Compressors, Gas Turbines And Jet Engines MCQ Questions & Answers

1

The pressure and temperature conditions of air at the suction of compressor are

A) Atmospheric B) Slightly more than atmospheric C) Slightly less than atmospheric D) Pressure slightly less than atmospheric and temperature slightly more than atmospheric

Discuss

Answer & Solution

Answer: Option D

Solution:

The pressure and temperature conditions of air at the suction of compressor are Pressure slightly less than atmospheric and temperature slightly more than atmospheric

2

If p₁, is the pressure of air entering the L.P. cylinder and p₂ is the pressure of air leaving the L.P. cylinder (or inter-cooler pressure), then the ratio of cylinder diameters for a single acting, two stage reciprocating air compressor with complete intercooling is given by (where D₁ = Diameter of L.P. cylinder and D₂ = Diameter of H.P. cylinder)

A) $$\frac{{{{\text{D}}_1}}}{{{{\text{D}}_2}}} = {{\text{p}}_1}{{\text{p}}_2}$$ B) $$\frac{{{{\text{D}}_1}}}{{{{\text{D}}_2}}} = \frac{{{{\text{p}}_1}}}{{{{\text{p}}_2}}}$$ C) $$\frac{{{{\text{D}}_1}}}{{{{\text{D}}_2}}} = \frac{{{{\text{p}}_2}}}{{{{\text{p}}_1}}}$$ D) None of these

Discuss

Answer & Solution

Answer: Option C

Solution:

If p₁, is the pressure of air entering the L.P. cylinder and p₂ is the pressure of air leaving the L.P. cylinder (or inter-cooler pressure), then the ratio of cylinder diameters for a single acting, two stage reciprocating air compressor with complete intercooling is given by $$\frac{{{{\text{D}}_1}}}{{{{\text{D}}_2}}} = \frac{{{{\text{p}}_2}}}{{{{\text{p}}_1}}}$$
Where,
D₁ = Diameter of L.P. cylinder,
D₂ = Diameter of H.P. cylinder

3

In n₁ and n₂ are the indices of compression for the first and second stage of compression, then the ratio of work-done on the first and second stages $$\left( {\frac{{{{\text{W}}_1}}}{{{{\text{W}}_2}}}} \right)$$ with perfect intercooling is given by

A) $$\frac{{{{\text{W}}_1}}}{{{{\text{W}}_2}}} = \frac{{{{\text{n}}_2}\left( {{{\text{n}}_1} - 1} \right)}}{{{{\text{n}}_1}\left( {{{\text{n}}_2} - 1} \right)}}$$ B) $$\frac{{{{\text{W}}_1}}}{{{{\text{W}}_2}}} = \frac{{{{\text{n}}_1}\left( {{{\text{n}}_2} - 1} \right)}}{{{{\text{n}}_2}\left( {{{\text{n}}_1} - 1} \right)}}$$ C) $$\frac{{{{\text{W}}_1}}}{{{{\text{W}}_2}}} = \frac{{{{\text{n}}_1}}}{{{{\text{n}}_2}}}$$ D) $$\frac{{{{\text{W}}_1}}}{{{{\text{W}}_2}}} = \frac{{{{\text{n}}_2}}}{{{{\text{n}}_1}}}$$

Discuss

Answer & Solution

Answer: Option B

Solution:

In n₁ and n₂ are the indices of compression for the first and second stage of compression, then the ratio of work-done on the first and second stages $$\left( {\frac{{{{\text{W}}_1}}}{{{{\text{W}}_2}}}} \right)$$ with perfect intercooling is given by $$\frac{{{{\text{W}}_1}}}{{{{\text{W}}_2}}} = \frac{{{{\text{n}}_1}\left( {{{\text{n}}_2} - 1} \right)}}{{{{\text{n}}_2}\left( {{{\text{n}}_1} - 1} \right)}}$$

4

If p₁ is the pressure of air entering the L.P. cylinder and p₃ is the pressure of air leaving the H.P. cylinder, then the ratio of cylinder diameters for a single acting, two stage reciprocating compressor with complete intercooling is given by

A) $$\frac{{{{\text{D}}_1}}}{{{{\text{D}}_2}}} = {\left( {{{\text{p}}_1}{{\text{p}}_3}} \right)^{\frac{1}{2}}}$$ B) $$\frac{{{{\text{D}}_1}}}{{{{\text{D}}_2}}} = {\left( {\frac{{{{\text{p}}_1}}}{{{{\text{p}}_3}}}} \right)^{\frac{1}{4}}}$$ C) $$\frac{{{{\text{D}}_1}}}{{{{\text{D}}_2}}} = {\left( {{{\text{p}}_1}{{\text{p}}_3}} \right)^{\frac{1}{4}}}$$ D) $$\frac{{{{\text{D}}_1}}}{{{{\text{D}}_2}}} = {\left( {\frac{{{{\text{p}}_3}}}{{{{\text{p}}_1}}}} \right)^{\frac{1}{4}}}$$

Discuss

Answer & Solution

Answer: Option D

Solution:

If p₁ is the pressure of air entering the L.P. cylinder and p₃ is the pressure of air leaving the H.P. cylinder, then the ratio of cylinder diameters for a single acting, two stage reciprocating compressor with complete intercooling is given by $$\frac{{{{\text{D}}_1}}}{{{{\text{D}}_2}}} = {\left( {\frac{{{{\text{p}}_3}}}{{{{\text{p}}_1}}}} \right)^{\frac{1}{4}}}$$

5

Volumetric efficiency of a compressor decreases with ________ in compression ratio.

A) Decrease B) Increase C) Remain same D) Does not change

Discuss

Answer & Solution

Answer: Option B

Solution:

Volumetric efficiency of a compressor decreases with increase in compression ratio.

6

In multistage compressor, the isothermal compression is achieved by

A) Employing inter-cooler B) By constantly cooling the cylinder C) By running compressor at very slow speed D) By insulating the cylinder

Discuss

Answer & Solution

Answer: Option C

Solution:

In multistage compressor, the isothermal compression is achieved by running compressor at very slow speed

7

In a single stage, single acting reciprocating air compressor, without clearance, the work-done on the air during isentropic compression is ________ the heat required to raise the temperature of air from T₁ to T₂ at a constant pressure.

A) Equal to B) Less than C) Greater than D) None of these

Discuss

Answer & Solution

Answer: Option A

Solution:

In a single stage, single acting reciprocating air compressor, without clearance, the work-done on the air during isentropic compression is equal to the heat required to raise the temperature of air from T₁ to T₂ at a constant pressure.

8

Out of the following, from where you will prefer to take intake for air compressor

A) From an air conditioned room maintained at 20°C B) From outside atmosphere at 1°C C) From coal yard side D) From a side where cooling tower is located nearby

Discuss

Answer & Solution

Answer: Option D

Solution:

Out of the following, from where you will prefer to take intake for air compressor From a side where cooling tower is located nearby

9

For supplying intermittent small quantity of air at high pressure, following compressor is best suited

A) Centrifugal B) Reciprocating C) Axial D) Screw

Discuss

Answer & Solution

Answer: Option B

Solution:

For supplying intermittent small quantity of air at high pressure, reciprocating compressor is best suited

10

The thrust on the rotor in a centrifugal compressor is produced by

A) Radial component B) Axial component C) Tangential component D) None of the above

Discuss

Answer & Solution

Answer: Option B

Solution:

The thrust on the rotor in a centrifugal compressor is produced by axial component

Compressors, Gas Turbines And Jet Engines MCQ Questions & Answers | Mechanical Engineering