PRESENTATION REPORT ON

Dynamometers

Submitted By:

Anand Kumar (ME/13/710)

Department of Mechanical Engineering

SHRI BALWANT INSTITUTE OF TECHNOLOGYApproved by AICTE, Min of HRD, Govt of India & DTE, Govt of HaryanaAffiliated to DCR University of Science and Technology, Murthal, Sonepat

Meerut Road (Pallri), Near DPS, Sonepat-131001, Haryana

DYNAMOMETERS

Abstract

My report focuses on the topic Dynamometers and its operations. In the following report I

have studied about the basics of Dynamometers, their operations and their uses. As well as the

report covers the inside view of the Dynamometers and its operations.

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DYNAMOMETERS

CERTIFICATEThis is certify that the seminar Topic entitled as Dynamometers and submitted by ANAND KUMAR having Roll No ME/13/710, embodies the bonafide work done by him under my supervision.

Signature of Supervisor:

Place:

Date:

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DYNAMOMETERS

Table of Contents

1 INTRODUCTION.......................................................................................................................................................5

2 PRINCIPLE OF OPERATION.................................................................................................................................6

2.1 CONSTANT FORCE...................................................................................................................................................................6

2.2 CONSTANT SPEED...................................................................................................................................................................6

3 DYNAMOMETER DESCRIPTION.........................................................................................................................8

4 TYPES OF DYNAMOMETERS................................................................................................................................9

4.1 ABSORPTION DYNAMOMETERS............................................................................................................................................9

4.1.1 Prony Brake Dynamometer.......................................................................................................................................... 9

4.1.2 Rope Brake Dynamometer......................................................................................................................................... 10

4.2 TRANSMISSION DYNAMOMETERS......................................................................................................................................10

4.2.1 Belt Transmission Dynamometer............................................................................................................................ 10

4.2.2 Torsion Dynamometer................................................................................................................................................. 11

5 TYPES OF DYNAMOMETER SYSTEMS............................................................................................................12

6 HISTORY..................................................................................................................................................................13

7 REFERENCES..........................................................................................................................................................14

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DYNAMOMETERS

1 INTRODUCTION

A dynamometer is a device for measuring force, torque, or power. For example, the power

produced by an engine, motor or other rotating prime mover can be calculated by

simultaneously measuring torque and rotational speed (RPM). A dynamometer can also be

used to determine the torque and power required to operate a driven machine such as a pump.

In that case, motoring or driving dynamometer is used. A dynamometer that is designed to be

driven is called an absorption or passive dynamometer. A dynamometer that can either drive

or absorb is called a universal or active dynamometer.

In an engine dynamometer, water flow, proportional to the desired applied load, creates

resistance to the engine. A controlled water flow through the inlet manifold is directed at the

center of the rotor in each absorption section. This water is then expelled to the outer

dynamometer body by centrifugal force. As it is directed outward, the water is accelerated

into pockets on the stationary stator plates where it is decelerated. The continual acceleration

and deceleration causes the dynamometer to absorb the power produced by the engine.

Through this transfer of energy the water is heated and discharged.

Dynamometer is a device to measure the output (brake power) of a prime mover. The power

is measured by applying the fictional torque by means of a brake. By knowing the fictional

torque, the power of the engine can be calculated.

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2 PRINCIPLE OF OPERATIONAn absorbing dynamometer acts as a load that is driven by the prime mover that is under test

(e.g. Pelton wheel). The dynamometer must be able to operate at any speed and load to any

level of torque that the test requires. Absorbing dynamometers are not to be confused with

"inertia" dynamometers, which calculate power solely by measuring power required to

accelerate a known mass drive roller and provide no variable load to the prime mover. An

absorption dynamometer is usually equipped with some means of measuring the operating

torque and speed.

The Power Absorption Unit of a dynamometer absorbs the power developed by the prime

mover. This power absorbed by the dynamometer is then converted into heat, which

generally dissipates into the ambient air or transfers to cooling water that dissipates into the

air. Regenerative dynamometers, in which the prime mover drives a DC motor as a generator

to create load, make excess DC power and potentially - using a DC/AC inverter - can feed

AC power back into the commercial electrical power grid. Absorption dynamometers can be

equipped with two types of control systems to provide different main test types.

2.1 Constant Force

The dynamometer has a "braking" torque regulator the Power Absorption Unit (PAU) is

configured to provide a set braking force torque load, while the prime mover is configured to

operate at whatever throttle opening, fuel delivery rate, or any other variable it is desired to

test. The prime mover is then allowed to accelerate the engine through the desired speed or

RPM range. Constant Force test routines require the PAU to be set slightly torque deficient as

referenced to prime mover output to allow some rate of acceleration. Power is calculated

based on rotational speed x torque x constant. The constant varies depending on the units

used.

2.2 Constant Speed

If the dynamometer has a speed regulator (human or computer), the PAU provides a variable

amount of braking force (torque) that is necessary to cause the prime mover to operate at the

desired single test speed or RPM. The PAU braking load applied to the prime mover can be

manually controlled or determined by a computer. Most systems employ eddy current, oil

hydraulic, or DC motor produced loads because of their linear and quick load change

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DYNAMOMETERS

abilities. Power is calculated based on rotational speed x torque x constant, with the constant

varying with the output unit desired and the input units used.

A motoring dynamometer acts as a motor that drives the equipment under test. It must be able

to drive the equipment at any speed and develop any level of torque that the test requires. In

common usage, AC or DC motors are used to drive the equipment or "load" device.

In most dynamometers power (P) is not measured directly, but must be calculated from

torque (τ) and angular velocity (ω) values or force (F) and linear velocity (v):

or

Where.

P is the power in watts

τ is the torque in Newton meters

ω is the angular velocity in radians per second

F is the force in Newton

v is the linear velocity in meters per second

Division by a conversion constant may be required, depending on the units of measure used.

For imperial units,

Where,

Php is the power in horsepower

τlb·ft is the torque in pound-feet

ωRPM is the rotational velocity in revolutions per minute

For metric units,

Where,

PkW is the power in kilowatts

τN·m is the torque in Newton meters

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DYNAMOMETERS

3 DYNAMOMETER DESCRIPTION

A dynamometer consists of an absorption (or absorber/driver) unit, and usually includes a

means for measuring torque and rotational speed. An absorption unit consists of some type of

rotor in housing. The rotor is coupled to the engine or other equipment under test and is free

to rotate at whatever speed is required for the test. Some means is provided to develop a

braking torque between the rotor and housing of the dynamometer. The means for developing

torque can be frictional, hydraulic, electromagnetic, or otherwise, according to the type of

absorption/driver unit.

One means for measuring torque is to mount the dynamometer housing so that it is free to

turn except as restrained by a torque arm. The housing can be made free to rotate by using

trunnions connected to each end of the housing to support it in pedestal-mounted trunnion

bearings. The torque arm is connected to the dyno housing and a weighing scale is positioned

so that it measures the force exerted by the dyno housing in attempting to rotate. The torque

is the force indicated by the scales multiplied by the length of the torque arm measured from

the center of the dynamometer. A load cell transducer can be substituted for the scales in

order to provide an electrical signal that is proportional to torque.

Another means to measure torque is to connect the engine to the dynamometer through a

torque sensing coupling or torque transducer. A torque transducer provides an electrical

signal that is proportional to the torque.

With electrical absorption units, it is possible to determine torque by measuring the current

drawn (or generated) by the absorber/driver. This is generally a less accurate method and not

much practiced in modern times, but it may be adequate for some purposes.

When torque and speed signals are available, test data can be transmitted to a data acquisition

system rather than being recorded manually. Speed and torque signals can also be recorded

by a chart recorder or plotter.

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DYNAMOMETERS

4 TYPES OF DYNAMOMETERS

In addition to classification as Absorption, Motoring, or Universal, as described above,

dynamometers can also be classified in other ways. A dyno that is coupled directly to an

engine is known as an engine dyno. A dyno that can measure torque and power delivered by

the power train of a vehicle directly from the drive wheel or wheels (without removing the

engine from the frame of the vehicle), is known as a chassis dyno. Dynamometers can also be

classified by the type of absorption unit or absorber/driver that they use. Some units that are

capable of absorption only can be combined with a motor to construct an absorber/driver or

"universal" dynamometer.

4.1 Absorption DynamometersIn these types of dynamometers, the entire power produced by the prime mover is absorbed

by the frictional resistance of the brake and is transformed into heat, during the process of

measurement. The absorption type of dynamometers can be classified as:

4.1.1 Prony Brake DynamometerIt consists of two wooden blocks placed around a pulley fixed to the shaft of the prime

mover, whose power is to be measured. The blocks are clamped by means of two bolts and

nuts. A helical spring is provided between the nut and the lever attached to it and carries a

weight W at its other end. A counter weight is placed at the other end of lever that balances

the brake when unloaded. Two stops are provided to limit the motion of the lever. When the

brake is to be put in operation, the long end of the lever is loaded with suitable weight W and

the nuts are tightened until the prime mover shaft runs at a constant speed and the lever is

horizontal position. Under these conditions, the moment due to the weight W must balance

the moment of the frictional resistance between blocks and pulley.

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DYNAMOMETERS

Fig 1: Prony brake Dynamometer

4.1.2 Rope Brake DynamometerIt consists of one or more ropes wound around the flywheel or rim of the pulley, fixed to the

shaft of the prime mover. The upper end of the ropes is attached to a spring balance while the

lower end is kept in position by applying a dead weight. In order to prevent the slipping of

the ropes over the flywheel, wooden blocks are placed at intervals around the circumference

of the flywheel. During operation of the brake, the prime mover is made to run at constant

speed. The frictional torque due to the ropes must be equal to the torque being transmitted by

the prime mover.

Fig 2: Rope brake Dynamometer

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DYNAMOMETERS

4.2 Transmission DynamometersIn these dynamometers, the energy is used for doing work. The power developed by the

prime mover is transmitted through the dynamometers to some other machine where the

power is suitably measured. This type of dynamometer can be classified as follows:

4.2.1 Belt Transmission DynamometerA belt transmission dynamometer consists of driving pulley, rigidly fixed to the shaft of the

prime mover. There is another driven pulley mounted on another shaft, to which the power

from pulley is transmitted. The pulleys are connected by means of a continuous belt passing

round the two loose pulleys, which are mounted on the lever. The lever carries a dead weight

at the one end, and a balancing weight is attached at the other end.

Fig 3: Belt transmission Dynamometer

4.2.2 Torsion DynamometerA torsion dynamometer is used to measure large power developed by a turbine or marine

engines. A large number of torsion dynamometers are used to measure the angle of twist.

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DYNAMOMETERS

Fig 4: Torsion Dynamometer

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5 TYPES OF DYNAMOMETER SYSTEMS

A 'brake' dynamometer applies variable load on the Prime Mover (PM) and measures the

PM's ability to move or hold the RPM as related to the "braking force" applied. It is usually

connected to a computer that records applied braking torque and calculates engine power

output based on information from a "load cell" or "strain gauge" and a speed sensor.

An 'inertia' dynamometer provides a fixed inertial mass load, calculates the power required to

accelerate that fixed and known mass, and uses a computer to record RPM and acceleration

rate to calculate torque. The engine is generally tested from somewhat above idle to its

maximum RPM and the output is measured and plotted on a graph.

A 'motoring' dynamometer provides the features of a brake dyne system, but in addition, can

"power" (usually with an AC or DC motor) the Prime Mover (PM) and allow testing of very

small power outputs (for example, duplicating speeds and loads that are experienced when

operating a vehicle traveling downhill or during on/off throttle operations).

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DYNAMOMETERS

6 HISTORY

The Graham-Desaguliers Dynamometer was invented by George Graham and mentioned in

the writings of John Desagulier in 1719. Desaguliers modified the first dynamometers, and so

the instrument became known as the Graham-Desaguliers dynamometer. The Regnier

dynamometer was invented and made public in 1798 by Edme Régnier, a French rifle maker

and engineer. A patent was issued (dated June 1817) to Siebe and Marriot of Fleet Street,

London for an improved weighing machine. Gaspard de Prony invented the de Prony brake in

1821. Macneill's road indicator was invented by John Macneill in the late 1820s, further

developing Marriot's patented weighing machine. Froude Hofmann, of Worcester, UK,

manufactures engine and vehicle dynamometers. They credit William Froude with the

invention of the hydraulic dynamometer in 1877, and say that the first commercial

dynamometers were produced in 1881 by their predecessor company, Heenan & Froude. In

1928, the German company "Carl Schenck Eisengießerei & Waagenfabrik" built the first

vehicle dynamometers for brake tests that have the basic design of modern vehicle test

stands.

The eddy current dynamometer was invented by Martin and Anthony Winther around 1931,

but at that time, DC Motor/generator dynamometers had been in use for many years. A

company founded by the Winthers brothers, Dynamatic Corporation, manufactured

dynamometers in Kenosha, Wisconsin until 2002. Dynamatic was part of Eaton Corporation

from 1946 to 1995. In 2002, Dyne Systems of Jackson, Wisconsin acquired the Dynamatic

dynamometer product line. Starting in 1938, Heenan & Froude manufactured eddy current

dynamometers for many years under license from Dynamatic and Eaton.

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DYNAMOMETERS

7 REFERENCES

Winther, J. B. (1975). Dynamometer Handbook of Basic Theory and Applications.

Cleveland, Ohio: Eaton Corporation

http://www.dynomitedynamometer.com/dyno-dynamometer-article.htm

http://www.explainthatstuff.com/how-dynamometers-work.html

http://www.setra.com/blog/test-and-measurement-dynamometer

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