Steam Nozzles and Turbines MCQ Questions & Answers

Steam Nozzles and Turbines MCQs : This section focuses on the "Steam Nozzles and Turbines". These Multiple Choice Questions (MCQs) should be practiced to improve the Steam Nozzles and Turbines skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.

Question 1

The blade velocity coefficient is ratio of relative velocity of steam at outlet tip of the blade to the relative velocity of steam at inlet tip of the blade.

A. TRUE
B. FALSE

Question 2

The Parsons' reaction turbine has

A. only moving blades
B. only fixed blades
C. identical fixed and moving blades
D. fixed and moving blades of different shape

Question 3

The difference of supersaturated temperature and saturation temperature at that pressure is called

A. degree of supersaturation
B. degree of superheat
C. degree of undercooling
D. none of these

Question 4

A nozzle is said to be a convergent nozzle

A. when the cross-section of the nozzle increases continuously from entrance to exit
B. when the cross-section of the nozzle decreases continuously from entrance to exit
C. when the cross-section of the nozzle first decreases from entrance to throat and then increases from its throat to exit
D. none of the above

Question 5

Which of the following statement is correct?

A. The expansion of steam in a nozzle follows Rankine cycle.
B. The friction in the nozzle increases the dryness fraction of steam.
C. The pressure of steam at throat is called critical pressure.
D. all of the above

Question 6

The velocity of steam leaving the nozzle (V) is given by (where K = Nozzle coefficient or nozzle efficiency, and hd = Enthalpy or heat drop during expansion of steam in a nozzle)

A. V = 44.72 hd K
B. V = 44.72 K hd
C. V = 44.72 K hd
D. V = 44.72 K hd

Question 7

The turbine blades do not change the direction of steam issuing from the nozzle.

A. TRUE
B. FALSE

Question 8

Multi-stage steam turbines are of the

A. velocity compounded type
B. reaction type
C. pressure compounded type
D. all of these

Question 9

The pressure at which the steam leaves the nozzle is known as back pressure.

A. Correct
B. Incorrect

Question 10

The critical pressure ratio for initially dry saturated steam is more as compared to initially wet steam.

A. Yes
B. No

Question 11

The ratio of the useful heat drop to the isentropic heat drop is called

A. condenser efficiency
B. nozzle efficiency
C. boiler efficiency
D. vacuum efficiency

Question 12

The action of steam in a steam turbine is

A. static
B. dynamic
C. static and dynamic
D. neither static nor dynamic

Question 13

The critical pressure ratio for initially wet steam is

A. 0.546
B. 0.577
C. 0.582
D. 0.601

Question 14

The discharge is __________ at critical pressure.

A. zero
B. minimum
C. maximum

Question 15

The efficiency of reaction turbine is maximum when (where α = Angle made by the absolute velocity (V) at inlet)

A. Vb = 0.5 V cos α
B. Vb = V cos α
C. Vb = 0.5 V2 cos α
D. Vb = V2 cos α

Question 16

In a convergent divergent nozzle, the discharge depends upon the initial conditions of steam and the area of nozzle at throat.

A. Correct
B. Incorrect

Question 17

The turbine blades are

A. straight
B. circular
C. curved

Question 18

The efficiency of steam turbines may be improved by

A. reheating of steam
B. regenerative feed heating
C. binary vapour plant
D. any one of these

Question 19

The steam leaves the nozzle at a

A. high pressure and a low velocity
B. high pressure and a high velocity
C. low pressure and a low velocity
D. low pressure and a high velocity

Question 20

De-Laval turbine is a

A. single rotor impulse turbine
B. multi-rotor impulse turbine
C. impulse reaction turbine
D. none of these

Question 21

In reaction turbines, the axial thrust is due to

A. pressure drop across the rotor
B. change in axial velocity
C. both (a) and (b)
D. none of these

Question 22

In a nozzle, whole frictional loss is assumed to occur between

A. inlet and thoroat
B. inlet and outlet
C. throat and exit
D. all of these

Question 23

The critical pressure gives the velocity of steam at the throat

A. equal to the velocity of sound
B. less than the velocity of sound
C. more than the velocity of sound
D. none of these

Question 24

Thermal equilibrium means that the flow of steam is

A. isothermal
B. isentropic
C. hyperbolic
D. polytropic

Question 25

The variation of steam pressure in the nozzle depends upon

A. velocity of steam
B. specific volume of steam
C. dryness fraction of steam
D. all of these

Question 26

Steam turbines are used for

A. large marine propulsion
B. electric power generation
C. direct drive of fans, compressors, pumps
D. all of these

Question 27

The discharge of steam in a convergent-divergent nozzle __________ after the throat (i.e. in the divergent portion of the nozzle)

A. remains constant
B. decreases
C. increases

Question 28

A binary vapour plant consists of

A. steam turbine
B. steam condenser
C. mercury boiler
D. all of these

Question 29

A regenerative steam cycle renders

A. increased work output per unit mass of steam
B. decreased work output per unit mass of steam
C. increased thermal efficiency
D. decreased work output per unit mass of steam as well as increased thermal efficiency

Question 30

The turbine, in which the general direction of the steam flow is parallel to the turbine axis, is called axial flow turbines

A. TRUE
B. FALSE

Question 31

Parson's reaction turbine is a __________ reaction turbine.

A. 40 percent
B. 50 percent
C. 60 percent
D. 70 percent

Question 32

The value of the reheat factor varies from

A. 1.02 to 1.06
B. 1.08 to 1.l0
C. 1.2 to 1.6
D. 1.6 to 2

Question 33

Parson's turbine is a

A. simple impulse turbine
B. simple reaction turbine
C. impulse-reaction turbine
D. none of these

Question 34

When the back pressure of a nozzle is below the designed value of pressure at exit of nozzle, the nozzle is said to be

A. choked
B. underdamping
C. overdamping
D. none of these

Question 35

The ratio of total useful heat drop to the total isentropic heat drop, is called

A. stage efficiency
B. internal efficiency
C. Rankine efficiency
D. none of these

Question 36

The isentropic enthalpy drop in moving blade is two-third of the isentropic enthalpy drop in fixed blades of a turbine. The degree of reaction will be

A. 0.4
B. 0.56
C. 0.67
D. 1.67

Question 37

In a De-Laval nozzle expanding superheated steam from 10 bar to 0.1 bar, the pressure at the minimum cross-section (i. e. pressure at throat, p2) will be

A. 3.3 bar
B. 5.46 bar
C. 8.2 bar
D. 9.9 bar

Question 38

The rate of discharge through the nozzle __________ when the exit pressure is gradually reduced.

A. remains same
B. decreases
C. increases

Question 39

The reheat factor is the ratio of the

A. cumulative heat drop to the isentropic heat drop
B. isentropic heat drop to the heat supplied
C. total useful heat drop to the total isentropic heat drop
D. none of the above

Question 40

The flow through a nozzle is regarded as

A. constant volume flow
B. constant pressure flow
C. isothermal flow
D. isentropic flow

Question 41

The impulse reaction turbine has its driving force

A. as an impulsive force
B. as a reaction force
C. partly as an impulsive force and partly as a reaction force
D. none of the above

Question 42

A turbine is said to have an axial discharge when the steam leaves the blade tip at __________ to the direction of the blade motion.

A. 60°
B. 90°
C. 180°
D. 270°

Question 43

The stage efficiency (ηS) is given by (where ηB = Blading efficiency, and ηN = Nozzle efficiency)

A. ηS = ηB x ηN
B. ηS = ηB/ηN
C. ηS = ηN/ηB
D. none of these

Question 44

The ratio of the workdone on the blades to the energy supplied to the blades, is called

B. nozzle efficiency
C. gross or stage efficiency
D. mechanical efficiency

Question 45

The critical pressure gives the velocity of steam at the throat equal to the velocity of sound.

A. Agree
B. Disagree

Question 46

The supersaturated flow of steam through a nozzle as compared to a stable flow, the available heat drop

A. remains the same
B. increases
C. decreases
D. is unpredictable

Question 47

In a reaction turbine, when steam flows through the fixed blades,

A. pressure increases while velocity decreases
B. pressure decreases while velocity increases
C. pressure and velocity both decreases
D. pressure and velocity both increases