MCQOPTIONS
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MCQOPTIONS
This section includes 15 Mcqs, each offering curated multiple-choice questions to sharpen your Thermal Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
In an impulse turbine, the axial force on the blades is zero if _____ |
| A. | the whirl components of the inlet and outlet absolute velocities are equal |
| B. | the flow components of the inlet and outlet absolute velocities are equal |
| C. | the exit velocity of steam is axial |
| D. | the flow and whirl component of inlet velocity are equal |
| Answer» C. the exit velocity of steam is axial | |
| 2. |
Work done per kg of steam in an impulse turbine when the blade speed ratio ( ) is equal to one is _____ |
| A. | 0 |
| B. | C<sub>bl</sub><sup>2</sup> |
| C. | 2C<sub>bl</sub><sup>2</sup> |
| D. | 2C<sub>bl</sub>(C<sub>f1</sub>+C<sub>f2</sub>) |
| Answer» B. C<sub>bl</sub><sup>2</sup> | |
| 3. |
Which of the following statement about the work done per kg of steam in impulse turbines is TRUE, when the blade speed ratio is equals ( frac{cos }{2} )? ( is the nozzle angle) |
| A. | Work done per kg of steam is maximum and is equal to 2C<sub>1</sub><sup>2</sup> |
| B. | Work done per kg of steam is minimum and is equal to 2C<sub>1</sub><sup>2</sup> |
| C. | Work done per kg of steam is maximum and is equal to 2C<sub>bl</sub><sup>2</sup> |
| D. | Work done per kg of steam is minimum and is equal to 2C<sub>bl</sub><sup>2</sup> |
| Answer» D. Work done per kg of steam is minimum and is equal to 2C<sub>bl</sub><sup>2</sup> | |
| 4. |
Which of the following statement about efficiency of impulse turbines is TRUE, when the blade speed ratio is made equal to half of cosine of the nozzle angle? |
| A. | Efficiency is minimum and is equal to ( frac{cos u2061 ^2}{2} ) |
| B. | Efficiency is maximum and is equal to ( frac{cos u2061 ^2}{2} ) |
| C. | Efficiency is minimum and is equal to cos u2061 <sup>2</sup> |
| D. | Efficiency is maximum and is equal to cos u2061 <sup>2</sup> |
| Answer» E. | |
| 5. |
Which of the following statement regarding work done in impulse turbines is TRUE, if the blade speed ratio is equal to zero? |
| A. | Maximum possible work done takes place |
| B. | Work done becomes zero |
| C. | Nothing can be stated about work done |
| D. | work done per kg of steam is equal to |
| Answer» C. Nothing can be stated about work done | |
| 6. |
In a single stage impulse turbine, the exit velocity of the steam is 90 m/s at an angle of 45 from the tangential direction. The mean blade speed is 200 m/s. The blades are equiangular and velocity coefficient of the blades is 0.8. Determine the velocity of steam leaving the nozzles. |
| A. | 472.32 m/s |
| B. | 535.50 m/s |
| C. | 624.84 m/s |
| D. | 784.36 m/s |
| Answer» C. 624.84 m/s | |
| 7. |
In a single stage impulse turbine nozzle angle is 20 and the mean blade speed is 300 m/s. Steam leaves the nozzle at a velocity of 700 m/s. Determine the exit velocity of the steam if the turbine blades are equiangular and frictionless. |
| A. | 154.65 m/s |
| B. | 195.65 m/s |
| C. | 246.30 m/s |
| D. | 321.32 m/s |
| Answer» D. 321.32 m/s | |
| 8. |
A simple impulse turbine has one ring of moving blades running at 400 m/s. The steam velocity leaving the nozzle is 1300 m/s. If the nozzle angle is 25 , determine the blade inlet angle. |
| A. | 15 |
| B. | 20 |
| C. | 25 |
| D. | 35 |
| Answer» E. | |
| 9. |
In a simple impulse turbine, steam leaves nozzle at 1200 m/s. The mean blade speed and nozzle angle is 300 m/s and 20 respectively. The inlet and outlet blade angles are equal. The blades of the turbine are frictionless. Determine the stage efficiency if the nozzle efficiency is 85%. |
| A. | 58.65% |
| B. | 62.32% |
| C. | 75.45% |
| D. | 84.37% |
| Answer» B. 62.32% | |
| 10. |
In a single row impulse turbine, steam leaves the nozzle at 600 m/s. The nozzle angle and the mean blade speed is 25 and 200 m/s. The blade velocity coefficient is 0.8. Determine the blade outlet angle if the steam leaves the turbine blades axially. |
| A. | 54 |
| B. | 60 |
| C. | 66 |
| D. | 74 |
| Answer» B. 60 | |
| 11. |
In a single row impulse turbine, the absolute velocity of steam leaving the turbine is 900 m/s. The nozzle angel is 20 . The mean blade speed is 300 m/s. The inlet blade angle is equal to the outlet blade angle. Determine the angle made by the discharging steam with the tangent of the wheel at the exit of moving blade. Neglect friction on turbine blades. |
| A. | 27 |
| B. | 36 |
| C. | 51 |
| D. | 90 |
| Answer» D. 90 | |
| 12. |
In a De-Laval turbine, steam with absolute velocity of 950 m/s is supplied through a nozzle. The mean blade velocity is 300 m/s. If the turbine is working at its maximum possible efficiency, determine the work done per kg of steam. |
| A. | 180 kJ |
| B. | 200 kJ |
| C. | 1705 kJ |
| D. | 1805 kJ |
| Answer» B. 200 kJ | |
| 13. |
In a De laval turbine, steam leaves nozzle with a velocity of 1300 m/s. The nozzle angle is 25 and the mean blade speed is 500 m/s. The inlet and outlet blade angles are equal. Find out work done per kg of steam if the blades of the turbine are frictionless. |
| A. | 678.205 kJ |
| B. | 798.562 kJ |
| C. | 365.458 kJ |
| D. | 456.321 kJ |
| Answer» B. 798.562 kJ | |
| 14. |
The maximum possible efficiency of a De-laval turbine is 88.3%. Determine the nozzle angle. |
| A. | 15 |
| B. | 20 |
| C. | 25 |
| D. | 30 |
| Answer» C. 25 | |
| 15. |
In a simple impulse turbine, it is observed that 22.4 kJ energy is lost to blade friction. The uses steam at a rate of 1 kg/s. If the velocity of steam relative to the moving blade at an entrance is 300 m/s, determine the blade velocity coefficient. |
| A. | 0.325 |
| B. | 0.456 |
| C. | 0.867 |
| D. | 0.951 |
| Answer» D. 0.951 | |