单项选择题A mixture of 45%cetane and 55% alpha-methyl-naphthalene is found to have the same ignition delay as a sample of diesel oil √The sample can be described as having a/an()

A.cetane number of 55
B.cetane number of 45
C.octane number of 55
D.octane number of 45


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1.单项选择题Worn main bearing will cause the compression ratio of an auxiliary diesel engine to()

A.increase
B.decrease
C.remain the same
D.increase on compression decrease on expansion

2.单项选择题With respect to diesel fuel, the ease with which a cold engine will start is dependent upon the()

A.ignition quality of the fuel
B.high heating value of the fuel
C.amount of carbon residue after combustion
D.internal flow resistance in the injectors

3.单项选择题A two-stroke/cycle diesel engine requires less starting air than a four-stroke/cycle diesel engine, of equal displacement, because the two-stroke/cycle diesel engine()

A.has little or no internal friction
B.has a lower effective compression ratio
C.operates with scavenge air under a positive pressure
D.operates without energy absorbing intake and exhaust strokes

4.单项选择题Which of the following operating conditions can occur when shims are removed from the joint between the foot of a marine type diesel engine connecting rod and the bearing box?()

A.Decreased connecting rod bearing clearance
B.Increased connecting rod bearing clearance
C.Decreased compression ratio
D.Increased compression ratio

5.单项选择题The longer the ignition delay period resulting from improper use of low cetane fuel, the ()

A.less fuel will enter the cylinder
B.higher the cylinder combustion temperature
C.more complete the fuel combustion
D.more rapid the rise in combustion pressure

6.单项选择题Intercoolers installed on starting air compressors, reduce the possibility of()

A.dust entering the high pressure stage
B.lube oil carbonization
C.discharge pulsations
D.inter-stage vapor lock

7.单项选择题The insertion of shims between the foot of a marine type connecting rod and a bearing box would result in ()

A.increased compression ratio
B.decreased compression ratio
C.increased bearing clearance
D.decreased bearing clearance

8.单项选择题Which of the following statements is true concerning the cetane number rating of diesel fuel? ()

A.The cetane number is obtained by comparing the fuel with cetane a colorless liquid hydrocarbon
B.The higher the cetane number, the shorter the ignition lag
C.The highest cetane number of fuel is 100
D.All of the above

9.单项选择题Which of the following statements is true concerning the cetane number of diesel fuel?()

A.The cetane number affects the amount of injection lag
B.The cetane number is an indication of the fuels viscosity
C.Ignition lag is reduced with fuels having a high cetane number
D.The cetane number is of little significance in the combustion process

10.单项选择题Fuel oil having a low cetane rating could result in()

A.improved cold weather starting
B.excessive fuel oil consumption
C.reduced ignition lag
D.smoother engine operation