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4

Pressure ratio in gas turbines is the ratio of

A. Compressor pressure ratio

B. Highest pressure to exhaust pressure

C. Inlet pressure to exhaust pressure

D. Pressures across the turbine

Correct Answer :

B. Highest pressure to exhaust pressure


Related Questions

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4

An ideal air compressor cycle without clearance on PV 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

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4

The compressor efficiency is the

A. Isothermal H.P/indicated H.R

B. Isothermal H.P./shaft H.R

C. Total output/air input

D. Compression work/motor input

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4

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

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4

The efficiency of a jet engine is higher at

A. Low speeds

B. High speeds

C. Low altitudes

D. High altitudes

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4

In jet propulsion power unit, the inlet duct of diverging shape is used in order to

A. Collect more air

B. Convert kinetic energy of air into pressure energy

C. Provide robust structure

D. Beautify the shape

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4

Which of the following statement is wrong?

A. In a two stage reciprocating air compressor with complete intercooling, maximum work is saved.

B. The minimum work required for a two stage reciprocating air compressor is double the work required for each stage.

C. The ratio of the volume of free air delivery per stroke to the swept volume of the piston is called volumetric efficiency.

D. None of the above

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4

Which one of the following is the effect of blade shape on performance of a centrifugal compressor?

A. Backward curved blades has poor efficiency

B. Backward curved blades lead to stable performance

C. Forward curved blades has higher efficiency

D. Forward curved blades produce lower pressure ratio

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4

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

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4

The compression ratio for the compressor is always __________ unity.

A. Equal to

B. Less than

C. More than

D. None of these

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4

In multistage compressor, the isothermal compression is achieved by

A. Employing intercooler

B. By constantly cooling the cylinder

C. By running compressor at very slow speed

D. By insulating the cylinder

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4

The advantage of multistage compression over single stage compression is

A. Lower power consumption per unit of air delivered

B. Higher volumetric efficiency

C. Decreased discharge temperature

D. All of the above

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4

A turboprop is preferred to turbojet because

A. It has high propulsive efficiency at high speeds

B. It can fly at supersonic speeds

C. It can fly at high elevations

D. It has high power for take off

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4

The thrust on the rotor in a centrifugal compressor is produced by

A. Radial component

B. Axial component

C. Tangential component

D. None of the above

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4

The maximum delivery pressure in a rotary air compressor is

A. 10 bar

B. 20 bar

C. 30 bar

D. 50 bar

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4

Euler's equation is applicable for

A. Centrifugal compressor

B. Axial compressor

C. Pumps

D. All of the above

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4

Maximum temperature in a gas turbine is of the order of

A. 700°C

B. 2000°C

C. 1500°C

D. 1000°C

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4

In a compressor, free air delivered is the actual volume delivered at the stated pressure reduced to

A. N.T.P. conditions

B. Intake temperature and pressure conditions

C. 0°C and 1 kg/cm²

D. 20°C and 1 kg/cm²

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4

During peak load periods, the best method of controlling compressors is

A. Start-stop motor

B. Constant speed unloader

C. Relief valve

D. Variable speed

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4

For speed above 3000 km/hour, it is more advantageous to use

A. Turbojet engine

B. Ramjet engine

C. Propellers

D. Rockets

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4

Propulsive efficiency is defined as ratio of

A. Thrust power and fuel energy

B. Engine output and propulsive power

C. Propulsive power and fuel input

D. Thrust power and propulsive power

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4

In a single acting reciprocating air compressor, without clearance, the compression of air may be

A. Isothermal

B. Polytropic

C. Isentropic

D. Any one of these

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4

The volume of air delivered in a medium capacity air compressor per unit time is

A. 0.1 to 1.2 m³/s

B. 0.15 to 5 m³/s

C. Above 5 m³/s

D. None of these

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4

If the clearance ratio for a reciprocating air compressor is 'K', then its volumetric efficiency is given by

A. 1 - k + k (p₁/p₂)1/n

B. 1 + k - k (p₂/p₁)1/n

C. 1 - k + k (p₁/p₂) n- 1/n

D. 1 + k - k (p₂/p₁) n-1/n

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4

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

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4

Turbofan engine employs

A. One air stream

B. Two or more air streams

C. No air stream

D. Solid fuel firing

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4

In a four stage compressor, if the pressure at the first and third stage is 1 bar and 16 bar, then the delivery pressure at the fourth stage will be

A. 1 bar

B. 16 bar

C. 64 bar

D. 256 bar

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4

Reheating in a gas turbine

A. Increases the thermal efficiency

B. Increases the compressor work

C. Increases the turbine work

D. Decreases the thermal efficiency

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4

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

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4

Open cycle gas turbine works on

A. Brayton or Atkinson cycle

B. Rankine cycle

C. Carnot cycle

D. Erricson cycle

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4

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