#### Steam Nozzles and Turbines

1

The efficiency of an impulse turbine is maximum when (where Vb = Blade speed, V = Absolute velocity of steam entering the blade, and alpha = Nozzle angle)

A. V_b = 0.5 V cos alpha
B. V_b = V cos alpha
C. V_b = 0.5 V^2 cos alpha
D. V_b = V^2 cos alpha

2

For a Parson's reaction turbine, if alpha_1 and alpha_2 are fixed blade angles at inlet and exit respectively and beta_1 and beta_2are the moving blade angles at entrance and exit respectively, then

A. alpha_1 = alpha_2 and beta_1 = beta_2
B. alpha_1 = beta_1 and alpha_2 = beta_2
C. alpha_1 < beta_1 and alpha_2 > beta_2
D. alpha_1 = beta_2 and beta_1 = alpha_2

3

In a Parson's turbine stage, blade velocity is 320 m/s at the mean radius and rotor blade exit angle is 30^circFor minimum kinetic energy of the steam leaving the stage, the steam velocity at the exit of the rotor will be

A. 160//sqrt(3) m//s
B. 320//sqrt(3) m//s
C. 640//sqrt(3) m//s
D. 640 m/s

4

The maximum efficiency of a De-Laval turbine is (where alpha = Nozzle angle)

A. sin ^2 alpha
B. cos ^2 alpha
C. tan^2 alpha
D. cot^2 alpha

5

The maximum efficiency of a reaction turbine is

A. (2sin^2 alpha)/(1 + sin ^2 alpha)
B. (2cos ^2 alpha)/(1 + cos ^2 alpha)
C. (1 + sin ^2 alpha)/(2sin ^2 alpha)
D. (1 + cos^2 alpha)/(2 cos ^2 alpha)`