Mechanical Engineering MCQs

Page No. 55

According to Recardo’s theory, detonation occurs due to______________________?


ainstantaneous auto-ignition of last part of charge to be burnt

✓


bimproper mixing of air and fuel

✖


cimproper combustion

✖


dself ignition temperature has nothing to do with detonation

✖



The knocking in diesel engines for given fuel, will be__________________?


aenhanced by increasing compression ratio

✖


benhanced by decreasing compression ratio

✓


cunaflected by compression ratio

✖


dfirst enhanced by increasig compression ratio upto a limit beyond which it will be suppressed

✖



Injection lag is_________________?


athe time taken by fuel after injection (before top dead center) to reach upto auto-ignition temperature

✖


btime before actual fuel injection and the pump pluger starts to pump fuel

✓


ctime corresponding to actual injection and top dead center

✖


dtime corresponding to actual ignition and top dead center

✖



Carbon residue in diesel oil should not be more than___________________?


a1%

✖


b0.5%

✖


c0.1%

✖


d0.001%

✓


View Answer 0.001%

Diesel engines have low specific fuel consumption compared to petrol engine. This statement is____________________?


anot true

✖


btrue at full load

✖


ctrue at part load

✖


dtrue at both part and full load

✓



In order to prevent knock in the S.I. engines, the charge away from the spark plug should have___________________?


alow temperature

✖


blow density

✖


clong ignition delay

✖


dall of the above

✓


View Answer all of the above

To reduce the possibility of knock in the C.I. engines, the first elements of fuel and air should have_______________?


ahigh temperature

✖


bhigh density

✖


cshort delay

✖


dall of the above

✓


View Answer all of the above

Piston rings are plated with chromium,cadmium or phosphate in order to__________________?


areduce cost

✖


bimprove surface finish

✖


cprevent clogging

✖


dreduce wear and eliminate scuffing

✓



The pistons are usually given a coating such as tin plating in order to________________?


areduce weight

✖


bconduct heat efficiently

✖


creduce possibility of scoring

✓


dreduce friction

✖



If overhead clearance is less, then the following type of engine should be selected__________________?


aV-type

✖


bIn-line

✖


cVertical

✖


dHorizontal

✓


View Answer Horizontal

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