i c Engine Question Bank

DEPARTMENT OF MECHANICAL ENGINNERING MAHARAJA INSTITUTE OF TECHNOLOGY MYSORE INTERNAL COMBUSTION ENGINES-06ME763  Faculty-Dr. Y.T.KRISHNEGOWDA

Frequently asked questions: UNIT-1: THERMODYNAMIC CYCLE ANALYSIS  1. With the help of P-V diagram explain how the variation in specific heats and dissociation of gases of gases tend

to deviate the ideal processes? 2. How the variation of specific heats takes' with temperature? What' are the physical Explanations for

variation of specific heats? 3. Explain the effect of fuel-air ratio on, i) Efficiency. ii) Maximum power. iii) Maximum temperature. iv)

Maximum pressure v) Exhaust temperature. 4 What are combustion charts? Where theses are used and why? 5. What is the effect of percentage change in the efficiency of Otto cycle having a compression ratio of 

7, if the specific heat at constant volume increases by 1 % 6. In an oil engine, working on dual combustion cycle the temperature and pressure at the beginning of 

compression, are 90°C and 1 bar. The compression ratio is 13:1. The heat supplied per kg of air is 1672 KJ, half of which is supplied at constant volume and half at constant pressure. Calculate i) the maximum pressure in the cycle, and ii) the percentage of stroke at which cut off occur. Take r for compression 1.4; Cv for products of combustion, 0.71+18.81 *10-5 T and R = O.287kJ/kgK. 7.

The air fuel ratio of a Diesel engine is 29: 1. If the compression ratio is 16: 1 and the temperature at

the end of compression is 900 K, find at what cylinder volume the combustion is complete. Express this volume as percentage of stroke. Assume that the combustion begins at the top dead center and takes place at constant pressure. Take calorific value of the fuel as 42 mJ/kg, R= 0.287 kJ/kgK  and Cv = 0.709 +O.000028T kJ/kgK.

8.

A petrol engine having a compression ratio of 6 uses a fuel with a calorific value of 42 MJ/kg. The air-

fuel ratio is 15:1 Pressure and temperature at the start of suction stroke are1 bar and

5TC  respectively.

Determine the maximum pressure in the cylinder if the index of compression is 1.3 and the specific heat at constant volume is given by Cv=0.678+ 0.00013T, where T is in Kelvin. Compare this value with that obtained when Cv =0.717 kJ/kgK.

UNIT-2: CARBURATION AND COMBUSTION PROCESS IN SI  ENGINES  1. With a neat pressure crank angle diagram, explain the stages of combustion in SI engine. 2. Explain the effect of following engine variables on ignition lag: .i) Mixture ratio ii) Initial temperature. iii) Electrode gap. 3. Give any four good requirements of anti knock additives. 4. Explain the phenomenon of 'Knocking' in SI engines with suitable sketches. 5. Discuss'. The effect of the following parameters on the name propagation of SI engines: i) A:F ratio ii) Compression ratio iii) RPM of the engine iv) Engine load v) Turbulence. 6. What are the factors that limit the compression ratio in Petrol engine? 7. Explain the difference between: i) Pre-ignition ii) Ant ignition iii) Detonation. 8, Describe the phenomenon, of knocking in SI engine. Explain four main factors which affect the tendency to knock.

UNIT-3: COMBUSTION IN CI ENGINES  1. What are two basic differences in the combustion process of SI and CI engines? 2. With the help of pressure-crank angle diagram, explain the stages of combustion in CI engines. 3. How does the detonation in SI engine differ from diesel knock? Explain. 4. Explain briefly the following:

i) Delay period in CI engine combustion. ii) Cetane number.

5. Compare 'Knocking' in SI and CI engines with reference to following engine variables.

i.

Compression ratio

ii Self-ignition temperature of fuel.

iii. Delay period for fuel. iv. Inlet temperature v. Inlet Pressure. 6. What is meant by delay period? Explain the effect of the following factors on delay period:

i) Fuel properties ii) Intake temperature iii) Compression ratio iv) Engine speed v) Type of  combustion chamber vi) Engine speed. 7.

a. What do you mean by Knock rating of Diesel fuel? b. Explain the effect following engine variables on delay period:

i) Compression ratio. ii) Quality of the fuel.iii) Injection pressure. iv) Engine speed. v) Intake temperature. c. Explain the phenomenon of knock in CI e ngines. 8

a. Discuss any three important variables that affect t he delay period in combustion. b. Explain how diesel engine knock differs from S.I engine knock. c. What is knock rating of diesel fuel?

UNIT-4: COMBUSTION CHAMBERS  1.a. Explain briefly at least ten SI engine combustion chamber design principles b. Give the classification of Cl engine combustion chamber. c. With simple sketch explain air-cell chamber type divided combustion chamber. 2.a. How C.I. engine combustion chambers are classified? What type of swir l are used in these chambers b. What are the advantages of overhead valve combustion chambers over side valve combustion-

chambers? Give neat sketches of both. 3a. Explain the basic requirements of a good Sl engine combustion chamber. b. Sketch and explain Ricardo turbulent combustion chamber c. Give any two advantages of induction swirl. Sketch and explain Ricardo swirl chamber.

4 a. Draw neat layout of I and F head combustion chambers. Discuss their advantages and disadvantages. b. What are the requirements of CI combustion chamber for Diesel engines? Explain why weak mixtures give less efficiency in CI Engines 5 a. What are F-head combustion chambers? Sketch a ny two F-head designs. b. What are the advantages and disadvantages of compression-induced swirl? c. What is' M-combustion chamber?

UNIT-5:

F UELS 

1.a. Write a brief note on the following:

i) Influence of chemical structure on knock. ii), Alternate fuels. b. Sketch and explain the working of carter (constant choke) carburetor. 2 a. How SI ENGINE fuels are rated? b. Write a short note on the air fuel ratio requirements of a petrol engine from no load to full load.. C. Sketch and explain solex carburetor. 3.a. Explain the reasons for looking for alternate fuels for IC engines. b. Explain alcohols as alternate fuels for IC engines bring out their merits and demerits. c. With a neat sketch explain the working principle of a SU carburetor. 4.a. What are the four main constituents of crude petroleum? Explain any three constituents giving

general formula, chemical structure. Also mention whether they are saturated or unsaturated compounds. b. Explain the SI-engine air fuel requirements under following conditions: i) Idling

, ii) Cruising. iii) High

power range. c. Draw the neat sketch of a simple carburetor. 5 a. Discuss the importance of: i) Gum content. ii) Heat of combustion iii) Sulphur content for a diesel

fuel b. Write short note on mixture strength re quirements of a petrol engine from no load to full load. c. Briefly explain with a neat sketch the operation of a simple float type carburetor

UNIT-6: F UEL INJECT ION

SYST EMS

1. a. What are the functional elements required for accomplishing the objectives of diesel engine fuel injection system? Also mention the location of these elements with the help of symbolic representation explain i) Individual pump and injector type. ii) Common rail type b. Explain the following with simple sketches i) Thermostat ii) Radiator 2 a. Discuss five important requirements of an ideal diesel injection system. b. Draw a sketch of Pintaux nozzle and discuss its merits. c. Name different methods used for circulating the w ater around the cylinder and cylinder head. 3 a. How are injection systems Classified ? Describe them briefly. What are the limitations of air injection system? b. Draw a typical heat balance sheet of IC engine. c. Why overheating and over cooling of IC engines is harmful? 4. a. With a neat sketch explain the Jerk pump injection system. b. With a neat sketch explain :i) Forced circulation-cooling system. ii) Evaporative cooling system. 5. a. Describe with suitable sketches common rail system and distributor injection. b. Draw a sketch of Pintaux nozzle and discuss its merits. c. What is the function of a radiator? Explain the construction of a typical radiator system of fuel .

UNIT-7: MODER N DEVOLOPMENT S 1. Write short notes on the following: a. Turbo charging. b. Super charging c.Stratified charge engine. d. Multi fuel engine. 2. a. What is supercharging and what is its effect on the following parameters: (i) Power output (ii) Mechanical efficiency (iii) Fuel consumption b. What are the advantages of dual-fuel engines? 3. a. Explain with neat sketches various types super changing arrangements. b. Explain. Stratified charge engines and give their classification. c. State the advantages and disadvantages of stratified charge engines.

4.a. What is meant by charge stratification? What are the advantages of burning leaner overall fuel-air

mixture? With a neat sketch explain Volkswagen PCI stratified charge engine: b. What is meant by multi fuel engine? What arc the requirements of multi fuel engines?

c. Explain the effect of supercharging on the following parameter i) Power output. ii) Mechanical efficiency. 5.a. What are the modifications required for supercharging? b. Discuss the general characteristics of stratified charge engines. c. What are the advantages and disadvantages of rotary combustion Engine compared to reciprocating

engine

UNIT-8: EMMISSION

R EGULAT OR S AND CONTR OL SYST EMS

1. a. What are the sources of pollutants in petrol engines? b. Explain how NOx emissions are controlled by exhaust gas recirculation. c. "A catalytic converter package is a total emission control package". Explain. 2. a. What are the main constituents of exhaust emission from Petrol-engine? Plot their nature and variation with respect to air: fuel ratio. b. What is the mechanism of smoke formation and how it is controlled? 3. Write short notes on the following: a) Sources of pollutants from IC engines b) Effects of engine emissions on human health c) Thermal: reactor package d) SI engine emission control. 4. a. Explain the mechanism of formation of N02 in petrol engine. With a suitable sketch explain the

control of N02 by Exhaust Gas Recirculation (EGR) method. b. With a suitable diagram explain the following emission control systems:

i) Thermal reactor

package. ii) Catalytic converter package. 5 a. Describe the exhaust gas recirculation method for the control of nitrogen oxides (NOx). b. Describe with sketches: i) After burners ii) Catalytic converter system

KISHAN.G.S. 7 TH  SEM MECHANICAL ENGG  MIT, MYSORE