Compressors_ Gas Turbines And Jet Engines — Part 2 MCQs with Explanations

Only rocket engines can be propelled to space because They are not air breathing engines

Gas turbine as compared to steam turbine: - Requires less space for installation - Has compressor and combustion chamber - Has less efficiency

Water is injected in gas turbine cycle to Control output of turbine

Gas turbine works on Brayton or Atkinson cycle

A closed cycle gas turbine works on Joule cycle

Open cycle gas turbine works on Brayton or Atkinson cycle

A turboprop is preferred to turbojet because It has high power for take off

In jet propulsion power unit, the inlet duct of diverging shape is used in order to Convert kinetic energy of air into pressure energy

Gas turbine cycle with regenerator Increases thermal efficiency

The ratio of the net work obtained from the gas turbine plant to the turbine work is known as work ratio

The ratio of isentropic work to Euler work is known as Pressure coefficient

The ratio of isentropic work to Euler’s work is known as Pressure Coefficient

In a single acting reciprocating compressor, the suction, compression and delivery of air takes place in two strokes of the piston.

The overall thermal efficiency of an ideal gas turbine plant is $$1 - {\left( {\frac{1}{{\text{r}}}} \right)^{\frac{{\gamma - 1}}{\gamma }}}$$ (Where r = Pressure ratio)

The capacity of a compressor is 5 m/min refers to free air

The thermal efficiency of a gas turbine as compared to a diesel plant is less

A jet engine is a type of reaction engine discharging a fast-moving jet that generates thrust by jet propulsion

Isothermal compression though most efficient, but is not practicable because Compressor has to run at very slow speed to achieve it

The type of rotary compressor used in aeroplanes, is of Axial flow type

Propulsion efficiency of the following order is obtained in practice 60%

The maximum delivery pressure in a rotary air compressor is 10 bar.

In a closed cycle gas turbine, the air is compressed isentropically

In a double acting compressor, the air is compressed In a single cylinder on both sides of the piston

The work-done on a compressor will be minimum if air is taken from A source of low temperature air

Free air is the air at Atmospheric conditions at any specific location.

Standard air is the air at 20°C and 1 kg/cm 2 and relative humidity 36%.

The overall efficiency of the compressed air system is the Ratio of shaft output of the air motor to the shaft input to the compressor

In a jet engine, the air-fuel ratio is 60 : 1.

The reason for volumetric efficiency of reciprocating compressor being less than 100 percent is - Pressure drop across the valves - Superheating in compressor - Clearance volume and leakages

Turbofan engine employs Two or more air streams

Gas turbines for power generation are normally used To supply peak load requirements

The criterion of the thermodynamic efficiency for rotary compressor is Isentropic compression

Producer gas is generally made from coke, or other carbonaceous material such as anthracite. Air is passed over the red-hot carbonaceous fuel and carbon monoxide is produced.

-Increase the turbine inlet temperature provided the turbine materials can stand the temperature or one has access to replacement parts that can withstand the temperatures. -Increase the pressure ratio. There is a limit to the efficiency increase depending upon the turbine inlet temperature. One can concievably increase the pressure ratio to a point that the increased work is never recovered because the expansion across the turbine is inadequate to recover the work. - Power augmentation through steam injection. -On turbines with HP and LP turbine separated, apply reheat.

The gas in cooling chamber of a closed cycle gas turbine is cooled at constant pressure

In a turbo jet engine, subsequent to heat addition to compressed air, to get the power output, the working substance is expanded in Turbine blades, which is essentially an isentropic process

Gas turbine as compared to internal combustion engine - Can be driven at a very high speed - Produces uniform torque -Has more efficiency

The mean effective pressure is a quantity relating to the operation of a reciprocating engine and is a valuable measure of an engine's capacity to do work that is independent of engine displacement.

After-cooler is used to Cause moisture and oil vapour to drop out

An after-cooler is used to Cause moisture and oil vapour to drop out