Steam Boilers, Engines, Nozzles & Turbines MCQ Solved Paper for SSC JHT

1. Thermal efficiency of well maintained boiler will be of the order
A. 40 %
B. 50 %
C. 75 %
D. 90 %
Answer : D

2. The actual vacuum in a condenser is equal to
A. Barometric pressure + actual pressure
B. Barometric pressure - actual pressure
C. Gauge pressure + atmospheric pressure
D. Gauge pressure - atmospheric pressure
Answer : B

3. The process of draining steam from the turbine, at certain points during its expansion and using this steam for heating the feed water in feed water heaters and then supplying it to the boiler is known as
A. Regenerative heating
B. Reheating of steam
C. Bleeding
D. None of these
Answer : C

4. The numbers of fire tubes in a Cochran boiler are
A. 75
B. 115
C. 165
D. 225
Answer : C

5. Proximate analysis of fuel is determination of percentage of
A. Carbon, hydrogen, nitrogen, sulphur, moisture
B. Fixed carbon, ash, volatile matter, moisture
C. Higher calorific value
D. Lower calorific value
Answer : B

6. The efficiency of a pressure-velocity compounded impulse turbine is __________ as compared to pressure compounded impulse turbine.
A. Same
B. Less
C. More
D. None of these
Answer : B

7. The ratio of the energy required to produce the artificial draught (expressed in metres head or J/kg of flue gas) to the mechanical equivalent of extra heat carried away per kg of flue gases due to natural draught, is known as
A. Efficiency of the boiler
B. Efficiency of the chimney
C. Efficiency of the fan
D. Power of the boiler
Answer : B

8. When the cross-section of a nozzle __________ continuously from entrance to exit, it is called a convergent nozzle.
A. Increases
B. Decreases
C. Remain same
D. None of these
Answer : B

9. The diameter of fire tubes in Cochran boiler is of the order of
A. 2 cm
B. 6 cm
C. 8 cm
D. 12 cm
Answer : B

10. The friction present between the steam and the nozzle surfaces reduces the heat drop by
A. 10 to 15 %
B. 15 to 25 %
C. 25 to 40 %
D. 40 to 60 %
Answer : A

11. Coke is produced by
A. Pulverising coal in inert atmosphere
B. Heating wood in a limited supply of air at temperatures below 300°C
C. Strongly heating coal continuously for about 48 hours in the absence of air in a closed vessel
D. Enriching carbon in the coal
Answer : C

12. Curtis turbine is a
A. Simple reaction turbine
B. Velocity compounded turbine
C. Pressure compounded turbine
D. Pressure-velocity compounded turbine
Answer : D

13. Willian's law states that the steam consumption per hour provided with a throttled governor is proportional to (where I.P. = Indicated power)
A. 1/(I.P)
B. 1/(I.P)²
C. I.P.
D. (I.P.)²
Answer : C

14. The three Ts for good combustion are
A. Temperature, time, and turbulence
B. Total air, true fuel, and turbulence
C. Thorough mixing, total air and temperature
D. Total air, time, and temperature
Answer : A

15. A nozzle is said to be a divergent 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
Answer : A

16. The expansion of steam, as it flows over the blades in reaction turbine, represents
A. Isothermal process
B. Isentropic process
C. Throttling process
D. Free expansion process
Answer : B

17. The number of flue tubes in Lancashire boiler is
A. Zero
B. One
C. Two
D. Four
Answer : C

18. The shell diameter and length of locomotive boiler are
A. 1.5 m, 4 m
B. 1.5 m, 6 m
C. 1 m, 4 m
D. 2 m, 4 m
Answer : A

19. The ratio of the actual vacuum to the ideal vacuum in a condenser is called
A. Condenser efficiency
B. Vacuum efficiency
C. Nozzle efficiency
D. Boiler efficiency
Answer : B

20. 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
Answer : D

21. In designing air preheaters, the important design consideration is that
A. Approach temperature should be as low as possible
B. Handling and maintenance should be easier
C. Heat transfer area should be optimum
D. Stack gases should not be cooled to the dew point
Answer : D

22. At very low temperature, the melting and boiling temperatures become equal. This temperature is
A. 373°K
B. 273.16°K
C. 303°K
D. 0°K
Answer : B

23. On Mollier chart, free expansion, or throttling process from high pressure to atmosphere is represented by
A. Horizontal straight line
B. Vertical straight line
C. Straight inclined line
D. Curved line
Answer : A

24. Boiler parameters are expressed by
A. Tonnes/hr. of steam
B. Pressure of steam in kg/cm²
C. Temperature of steam in °C
D. All of the above
Answer : D

25. The draught in locomotive boilers is produced by a
A. Chimney
B. Centrifugal fan
C. Steam jet
D. None of these
Answer : C

26. The shell diameter of a Locomotive boiler is
A. 1 m
B. 1.5 m
C. 2 m
D. 2.5 m
Answer : B

27. In accelerated circulation type boiler
A. Heating takes place at bottom and the water supplied at bottom gets converted into the mixture of steam bubbles and hot water which rise to drum
B. Water is supplied in drum and through down comers located in atmospheric condition it passes to the water wall and rises to drum in the form of mixture of water and steam
C. Feed pump is employed to supplement natural circulation in water wall type furnace
D. Water is converted into steam in one pass without any recirculation
Answer : B

28. At which pressure the properties of water and steam become identical
A. 0.1 kg/cm²
B. 1 kg/cm²
C. 100 kg/cm²
D. 225.6 kg/cm²
Answer : D

29. The blade friction in the impulse turbine reduces the velocity of steam by __________ while it passes over the blades.
A. 10 to 15 %
B. 15 to 20 %
C. 20 to 30 %
D. 30 to 40 %
Answer : A

30. A compound steam engine in which piston rods of high pressure and low pressure cylinders are attached to two different cranks set at 90° to each other, is called
A. Receiver type compound engine
B. Tandem type compound engine
C. Woolf type compound engine
D. Both (A) and (B)
Answer : A

31. The Locomotive boiler has
A. 137 fire tubes and 44 superheated tubes
B. 147 fire tubes and 34 superheated tubes
C. 157 fire tubes and 24 superheated tubes
D. 167 fire tubes and 14 superheated tubes
Answer : C

32. Gusset stays in a boiler are provided to
A. Prevent the bulging of flat surfaces
B. Avoid explosion in furnace
C. Prevent leakage of hot flue gases
D. Support furnace freely from top
Answer : A

33. The fire tubes in a Cochran boiler usually have _________ diameter.
A. 6.25 mm
B. 62.5 mm
C. 72.5 mm
D. 92.5 mm
Answer : B

34. The crown of the fire box is made hemispherical in order to
A. Give maximum space
B. Give maximum strength
C. Withstand pressure inside boiler
D. Resist intense heat in fire box
Answer : D

35. The pressure compounded impulse turbine as compared to velocity compounded turbine require __________ number of stages.
A. Same
B. Less
C. More
D. None of these
Answer : C

36. Throttle governing of steam engines is a method of controlling the engine output by varying
A. Volume of intake steam
B. Pressure of intake steam
C. Temperature of intake steam
D. All of these
Answer : B

37. Water tube boilers are those in which
A. Flue gases pass through tubes and water around it
B. Water passes through the tubes and flue gases around it
C. Work is done during adiabatic expansion
D. Change in enthalpy
Answer : C

38. Pour point of fuel oil is the
A. Lowest temperature at which oil will flow under set condition
B. Storage temperature
C. Temperature at which fuel is pumped through burners
D. Temperature at which oil is transported
Answer : A

39. The capacity of induced draft fan compared to forced draft fan in a boiler is
A. Same
B. More
C. Less
D. Less or more depending on size of boiler
Answer : B

40. Expansion ratio is the ratio of
A. Swept volume to the volume at cut-off
B. Clearance volume to the swept volume
C. Volume at cut-off to the swept volume
D. Swept volume to the clearance volume
Answer : A

41. In cross compounding, the cylinders are arranged
A. Side by side and each cylinder has common piston, connecting rod and crank
B. Side by side and each cylinder has separate piston, connecting rod and crank
C. At 90° and each cylinder has common piston, connecting rod and crank
D. At 90° and each cylinder has separate piston, connecting rod and crank
Answer : B

42. The air pressure at the fuel bed is reduced below that of atmosphere by means of a fan placed at or near the bottom of the chimney to produce a draught. Such a draught is called
A. Natural draught
B. Induced draught
C. Forced draught
D. Balanced draught
Answer : B

43. Which of the following is not a boiler mounting?
A. Blow off cock
B. Feed check valve
C. Economiser
D. Fusible plug
Answer : C

44. The critical pressure ratio (p?/p?) is given by
A. (p?/p?) = [2/(n - 1)] ^{n/(n + 1)}
B. (p?/p?) = [2/(n + 1)] ^n/(n-1)
C. (p?/p?) = [(n - 1)/2] ^{n + (1/n)}
D. (p?/p?) = [(n + 1)/2] ^{n - (1/n)}
Answer : B

45. During polytropic process
A. Heat transfer takes place across cylinder walls
B. Work is done
C. Steam may be wet, dry or superheated after expansion
D. All of the above
Answer : D

46. In a reaction turbine, when steam flows through the moving 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
Answer : C

47. 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 subsonic.
C. The flow in the divergent portion of the nozzle is supersonic.
D. To increase the velocity of steam above sonic velocity (supersonic) by expanding steam below the critical pressure, the divergent portion for the nozzle is not necessary.
Answer : D

48. A single stage impulse turbine with a diameter of 1.2 m runs at 3000 r.p.m. If the blade speed ratio is 0.42, then the inlet velocity of steam will be
A. 79 m/s
B. 188 m/s
C. 450 m/s
D. 900 m/s
Answer : C

49. De-Laval turbine is a
A. Simple impulse turbine
B. Simple reaction turbine
C. Impulse-reaction turbine
D. None of these
Answer : A

50. Evaporative capacity of boiler is expressed as
A. kg of steam produced
B. Steam pressure produced
C. kg of fuel fired
D. kg of steam produced per kg of fuel fifed
Answer : D