McqMate
Chapters
| 1. |
A perfect engine works on the Carnot cycle between 727 °C and 227°C. The efficiency of the engine is |
| A. | 0.5 |
| B. | 0.75 |
| C. | 1 |
| D. | 0.25 |
| Answer» A. 0.5 | |
| 2. |
The air standard Otto cycle consists of |
| A. | two constant volume and two isentropic processes |
| B. | two constant pressure and two isentropic processes |
| C. | two constant pressure and two constant volume processes |
| D. | none of the above |
| Answer» A. two constant volume and two isentropic processes | |
| 3. |
In air standard Diesel cycle at fixed r and fixed n |
| A. | ƞthermal increases with increase in heat addition and cut-off ratio |
| B. | ƞthermal decreases with increase in heat addition and cut-off ratio |
| C. | ƞthermal Remains the same with increase in heat addition and cut-off ratio |
| D. | none of the above |
| Answer» B. ƞthermal decreases with increase in heat addition and cut-off ratio | |
| 4. |
Mean effective pressure of Otto cycle is |
| A. | inversely proportional to pressure ratio |
| B. | directly proportional to pressure ratio |
| C. | does not depend on pressure ratio |
| D. | proportional to square root of pressure ratio |
| Answer» B. directly proportional to pressure ratio | |
| 5. |
For a given compression ratio the work output of Otto cycle is |
| A. | increases with Increase in r |
| B. | decreases with increase in r |
| C. | is not affected |
| D. | none of the above |
| Answer» A. increases with Increase in r | |
| 6. |
For a given value of r, efficiency of Otto cycle |
| A. | decreases with compression ratio |
| B. | increases with compression ratio |
| C. | is not affected |
| D. | none of the above |
| Answer» B. increases with compression ratio | |
| 7. |
For dual combustion cycle for fixed value of heat addition and compression ratio |
| A. | mep wil be greater with increase in rp, and decrease in rc |
| B. | mep will be greater with decrease in rp and decrease in rc |
| C. | mep remain the same with increase in rp and decrease in rc |
| D. | none of the above |
| Answer» A. mep wil be greater with increase in rp, and decrease in rc | |
| 8. |
The normal range of, compression ratio for Otto cycle is |
| A. | 6 to 10 |
| B. | 2 to 4 |
| C. | >10 |
| D. | none of the above |
| Answer» A. 6 to 10 | |
| 9. |
The normal range of compression ratio for Diesel cycle is |
| A. | 4 to 6 |
| B. | 6 to 8 |
| C. | 15 to 20 |
| D. | >25 |
| Answer» C. 15 to 20 | |
| 10. |
For the same compression ratio and heat addition |
| A. | ƞOtto > ƞDiesel > ƞDual |
| B. | ƞDiesel > ƞOtto > ƞDual |
| C. | ƞOtto> ƞDual > ƞDiesel |
| D. | ƞDual> ƞDiesel > ƞOtto |
| Answer» C. ƞOtto> ƞDual > ƞDiesel | |
| 11. |
for the same compression ratio and heat rejection, |
| A. | ƞOtto> ƞDual > ƞDiesel |
| B. | ƞDiesel > ƞDual > ƞOtto |
| C. | ƞDual> ƞDiesel > ƞOtto |
| D. | ƞDual> ƞOtto> ƞDiesel |
| Answer» A. ƞOtto> ƞDual > ƞDiesel | |
| 12. |
When the engines are built to withstand the sane thermal and mechanical stresses |
| A. | ƞDiesel > ƞDual > ƞOtto |
| B. | ƞDual> ƞDiesel > ƞOtto |
| C. | ƞOtto> ƞDual > ƞDiesel |
| D. | ƞOtto> ƞDiesel > ƞDual |
| Answer» A. ƞDiesel > ƞDual > ƞOtto | |
| 13. |
For the same peak pressure and heat input |
| A. | ƞOtto > ƞDual > ƞDiesel |
| B. | ƞOtto > ƞDiesel > ƞDual |
| C. | ƞDiesel > ƞDual > ƞOtto |
| D. | ƞDiesel > ƞOtto > ƞDual |
| Answer» C. ƞDiesel > ƞDual > ƞOtto | |
| 14. |
For the same peak pressure and work output |
| A. | ƞOtto > ƞDual > ƞDiesel |
| B. | ƞOtto > ƞDiesel > ƞDual |
| C. | ƞDiesel > ƞOtto > ƞDual |
| D. | ƞDiesel > ƞDual > ƞOtto |
| Answer» D. ƞDiesel > ƞDual > ƞOtto | |
| 15. |
Brayton cycle is used in |
| A. | Ramjet engines |
| B. | gas turbines |
| C. | pulse jet engines |
| D. | Cl engines |
| Answer» B. gas turbines | |
| 16. |
The actual efficiency of a good engine is about _______of the estimated fuel-air cycle efficiency. |
| A. | 100% |
| B. | 85% |
| C. | 50% |
| D. | 25% |
| Answer» B. 85% | |
| 17. |
With dissociation peak temperature is obtained |
| A. | at the stoichiometric air-fuel ratio |
| B. | when the mixture is slightly lean |
| C. | when the mixture is slightly rich |
| D. | none of the above |
| Answer» C. when the mixture is slightly rich | |
| 18. |
With dissociation the exhaust gas temperature |
| A. | decreases |
| B. | increases |
| C. | no effect |
| D. | increases upto certain air-fuel ratio and then decreases |
| Answer» A. decreases | |
| 19. |
Fuel-air ratio affects maximum power output of the engine due to |
| A. | higher specific heats |
| B. | chemical equilibrium losses |
| C. | both (a) and (b) |
| D. | none of the above |
| Answer» C. both (a) and (b) | |
| 20. |
Mean effective pressure at a given compression ratio is maximum when the air-fuel ratio is |
| A. | higher than stoichiometric |
| B. | lower than stoichiometric |
| C. | equal to stoichionetric |
| D. | none of the above |
| Answer» B. lower than stoichiometric | |
| 21. |
For a compressor process with variable specific heat the peak temperature and pressure are _______compared to constant specific heat |
| A. | lower |
| B. | higher |
| C. | no effect |
| D. | none of the above |
| Answer» A. lower | |
| 22. |
Dissociation can be considered as |
| A. | disintegration of combustion products at high temperature |
| B. | reverse process of combustion |
| C. | heat absorption process |
| D. | all of the above |
| Answer» D. all of the above | |
| 23. |
Time loss factor in actual cycle is due to |
| A. | Progressive combustion |
| B. | heat loss through cylinder walls |
| C. | gas leakage |
| D. | friction |
| Answer» A. Progressive combustion | |
| 24. |
The major loss in a SI engine is due to |
| A. | exhaust blow down |
| B. | pumping |
| C. | incomplete combustion |
| D. | variation in specific heat and chemical equilibrium |
| Answer» D. variation in specific heat and chemical equilibrium | |
| 25. |
Fuel-air cycle efficiency is less than air-standard cycle efficiency by an amount equal to |
| A. | pumping loss |
| B. | friction loss |
| C. | loss due to specific heat variation and chemical equilibrium |
| D. | exhaust blow down loss |
| Answer» C. loss due to specific heat variation and chemical equilibrium | |
| 26. |
The major loss in a CI engine is |
| A. | direct heat loss |
| B. | loss due to incomplete combustion |
| C. | rubbing friction loss |
| D. | pumping loss |
| Answer» B. loss due to incomplete combustion | |
| 27. |
The ratio of the actual efficiency and the fuel-air cycle efficiency for CI engines is about |
| A. | 0.2-0.3 |
| B. | 0.5-0.6 |
| C. | 1.0 |
| D. | 0.6-0.8 |
| Answer» D. 0.6-0.8 | |
| 28. |
In an actual SI engine the pumping loss with respect to speed |
| A. | decreases |
| B. | Increases |
| C. | remains constant |
| D. | nothing to do with speed |
| Answer» B. Increases | |
| 29. |
The volumetric efficiency is affected by |
| A. | the exhaust gas in the clearance volume |
| B. | the design of intake and exhaust valve |
| C. | valve timing |
| D. | all of the above |
| Answer» D. all of the above | |
| 30. |
The air standard efficiency of an Otto cycle compared to diesel cycle for the given compression ratio is |
| A. | same |
| B. | less |
| C. | more |
| D. | more or less depending on power rating |
| Answer» C. more | |
| 31. |
In a typical medium speed, 4-stroke cycle diesel engine |
| A. | fuel injection starts at 10° before to dead center and ends at 20° after tor dead center |
| B. | fuel injection starts at top dead center and ends at 20° after top dead center |
| C. | fuel injection starts at just before top dead center and ends just after top dead center |
| D. | may start and end anywhere |
| Answer» A. fuel injection starts at 10° before to dead center and ends at 20° after tor dead center | |
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