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What is the correct answer?

4

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

Correct Answer :

B. In the direction of motion of blades


Related Questions

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4

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

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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

Gas turbine as compared to internal combustion engine

A. Can be driven at a very high speed

B. Produces uniform torque

C. Has more efficiency

D. All of these

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4

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

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4

Which of the following statement is correct?

A. The ratio of the discharge pressure to the inlet pressure of air is called compressor efficiency

B. The compression ratio for the compressor is always greater than unity

C. The compressor capacity is the ratio of workdone per cycle to the stroke volume

D. During isothermal compression of air, the workdone in a compressor is maximum

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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

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4

If p₁, is the pressure of air entering the L.P. cylinder and p₂ is the pressure of air leaving the L.P. cylinder (or intercooler pressure), then the ratio of cylinder diameters for a single acting, two stage reciprocating air compressor with complete intercooling is given by (where D₁ = Dia. of L.P. cylinder, and D₂ = Dia. of H.P. cylinder)

A. D₁/D₂ = p₁ p₂

B. D₁/D₂ = p₁/p₂

C. D₁/D₂ = p₂/p₁

D. None of these

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4

Pick up the wrong statement

A. Centrifugal compressors deliver practically constant pressure over a considerable range of capacities

B. Axial flow compressors have a substantially constant delivery at variable pressures

C. Centrifugal compressors have a wider stable operating range than axial flow compressors

D. Axial flow compressors are bigger in diameter compared to centrifugal type

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4

Fighter bombers use following type of engine

A. Turbojet

B. Turbo-propeller

C. Rocket

D. Ramjet

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4

Axial flow compressor has the following advantage over centrifugal compressor

A. Larger air handling ability per unit frontal area

B. Higher pressure ratio per stage

C. Aerofoil blades are used

D. Higher average velocities

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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 single stage, single acting reciprocating air compressor, without clearance, the workdone 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

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4

The ideal efficiency of simple gas turbine cycle depends on

A. Pressure ratio

B. Maximum cycle temperature

C. Minimum cycle temperature

D. All of the above

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4

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

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4

Pick up wrong statement. Surging phenomenon in centrifugal compressor depends on

A. Mass flow rate

B. Pressure ratio

C. Change in load

D. Stagnation pressure at the outlet

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4

An ideal air compressor cycle with 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 thrust of a jet propulsion power unit can be increased by

A. Injecting water into the compressor

B. Burning fuel after gas turbine

C. Injecting ammonia into the combustion chamber

D. All of the above

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4

The maximum temperature in a gas turbine is

A. 200°C

B. 500°C

C. 700°C

D. 1000°C

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4

Euler's equation can be used for

A. Radial flow compressors

B. Axial flow compressors

C. Pumps

D. All 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

In a single stage, single acting reciprocating air compressor without clearance volume, the workdone is maximum during

A. Isothermal compression

B. Isentropic compression

C. Polytropic compression

D. None of these

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4

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

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4

If V, U and Vr represent the absolute velocity of fluid, velocity of blade, and relative velocity of fluid, and suffix I and o stand for entry and exit conditions, then in a rotary machine whose degree of reaction is unity

A. Vi = Vo

B. Vt > Vo

C. U < Vo

D. V = Uo

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4

In the aircraft propellers

A. The propulsive matter is caused to flow around the propelled body

B. Propulsive matter is ejected from within the propelled body

C. Its functioning does not depend on presence of air

D. All of the above

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4

A simple turbojet engine is basically

A. A propeller system

B. Gas turbine engine equipped with a propulsive nozzle and diffuse

C. Chemical rocket engine

D. Ramjet engine

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4

The following is true for an open cycle gas turbine having exhaust heat exchanger. Atmospheric air before entering the compressor is

A. Heated

B. Compressed air before entering the combustion chamber is heated

C. Bled gas from turbine is heated and readmitted for complete expansion

D. Exhaust gases drive the compressor

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4

Water is injected in gas turbine cycle to

A. Control temperature

B. Control output of turbine

C. Control fire hazards

D. Increase efficiency

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4

When the temperature of air leaving the intercooler, in a two stage compression with intercooler, is ________ the original atmospheric air temperature, then the intercooling is known as perfect or complete intercooling.

A. Equal to

B. Less than

C. More than

D. None of these

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4

The indicated work per unit mass of air delivered is

A. Directly proportional to clearance volume

B. Greatly affected by clearance volume

C. Not affected by clearance volume

D. Inversely proportional to clearance volume

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4

Which is false statement about air receivers?

A. These are used to dampen pulsations

B. These act as reservoir to take care of sudden demands

C. These increase compressor efficiency

D. These knock out some oil and moisture