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
Remain same
Decrease
Increase
None of the above
Correct Answer :
C. Increase
Related Questions
The compressor efficiency is the
Isothermal H.P/indicated H.R
Isothermal H.P./shaft H.R
Total output/air input
Compression work/motor input
In the axial flow gas turbine, the work ratio is the ratio of
Compressor work and turbine work
Output and input
Actual total head temperature drop to the isentropic total head drop from total head inlet to static head outlet
Actual compressor work and theoretical compressor work
For a two stage reciprocating compressor, compression from p₁ to p₃ is with perfect intercooling and no pressure losses. If compression in both the cylinders follows the same polytropic process and the atmospheric pressure is pa, then the intermediate pressure p₂ is given by
p₂ = (p₁ + p₃)/2
p₂ = p₁. p₃
P₂ = Pa × p₃/p₁
p₂ = Pa p₃/p₁
Pick up the wrong statement about advantages of multistage compression
Better lubrication is possible advantages of multistage
More loss of air due to leakage past the cylinder
Mechanical balance is better
Air can be cooled perfectly in between
The pressure and temperature conditions of air at the suction of compressor are
Atmospheric
Slightly more than atmospheric
Slightly less than atmospheric
Pressure slightly less than atmospheric and temperature slightly more than atmospheric
The thermal efficiency of a simple gas turbine for a given turbine inlet temperature with increase in pressure ratio
Increases
Decreases
First increases and then decreases
First decreases and then increases
Maximum delivery pressure is a rotary air compressor is of the order of
6 kg/cm²
10 kg/cm²
16 kg/cm²
25 kg/cm²
The pressure ratio in gas turbines is of the order of
2 : 1
4 :1
61 : 1
9 : 1
The effective power of gas turbines is increased by adding the following in compressor
Ammonia and water vapour
Carbon dioxide
Nitrogen
Hydrogen
Gas turbines use following type of air compressor
Centrifugal type
Reciprocating type
Lobe type
Axial flow type
The degree of reaction is usually kept ________ for all types of axial flow compressors.
0.2
0.3
0.4
0.5
The axial flow compressor is preferred in aircraft gas turbines because of
Low frontal area
Higher thrust
High pressure rise
None of these
What will be the volume of air at 327°C if its volume at 27°C is 1.5 m³/ mt?
3 m³/ mt.
1.5 m³/ mt.
18 m³/ mt.
6 m³/ mt.
For supplying intermittent small quantity of air at high pressure, following compressor is best suited
Centrifugal
Reciprocating
Axial
Screw
Compression efficiency is compared against
Ideal compression
Adiabatic compression
Isentropic compression
Isothermal compression
For minimum work in multistage compression, assuming same index of compression in all stages
Work done in first stage should be more
Work done in subsequent stages should increase
Work done in subsequent stages should decrease
Work done in all stages should be equal
A compressor at high altitude will draw
More power
Less power
Same power
More/less power depending on other factors
In a single acting reciprocating compressor, the suction, compression and delivery of air takes place in ________ of the piston.
One stroke
Two strokes
Three strokes
Four strokes
The main purpose of reheating in gas turbine is to
Increase temperature
Reduce turbine size
Increase power output
Increase 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
The volumetric efficiency of a compressor falls roughly as follows for every 5°C increase in atmospheric temperature
0.1 %
0.5 %
1 %
5 %
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
In a centrifugal compressor, the flow of air is ________ to the axis of compressor.
Parallel
Perpendicular
Inclined
None of these
Inter-cooling in gas turbine results in
Increase in net output but decrease in thermal efficiency
Increase in thermal efficiency but decrease in net output
Increase in both thermal efficiency and net output
Decrease in both thermal efficiency and net output
High air-fuel ratio in gas turbines
Increases power output
Improves thermal efficiency
Reduces exhaust temperature
Do not damage turbine blades
The ratio of the volume of free air delivery per stroke to the swept volume of the piston, is known as
Compressor efficiency
Volumetric efficiency
Isothermal efficiency
Mechanical efficiency
A closed cycle gas turbine consists of a
Compressor
Heating chamber
Cooling chamber
All of these
The air power of the compressor is also known as
Indicated power
Brake power
Frictional power
None of these
The indicated work per unit mass of air delivered is
Directly proportional to clearance volume
Greatly affected by clearance volume
Not affected by clearance volume
Inversely proportional to clearance volume
The ratio of isentropic work to Euler work is known as
Pressure coefficient
Work coefficient
Polytropic reaction
Slip factor