Q: Definition check: What qualifies as a convergent nozzle in fluid/steam-nozzle terminology? Identify the correct description of how the cross-sectional area changes from inlet to exit. Choose the correct option.

Given Question asks for the definition of a convergent nozzle. Concept A convergent nozzle has a monotonically decreasing flow area from the inlet to the exit; a convergent–divergent (C–D) nozzle has a minimum area (throat) followed by a diverging exit section. Final Answer Area decreases continuously from entrance to exit.

Q: True/False (steam nozzles): Compare critical pressure ratios for different steam qualities. Statement: “The critical pressure ratio for initially dry saturated steam is greater than that for initially wet steam.” Decide whether the statement is cor…

Concept Critical pressure ratio (p₂/p₁) for choking depends on the effective expansion index and thermodynamic properties of the working fluid. With higher dryness fraction (approaching dry saturated), the effective index yields a slightly higher critical pressure ratio than for wetter steam. Implication Thus, for the same inlet state, initially dry saturated steam requires a relatively higher p₂/p₁ to choke than initially wet steam. Final Answer Agree.

Question 1

Supersaturated steam flow through a nozzle vs. stable (equilibrium) flow  When steam expands with supersaturation (delayed condensation), how does the available heat drop compare to a stable (equilibrium) expansion? Choose the correct option.

Accepted Answer

Concept Supersaturation delays condensation, so steam expands further in a metastable state before nuclei form. This permits a larger effective pressure/enthalpy drop across the nozzle prior to condensation (commonly evidenced by slightly higher exit velocity and mass flow than the equilibrium prediction). Implication Because of delayed phase change, the available heat drop (and thus attainable jet kinetic energy) tends to be higher than under fully stable equilibrium expansion at the same inlet and back pressures. Final Answer Increases

Question 2

Applications of steam turbines  Identify where steam turbines are commonly used in practice. Choose the correct option.

Accepted Answer

Concept Steam turbines are versatile prime movers used in marine propulsion (especially large ships), power plants (utility and industrial), and for mechanical drives (fans, compressors, pumps) where high-speed, continuous-duty operation is needed. Final Answer All of these

Question 3

Type classification: De Laval turbine  Classify the De Laval turbine according to type and staging. Choose the correct option.

Accepted Answer

Concept The classic De Laval machine is a single-stage, single-rotor impulse turbine with a convergent–divergent nozzle and one ring of moving blades. All pressure drop occurs in the nozzle; the rotor extracts kinetic energy only. Final Answer Single-rotor impulse turbine

Question 4

Exit state from a nozzle  Steam leaves a nozzle with what typical combination of pressure and velocity? Choose the correct option.

Accepted Answer

Concept A nozzle converts pressure energy into kinetic energy: pressure drops while velocity rises. Therefore, the exit condition is low pressure, high velocity. Final Answer Low pressure and high velocity

Question 5

Parsons turbine: impulse or reaction?  Identify the correct classification of a Parsons turbine stage. Choose the correct option.

Accepted Answer

Concept The Parsons turbine uses roughly 50% reaction per stage; pressure drop is shared between fixed and moving blades. Hence it is an impulse–reaction type. Final Answer Impulse–reaction turbine

Question 6

Choked flow in a convergent–divergent steam nozzle  Statement: In a C–D nozzle, the mass discharge rate depends on the initial (inlet) steam conditions and the throat area (once choked), not on the exit pressure. Decide whether the statement is corr…

Accepted Answer

Concept After the back pressure is reduced to the critical (choked) value, the throat Mach number is 1. The mass flow then becomes a function of inlet state and throat area only; further reduction of exit pressure does not increase discharge. Final Answer True

Question 7

Effect of reducing back (exit) pressure on nozzle mass flow  As the exit/back pressure is gradually reduced from high to low values, how does the mass discharge rate through a steam nozzle change? Choose the correct option.

Accepted Answer

Concept Before choking, lowering the back pressure increases the pressure drop and hence the mass flow. At the critical back pressure, the flow chokes (Mach 1 at the throat). Beyond this point, further back-pressure reduction cannot raise the mass flow; it stays constant. Graphical view Discharge vs. back pressure: rising curve up to the critical point, then a horizontal plateau. Final Answer Increases up to a critical back pressure and then remains constant

Question 8

Steam nozzle back pressure vs design exit pressure: identify the nozzle condition for expansion.  Given: Back pressure (ambient) is lower than the designed exit pressure of the nozzle. Choose the correct technical term that describes the nozzle cond…

Accepted Answer

Concept/Approach For a fixed-geometry convergent–divergent nozzle, the designed exit pressure is the ambient pressure at which the nozzle ideally expands the fluid to match the surroundings.If the actual back (ambient) pressure is lower than this designed value, the nozzle has not expanded enough — the exit pressure remains higher than ambient — and therefore the jet needs further expansion outside the nozzle. Definition Underexpanded nozzle: exit static pressure > ambient (back) pressure; needs additional expansion externally (expansion fans form at the lip).Overexpanded nozzle: exit static pressure < ambient pressure; external compression shocks form. Final Answer Underexpanded nozzle.

Question 9

Definition check: What qualifies as a convergent nozzle in fluid/steam-nozzle terminology?  Identify the correct description of how the cross-sectional area changes from inlet to exit. Choose the correct option.

Accepted Answer

Given Question asks for the definition of a convergent nozzle. Concept A convergent nozzle has a monotonically decreasing flow area from the inlet to the exit; a convergent–divergent (C–D) nozzle has a minimum area (throat) followed by a diverging exit section. Final Answer Area decreases continuously from entrance to exit.

Question 10

True/False (steam nozzles): Compare critical pressure ratios for different steam qualities.  Statement: “The critical pressure ratio for initially dry saturated steam is greater than that for initially wet steam.” Decide whether the statement is cor…

Accepted Answer

Concept Critical pressure ratio (p₂/p₁) for choking depends on the effective expansion index and thermodynamic properties of the working fluid. With higher dryness fraction (approaching dry saturated), the effective index yields a slightly higher critical pressure ratio than for wetter steam. Implication Thus, for the same inlet state, initially dry saturated steam requires a relatively higher p₂/p₁ to choke than initially wet steam. Final Answer Agree.

Question 11

In a reaction turbine

Accepted Answer

the expansion of steam takes place partly in the fixed blades and partly in the moving blades

Question 12

The critical pressure ratio for gases is

Accepted Answer

0.528

Question 13

The velocity of steam at throat of the nozzle is __________ the velocity of sound.

Accepted Answer

equal to

Question 14

The reheat factor depends upon

Accepted Answer

all of these

Question 15

The ratio of the workdone on the blades per kg of steam to the total energy supplied per stage per kg of steam is called

Accepted Answer

stage efficiency

Question 16

The discharge through a nozzle is maximum for a certain value of exit pressure. This pressure is known as critical pressure.

Accepted Answer

Agree

Question 17

A single stage impulse turbine with a diameter of 1.2 m runs at 3000 r.p.m. If the blade speed ratio is 0.42, then the inlet velocity of steam will be

Accepted Answer

450 m/s

Question 18

In an impulse turbine

Accepted Answer

the steam is expanded in nozzles only and there is a pressure drop and heat drop

Question 19

The compounding of turbines is done in order to

Accepted Answer

all of these

Question 20

The efficiency ratio is the ratio of total useful heat drop to the total isentropic heat drop.

Accepted Answer

Agree

Steam Nozzles and Turbines Questions