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.
| 51. |
The pressure of air at the beginning of the compression stroke is ________ the atmospheric pressure. |
| A. | Equal to |
| B. | Less than |
| C. | More than |
| D. | None of these |
| Answer» C. More than | |
| 52. |
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 m³/ min of compressed air | |
| 53. |
Separators are generally used in air compressor installations |
| A. | Before the inter-cooler |
| B. | After the inter-cooler |
| C. | Between the after-cooler and receiver |
| D. | Before first stage suction |
| Answer» D. Before first stage suction | |
| 54. |
The inlet pressure is always ________ the discharge pressure. |
| A. | Equal to |
| B. | Less than |
| C. | More than |
| D. | None of these |
| Answer» C. More than | |
| 55. |
The type of rotary compressor used in gas turbines, is of |
| A. | Centrifugal type |
| B. | Axial flow type |
| C. | Radial flow type |
| D. | None of these |
| Answer» C. Radial flow type | |
| 56. |
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 | |
| 57. |
Maximum temperature in a gas turbine is of the order of |
| A. | 700°C |
| B. | 2000°C |
| C. | 1500°C |
| D. | 1000°C |
| Answer» B. 2000°C | |
| 58. |
Maximum delivery pressure is a rotary air compressor is of the order of |
| A. | 6 kg/cm² |
| B. | 10 kg/cm² |
| C. | 16 kg/cm² |
| D. | 25 kg/cm² |
| Answer» C. 16 kg/cm² | |
| 59. |
The output of a gas turbine is 300 KW and its efficiency is 20 percent, the heat supplied is |
| A. | 6000 KW |
| B. | 15 KW |
| C. | 600 KW |
| D. | 150 KW |
| Answer» C. 600 KW | |
| 60. |
There is a certain pressure ratio (optimum) for a gas turbine at which its thermal efficiency is maximum. With increase in turbine temperature, the value of pressure ratio for the peak efficiency would |
| A. | Remain same |
| B. | Decrease |
| C. | Increase |
| D. | None of the above |
| Answer» D. None of the above | |
| 61. |
The ideal efficiency of simple gas turbine cycle depends on |
| A. | Pressure ratio |
| B. | Maximum cycle temperature |
| C. | Minimum cycle temperature |
| D. | All of the above |
| Answer» B. Maximum cycle temperature | |
| 62. |
In a four stage compressor, if the pressure at the first and third stage is 1 bar and 16 bar, then the delivery pressure at the fourth stage will be |
| A. | 1 bar |
| B. | 16 bar |
| C. | 64 bar |
| D. | 256 bar |
| Answer» D. 256 bar | |
| 63. |
In air breathing jet engine, the jet is formed by expanding |
| A. | Highly heated atmospheric air |
| B. | Solids |
| C. | Liquid |
| D. | Plasma |
| Answer» B. Solids | |
| 64. |
Volumetric efficiency is |
| A. | The ratio of stroke volume to clearance volume |
| B. | The ratio of the air actually delivered to the amount of piston displacement |
| C. | Reciprocal of compression ratio |
| D. | Index of compressor performance |
| Answer» C. Reciprocal of compression ratio | |
| 65. |
Volumetric efficiency of air compressors is of the order of |
| A. | 20 - 30% |
| B. | 40 - 50% |
| C. | 60 - 70% |
| D. | 70 - 90% |
| Answer» E. | |
| 66. |
The compression ratio in a gas turbine is of the order of |
| A. | 3.5 : 1 |
| B. | 5 : 1 |
| C. | 8 : 1 |
| D. | 12 : 1 |
| Answer» D. 12 : 1 | |
| 67. |
The ratio of the indicated power to the shaft power or brake power of the motor or engine required to drive the compressor, is called |
| A. | Compressor efficiency |
| B. | Volumetric efficiency |
| C. | Isothermal efficiency |
| D. | Mechanical efficiency |
| Answer» E. | |
| 68. |
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 | |
| 69. |
Diffuser in a compressor is used to |
| A. | Increase velocity |
| B. | Make the flow streamline |
| C. | Convert pressure energy into kinetic energy |
| D. | Convert kinetic energy into pressure energy |
| Answer» E. | |
| 70. |
Pick up wrong statement. Surging phenomenon in centrifugal compressor depends on |
| A. | Mass flow rate |
| B. | Pressure ratio |
| C. | Change in load |
| D. | Stagnation pressure at the outlet |
| Answer» E. | |
| 71. |
The air is delivered ________ in one revolution in case of a three lobbed rotor. |
| A. | Two times |
| B. | Three times |
| C. | Four times |
| D. | Six times |
| Answer» E. | |
| 72. |
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 | |
| 73. |
For a two stage reciprocating compressor, compression from p₁ to p₃ is with perfect intercooling and no pressure losses. If compression in both the cylinders follows the same polytropic process and the atmospheric pressure is pa, then the intermediate pressure p₂ is given by |
| A. | p₂ = (p₁ + p₃)/2 |
| B. | p₂ = p₁. p₃ |
| C. | P₂ = Pa × p₃/p₁ |
| D. | p₂ = Pa p₃/p₁ |
| Answer» C. P₂ = Pa × p₃/p₁ | |
| 74. |
The axial flow compressor is preferred in aircraft gas turbines because of |
| A. | Low frontal area |
| B. | Higher thrust |
| C. | High pressure rise |
| D. | None of these |
| Answer» B. Higher thrust | |
| 75. |
The blades of gas turbine are made of |
| A. | High nickel alloy |
| B. | Stainless steel |
| C. | Carbon steel |
| D. | High alloy steel |
| Answer» B. Stainless steel | |
| 76. |
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 | |
| 77. |
The capacity of a compressor is expressed in |
| A. | kg/m² |
| B. | kg/m³ |
| C. | m³/min |
| D. | m³/kg |
| Answer» D. m³/kg | |
| 78. |
A rotary compressor is driven by an |
| A. | Electric motor |
| B. | Engine |
| C. | Either (A) or (B) |
| D. | None of these |
| Answer» D. None of these | |
| 79. |
Isothermal compression efficiency, even when running at high speed, can be approached by using |
| A. | Multistage compression |
| B. | Cold water spray |
| C. | Both (A) and (B) above |
| D. | Fully insulating the cylinder |
| Answer» D. Fully insulating the cylinder | |
| 80. |
The volumetric efficiency for reciprocating air compressors is about |
| A. | 10 to 40% |
| B. | 40 to 60% |
| C. | 60 to 70% |
| D. | 70 to 90% |
| Answer» E. | |
| 81. |
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 | |
| 82. |
Axial flow compressor resembles |
| A. | Centrifugal pump |
| B. | Reciprocating pump |
| C. | Turbine |
| D. | Sliding vane compressor |
| Answer» D. Sliding vane compressor | |
| 83. |
The ratio of work done per cycle to the swept volume in case of compressor is called |
| A. | Compression index |
| B. | Compression ratio |
| C. | Compressor efficiency |
| D. | Mean effective pressure |
| Answer» E. | |
| 84. |
The absolute pressure of air at the outlet of a compressor is called |
| A. | Back pressure |
| B. | Critical pressure |
| C. | Discharge pressure |
| D. | None of these |
| Answer» D. None of these | |
| 85. |
The thrust on the rotor in a centrifugal compressor is produced by |
| A. | Radial component |
| B. | Axial component |
| C. | Tangential component |
| D. | None of the above |
| Answer» C. Tangential component | |
| 86. |
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 | |
| 87. |
Out of the following, from where you will prefer to take intake for air compressor |
| A. | From an air conditioned room maintained at 20°C |
| B. | From outside atmosphere at 1°C |
| C. | From coal yard side |
| D. | From a side where cooling tower is located nearby |
| Answer» E. | |
| 88. |
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. |
| A. | Equal to |
| B. | Less than |
| C. | Greater than |
| D. | None of these |
| Answer» B. Less than | |
| 89. |
In multistage compressor, the isothermal compression is achieved by |
| A. | Employing inter-cooler |
| B. | By constantly cooling the cylinder |
| C. | By running compressor at very slow speed |
| D. | By insulating the cylinder |
| Answer» D. By insulating the cylinder | |
| 90. |
The volume of air delivered by the compressor is called |
| A. | Free air delivery |
| B. | Compressor capacity |
| C. | Swept volume |
| D. | None of these |
| Answer» C. Swept volume | |
| 91. |
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 | |
| 92. |
In a reciprocating air compressor, the compression work per kg of air |
| A. | Increases as clearance volume increases |
| B. | Decreases as clearance volume increases |
| C. | Is independent of clearance volume |
| D. | Increases as clearance volume decreases |
| Answer» D. Increases as clearance volume decreases | |
| 93. |
Volumetric efficiency of a compressor decreases with ________ in compression ratio. |
| A. | Decrease |
| B. | Increase |
| C. | Remain same |
| D. | Does not change |
| Answer» C. Remain same | |
| 94. |
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 |
| A. | D₁/D₂ = (p₁ p₃)1/2 |
| B. | D₁/D₂ = (p₁/p₃)1/4 |
| C. | D₁/D₂ = (p₁ p₃)1/4 |
| D. | D₁/D₂ = (p₃/p₁)1/4 |
| Answer» E. | |
| 95. |
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 (W₁/W₂) with perfect intercooling is given by |
| A. | W₁/W₂ = n₂(n₁ - 1)/n₁(n₂ - 1) |
| B. | W₁/W₂ = n₁(n₂ - 1)/n₂(n₁ - 1) |
| C. | W₁/W₂ = n₁/n₂ |
| D. | W₁/W₂ = n₂/n₁ |
| Answer» C. W₁/W₂ = n₁/n₂ | |
| 96. |
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 = Dia. of L.P. cylinder, and D₂ = Dia. of H.P. cylinder) |
| A. | D₁/D₂ = p₁ p₂ |
| B. | D₁/D₂ = p₁/p₂ |
| C. | D₁/D₂ = p₂/p₁ |
| D. | None of these |
| Answer» D. None of these | |
| 97. |
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 | |
| 98. |
Which of the following statement is correct relating to rocket engines? |
| A. | The combustion chamber in a rocket engine is directly analogous to the reservoir of a supersonic wind tunnel |
| B. | The stagnation conditions exist at the combustion chamber |
| C. | The exit velocities of exhaust gases are much higher than those in jet engine |
| D. | All of the above |
| Answer» E. | |
| 99. |
In the axial flow gas turbine, the work ratio is the ratio of |
| A. | Compressor work and turbine work |
| B. | Output and input |
| C. | Actual total head temperature drop to the isentropic total head drop from total head inlet to static head outlet |
| D. | Actual compressor work and theoretical compressor work |
| Answer» D. Actual compressor work and theoretical compressor work | |
| 100. |
High air-fuel ratio in gas turbines |
| A. | Increases power output |
| B. | Improves thermal efficiency |
| C. | Reduces exhaust temperature |
| D. | Do not damage turbine blades |
| Answer» D. Do not damage turbine blades | |