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

101.    A hmh 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
(e)    about 10% lean mixture.
Ans: d

102.    The knock in diesel engine occurs due to
(a)    instantaneous and rapid burning of the first part of the charge
(b)    instantaneous atuo iginition of last part of charge
(c)    delayed burning of the first part of the charge
(d)    reduction of delay period
(e)    all of the above.
Ans: a

103.    The air-fuel ratio in petrol engines-is controlled by
(a)    controlling valve opening/closing
(b)    governing 
(c)     injection
(d)     carburettion
(e)     scavenging and supercharging.
Ans: d

104.    Volatility of diesel fuel oil is
(a)    minimum temperature to which oil is heated in order to give off inflam¬mable vapours 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
(e)    temperature at which it flows easily.
Ans: d

105.    Which is more viscous lib oil
(a) SEA 30 
(b) SAE 40
(c) SAE 50 
(d) SAE 70
(e) SAE 80.
Ans: e

106.    In the opposed piston diesel engine, the combustion chamber is located
(a)     above the piston (/;) below the piston
(c)    between the pistons
(d)    any when
(e)    there is no such criterion.
Ans: c

107.    A stoichiometric air-fuel ratio is
(a)     chemically correct mixture
(b)    lean mixture
(c)    rich mixture for idling
(d)    rich mixture for over loads
(e)    the ratio used at full rated parameters.
Ans: a

108.    In a naturally aspirated diesel engine, the air is supplied by
(a)    a supercharger
(b)    a centrifugal blower
(c)    a vacuum chamber
(d)    an injection tube
(e)    forced chamber
Ans: c

109.    In loop scavenging, the top of the piston is
(a) flat 
(b) contoured
(c) slanted 
(d) depressed
(e) convex shaped.
Ans: b

110.    In the crankcase method of scavenging, the air pressure is produced by
(a)    supercharger
(b)    centrifugal pump
(c)    natural aspirator
(d)    movement of engine piston
(e)    reciprocating pump.
Ans: d

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