Compressors, Gas Dynamics and Gas Turbines Most imp Mcq.

Compressors, Gas Dynamics and Gas Turbines Most imp Mcq.

We have total covered  past exam asked Mcq and Model Mcq for upcoming Exam.

The volume of air sucked by the compressor during its suction stroke is called

swept volume

For perfect intercooling in a two stage compressor,

 P2/P1=P3/P2

The volumetric efficiency of a compressor

decreases with increase in compression ratio

Reheating in a multi-stage expansion gas turbine __________ compressor work.

B.decreases

A compressor mostly used for supercharging of I.C.

engines is

A.radial flow compressor

The workdone on a compressor will be minimum if air is taken from

C.a source of low temperature air

In a jet propulsion unit, the products of combustion after passing through the gas turbine are discharged into

C.discharge nozzle

The ratio of the discharge pressure to the inlet pressure of air is called

A.compression ratio

The velocity of air entering in a rocket is __________ as compared to an aircraft.

A.zero

A regenerator in a gas turbine improves thermal  

efficiency.

A.Correct

Which one of the following is the effect of blade shape on performance of a centrifugal compressor ?

D.Forward curved blades produce lower pressure ratio

In a jet engine, the air-fuel ratio is

D.60:1

Which of the following bladings will give maximum pressure rise in a centrifugal compressor, assuming the same overall dimensions, blade inlet angle and rotational speeds ?

A.Forward curved blades

A compressor at high altitudes will require __________ power.

B.less

When air is to be compressed at a high pressure, then it is advantageous to use

C.multi-stage compression with intercooling

The absolute pressure of air at the outlet of a compressor is called

C.discharge pressure

The volume of air delivered in a medium capacity air compressor per unit time is

B.0.15 to 5 m3/s

In a closed cycle gas turbine, the air is compressed

C.isentropically

In a single stage, single acting reciprocating air

compressor, without clearance volume, the workdone is minimum during

A.isothermal compression

If the flow of air through the compressor is parallel to its axis, then the compressor is

C.axial flow compressor

The gas in cooling chamber of a closed cycle gas turbine is cooled at

C.constant pressure

A 3 m3/min compressor means that it

B.compresses 3 m3/ min of free air

The compression ratio for the compressor is always __________ unity.

C.more than

With the decrease in compression ratio, the volumetric efficiency

B.increases

Separators are generally used in air compressor

installations

C.between the aftercooler and receiver

If the flow of air through the compressor is

perpendicular to its axis, then it is a

B.centrifugal compressor

In air compressors, free air delivery means the

A.actual volume of the air delivered by the compressor when reduced to normal temperature and pressure conditions

The ratio of the isothermal power to the shaft power or brake power of the motor or engine required to drive the compressor is called

overall isothermal efficiency.

In a double acting compressor, the air is compressed

C.in a single cylinder on both sides of the piston

In a centrifugal compressor, the flow of air is __________ to the axis of compressor

B.perpendicular

In a high pressure compressor, the delivery pressure is

C.8 to 10 bar

When the outlet angle from the rotor of a centrifugal compressor is more than 90°, then the blades are said to be

A.forward curved

A turbo-prop is preferred to turbojet because

D.it has high power for take off

The air power of the compressor is also known as

A.indicated power

Standard air is the air at

__________ and relative humidity of 36 percent.

B.1 bar and 20° C

In a single stage, single acting reciprocating air

compressor without clearance volume, the workdone is maximum during

B.isentropic compression

The compressor capacity is defined as the

B.volume of air delivered by the compressor

A rocket engine uses __________ for the combustion of its fuel.

C.its own oxygen

A gas turbine used in air-craft should have low weight and

small frontal area.

Free air is the air at atmospheric conditions at

any specific location.

A closed cycle gas turbine works on

D.Joule cycle

In open cycle turbo-jet engines used in military aircraft, reheating the exhaust gas from the turbine by burning, more fuel is used to increase the

A.thrust and range of aircraft

The axial flow compressor is preferred in air-craft gas turbines because of

A.low frontal area

The ratio of the net work obtained from the gas turbine plant to the turbine work is known as

B.work ratio

A machine used to raise the pressure of air is called

C.compressor

In a single acting reciprocating air

compressor, without clearance, the compression of air may be

A. isothermal

B.polytropic

C.isentropic

D.any one of these

In a centrifugal compressor, the highest Mach number leading to shock wave in the fluid flow occurs at

B.diffuser outlet radius

The compressor capacity will be __________ if the

temperature of intake air is lowest.

B.highest

The mass of gas turbine per kW developed is about __________ as that of an I.C. engine.

D.one-sixth

In a centrifugal compressor, the ratio of the __________ to the blade velocity is called slip factor.

D.outlet velocity of flow

The air is delivered __________ in one revolution in case of a threelobbed rotor.

D.six times

A jet engine has A.no propeller

A rocket works with maximum overall efficiency when air-craft velocity is __________ the jet velocity.

B.one-half

The volumetric efficiency for reciprocating air compressors is about

D.70 to 90%

The maximum temperature in a gas turbine is

C.700°C

An aftercooler is used to

C.cause moisture and oil vapour to drop out

High air-fuel ratio in gas turbines

C.reduces exhaust temperature

The ratio of the volume of free air delivery per stroke to the swept volume of the piston, is known as

B.volumetric efficiency

The ratio of the indicated power to the shaft power or brake power of the motor or engine required to drive the compressor, is called

D.mechanical efficiency

The compression ratio in a gas turbine is

B.1

Only rocket engines can be propelled to space because

D.they are not air-breathing engines

The maximum combustion pressure in gas turbine is __________ as compared to I.C. engine.

B.less

A large clearance Volume in a

reciprocating compressor results in

A.reduced volume flow rate

A closed cycle gas turbine gives __________ efficiency as compared to an open cycle gas turbine.

C.higher

Intercooling in gas turbines

D.increases net output and thermal efficiency both

In axial flow compressor, exit flow angle deviation from the blade angle is a function of

B.blade camber and incidence angle

Rotary compressors are used for delivering

D.large quantities of air at low pressures

In a centrifugal compressor, an increase in speed at a given pressure ratio causes

D.increase in flow and decrease in efficiency

A rotary compressor is driven by an

A.electric motor

B.engine

C.either (a) or (b)

Which of the following statement is correct?

B.The compression ratio for the compressor is always greater than unity.

The type of rotary compressor used in gas turbines, is of

B.axial flow type

In the aircraft propellers

A.the propulsive matter is ejected from within the

propelled body

The volume of air delivered by the compressor is called

B.compressor capacity

The efficiency of a jet engine is higher at

D.high altitudes

Intercooling in multi-stage compressors is done

D.to minimise the work of compression

The ratio of workdone per cycle to the stroke volume of the compressor is known as

D.mean effective pressure

In a single acting reciprocating compressor, the suction, compression and delivery of air takes place in __________ of the piston.

B.two strokes

The capacity of a compressor is expressed in

C.m3/min

The maximum delivery pressure in a rotary air compressor is

A.10 bar

The stagnation pressure rise in a centrifugal compressor takes place

C.in the diffuser and impeller

In a jet propulsion

B.the propulsive matter is caused to flow around the

propelled body

The type of rotary compressor

used in aeroplanes, is of

B.axial flow type

In a reciprocating air compressor, the compression work per kg of air

C.is independent of clearance volume

The degree of reaction in an axial flow compressor is defined as the ratio of static enthalpy rise in the

C.rotor to static enthalpy rise in the stage

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