MCQOPTIONS
Saved Bookmarks
MCQOPTIONS
This section includes 454 Mcqs, each offering curated multiple-choice questions to sharpen your Mechanical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 251. |
_ Pick up the wrong statement about advantages of multistage compression$? |
| A. | Better lubrication is possible advantages of multistage |
| B. | More loss of air due to leakage past the cylinder |
| C. | Mechanical balance is better |
| D. | Air can be cooled perfectly in between |
| Answer» C. Mechanical balance is better | |
| 252. |
_ More than one stage will be preferred for reciprocating compressor if the delivery pressure is more than$? |
| A. | 2 kg/cm² |
| B. | 6 kg/cm² |
| C. | 10 kg/cm² |
| D. | 14.7 kg/cm² |
| Answer» B. 6 kg/cm¬¨‚⧠| |
| 253. |
_ Gas turbine cycle with regenerator$? |
| A. | Increases thermal efficiency |
| B. | Allows high compression ratio |
| C. | Decreases heat loss is exhaust |
| D. | Allows operation at very high altitudes |
| Answer» B. Allows high compression ratio | |
| 254. |
_ The overall thermal efficiency of an ideal gas turbine plant is (where r = Pressure ratio)$? |
| A. | r …£-1 |
| B. | 1 - r …£-1 |
| C. | 1 - (1/r) …£-1/…£ |
| D. | 1 - (1/r) …£/…£-1 |
| Answer» D. 1 - (1/r) ‚Ķ¬£/‚Ķ¬£-1 | |
| 255. |
_ The ratio of specific weight/h.p. of gas turbine and I.C engines may be typically of the order of$? |
| A. | 1: 1 |
| B. | 2: 1 |
| C. | 4: 1 |
| D. | 1: 6 |
| Answer» E. | |
| 256. |
_ When air is to be compressed at a high pressure, then it is advantageous to use$? |
| A. | Single stage compression |
| B. | Multistage compression without intercooling |
| C. | Multistage compression with intercooling |
| D. | None of these |
| Answer» D. None of these | |
| 257. |
_ The ratio of outlet whirl velocity to blade velocity in case of centrifugal compressor is called$? |
| A. | Slip factor |
| B. | Velocity factor |
| C. | Velocity coefficient |
| D. | None of the above |
| Answer» B. Velocity factor | |
| 258. |
_ The advantage of multistage compression over single stage compression is$? |
| A. | Lower power consumption per unit of air delivered |
| B. | Higher volumetric efficiency |
| C. | Decreased discharge temperature |
| D. | All of the above |
| Answer» E. | |
| 259. |
_ Producer gas is produced by$? |
| A. | Carbonisation of coal |
| B. | Passing steam over incandescent coke |
| C. | Passing air and a large amount of steam over waste coal at about 65°C |
| D. | Partial combustion of coal, coke, anthracite coal or charcoal in a mixed air steam blast |
| Answer» E. | |
| 260. |
_ The maximum temperature in a gas turbine is$? |
| A. | 200°C |
| B. | 500°C |
| C. | 700°C |
| D. | 1000°C |
| Answer» D. 1000¬¨‚àûC | |
| 261. |
_ Reheating in gas turbine results in$? |
| A. | Increase of work ratio |
| B. | Decrease of thermal efficiency |
| C. | Decrease of work ratio |
| D. | Both (A) and (B) above |
| Answer» E. | |
| 262. |
_ In a jet propulsion unit, the products of combustion after passing through the gas turbine are discharged into$? |
| A. | Atmosphere |
| B. | Vacuum |
| C. | Discharge nozzle |
| D. | Back to the compressor |
| Answer» D. Back to the compressor | |
| 263. |
_ The pressure ratio for an open cycle gas turbine compared to closed cycle gas turbine of same h.p. is$? |
| A. | Low |
| B. | High |
| C. | Same |
| D. | Low/high depending on make and type |
| Answer» B. High | |
| 264. |
_ Pick up the correct statement$? |
| A. | Closed cycle gas turbine is an I.C engine |
| B. | Gas turbine uses same working fluid over and over again |
| C. | Ideal efficiency of closed cycle gas turbine plant is more than Carnot cycle efficiency |
| D. | Thrust in turbojet is produced by nozzle exit gases |
| Answer» E. | |
| 265. |
_ The compressor capacity with decrease in suction temperature$? |
| A. | Increases |
| B. | Decreases |
| C. | Remain unaffected |
| D. | May increase or decrease depending on compressor capacity |
| Answer» B. Decreases | |
| 266. |
_ The work ratio of a gas turbine plant is defined as the ratio of$? |
| A. | Net work output and heat supplied |
| B. | Net work output and work done by turbine |
| C. | Actual heat drop and isentropic heat drop |
| D. | Net work output and isentropic heat drop |
| Answer» C. Actual heat drop and isentropic heat drop | |
| 267. |
_ An air receiver is to be placed outside. Should it be placed in$? |
| A. | Sun |
| B. | Shade |
| C. | Rain |
| D. | Enclosed room |
| Answer» C. Rain | |
| 268. |
_ A jet engine works on the principle of conservation of$? |
| A. | Mass |
| B. | Energy |
| C. | Flow |
| D. | Linear momentum |
| Answer» E. | |
| 269. |
_ The stagnation pressure rise in a centrifugal compressor takes place$? |
| A. | In the diffuser only |
| B. | In the impeller only |
| C. | In the diffuser and impeller |
| D. | In the inlet guide vanes only |
| Answer» D. In the inlet guide vanes only | |
| 270. |
_ The temperature of air at the beginning of the compression stroke is ________ the atmospheric temperature.$? |
| A. | Equal to |
| B. | Less than |
| C. | More than |
| D. | None of these |
| Answer» D. None of these | |
| 271. |
_ In jet engines, paraffin is usually used as the fuel because of its$? |
| A. | High calorific value |
| B. | Ease of atomisation |
| C. | Low freezing point |
| D. | Both (A) and (C) above |
| Answer» E. | |
| 272. |
_ Which one of the following is the effect of blade shape on performance of a centrifugal compressor?$? |
| 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. | |
| 273. |
_ In a turbo jet engine, subsequent to heat addition to compressed air, to get the power output, the working substance is expanded in$? |
| A. | Exit nozzle, which is a constant volume process |
| B. | Exit nozzle, which is essentially an isentropic process |
| C. | Turbine blades, which is a constant volume process |
| D. | Turbine blades, which is essentially an isentropic process |
| Answer» E. | |
| 274. |
_ Reciprocating air compressor is best suited for$? |
| A. | Large quantity of air at high pressure |
| B. | Small quantity of air at high pressure |
| C. | Small quantity of air at low pressure |
| D. | Large quantity of air at low pressure |
| Answer» B. Small quantity of air at high pressure | |
| 275. |
_ A large clearance volume in a reciprocating compressor results in$? |
| A. | Reduced volume flow rate |
| B. | Increased volume flow rate |
| C. | Lower suction pressure |
| D. | Lower delivery pressure |
| Answer» B. Increased volume flow rate | |
| 276. |
_ If V, U and Vr represent the absolute velocity of fluid, velocity of blade, and relative velocity of fluid, and suffix ‘I’ and ‘o’ stand for entry and exit conditions, then in a rotary machine whose degree of reaction is unity$? |
| A. | Vi = Vo |
| B. | Vt > Vo |
| C. | U < Vo |
| D. | V = Uo |
| Answer» B. Vt > Vo | |
| 277. |
_ Cylinder clearance in a compressor should be$? |
| A. | As large as possible |
| B. | As small as possible |
| C. | About 50% of swept volume |
| D. | About 100% of swept volume |
| Answer» C. About 50% of swept volume | |
| 278. |
_ Ramjet engine$? |
| A. | Is self operating at zero flight speed |
| B. | Is not self operating at zero flight speed |
| C. | Requires no air for its operation |
| D. | Produces a jet consisting of plasma |
| Answer» C. Requires no air for its operation | |
| 279. |
_ The maximum compression ratio in an actual single stage axial flow compressor is of the order of$? |
| A. | 1 : 1.2 |
| B. | 1 : 2 |
| C. | 1 : 5 |
| D. | 1 : 10 |
| Answer» B. 1 : 2 | |
| 280. |
_ A 3 m³/min compressor means that it$? |
| A. | Compresses 3 m³/min of standard air |
| B. | Compresses 3 m³/ min of free air |
| C. | Delivers 3 m³/ min of compressed air |
| D. | Delivers 3 m³/ min of compressed air at delivery pressure |
| Answer» C. Delivers 3 m¬¨‚â•/ min of compressed air | |
| 281. |
_ The pressure ratio in gas turbines is of the order of$? |
| A. | 2: 1 |
| B. | 4:1 |
| C. | 61: 1 |
| D. | 9: 1 |
| Answer» D. 9: 1 | |
| 282. |
__The propulsive power of the rocket is (where v‚ÇÅ = Jet velocity, and v‚ÇÇ = Aircraft velocity)__ |
| A. | (v₁² -v₂²)/2g |
| B. | (v₁ - v₂)²/2g |
| C. | (v₁² -v₂²)/g |
| D. | (v₁ - v₂)²/g |
| Answer» B. (v‚Äö√á√Ö - v‚Äö√á√á)¬¨‚â§/2g | |
| 283. |
__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 | |
| 284. |
__If the clearance ratio for a reciprocating air compressor is 'K', then its volumetric efficiency is given by__ |
| A. | 1 - k + k (p‚ÇÅ/p‚ÇÇ)1/n |
| B. | 1 + k - k (p‚ÇÇ/p‚ÇÅ)1/n |
| C. | 1 - k + k (p‚ÇÅ/p‚ÇÇ) n- 1/n |
| D. | 1 + k - k (p‚ÇÇ/p‚ÇÅ) n-1/n |
| Answer» C. 1 - k + k (p‚Äö√á√Ö/p‚Äö√á√á) n- 1/n | |
| 285. |
__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 | |
| 286. |
__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. | |
| 287. |
__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 | |
| 288. |
__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 | |
| 289. |
__The power available for takeoff and climb in case of turbojet engine as compared to reciprocating engine is__ |
| A. | Less |
| B. | More |
| C. | Same |
| D. | May be less or more depending on ambient conditions |
| Answer» B. More | |
| 290. |
__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 | |
| 291. |
__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 | |
| 292. |
__For supplying intermittent small quantity of air at high pressure, following compressor is best suited__ |
| A. | Centrifugal |
| B. | Reciprocating |
| C. | Axial |
| D. | Screw |
| Answer» C. Axial | |
| 293. |
__If p‚ÇÅ is the pressure of air entering the L.P, cylinder and p‚ÇÉ 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. | D‚ÇÅ/D‚ÇÇ = (p‚ÇÅ p‚ÇÉ)1/2 |
| B. | D‚ÇÅ/D‚ÇÇ = (p‚ÇÅ/p‚ÇÉ)1/4 |
| C. | D‚ÇÅ/D‚ÇÇ = (p‚ÇÅ p‚ÇÉ)1/4 |
| D. | D‚ÇÅ/D‚ÇÇ = (p‚ÇÉ/p‚ÇÅ)1/4 |
| Answer» E. | |
| 294. |
__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 | |
| 295. |
__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 | |
| 296. |
__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 | |
| 297. |
__In a closed cycle gas turbine, the air is compressed__ |
| A. | Isothermally |
| B. | Polytropically |
| C. | Isentropically |
| D. | None of these |
| Answer» D. None of these | |
| 298. |
__A jet engine has__ |
| A. | No propeller |
| B. | Propeller in front |
| C. | Propeller at back |
| D. | Propeller on the top |
| Answer» B. Propeller in front | |
| 299. |
_Pick up the wrong statement$? |
| A. | Centrifugal compressors deliver practically constant pressure over a considerable range of capacities |
| B. | Axial flow compressors have a substantially constant delivery at variable pressures |
| C. | Centrifugal compressors have a wider stable operating range than axial flow compressors |
| D. | Axial flow compressors are bigger in diameter compared to centrifugal type |
| Answer» E. | |
| 300. |
_The air power of the compressor is also known as$? |
| A. | Indicated power |
| B. | Brake power |
| C. | Frictional power |
| D. | None of these |
| Answer» B. Brake power | |