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Home » Engineering » Mechanical Engineering » Aptitude Test - 13
1.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. stage efficiency
2.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
D. remains constant
3.The rate of discharge through the nozzle _____ when the exit pressure is gradually reduced.
A. remains same
B. decreases
C. increases
D. remains same
4.In a nozzle, whole frictional loss is assumed to occur between
A. inlet and thoroat
B. inlet and outlet
C. throat and exit
D. inlet and thoroat
5.The critical pressure ratio for initially wet steam is
A. 0.546
B. 0.577
C. 0.582
D. 0.546
6.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. 0.4
7.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. as an impulsive force
8.The efficiency of reaction turbine is maximum when (where ? = Angle made by the absolute velocity (V) at inlet)
A. Vb = 0.5 V cos ?
B. Vb = V cos ?
C. Vb = 0.5 V2 cos ?
D. Vb = 0.5 V cos ?
9.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. increased work output per unit mass of steam
10.De-Laval turbine is a
A. single rotor impulse turbine
B. multi-rotor impulse turbine
C. impulse reaction turbine
D. single rotor impulse turbine
11.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. cumulative heat drop to the isentropic heat drop
12.Thermal equilibrium means that the flow of steam is
A. isothermal
B. isentropic
C. hyperbolic
D. isothermal
13.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. choked
14.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. blading efficiency
15.The discharge is __________ at critical pressure.
A. zero
B. minimum
C. maximum
D. zero
16.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. remains the same
17.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. high pressure and a low velocity
18.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. equal to the velocity of sound
19.The action of steam in a steam turbine is
A. static
B. dynamic
C. static and dynamic
D. static
20.Multi-stage steam turbines are of the
A. velocity compounded type
B. reaction type
C. pressure compounded type
D. velocity compounded type
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. pressure drop across the rotor
22.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. The expansion of steam in a nozzle follows Rankine cycle.
23.A binary vapour plant consists of
A. steam turbine
B. steam condenser
C. mercury boiler
D. steam turbine
24.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. 3.3 bar
25.The stage efficiency (?S) is given by (where ?B = Blading efficiency, and ?N = Nozzle efficiency)
A. ?S = ?B x ?N
B. ?S = ?B/?N
C. ?S = ?N/?B
D. ?S = ?B x ?N
26.The turbine blades are
A. straight
B. circular
C. curved
D. straight
27.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. velocity of steam
28.Steam turbines are used for
A. large marine propulsion
B. electric power generation
C. direct drive of fans, compressors, pumps
D. large marine propulsion
29.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. 1.02 to 1.06
30.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. high pressure and a low velocity
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