For slow speed large capacity compressor, following type of valve will be best suited
Poppet valve
Mechanical valve of the Corliss, sleeve, rotary or semi rotary type
Disc or feather type
Any of the above
Correct Answer :
C. Disc or feather type
Related Questions
Pick up the false statement
Gas turbine is a self starting unit
Gas turbine does not require huge quantity of water like steam plant
Exhaust losses in gas turbine are high due to large mass flow rate
Overall efficiency of gas turbine plant is lower than that of a reciprocating engine
An aftercooler is used to
Remove impurities from air
Reduce volume of air
Cause moisture and oil vapour to drop out
Cool the air
In a turbo jet engine, subsequent to heat addition to compressed air, to get the power output, the working substance is expanded in
Exit nozzle, which is a constant volume process
Exit nozzle, which is essentially an isentropic process
Turbine blades, which is a constant volume process
Turbine blades, which is essentially an isentropic process
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.
Equal to
Less than
Greater than
None of these
The fuel consumption in gas turbines is accounted for by
Lower heating value
Higher heating value
Heating value
Higher calorific value
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 gas turbines, high thermal efficiency is obtained in
Closed cycle
Open cycle
Both of the above
Closed/open depending on other considerations
Adiabatic compression is one in which
Temperature during compression remains constant
No heat leaves or enters the compressor cylinder during compression
Temperature rise follows a linear relationship
Work done is maximum
Which of the following statement is correct?
The ratio of the discharge pressure to the inlet pressure of air is called compressor efficiency
The compression ratio for the compressor is always greater than unity
The compressor capacity is the ratio of workdone per cycle to the stroke volume
During isothermal compression of air, the workdone in a compressor is maximum
In n₁ and n₂ are the indices of compression for the first and second stage of compression, then the ratio of workdone on the first and second stages (W₁/W₂) with perfect intercooling is given by
W₁/W₂ = n₂(n₁ - 1)/n₁(n₂ - 1)
W₁/W₂ = n₁(n₂ - 1)/n₂(n₁ - 1)
W₁/W₂ = n₁/n₂
W₁/W₂ = n₂/n₁
Pressure ratio in gas turbines is the ratio of
Compressor pressure ratio
Highest pressure to exhaust pressure
Inlet pressure to exhaust pressure
Pressures across the turbine
The assumption made in two stage compression with intercooler is that
There is no pressure drop in the intercooler
The compression in both the cylinders is polytropic
The suction and delivery of air takes place at constant pressure
All of the above
Isothermal compression though most efficient, but is not practicable because
It requires very big cylinder
It does not increase pressure much
It is impossible in practice
Compressor has to run at very slow speed to achieve it
In a single acting reciprocating air compressor, without clearance, the compression of air may be
Isothermal
Polytropic
Isentropic
Any one of these
Ramjet engine
Is self operating at zero flight speed
Is not self operating at zero flight speed
Requires no air for its operation
Produces a jet consisting of plasma
In a compressor, free air delivered is the actual volume delivered at the stated pressure reduced to
N.T.P. conditions
Intake temperature and pressure conditions
0°C and 1 kg/cm²
20°C and 1 kg/cm²
Ratio of compression is the ratio of
Gauge discharge pressure to the gauge intake pressure
Absolute discharge pressure to the absolute intake pressure
Pressures at discharge and suction corresponding to same temperature
Stroke volume and clearance volume
For perfect intercooling in a two stage compressor
p₂/p₁ = p₃/p₂
p₁/p₃ = p₂/p₁
p₁ = p₃
p₁ = p₂ p₃
Efficiency of gas turbine is increased by
Reheating
Inter cooling
Adding a regenerator
All of the above
During peak load periods, the best method of controlling compressors is
Start-stop motor
Constant speed unloader
Relief valve
Variable speed
The maximum temperature in a gas turbine is
200°C
500°C
700°C
1000°C
Axial flow compressor resembles
Centrifugal pump
Reciprocating pump
Turbine
Sliding vane compressor
The compression ratio in a gas turbine is of the order of
3.5 : 1
5 : 1
8 : 1
12 : 1
For a two stage compressor, if index of compression for higher stage is greater than index of compression for lower stage, then the optimum pressure as compared to ideal case will
Increase
Decrease
Remain unaffected
Other factors control it
For slow speed large capacity compressor, following type of valve will be best suited
Poppet valve
Mechanical valve of the Corliss, sleeve, rotary or semi rotary type
Disc or feather type
Any 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
It is not possible to use closed gas turbine cycle in aeronautical engines because
It is inefficient
It is bulky
It requires cooling water for its operation
None of the above
Isothermal compression efficiency can be attained by running the compressor
At very high speed
At very slow speed
At average speed
At zero speed
The net work input required for compressor with increase in clearance volume
Increases
Decreases
Remains same
Increases/decreases depending on compressor capacity
The air-fuel ratio in gas turbines is of the order of
7 : 1
15 : 1
30 : 1
50 : 1.