Objective Type Questions on Boiler and Auxiliaries

(Answers are marked in red color)

(1)     The critical pressure ratio of a convergent nozzle is defined as

a)      The ratio of outlet pressure to inlet pressure of nozzle

b)     The ratio of inlet pressure to outlet pressure of nozzle

c)      The ratio of outlet pressure to inlet pressure only when mass flow rate per unit area is minimum

d)     The ratio of outlet pressure to inlet pressure only when mass flow rate per unit area is maximum

(2)     The isentropic expansion of steam through nozzle for the steam initially dry saturated at inlet is approximated by equation

a)      PV= C

b)     P  =C

c)      P =C

d)     P =C

(3)      Curtis turbine is

a)      Reaction steam turbine

b)     Pressure-velocity compounded steam turbine

c)      Pressure compounded impulse steam turbine

d)     Velocity compounded impulse steam turbine

(4)     Parson’s turbine is

a)      Pressure compounded steam turbine

b)     Single wheel impulse steam turbine

c)      Single wheel reaction steam turbine

d)     Multi-wheel reaction steam turbine

(5)     The pressure on the two sides of the impulse wheel of steam turbine

a)      Is same

b)     Is different

c)      Increases from one side to the other side

d)     Decreases from one side to the other side

(6)     In De Laval steam turbine

a)      The pressure in the turbine rotor is approximately same as in condenser

b)     The pressure in the turbine rotor is higher than pressure in condenser

c)      The pressure in the turbine rotor gradually decreases from inlet to exit to condenser

d)     None of the above

(7)     In case of reaction steam turbine

a)      There is enthalpy drop both in fixed and moving blades

b)     There is enthalpy drop only in fixed blades

c)      There is enthalpy drop only in moving blades

d)     None of the above

(8)     The effect of considering friction losses in steam nozzle for the same pressure ratio leads to

a)      Increase in exit velocity from the nozzle

b)     Decrease in exit velocity from the nozzle

c)      No change in exit velocity from the nozzle

d)     May decrease or increase of dryness fraction of exit steam depending upon inlet quality

(9)     The ratio of exit pressure to inlet pressure for maximum mass flow rate per unit area of steam through a nozzle when steam is initially dry saturated is

a)      0.6

b)     0.578

c)      0.555

d)     0.5457

(10) The value of reheat  factor normally varies from

a)      0.5 to 0.6

b)     0.9 to 0.95

c)      1.02 to 1.06

d)     1.2 to 1.6

(11) Steam turbines are governed by which of the following methods?

a)      Throttle governing

b)     Nozzle control governing

c)      By pass governing

d)     All of the above

(12) The thermal efficiency of the engine with condenser as compared to without condenser, for a given pressure and temperature of steam is

a)      Higher

b)     Lower

c)      same as long as initial pressure and temperature is unchanged

d)     None of the above

(13) In a shell and tube surface condenser

a)      Steam and cooling water mix to give the condensate

b)     Cooling water passes through the tubes and steam surrounds them

c)      Steam passes through the cooling water surrounds them

d)     All of the above varying with the situation

(14) Vacuum efficiency of a condenser is ratio of

a)      Actual vacuum in condenser with air present /Theoretical vacuum in condenser with no air present

b)     Theoretical vacuum in condenser with no air present /Actual vacuum in condenser with air present

c)      (Partial pressure of vapour + partial pressure of air present)/ Partial pressure of vapour only

d)     Partial pressure of vapour only/( Partial pressure of vapour + partial pressure of air pressure)

(15) In a steam power plant the function of a condenser is

a)      To maintain pressure below atmospheric to increase work output from the prime mover

b)     To receive large volumes of steam exhausted from steam prime mover

c)      To condense large volumes of steam to water which may be used again in boiler

d)     All of the above

(16) Pipes carrying steam are generally made up of

a)      Steel

b)     Cast iron

c)      Copper

d)     Aluminum

(17) Steam turbines commonly used in steam power station are

a)      Condensing type

b)     Non-condensing type

c)      None of the above

d)     Gaseous type

(18) Economizer’s improves boiler efficiency by

a)      1 to 5%

b)     4 to 10%

c)      10 to 12%

d)     15 to 20%

(19) In steam power station the choice of high temperature fan is for

a)      Increasing the efficiency of boiler alone

b)     Increasing the efficiency of turbine alone

c)      Increasing overall efficiency

d)     None of the above

(20) Capacity of turbine and generator are related as

a)      Turbine kW= generator kW / Generator efficiency

b)     Turbine kW= generator kW x generator efficiency

c)      Turbine kW= generator kW

d)     Turbine kW=(generator kW)2

(21) Superheating of steam is desirable for

a)      Increasing the efficiency of Rankine cycle

b)     Reducing initial condensation losses

c)      Avoiding too high moisture in the last stage of turbine

d)     All of the above

(22) The thermal efficiency of a gas turbine cycle with ideal regenerative heat exchanger is

a)      Equal to work ratio

b)     Less than work ratio

c)      More than work ratio

d)     Unpredictable

(23) The presence of air in a condenser

a)      Increases the pressure in the condenser and decreases the condensing coefficient

b)     Decreases the pressure in the condenser but increases the condensing coefficient

c)      Increases the pressure in the condenser as well as the condensing coefficient

d)     Decreases the pressure in the condenser as well as the condensing coefficient

(24) In a steam condenser, the partial pressure of steam and air are 0.06 bar and 0.007 bar respectively. The condenser pressure is

a)      0.067 bar

b)     0.06 bar

c)      0.053 bar

d)     0.007 bar

(25) Cooling tower in a steam power station is a device for

a)      Condensing the steam into water

b)     Cooling the exhaust gases coming out of the boiler

c)      Reducing the temperature of superheated steam

d)     Reducing the temperature of cooling water used in condenser

(26) With the reference to supersaturated flow through a steam nozzle, which of the following statements are true?

1.       Steam is sub-cooled

2.       Mass flow rate is more that the equilibrium rate of flow

3.       Index of expansion corresponds to wet steam conditions

4.       There is loss in availability

Select the correct answer using the code below:

(a)   1,2and 3 (b)1 and 2 (c)1 and 4 (d)2,3 and 4

(27) Symmetrical blading is used in a turbine when its degree of reaction is

a)      25%

b)     50%

c)      75%

d)     100%

(28) The degree of reaction of turbine is the ratio of enthalpy drop in

a)      Moving blades to enthalpy drop in the stage

b)     Fixed blades to enthalpy drop in the stage

c)      Moving blades to enthalpy drop in the fixed blades

d)     Fixed blades to enthalpy drop in moving blades

(29) Energy conversion takes places only in one  row of nozzle blades and later the steam glides over the rotor and guide blade rows in case of

a)      De-Laval turbine

b)     Rateau turbine

c)      Parson’s turbine

d)     Curtis turbine

(30) In a reaction turbine the enthalpy drop in the fixed blade ring is 50kJ per kg and the enthalpy drop in the moving blade ring is 25kJ per kg. The degree of reaction of the turbine is

a)      66.7%

b)     50.0%

c)      33.3%

d)     6.0%

(31) Efficiency of nozzle governed turbine is affected mainly by losses due to

a)      Partial admission

b)     Throttling

c)      Inter-stage pressure drop

d)     Condensation in last stages

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

a)      0.4

b)     0.6

c)      0.66

d)     1.66

(33) Running speeds of steam turbines can be brought down to practical limits by which of the following methods?

1)     By using heavy flywheel

2)     By using a quick response governor

3)     By compounding

4)     By reducing fuel feed to the furnace

 Choose the correct answer using given the codes given below:

(a) 3 alone (b) 1, 2, 3 and 4 (c) 1, 2 and 4 (d) 2 and 3

(34) In a surface condenser used in a steam power station, undercooling of condensate is undesirable as this would

a)      Not absorb the gases in steam

b)     Reduce efficiency of the plant

c)      Increases the cooling water requirement

d)     Increase thermal stresses in the condenser

(35) In thermal power plants, the Deaerator is used mainly to

a)      Remove air from condenser

b)     Increase feed water temperature

c)      Reduce steam pressure

d)     Reduce dissolved gases from feed water

(36) The net result of pressure-velocity compounding of steam turbine is

a)      Less number of stages

b)     Large turbine for a given pressure drop

c)      Shorter turbine for a given pressure drop

d)     Low friction loss

(37) For one dimensional isentropic flow in a diverging passage, if the initial static pressure is p1 and the initial Mach number is M1(M1 <1), then for the downstream flow

a)      M2 <M1    ; p2 < p1

b)     M2 < M1  ; p2 > p1

c)      M2 > M1 ; p2 >p1

d)     M2 > M1 ; p2 <p1

(38) Consider the following statements: A convergent –divergent is said to be choked when

1)     Critical pressure is attend at the throat

2)     Velocity at the throat becomes sonic

3)     Exit velocity become supersonic

Of these statements

a)      1,2 and 3 are correct

b)     1 and 2 are correct

c)      2 and 3 are correct

d)     1 and 3 are correct

(39) Thermal efficiency of closed cycle gas turbine plant increases by

a)      Reheating

b)     Intercooling

c)      Regenerator

d)     All of the above

(40) Rateau steam turbine is

a)      Reaction steam turbine

b)     Velocity compounded impulse steam turbine

c)      Pressure compounded impulse steam turbine

d)     Pressure velocity compounded steam turbine

(41) 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)      Under damping

b)     over- damping

c)      choked

d)     none of these

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

a)      internal efficiency

b)     Rankine efficiency

c)      stage efficiency

d)     none of these

(43) The critical pressure ratio for initially wet steam is

a)      0.582

b)     0.546

c)      0.577

d)     0.601

(44) Multi-stage steam turbines are of the

a)      reaction type

b)     velocity compounded type

c)      pressure compounded type

d)     all of these

(45) The steam leaves the nozzle at a

a)      high pressure and a low velocity

b)     low pressure and a high velocity

c)      low pressure and a low velocity

d)     high pressure and a high velocity

(46) 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

(47) Thermal equilibrium means that the flow of steam is

a)      isothermal

b)     hyperbolic

c)      isentropic

d)     Polytropic

(48) The impulse reaction turbine has its driving force

a)      partly as an impulsive force and partly as a reaction force

b)     none of the above

c)      as an impulsive force

d)     as a reaction force

(49) The reheat factor is the ratio of the

a)      cumulative heat drop to the isentropic heat drop

b)     total useful heat drop to the total isentropic heat drop

c)      none of the above

d)     isentropic heat drop to the heat supplied

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

a)      inlet and outlet

b)     inlet and throat

c)      throat and exit

d)     nozzle only

(51) The critical pressure gives the velocity of steam at the throat

a)      less than the velocity of sound

b)     more than the velocity of sound

c)      none of these

d)     equal to the velocity of sound

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

a)      degree of super-saturation

b)     degree of under cooling

c)      degree of superheat

d)     none of these

(53) Which of the following statement is correct?

a)      The friction in the nozzle increases the dryness fraction of steam.

b)     The pressure of steam at throat is called critical pressure.

c)      The expansion of steam in a nozzle follows Rankine cycle.

d)     all of the above

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

a)      pressure and velocity both decreases

b)     pressure decreases while velocity increases

c)      pressure and velocity both increases

d)     pressure increases while velocity decreases

(55) Steam turbines are used for

a)      electric power generation

b)     large marine propulsion

c)      direct drive of fans, compressors, pumps

d)     all of these

(56) Curtis turbine is a

a)      simple reaction turbine

b)     pressure compounded turbine

c)      pressure-velocity compounded turbine

d)     velocity compounded turbine

(57) The flow of steam is super-sonic

a)      at the throat of the nozzle

b)     in the convergent portion of the nozzle

c)      at the entrance to the nozzle

d)     in the divergent portion of the nozzle

(58) Parson’s turbine is a

a)      simple impulse turbine

b)     impulse-reaction turbine

c)      none of these(page-1021)

d)     simple reaction turbine

(59) In a reaction turbine

a)      the pressure and temperature of steam remains constant

b)     the steam is allowed to expand in the nozzle, where it gives a high velocity before it enters the moving blades

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

d)     the steam is expanded from a high pressure to a condenser pressure in one or more nozzles

(60) In a reaction turbine when the degree of reaction is zero, then there is

a)      maximum heat drop in fixed blades

b)     no heat drop in fixed blades

c)      no heat drop in moving blades

d)     maximum heat drop in moving blades

(61) Which of the following statement is wrong?

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

b)     The flow in the convergent portion of the nozzle is sub-sonic.

c)      To increase the velocity of steam above sonic velocity (super-sonic) by expanding steam below the critical pressure, the divergent portion for the nozzle is not necessary.

d)     The flow in the divergent portion of the nozzle is super-sonic points

(62) A steam turbine, in which a part of the steam after partial expansion, is used for process heating and the remaining steam is further expanded for power generation, is known as

a)      back pressure turbine

b)     pass out turbine

c)      impulse turbine

d)     low pressure turbine

(63) Stage efficiency is also known as

a)      gross efficiency

b)     nozzle efficiency

c)      diagram efficiency

d)     none of these

(64) The density of supersaturated steam is about __________ that of the ordinary saturated vapors at the corresponding pressure.

a)      same as

b)     2 times

c)      4 times

d)     8 times

(65) The compounding of turbines is done in order to

a)      reduce speed of rotor

b)     improve efficiency

c)      reduce exit losses

d)     all of these

(66) The effect of friction on the flow of steam through a nozzle is to

a)      decrease the mass flow rate and to increase the wetness of steam

b)     increase the mass flow rate and to increase the exit temperature

c)      increase the exit temperature without any effect on mass flow rate

d)     decrease the mass flow rate and to decrease the wetness of steam

(67) Which of the following statement is correct for steam turbines as compared to reciprocating steam engines?

a)      A steam turbine develops higher speeds

b)     The efficiency of steam turbine is higher 

c)      The steam consumption is less

d)     all of these

(68) The purpose of governing in steam turbines is to

a)      reheat the steam and improve its quality

b)     maintain the speed of the turbine

c)      completely balance against end thrust

d)     reduce the effective heat drop

(69) De-Laval turbines are mostly used

a)      where low speeds are required

b)     for small power purposes and low speeds

c)      for large power purposes

d)     for small power purposes and high speeds

(70) The process of maintaining the speed of the turbine constant for various load conditions, is known as

a)      bleeding

b)     reheating

c)      governing

d)     none of these

(71) Blading efficiency is also known as

a)      stage efficiency

b)     nozzle efficiency

c)      diagram efficiency

d)     none of these

(72) The ratio of the work done on the blades per kg of steam to the total energy supplied per stage per kg of steam is called

a)      nozzle efficiency

b)     mechanical efficiency

c)      stage efficiency

d)     blading efficiency

(73) A condenser in a thermal power plant condenses steam combing out of

a)      Boiler

b)     Super-heater

c)      Economizer

d)     Turbine

(74) Most of the generators in thermal power plants run at

a)      3000 rpm

b)     1500 rpm

c)      1000 rpm

d)     750 rpm

(75) In a thermal power plant cooling towers are used to

a)      condense low pressure steam

b)     cool condensed steam

c)      cool water used in condenser for condensing steam

d)     Cool feed water of boiler

(76) A gas turbine power plant usually suits for

a)      peak load operation

b)     base load operation

c)      casual run

d)     None of the above

(77) A gas turbine works on

a)      Carnot cycle

b)     Brayton cycle

c)      Dual cycle

d)     Rankine cycle

(78) Compressor used in gas turbines is

a)      reciprocating compressor

b)     plunger type compressor

c)      screw compressor

d)     Multistage axial flow compressor

(79) For high flow requirement, pumps are generally operated in

a)      Parallel

b)     Series

c)      Any of the above

d)     None of the above

(80) The operating point in a pumping system is identified by

a)      Point of intersection of system curve and efficiency curve

b)     Point of intersection of pump curve and theoretical power curve

c)      Point of intersection of pump curve and system curve

d)     Cannot be decided by pump characteristic curves

(81) Installation of Variable frequency drives (VFD) allows the motor to be operated with

a)      lower start-up current

b)     higher start-up current

c)      constant current

d)     none of the above

(82) For large capacity centrifugal pumps, design efficiencies are in the range of

a)      Around 70%

b)     Around 85%

c)      Around 95%

d)     Any of above

(83) The most efficient method of flow control in a pumping system is-

a)      Throttling the flow

b)     Speed control

c)      Impeller trimming

d)     None

(84) For  pumping highly viscous fluid, the type of pump generally used is

a)      Centrifugal

b)     Multistage centrifugal

c)      Gear pump

d)     Screw pump

(85) For very high discharge at low pressure type of pump preferred is

a)      Centrifugal

b)     Axial

c)      Reciprocating

d)     Mixed flow

(86) Multistage centrifugal pumps are used to obtain

a)      High discharge

b)     High head

c)      Pumping of  high viscous fluids

d)     High head and high discharge

(87) A hydraulic accumulates normally consist of

a)      Two cylinders, two rams and a storage device

b)     A cylinder and a ram

c)      Two co-axial rams and two cylinders

d)     A cylinder , a piston storage tank and a control valve

(88) In hydraulic coupling as the ratio of the speed driven shaft to driving shaft increases, the efficiency

a)      Decreases

b)     Increases

c)      Remain constant

d)     Is independent of speed rate

(89) In a centrifugal pump, cavitations may occur due to

a)      Acceleration of water in the delivery pipe

b)     Closed delivery pipe

c)      Clearance between piston and cylinder

d)     None of the above

(90) Hydraulic Coupling belongs to the category of

a.       Power absorbing machine

b.       Power developing machine

c.       Energy generating machine

d.       Energy transfer machine