11. The brake power of a diesel engine, keeping other parameters constant, can be increased by
A. decreasing the density of intake air
B. increasing the temperature of intake air
C. increasing the pressure of intake air
D. decreasing the pressure of intake air
12. In diesel engines, the fuel is injected in the form of very fine spray, into the engine cylinder, which gets ignited due to high temperature of the compressed air.
A. Agree
B. Disagree
13. Pre-ignition is caused by the spontaneous combustion of the mixture before the end of the compression stroke and is due to
A. cylinder walls being too hot
B. overheated spark plug points
C. red hot carbon deposits on cylinder walls
D. any one of these
14. The expansion of fuel in a four stroke cycle diesel engine
A. starts at 15° before top dead center and ends at 30° after top dead center
B. starts at top dead center and ends at 30° after top dead center
C. starts at 15° after top dead center and ends at 30° before bottom dead center
D. may start and end anywhere
15. The object of supercharging engine is
A. to reduce the mass of the engine per brake power
B. to reduce space occupied by the engine
C. to increase the power output of an engine when greater power is required
D. all of the above
16. In the open combustion chamber in diesel engines, the shape and layout of the piston crown, the inlet port and the valve produce the turbulent effect of fuel mixture.
A. True
B. False
17. In a four stroke cycle petrol engine, the charge is ignited at
A. 30° before top dead center
B. 30° after top dead center
C. 30° before bottom dead center
D. 30° after bottom dead center
18. A moderator, in nuclear power plants, is a medium introduced into the fuel mass in order to
A. slow down the speed of fast moving neutrons
B. control the reaction
C. reduce the temperature
D. extract heat from nuclear reaction
19. Where reactor operation is designed with fast neutrons such as in reactors using highly enriched fuel, the moderator used is
A. heavy water
B. graphite
C. carbon dioxide
D. no moderator is needed
20. In a diesel engine, the duration between the time of injection and ignition is known as
A. pre-ignition period
B. delay period
C. period of ignition
D. burning period
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