# Compressors, Gas Turbines and Jet Engines MCQ Practice Test – Set 6 :: Mechanical Engineering

Are you guys looking for Mechanical Engineering MCQ Questions with Answers PDF Free Download as per Mechanical Engineering new exam pattern? You came to the right page. This may assist you to understand and check your knowledge about the Subjects. Students also can take a free test of the Multiple Choice Questions of Mechanical Engineering. Each question has four options followed by the right answer. These Mechanical Engineering MCQ Questions are selected supported by the newest exam pattern.

## Q1. A compressor mostly used for supercharging of I.C. engines is

(B) Axial flow compressor
(C) Roots blower
(D) Reciprocating 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

## 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

## 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

(A) Same
(B) One-half
(C) One fourth
(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

## 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

## 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

(B) Blade camber and incidence angle
(C) Space-chord ratio
(D) Blade camber and space-chord ratio

(A) Two times
(B) Three times
(C) Four times
(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

## Q18. The thermodynamic efficiency of rotary compressor is based on

(A) Isothermal compression
(C) Isentropic compression
(D) Polytropic compression

(A) 1.03 kg/cm²
(B) 1.06 kg/cm²
(C) 1.00 kg/cm²
(D) 0.53 kg/cm²