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 ratio of the workdone on the blades to the energy supplied to the blades, is called
A. blading efficiency
B. nozzle efficiency
C. gross or stage efficiency
D. mechanical efficiency
Question 2
Parson's turbine is a
A. simple impulse turbine
B. simple reaction turbine
C. impulse-reaction turbine
D. none of these
Question 3
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 4
Parson's reaction turbine is a __________ reaction turbine.
A. 40 percent
B. 50 percent
C. 60 percent
D. 70 percent
Question 5
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 6
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 7
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 8
The critical pressure ratio for initially dry saturated steam is more as compared to initially wet steam.
A. Yes
B. No
Question 9
The critical pressure gives the velocity of steam at the throat equal to the velocity of sound.
A. Agree
B. Disagree
Question 10
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 11
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 12
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 13
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 14
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 15
The action of steam in a steam turbine is
A. static
B. dynamic
C. static and dynamic
D. neither static nor dynamic
Question 16
The critical pressure ratio for initially wet steam is
A. 0.546
B. 0.577
C. 0.582
D. 0.601
Question 17
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 18
Multi-stage steam turbines are of the
A. velocity compounded type
B. reaction type
C. pressure compounded type
D. all of these
Question 19
De-Laval turbine is a
A. single rotor impulse turbine
B. multi-rotor impulse turbine
C. impulse reaction turbine
D. none of these
Question 20
The flow through a nozzle is regarded as
A. constant volume flow
B. constant pressure flow
C. isothermal flow
D. isentropic flow
Question 21
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 22
The rate of discharge through the nozzle __________ when the exit pressure is gradually reduced.
A. remains same
B. decreases
C. increases
Question 23
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 24
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 25
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 26
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 27
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 28
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 29
Thermal equilibrium means that the flow of steam is
A. isothermal
B. isentropic
C. hyperbolic
D. polytropic
Question 30
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 31
The turbine blades are
A. straight
B. circular
C. curved
Question 32
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
Question 33
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 34
The pressure at which the steam leaves the nozzle is known as back pressure.
A. Correct
B. Incorrect
Question 35
The turbine blades do not change the direction of steam issuing from the nozzle.
A. TRUE
B. FALSE
Question 36
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 37
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 38
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 39
The discharge is __________ at critical pressure.
A. zero
B. minimum
C. maximum
Question 40
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 41
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 42
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 43
A binary vapour plant consists of
A. steam turbine
B. steam condenser
C. mercury boiler
D. all of these
Question 44
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 45
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 46
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 47
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 48
The steam enters 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