Steam boilers, engines, nozzles and turbines - Mechanical Engineering test

Steam boilers, engines, nozzles and turbines - Mechanical Engineering test

1) Fire tube boilers are those in which

a) Water passes through the tubes and flue gases surround them.
b) Tubes are laid vertically.
c) Forced circulation takes place.
d) Flue gases pass through tubes and water surrounds them.

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2) What is the basic purpose of a drum in a boiler?

a) To remove salt from water.
b) To serve as a storage of steam.
c) To separate steam from water.
d) All of these,

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3) In a boiler a blow off cock is used to

a) Blow air into the furnace.
b) Allow flue gases to escape to the chimney.
c) Drain off water resulting from partial condensation of steam.
d) Remove sludge from the boiler.

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4) The size of boiler tubes is specified by

a) Outside diameter and inside diameter.
b) Mean diameter and thickness.
c) Outside diameter and thickness.
d) Inside diameter and thickness.

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5) Blow down from the boiler drum is carried out to

a) Lower steam pressure.
b) Increase steam temperature.
c) Control the solids concentration in boiler water.
d) All of the above.

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6) The economiser unit of a boiler is located between

a) Super heater and air preheater.
b) Air preheater and chimney.
c) Forced draught fan and furnace.
d) Furnace and super heater.

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7) Presence of sulphur is coal causes

a) Corrosion of air heaters.
b) Ash precipitation.
c) Clinkering and slagging.
d) All of the above.

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8) Locomotive boiler is a

a) Single tube, vertical, externally fired and stationery boiler.
b) Single tube, horizontal, internally fired and stationery boiler.
c) Multi-tubular, horizontal, internally fired and mobile boiler.
d) Multi-tubular, horizontal, externally fired and stationary boiler.

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9) The natural draught in a boiler is produced due to

a) The fact that pressure at the grate due to cold column is higher than the pressure at chimney base due to hot column.
b) The fact that furnace gases being light go through the chimney giving place to cold air from outside to rush in.
c) The facts that at the chimney top the pressure is more than its environmental pressure.
d) All of these.

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10) The draught produced, for a given height of the chimney and given mean temperature of chimney gases

a) May increase or decrease with increase in outside air temperature.
b) Remains the same irrespective of outside air temperature.
c) Increases with increase in outside air temperature.
d) Decreases with increase in outside air temperature.

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11) The power of induced draught fan as compared to forced draught fan is ……………for the same draught.

a) Less.
b) More.
c) Same.
d) Not predictable.

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12) The pressure at the furnace is minimum in case of

a) Natural draught system.
b) Balanced draught system.
c) Induced draught system.
d) Forced draught system.

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13) Equivalent evaporation is

a) The ratio of heat actually used in producing the steam to the heat liberated in the furnace.
b) The amount of water evaporated or steam produced in kg per kg of fuel burnt.
c) The amount of water evaporated ‘from and at 100°C’ into dry and saturated steam.
d) None of these.

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14) The amount of water evaporated in kg per kg of fuel burnt is called

a) Evaporating capacity of a boiler.
b) Equivalent evaporation from and at 100°C.
c) Boiler efficiency.
d) None of these.

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15) The rate of steam consumption for throttle governing

a) Varies inversely as the speed of the engine.
b) Varies directly as the speed of engine.
c) Is directly proportional to I.P. of the engine.
d) Is inversely proportional to I.P. of the engine.

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16) Tandem compound steam engines have

a) Only one crank with no phase difference.
b) Two cranks with no phase difference.
c) Two cranks at 90°C phase difference.
d) Two cranks at 180°C phase difference.

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17) Compound steam engines governing is done by

a) Cut off variation in high pressure cylinder.
b) Cut off variations simultaneously in high pressure and low pressure cylinders.
c) Throttling steam to high pressure cylinder.
d) All of the above methods.

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18) The saturation curve of a steams engine represent

a) The saturated state of steam.
b) The quantum of missing quantity.
c) The curve drawn through the points of dry volume.
d) None of these.

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19) All steam engines work on

a) First law of thermodynamics.
b) Second law of thermodynamics.
c) Principle of conservation of energy.
d) None of these.

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20) Missing quantity per stroke is equal to ……………..in steam engine.

a) Cylinder feed-indicated weight of steam.
b) Cylinder feed-weight of cushion steam.
c) Indicated weight of steam-weight of cushion steam.
d) None of these.

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21) In Rankine cycle the expansion of steam is assumed to be

a) Isothermal.
b) Adiabatic.
c) Polytropic.
d) Hyperbolic.

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22) A governor on a steam engine is used

a) To control pressure of steam.
b) To regulate load.
c) To provide safety of engine under abnormal conditions.
d) To maintain a fairly constant speed for all loads.

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23) In a flow through a nozzle the mach number is more than unity

a) At the throat.
b) In the converging.
c) In the diverging section.
d) None of these.

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24) Which of the following aspects is invalid for a convergent-divergent nozzle?

a) Supersonic flow in the divergent portion.
b) Subsonic flow in convergent portion.
c) Velocity of flow equals sonic velocity at the throat.
d) Flow may reverse back from supersonic to subsonic value towards the nozzle exit.

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25) In a nozzle the effect of super saturation is

a) To increase the entropy.
b) To increase the heat drop.
c) To decrease dryness fraction of steam.
d) To decrease specific volume of steam.

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26) The steam nozzle is said to be choked when

a) There is stoppage of flow through the nozzle.
b) Flow rate cannot be increased by increasing the supply pressure.
c) Shock effect is felt in the nozzle.
d) Critical conditions prevail and mass flow rate is maximum.

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27) In a nozzle, shock waves generally occur

a) At entry to nozzle.
b) At the nozzle throat.
c) In the convergent section of the nozzle.
d) In the divergent section of the nozzle.

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28) In case of impulse steam turbine

a) There is enthalpy drop in nozzles.
b) There is enthalpy drop in fixed and moving blades.
c) There is enthalpy drop only in moving blades.
d) None of these.

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29) In case of reaction steam turbine

a) There is enthalpy drop only in moving blades.
b) There is enthalpy drop only in fixed blades.
c) There is enthalpy drop both in fixed and moving blades.
d) None of these.

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30) The degree of reaction is …... for Parson’s reaction steam turbine.

a) 50%
b) 100%
c) 60%
d) 75%

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31) Reheat factor in steam turbines depends on

a) Stage efficiency only.
b) Exit pressure only.
c) Initial pressure and temperature only.
d) All of these.

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32) In steam turbines the reheat factor

a) Remains same irrespective of number of stages.
b) Decreases with the increase in number of stages.
c) Increases with the increase in number of stages.
d) None of these.

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33) ……………..is an essential merit of a reaction turbine.

a) Greater work output.
b) Capability to have expansions in stages.
c) High diagram efficiency.
d) Blade speeds lie in the useful range.

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34) The steam turbines are governed to

a) Completely balance.
b) Reduce effective heat drop.
c) Maintain the speed of the turbine.
d) Reheat steam and improve its quality.

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35) The effect of bleeding is

a) The boiler is supplied with hot water.
b) It increases the thermodynamic efficiency of the turbine.
c) It decreases the power developed by the turbine.
d) All of these.

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36) What is the purpose of reheating of steam in a turbine?

a) It reduces wear on blade.
b) It increases the efficiency of the turbine.
c) It increases the work done through the turbine.
d) All of these.

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37) In jet type condensers

a) Cooling water passes through tubes and steam surrounds them.
b) Steam passes through tubes and cooling water surrounds them.
c) Steam and cooling water mix.
d) Steam and cooling water do not mix.

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38) In a shell and tube surface condenser

a) Steam passes through the cooling tubes and cooling water surrounds them.
b) Cooling water passes through the tubes and steam surrounds them.
c) Steam and cooling water mix to give the condensate.
d) All the above varying with situation.

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39) Evaporation type of condenser has

a) Water in pipes surrounded by steam.
b) Steam in pipes surrounded by water.
c) Either of the above.
d) None of the above.

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40) In a jet condenser the maximum limit of vacuum attained is about ………….of Hg.

a) 650mm
b) 550mm
c) 500mm
d) 700mm

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