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Q1. A compressor mostly used for supercharging of I.C. engines is
(A) Radial flow compressor
(B) Axial flow compressor
(C) Roots blower
(D) Reciprocating compressor
Answer: (A) Radial flow compressor
Q2. When air is to be compressed at a high pressure, then it is advantageous to use
(A) Single stage compression
(B) Multistage compression without intercooling
(C) Multistage compression with intercooling
(D) None of these
Answer: (C) Multistage compression with intercooling
Q3. Volumetric efficiency of a compressor without clearance volume
(A) Increases with increase in compression ratio
(B) Decreases with increase in compression ratio
(C) Is not dependent upon compression ratio
(D) May increase/decrease depending on compressor capacity
Answer: (C) Is not dependent upon compression ratio
Q4. If p₁ is the pressure of air entering the L.P, cylinder and p₃ is the pressure of air leaving the H.P. cylinder, then the ratio of cylinder diameters for a single acting, two stage reciprocating compressor with complete intercooling is given by
(A) D₁/D₂ = (p₁ p₃)1/2
(B) D₁/D₂ = (p₁/p₃)1/4
(C) D₁/D₂ = (p₁ p₃)1/4
(D) D₁/D₂ = (p₃/p₁)1/4
Answer: (D) D₁/D₂ = (p₃/p₁)1/4
Q5. The performance of air compressor at high altitudes will be __ as compared to that at sea level.
(A) Same
(B) Lower
(C) Higher
(D) None of these
Answer: (B) Lower
Q6. Volumetric efficiency is
(A) The ratio of stroke volume to clearance volume
(B) The ratio of the air actually delivered to the amount of piston displacement
(C) Reciprocal of compression ratio
(D) Index of compressor performance
Answer: (B) The ratio of the air actually delivered to the amount of piston displacement
Q7. A centrifugal compressor works on the principle of
(A) Conversion of pressure energy into kinetic energy
(B) Conversion of kinetic energy into pressure energy
(C) Centripetal action
(D) Generating pressure directly
Answer: (B) Conversion of kinetic energy into pressure energy
Q8. Losses in a centrifugal compressor are due to
(A) Inlet losses
(B) Impeller channel losses
(C) Diffuser losses
(D) All of the above
Answer: (D) All of the above
Q9. The mass of gas turbine per kW developed is about __ as that of an I.C. engine.
(A) Same
(B) One-half
(C) One fourth
(D) One sixth
Answer:(D) One sixth
Q10. In a centrifugal compressor, an increase in speed at a given pressure ratio causes
(A) Increase in flow
(B) Decrease in flow
(C) Increase in efficiency
(D) Increase in flow and decrease in efficiency
Answer: (D) Increase in flow and decrease in efficiency
Q11. In jet engines, for the efficient production of large power, fuel is burnt in an atmosphere of
(A) Vacuum
(B) Atmospheric air
(C) Compressed air
(D) Oxygen alone
Answer: (C) Compressed air
Q12. In multistage compressor, the isothermal compression is achieved by
(A) Employing inter-cooler
(B) By constantly cooling the cylinder
(C) By running compressor at very slow speed
(D) By insulating the cylinder
Answer: (C) By running compressor at very slow speed
Q13. The mean effective pressure of the compressor is the
(A) Actual volume of the air delivered by the compressor when reduced to normal temperature and pressure conditions
(B) Volume of air delivered by the compressor
(C) Volume of air sucked by the compressor during its suction stroke
(D) None of the above
Answer: (D) None of the above
Q13. In gas turbines, high thermal efficiency is obtained in
(A) Closed cycle
(B) Open cycle
(C) Both of the above
(D) Closed/open depending on other considerations
Answer: (A) Closed cycle
Q14. The pressure and temperature conditions of air at the suction of compressor are
(A) Atmospheric
(B) Slightly more than atmospheric
(C) Slightly less than atmospheric
(D) Pressure slightly less than atmospheric and temperature slightly more than atmospheric
Answer: (D) Pressure slightly less than atmospheric and temperature slightly more than atmospheric
Q15. In axial flow compressor, exit flow angle deviation from the blade angle is a function of
(A) Blade camber
(B) Blade camber and incidence angle
(C) Space-chord ratio
(D) Blade camber and space-chord ratio
Answer:(B) Blade camber and incidence angle
Q16. The air is delivered __ in one revolution in case of a three lobbed rotor.
(A) Two times
(B) Three times
(C) Four times
(D) Six times
Answer: (D) Six times
Q17. The axial flow compressor is preferred in aircraft gas turbines because of
(A) Low frontal area
(B) Higher thrust
(C) High pressure rise
(D) None of these
Answer: (A) Low frontal area
Q18. The thermodynamic efficiency of rotary compressor is based on
(A) Isothermal compression
(B) Adiabatic compression
(C) Isentropic compression
(D) Polytropic compression
Answer: (B) Adiabatic compression
Q19. Atmospheric pressure is 1.03 kg/cm and vapour pressure is 0.03 kg/cm. The air pressure will be
(A) 1.03 kg/cm²
(B) 1.06 kg/cm²
(C) 1.00 kg/cm²
(D) 0.53 kg/cm²
Answer: (C) 1.00 kg/cm²
Q20. The work-done on a compressor will be minimum if air is taken from
(A) The atmosphere
(B) A source at 0° C
(C) A source of low temperature air
(D) A source of high temperature air
Answer: (C) A source of low temperature air
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