# Compressors, Gas Turbines and Jet Engines – Set 05

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## Q1. An ideal air compressor cycle with clearance on P-V diagram can be represented by following processes

(A) One adiabatic, two isobaric, and one constant volume
(B) Two adiabatic and two isobaric
(C) Two adiabatic, one isobaric and one constant volume
(D) One adiabatic, one isobaric and two constant volumes

## Q2. The capacity of a compressor is 5 m/min refers to

(A) Standard air
(B) Free air
(C) Compressed air
(D) Compressed air at delivery pressure

(A) 30:1
(B) 40:1
(C) 50:1
(D) 60:1

## Q4. High air-fuel ratio in gas turbines

(A) Increases power output
(B) Improves thermal efficiency
(C) Reduces exhaust temperature
(D) Do not damage turbine blades

## Q5. The process, which causes the air to enter the impeller blades of a centrifugal compressor at __ velocity (without effecting the mass of air to flow and velocity of flow) is known as prewhirl.

(A) Reduced
(B) Increased
(C) Zero
(D) None of these

## Q6. Ratio of indicated h.p. to shaft h.p. in known as

(A) Compressor efficiency
(B) Isothermal efficiency
(C) Volumetric efficiency
(D) Mechanical efficiency

## Q7. Compression efficiency is compared against

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

## Q8. The overall isothermal efficiency of compressor is defined as the ratio of

(A) Isothermal h.p. to the BHP of motor
(B) Isothermal h.p. to adiabatic h.p.
(C) Power to drive compressor to isothermal h.p.
(D) Work to compress air isothermally to work for actual compression

## Q9. For minimum work required to compress and deliver a quantity of air by multistage compression

(A) The compression ratio in each stage should be same
(B) The intercooling should be perfect
(C) The work-done in each stage should be same
(D) All of the above

## Q10. The efficiency of jet engine is

(A) Lower at low speed
(B) Higher at high altitudes
(C) Same at all altitudes
(D) Higher at high speed

## Q11. In a centrifugal compressor, the ratio of the __ to the blade velocity is called slip factor.

(A) Inlet whirl velocity
(B) Outlet whirl velocity
(C) Inlet velocity of flow
(D) Outlet velocity of flow

## Q12. The net work input required for compressor with increase in clearance volume

(A) Increases
(B) Decreases
(C) Remains same
(D) Increases/decreases depending on compressor capacity

## Q13. Intercooling in gas turbines

(A) Decreases net output but increases thermal efficiency
(B) Increases net output but decreases thermal efficiency
(C) Decreases net output and thermal efficiency both
(D) Increases net output and thermal efficiency both

## Q14. The most efficient method of compressing air is to compress it

(A) Isothermally
(C) Isentropically
(D) Isochronically

## Q15. The compressed air may be used

(A) In gas turbine plants
(B) For operating pneumatic drills
(C) In starting and supercharging of I.C. engines
(D) All of the above

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