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MCQOPTIONS
This section includes 327 Mcqs, each offering curated multiple-choice questions to sharpen your GATE (Mechanical Engineering) knowledge and support exam preparation. Choose a topic below to get started.
| 101. |
The work ratio of simple gas turbine cycle depends on |
| A. | Pressure ratio |
| B. | Maximum cycle temperature |
| C. | Minimum cycle temperature |
| D. | All of the above |
| Answer» E. | |
| 102. |
Reheating in a multistage expansion gas turbine ________ compressor work. |
| A. | Has no effect on |
| B. | Decreases |
| C. | Increases |
| D. | None of these |
| Answer» C. Increases | |
| 103. |
Compression efficiency is compared against |
| A. | Ideal compression |
| B. | Adiabatic compression |
| C. | Isentropic compression |
| D. | Isothermal compression |
| Answer» E. | |
| 104. |
For a two stage compressor, if index of compression for higher stage is greater than index of compression for lower stage, then the optimum pressure as compared to ideal case will |
| A. | Increase |
| B. | Decrease |
| C. | Remain unaffected |
| D. | Other factors control it |
| Answer» B. Decrease | |
| 105. |
The process, which causes the air to enter the impeller blades of a centrifugal compressor at ________ velocity (without effecting the mass of air to flow and velocity of flow) is known as prewhirl. |
| A. | Reduced |
| B. | Increased |
| C. | Zero |
| D. | None of these |
| Answer» B. Increased | |
| 106. |
Isothermal compression efficiency can be attained by running the compressor |
| A. | At very high speed |
| B. | At very slow speed |
| C. | At average speed |
| D. | At zero speed |
| Answer» C. At average speed | |
| 107. |
The efficiency of roots blower ________ with the increase in pressure ratio. |
| A. | Decreases |
| B. | Increases |
| C. | Does not change |
| D. | None of these |
| Answer» B. Increases | |
| 108. |
The work done per unit mass of air in compression will be least when 'n' is equal to |
| A. | 1 |
| B. | 1.2 |
| C. | 1.3 |
| D. | 1.4 |
| Answer» B. 1.2 | |
| 109. |
Ratio of compression is the ratio of |
| A. | Gauge discharge pressure to the gauge intake pressure |
| B. | Absolute discharge pressure to the absolute intake pressure |
| C. | Pressures at discharge and suction corresponding to same temperature |
| D. | Stroke volume and clearance volume |
| Answer» C. Pressures at discharge and suction corresponding to same temperature | |
| 110. |
Adiabatic compression is one in which |
| A. | Temperature during compression remains constant |
| B. | No heat leaves or enters the compressor cylinder during compression |
| C. | Temperature rise follows a linear relationship |
| D. | Work done is maximum |
| Answer» C. Temperature rise follows a linear relationship | |
| 111. |
Euler's equation can be used for |
| A. | Radial flow compressors |
| B. | Axial flow compressors |
| C. | Pumps |
| D. | All of these |
| Answer» E. | |
| 112. |
The thrust of a jet propulsion power unit can be increased by |
| A. | Injecting water into the compressor |
| B. | Burning fuel after gas turbine |
| C. | Injecting ammonia into the combustion chamber |
| D. | All of the above |
| Answer» E. | |
| 113. |
The efficiency and work ratio of a gas turbine plant can be increased by |
| A. | Adding heat exchanger |
| B. | Injecting water in/around combustion chamber |
| C. | Reheating the air after partial expansion in the turbine |
| D. | All of the above |
| Answer» E. | |
| 114. |
Inter-cooling in multistage compressors is done |
| A. | To cool the air during compression |
| B. | To cool the air at delivery |
| C. | To enable compression in two stages |
| D. | To minimize the work of compression |
| Answer» E. | |
| 115. |
For maximum work, the reheating should be done to an intermediate pressure of (Where p₁ = Maximum pressure, and p₂ = Minimum pressure) |
| A. | (p₁ - p₂)/2 |
| B. | (p₁ + p₂)/2 |
| C. | p₁/p₂ |
| D. | p₁ p₂ |
| Answer» E. | |
| 116. |
With the decrease in compression ratio, the volumetric efficiency |
| A. | Does not change |
| B. | Increases |
| C. | Decreases |
| D. | First decrease and then increase |
| Answer» C. Decreases | |
| 117. |
In which case the air-fuel ratio is likely to be maximum? |
| A. | Gas turbine |
| B. | 4-stroke petrol engine |
| C. | 4-stroke diesel engine |
| D. | Multi cylinder engine |
| Answer» B. 4-stroke petrol engine | |
| 118. |
An ideal air compressor cycle with clearance on P-V diagram can be represented by following processes |
| A. | One adiabatic, two isobaric, and one constant volume |
| B. | Two adiabatic and two isobaric |
| C. | Two adiabatic, one isobaric and one constant volume |
| D. | One adiabatic, one isobaric and two constant volumes |
| Answer» C. Two adiabatic, one isobaric and one constant volume | |
| 119. |
An ideal air compressor cycle without clearance on P-V diagram can be represented by following processes |
| A. | One adiabatic, two isobaric, and one constant volume |
| B. | Two adiabatic and two isobaric |
| C. | Two adiabatic, one isobaric and one constant volume |
| D. | One adiabatic, one isobaric and two constant volumes |
| Answer» B. Two adiabatic and two isobaric | |
| 120. |
In a centrifugal compressor, the ratio of the ________ to the blade velocity is called slip factor. |
| A. | Inlet whirl velocity |
| B. | Outlet whirl velocity |
| C. | Inlet velocity of flow |
| D. | Outlet velocity of flow |
| Answer» E. | |
| 121. |
For slow speed large capacity compressor, following type of valve will be best suited |
| A. | Poppet valve |
| B. | Mechanical valve of the Corliss, sleeve, rotary or semi rotary type |
| C. | Disc or feather type |
| D. | Any of the above |
| Answer» D. Any of the above | |
| 122. |
It is not possible to use closed gas turbine cycle in aeronautical engines because |
| A. | It is inefficient |
| B. | It is bulky |
| C. | It requires cooling water for its operation |
| D. | None of the above |
| Answer» D. None of the above | |
| 123. |
In a high pressure compressor, the delivery pressure is |
| A. | 1 to 5 bar |
| B. | 5 to 8 bar |
| C. | 8 to 10 bar |
| D. | 10 to 15 bar |
| Answer» D. 10 to 15 bar | |
| 124. |
The most efficient method of compressing air is to compress it |
| A. | Isothermally |
| B. | Adiabatically |
| C. | Isentropically |
| D. | Isochronically |
| Answer» B. Adiabatically | |
| 125. |
In a centrifugal compressor, the flow of air is ________ to the axis of compressor. |
| A. | Parallel |
| B. | Perpendicular |
| C. | Inclined |
| D. | None of these |
| Answer» C. Inclined | |
| 126. |
In a single stage, single acting reciprocating air compressor, without clearance volume, the work-done is minimum during |
| A. | Isothermal compression |
| B. | Isentropic compression |
| C. | Polytropic compression |
| D. | None of these |
| Answer» B. Isentropic compression | |
| 127. |
In a single stage, single acting reciprocating air compressor without clearance volume, the work-done is maximum during |
| A. | Isothermal compression |
| B. | Isentropic compression |
| C. | Polytropic compression |
| D. | None of these |
| Answer» C. Polytropic compression | |
| 128. |
The compressor capacity is defined as the |
| A. | Actual volume of the air delivered by the compressor when reduced to normal temperature and pressure conditions |
| B. | Volume of air delivered by the compressor |
| C. | Volume of air sucked by the compressor during its suction stroke |
| D. | None of the above |
| Answer» C. Volume of air sucked by the compressor during its suction stroke | |
| 129. |
Euler's equation is applicable for |
| A. | Centrifugal compressor |
| B. | Axial compressor |
| C. | Pumps |
| D. | All of the above |
| Answer» E. | |
| 130. |
The propulsive power of the rocket is (where v₁ = Jet velocity, and v₂ = Aircraft velocity) |
| A. | (v₁² -v₂²)/2g |
| B. | (v₁ - v₂)²/2g |
| C. | (v₁² -v₂²)/g |
| D. | (v₁ - v₂)²/g |
| Answer» B. (v₁ - v₂)²/2g | |
| 131. |
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 |
| Answer» E. | |
| 132. |
During base load operation, the best method of controlling compressor is |
| A. | Start-stop motor |
| B. | Constant speed unloader |
| C. | Relief valve |
| D. | Variable speed |
| Answer» B. Constant speed unloader | |
| 133. |
A closed cycle gas turbine consists of a |
| A. | Compressor |
| B. | Heating chamber |
| C. | Cooling chamber |
| D. | All of these |
| Answer» E. | |
| 134. |
The thermal efficiency of a simple gas turbine for a given turbine inlet temperature with increase in pressure ratio |
| A. | Increases |
| B. | Decreases |
| C. | First increases and then decreases |
| D. | First decreases and then increases |
| Answer» B. Decreases | |
| 135. |
Axial flow compressor has the following advantage over centrifugal compressor |
| A. | Larger air handling ability per unit frontal area |
| B. | Higher pressure ratio per stage |
| C. | Aerofoil blades are used |
| D. | Higher average velocities |
| Answer» B. Higher pressure ratio per stage | |
| 136. |
If the clearance ratio for a reciprocating air compressor is 'K', then its volumetric efficiency is given by |
| A. | 1 - k + k (p₁/p₂)1/n |
| B. | 1 + k - k (p₂/p₁)1/n |
| C. | 1 - k + k (p₁/p₂) n- 1/n |
| D. | 1 + k - k (p₂/p₁) n-1/n |
| Answer» C. 1 - k + k (p₁/p₂) n- 1/n | |
| 137. |
In a centrifugal compressor, the highest Mach number leading to shock wave in the fluid flow occurs at |
| A. | Diffuser inlet radius |
| B. | Diffuser outlet radius |
| C. | Impeller inlet radius |
| D. | Impeller outlet radius |
| Answer» C. Impeller inlet radius | |
| 138. |
The area of actual indicator diagram on an air compressor as compared to area of ideal indicator diagram is |
| A. | Less |
| B. | More |
| C. | Same |
| D. | More/less depending on compressor capacity |
| Answer» C. Same | |
| 139. |
The volumetric efficiency of a compressor falls roughly as follows for every 5°C increase in atmospheric temperature |
| A. | 0.1% |
| B. | 0.5% |
| C. | 1% |
| D. | 5% |
| Answer» D. 5% | |
| 140. |
Maximum work is done in compressing air when the compression is |
| A. | Isothermal |
| B. | Adiabatic |
| C. | Polytropic |
| D. | None of the above |
| Answer» C. Polytropic | |
| 141. |
The performance of air compressor at high altitudes will be ________ as compared to that at sea level. |
| A. | Same |
| B. | Lower |
| C. | Higher |
| D. | None of these |
| Answer» C. Higher | |
| 142. |
The degree of reaction in an axial flow compressor is defined as the ratio of static enthalpy rise in the |
| A. | Rotor to static enthalpy rise in the stator |
| B. | Stator to static enthalpy rise in the rotor |
| C. | Rotor to static enthalpy rise in the stage |
| D. | Stator to static enthalpy rise in the stage |
| Answer» D. Stator to static enthalpy rise in the stage | |
| 143. |
The efficiency of a jet engine is higher at |
| A. | Low speeds |
| B. | High speeds |
| C. | Low altitudes |
| D. | High altitudes |
| Answer» E. | |
| 144. |
A simple turbojet engine is basically |
| A. | A propeller system |
| B. | Gas turbine engine equipped with a propulsive nozzle and diffuse |
| C. | Chemical rocket engine |
| D. | Ramjet engine |
| Answer» C. Chemical rocket engine | |
| 145. |
The degree of reaction of an axial flow turbine is the ratio of isentropic temperature drop in a blade row to the |
| A. | Adiabatic temperature drop in the stage |
| B. | Total temperature drop |
| C. | Total temperature drop in the stage |
| D. | Total adiabatic temperature drop |
| Answer» D. Total adiabatic temperature drop | |
| 146. |
Rotary compressors are suitable for |
| A. | Large discharge at high pressure |
| B. | Low discharge at high pressure |
| C. | Large discharge at low pressure |
| D. | Low discharge at low pressure |
| Answer» D. Low discharge at low pressure | |
| 147. |
1 m of air at atmospheric condition weighs approximately |
| A. | 0.5 kg |
| B. | 1.0 kg |
| C. | 1.3 kg |
| D. | 2.2 kg |
| Answer» D. 2.2 kg | |
| 148. |
The following property is most important for material used for gas turbine blade |
| A. | Toughness |
| B. | Fatigue |
| C. | Creep |
| D. | Corrosion resistance |
| Answer» D. Corrosion resistance | |
| 149. |
Intercooling in gas turbines |
| A. | Decreases net output but increases thermal efficiency |
| B. | Increases net output but decreases thermal efficiency |
| C. | Decreases net output and thermal efficiency both |
| D. | Increases net output and thermal efficiency both |
| Answer» E. | |
| 150. |
Which one of the following is the effect of blade shape on performance of a centrifugal compressor? |
| A. | Backward curved blades has poor efficiency |
| B. | Backward curved blades lead to stable performance |
| C. | Forward curved blades has higher efficiency |
| D. | Forward curved blades produce lower pressure ratio |
| Answer» E. | |