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_2`are 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^circ``For 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)`