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Some more questions on steam turbines have been discussed here in continuation with previous discussion.

Deepali Namdeo
I have done my bachelor's in mechanical engineering from M.I.T.S Gwalior. Currently I am Design Engineer at Cameron, a Schlumberger Company.

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  2. About ME GATE Qualified. I also have an experience of 11 months teaching Engineering subjects like Industrial, Thermodynamics, SOM, HMT. Currently working as a Design Engineer at "Cameron-A Schlumberger Company" with honors from M.I.T.S Gwalior. I am pursuing my Post graduate Diploma in Design Engineering for Oil and Gas Industry

  3. 16. A single-stage impulse turbine with a diameter of 120 cm runs at 3000 rpm. If the blade speed ratio is 0.42 then, the inlet velocity of steam will be (a) 79 m/s (b) 188m/s (c) 450 m/s (d) 900 m/s IIES-1993] bladespeed velocity of steam at entry Ans. (c) Blade speed ratio- nDN b 60 1:2x3000 60 Tx1.2x50- 450m/s m/s . Inlet velocity steam- 0.42

  4. 17. The compounding of steam turbines is done to (a) Improve efficiency (e) Increase blade spocd ratio ITES-1992; 19991 (b) reduce turbinc speed (d) reducc axial thrust 17. Ans. (b) The compounding of steam turbine is done to reduce turbine speed. Running speeds of steam turbine can be brought down to practical limits by which of the following method(s)? 1. By using heavy flywheel 3. By compounding (a) 3 alone 18. IES-1996) 2. By using a quick response governor 4. By reducing fuel feed to the furnace. (c)1, 2 and 4 (b)1, 2, 3 and 4 (d) 2 and 3 18. Ans. (d)

  5. Which one of the following is the feature of pressure compounding (Rateau staging)? (a) Low efficiency at low rotational speeds (b) High efficiency with low fluid velocities (c) High efficiency with high fluid velocities (d) Low efficiency at high rotational speeds 19. IES-2004] 19. Ans. (b)

  6. [IES-1994] Which of the following statements are correct? 1. Impulse turbine rotor blades are thick at the centre 2. Rateau turbine is more efficient than Curtis turbine 3. Blade velocity coefficient for an impulse turbine is of the order of 60%. (a) 1, 2 and 3 (b) 1 and 2 20. (c) 1 and 3 (d) 2 and 3. 20. Ans. (b) 3 is wrong because blade velocity coefficient for an impulse turbine is of the V cos a 2 order less than 50%. u

  7. 21. In a simple impulse turbine the nozzle angle at the entrance is 30 . For maximum diagram efficiency what is the blade-speed ratio? IES-2009] (a) 0 259 (b) 0 75 (c) 0 5 (d) 0.433 Ans. (d) For maximum efficiency of Impulse turbine. C05 Q Blade speed ratio - 2 cos 30 0.866 -0.433 2 2

  8. 22. Assertion (A): Modern turbines have velocity compounding at the initial stages IES-2000] and pressure compounding in subsequent stages. Reason (R): Excessive tip leakage occurs in the high pressure region of reaction blading. (a) Both A and R are individually true and R is the correct explanation of A (b) Both A and R are individually true but R is not the correct explanation of A (c) A is true but R is false (d) A is false but R is true 22. Ans. (a)

  9. The net result of pressure-velocity compounding of steam turbine is: (a) Less number of stages (b) Large turbine for a given pressure drop (c) Shorter turbine for a given pressure drop (d) Lower friction loss 23. [IES-1997] 23. Ans. (a) Pressure-velocity compounding of steam turbines results is less number of stages A 4-row velocity compounded steam turbine develops total 6400 kW. What is the power developed by the last row? (a) 200 kWW 24. [IES-2005] (b) 400 kW (c) 800 kW (d) 1600 kW 24. Ans. (b) work done in different stages in velocity compounding is 6400 0kW 753+1

  10. 25. In Parson's reaction turbines, the velocity diagram triangles at the inlet IES-2004] and outlet are which of the following? (a) Asymmetrical (b) Isosceles (c) Right-angled (d) Congruent 25. Ans. (d) 26. Match List-I (Different turbine stages) with List-II (Turbines) and select IES-1999] the correct answer using the codes given below the lists: List-I A. 50% reaction stage B. Two-stage velocity compounded turbine C. Single-stage impulse D. Two-stage pressure compounded turbine List-II 1. Rateau 2. Parson 3. Curtis 4. De-Laval 5. Hero Code: A (a) 5 23 b) 5 32 (c) 2 34 (d) 3 142 -26. Ans. (c) 50% reaction turbine is Parson, 2-stage velocity compounded turbine is Curtis, single stage impulse turbine is De-Laval, and 2-stage pressure compounded turbine is Rateau.

  11. 28. The correct sequence of the given steam turbines in the ascending order of [IES-1995] efficiency at their design points is (a) Rateau, De Laval, Parson's, Curtis (b) Curtis, De Laval, Rateau, Parson's. (c) De Laval, Curtis, Rateau, Parson's (d) Parson's, Curtis, Rateau, De Laval. 28. Ans.(c) Ascending order for efficiency is De Laval, Curtis, Rateau, Parson's.

  12. Among other things, the poor part-load performance of De laval turbines is due to the (a) Formation of shock waves in the nozzle (b) Formation of expansion waves at the nozzle exit (c) Turbulent mixing at the nozzle exit (d) Increased profile losses in the rotor. -30. IES-1995 30. Ans.(b) In De Laval turbine, at part load, pressure is reduced but velocity increases which is not fully dropped in single stage. Thus expansion waves occur at nozzle exit