Mechanical Engineering Mcqs
Auto-ignition temperature is____________________?

A. Minimum temperature to which 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. That at which it catches fire without external aid
D. Indicated by 90% distillation temperature, i.e., when 90% of sample oil has distilled off

Octane number is determined by comparing the performance of the petrol with the following hydrocarbons__________________?

A. Iso-octane
B. Mixture of normal heptane and iso-oc-tane
C. Alpha methyl napthalene
D. Mixture of methane and ethane

Ethyl fluid is used_______________________?

A. To increase the octane rating of the fuel
B. To increase the cetane rating of the fuel
C. As a defrosting agent
D. As a superior type of fluid compared to others

Normal heptane_______________?

A. Accelerates auto-ignition
B. Helps to resist auto-ignition
C. Does not affect auto-ignition
D. Has no relation with auto-ighition

Which is correct statement about reaction time for autoignition of fuel and the fuel air ratio__________________?

A. Lean mixture has high reaction time
B. Rich mixture has high reaction time
C. Chemically correct mixture has mini-mum reaction time
D. All of the above

Ignition lag is__________________?

A. The time taken by fuel after injection (before top dead center) to reach upto auto-ignition temperature
B. Time before actual fuel injection and the pump plunger starts to pump fuel
C. Time corresponding to actual injection and top dead center
D. Time corresopnding to actual ingition and top dead center

Cetane number is determined by comparing the performance of diesel oil with the following hydrocarbons___________________?

A. Cetane
B. Mixture of cetane and alphamethyl napthalene
C. Ethylene dibromide
D. Mixture of aldehydes and ketones

Violent sound pulsations within the cylinder of an I.C. engine are caused due to_________________?

A. Heavy turbulence
B. Improved scavenging
C. Heavy supercharging
D. Detonation