MCQOPTIONS
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MCQOPTIONS
This section includes 73 Mcqs, each offering curated multiple-choice questions to sharpen your Mechanical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
For the same compression ratio, the efficiency of a dual combustion cycle is- |
| A. | Less than Diesel cycle efficiency |
| B. | Less than Diesel cycle and greater than Otto cycle efficiency |
| C. | Less than Otto cycle and greater than Diesel cycle efficiency |
| D. | Greater than Otto cycle efficiency |
| Answer» D. Greater than Otto cycle efficiency | |
| 52. |
For an air-standard Diesel cycle, |
| A. | heat addition is at constant volume and heat rejection is at constant pressure |
| B. | heat addition is at constant pressure and heat rejection is at constant pressure |
| C. | heat addition is at constant pressure and heat rejection is at constant volume |
| D. | heat addition is at constant volume and heat rejection is at constant volume |
| Answer» D. heat addition is at constant volume and heat rejection is at constant volume | |
| 53. |
For same compression ratio & heat supplied, which thermodynamic air cycle has maximum thermal efficiency? |
| A. | Otto cycle |
| B. | Diesel cycle |
| C. | Dual cycle |
| D. | All of these |
| Answer» B. Diesel cycle | |
| 54. |
For same compression ratio |
| A. | Thermal efficiency of Otto cycle is greater than that of diesel cycle |
| B. | Thermal efficiency of Otto cycle is less than that of diesel cycle |
| C. | Both (a) & (b) |
| D. | Thermal efficiency of Otto cycle is equal to that of diesel cycle |
| Answer» B. Thermal efficiency of Otto cycle is less than that of diesel cycle | |
| 55. |
Diesel engines are generally |
| A. | Quality governed |
| B. | Quantity governed |
| C. | Combination of quality and quantity governed |
| D. | Heat and mass governed |
| Answer» B. Quantity governed | |
| 56. |
If the cut-off ratio is decreased, the efficiency of diesel cycle |
| A. | Increases |
| B. | Decreases |
| C. | Remains constant |
| D. | May increase or decrease |
| Answer» B. Decreases | |
| 57. |
Otto cycle is a constant ________ cycle. |
| A. | Temperature |
| B. | Entropy |
| C. | Pressure |
| D. | Volume |
| Answer» E. | |
| 58. |
For the same values of peak pressure, peak temperature and heat rejection, the correct order of efficiencies for Otto, Dual and Diesel cycles is |
| A. | ηOtto > ηDual > ηDiesel |
| B. | ηDual > ηDiesel > ηOtto |
| C. | ηDisel > ηDual > ηOtto |
| D. | ηDisel > ηOtto > ηDual |
| E. | ηOtto > ηDiesel > ηDual |
| Answer» D. ηDisel > ηOtto > ηDual | |
| 59. |
An ideal spark ignition engine has a compression ratio of 9. What is its Air standard efficiency if ratio of specific heats is 1.5? |
| A. | 63% |
| B. | 67% |
| C. | 70% |
| D. | 72% |
| Answer» C. 70% | |
| 60. |
In an air standard Otto cycle, the compression ratio is 7. Find the cycle efficiency |
| A. | 54% |
| B. | 38% |
| C. | 71% |
| D. | 80% |
| Answer» B. 38% | |
| 61. |
In a compressor, the clearance volume is kept minimum, because it affects |
| A. | isothermal efficiency |
| B. | compressor efficiency |
| C. | volumetric efficiency |
| D. | none of the above |
| Answer» D. none of the above | |
| 62. |
Consider the following statements regarding cycles:1. Stirling cycle consists of two isothermal and two adiabatic processes.2. In vapour compression cycle, the refrigerant is in the form of dry saturated vapour before enteringcompressor.3. Diesel cycle consists of one constant pressure; one constant volume and two isentropic processes Which of the above statements are correct? |
| A. | 1,2 and 3 |
| B. | 1 and 2 only |
| C. | 1 and 3 only |
| D. | 2 and 3 only |
| Answer» E. | |
| 63. |
An ideal gas with heat capacity ratio of 2 is used in an ideal Otto-cycle which operates between minimum and maximum temperatures of 200 K and 1800 K. What is the compression ratio of the cycle for maximum work output? |
| A. | 1.5 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» D. 4 | |
| 64. |
For the same heat added and the same compression ratio, ________. |
| A. | Otto cycle is more efficient than diesel cycle. |
| B. | Diesel cycle is more efficient than Otto cycle. |
| C. | Both Diesel and Otto cycle are equally efficient. |
| D. | Cannot be determined. |
| Answer» B. Diesel cycle is more efficient than Otto cycle. | |
| 65. |
A 4-stroke diesel engine has length of 20 cm and diameter of 16 cm. The engine is producing power of 25 kW when it is running at 2500 r.p.m. The mean effective pressure of the engine will be nearly |
| A. | 5.32 bar |
| B. | 4.54 bar |
| C. | 3.76 bar |
| D. | 2.98 bar |
| Answer» E. | |
| 66. |
A turbo-charged four-stroke direct injection diesel engine has a displacement volume of 0.0259 m3 ( 25.9 litres) . The engine has an output of 950 kW at 2200 rpm. The mean effective pressure in MPa is closest to |
| A. | 2 |
| B. | 1 |
| C. | 0.2 |
| D. | 0.1 |
| Answer» B. 1 | |
| 67. |
Petrol is used in which cycle? |
| A. | Otto cycle |
| B. | Diesel cycle |
| C. | Rankine cycle |
| D. | Carnot cycle |
| Answer» B. Diesel cycle | |
| 68. |
In a four-stroke cycle, the minimum temperature inside the engine cylinder occurs at the |
| A. | beginning of suction stroke |
| B. | end of suction stroke |
| C. | beginning of exhaust stroke |
| D. | end of exhaust stroke |
| Answer» B. end of suction stroke | |
| 69. |
A diesel engine has a compression ratio of 16 and cut-off takes place at 6% of the stroke. What will be the cut-off ratio? |
| A. | 1.6 |
| B. | 1.9 |
| C. | 2.1 |
| D. | 2.4 |
| Answer» C. 2.1 | |
| 70. |
Compression ratio in case of SI engine is in the range of |
| A. | 6 - 10 |
| B. | 10 - 15 |
| C. | 16 - 25 |
| D. | 25 - 40 |
| Answer» B. 10 - 15 | |
| 71. |
For the same compression ratio, the thermodynamic cycles in the order of decreasing efficiencies are |
| A. | Dual, Diesel, Otto |
| B. | Dual, Otto, Diesel |
| C. | Diesel, Dual, Otto |
| D. | Otto, Dual, Diesel |
| Answer» E. | |
| 72. |
An ideal air-standard diesel engine has a compression ratio of 14 ∶ 1. The state of air at the beginning of the compression stroke is 400 kPa and 400 K. The highest temperature during the cycle is 1500 K. Assume air to be an ideal gas with constant specific heats. The gas constant of air is R = 0.287 kJ/kg-K and specific heat at constant volume cv = 0.717 kJ/kg-K. Air temperature at the end of the compression stroke is |
| A. | 1050 K |
| B. | 1500 K |
| C. | 1149.51 K |
| D. | 560 K |
| Answer» D. 560 K | |
| 73. |
An ideal cycle based on the concept of combination of two heat addition processes, one at constant volume and the other at constant pressure, is called |
| A. | Otto cycle |
| B. | Dual cycle |
| C. | Diesel cycle |
| D. | Carnot cycle |
| Answer» C. Diesel cycle | |