Ram compression in turbojet involves
Reduction of speed of incoming air and conversion of part of it into pressure energy
Compression of inlet air
Increasing speed of incoming air
Lost work
Correct Answer :
A. Reduction of speed of incoming air and conversion of part of it into pressure energy
Related Questions
If the clearance ratio for a reciprocating air compressor is 'K', then its volumetric efficiency is given by
1 - k + k (p₁/p₂)1/n
1 + k - k (p₂/p₁)1/n
1 - k + k (p₁/p₂) n- 1/n
1 + k - k (p₂/p₁) n-1/n
For supplying intermittent small quantity of air at high pressure, following compressor is best suited
Centrifugal
Reciprocating
Axial
Screw
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
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 mean effective pressure of the compressor is the
Actual volume of the air delivered by the compressor when reduced to normal temperature and pressure conditions
Volume of air delivered by the compressor
Volume of air sucked by the compressor during its suction stroke
None of the above
The ratio of work done per cycle to the swept volume in case of compressor is called
Compression index
Compression ratio
Compressor efficiency
Mean effective pressure
The volume of air delivered in a medium capacity air compressor per unit time is
0.1 to 1.2 m³/s
0.15 to 5 m³/s
Above 5 m³/s
None of these
The overall isothermal efficiency of the compressor is defined as the ratio of
Work required to compress the air isothermally to the actual work required to compress the air for the same pressure ratio
Isothermal power to the shaft power or B.P. of the motor or engine required to drive the compressor
Volume of free air delivery per stroke to the swept volume of the piston
Isentropic power to the power required to drive the compressor
The working fluid in a turbine is
In two phases
In three phases
In a single phase
In the form of air and water mixture
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
A jet engine has
No propeller
Propeller in front
Propeller at back
Propeller on the top
Stalling of blades in axial flow compressor is the phenomenon of
Air stream blocking the passage
Motion of air at sonic velocity
Unsteady periodic and reversed flow
Air stream not able to follow the blade contour
Euler's equation can be used for
Radial flow compressors
Axial flow compressors
Pumps
All of these
The following is true for an open cycle gas turbine having exhaust heat exchanger. Atmospheric air before entering the compressor is
Heated
Compressed air before entering the combustion chamber is heated
Bled gas from turbine is heated and readmitted for complete expansion
Exhaust gases drive the compressor
A machine used to raise the pressure of air is called
Gas turbine
I.C engine
Compressor
Air motor
Axial flow compressor resembles
Centrifugal pump
Reciprocating pump
Turbine
Sliding vane compressor
The advantage of multistage compression over single stage compression is
Lower power consumption per unit of air delivered
Higher volumetric efficiency
Decreased discharge temperature
All of the above
Phenomenon of choking in compressor means
No flow of air
Fixed mass flow rate regardless of pressure ratio
Reducing mass flow rate with increase in pressure ratio
Increased inclination of chord with air steam
A compressor mostly used for supercharging of I.C. engines is
Radial flow compressor
Axial flow compressor
Roots blower
Reciprocating compressor
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
A closed cycle gas turbine gives ________ efficiency as compared to an open cycle gas turbine.
Same
Lower
Higher
None of these
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
With the decrease in compression ratio, the volumetric efficiency
Does not change
Increases
Decreases
First decrease and then increase
The compression ratio in a gas turbine is of the order of
3.5 : 1
5 : 1
8 : 1
12 : 1
The degree of reaction of an axial flow turbine is the ratio of isentropic temperature drop in a blade row to the
Adiabatic temperature drop in the stage
Total temperature drop
Total temperature drop in the stage
Total adiabatic temperature drop
Diffuser in a compressor is used to
Increase velocity
Make the flow streamline
Convert pressure energy into kinetic energy
Convert kinetic energy into pressure energy
Rotary compressors are used for delivering
Small quantities of air at high pressures
Large quantities of air at high pressures
Small quantities of air at low pressures
Large quantities of air at low pressures
The performance of air compressor at high altitudes will be ________ as compared to that at sea level.
Same
Lower
Higher
None of these
In a jet engine, the air-fuel ratio is
30 : 1
40 : 1
50 : 1
60 : 1
Fighter bombers use following type of engine
Turbojet
Turbo-propeller
Rocket
Ramjet