Deck 11: Understanding Steam Turbines: Ratios, Actions, and Factors

Question 1

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

A)rankine efficiency
B)stage efficiency
C)internal efficiency
D)none of the mentioned

Answer 1

internal efficiency

Question 2

What is the action of steam in a steam turbine?

A)neither static nor dynamic
B)dynamic
C)static
D)both dynamic & static

Answer 2

dynamic

Question 3

The critical pressure gives the velocity of steam at the throat ___________

A)equal to the velocity of sound
B)more than velocity of sound
C)less than the velocity of light
D)none of the mentioned

Answer 3

equal to the velocity of sound

Question 4

The flow through a nozzle is regarded as ___________

A)isothermal flow
B)isobaric flow
C)isochoric flow
D)isentropic flow

Question 5

The steam leaves the nozzle at a ____________

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

Question 6

De-Laval turbine is a ____________

A)multi rotor impulse turbine
B)impulse reaction turbine
C)single rotor impulse turbine
D)none of the mentioned

Question 7

The Parsons' reaction turbine has ____________

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

Question 8

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

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

Question 9

Rateau turbine is ____________

A)pressure-velocity compounded turbine
B)simple reaction turbine
C)velocity compounded turbine
D)pressure compounded turbine

Question 10

The value of the reheat factor varies from ____________

A)1.08 to 1.10
B)1.2 to 1.6
C)1.6 to 2
D)1.02 to 1.06

Question 11

In reaction turbines, the axial thrust is due to ____________

A)pressure drop across the rotor
B)change in axial velocity
C)both pressure drop across the rotor and change in axial velocity
D)none of the mentioned

Question 12

The flow of steam is super-sonic ____________

A)in the convergent portion of the nozzle
B)at the entrance to the nozzle
C)at the throat of the nozzle
D)in the divergent portion of the nozzle

Question 13

The variation of steam pressure in the nozzle depends upon ____________

A)dryness fraction of steam
B)specific volume of steam
C)velocity of steam
D)all of the mentioned

Question 14

A binary vapour plant consists of ____________

A)mercury boiler
B)steam turbine
C)steam condenser
D)all of the mentioned

Question 15

The steam enters the nozzle at a ____________

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

Question 16

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

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

Question 17

Steam turbines are used for ____________

A)electric power generation
B)large marine propulsion
C)direct drive of fans, compressors, pumps
D)all of the mentioned

Question 18

Curtis turbine is a ____________

A)pressure compounded turbine
B)velocity compounded turbine
C)simple reaction turbine
D)pressure-velocity compounded turbine

Question 19

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 mentioned

Question 20

What is the purpose of governing in steam turbines?

A)reheat the steam and improve its quality
B)maintain the speed of the turbine
C)reduce the effective heat drop
D)completely balance against end thrust

Question 21

The ratio of the isentropic heat drop to the heat supplied is called ____________

A)stage efficiency
B)reheat factor
C)internal efficiency
D)rankine efficiency

Question 22

The reheat factor depends upon ____________

A)exit pressure
B)turbine stage efficiency
C)initial pressure and superheat
D)all of the mentioned

Question 23

What is the critical pressure ratio for initially dry saturated steam?

A)0.546
B)0.577
C)0.586
D)0.578

Question 24

In an impulse turbine, steam expands ____________

A)wholly in nozzle
B)partly in the nozzle and partly in blades
C)wholly in blades
D)none of the mentioned

Question 25

A steam nozzle converts ____________

A)heat energy of steam into potential energy
B)potential energy into heat energy of steam
C)heat energy of steam into kinetic energy
D)kinetic energy into heat energy of steam