Question 1

Two-stage reciprocating air compressor: work per cycle composition  Consider a two-stage reciprocating air compressor. The total work done per cycle equals what combination of stage works? Choose the correct statement.

Accepted Answer

Concept/Approach Each cycle comprises compression (and associated processes) in the low-pressure (L.P.) stage plus in the high-pressure (H.P.) stage. The indicated work per cycle is the sum of the indicated works of both stages, accounting for intercooling and valve actions. Final Answer Equal to the sum of works in L.P. and H.P. cylinders

Question 2

Compressor capacity at standard conditions (FAD concept)  Statement: The actual volume of air delivered by a compressor, reduced to normal (standard) temperature and pressure conditions, is called the compressor capacity. Decide whether the statemen…

Accepted Answer

Concept/Approach Compressor capacity is commonly specified as free air delivery (FAD), i.e., the volumetric flow rate referred to standard temperature and pressure. Therefore the statement is correct. Final Answer True

Question 3

Application range of rotary compressors: flow rate and pressure level  Rotary (positive-displacement or dynamic) compressors are typically selected to deliver which combination of flow and pressure? Choose the best description.

Accepted Answer

Concept/Approach Rotary machines (roots, screw, centrifugal, axial) are well suited for large flow rates. In typical single-stage practice, they achieve moderate to low pressures compared with multistage reciprocating compressors used for very high pressures. Final Answer Large quantities of air at low pressures

Question 4

Compressor type used in gas turbines: identify the rotary compressor  Gas turbines (especially aircraft and large power units) primarily use which type of rotary compressor? Choose the correct option.

Accepted Answer

Concept/Approach Modern aircraft and heavy-duty gas turbines predominantly use axial-flow compressors for their high mass-flow capability and good efficiency at high pressure ratios via multistaging. (Small/industrial units may use centrifugal stages, but axial flow is the standard for large engines.) Final Answer Axial-flow type

Question 5

How compressor capacity is expressed: choose the standard unit  Compressor capacity is normally stated as a volumetric flow rate at standard (or specified) conditions. Select the correct unit.

Accepted Answer

Concept/Approach Capacity is a volumetric flow quantity, typically reported as m³/min (or m³/s, cfm) referred to standard conditions (FAD basis). Final Answer m³/min

Question 6

Axial-flow compressor operating regime: statement on best performance  Statement: An axial compressor gives its optimum performance at high rotational speeds and large volume flows. Decide whether the statement is correct.

Accepted Answer

Concept/Approach Axial-flow compressors are favored for high mass-flow applications and achieve good efficiency at high blade tip speeds (high rpm), handling large volume flows through multiple stages. Final Answer True

Question 7

Effect of large clearance volume in a reciprocating compressor  If the clearance volume of a reciprocating compressor is large, what is the primary effect on delivered flow? Choose the correct outcome.

Accepted Answer

Concept/Approach A larger clearance volume increases the fraction of residual compressed air that re-expands during the suction stroke, reducing the volumetric efficiency. As a result, the net fresh air inducted (and thus delivered volume flow) decreases. Common pitfall Confusing volumetric efficiency with pressure ratio; clearance volume primarily affects capacity, not the set pressure ratio (which is governed by system resistance and valve behavior). Final Answer Reduced volume flow rate

Question 8

Gas-turbine intercooling: effect on net work and thermal efficiency.  Consider a simple gas turbine where intercooling is applied only between multistage compressors (no reheat and no recuperator). Assume the same compressor pressure ratio, the same…

Accepted Answer

Concept/Approach Intercooling between compressor stages lowers the work of compression, so turbine work minus compressor work (net output) increases. However, the air then enters the combustor at a lower temperature, so for the same turbine inlet temperature more fuel (heat input) is needed and the average temperature of heat addition drops, leading to a lower thermal efficiency for a simple (unrecuperated) cycle. Result Net output ↑, Thermal efficiency ↓. Final Answer increases net output but decreases thermal efficiency.

Question 9

Rotary compressors: suitability for flow rate and pressure level.  Evaluate the statement about application range: rotary compressors are preferred when a large volume flow is needed at relatively low delivery pressure. Decide if this statement is c…

Accepted Answer

Concept/Approach Rotary (centrifugal/axial/rotary vane/roots) compressors are commonly used for large volumetric flow rates at modest pressure ratios, where reciprocating compressors become bulky and pulsating. Hence the statement is correct. Final Answer Agree.

Question 10

Compressor definitions: identify the correct efficiency term.  Definition target: the ratio of free air delivery (at standard condition) per stroke to the piston's swept volume. Select the correct name of this ratio.

Accepted Answer

Given Ratio = (Free air delivered per stroke at NTP)/(Swept volume of piston). Concept This ratio measures how effectively the cylinder volume is filled with air referenced to standard conditions; the standard term is volumetric efficiency. Final Answer volumetric efficiency.

Question 11

Gas turbine as compared to internal combustion engine

Accepted Answer

all of these

Question 12

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

Accepted Answer

diffuser outlet radius

Question 13

In a gas turbine, air is obtained from the atmosphere and compressed in an air compressor.

Accepted Answer

True

Question 14

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

D1/D2 = (p3/p1)1/4

Question 15

The air is delivered __________ in one revolution in case of a three-lobbed rotor.

Accepted Answer

six times

Question 16

Maximum work is saved in a two stage reciprocating air compressor with incomplete intercooling.

Accepted Answer

Disagree

Question 17

In a compressor, work is done on the piston during suction of air and work is done by the piston during compression as well as delivery of air.

Accepted Answer

Agree

Question 18

A receiver in compressor installations is used to damp pressure waves in compressor discharge.

Accepted Answer

Yes

Question 19

A gas turbine used in air-craft should have low weight and small frontal area.

Accepted Answer

Correct

Question 20

A jet engine has

Accepted Answer

no propeller

Compressors, Gas Dynamics and Gas Turbines Questions