# Compressors, Gas Turbines and Jet Engines Objective Questions with Answers – Set 13

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## Q1. The degree of reaction of an axial flow turbine is the ratio of isentropic temperature drop in a blade row to the

(A) Adiabatic temperature drop in the stage
(B) Total temperature drop
(C) Total temperature drop in the stage
(D) Total adiabatic temperature drop

## Q2. Pick up the wrong statement

(A) Large gas turbines employ axial flow compressors
(B) Axial flow compressors are more stable than centrifugal type compressors but not as efficient
(C) Axial flow compressors have high capacity and efficiency
(D) Axial flow compressors have instability region of operation

## Q3. The specific output per kg mass flow rate of a gas turbine (having fixed efficiencies of compressor and turbine and fixed higher and lower temperature) with increase in pressure ratio will

(A) Increase first at fast rate and then slow
(B) Increase first at slow rate and then fast
(C) Decrease continuously
(D) First increase, reach maximum and then decrease

## Q4. Standard air is the air at

(A) Atmospheric conditions at any specific location
(B) 20°C and 1 kg/cm² and relative humidity 36%
(C) 0°C and standard atmospheric conditions
(D) 15°C and 1 kg/cm²

## Q5. In the axial flow gas turbine, the work ratio is the ratio of

(A) Compressor work and turbine work
(B) Output and input
(C) Actual total head temperature drop to the isentropic total head drop from total head inlet to static head outlet
(D) Actual compressor work and theoretical compressor work

## Q6. The power available for takeoff and climb in case of turbojet engine as compared to reciprocating engine is

(A) Less
(B) More
(C) Same
(D) May be less or more depending on ambient conditions

## Q7. The working fluid in a turbine is

(A) In two phases
(B) In three phases
(C) In a single phase
(D) In the form of air and water mixture

## Q8. In a single stage, single acting reciprocating air compressor, without clearance, the work-done on the air during isentropic compression is __ the heat required to raise the temperature of air from T₁ to T₂ at a constant pressure.

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

(A) 10 to 40%
(B) 40 to 60%
(C) 60 to 70%
(D) 70 to 90%

## Q10. A closed gas turbine in which fuel is burnt directly in the air is not possible because of

(A) Paucity of O2
(B) Increasing gas temperature
(C) High specific volume
(D) High friction losses

## Q11. Gas turbine cycle with regenerator

(A) Increases thermal efficiency
(B) Allows high compression ratio
(C) Decreases heat loss is exhaust
(D) Allows operation at very high altitudes

## Q12. Free air is the air at

(A) Atmospheric conditions at any specific location
(B) 20°C and 1 kg/cm² and relative humidity of 36%
(C) 0°C and standard atmospheric conditions
(D) 15°C and 1 kg/cm²

## Q13. 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.

## Q14. Choose the correct statement

(A) Gas turbine requires lot of cooling water
(B) Gas turbine is capable of rapid start up and loading
(C) Gas turbines has flat efficiency at part loads
(D) Gas turbines have high standby losses and require lot of maintenance

## Q15. The compression ratio in a gas turbine is of the order of

(A) 3.5 : 1
(B) 5 : 1
(C) 8 : 1
(D) 12 : 1

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