If the flow of air through the compressor is perpendicular to its axis, then it is a
1.Reciprocating compressor
2.Centrifugal compressor
3.Axial flow compressor
4.Turbo compressor
In a double acting compressor, the air is compressed
1. In one cylinder
2. In two cylinders
3. In a single cylinder on both sides of the piston
4.In two cylinders on both sides of the piston
Separators in compressor installations are located
1.Before inter-cooler
2.After inter-cooler
3.After receiver
4. Between after-cooler and air receiver
The overall thermal efficiency of an ideal gas turbine plant is (where r = Pressure ratio)
1.r ɣ-1
2. 1 - r ɣ-1
3. 1 - (1/r) ɣ-1/ɣ
4.1 - (1/r) ɣ/ɣ-1
. Reciprocating air compressor is best suited for
1.Large quantity of air at high pressure
2.Small quantity of air at high pressure
3. Small quantity of air at low pressure
4.Large quantity of air at low pressure
A compressor mostly used for supercharging of I.C. engines is
1.Radial flow compressor
2. Axial flow compressor
3.Roots blower
4.Reciprocating compressor
After-cooler is used to
1. Cool the air
2.Decrease the delivery temperature for ease in handling
3. Cause moisture and oil vapour to drop out
4.Reduce volume
Gas turbines use following type of air compressor
1. Centrifugal type
2.Reciprocating type
3.Lobe type
4.Axial flow type
In a closed cycle gas turbine, the air is compressed
1.Isothermally
2.Polytropically
3.Isentropically
4.None of these
In a jet propulsion unit, the products of combustion after passing through the gas turbine are discharged into
1.Atmosphere
2.Vacuum
3.Discharge nozzle
4.Back to the compressor
In an axial flow compressor, the ratio of pressure in the rotor blades to the pressure rise in the compressor in one stage is known as
1.Work factor
2. Slip factor
3.Degree of reaction
4.Pressure coefficient
In jet engines, for the efficient production of large power, fuel is burnt in an atmosphere of
1.Vacuum
2.Atmospheric air
3.Compressed air
4.Oxygen alone
In multistage compressor, the isothermal compression is achieved by
1. Employing inter-cooler
2.By constantly cooling the cylinder
3.By running compressor at very slow speed
4. By insulating the cylinder
In the aircraft propellers
1.The propulsive matter is caused to flow around the propelled body
2.Propulsive matter is ejected from within the propelled body
3.Its functioning does not depend on presence of air
4.All of the above
Mining industry usually employs following motive power
1. A.C. electric motor
2.Compressed air
3.Petrol engine
4.Diesel engine
Out of the following, from where you will prefer to take intake for air compressor
1.0.1 bar and 20°C
2.1 bar and 20°C
3.0.1 bar and 40°C
4.1 bar and 40°C
Out of the following, from where you will prefer to take intake for air compressor
1. From an air conditioned room maintained at 20°C
2.From outside atmosphere at 1°C
3. From coal yard side
4.From a side where cooling tower is located nearby
Pick up the correct statement
1.Large gas turbines use radial inflow turbines
2.Gas turbines have their blades similar to steam turbine
3.Gas turbine's blade will appear as impulse section at the hub and as a reaction section at tip
4.Gas turbines use both air and liquid cooling
Pick up the wrong statement
1. Pulse-jet requires no ambient air for propulsion
2. Ramjet engine has no turbine
3.Turbine drives compressor in a Turbojet
4.Bypass turbojet engine increases the thrust without adversely affecting, the propulsive efficiency and fuel economy
Ram compression in turbojet involves
1. Reduction of speed of incoming air and conversion of part of it into pressure energy
2.Compression of inlet air
3. Increasing speed of incoming air
4.Lost work
Reciprocating air compressor is best suited for
1.Large quantity of air at high pressure
2. Small quantity of air at high pressure
3.Small quantity of air at low pressure
4.Large quantity of air at low pressure
Reheating in a multistage expansion gas turbine ________ compressor work.
1.Has no effect on
2.Decreases
3.Increases
4.None of these
Standard air is the air at ________ and relative humidity of 36 percent.
1.0.1 bar and 20°C
2.1 bar and 20°C
3.0.1 bar and 40°C
4.1 bar and 40°C
The area of actual indicator diagram on an air compressor as compared to area of ideal indicator diagram is
1.Less
2.More
3.Same
4.More/less depending on compressor capacity
The capacity of compressor will be highest when its intake temperature is
1. Lowest
2.Highest
3.Anything
4.Atmospheric
The closed cycle in gas turbines
1.Provides lesser flexibility
2.Provides lesser flexibility
3.In never used
4.Is used when gas is to be burnt
The closed cycle in gas turbines
1.Provides greater flexibility
2.Provides lesser flexibility
3. In never used
4.Is used when gas is to be burnt
The compressor capacity is defined as the
1.Actual volume of the air delivered by the compressor when reduced to normal temperature and pressure conditions
2.Volume of air delivered by the compressor
3.Volume of air sucked by the compressor during its suction stroke
4. None of the above
The degree of reaction is usually kept ________ for all types of axial flow compressors.
1.0.2
2.0.3
3. 0.4
4.0.5
The efficiency and work ratio of a gas turbine plant can be increased by
1.Adding heat exchanger
2.Injecting water in/around combustion chamber
3.Reheating the air after partial expansion in the turbine
4.All of the above
The gas in cooling chamber of a closed cycle gas turbine is cooled at
1. Constant volume
2.Constant temperature
3.Constant pressure
4.None of these
The maximum combustion pressure in gas turbine as compared to I.C. engine is
1.More
2.Less
3.Same
4.Depends on other factors
The overall isothermal efficiency of the compressor is defined as the ratio of
1.Work required to compress the air isothermally to the actual work required to compress the air for the same pressure ratio
2. Isothermal power to the shaft power or B.P. of the motor or engine required to drive the compressor
3.Volume of free air delivery per stroke to the swept volume of the piston
4. Isentropic power to the power required to drive the compressor
The reason for volumetric efficiency of reciprocating compressor being less than 100 percent is
1.Pressure drop across the valves
2.Superheating in compressor
3.Clearance volume and leakages
4.All of the above
The volume of air sucked by the compressor during its suction stroke is called
1.Free air delivery
2.Compressor capacity
3.Swept volume
4.None of these
The volumetric efficiency of a compressor
1. Increases with decrease in compression ratio
2.Decreases with decrease in compression ratio
3. Increases with increase in compression ratio
4.Decreases with increase in compression ratio
The work-done on a compressor will be minimum if air is taken from
1.The atmosphere
2.A source at 0° C
3. A source of low temperature air
4.A source of high temperature air
To avoid moisture troubles, the branch connections from compressed air lines should be taken from
1.Top side of main
2.Bottom side of main
3.Left side of main
4.Right side of main
To avoid moisture troubles, the compressed air main line should
1.Rise gradually towards the point of use
2.Drop gradually towards the point of use
3.Be laid vertically
4.Be laid exactly horizontally
When air is to be compressed at a high pressure, then it is advantageous to use
1.Single stage compression
2.Multistage compression without intercooling
3.Multistage compression with intercooling
4.None of these
Which is false statement about multistage compression?
1.Power consumption per unit of air delivered is low
2.Volumetric efficiency is high
3. It is best suited for compression ratios around 7:1
4.The moisture in air is condensed in the inter-cooler
Which of the following statement is correct?
1.The reciprocating compressors are best suited for high pressure and low volume capacity
2.The effect of clearance volume on power consumption is negligible for the same volume of discharge
3.Both (A) and (B)
4.None of these