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4

In jet engines, for the efficient production of large power, fuel is burnt in an atmosphere of

A. Vacuum

B. Atmospheric air

C. Compressed air

D. Oxygen alone

Correct Answer :

C. Compressed air


Related Questions

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4

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

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4

The ratio of outlet whirl velocity to blade velocity in case of centrifugal compressor is called

A. Slip factor

B. Velocity factor

C. Velocity coefficient

D. None of the above

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4

Reheating in gas turbine results in

A. Increase of work ratio

B. Decrease of thermal efficiency

C. Decrease of work ratio

D. Both (A) and (B) above

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4

Axial flow compressor resembles

A. Centrifugal pump

B. Reciprocating pump

C. Turbine

D. Sliding vane compressor

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4

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

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4

The temperature of air at the beginning of the compression stroke is ________ the atmospheric temperature.

A. Equal to

B. Less than

C. More than

D. None of these

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4

The criterion of the thermodynamic efficiency for rotary compressor is

A. Isentropic compression

B. Isothermal compression

C. Polytropic compression

D. None of the above

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4

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

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4

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

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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

Pick up the correct statement

A. Gas turbine uses low air-fuel ratio to economise on fuel

B. Gas turbine uses high air-fuel ratio to reduce outgoing temperature

C. Gas turbine uses low air-fuel ratio to develop the high thrust required

D. All of the above

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4

When the outlet angle from the rotor of a centrifugal compressor is more than 90°, then the blades are said to be

A. Forward curved

B. Backward curved

C. Radial

D. None of these

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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

The performance of air compressor at high altitudes will be ________ as compared to that at sea level.

A. Same

B. Lower

C. Higher

D. None of these

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4

A rocket engine for the combustion of its fuel

A. Carries its own oxygen

B. Uses surrounding air

C. Uses compressed atmospheric air

D. Does not require oxygen

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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

In air compressors, free air delivery means the

A. Actual volume of the air delivered by the compressor when reduced to normal temperature and pressure conditions

B. Volume of air delivered by the compressor

C. Volume of air sucked by the compressor during its suction stroke

D. None of the above

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4

A rocket engine uses ________ for the combustion of its fuel.

A. Surrounding air

B. Compressed atmospheric air

C. Its own oxygen

D. None 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

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

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4

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

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4

Standard air is the air at ________ and relative humidity of 36 percent.

A. 0.1 bar and 20°C

B. 1 bar and 20°C

C. 0.1 bar and 40°C

D. 1 bar and 40°C

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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

The reason for volumetric efficiency of reciprocating compressor being less than 100 percent is

A. Pressure drop across the valves

B. Superheating in compressor

C. Clearance volume and leakages

D. All of these

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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

The volumetric efficiency for reciprocating air compressors is about

A. 10 to 40 %

B. 40 to 60 %

C. 60 to 70 %

D. 70 to 90 %

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4

Phenomenon of choking in compressor means

A. No flow of air

B. Fixed mass flow rate regardless of pressure ratio

C. Reducing mass flow rate with increase in pressure ratio

D. Increased inclination of chord with air steam

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4

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

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4

Pick up the false statement

A. Gas turbine is a self starting unit

B. Gas turbine does not require huge quantity of water like steam plant

C. Exhaust losses in gas turbine are high due to large mass flow rate

D. Overall efficiency of gas turbine plant is lower than that of a reciprocating engine

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4

Aeroplanes employ following type of compressor

A. Radial flow

B. Axial flow

C. Centrifugal

D. None of the above