10M134 AIC Assignment 1 & 2.pdf

7/27/2019 10M134 AIC Assignment 1 & 2.pdf

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Assignment 1 & 2

Submitted by:Chandan N10M134VII Sem Website

Advanced Internal

Combustion EnginesDr. Kumar G NAssistant ProfessorDept. of MechanicalEngineeringNITK Surathkal


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Assignment-1

1) What is your opinion in the relevance of IC Engines in today's

world?

Since over 100 years, the internal combustion engine has been the mainstay of the

automobile. But now due to increased concern about the environment and the dwindling

crude oil reserves and the long lead times in creating these fossil fuels have led to a

debate on reducing the use of IC engines. However in present situation, electric vehicles are

prohibitively expensive and fuel cell powered cars are still in initial stages of research. The

battery alone in an electric car can cost $20,000 and will remain so for some time.

Moreover, electric vehicles are unproven in the real world, which suggests the continued

dependence on IC engines. Engineers are working to build a better engine, one that runsmore efficiently and gets better gas mileage and there are alternative fuels like ethanol,

butanol, bio-diesel etc. Hence, IC engines are still very relevant in today's world and are

going to be important for years to come.

2) Why are you taking this course?

Internal combustion Engine is a vast field where lot of research has already been done but

still there is a lot of scope for future research as the known worldwide reserves of

petroleum are predicted to last for only 30 years. Air pollution is one of the other major

problems being faced by the world today. So this has created a situation to increase theefficiency and decrease emissions in an engine. By learning this course, a basic idea about

thermo-chemistry of fuels can be obtained and also ways to increase efficiency and

decrease emissions can be learnt.

3) List the technical specification of your favorite automobile vehicle.

My favorite vehicle is Koenigsegg Agera R. The Agera R is the only roadster Hypercar with

a detachable and stow able hardtop, thereby offering the best of two worlds. This, in

combination with 120 liters of luggage space, truly combines extreme performance with

everyday usability. Technical Specifications are given below:


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Performance

Power output: 1140 hp at 7100 rpmredline @ 7500 rpm

Torque: over 1000 Nm from 2700 to 7300 rpm

Max torque: 1200 Nm at 4100 rpm

Turbo: 1.4 bar boost pressure, 0.5 bar boost pressure @ 2300 rpm, Full turbo spool up

@ 2700 rpm

Acceleration: 0-100 km/h (0-62 mph) 2.8 sec, 0-200 km/h 7,8 sec, 0-200-0 km/h 12.6

sec, 0-300-0 km/h 21,19 sec

Braking distance: 30.5m (100-0 km/h)

Lateral g-force: 1.6g

Fuel consumption: Highway travel: 12.5 l/100km, Combined: 14,7/100km

Weight-to-power ratio: 1.19 kg/hp (dry weight)

Weight distribution: 44% front, 56% rear

Emission levels: Euro V and lev 2

Aerodynamics

Cd. 0.33 to 0.37 with adaptable rear wings.

Frontal Area: 1.873 m2

Total Downforce at 250 km/h: 300 kg

Flat underside of chassis. Venturi tunnels at rear of chassis/body.

Dimensions

Total length: 4293 mm (169)

Total width: 1996 mm (78.6)

Total height: 1120 mm (44.1)

Ground clearance: Rear: 100 mm (3.94) Front: 100 mm (3.94)

Wheelbase: 2662 mm.

Front track: 1700 mm. Rear track: 1650 mm.

Front overhang: 885 mm Rear overhang: 752 mm

Fuel capacity: 80 litres Luggage compartment: 120 litres (31.7 US gallons)


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Dry weight: 1330 kg

Curb weight 1435 kg (all fluids plus 50% fuel)

Maximum laden weight: 1650 kg (full tank, two passengers, full luggage)


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Assignment-2

1) Explain the following terms:

Engine continuous power:

The power which the engine is capable of delivering continuously between the normal

maintenance intervals stated by the manufacturer, at stated speed and under stated

operating conditions.

Indicated power:

Indicated Power is the total power developed by the combustion of the fuel in the com-

bustion chamber or it is the total power available inside the engine cylinder. It is denoted

by IP.

Brake power:

Brake Power is the total power available at the output shaft. This is the actual output

available to do work. It is denoted by BP.

Specific fuel consumption:

It is the quantity of fuel consumed per unit power produced per unit of time. It is generally

expressed in grams of fuel consumed per kWh. It can be expressed mathematically as the

ratio of fuel consumed in kg/h to the power developed in the engine. It is denoted by SFC.

2) What do you mean by?

Indicated thermal efficiency:

Indicated thermal efficiency is the ratio of work done by fuel combustion inside a cylinder

over a given time interval to the total heat content of the fuel supplied to the cylinder during

that time. It is denoted by ith and mathematically:

Mechanical efficiency:

Mechanical efficiency is defined as ratio of brake power(BP) to the indicated power (IP).

Mechanical efficiency takes all mechanical losses happening in the engine into account It is

denoted by m and mathematically:


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Volumetric efficiency:

Volumetric efficiency is the ratio of mass of air or charge actually induced to the mass of air

or charge corresponding to the cylinder volume at ambient conditions. It can also be defined

as ratio of volume of air or charge induced at ambient conditions to the stroke volume. It is

denoted by vol and mathematically:

Overall thermal efficiency:

It is defined as the ratio of heat converted to useful mechanical work to the chemical energy

input to the engine. It is denoted by th and mathematically:

Discuss any one method to find indicated power.

The method illustrated below is used to calculate Indicated power of slow speed engines

using indicator diagram. The engine indicator and indicator diagram is shown below:

Indicated power is usually measured by using indicator diagram. An indicator diagram is a

trace made by recording pressure gauge, called indicator, attached to the cylinder of a

reciprocating engine. An indicator diagram represents the work done in one engine cycle. The

same gas pressure at on the engine piston P and indicator piston I. The indicator piston is

loaded by a spring and it moves in direct proportion to change in pressure.

The motion of the indicator piston causes a pencil held at the end of the linkage L to move

upon a strip of paper wrapped around drum D. The drum is rotated about its axis by chord C,

which is connected through a reducing motion R to the piston P of the engine. The surface of

drum D moves horizontally under the pencil while the pencil moves vertically over the

surface and a plot of pressure upon piston vs. piston travel is obtained. Before tracing thefinal indicator diagram a pressure reference line is recorded by subjecting the indicator to the


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atmosphere and tracing a line at a constant pressure of one atmosphere. The area can be

measured by an instrument known as 'Planimeter' or by the use of the mid ordinates rule. On

modern engines this diagram can be continuously taken by employing two transducers, one

pressure transducer in the combustion space and other transducer on the shaft. Through the

computer we can thus get on line indicated diagram and power of all cylinders. The area is

then divided by the length of the diagram in order to obtain mean height. This mean height,when multiplied by the spring scale of the indicator mechanism, gives the indicated mean

effective pressures (Pim) for the cylinder. It can be defined mathematically as:

Indicated power is then calculated from Indicated mean effective pressure using the relation:

where,

A is the cross sectional area of the cylinder

L is the stroke length

N is the speed in rpm

n=0.5 for 4-stroke and n=1 for 2-stroke engines.

3) Explain the performance test of an engine according to I.S.

Testing of Constant Speed IC Engines for General Purposes According to IS: 1600-1960:This code applies to testing of constant speed reciprocating internal combustion engines of

the following types used for general purposes like:

(1) Compression ignition engines.

(2) Carburettor type engines, and

(3) Gas engines.

This code is not applicable to pressure charged engines, engines for road or rail traction

engines and engines for aircraft propulsion or aircraft auxiliaries.

General Requirements for Tests:

The manufacturer shall supply the performance characteristics of the engine prior to the

commencement of the tests. The engine shall be tested as offered to the purchaser. All parts

shall be in stock and all parts essential for engine operation should be included.

Accessories used on the engine under test shall be listed.

Preparation for Tests:

The engine shall be completely stripped and examined physically so that design features and

also the condition of the various parts may be noted before tests are, commenced.

After the physical examination the dimensions of the main working parts, listed below shall

be checked and recorded.

1. Cylinder head.2. Valves, valve seats, valve springs and valve guides


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3. Cylinder liner.

4. Piston Assembly.

5. Connecting rod small end big end bearings and connecting rod bolts.

6. Crankshaft, including bearings and journals and

7. Governor springs.

Preliminary Run:

The engine shall be subjected to preliminary run of 49 hours at rated speed under operating

temperatures as specified by the manufacturer in a non-stop cycle of 7 hrs each conforming to

cycles as shown in Fig below:

Preliminary Run Specifications

During the preliminary run, special attention shall be paid to engine vibration and quiteness.

The oil pressure shall be checked from time to time. Oil, coolant and fuel leaks shall be

rectified and faculty components replaced as may be found necessary. A complete record ofsuch attention and running time of components changed shall be kept.

Test Procedure:

(1)Engine adjustment:

The distributor, carburettor or the fuel pump rack, as the case may be set as its nominal

specified value at idling in contrast to its manual adjustments for maximum power at each

speed.

(2) Temperature:

The temperature of the inlet air shall be measured at the entrance of the induction system.

(3) Number of Runs:

In every test, a sufficient number of runs shall be made throughout the speed range. A run

shall be made at the lowest steady at which the engine operates.

(4) Duration of Runs:

Performance data shall be obtained under stabilized operating conditions. Durations of the

experimental run depends upon two principles:(i) No data shall be taken until load, speed and temperature have been stabilized.


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(ii) Recorded data shall be average sustained values maintained over a period of at least one

minute, with no significant change occurring during that time.

(5) Power Test:

For all power tests with results to be plotted versus speed, a single series of stabilized runs atascending speeds is sufficient. This series of runs should progress continuously, from the

lowest to the maximum. If the engine requires to be idled between runs to avoid excessively

high temperature, sufficient time should for the engine to reach its stabilized condition before

taking readings. The brake load recorded should be steady and constant throughout the run.

(6) Engine Speed:

Engine speed should be held constant as possible by means of applied dynamometer load at

wide open throttle or by throttle adjustment at part load.

(7) Friction Power:

The friction power test shall, if possible, follow immediately after the power test. If this is not

possible, the test shall be conducted under condition similar to those for the power test.

(8) Fuel Consumption:

Fuel consumption shall be measured simultaneously with brake power. The fuel consumption

measurement shall not be started un-till the engine is stabilized.

Observations:

(1)Brake Power is given by:

where,

W is the load applied in N

S is the spring scale reading in N

and N is the rpm

(2)Mechanical Efficiency is given by:

(3)Indicated Power is given by:

IP = Brake Power + Frictional Power

(4) Specific Fuel Consumption:


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Specific fuel consumption shall be computed on the basis of gm of fuel per observed brake

power hour.

(5) Five Hundred Hour Endurance Test:

After completion of the performance test, the engine shall be run for 500 hours at rated speed

in cycles of 16 hours continuous running each cycle being made as follows:

At the end of 16 hour cycle, the engine shall be stopped and necessary servicing and minor

adjustments may be carried out in accordance with the maker's schedule. Before starting the

next cycle, the engine shall have reached very nearly the room temperature. One litre sample

of the oil drained during each oil change and one litre sample of the fuel used shall be sent to

the laboratory for analysis.

(6)Recheck of Power and Fuel Consumption:

The power fuel consumption shall be determined by repeating the performance test.

(7)Final Inspection:

At the conclusion of the test, the engine shall be stripped, its condition noted and the

dimensions of the main working parts checked and recorded.

4) Explain any one method of finding brake power.

Determination of Brake Power using rope brake Dynamometer is explained below. A

Rope Brake Dynamometer is shown in Fig:


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Rope Brake Dynamometer

It consists of a number of turns of rope wound around the rotating drum attached to the

output shaft. One side of the rope is connected to a spring balance and other to a loading

device. The BP is given by,

Where,D= Brake drum diameter

W= Weight

S = Spring scale reading

The power is absorbed is due to friction between rope and the drum. If the power produced is

very high, some heat is also produces due to friction. To avoid the thermal effects of between

wheel and rope, some cooling arrangement is necessary. Generally owing water is used as

cooling medium. Rope brake is quiet cheaper and can be easily fabricated, but not very

accurate because of changes in the friction coefficient of the rope with temperature.

5) How to measure the quantity of air supplied to an I.C. engine?The orifice plate can be used to measure the air flow rate. The pressure pulsations into the

engine are reduced by fitting an air tank. The set-up is shown in Fig:


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Measurement of Mass of air using orifice plate

Mass flow through orifice plate is obtained using the formula:

Where,

Cd is the coefficient of Discharge

A is area of the cross section

g is the acceleration due to gravityhw is the height of water column

w, a are density of water and air respectively.

How do you find the IP of a multi-cylinder I.C. engine without using anindicator?

IP of a multi-cylinder engine can be calculated by finding the brake power (by

Dynamometer) and frictional power (by Morse Test) individually and summing them

together.

IP = Brake Power + Frictional Power

6) What do you mean by relative efficiency of an engine? Explain how it isexpressed?

Relative efficiency is the ratio of actual thermal efficiency to the theoretical thermal

efficiency of an IC Engine. It is denoted by rel. It is expressed as:


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7) Distinguish between IP and BP, which is greater?

The power available in the cylinder is called Indicated power IP and the power available in

the shaft to do useful mechanical work is called brake power. The power available at the

crank shaft is always less than the IP due to friction. Hence IP is always greater than BP.

8) What for a Morse test is conducted?

Morse Test is the method of determining indicated power (IP) of each cylinder individually,

of a multi cylinder IC engine, without the use of an indicator and thus computing the `total IP

of the engine' by summing up IP of all the cylinders. This method is adopted to calculate IP

of high speed engines, i.e. where the indicator method is unsuitable. Also it can be used to

obtain the frictional power of the multi cylinder engine.

9) You are doing a preliminary design study of a turbocharged four stroke

diesel engine. The maximum rated power is limited by stress considerationsto a brake mean effective pressure of 1200 kPa and maximum value of mean

piston speed of 12 m/s.

(a) Derive an equation relating the engine inlet pressure to the fuel/air ratio at this maximum

rated power operating point.

For a four stroke engine we have:

Where,

P is the power output of the engine. fis the fuel conversion efficiency.

v is the volumetric efficiency.

Qhv is Calorific Value of the fuel.

N is the speed of the engine.

Vd is the displacement volume.

ai is the air density at the inlet.

F/A is the fuel-air ratio.

Also using Ideal Gas Equation we know,

Where,

Pai.is the pressure at the inlet

Tai.is the temperature at the inlet and also


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Cancelling common terms in the 3 equations and relating them gives:

(b) The maximum rated brake power requirement for this engine is 400 kW. Estimate

sensible values for number of cylinders, cylinder bore, stroke, and determine the maximum

rated speed of this preliminary engine design.

Assume the engine has 12 cylinders. Then we know

Where,

S is the mean piston speed in m/s

L is the stroke length in m

Assuming square engine (L=D), substituting S=12 m/s, P=400 kW, mep= 1200 kPa and using

(6) in (5), we get

L=D=108.5mm

Rated speed = 3333 rpm

(c) If the pressure ratio across the compressor is 2, estimate the overall fuel/air ratio at

maximum rated power. Assume appropriate values for unknown parameters.

Assume f=0.3, v=0.9, Patm= 103 kPa, Tatm= 298 K, n=1.4

Since pressure ratio across the compressor is 2, Pai=206 kPa, R=289 J/kgK

Assuming adiabatic compression in the compressor, Tai =363 K.

Using equation (4), substituting all values and solving, we get F/A=0.051 i.e A/F= 19.6.

Documents

10M134 AIC Assignment 1 & 2.pdf