# Compressors, Gas Turbines and Jet Engines MCQ Practice Test – Set 13 :: 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. Surging is the phenomenon of

(A) Air stream blocking the passage
(B) Motion of air at sonic velocity
(C) Unsteady, periodic and reversed flow

## Q2. There is a certain pressure ratio (optimum) for a gas turbine at which its thermal efficiency is maximum. With increase in turbine temperature, the value of pressure ratio for the peak efficiency would

(A) Remain same
(B) Decrease
(C) Increase
(D) None of the above

## Q3. 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

## Q4. In a single acting reciprocating compressor, the suction, compression and delivery of air takes place in __ of the piston.

(A) One stroke
(B) Two strokes
(C) Three strokes
(D) Four strokes

## Q5. Gas turbine blades are given a rake

(A) Equal to zero
(B) In the direction of motion of blades
(C) Opposite to the direction of motion of blades
(D) Depending on the velocity

## Q6. Water is injected in gas turbine cycle to

(A) Control temperature
(B) Control output of turbine
(C) Control fire hazards
(D) Increase efficiency

Answer: (B) Control output of turbine

## Q7. A rocket works with maximum overall efficiency when air craft velocity is equal to the

(A) Jet velocity
(B) Twice the jet velocity
(C) Half the jet velocity
(D) Average of the jet velocity

Answer: (C) Half the jet velocity

## Q8. In air breathing jet engine, the jet is formed by expanding

(A) Highly heated atmospheric air
(B) Solids
(C) Liquid
(D) Plasma

Answer: (A) Highly heated atmospheric air

## Q9. In a reciprocating air compressor, the compression work per kg of air

(A) Increases as clearance volume increases
(B) Decreases as clearance volume increases
(C) Is independent of clearance volume
(D) Increases as clearance volume decreases

Answer: (C) Is independent of clearance volume

(A) 0.1%
(B) 0.5%
(C) 1.0%
(D) 5%

## Q11. Rotary compressors are suitable for

(A) Large discharge at high pressure
(B) Low discharge at high pressure
(C) Large discharge at low pressure
(D) Low discharge at low pressure

Answer: (C) Large discharge at low pressure

## Q12. A closed cycle gas turbine gives __ efficiency as compared to an open cycle gas turbine.

(A) Same
(B) Lower
(C) Higher
(D) None of these

## Q13. Open cycle gas turbine works on

(A) Brayton or Atkinson cycle
(B) Rankine cycle
(C) Carnot cycle
(D) Ericsson cycle

Answer: (A) Brayton or Atkinson cycle

## Q14. The inlet pressure is always __ the discharge pressure.

(A) Equal to
(B) Less than
(C) More than
(D) None of these

## Q15. A gas turbine used in air craft should have

(A) High h.p. and low weight
(B) Low weight and small frontal area
(C) Small frontal area and high h.p.
(D) High speed and high h.p.

Answer: (B) Low weight and small frontal area

(A) 34%
(B) 50%
(C) 60%
(D) 72%

## Q17. Ramjet engine

(A) Is self operating at zero flight speed
(B) Is not self operating at zero flight speed
(C) Requires no air for its operation
(D) Produces a jet consisting of plasma

Answer: (B) Is not self operating at zero flight speed

## Q18. The clearance volume of the air compressor is kept minimum because

(A) It allows maximum compression to be achieved
(B) It greatly affects volumetric efficiency
(C) It results in minimum work
(D) It permits isothermal compression

Answer: (B) It greatly affects volumetric efficiency

## Q19. For a two stage reciprocating compressor, compression from p₁ to p₃ is with perfect intercooling and no pressure losses. If compression in both the cylinders follows the same polytropic process and the atmospheric pressure is pa, then the intermediate pressure p₂ is given by

(A) p₂ = (p₁ + p₃)/2
(B) p₂ = p₁. p₃
(C) P₂ = Pa × p₃/p₁
(D) p₂ = Pa p₃/p₁

Answer: (B) p₂ = p₁. p₃

## Q20. For perfect intercooling in a two stage compressor

(A) p₂/p₁ = p₃/p₂
(B) p₁/p₃ = p₂/p₁
(C) p₁ = p3
(D) p₁ = p₂ p3