MCQOPTIONS
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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.
| 151. |
The material commonly used for air craft gas turbine is |
| A. | Stainless steel |
| B. | High alloy steel |
| C. | Duralumin |
| D. | Timken, Haste alloys |
| Answer» E. | |
| 152. |
The degree of reaction is usually kept ________ for all types of axial flow compressors. |
| A. | 0.2 |
| B. | 0.3 |
| C. | 0.4 |
| D. | 0.5 |
| Answer» E. | |
| 153. |
A compressor mostly used for supercharging of I.C. engines is |
| A. | Radial flow compressor |
| B. | Axial flow compressor |
| C. | Roots blower |
| D. | Reciprocating compressor |
| Answer» B. Axial flow compressor | |
| 154. |
The mass of gas turbine per kW developed is about ________ as that of an I.C. engine. |
| A. | Same |
| B. | One-half |
| C. | One fourth |
| D. | One sixth |
| Answer» E. | |
| 155. |
When the temperature of air leaving the inter-cooler, in a two stage compression with inter-cooler, is ________ the original atmospheric air temperature, then the intercooling is known as perfect or complete intercooling. |
| A. | Equal to |
| B. | Less than |
| C. | More than |
| D. | None of these |
| Answer» B. Less than | |
| 156. |
In a compressor, free air delivered is the actual volume delivered at the stated pressure reduced to |
| A. | N.T.P. conditions |
| B. | Intake temperature and pressure conditions |
| C. | 0°C and 1 kg/cm² |
| D. | 20°C and 1 kg/cm² |
| Answer» C. 0°C and 1 kg/cm² | |
| 157. |
The specific output per kg mass flow rate of a gas turbine (having fixed efficiencies of compressor and turbine and fixed higher and lower temperature) with increase in pressure ratio will |
| A. | Increase first at fast rate and then slow |
| B. | Increase first at slow rate and then fast |
| C. | Decrease continuously |
| D. | First increase, reach maximum and then decrease |
| Answer» E. | |
| 158. |
The stagnation pressure rise in a centrifugal compressor takes place |
| A. | In the diffuser only |
| B. | In the impeller only |
| C. | In the diffuser and impeller |
| D. | In the inlet guide vanes only |
| Answer» D. In the inlet guide vanes only | |
| 159. |
The ratio of work-done per cycle to the stroke volume of the compressor is known as |
| A. | Compressor capacity |
| B. | Compression ratio |
| C. | Compressor efficiency |
| D. | Mean effective pressure |
| Answer» E. | |
| 160. |
The volumetric efficiency of compressor with increase in compression ratio will |
| A. | Increase |
| B. | Decrease |
| C. | Remain same |
| D. | May increase or decrease depending on clearance volume |
| Answer» C. Remain same | |
| 161. |
When the outlet angle from the rotor of a centrifugal compressor is more than 90°, then the blades are said to be |
| A. | Forward curved |
| B. | Backward curved |
| C. | Radial |
| D. | None of these |
| Answer» B. Backward curved | |
| 162. |
The temperature of air at the beginning of the compression stroke is ________ the atmospheric temperature. |
| A. | Equal to |
| B. | Less than |
| C. | More than |
| D. | None of these |
| Answer» D. None of these | |
| 163. |
The assumption made in two stage compression with inter-cooler is that |
| A. | There is no pressure drop in the inter-cooler |
| B. | The compression in both the cylinders is polytropic |
| C. | The suction and delivery of air takes place at constant pressure |
| D. | All of the above |
| Answer» E. | |
| 164. |
The volumetric efficiency of a compressor falls roughly as follows for every 100 m increase in elevation |
| A. | 0.1% |
| B. | 0.5% |
| C. | 1.0% |
| D. | 5% |
| Answer» D. 5% | |
| 165. |
Pick up the wrong statement |
| A. | Pulse-jet requires no ambient air for propulsion |
| B. | Ramjet engine has no turbine |
| C. | Turbine drives compressor in a Turbojet |
| D. | Bypass turbojet engine increases the thrust without adversely affecting, the propulsive efficiency and fuel economy |
| Answer» B. Ramjet engine has no turbine | |
| 166. |
The ratio of the increase in pressure in rotor blades to total increase in pressure in the stage is called |
| A. | Pressure ratio |
| B. | Pressure coefficient |
| C. | Degree of reaction |
| D. | Slip factor |
| Answer» D. Slip factor | |
| 167. |
In air compressors, free air delivery means 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» B. Volume of air delivered by the compressor | |
| 168. |
The compressor efficiency is the |
| A. | Isothermal H.P/indicated H.R |
| B. | Isothermal H.P./shaft H.R |
| C. | Total output/air input |
| D. | Compression work/motor input |
| Answer» B. Isothermal H.P./shaft H.R | |
| 169. |
The air entry velocity m a rocket as compared to aircraft is |
| A. | Same |
| B. | More |
| C. | Less |
| D. | Zero |
| Answer» E. | |
| 170. |
Rotary compressors are used for delivering |
| A. | Small quantities of air at high pressures |
| B. | Large quantities of air at high pressures |
| C. | Small quantities of air at low pressures |
| D. | Large quantities of air at low pressures |
| Answer» E. | |
| 171. |
The pressure ratio for an open cycle gas turbine compared to closed cycle gas turbine of same h.p. is |
| A. | Low |
| B. | High |
| C. | Same |
| D. | Low/high depending on make and type |
| Answer» B. High | |
| 172. |
Pick up the false statement |
| A. | Gas turbine is a self starting unit |
| B. | Gas turbine does not require huge quantity of water like steam plant |
| C. | Exhaust losses in gas turbine are high due to large mass flow rate |
| D. | Overall efficiency of gas turbine plant is lower than that of a reciprocating engine |
| Answer» B. Gas turbine does not require huge quantity of water like steam plant | |
| 173. |
In jet engines the products of combustion after passing through the gas turbine are discharged into |
| A. | Atmosphere |
| B. | Back to the compressor |
| C. | Discharge nozzle |
| D. | Vacuum |
| Answer» D. Vacuum | |
| 174. |
In a jet propulsion unit, the products of combustion after passing through the gas turbine are discharged into |
| A. | Atmosphere |
| B. | Vacuum |
| C. | Discharge nozzle |
| D. | Back to the compressor |
| Answer» D. Back to the compressor | |
| 175. |
A compressor at high altitudes will require ________ power. |
| A. | Same |
| B. | Less |
| C. | More |
| D. | None of these |
| Answer» C. More | |
| 176. |
The efficiency of the vane blower is (where W₁ = Workdone due to compression, and W₂ = Workdone due to back flow) |
| A. | W₁/(W₁ + W₂) |
| B. | W₂/(W₁ + W₂) |
| C. | (W₁ + W₂)/W₁ |
| D. | (W₁ + W₂)/W₂ |
| Answer» C. (W₁ + W₂)/W₁ | |
| 177. |
In open cycle turbojet engines used in military aircraft, reheating the exhaust gas from the turbine by burning, more fuel is used to increase the |
| A. | Thrust and range of aircraft |
| B. | Efficiency of the engine |
| C. | Both (A) and (B) |
| D. | None of these |
| Answer» B. Efficiency of the engine | |
| 178. |
The velocity of air entering in a rocket is _________ as compared to an aircraft. |
| A. | Zero |
| B. | Less |
| C. | More |
| D. | Same |
| Answer» B. Less | |
| 179. |
An air receiver is to be placed outside. Should it be placed in |
| A. | Sun |
| B. | Shade |
| C. | Rain |
| D. | Enclosed room |
| Answer» C. Rain | |
| 180. |
The working fluid in a turbine is |
| A. | In two phases |
| B. | In three phases |
| C. | In a single phase |
| D. | In the form of air and water mixture |
| Answer» D. In the form of air and water mixture | |
| 181. |
The minimum work required for a three stage reciprocating air compressor is ________ the work required for each stage. |
| A. | Equal to |
| B. | Double |
| C. | Three times |
| D. | Six times |
| Answer» D. Six times | |
| 182. |
In jet engines, for the efficient production of large power, fuel is burnt in an atmosphere of |
| A. | Vacuum |
| B. | Atmospheric air |
| C. | Compressed air |
| D. | Oxygen alone |
| Answer» D. Oxygen alone | |
| 183. |
Which of the following plants is smallest and lightest for generating a given amount of power? |
| A. | Gas turbine plant |
| B. | Petrol engine |
| C. | Diesel engine |
| D. | Solar plant |
| Answer» B. Petrol engine | |
| 184. |
The maximum propulsion efficiency of a turbojet is attained at around following speed |
| A. | 550 km/hr |
| B. | 1050 km/hr |
| C. | 1700 km/hr |
| D. | 2400 km/hr |
| Answer» E. | |
| 185. |
The overall isothermal efficiency of compressor is defined as the ratio of |
| A. | Isothermal h.p. to the BHP of motor |
| B. | Isothermal h.p. to adiabatic h.p. |
| C. | Power to drive compressor to isothermal h.p. |
| D. | Work to compress air isothermally to work for actual compression |
| Answer» B. Isothermal h.p. to adiabatic h.p. | |
| 186. |
The overall isothermal efficiency of the compressor is defined as the ratio of |
| A. | Work required to compress the air isothermally to the actual work required to compress the air for the same pressure ratio |
| B. | Isothermal power to the shaft power or B.P. of the motor or engine required to drive the compressor |
| C. | Volume of free air delivery per stroke to the swept volume of the piston |
| D. | Isentropic power to the power required to drive the compressor |
| Answer» C. Volume of free air delivery per stroke to the swept volume of the piston | |
| 187. |
The compressed air may be used |
| A. | In gas turbine plants |
| B. | For operating pneumatic drills |
| C. | In starting and supercharging of I.C. engines |
| D. | All of the above |
| Answer» E. | |
| 188. |
An after-cooler is used to |
| A. | Remove impurities from air |
| B. | Reduce volume of air |
| C. | Cause moisture and oil vapour to drop out |
| D. | Cool the air |
| Answer» D. Cool the air | |
| 189. |
The mean effective pressure of the compressor is 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» E. | |
| 190. |
In gas turbines, high thermal efficiency is obtained in |
| A. | Closed cycle |
| B. | Open cycle |
| C. | Both of the above |
| D. | Closed/open depending on other considerations |
| Answer» B. Open cycle | |
| 191. |
Water gas is produced by |
| A. | Carbonisation of coal |
| B. | Passing steam over incandescent coke |
| C. | Passing air and a large amount of steam over waste coal at about 65°C |
| D. | Partial combustion of coal, eke, anthracite coal or charcoal in a mixed air steam blast |
| Answer» C. Passing air and a large amount of steam over waste coal at about 65°C | |
| 192. |
Producer gas is produced by |
| A. | Carbonisation of coal |
| B. | Passing steam over incandescent coke |
| C. | Passing air and a large amount of steam over waste coal at about 65°C |
| D. | Partial combustion of coal, coke, anthracite coal or charcoal in a mixed air steam blast |
| Answer» E. | |
| 193. |
Gas turbines for power generation are normally used |
| A. | To supply base load requirements |
| B. | To supply peak load requirements |
| C. | To enable start thermal power plant |
| D. | In emergency |
| Answer» C. To enable start thermal power plant | |
| 194. |
Gas turbine as compared to internal combustion engine |
| A. | Can be driven at a very high speed |
| B. | Produces uniform torque |
| C. | Has more efficiency |
| D. | All of these |
| Answer» E. | |
| 195. |
In a turbo jet engine, subsequent to heat addition to compressed air, to get the power output, the working substance is expanded in |
| A. | Exit nozzle, which is a constant volume process |
| B. | Exit nozzle, which is essentially an isentropic process |
| C. | Turbine blades, which is a constant volume process |
| D. | Turbine blades, which is essentially an isentropic process |
| Answer» E. | |
| 196. |
The gas in cooling chamber of a closed cycle gas turbine is cooled at |
| A. | Constant volume |
| B. | Constant temperature |
| C. | Constant pressure |
| D. | None of these |
| Answer» D. None of these | |
| 197. |
Work ratio of a gas turbine may be improved by |
| A. | Decreasing the compression work |
| B. | Increasing the compression work |
| C. | Increasing the turbine work |
| D. | Both (A) and (C) above |
| Answer» E. | |
| 198. |
The reason for volumetric efficiency of reciprocating compressor being less than 100 percent is |
| A. | Pressure drop across the valves |
| B. | Superheating in compressor |
| C. | Clearance volume and leakages |
| D. | All of these |
| Answer» E. | |
| 199. |
In a jet engine, the air-fuel ratio is |
| A. | 30:1 |
| B. | 40:1 |
| C. | 50:1 |
| D. | 60:1 |
| Answer» E. | |
| 200. |
The overall efficiency of the compressed air system is the |
| A. | Ratio of shaft output of the air motor to the shaft input to the compressor |
| B. | Ratio of shaft input to the compressor to the shaft output of air motor |
| C. | Product of shaft output of air motor and shaft input to the compressor |
| D. | None of the above |
| Answer» B. Ratio of shaft input to the compressor to the shaft output of air motor | |