The efficiency of jet engine is
Lower at low speed
Higher at high altitudes
Same at all altitudes
Higher at high speed
Correct Answer :
B. Higher at high altitudes
Related Questions
Reciprocating air compressor is best suited for
Large quantity of air at high pressure
Small quantity of air at high pressure
Small quantity of air at low pressure
Large quantity of air at low pressure
Which of the following statement is wrong?
In a two stage reciprocating air compressor with complete intercooling, maximum work is saved.
The minimum work required for a two stage reciprocating air compressor is double the work required for each stage.
The ratio of the volume of free air delivery per stroke to the swept volume of the piston is called volumetric efficiency.
None of the above
The maximum delivery pressure in a rotary air compressor is
10 bar
20 bar
30 bar
50 bar
The thrust of a jet propulsion power unit can be increased by
Injecting water into the compressor
Burning fuel after gas turbine
Injecting ammonia into the combustion chamber
All of the above
The output of a gas turbine is 300 KW and its efficiency is 20 percent, the heat supplied is
6000 KW
15 KW
600 KW
150 KW
In a centrifugal compressor, an increase in speed at a given pressure ratio causes
Increase in flow
Decrease in flow
Increase in efficiency
Increase in flow and decrease in efficiency
A compressor at high altitude will draw
More power
Less power
Same power
More/less power depending on other factors
Ratio of indicated H.P. and brake H.P. is known as
Mechanical efficiency
Volumetric efficiency
Isothermal efficiency
Adiabatic efficiency
A gas turbine used in air craft should have
High h.p. and low weight
Low weight and small frontal area
Small frontal area and high h.p.
High speed and high h.p
Standard air is the air at
Atmospheric conditions at any specific location
20°C and 1 kg/cm² and relative humidity 36%
0°C and standard atmospheric conditions
15°C and 1 kg/cm²
Axial flow compressor resembles
Centrifugal pump
Reciprocating pump
Turbine
Sliding vane compressor
To avoid moisture troubles, the compressed air main line should
Rise gradually towards the point of use
Drop gradually towards the point of use
Be laid vertically
Be laid exactly horizontally
Pick up the correct statement
Gas turbine uses low air-fuel ratio to economise on fuel
Gas turbine uses high air-fuel ratio to reduce outgoing temperature
Gas turbine uses low air-fuel ratio to develop the high thrust required
All of the above
Reheating in multistage expansion gas turbine results in
High thermal efficiency
Reduction in compressor work
Decrease of heat loss in exhaust
Maximum work output
The ideal efficiency of simple gas turbine cycle depends on
Pressure ratio
Maximum cycle temperature
Minimum cycle temperature
All of the above
The pressure ratio for an open cycle gas turbine compared to closed cycle gas turbine of same h.p. is
Low
High
Same
Low/high depending on make and type
Air-fuel ratio in a jet engine will be of the order of
10 : 1
15 : 1
20 : 1
60 : 1
A jet engine works on the principle of conservation of
Mass
Energy
Flow
Linear momentum
Which one of the following is the effect of blade shape on performance of a centrifugal compressor?
Backward curved blades has poor efficiency
Backward curved blades lead to stable performance
Forward curved blades has higher efficiency
Forward curved blades produce lower pressure ratio
Gas turbines for power generation are normally used
To supply base load requirements
To supply peak load requirements
To enable start thermal power plant
In emergency
More than one stage will be preferred for reciprocating compressor if the delivery pressure is more than
2 kg/cm²
6 kg/cm²
10 kg/cm²
14.7 kg/cm²
The inlet pressure is always ________ the discharge pressure.
Equal to
Less than
More than
None of these
Maximum work is done in compressing air when the compression is
Isothermal
Adiabatic
Polytropic
None of the above
The efficiency of jet engine is
Lower at low speed
Higher at high altitudes
Same at all altitudes
Higher at high speed
As the turbine inlet temperature increases, the thermal efficiency of gas turbine for the optimum pressure ratio
Increases
Decreases
Remain same
First increases and then decreases
A rocket engine for the combustion of its fuel
Carries its own oxygen
Uses surrounding air
Uses compressed atmospheric air
Does not require oxygen
The material commonly used for air craft gas turbine is
Stainless steel
High alloy steel
Duralumin
Timken, Haste alloys
The gas in cooling chamber of a closed cycle gas turbine is cooled at
Constant volume
Constant temperature
Constant pressure
None of these
A closed gas turbine in which fuel is burnt directly in the air is not possible because of
Paucity of O2
Increasing gas temperature
High specific volume
High friction losses
The efficiency of the vane blower is (where W₁ = Workdone due to compression, and W₂ = Workdone due to back flow)
W₁/(W₁ + W₂)
W₂/(W₁ + W₂)
(W₁ + W₂)/W₁
(W₁ + W₂)/W₂