Automotive Laboratory Development: Small Engine Dynamometer System Design

Preliminary Design Report

Team 04006 Benjamin Duprey Matthew Lazzaro

Timothy Trapp David Wuchter Aron Youngs

2/20/04

Department of Mechanical Engineering Kate Gleason College of Engineering

Rochester Institute of Technology 76 Lomb Memorial Drive

Rochester, NY 14623-5604

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1. Executive Summary

This preliminary design report summarizes the progress achieved by the Automotive Laboratory Development Senior Design Team. Currently the Department of Mechanical Engineering at Rochester Institute of Technology utilizes a DYNO-mite dynamometer made by Land and Sea, Inc. The goal of the team is to design, manufacture, and test a replacement dynamometer system. With an impending expansion of the Kate Gleason College of Engineering a need arises for multiple dynamometer systems to be used in a yet-to-be-built automotive laboratory. It is not cost effective to procure the numerous dynamometer systems for both financial and educational reasons. The team must design a pilot production system that specifically fulfills all requirements of students and staff at RIT. This engine test fixture will ultimately be reproduced and modeled from the pilot production model and according to the plans and specifications of the design team.

The Engineering Design PlannerTM methodology was used to shape the design process of the dynamometer system. At the completion of the RIT 20032 Winter term the first five facets of this design process have been completed. The first step of the project was to recognize and quantify the need. This goal will push the project in the correct direction and set the scope, goals, and motivations of the design. The second step provides an overview of the concept development stemming from the needs assessment. This document discusses the various dynamometer devices and subsystems generated by the team. The third step provides a feasibility study of the proposed concepts. A formal process was used to quantify between the concepts and determine the best possible design system. The next step lay out the specific intentions of the design team final concept. All goals, design practices, and safety requirements are determined and recorded. The fifth step is the analysis of the chosen design. This section quantifies and qualifies the reasoning for design decisions and specifications, while also providing justifiable calculations and information. The final section of this document recognizes the status of the project after the design phase. A future plan and schedule is created to keep the team on target for a successful pilot production dynamometer design. The current drawing package, budget, and bill of materials of the project are included in a technical data package.

Utilizing the Engineering Design PlannerTM the dynamometer system advanced. The final design became an open loop water brake absorber system. The water brake acts as a very inefficient pump absorbing the energy produced by an engine. A casing houses the impeller type water brake. The impeller is directly connected to the driveshaft of the test engine. As engine speed increases the water brake rotates. Load is applied by controlling the amount of fluid allowing into the casing surround the water brake. The impeller design absorbs the kinetic energy and creates an output flow from the casing. The dynamometer system uses an array of sensors to accurately measure the characteristics of the test engine. A data acquisition system records and analyzes the sensor outputs. When fabricated, the system will be capable of absorbing the full 5 horsepower produced by the specified Kohler test engine.

Experimentation will be conducted prior to the completion of the pilot production system to validate the dynamometer meets design objectives and specifications.

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1. Table of Contents 1. Executive Summary.................................................................................................2 1. Table of Contents ....................................................................................................3 2. Needs Assessment ...................................................................................................5

2.1. Project Mission Statement................................................................................5 2.2. Product Description .........................................................................................5 2.3. Scope Limitations ............................................................................................8 2.4. Stake Holders...................................................................................................9 2.5. Key Business Goals .........................................................................................9 2.6. Top Level Critical Financial Parameters.........................................................10 2.7. Financial Analysis..........................................................................................10 2.8. Primary Market ..............................................................................................11 2.9. Secondary Market ..........................................................................................11 2.10. Order Qualifiers .........................................................................................11 2.11. Order Winners............................................................................................12 2.12. Innovation Opportunities............................................................................12 2.13. Background................................................................................................13

3. Concept Development............................................................................................16 3.1. Water Braking System Concept......................................................................17 3.2. Resistance Load Generator System Concept...................................................18 3.3. Mechanical Brake System Concept ................................................................19 3.4. Sensor Package ..............................................................................................19 3.5. Data Acquisition Package ..............................................................................21

4. Feasibility Assessment...........................................................................................23 4.1. Water Brake System Feasibility .....................................................................24

4.1.1. Closed Loop...........................................................................................24 4.1.2. Open Loop .............................................................................................25

4.2. Resistance Load Electric Generator System Feasibility ..................................25 4.3. Mechanical Brake System Feasibility.............................................................27 4.4. Feasibility Conclusion....................................................................................28

5. Performance Objectives and Specifications............................................................29 5.1. Design Objectives ..........................................................................................29 5.2. Performance Objectives .................................................................................30 5.3. Design Practices Used by the Team................................................................31 5.4. Safety Objectives ...........................................................................................32

6. Analysis of the Problem and Synthesis of Design ..................................................33 6.1. Water Brake Impeller Design.........................................................................34

6.1.1. Water Brake Impeller Radius .................................................................35 6.1.2. Water Brake Inertia Optimization...........................................................38 6.1.3. Profile of Impeller Blades.......................................................................40 6.1.4. Water Brake Impeller Design Conclusion...............................................45

6.2. Water Brake Casing Design ...............................................................................45 6.3. Torque Arm Design ...........................................................................................49 6.4. Motor Mounting Design and Setup ....................................................................50 6.5. Sensor Placement and Mounting ........................................................................53

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6.6. Data Acquisition Design and Setup....................................................................55 6.7. Controls and User-Interface Design ...................................................................57 6.8. Structure and Assembly .....................................................................................58 7. Budget ...................................................................................................................60 8. Future Plans...........................................................................................................61 8.1. Schedule ............................................................................................................63 9. Conclusion ............................................................................................................63 10. References .........................................................................................................65 11. Appendix ...........................................................................................................66

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2. Needs Assessment

2.1. Project Mission Statement

The Automotive Lab Development Senior Design Team is to design and fabricate

a working pilot production system. The final design will provide a flexible bench top,

educational engine test fixture. The design must incorporate hands on experience to

further enhance theory from coursework. The solution must be safe, robust, flexible to

change, and intuitive to operate.

2.2. Product Description

Figure 2.2.1 � Kohler Engine

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Currently at Rochester Institute of Technology, a single small engine dynamometer is

utilized in labs and coursework. With the impending expansion of the Kate Gleason

College of Engineering building, there are plans to build a new automotive test cell

facility. This state of the art laboratory will be a dramatic improvement over the current

situation. Students have only had one small engine dynamometer available for use. Even

with small laboratory groups the learning experience from using the dynamometer was

minimized. RIT has proposed to incorporate six new small engine dynamometers into

the new automotive laboratory. This equipment will be the main components of the lab.

The current dynamometer was procured from Land and Sea, Inc. The Land and

Sea DYNO-mite is not being used to its full potential. This system is not properly

matched to its end use at RIT, learning. The DNYO-mite is capable of conducting its

own dyno runs with minimal operator interface. The system includes servo-motion

control of throttle and load, along with a stand alone data acquisition system and

computer; it is a �black box� system.

To simply purchase more units from Land and Sea is not the best direction for

RIT to pursue. The cost of each unit is on the order of $30,000, while the value to the

institution and students is far less. The DYNO-mite unit has many advanced features that

are irrelevant to learning and unused. The unique data acquisition system does not allow

standardization. Maintenance and repair must be done by Land and Sea technicians.

Replacement parts are not common and therefore must be routed from Land and Sea as

well.

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In order to fully meet the needs of the College of Engineering and the future

Automotive Laboratory, the only viable solution is to design and build an original

dynamometer. The new system will be tailor-fitted to meet the specific needs of students

and professors at RIT.

The new dynamometer will designed around a stockpile of small single cylinder

engines currently owned by RIT. The College of Engineering has a large quantity of

Kohler Command engines. This five horsepower, single cylinder, air cooled, four stroke

power plant is robust and reliable.

The purpose of a dynamometer is to place a load on an engine and measure its

performance. The application of the mechanical load creates energy. The fundamental

goal of a dynamometer is conversion or translation of energy. The Kohler engine creates

five horsepower therefore the design must be able to dissipate at a minimum of five

horsepower in order to completely stall the engine. There are a variety of designs and

systems for dynamometers. The final design will best fit the needs of students and

professors.

The goal of the design group is to produce a single unit. The ultimate intention of

the College of Engineering is to reproduce this pilot production model. Depending on

budget and space requirements six to ten dynamometer units will be reproduced. The

Kate Gleason College of Engineering expansion building plans for the automotive

laboratory will take into consideration the new dynamometer design.

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2.3. Scope Limitations

The pilot production Automotive Laboratory Small Engine Dynamometer shall be

fully designed by the end of RIT�s winter quarter and be fabricated and fully assembled

at the completion of spring quarter.

At the end of Winter Quarter 20032, the senior design team will hold a Preliminary

Design Review. At this time the group will be responsible for:

• Needs Assessment

• Concept Development

• Feasibility Assessment

• Drawing Package

• Analysis and justification of final design

• Bill of Materials

• Budget

At the end of Spring Quarter 20033, the senior design team will present the working pilot

production system. The end responsibilities will include:

• Functioning pilot production dynamometer system

• Operating and Training Manual

• Final Report and Binder

The senior design team will not be responsible for the following:

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• Performance modifications to the Kohler engine

• Design of laboratory building and structure

• Generating laboratory experiments

2.4. Stake Holders

The key stake holders are the students and professors using the future Automotive

Laboratory. Other stake holders include the students of the senior design team and their

future employers.

2.5. Key Business Goals

The senior design team will be successful when it has designed and fabricated a

pilot production small engine dynamometer that meets the academic and research needs

of the RIT College of Engineering students and staff. If this has been done then:

• The members of the team will have learned how to work on an engineering team

in a professional manner.

• RIT will have a pilot production model of a new small engine dynamometer

specifically suited to the needs of the College of Engineering.

• The design package will be able to be replicated and reproduced depending on the

requirements and demands of students and the institute.

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2.6. Top Level Critical Financial Parameters

• The dynamometer must be cheaper than the current Land and Sea DNYO-mite

dynamometer.

• The dynamometer system must be easily reproduced. Common parts, simple

machining, and RIT standards will be used to minimize cost of cloning the design.

• Human interface of dynamometer design must provide an intuitive educational

experience.

• Data and analysis must be accurately conveyed.

2.7. Financial Analysis

A $5000 budget has been proposed for the RIT Automotive Lab Development

Senior Design team. This budget shall include:

• Mechanical components of dynamometer

• Coupling for connecting Kohler engine to dynamometer

• Data acquisition equipment and software

• Sensor package

• Mounting platform or cart

• Raw materials for machining mounts and mechanical control system

• Computer system to run DAQ software and provide user interface

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2.8. Primary Market

The primary market of the new small engine dynamometer system is the College

of Engineering. This consists of both students and professors primarily in the Mechanical

Engineering department.

2.9. Secondary Market

The secondary market includes the commercialization of the use of the new

automotive laboratory. Potentially RIT could create a program in which it sells dyno

time to businesses and individuals wishing to test small engines. Also RIT could sell or

distribute the design specifications to other colleges and institutions as a learning tool.

2.10. Order Qualifiers

The Automotive Laboratory Development team will create a pilot production

small engine test fixture. The design will meet the needs of the College of Engineering.

The design will also incorporate future reproduction plans of the system. Upon

completion a user-guide and training manual will document operation of the system for

future users and maintenance issues.

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2.11. Order Winners

• The new design will be cheaper than the existing dynamometer currently in use.

• Comply with OSHA safety standards.

• Ease of operation for students with minimal assistance from instructor.

• A compact portable design to efficiently utilize laboratory space.

• System will verify experimental data collected conforms to theoretical

calculations.

• Maintenance issues will be minimized with widespread use of common parts.

• System will be designed with ease of reproducibility in mind.

2.12. Innovation Opportunities

The new design of the small engine test fixture has the potential to be marketed

by RIT to other colleges, learning institutions, and private industries. The dynamometer

and incumbent system will be focused on learning rather than just collecting raw data.

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2.13. Background

Figure 2.13.1 � DynoMite Dynamometer

A dynamometer can be defined as any device for measuring power output of a source.

More specifically it is a device for measuring the tangential forces incident to a rotating

mass. In terms of engine and automotive interests a dynamometer is a way of accurately

measuring the specific output of an engine. Dynamometers typically apply some form of

measurable resistance on the engine. The resistance is called the load, and serves as a

benchmark, something to measure the engine�s power against. There are a variety of

ways to measure this output, and these are dictated by the basic mechanism of the

dynamometer design.

The most common form of dynamometers today, use oil or water circulating with

a pump to provide the load requirement. This system works on a simple concept: the

harder the pump and fluid work the harder the engine must work. Increasing the flow of

the fluid to the point the engine cannot output enough power, will cause the engine to

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slow down. Likewise, reducing the flow of the fluid will cause the engine to speed up

until equilibrium is reached. Utilizing a valve to regulate inlet fluid flow allows control

of the applied load. There are two variations of this design.

The first design calls for a pump to be driven by the output of the measured

engine. Using a positive displacement pump mechanically forces the fluid out of the

pump outlet. This mechanism allows load to be applied to the engine by regulating, with

a valve, the inlet amount of fluid to the pump. Measuring the power of the engine is then

directly related to the fluid flow exiting the pump. The pump converts the test engines

power into a fluid flow.

Water brakes are another form of hydraulic pump absorbers. These designs

consist of one or more vaned rotors spinning in between pocketed stator housings. Load

is controlled by adjusting the level of fluid in the brake with adjustable inlet orifice.

Raising the fluid level increases the rotational drag of the rotor, applying more resistance

to the engine turning it. The water brake is easily compared to a very inefficient pump; it

efficiently uses up engine power by converting it to fluid flow and heat.

The simplest and earliest form of dynamometer brakes were mechanical brakes.

A rotating drum with a friction brake was used to apply drag at the engine�s output shaft.

This crude form of absorber proved difficult to accurately apply a consistent load for

prolonged periods of time. Mechanical brakes convert kinetic energy into thermal energy

by using pressure to apply varying levels of friction. The heat lost to surrounds is

difficult to measure further enhancing characteristic drawbacks of these simple systems.

Electric dynamometers convert mechanical power to electric power. The engine

drives a generator. The more electricity generated, the harder the engine has to work.

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The voltage created by a generator is more or less constant. Therefore, by varying the

amount of electrical current load on the generator, the mechanical load on the engine is

varied. Varying the load can be accomplished by adding resistance to the electric output

of the generator.

Generator style dynamometers are great for steady state conditions, but have

significant drawbacks for transient testing. Generators have a high polar moment of

inertia. High inertia means a lot of power is required to accelerate the armature.

Likewise, a lot of stored horsepower will be returned when dropping down in engine

speed. This effect skews the test data whenever engine speed is changing.

Eddy current brake dynamometers are similar in operational characteristics to

electric generator absorbers. The main difference is that eddy current brakes do not

generate electricity. Rather, they use an electrical power supply to charge

electromagnetic coils. The dynamometer�s input shaft spins a metallic rotor inside the

resulting magnetic field. When the current to the magnetic field is increased, the rotor

shaft becomes harder for the test engine to turn.

Regardless of the dynamometer device in use, a method to gathering information

must be in place. The most basic piece of information from a dynamometer is torque.

Knowing the torque of the driveshaft and measuring the engine speed, output power can

then be determined. Besides the output of the engine other vital measurements include

pressure in the combustion chamber, intake temperature, and exhaust temperature. With

these basic measurements the thermodynamic cycles of the internal combustion engine

can be compared against theory. The key element of any dynamometer system is

accurately measuring the type of loads and conditions you are trying to simulate.

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3. Concept Development

The Automotive Laboratory Development Senior Design Group developed a large

list of possible solutions to satisfy the need of producing an inexpensive dynamometer as

a teaching tool. The list was generated from numerous brainstorming sessions and based

on initial feasibility assessments focused on three schools of thought. The concepts

developed for the dynamometer design stemmed from a fluid braking system, a

mechanical braking system and an electrical braking system. These 3 basic designs were

then expanded upon and more closely evaluated.

Group and individual drawings were initially generated to develop more formal

plans. The group drawings generated five concepts and individually, each member was

assigned to generate three concept drawings. There was a great deal of overlap and from

23 concepts there ended up being nine individual proposals. These nine concepts were: an

inertial dynamometer system, an open system water brake, a resistance load electrical

generator brake, a mechanical brake, an eddy current brake, a competing engine brake, a

load cell electric generator brake, and a closed system water brake. A second feasibility

assessment was conducted to eliminate the competing engine brake, the load cell electric

generator brake and the eddy current brake. After this elimination a great deal of debate

occurred over the feasibility of each of the three semi-final designs. Each of these

concepts is presented in detail below.

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3.1. Water Braking System Concept

The water braking system concept is largely based upon centrifugal pumping

laws. A centrifugal pump works on the concept of displacing fluid radially from its inlet

to its outlet, about the impeller of the pump. The load a centrifugal pump encounters is

related to the input power and the input flow. The less the input power and the larger the

flow the easier it is to stall, or brake, the pump.

The same theory applies for a water brake dynamometer system. A water brake

dynamometer is directly connected to the engine output shaft. The pump impeller and

the power of the engine produce dictate the pumping ability and thus output of the

system. Varying the inlet water flow through a valve can control the amount of load

placed on the engine.

A closed system water brake incorporates a pump and reservoir to drive the fluid

into the absorber. This creates a large packaging sized dynamometer. By using the closed

system approach, more heat is generated due to the use of a common water supply and a

pump. Due to this generation of heat, a cooling system would need to be implemented to

allow the system parameters to remain constant and efficient. However, because the

system is closed, measuring the pumping losses due to heat generation is straightforward.

Despite the varying temperature a closed system water brake is more environmentally

friendly in its handling of water and potentially various working fluids could be used.

An open system water brake dynamometer uses tap water as the inlet flow and has

no re-circulation; allowing for a small unit packaging size. By using an open system

approach, heat is generation in negligible; a cooling system is unnecessary. However,

since the system relies on tap water, the flow may not to be constant. This effect is

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directly related to the plumbing facilities and configurations the system is connected to.

The lack of a reservoir and pump will allow measuring heat loss slightly harder than that

of a closed system.

3.2. Resistance Load Generator System Concept

The resistance load generator system concept is based on constant voltage laws

that dictate that a system will absorb a designated current based on its level of resistance.

The system design calls for an AC electric generator to be attached to the output shaft of

the engine and a bank of switch-selected resistors to be wired in series to the generator

power output line. By selecting specific resistors, which correspond to a certain level of

current absorption, the load can be varied on the basis that power is the product of

voltage and current.

Another resistance loaded dynamometer concept can utilize switch-selected light

bulbs, LEDs or heating coils. This would provide a visual representation of the

impending load to the user.

Despite the simplicity of an electric generator style dynamometer there exists a

great deal of inefficiencies in converting mechanical power into electrical power.

Similarly, because the resistance loads required have to absorb high levels of power, thus

generating heat, the inherent electrical inefficiencies of the resistors skyrocket unless

cooling systems are integrated.

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3.3. Mechanical Brake System Concept

The mechanical brake system concept is based upon transferring mechanical

energy into thermal energy or heat. This is accomplished through the torque generated

from friction about a designated rotating radius. Exactly like an automotive disc brake,

the system turns input hydraulic pressure into a normal force that is applied to a friction

pad, and is then applied to a surface that radiates heat. Applying a disc brake system to an

engine�s output shaft gets the same response. By varying the hydraulic pressure, many

different loads can be achieved.

Despite the simplicity of a mechanical dynamometer system there exists a great

deal of data acquisition problems associated with the heat transfer through the brake

system. To measure this thermal energy loss, very sophisticated sensors would be

necessary to determine the heat transferred to the surrounding environment.

3.4. Sensor Package

The main objective of building the dynamometer system is to place a load on the

engine. The above mentioned concepts all deal with the placement of the load, whether

mechanical or electrical, on the engine itself. The most important and integral part of the

dynamometer is the sensor package.

The sensor design is independent, or generic, to the dynamometer concept used.

The sensor package is to be designed according to the needs assessment. The educational

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purpose of the dynamometer system is to relate experimentally, how the internal

combustion Kohler engine operates, and compare those attributes to theory learned in the

classroom.

This goal can be achieved by measuring a fundamental set of data points. Intake

temperature and exhaust temperature will be used with cylinder pressure to model the

thermodynamic cycle in the engine cylinder. A thermocouple placed in the intake

manifold, before the combustion chamber will record an average intake temperature. A

thermocouple place in the exhaust flow will determine the average temperature of the

gasses exiting the after the combustion cycle. A pressure transducer mounted in the

cylinder head of the engine will record the dynamic pressure throughout the

thermodynamic process. A second pressure transducer will be used to measure intake

pressure.

A mass air flow sensor used in conjunction with an oxygen sensor will be used to

calculate the amount of fuel flowing into the engine. A wide-band oxygen sensor uses a

chemical reaction to output a voltage that is related to the air and fuel mixture in the

exhaust. The output voltages of the sensor can be measured and can be related to

corresponding air-fuel ratios. The mass air flow sensor measures the amount of flow into

the engine. Using the flow rate and the air-fuel ratio the amount of fuel is equal to:

Flow Rate of Air / Air-Fuel Ratio = Flow Rate of Fuel

To relate emissions to the laboratory a hydrocarbon measuring device will be

placed in the exhaust flow. This device measures the average concentration of

hydrocarbons. This reading can be used to relate emissions to engine speed and load.

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The sensor needs to be mounted somewhere in the exhaust flow path and outputs a

voltage that corresponds to specific hydrocarbon concentrations.

Engine speed will be measured using a Hall-Effect sensor. This sensor is used in

conjunction with one or more small magnets. As the magnets pass by the sensor a

voltage is output. The magnets can be mounted on the driveshaft, as the driveshaft turns

the sensor will measure the engine speed. Using the data acquisition system to read the

amount of voltages output from the sensor over a given period of time the engine

revolutions per minute can be recorded and displayed.

The load applied from the dynamometer is dependant on the style of system used

in the final design. A mechanical of fluid style dynamometer will use a torque arm to

measure the rotational force, torque. A strain gauge mounted on the torque arm converts

the mechanical load into a measurable voltage.

An electric generator style dynamometer will measure the load on the engine in

terms of power. An ammeter style device can measure the current produced by the

generator. Power is equal to the product of current and voltage, and therefore can be

calculated and recorded.

3.5. Data Acquisition Package The data acquisition, DAQ, subsystem is independent of concept choice. The

DAQ equipment will interpret the readings taken from the sensors and relate them to data

and measurements understandable by the users. The output of each sensor is either a

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current or voltage. The DAQ is programmed for each sensor to read the electrical output

and display or record various measurements.

According to the Kate Gleason College of Engineering National Instruments

equipment and LabVIEW Software will be used. This software is the industry standard

for data collection.

The constraining requirement of the DAQ is the sampling rate for the in-cylinder

pressure transducer. Due to the nature of the Kohler engine, and engine speed, the DAQ

system and pressure sensor must accurately record in-cylinder pressure at speeds up to

6000rpm. This requires a sampling rate of 100 samples per second.

Intake and exhaust temperatures do not require a high sampling rate. These

properties change gradually over time depending on atmospheric and loading conditions.

The engine speed will be read by the DAQ as an input voltage. Within the

software a scale factor will be programmed with a timer to display and record engine

revolutions per minute.

The load placed on the engine by the dynamometer will be output through the

strain gauge. LabVIEW will be programmed to interpret this voltage or current and

display and record a value for torque. Using the formula:

dEngineSpeeTorquePower *=

LabVIEW can be programmed to calculate the power produced by the Kohler engine as

well.

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4. Feasibility Assessment

The three basic concepts presented in the previous section are the results of team and

personal brainstorming involving initial investigation and evaluation. Once each potential

concept had been clearly defined and understood by all members of the team a feasibility

assessment was generated using the steps provided in the Design Planner package. This

assessment looked at technical, performance, schedule, economic, and resource factors

affecting the completion of the project. Each question was compared with the project

baseline, which is the current dynamometer described in the section 1, Needs

Assessment. These questions were graded on a scale of 0 to 3, with a score of 2

representing the same as the base line, 0 being not feasible, 1 being less feasible and 3

being more feasible. The team used these factors to rank the concepts and decide which

direction the team and the design project should move in. The feasibility of each concept

is described below.

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4.1. Water Brake System Feasibility

4.1.1. Closed Loop

The closed loop water brake dynamometer was compared to a baseline of the

current dynamometer, an open loop water brake. The 13 questions were broken into

subgroups and discussed as shown.

First, an assessment was done regarding resource feasibility. The team has

sufficient skills, sufficient equipment and enough people to satisfy the goal of the project.

The resource feasibility assessment received a score equal to that of the baseline.

Second, an assessment was done regarding economic feasibility. The team�s

budget would be enough to support this concept. However, if it were to fail, due to the

necessity of purchasing pumping equipment the left over budget may not be enough to

�start over�. The economic assessment received a score slightly below the baseline.

Third, an assessment was done with regard to schedule feasibility. The chances

of meeting intermediate mileposts, PDR and CDR requirements are very close to that of

the baseline. By adding the necessary parts to produce a closed loop system some level of

intricacy is added to the design. Due to these intricacies, the schedule assessment

received a score slightly less than the baseline.

Fourth, a feasibility assessment related to the technical aspect of the closed loop

was conducted. The senior design team has the basic skills necessary to implement a

closed loop system. However, the team may require assistance in designing an

appropriate cooling system for the water. Similarly, the data acquisition and tuning

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associated with the heat transfer issues could potentially require assistance. The technical

assessment received a score slightly below the baseline.

Lastly, an assessment was done regarding performance aspects. Having a closed

loop system certainly satisfies the needs assessment. It achieves the same result as the

baseline in producing a useful teaching tool. However, it is less wasteful with water and

easier to establish efficiently losses due to thermal energy losses. The performance

assessment received a score slightly higher than the baseline.

4.1.2. Open Loop

The open loop water brake has the same characteristics as the baseline. Therefore

it has the same score in the feasibility assessment.

4.2. Resistance Load Electric Generator System Feasibility

The resistance load electric generator dynamometer was compared to a baseline

of the current dynamometer, an open loop water brake. The 12 questions were broken

into subgroups and discussed as shown.

First, an assessment was done regarding resource feasibility. The team has

sufficient skills, sufficient equipment and enough people to satisfy the goal of the project.

However, the team has no electrical engineers; therefore consulting RIT�s staff could be

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necessary. The resource feasibility assessment received a score slightly less than that of

the baseline.

Second, an assessment was done regarding economic feasibility. The team�s

budget would be enough to support this concept. However, if it were to fail, due to the

necessity of purchasing an electric generator, numerous resistors and switches the left

over budget may not be enough to �start over�. The economic assessment received a

score slightly below the baseline.

Third, an assessment was done with regard to schedule feasibility. The chances of

meeting intermediate mileposts, PDR and CDR requirements are not so close to that of

the baseline. The intricacies inherent in having many switch selected high power resistors

and the potential need for a cooling system could generate trouble for post production

testing. Due to these intricacies, the schedule assessment received a score less than the

baseline.

Fourth, a feasibility assessment related to the technical aspect of the electrical

dynamometer was conducted. The senior design team has the basic skills necessary to

implement an electrical dynamometer system. However, the team may require assistance

in designing an appropriate cooling system for the resistors. Similarly, the data

acquisition and tuning associated with the heat transfer issues could potentially require

assistance. The technical assessment received a score slightly below the baseline.

Lastly, an assessment was done regarding performance aspects. Having an

electrical dynamometer system certainly satisfies the needs assessment. It achieves the

same result as the baseline in producing a useful teaching tool. However, it is less

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efficient due to converting mechanical energy to electrical energy. The performance

assessment received a score slightly lower than the baseline.

4.3. Mechanical Brake System Feasibility

The mechanical brake dynamometer was compared to a baseline of the current

dynamometer, an open loop water brake. The 12 questions were broken into subgroups

and discussed as shown.

First, an assessment was done regarding resource feasibility. The team has

sufficient skills, sufficient equipment and enough people to satisfy the goal of the project.

The resource feasibility assessment received a score equal to that of the baseline.

Second, an assessment was done regarding economic feasibility. The team�s

budget would be enough to support this concept. However, even if it were to fail, despite

the necessary purchasing of sophisticated sensors the left over budget would likely be

enough to �start over�. The economic assessment received a score equal to the baseline.

Third, an assessment was done with regard to schedule feasibility. The chances

of meeting intermediate mileposts, PDR and CDR requirements are very close to that of

the baseline. By adding the necessary sensors to produce a mechanical system and

subtracting the water pumping and sensing system it is likely to be similar to the baseline.

Therefore the schedule assessment received a score equal to the baseline.

Fourth, a feasibility assessment related to the technical aspect of the mechanical

brake was conducted. The senior design team has the basic skills necessary to implement

a mechanical system. However, the team may require assistance in the data acquisition

28

and tuning associated with the heat transfer issues. The technical assessment received a

score slightly below the baseline.

Lastly, an assessment was done regarding performance aspects. Having a

mechanical system certainly satisfies the needs assessment. It achieves the same result as

the baseline in producing a useful teaching tool. However, it isn�t wasteful but is likely

harder to establish thermal energy losses. The performance assessment received a score

equal to the baseline.

4.4. Feasibility Conclusion

Based on the analysis presented above, the team was able to examine each

concept and decide which concept should be further developed. The scores of each

concept and a radar chart can be seen in Appendix B. The team decided to select the

baseline, the open loop water brake dynamometer as it had the highest feasibility grade.

However, depending upon a more formal economic and technical assessment we may

integrate a closed loop system into the design.

R1 R2 E1 E2 S1 S2 S3 T1 T2 P1 P2Base Line: Water Brake Open Loop 2 2 2 2 2 2 2 2 2 2 2Water Brake Closed Loop 2 2 2 1 1 2 2 1 2 2 3Electro Generator 1 2 2 1 1 2 2 1 1 1 1Mechanical Brake 2 2 3 2 2 2 2 2 1 2 1

Feasibility Assessment

0

1

2

3R1

R2

E1

E2

S1

S2S3

T1

T2

P1

P2

P3

Base Line: Water BrakeOpen LoopWater Brake Closed Loop

Electro Generator

Mechanical Brake

29

Figure 4.4.1

5. Performance Objectives and Specifications

The team acknowledges that certain objectives and specifications have to be

determined so that it can measure the performance of the engine dynamometer system.

These objectives and specifications are discussed in this section.

5.1. Design Objectives There are a number of design objectives that required the attention of the team.

These objectives need to be specified in order for the team to have a set list of goals to

achieve. These objectives are listed below.

1) The most important goal that the team has to achieve is the production of a

functional engine dynamometer. This goal lies at the core of the project and the

design elements must include this objective at every phase.

2) Another objective is to design the engine dynamometer as a functional teaching

tool. This goal is central to the objectives illustrated in the needs assessment.

3) Another objective that has been incorporated into the design of the engine

dynamometer is accuracy. The acquisition of data must provide a high level of

accuracy for the engine dynamometer to be a functional lab tool.

30

4) The team will also ensure that the engine dynamometer is safe, reliable and

robust. This objective is essential to the uptime of the engine laboratory and

therefore essential for the dynamometer as a teaching tool.

5.2. Performance Objectives

The team has decided that a number of performance specifications need to be met

in order for the project to be successful. These specifications are based on the minimal

requirements of the engine dynamometer to be designed by the team. Therefore the final

product needs to be able to meet these minimal requirements so that the basic objectives

of the project are fulfilled. These specifications have been kept in mind when designing

the engine dynamometer and are listed below.

1) The engine dynamometer shall be able to absorb at least 3.7 kilowatts of power.

An important objective that has been incorporated into the design of the engine

dynamometer is for the dynamometer to be able to stall the engine. This is

essential for the performance of a lab and thus is critical to having the

dynamometer as a teaching tool.

2) The sensor package must be accurate and robust. The sensors must be able to

handle a large range of operating parameters. For example, the in cylinder

pressure transducer must be able to withstand 10,061 kilopascals. The exhaust

thermocouple must be able to withstand 1,500 degrees Celsius. The mass airflow

sensor must be able to withstand 11.44 cubic feet per minute. The sensors also

must be able to come close to continuous sampling i.e. have/handle high

frequencies and high resolutions.

31

3) The team will also ensure that the engine vibration does not interfere with the data

acquisition and that the torque arm be optimally designed so as to handle 8.4 ft-

lbs of torque.

4) The engine dynamometer will have minimal inertia. We are not designing an

inertial dynamometer; therefore any non-liquid additional inertia is not necessary

and would be intrusive upon our overall accuracy.

5.3. Design Practices Used by the Team

The team discussed a number of design practices to be considered when designing the

engine dynamometer. These practices are provided below.

1) Design for Manufacturability � The team has designed the engine dynamometer

such that the parts are designed custom for this application, however they can be

easily reproduced.

2) Design for Assembly � The team designed the engine dynamometer such that a

few assemblies and sub-assemblies exist in order to make the entire assembly

process easier.

3) Design for Minimal Cost � The team designed the engine dynamometer such that

the cost of making the dynamometer is kept to a minimum. Unnecessary parts and

materials were kept to a minimum and the materials were selected after assessing

benefits versus costs.

32

4) Design for Reliability � The team has selected materials and parts that will make

the engine dynamometer as reliable as possible.

5.4. Safety Objectives

The team found set safety standards for this project�s handling of combustible

fluids and exhaust. Also, the nature of an engine and an engine dynamometer require

guidelines related to fast moving parts.

• The most important safety issue of an indoor engine dynamometer is related to the

handling of combustible fluids. An engine requires fuel to run, and in our case

that fuel is gasoline. ASME requires gasoline to be contained in a certain fashion.

The engine we are using for the engine dynamometer has an ASME certified gas

tank.

• The second most important safety issue of an indoor engine dynamometer is

related to the handling of exhaust emissions. OSHA requires exhaust emissions to

be ventilated from all indoor rooms to the outside. A vacuum ventilation system is

going to be central to the operation of the engine dynamometer indoors. The

engine lab cell is going to have this type of system when the building is

completed.

• Thirdly, the nature of mechanical systems with fast moving parts requires all

exposed moving parts to be guarded for operator safety.

33

6. Analysis of the Problem and Synthesis of Design

The analysis of the open loop water brake dynamometer system focused on

several different aspects of the overall design. The system design was split up into the

component sections: water brake impeller, water brake casing, torque arm, motor

mounting, sensor placement, data acquisition, controls and user-interface, and structure

and assembly.

The water brake was designed to provide sufficient load to stall the Kohler engine

as well as be flexible for use with other small engines that may be used in the future. The

impeller blade angle and surface area were modeled and optimized to provide the most

favorable results best suited for the team�s design requirements. Machine-ability and

remanufacture-ability were also major criteria when specifying the water brake impeller

geometry.

The water brake casing was designed around the impeller. The casing was

designed to withstand worst-case scenario operating conditions. A Finite Element

Analysis, FEA, was conducted on the casing for proof of concept data.

The torque arm was designed and optimized to translate the most accurate toque

reading to the DAQ system. Strength of materials calculations were used to determine

size and shape of the arm. Placement of the strain gauge was also chosen to best suit the

needs of the system and equipment.

The motor mounting hardware was designed and specified to effectively isolate

the inherent vibration cause by the engine. Without this feature an undesirable amount of

34

electrical noise would be created. This effect would interfere with sensor and DAQ

equipment, rendering the system inaccurate if not useless.

The data acquisition equipment was specified to meet the requirements of the

needs assessment. The equipment did not need to be designed, rather procured. The

DAQ software, LabVIEW, will be programmed next quarter, as part of the build-phase.

The controls and user-interface were designed to be intuitive and straightforward.

An engine speed control and variable load control must be incorporated into the final

system. They must be able to handle the use and abuse associated with student operated

laboratory equipment. The user-interface design includes both the LabVIEW display on

the system computer monitor as well as a visual tachometer and flow-meter.

A pre-fabricated industrial cart will be used as the backbone of the structure. The

system will be packaged to fit entirely on the cart.

6.1. Water Brake Impeller Design

The impeller is made of two separate pieces: the actual impeller, which is

machined out of 6061 aluminum, and the collar the impeller and the case rests on, which

is made out of steel. The design has two focus points: the radius of the impeller, and the

profile of the impeller blades. The radius of the design constrains the maximum power

the impeller can dissipate. The profile design determines the efficiency of the impeller.

35

6.1.1. Water Brake Impeller Radius

The design team needed to determine the optimized radius for the water brake

according to the needs assessment requirements. Using the following equation (Equation

6.1.1) the water brake can be designed to fit desired parameters.

QRTshaft ρω 22= Equation 6.1.1

In this equation, T shaft is the torque on the motor shaft; ω is the angular velocity of

the impeller; R2 is the radius of the impeller; ρ is the density of the fluid; and Q is the

mass flow rate of the fluid. By varying R2, different values for T shaft could be calculated

and used Equation 6.1.2:

shaftm TW ϖ=.

Equation 6.1.2

T shaft is the torque on the motor shaft; ω is the angular velocity of the impeller;

and Wm is the work done by the motor on the impeller. Optimizing the size of the

impeller, R2, was done for the given power rating of the Kohler engine, five horsepower.

The minimum radius requirement of the impeller design calls for a 2.75� radius in order

to completely absorb the engine output.

One requirement of the needs assessment addresses a flexible system. The water

brake impeller design justifies that size and character of the engine being loaded.

Increasing the impeller radius allows for seamless integration with the Kohler engine as

well as higher output power plants. Figure 6.1.1 shows the maximum power various size

impellers can absorb at 3600rpm. The Kohler Command engine produces maximum

output at 3600rpm.

36

Power vs. Impeller Diameter: Engine Speed 3600rpm

0

10

20

30

40

50

60

70

0 1 2 3 4 5 6 7 8

R2 (inches)

Wm

(HP)

Figure 6.1.1

The team decided on an impeller design with a radius of 6�. This size will allow a

maximum of 45HP at 3600rpm. These characteristics will allow the system to remain

flexible without having any negative effects on lower output engines such as the Kohler

Command.

The water brake impeller is directly connected to the output shaft of the engine.

As engine speed increases the water brake can effectively absorb an increasing amount of

energy. Figure 6.1.2 displays that a 6� radius impeller design is capable of absorbing

126HP at an engine speed of 6000rpm.

37

Power vs. Impeller Diameter: Engine Speed 6000rpm

0

20

40

60

80

100

120

140

160

180

200

0 1 2 3 4 5 6 7 8

R2 (inches)

Wm

(HP)

Figure 6.1.2

Figure 6.1.3 � Final Impeller Model

38

6.1.2. Water Brake Inertia Optimization

Ideally, since the dynamometer is to be used with the low output Kohler engine

inertia should be minimized. Since this engine only produces an approximate maximum

power of 5 horsepower the percent error caused by a massive water brake would render

the system inaccurate.

The inertia of the water brake impeller was calculated using a straight-edged

blade design. Later in this document the justification of the blade design will be

explained. Using this assumption the inertia of the impeller can be determined by

breaking up the impeller design in two geometric matrixes, a disc and a series of

rectangles. The disk is used to model the back of the impeller, while the blades are

assumed to be rectangles.

The volume of the disc can be found by:

hRRVdisc *)(* 12 −Π= (Equation 6.1.3)

Where R2 is the outer radius of the impeller, R1 is the inner radius of the impeller, and h

is the thickness.

The volume of the blades can be calculated using:

( ) NRRTWVblade *** 212 −= (Equation 6.1.4)

Where W is the blade width, T is the blade thickness, and N corresponds to the number of

blades.

Using the volumes of the disc and blades the mass of the impeller was

determined. The using the 6061 Aluminum density property of 0.102 lb/in^3 the mass is

equal to the quotient of the density and the total volume.

39

Once the mass was know the inertia of the impeller was calculated using Equation

6.5:

( )212**

21 RRmassI −= (Equation 6.1.5)

Figure 6.1.3 shows the relationship between impeller size and its inertia.

Impeller Radius vs. Inertia

0.0020.0040.0060.0080.00

100.00120.00140.00160.00

3 4 5 6 7 8 9 10Outer Radius (in)

Iner

tia (l

b*in

^2)

Figure 6.1.3

Using an impeller design size of 6 inches has a moment of inertia of 9.06 lb*in^2.

Compared to a 10 inch impeller with a moment of inertia of 135.88 lb*in^2, the 6 inch

design minimizes inertia while retaining a versatile power absorbing range.

These assumptions and calculations in the inertia analysis of the water brake were

simply used to steer the team in the correct direction of the design. The actual inertia of

the water break was found using a ProEngineer tool box to be 4.677lb*in^2. The

assumption to model the blades as rectangles is the reason for the error between actual

and calculated. This error does not affect the choice of impeller size since the error is

linear for all designs.

40

6.1.3. Profile of Impeller Blades

Before looking at the equations it is helpful to see the velocity diagram in Figure

6.1.4:

In the figure Vrb2 is the velocity relative to the blade, V is the absolute resolved

velocity, and U is the runner speed which can be found by using the Equation 6.1.6:

ϖrU = Equation 6.1.6

In this equation r is the radius of the impeller, and ω is the angular velocity. This

velocity diagram shows two unknowns; therefore an initial guess must be made at one of

the variables and then re-substituted iteratively into the equation. Translating the Vrb2

vector along the U vector, geometric laws can be used to simulate results. By using an

initial guess of Vrb2, and the law of cosines the absolute velocity can be modeled.

U2 = r2ω Vrb2

β2

V2Figure 6.1.4

41

The profile of the impeller blades will effectively determine the efficiency the

impeller operates as a pump, displacing fluid of a given rate at a design characteristic

velocity. The velocity relative to the blades will be known as Vrb2. The size of the

passages will be called b. The blade profile will determine the average velocity of the

fluid at both the inlet and outlet of the water brake. By varying the angle and profile of

the impeller blade, β, the velocity relative to the blade varies as shown in Figure 6.1.5:

Blade angle vs Vrb2: at 3600rpm

0

20

40

60

80

100

120

140

160

30 30.5 31 31.5 32 32.5 33 33.5 34Vrb2 (ft/s)

β (ο )

Figure 6.1.5

Analyzing the graph in figure 6.1.5, the relation between blade angle and relative velocity

can be seen. An obtuse angle relative to the spinning impeller direction produces a far

42

slower velocity than an acute blade angle. This graph demonstrates the flow

characteristics that the team used as a basis for the design calculations and assumptions.

Figure 6.1.6 graphically represents the specific speed values associated with

various impeller blade designs.

(Figure 6.1.6)

The profile of the impeller blade affects the specific speed of the absorber. Due to

machining ability and reproduction concerns the simplest profile was chosen; a blade

angle of 90 degrees with a straight vane. The design team made this assumption knowing

that measures must be taken in order to compensate for not using the most efficient

design.

The specific speed is used in Equation 6.1.7:

34

21

111

=

scuNQH ω Equation 6.1.7

In this equation H represents head, ω is the angular velocity, Q is the mass flow

rate of the fluid, and Nscu is the specific speed of the impeller. By using 500 as the

specific speed a head value of 4.76 ft was determined.

43

Next the power of the fluid needed to be calculated. This energy was found using

Equation 6.1.8:

waterfluid gQHP ρ= Equation 6.1.8

In this equation Pfluid is the power of the fluid, g is the constant of gravity, Q is the

mass flow rate of the fluid, H is the head, and ρwater is the density of the fluid, which in

this case is water. The power of the fluid was calculated to be 0.00135 in units of

horsepower for the given specific speed. Figure 6.7 compares various specific speeds

associated with different impeller designs.

The efficiency of the impeller can be determined. This was calculated by using

Equation 6.1.9:

00100×=

mech

fluid

PP

η Equation 6.1.9

In this equation η is the efficiency, Pfluid is the power of the fluid, and Pmech is the power

of the engine supplied by the shaft.

44

Figure 6.1.7 compares various specific speeds associated with different impeller designs.

Impeller Efficiency at 3600rpm

0

0.005

0.01

0.015

0.02

0.025

0.03

0 500 1000 1500 2000 2500

Nscu

ηFigure 6.1.7

The graph clearly shows that the specific speed associated with a straight impeller blade

is the worst choice when compared to the 2000 specific speed associated with a Francis

vane style impeller. Continuing with the assumption previously mentioned, although the

blade geometry is not optimized, the size geometry is. If the team were to use a curved

profile the same results of power absorption could be achieved in a smaller package.

The water brake characteristic design is to become a very inefficient pump. The

purpose of the device is to absorb energy. This is the reason for such low efficiency. In a

dynamometer, the lower the efficiency of the water brake, the better the design.

45

6.1.4. Water Brake Impeller Design Conclusion

The final impeller design the team has a 6 inch outer diameter. The twelve vanes

on each side of the impeller are of a straight design. A single vane extends 0.515 inches

and measure 0.19 inches thick. After the calculations and data gathered from the analysis

the team is confident this design will exceed all expectations of performance. Figure 6.8

is a drawing of the final impeller design.

6.2. Water Brake Casing Design

The casing of the water brake must be manufactured out of a readily available,

inexpensive and easily machinable metal. From these criteria, 6061 aluminum was

chosen. The casing is easily manufactured using an engine lathe. Its purpose is to contain

the water and impeller during dynamometer operation. The bearings that the impeller run

on are installed into the casing as well are the shaft seals. In order to get water into and

out of the case, there are two fittings. One for the inlet which will accommodate a

common garden hose and the other for the outlet. A small vent hole is also added to help

the water brake drain after a power run. The radial bolt circle will seal the outer edge.

The casing of the water brake must remain stationary because it is how the torque is

transmitted from the impeller to the torque arm. In order to accommodate this, an adaptor

shaft was designed to allow the impeller to turn and the casing to remain stationary. The

shaft will be press fit into the impeller and bored to fit the output shaft on the engine.

Two countersunk holes will also be added to one end to accommodate magnets for the

46

Hall-effect sensor (for RPM measurement). Because it is a bearing race and a shaft seal

race, it will be made out of mild steel and will be ground.

The bearings chosen are standard deep-groove ball bearings. They offer good

reliability, are readily available and are inexpensive. The shaft seals are single lip design

with an integral garter spring to make them self adjusting to wear.

The inlet and outlet passages were analyzed using centrifugal pump equations

obtained in the Introduction to Fluid Mechanics textbook. The inlet passage delivered the

fluid normal to the blades of the impeller, and the outlet passage allowed fluid to leave

the impeller tangentially. The diameters of both passages were found by using the

following equation (equation 6.2.1) was used:

22

2 2 rbVRQb

π= Equation 6.2.1

In this equation b2 is the diameter of the passage; Q is the mass flow rate of the fluid, R2 is

the radius of the impeller at the passage point, and Vrb2 is the velocity relative to the blade.

For the inlet passage Vrb2 was found graphically by using an iterative method and using

30 (ft/s) as an initial guess the results can be found in (fig. 6.2.1). These values for Vrb2

were then substituted into equation 6.2.1 to find the corresponding values of b. During

this analysis though b seemed to result in vary small values as can be seen in table in the

appendix. This makes sense however for such large Vrb2 values minimizing the outlet

hole would be preferable. Due to machining purposes b was decided to be increase, also

maximizing Vrb2 is not an important design point so figure 6.2.2 was created to analyze

the effect of varying b on Vrb2. This makes sense; as you limit the area fluid has to

escape the passage would act like a nozzle. The value of 1� was decided upon for

pragmatic reasons. This was done for both passages inlet and outlet.

47

Vrb (ft/s) vs. b (for β= 90o)

0.000338

0.00034

0.000342

0.000344

0.000346

0.000348

0.00035

0.000352

0.000354

0.000356

0.000358

30.6 30.8 31 31.2 31.4 31.6 31.8 32 32.2 32.4

Vrb

bFigure 6.2.1

48

Vrb (ft/s) vs. b (for β= 90o)

0.000338

0.00034

0.000342

0.000344

0.000346

0.000348

0.00035

0.000352

0.000354

0.000356

0.000358

30.6 30.8 31 31.2 31.4 31.6 31.8 32 32.2 32.4

Vrb

b

Figure 6.2.1

Figure 6.2.2 � Water Brake Model Exploded View

49

6.3. Torque Arm Design

The purpose of a torque arm is to, as its name implies, measure torque. This is done

by mounting a strain gage to the surface of the torque arm near the impeller housing. As

the impeller turns, it churns the water inside the casing. The more water inside the casing

and/or the faster the engine turns, the greater the braking force exerted on the engine.

Viscous friction inside the housing will cause it to rotate, and by having an arm mounted

to the housing that in turn presses against a hard stop at its free end, an internal moment

in the arm is produced. A strain gage is mounted to the surface of the arm at a location

closest to the housing (where the internal moment will be the greatest) and by measuring

this strain, the user can back-calculate the torque being exerted by the engine.

The calculations involved taking the maximum output torque of the engine and

determining the corresponding distance/force combinations of the arm. Once this was

done, several cross-sectional dimension combinations were chosen to analyze and the

respective moments of inertia were calculated. Aluminum was chosen for the material of

the arm for its low weight, relatively low cost (for the sizes required), and good metal

working properties. Max Compressive and Tensile Bending Stresses were calculated

next, at which point the Maximum Deflection and Maximum Slope of each arm were

found. While the slope calculation was performed more of as an exercise, the deflection

calculation was the important one since it was critical to know if the deflection of the

chosen cross-sections would be too large or too small. The ½� x ½� x 16.4� bar was

chosen since it is small enough to allow for visible deflections but not so much so that the

50

bending stresses would be too high. In addition, it was desirable to have the arm not

exceed the width of the cart on which everything is mounted.

The last necessary computation was determining strain, and Equation 6.3.1 was

used was for the case of uniaxial strain:

σ = Eε (Equation 6.3.1)

Where σ = bending stress, E = elastic modulus, and ε = strain. This is the value that will

be read directly from the strain gage on the completed dynamometer. Since the elastic

modulus for the material of the arm is known, one can then calculate the resulting

bending stress. From here, the bending stress formula, Equation 6.3.1

σ = Mc/I (Equation 6.3.2)

is used in the form M = σI/c. The moment of inertia, I, and distance from neutral axis to

surface, c, can be calculated and measured, respectively, at which point the moment may

be calculated. All calculations can be found in the appendix of this document.

6.4. Motor Mounting Design and Setup

The Kohler motor to be used with the engine dynamometer test cell vibrates when

running. This means that when the motor is attached to the cart we plan to use the

vibrations will be transmitted throughout the cart and into other components. These

vibrations have to be considered because the amplitudes of the transmitted forces can

easily cause damage and may lead to failure of DAQ equipment, sensor, computer or any

other device attached the cart.

51

The problem was analyzed as a single degree of freedom, and the motor was

modeled as a mass with a harmonic force = Fcos(ωt). The cart was modeled as a mass

that was supported by a spring with very high stiffness and a deflection of zero.

Essentially the cart is a fixed mounting surface for the motor with the very high spring

rate.

This in mind, the motor needs to be isolated so there is very little to no vibration

forces transmitted to the cart. Ideally, the engine needs to sit on a cushion of air, which

would transmit no vibrations. The design calls for a spring/damper mount that is very

soft and can absorb large shocks.

After an effort to solve the problem it was seen that an analytical solution may be

very difficult to find. The team did not have enough information on the engine to

calculate the eccentric mass. This eccentric mass causes an imbalance in the rotating

assembly of the engine. This imbalance is the harmonic force that is transmitted. Also,

measuring the transmitted force of the engine could have been done with equipment in

the Vibrations Lab but due lack of time and experience with lab equipment this was not

an option.

The problem was then discussed with Dr. Kochersberger, a vibrations professor at

RIT. His expertise suggested avoiding analyzing the vibrations problem due to its

complexity. With the nature of use of a dynamometer, the engine will be constantly run

at different speeds with varying loads. This creates an infinite range of calculations and

measuring. These constantly changing conditions make it extremely difficult to find an

ideal spring/damper motor mount. Dr. Kochersberger recommended searching machine

components suppliers to see what is available and most effective.

52

McMaster (www.McMaster.com) has a wide range of spring/damper mounts for

motors. After searching the site, a mount was found under the �Vibration Damping

Mounts� sections in their online catalogue (pp.1218). The �Vibration Damping Mounts�

are described to isolate vibration, shock, and noise transmitted from machinery. On

pp.1223 of their online catalogue, �Steel Spring-Action Mounts� appear to be the best

solution to isolate engine vibrations. They are designed for high deflections and are

claimed to provide the best vibration, shock, and noise isolation. The mount chosen for

this project can handle a 60lb load with a deflection of 1.3in. This mount has a spring

rate of 46.2lb/in and there will be four of them to support the engine.

Figure 6.4.1 shows the specifications of the mount design to be used.

Compression

Flange

Deflection Flange Hole Hole

Thread @ Max. Load (A) (B) (D) (E)� Ctr. to Ctr. Dia.*

3/8"-16 1.3" 3 3/8" 5 7/8" 2 3/8" 3" 5" 7/16" 6219K83 $30.17

3/8"-16 1.3" 3 3/8" 5 7/8" 2 3/8" 3" 5" 7/16" 6219K84 30.17

3/8"-16 1.2" 3 3/8" 5 7/8" 2 3/8" 3" 5" 7/16" 6219K85 30.17

3/8"-16 1.0" 3 3/8" 5 7/8" 2 3/8" 3" 5" 7/16" 6219K86 30.17

3/8"-16 0.8" 3 3/8" 5 7/8" 2 3/8" 3" 5" 7/16" 6219K87 30.17

3/8"-16 0.5" 3 3/8" 5 7/8" 2 3/8" 3" 5" 7/16" 6219K88 32.98

3/8"-16 0.5" 3 3/8" 5 7/8" 2 3/8" 3" 5" 7/16" 6219K89 35.44

1/2"-13 1.02" 5 1/4" 7 3/4" 3" 3 1/2" 6 1/2" 5/8" 6219K91 43.60

1/2"-13 0.83" 5 1/4" 7 3/4" 3" 3 1/2" 6 1/2" 5/8" 6219K92 48.09

1/2"-13 0.74" 5 1/4" 7 3/4" 3" 3 1/2" 6 1/2" 5/8" 6219K93 48.09

1/2"-13 0.70" 5 1/4" 7 3/4" 3" 3 1/2" 6 1/2" 5/8" 6219K94 50.33

1300

1500�Bolt length. * Flange hole is slotted.

Steel Spring-Action Mounts High-deflection mounts provide the best vibration, shock, and noise isolation for slow-operating machines (machinery operating at speeds as low as 500 rpm). The upper and lower cast iron housings keep the steel spring contained and help prevent horizontal movement of the mount. Neoprene between the housings prevents metal-to-metal contact, while a neoprene pad bonded to the base plate provides additional resistance to movement. These mounts also provide leveling capabilities (for best results, adjust leveling bolt so that upper housing is 1/4"- 1/2" above the top of the lower housing). Mounts are furnished with a mounting bolt and nut. Temperature range is -40° to +160° F.

450

700

900

1100

100

165

260

370

lbs. Each

60

Max.

Load,

(Figure 6.4.1) Source: www.mcmaster.com, page 1223 online catalogue

In the design facet of this project an experiment will be conducted to ensure these

specified mounts effectively isolate the vibration of the engine. This experiment will

place the engine and mounts on a surface similar to the final mounting platform and

53

measure for any transmitted vibrations. If a problem exists a vibrations analysis will be

required to determine the corrective actions the team needs to make.

6.5. Sensor Placement and Mounting Pressure sensors will be mounted and placed in the engine to measure intake

pressure and combustion pressure. Measuring intake pressure will be done by locating a

pressure transducer in the intake runner. A hole will be drilled and tapped for the size of

the transducer to screw it in just after the carburetor. The location of the hole is easy to

access along with plenty of material to work with. The pressure transducer for measuring

combustion pressure will be located in the cylinder head next to the spark plug. Again, a

hole will be drilled and tapped to the size of the transducer where there is plenty of

material to mount the transducer while leaving easy access. The combustion pressure

transducer will not interfere with valves, spark plug, piston, and cooling fins. Figure

6.5.1 depicts the approximate position of the in-cylinder pressure transducer.

54

(Figure 6.5.1)

Type-K thermocouples will be mounted in the engine to measure temperatures of

oil, intake and exhaust. The oil temperature sensor will be placed in a drain plug in the

bottom of the crank case that is not used for anything. A hole will be drilled and the

thermocouple will be mounted in the plug with a high-temperature epoxy. Both intake

and exhaust thermocouples will be mounted in the intake runner and exhaust pipe by

drilling hole and sealing them with an epoxy.

The engine�s air flow will be measured with an air flow meter and Mass-Air-Flow

(MAF) sensor. This will be done by modifying the air flow meter pipe and the engine�s

air cleaner so they can be attached or detached if needed. Within the air cleaner the MAF

sensor will be mounted with a small bracket so as to not disturb air flow into the engine.

An Oxygen (O2) sensor and Hydro-Carbon sensor will be mounted in the exhaust

pipe to tell what air-fuel ratio the engine is running at and the amount of Hydro-Carbons

going out the tale pipe. To do this, the exhaust pipe will have a hole drilled and a

threaded bung will be welded in place. With the bung welded in place the O2 sensor can

easily be screwed in and tightened down. The Hydro-Carbon sensor will be mounted

inside the exhaust pipe or muffler.

Measuring engine speed (RPM) will be done using a Hall-Effect sensor. The

Hall-Effect sensor consists of small magnets and a pick-up sensor. The collar on the

water brake will have four equally spaced counter-bores drilled. The magnets will be

pressed into the counter bores. The pick-up sensor for the Hall-Effect will be mounted to

the case of the water brake near the rotating collar where the magnets are.

55

To measure torque from the engine a torque arm will be used with a strain gauge.

The torque arm is attached near the center of the water brake housing and the other end

rests on a stop. The strain gage will be attached to the end of the torque arm that is

secured to the water brake housing.

6.6. Data Acquisition Design and Setup

The DAQ for the pilot production dynamometer system is to be provided by the

Kate Gleason College of Engineering. Currently RIT owns a number of DAQ carts for

coursework and research. These carts meet and exceed all requirements of the needs

assessment and data collection. The equipment is all National Instruments brand. Figure

6.6.1 shows the equipment included on the cart, to be used by the team.

DAQ Multifunction DAQ PCI Card

Rack Mounted Terminal Accys

Rack Mounted Terminal Accys

Rack Mounted Terminal Accys

Chassis Strain Gauge Input Module Isolation Amplifier Signal Conditioning Module Feedthrough Panel Multiplexer Input Module Thermocouple Input Module

(Figure 6.6.1)

The team will use the thermocouple input module to record the intake, exhaust, and

engine temperatures. The strain gauge input module will record torque output of the

engine. The pressure transducers, Hall-Effect sensor, oxygen sensor, mass air flow

56

sensor, and emissions equipment will all be directed into the DAQ system through the

rack mounted terminals.

Also included in the cart setup is a desktop computer running National

Instrument�s LabVIEW software. The focus of the DAQ portion of the senior design

team will be to construct a program within LabVIEW to interpret all the readings from

the system sensors. Preliminary goals of the design process, consulting with RIT and

National Instruments staff, have ensured that the DAQ system is capable of these

requirements. During the next phase of the design process all programming will be

implemented.

The main goals of the DAQ software interface include:

• Obtaining all required measurements as addressed in the needs assessment

and project specifications.

• Creating an output file of data that can easily be analyzed and interpreted

by the user. This will most likely be a Microsoft Excel spreadsheet.

• Build a graphical-user-interface.

Design work is straight forward. The sensors plug into the DAQ equipment, and

then need to be calibrated according to manufacturer requirements. The calibration can

be done using the LabVIEW software or a basic voltmeter and ammeter. The sensors

output either a voltage or current reading. The DAQ equipment measures these outputs

and the LabVIEW software program interprets these readings into measurements.

57

6.7. Controls and User-Interface Design The needs assessment requires the dynamometer system to be easily operated and

intuitive to its users. The main user-interface will be the DAQ computer and the

LabVIEW graphical user interface, GUI. The GUI will display on screen virtual gauges.

These gauges will show current characteristics of the engine and dynamometer including;

engine speed, engine torque and power, intake and exhaust temperature, engine oil

temperature, air-fuel ratio, and emissions hydrocarbon concentration.

Starting up the entire dynamometer system will include powering up all electronic

equipment, turning on the flow into the water brake at the tap, and starting the engine.

The electronic equipment will be started by plugging the DAQ cart into a

conventional 120VAC outlet and turning on the computer and DAQ equipment. A valve

will start and stop the water flow into the system. A globe valve, downstream the main

valve and before the water brake inlet, will be used to control load placed on the engine

by the dynamometer. The engine will be pull started by the user.

Operating the dynamometer system will involve varying engine speed, water

brake load, and recording data.

The engine speed will be controlled by a push-pull cable and lever assembly.

This system will be connected to the Kohler engine throttle. The Kohler engine throttle is

outfitted with a torsion return spring; this design automatically closed the throttle when

there is no external force applied. As the lever is pulled and pushed the throttle will open

and close changing engine speed.

The dynamometer load is controlled by regulating the amount of fluid allowed

into the water brake. A globe valve allows more fine tuning control than a convention

58

gate valve. Closing the globe valve will reduce the amount of load; a fully open valve

will produce maximum loading conditions.

The throttle push-pull assembly and globe valve will be mounted next to one

another to allow safety and ease of operation.

Data logging will be triggered using the LabVIEW GUI and computer. Using the

computer mouse to click an on-screen button will begin data collection.

A Visual Flow-meter will provide a visible arbitrary gauge. This will be mounted

to show the air flow into the Kohler engine. As the engine speed and dynamometer

change the flow meter will visually illustrate the dynamics processes. The gauge is

simply a cylinder encasing a floating sphere. As the flow increases the sphere rises in the

cylinder.

6.8. Structure and Assembly The entire dynamometer system is to be mounted on to a procured cart. The

engine, water brake, computer system, and DAQ will be place on the mobile cart.

The Kohler engine will be mounted to the cart using the vibration damping

mounts. The mounts will be secured directly to the cart surface.

The engine drive shaft will be drilled and tapped in order to provide a mounting

point for the water brake assembly. The dynamometer will utilize a hollow collar

cylinder to mount to the engine drive shaft. The impeller will be press-fit onto the collar.

The collar will then pass through the casing bearings and oil seals allowing the impeller

59

to freely spin within the casing. The collar and water brake assembly will be bolted to

the drilled and tapped engine drive shaft.

The collar will protrude from the water brake and allow a mounting point for the

magnets to be used be the Hall-Effect sensor. The actual sensor will be mounted fixed on

the casing and measure the engine speed off the spinning collar.

The torque arm will be bolted to the outside of the water brake casing. The arm

will rest on a stop to prevent the dynamometer from rotating under load.

For the pilot production, the RIT provided DAQ system will remain on its original

cart, even though the dynamometer system has space available. Since the DAQ system

may have other future uses it will remain separate for flexibility.

The throttle will be mounted to the top surface of the cart. The load controlling

globe valve will mount in a hole next to the throttle.

Figure 6.8.1 � Assembly Model

60

7. Budget Part Name Part Number Material Quantity Vendor Vendor Part Number Price Line PriceImpeller Dyn-001 Aluminum 0.2 Yard $120.00 $24.00Collar Dyn-002 Mild Steel 1 Yard $2.00 $2.00Ball Bearing Dyn-004 Steel 2 McMaster 60355K82 $10.77 $21.54Oil Seal Dyn-005 Steel 2 Chicago Rawhide 12577 CRW1 $7.00 $14.00Cart Dyn-006 Steel 1 McMaster 2892T54 $380.00 $380.00Casing Dyn-007 Aluminum 0.25 Yard $120.00 $30.00Back Plate Dyn-008 Aluminum 0.05 Yard $120.00 $6.00Torque Arm Stop Dyn-009 Steel 1 Yard $1.00 $1.00Engine Mount Dyn-010 Rubber & Cast Iron 4 McMaster 6219k83 $30.17 $120.68Torque Arm Dyn-011 Aluminum 1 Yard $12.00 $12.00Tachometer Sensor Bracket Dyn-012 Aluminum 1 Yard $1.00 $1.00Thermocouple (J) Dyn-201 1 (5 Pack) Superlogics TC-61XJBEX36A $60.20 $60.20Thermocouple (K) Dyn-202 1 (5 Pack) Superlogics TC-61XKBEX72A $44.00 $44.00In Cylinder Pressure Transducer Dyn-203 1 Optrand PSI Plug 3ksi $645.00 $645.00Pressure Transducer Dyn-204 1 Superlogics Press-ICP-101A02 $475.00 $475.00MAF Sensor Dyn-205 1 TSI Flowmeters 4226-01-02 $245.00 $245.00MAF Cable Dyn-206 1 TSI Flowmeters 4225/4226/4235-x-x $19.00 $19.00Strain Gauge Dyn-207 1 Superlogics Strain-ICP-740B02 $195.00 $195.00Hall Effect Sensor Dyn-208 1 Radio Shack 276-1646 $2.00 $2.00Rare Earth Magnets Dyn-209 2 Radio Shack 64-1895 $2.00 $4.00Wideband Oxygen Sensor Dyn-210 1 OxygenSensor.net 36531-P07-003 $195.00 $195.00Hydrocarbon Sensor Dyn-211 1 Thermo-Electro FX-IR-67-0022-01 $1,380.00 $1,380.00Multifunction DAQ PCI Card Dyn-301 1 National Instruments NI-PCI-6052E $1,595.00 $1,595.00Rack Mounted Terminal Accys Dyn-302 1 National Instruments NI-TC-2095 $395.00 $395.00Rack Mounted Terminal Accys Dyn-303 1 National Instruments NI-BNC-2095 $395.00 $395.00Rack Mounted Terminal Accys Dyn-304 1 National Instruments NI-BNC-2090 $395.00 $395.00Chassis Dyn-305 1 National Instruments NI-SCXI-1001 $1,595.00 $1,595.00Strain Gauge Input Module Dyn-306 1 National Instruments NI-SCXI-1520 $2,295.00 $2,295.00Isolation Amplifier Dyn-307 1 National Instruments NI-SCXI-1125 $1,395.00 $1,395.00Signal Conditioning Module Dyn-308 1 National Instruments NI-SCXI-1531 $2,295.00 $2,295.00Feedthrough Panel Dyn-309 1 National Instruments NI-SCXI-1180 $95.00 $95.00Multiplexer Input Module Dyn-310 1 National Instruments NI-SCXI-1104 $1,295.00 $1,295.00Thermocouple Input Module Dyn-311 1 National Instruments NI-SCXI-1102 $1,295.00 $1,295.00Muffler Casing Dyn-901 1 Supertrapp 317-0875 $33.55 $33.55Muffler Core Dyn-902 1 Supertrapp 310-0400 $50.35 $50.35Push-Pull Cable Dyn-903 1 McMaster 3125K44 $25.55 $25.55Push-Pull Cable Lever Dyn-904 1 McMaster 1373K13 $33.25 $33.25Globe Valve Dyn-905 1 McMaster 4600K14 $28.00 $28.00Hose Dyn-906 1 McMaster 5683K97 $32.09 $32.09Fittings Dyn-907 1 Home Depot $10.00 $10.00Fasteners Dyn-908 1 Home Depot $10.00 $10.00Gas Tank Dyn-909 1 Kohler Command 5 Fuel Tank $44.95 $44.95

Total $17,189.16Total minus RIT Freebies $4,144.16

61

8. Future Plans At this point the senior design team has completed the first six facets of the

automotive laboratory development project. The team is now ready to begin building,

assembling, and experimentation of the open-loop water brake dynamometer system.

All machining and assembly will be conducted in-house using the RIT machine

shop facilities. All work will be conducted by team members eliminating cost of hired

machinists and labor. As soon as the raw material is in stock and accounted for, all

required machining can begin immediately.

Preliminary testing must be done concerning the vibration mounting of the

engine. This experiment will verify proof-of-concept for the design specified motor

mounts. The Kohler engine will be mounted on a scrap piece of material similar to the

cart mounting surface using the intended engine mounts. In order to pass this test the

mounts must effectively isolate the motor vibrations from the mounting surface. Upon

graduation from this experiment, the engine and motor mounts can be assembled onto to

the cart. This is a key step since the rest of the dynamometer assembly depends on the

engine being mounted.

Software programming of LabVIEW can begin immediately. The first task of the

DAQ team is to setup the system to record the outputs from the system sensors. Upon

completion the sensors will be calibrated prior to mounting. After calibration the GUI

will be constructed.

Before sensor mounting, all necessary machining required for mounting can be

completed. The cylinder head will be drilled and tapped for the pressure transducer

mount. The intake and exhaust will be modified to accept respective thermocouples. The

62

mass air flow sensor will need be mounted prior to the intake. The exhaust will be fitted

with a sound deadening muffler, oxygen sensor, and emissions equipment. During this

work the engine driveshaft can be drilled and tapped for mounting of the water brake.

After calibration of the sensors, mounting will begin. Once placed, an experiment

will connect the sensors to the DAQ to check function of both systems.

Final assembly will entail mounting of all hardware and controls. This is the last

step in the build process.

A final experiment will be run with the entire assembly. The dynamometer

system will be used to conduct the experiment carried out in the Thermal Fluids

Laboratory class offered by the department of mechanical engineering. Accurately

completing this experiment along with addressing all product specifications in this report

will declare the design successful.

An operational and maintenance manual will be created. This document will be

used to address questions by future users.

The design package, experimentation results, and manual will provide adequate

knowledge for replication and future use of the dynamometer system.

63

8.1. Schedule A schedule has been developed for the RIT spring quarter, 20033. This timeline

will keep the team on target to complete all project goals.

March April MayTasks 8 15 22 29 5 12 19 26 3 10Procure Raw MaterialsCollect sensors and FittingsLabVIEW programmingPriliminary Engine Vibrations ExperimentSensor CalibrationWater Brake MachiningSensor MountingFinal AssemblyFinal Experiment and TestingCreate maintenance and operation manualCDRTechnical Documentation

9. Conclusion

The team has completed the first five processes of design this quarter. These

processes included needs assessment, project objectives and specifications, concept

development, feasibility assessment, analysis and synthesis of the design, and the

preliminary design.

The proposed design will be cost effective, more sensitive to the needs of the

instructors conducting the labs, and more sensitive to the students trying to participate in

the labs. The goal is to produce a working dynamometer that is both visual and practical.

It also needs to be safe, user friendly, and robust, however it still needs to be accurate and

give a good representation of the motor characteristics.

64

By developing four concepts and assessing their feasibility the concept that would

best support these features was found. These concepts included; an open � loop water

brake dynamometer, a closed � loop water brake dynamometer, a resistive load electric

generator dynamometer, and a mechanical brake dynamometer. Even though each

concept proved not to be completely unfeasible the open � loop water brake design was

decided to be the best given the mechanical nature of the design, the budget provided,

and the outcome of the feasibility assessment.

Many parameters were analyzed for the water brake. An FEA analysis was

completed on the casing of the water brake, along with calculations on the diameter of the

outlet passageway. The diameter of the impeller was taken into consideration, along with

the profile and thickness of the impeller blade. A stress analysis was completed on the

torque arm. This was done to ensure that the design would meet the set requirements.

By the end of spring quarter the team hopes to have fabricated and assembled a

functioning dynamometer, located and placed all needed sensors on the engine, and

properly programmed every output from the sensors into LabVIEW. The team will test

to make sure that the dynamometer properly loads the engine while all the sensors are

taking accurate readings. The team will also design some sample laboratory experiments

to show the abilities and the limitations of the dynamometer.

65

10. References Fox, Robert W., McDonald, Alan T. Introduction to Fluid Mechanics, 5th Edition. New York: John Wiley & Sons, Inc. Hensel, Edward. Personal Interview. 21 Jan. 2004. Juvinall, Robert C., Marshek, Kurt M. Fundamentals of Machine Component Design, 3rd Edition. New York: John Wiley & Sons, Inc. Kempski, Mark. Personal Interview. 19 Jan. 2004. Kochersberger, Kevin. Personal Interview. 16 Feb. 2004. Mc Nally, William. �All about specific speed 7-3�, http://www.mcnallyinstitute.com//07-html/7-03.html Moran, Michael J., Shapiro, Howard N. (2000). Fundamental of Engineering Thermodynamics, 4th Edition. New York: John Wiley & Sons, Inc. Pulkrabek, Willard W. Engineering Fundamentals of the Internal Combustion Engine, 1st Edition. New York: Prentice Hall. Sciremammano, Frank. Personal Interview. 29 Jan. 2004. Steinke, Mark. Personal Interview. 17 Dec. 2003. Wellin, John. Personal Interview. 21 Jan. 2004.

66

11. Appendix

A. Feasibility Assessment Scores and Radar Chart B. Impeller Calculations and Graphs C. Torque Arm Calculations D. Impeller and Casing FEA results E. Bearing Fatigue Life F. Drawing Package

67

A. Feasibility Assessment Scores and Radar Chart

R1 R2 E1 E2 S1 S2 S3 T1 T2 P1 P2Base Line: Water Brake Open Loop 2 2 2 2 2 2 2 2 2 2 2Water Brake Closed Loop 2 2 2 1 1 2 2 1 2 2 3Electro Generator 1 2 2 1 1 2 2 1 1 1 1Mechanical Brake 2 2 3 2 2 2 2 2 1 2 1

Feasibility Assessment

0

1

2

3R1

R2

E1

E2

S1

S2S3

T1

T2

P1

P2

P3

Base Line: Water BrakeOpen LoopWater Brake Closed Loop

Electro Generator

Mechanical Brake

68

B. Impeller Calculations and Graphs Constants

ω = 3600 RPMρ = 1.46 slug/ft3

Q = 1.5 GPMU = 35 ft/s

69

Impeller DiameterR2 (in) Tshaft (ft*lbf) Wm (hp)

1 1.8395957 1.260931.25 2.8743683 1.9702021.5 4.1390903 2.837091

1.75 5.6337618 3.8615972 7.3583828 5.043718

2.25 9.3129532 6.3834562.5 11.497473 7.88081

2.75 13.911942 9.535783 16.556361 11.34837

3.25 19.43073 13.318573.5 22.535047 15.44639

3.75 25.869315 17.731824 29.433531 20.17487

4.25 33.227697 22.775544.5 37.251813 25.53382

4.75 41.505878 28.449725 45.989892 31.52324

5.25 50.703856 34.754375.5 55.64777 38.14312

5.75 60.821633 41.689486 66.225445 45.39346

6.25 71.859207 49.255066.5 77.722918 53.27427

6.75 83.816579 57.45117 90.140189 61.78555

ResultsR2 (in) 7 61.78555

Blade angle vs. DiameterVrb (ft/s) 33.564933 initial guess

β (ο) V2 (ft/s)2 Vrb (ft/s)30 82.118232 33.5649335 110.80354 33.5711640 143.75434 33.5276145 180.9079 33.4505850 222.19352 33.3555 267.53258 33.2322760 316.8388 33.1017265 370.01831 32.9613670 426.96988 32.8133975 487.58511 32.6594480 551.7486 32.5007785 619.33822 32.3383790 690.22531 32.1730295 764.27492 32.00538

100 841.34611 31.83596105 921.29217 31.66524110 1003.9609 31.49361115 1089.195 31.32142120 1176.8321 31.14896125 1266.7054 30.97652130 1358.644 30.80435135 1452.4727 30.63268140 1548.0129 30.46173145 1645.0828 30.2917

Resultsβ (ο) 90 Max

Vrb (ft/s) 32.173024 33.57116

Vrb (ft/s) vs. b (for β= 90o)Initial guess @ 90o

Vrb (ft/s) Vrb (ft/s) b (in)30 30.768902 0.000356

31.098384 31.263147 0.0003531.791743 31.544353 0.00034732.239901 31.714612 0.00034532.542257 31.824792 0.00034432.753464 31.899663 0.00034332.909578 31.953956 0.00034233.02943 31.995057 0.000342

33.121101 32.026167 0.00034233.191032 32.049713 0.000341

33.2485 32.068944 0.00034133.298189 32.085488 0.00034133.341121 32.099721 0.00034133.378194 32.111966 0.00034133.410193 32.122502 0.00034133.437799 32.131566 0.00034133.461609 32.139366 0.0003433.482137 32.146078 0.0003433.499833 32.151854 0.0003433.515084 32.156824 0.0003433.528224 32.161101 0.0003433.539546 32.164783 0.0003433.549298 32.167951 0.0003433.557698 32.170677 0.0003433.564933 32.173024 0.00034

70

b (in) vs. Vrb (ft/s)b (in) Vrb (ft/s)

1/16 0.17507041/8 0.08753523/16 0.05835681/4 0.04376765/16 0.03501413/8 0.02917847/16 0.02501011/2 0.02188389/16 0.01945235/8 0.017507

11/16 0.01591553/4 0.0145892

13/16 0.0134677/8 0.012505

15/16 0.01167141 0.01094191 1/16 0.01029831 1/8 0.00972611 3/16 0.00921421 1/4 0.00875351 5/16 0.00833671 3/8 0.00795771 7/16 0.00761181 1/2 0.00729461 9/16 0.00700281 5/8 0.00673351 11/16 0.00648411 3/4 0.00625251 13/16 0.0060369

71

Power vs. Impeller Diameter: Engine Speed 3600rpm

0

10

20

30

40

50

60

70

0 1 2 3 4 5 6 7 8R2 (inches)

Wm

(HP)

Blade angle vs Vrb2: at 3600rpm

0

20

40

60

80

100

120

140

160

30 30.5 31 31.5 32 32.5 33 33.5 34Vrb2 (ft/s)

β (ο )

72

Vrb (ft/s) vs. b (for β= 90o)

0.000338

0.00034

0.000342

0.000344

0.000346

0.000348

0.00035

0.000352

0.000354

0.000356

0.000358

30.6 30.8 31 31.2 31.4 31.6 31.8 32 32.2 32.4Vrb

b

b (in) vs. Vrb (ft/s)

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

0 1/5 2/5 3/5 4/5 1 1 1/5 1 2/5 1 3/5 1 4/5 2

b

Vrb

73

Impeller Efficiency at 3600rpm

0

0.005

0.01

0.015

0.02

0.025

0.03

0 500 1000 1500 2000 2500

Nscu

η

74

C. Torque Arm Calculations

Force

ft-lbf in-lbf in ft 3.35 lbf b h in4

8.4 100.8 6 0.5 2.7 16.8 0.5 0.5 0.005212 1.0 8.7 8.4 1 1 0.083318 1.5 14.7 5.624 2.0 20.7 4.230 2.5 26.7 3.436 3.0 32.7 2.842 3.5 38.7 2.448 4.0 44.7 2.1

Output Torque

Possible combinations of Torque Arm parameters to counteract this

torque

Note: This is the length measured from center of output shaft to location of

applied force.

Arm Dimensions, inchesLength

Note: See Drawing.

Distance from center of first hole to end of arm, inches

Moment of Inertia, Ix = 1/12*b*h3

Note: Neutral Axis is in the center of the bar because the bar is a symmetrical shape.

E = 10000 ksi

ctop cbottomMax Tensile

(top)Max Compressive

(bottom)inches inches psi psi rad degrees rad degrees0.25 -0.25 4838.4 -4838.4 0.0011 0.065 0.00007 0.00410.5 -0.5 604.8 -604.8 0.0060 0.346 0.00038 0.0216

0.0115 0.661 0.00072 0.04130.0172 0.985 0.00107 0.06160.0229 1.313 0.00143 0.08200.0287 1.642 0.00179 0.10260.0344 1.972 0.00215 0.12320.0402 2.303 0.00251 0.1439

For 6061-T6,

Maximum Slope

0.5 x 0.5 1 x 1

Bending Stress, σx = Mc/I

c = perpendicular distance from the neutral axis to a point farthest away from the neutral

axis, where σmax acts.

0.5 x 0.5 1 x 1 0.5 x 0.5 1 x 1

inches inches Max εgage = 1.0E-04-0.0020 -0.0001 4.84E-04 6.05E-05-0.0348 -0.0022 Fail Pass-0.1127 -0.0070-0.2367 -0.0148-0.4070 -0.0254-0.6237 -0.0390-0.8868 -0.0554-1.1964 -0.0748

Normal Strain, upper surface, ε = σ/EMaximum Displacement

75

Torque Arm

y = 8.4x-1

0.0

5.0

10.0

15.0

20.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

Length, ft

Req

uir

ed

Fo

rce,

lbf

Displacement vs. Length

-1.400-1.200-1.000-0.800-0.600-0.400-0.2000.0000.200

0 10 20 30 40 50

Length, inches

Max

imum

Dis

plac

emen

t, in

ches

0.5 x 0.5 1 x 1

76

Displacement vs. Reaction Force

-1.400-1.200-1.000-0.800-0.600-0.400-0.2000.0000.200

0.0 5.0 10.0 15.0 20.0

Reaction Force, lbf

Dis

plac

emen

t, in

ches

0.5 x 0.5 1 x 1

77

D. Torque Arm and Casing FEA

78

E. Bearing Fatigue Life

Engine Torque = 8.4 ft*lbTorque Arm Length = 1.25 ftReaction Force = 6.72 lb

Bearing Inner Diameter = 1.25 inBearing Inner Diameter = 0.104167 ftTangential Force On Bearing Inner Race = 80.64 lb

Bearing Dynamic Load Rating = 2517 lbFactor Of Safety = 31

Static Loading = 15 lb

Fequiv. dynamic = Fradial static + Fdynamic

Fequiv. Dynamic = P = 95.64 lb

L10 = 18227.66 millions of revolutions

RPM = 3600Life = 84387 hours of continuous operation

*Calculations Assume Perfect Operating Conditions With No Contaminants*

F. Drawing Package