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 velocity of air entering in a rocket is __________ as compared to an aircraft.
-
zero -
less -
more -
same
With the decrease in compression ratio, the volumetric efficiency
-
does not change -
increases -
decreases
The operation of the reciprocating air motor is similar to reciprocating air compressor.
-
True -
False
If the flow of air through the compressor is parallel to its axis, then the compressor is
-
reciprocating compressor -
centrifugal compressor -
axial flow compressor -
turbo-compressor
In a centrifugal compressor, the flow of air is __________ to the axis of compressor.
-
parallel -
perpendicular -
inclined -
none of these
The operation of the reciprocating air motor is similar to reciprocating air compressor.
-
True -
False
When the outlet angle from the rotor of a centrifugal compressor is more than 90°, then the blades are said to be
-
forward curved -
backward curved -
radial -
none of these
Which of the following statement is correct?
-
The reciprocating compressors are best suited for high pressure and low volume capacity -
The effect of clearance volume on power consumption is negligible for the same volume of discharge -
both (a) and (b) -
none of these
The volumetric efficiency of the compressor is defined as the ratio of volume of free air delivery per stroke to the swept volume of the piston.
-
Yes -
No
For minimum work required to compress and deliver a quantity of air by multi-stage compression,
-
the compression ratio in each stage should be same -
the intercooling should be perfect -
the workdone in each stage should be same -
all of the above
Slip factor in a centrifugal compressor indicates the amount of air leaked from the storage vessel.
-
Yes -
No
A centrifugal compressor is an axial flow compressor.
-
Correct -
Incorrect
The speed of rotary air compressor is __________ as compared to reciprocating air compressor.
-
high -
low
Separators are generally used in air compressor installations
-
before the intercooler -
after the intercooler -
between the aftercooler and receiver -
before first stage suction
The multi-stage compression ofair as compared to single stage compression
-
improves volumetric efficiency for the given pressure ratio -
reduces workdone per kg of air -
gives more uniform torque -
all of these
The speed of rotary air compressor is __________ as compared to reciprocating air compressor.
-
high -
low
The volume of air sucked by the compressor during its suction stroke is called
-
free air delivery -
compressor capacity -
swept volume -
none of these
The ratio of the isentropic work to the Euler's work is known as pressure coefficient.
-
Yes -
No
A compressor must be driven by some prime mover.
-
Agree -
Disagree
When air is to be compressed at a high pressure, then it is advantageous to use
-
single stage compression -
multi-stage compression without intercooling -
multi-stage compression with intercooling -
none of these
If the flow of air through the compressor is perpendicular to its axis, then it is a
-
reciprocating compressor -
centrifugal compressor -
axial flow compressor -
turbo compressor
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
A turbo-prop is preferred to turbo-jet because
-
it has high propulsive efficiency at high speeds -
it can fly at super sonic speeds -
it can fly at high elevations -
it has high power for take off
The absolute pressure of air at the outlet of a compressor is called
-
back pressure -
critical pressure -
discharge pressure -
none of these
In air compressors, free air delivery means 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
In a jet engine, the air-fuel ratio is
-
30:1 -
40:1 -
50:1 -
60:1
The air power of the compressor is also known as
-
indicated power -
brake power -
frictional power -
none of these
The efficiency of the vane blower is (where W1 = Workdone due to compression, and W2 = Workdone due to back flow)
Volumetric efficiency of a compressor decreases with __________ in compression ratio.
-
decrease -
increase