Compressors, Gas Turbines and Jet Engines MCQs

Question 1

The power available for takeoff and climb in case of turbojet engine as compared to reciprocating engine is

Accepted Answer

Less

Answer

More

Answer

Same

Answer

May be less or more depending on ambient conditions

Question 2

Gas turbines use following type of air compressor

Accepted Answer

Axial flow type

Answer

Centrifugal type

Answer

Reciprocating type

Answer

Lobe type

Question 3

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

Accepted Answer

Pressure slightly less than atmospheric and temperature slightly more than atmospheric

Answer

Atmospheric

Answer

Slightly more than atmospheric

Answer

Slightly less than atmospheric

Question 4

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)

Accepted Answer

$$\frac{{{{	ext{D}}_1}}}{{{{	ext{D}}_2}}} = \frac{{{{	ext{p}}_2}}}{{{{	ext{p}}_1}}}$$

Answer

$$\frac{{{{	ext{D}}_1}}}{{{{	ext{D}}_2}}} = {{	ext{p}}_1}{{	ext{p}}_2}$$

Answer

$$\frac{{{{	ext{D}}_1}}}{{{{	ext{D}}_2}}} = \frac{{{{	ext{p}}_1}}}{{{{	ext{p}}_2}}}$$

Answer

None of these

Question 5

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 $$\left( {\frac{{{{	ext{W}}_1}}}{{{{	ext{W}}_2}}}} ight)$$ with perfect intercooling is given by

Accepted Answer

$$\frac{{{{	ext{W}}_1}}}{{{{	ext{W}}_2}}} = \frac{{{{	ext{n}}_1}\left( {{{	ext{n}}_2} - 1} ight)}}{{{{	ext{n}}_2}\left( {{{	ext{n}}_1} - 1} ight)}}$$

Answer

$$\frac{{{{	ext{W}}_1}}}{{{{	ext{W}}_2}}} = \frac{{{{	ext{n}}_2}\left( {{{	ext{n}}_1} - 1} ight)}}{{{{	ext{n}}_1}\left( {{{	ext{n}}_2} - 1} ight)}}$$

Answer

$$\frac{{{{	ext{W}}_1}}}{{{{	ext{W}}_2}}} = \frac{{{{	ext{n}}_1}}}{{{{	ext{n}}_2}}}$$

Answer

$$\frac{{{{	ext{W}}_1}}}{{{{	ext{W}}_2}}} = \frac{{{{	ext{n}}_2}}}{{{{	ext{n}}_1}}}$$

Question 6

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

Accepted Answer

$$\frac{{{{	ext{D}}_1}}}{{{{	ext{D}}_2}}} = {\left( {\frac{{{{	ext{p}}_3}}}{{{{	ext{p}}_1}}}} ight)^{\frac{1}{4}}}$$

Answer

$$\frac{{{{	ext{D}}_1}}}{{{{	ext{D}}_2}}} = {\left( {{{	ext{p}}_1}{{	ext{p}}_3}} ight)^{\frac{1}{2}}}$$

Answer

$$\frac{{{{	ext{D}}_1}}}{{{{	ext{D}}_2}}} = {\left( {\frac{{{{	ext{p}}_1}}}{{{{	ext{p}}_3}}}} ight)^{\frac{1}{4}}}$$

Answer

$$\frac{{{{	ext{D}}_1}}}{{{{	ext{D}}_2}}} = {\left( {{{	ext{p}}_1}{{	ext{p}}_3}} ight)^{\frac{1}{4}}}$$

Question 7

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

Accepted Answer

Increase

Answer

Decrease

Answer

Remain same

Answer

Does not change

Question 8

In multistage compressor, the isothermal compression is achieved by

Accepted Answer

By running compressor at very slow speed

Answer

Employing inter-cooler

Answer

By constantly cooling the cylinder

Answer

By insulating the cylinder

Question 9

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.

Accepted Answer

Equal to

Answer

Less than

Answer

Greater than

Answer

None of these