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Mechanical Engineering Objective Questions { Internal Combustion Engines }

85. Diesel engine can work on very lean air fuel ratio of the order of 30: 1, A petrol engine can also work on such a lean ratio provided
A.It is properly designed
B.Best quality fuel is used
C.Can not work as it is impossible
D.Flywheel size is proper

86. A diesel engine has
A.1 valve
B.2 valves
C.3 valves
D.4 valves

87. A high flame speed is obtained in diesel engine when air fuel ratio is
A.Uniform throughout the mixture
B.Chemically correct mixture
C.About 3-5% rich mixture
D.About 10% 'rich mixture

88. The knock in diesel engine occurs due to
A.Instantaneous and rapid burning of the first part of the charge
B.Instantaneous auto ignition of last part of charge
C.Delayed burning of the first part of the charge
D.Reduction of delay period

89. The air-fuel ratio in petrol engines is controlled by
A.Controlling valve opening/closing

90. Volatility of diesel fuel oil is
A.Minimum temperature to which oil is heated in order to give off inflammable vapors in sufficient quantity to ignite momentarily when brought in contact with a flame
B.Temperature at which it solidifies or congeals
C.It catches fire without external aid
D.Indicated by 90% distillation temperature, i.e. when 90% of sample oil has distilled off

91. Which is more viscous lub oil
A.SEA 30
B.SAE 80
C.SAE 50
D.SAE 70

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