solution for internal combustion engines · 2020-01-28 · solution for internal combustion engines...

Mumbai University Mechanical (Semester -V)

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Solution for Internal Combustion Engines

December 2015

Index

Q.1)

a) …………………………………………………………………………. 2

b) …………………………………………………………………………. 3

c) …………………………………………………………………………. 4

d) …………………………………………………………………………. N.A

e) ………………………………………………………………………… 4-5

d) ………………………………………………………………………… 6 -7

Q.2)

a) …………………………………………………………………………. 7-8

b) …………………………………………………………………………. 8-10

Q.3)

a) …………………………………………………………………………. 10-11

b) …………………………………………………………………………. 12-13

Q.4)

a) …………………………………………………………………………. 13

b) …………………………………………………………………………. 14

Q.5)

a) …………………………………………………………………………. 15-16

b) ………………………………………………………………………….17-18

Q.6)

a) ………………………………………………………………………….19-20

b) ………………………………………………………………………….20-21

c) ………………………………………………………………………….22-24

d) ………………………………………………………………………….24-25

e) ………………………………………………………………………….. 25-26



Q1)ATTEMPT ANY FIVE OF THE FOLLOWING

(a) Compare abnormal combustion in SI and CI engines

Ans:



b) Sketch and explain actual port timing diagram for two stroke engine



c) Give the reasons for black,blue and white colored smoke from exhaust of

diesel engines.

Ans:

d) Explain the effects of spark advancement and retardation on the engine

performance.

Ans: N.A

e) Explain why turbo charged engine may have inferior values of power output

and fuel consumption than naturally aspirated engines especially a low speed.

Ans: Power output



Fuel Consumption:



f) What are the components (at least four) of general diesel fuel injection

system? State in brief function of each of them.

Ans:



Q2)

(a) Describe the requirements for spark plug.

AnS:



(b) During test on a diesel engine the power developed by the engine is used for

driving a DC generator with output of 210 ampere at 200volt .The

effieciency of generator is 82% .The fuel of 42600kj/kg calorific value is

supplied to the engine at 11.2 kg/hr.The air fuel ratio was 18: 1.The exhaust

gases were passed through a exhaust gas calorimeter for which the

observation were as follows:

Water circulated through at 580 l/hr ,temperature rise of water through

calorimeter is equal to 36 0 C.Temperature of exhaust gas at exit from

calorimeter is 980 .C .Ambient temperature is 200 . C .Heat lost to jacket cooling

water is 32% of the total heat supplied :If the specific heat,of exhaust gases be

1.05 kJ/kgK,draw up the heat balance sheet on minute basis.



Ans:



Q3)

(a) With neat sketch explain various types of fuels nozzles used in CI

engine system.

Ans:



2 Multiple Hole Type : Proper mixing with air 4 to 18 holes .Size of the

holes will be 0.35 to 1.5 mm



(b)A perfect gas at 1 bar and 290 K undergoes ideal diesel cycle. The

maximum pressure of the cycle is 50bar .The volume at the beginning of

compression is 1 m3 and after constant pressure heating is 0.1 m3 .Determine

the temperature at all sallent point of the cycle and also find out the efficiency

of the cycle .Take v=1.4 for the gas.

Ans:



Q4) a) Compare air and water cooling systems.

Ans:



(b) A closed type injector has a nozzle orifice diameter of 0.9 mm and

maximum cress sectional area of passage between needle cone and the seat is

1.75 mm2.Coefficient od discharge for the orifice is 0.85 and for the pressure of

0.8.The injection pressure is 175 bar and the average pressure of change during

injection is 25 bar ,when the needle cone is fully lifted up.Calculate the volume

rate of flow per second of fuel through the injector and the velocity of jet at that

instant .Take density of fuel equal to 850kg/m3 .

Ans:



Q5)

(a) Explain in detail the various stages of combustion in S.I .engine.

Ans:

Given below are the Stages of combustion in SI engine.



Following are the stages of combustion in S.I engine

1) Ignition delay /Ignition lag

2) Second phase (Spreading of Flame)

3) After Burning.



(b) What is turbo charging ? Describe in brief the methods of turbo charging.

Ans:



Q6) Write short note(any 4)

(a) Effect of dissociation phenomenon on PV diagram of turbo charging.

Ans:



Effect of Dissociation on Temperature at different Mixture strength



(b) Control of NOx emission.

Ans:



(c) Alternate fuels in I.C engine.

Ans:

For C.I engines alternative fuels are:

a) CNG

b) Methanol-Diesel fuel blends

c) Vegetable oils: Karanji oil ,sunflower oil etc.

a)CNG:



b) Methanol:

Methyl alcohol or wood alcohol CH3OH , a colourless ,flammable liquid

that is miscible with water in all proportions.

Methanol is a monohydric alcohol.

It melts at -97.80 C and boils at 670 C.

It reacts with certain acids to form methyl esters .Methanol is a fatal

poison.

Small internal doses, continued inhalation of the vapour ,or prolonged

exposure of the skin to the liquid cause blindness.

As a result, commercial use of methanol has sometimes been prohibited

.Methanol is used as a solvent for varnishes and lacquers ,as an antifreeze

,and as a gasoline extender in the production of gasohole.

Large amount of it are used in the synthesis of formaldehyde. Because of

its poisonous properties ,methanol is also used as a denaturant for

ethanol.



Vegetable oil:

d) Stages of combustion in CI engine.

Ans:

(1) First stage (Ignition Delay ): It is temporary phase.It is the



e) Exhaust gas recirculation.

Ans:

solution for internal combustion engines · 2020-01-28 · solution for internal combustion engines...

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