110 TOP Objective I.C. Engines - Mechanical Engineering Questions and Answers pdf

81.    The reason for supercharging in any engine is to
(a)    increase efficiency
(b)    increase power
(c)    reduce weight and bulk for a given out-put
(d)    effect fuel economy
(e)     none of the above.
Ans: c

82.    The operation of forcing additional air under pressure in the engine cylinder is known as
(a) scavenging   
(b) turbulence
(c) supercharging
(d) pre-ignition
(e) dissociation and carburretion of fuel.
Ans: c

83.    Supercharging is essential in
(a) diesel engines
(b) gas turbines
(c) petrol engines
(d) aircraft engines
(e) marine engines.
Ans: d

84.    The minimum cranking speed in case of petrol engine is about
(a)    half the operating speed
(b)    one-fourth of operating speed
(c)     250-300 rpm 
(d)     60-80 rpm  
(e)     10-20 rpm
Ans: d

85.    In a typical medium speed 4 stroke cycle diesel engine
(a)    exhaust valve opens at 35° before bot-tom dead center and closes at 20° after top dead center
(b)    exhaust valve opens at bottom dead center and closes at top dead center
(c)    exhaust valve opens just after bottom dead center and closes just before top dead center
(d)    may open and close anywhere
(e)    none of the above is true.
Ans: a

86.    Flash point of fuel oil is
(a)     minimum temperature to which1 oil is heated in order to give off inflammable vapours in sufficient quantity to ignite momentarily when brought in contact with a flame
(b)    temperature at which it solidifies or congeals
(c)    temperature at which it catches fire without external aid
(d)    indicated by 90% distillation temperature, i.e. when 90% of sample oil has distilled off
(e)    none of the above.
Ans: a

87.    The mean effective pressure obtained from engine indicator indicates the
(a)    maximum pressure developed
(b)    minimum pressure
(c)    instantaneous pressure at any instant
(d)    exhaust pressure
(e)    average pressure.
Ans: e

88.    For the same power developed in I.C. engines, the cheaper system is
(a)    naturally aspirated
(b)    supercharged
(c)    centrifugal pump
(d)    turbo charger
(e)     none of the above.
Ans: b

89.    Installation of supercharger on a four-cycle diesel engine can result in the following percentage increase in power
(a) upto 25%
(b) upto 35%
(c) upto 50%
(d) upto 75%
(e) upto 100%.
Ans: e

90.    Scavenging is usually done to increase
(a)    thermal efficiency
(b)    speed
(c)    power output
(d)    fuel consumption
(e)    all of the above.
Ans: c

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