Steam Boilers, Engines, Nozzles and Turbines LAB VIVA Questions :-
PROPERTIES OF STEAM:
1. At a pressure of 0.006112 bar, the melting and boiling temperature become equal and the change of phase ice-water-steam is shown on T-v diagram by ________.
2. At a pressure of 0.006112 bar and temperature of 273.16°K, ice, water and steam coexist and such a condition is represented by ________.
3. At pressures lower than 0.006112 bar, the ice ______to steam.
4. At a pressure of 221.2 bar and temperature of 374.15°C, the change of volume accompanying evaporation is _______.
5. The condition of p = 221.2 bar and t = 374.15°C is called_______.
6. At critical point, the latent heat of vaporisation is ______.
7. There is no definite transition from liquid to vapour and two phases can’t be distinguished visually.
8. Superheated steam behaves like______gas.
9. At very high pressures, the volumes of saturated water _______ by omitted from calculations.
10. During throttling process________remains unchanged.
11. Diagram showing properties of steam on enthalpy vs. entropy chart.
12. With increase in pressure, the enthalpy of evaporation ________.
13. With increase in pressure, the enthalpy of dry saturated steam ________.
14. For measuring dryness fraction of the order of 0.98, _______calorimeter is used.
STEAM BOILERS:
15. Units used with pulverised coal fired boilers in order to reduce atmospheric pollution.
16. The coal and air pass directly from the pulveriser to the burners and the desired firing rate is regulated by the ratio of pulverising.
17. Type of pulveriser adaptable to highly abrasive fuels having high silica content.
18. It mixes and directs the flow of fuel and air so as to ensure rapid ignition and complete combustion.
19. Air initially mixed with the fuel to obtain rapid ignition and to act as a conveyor for the fuel.
20. Air introduced to the burners outside of the primary-air ports, in order to ensure complete combustion.
21. Type of atomiser used for providing an operating range of 10 to 1 in oil burners.
22. The burner tips in corner fired boiler are tilted to control
23. A furnace designed to burn low-ash-fusion coals and to retain most of the coal ash in the slag.
24. The pressure limit upto which drum type natural or assisted circulation boiler are restricted because of circulation of steam-separation characteristics.
25. Component to add heat to steam after evaporation in furnace.
26. Component to remove heat from the moderately low temperature combustion gases after superheat/reheat sections of the boiler unit.
27. Type of air heater in which the stationary metal parts form a separating boundary between the heating and cooling fluids, and the heat passes by conduction through the metal wall.
28. Type of air heater in which heat transferring members are moved alternately through the gas and air streams undergoing successive heating and cooling cycles and transferring heat by the internal storage capacity of the members.
29. Circulation produced in boiler by the difference in the densities of the water in the unheated down-comers and the steam-water mixture in the heated tubes.
30. In assisted circulation type of boilers, the quantity of water pumped (usually) in comparison to the amount of steam evaporated is
31. Boiler requiring no steam drum and using relatively small-diameter tubes.
32. Effect caused by the difference in densities of flue gases in chimney and surrounding air.
33. The greatest factor in the corrosion of steel surfaces in contact with water in boilers is
34. Dissolved oxygen is removed from feedwater for boiler in
35. Corrosion in boilers is prevented or minimised by maintaining boiler water.
36. The pH of a water sample can be determined accurately by the measurement of its
37. The elimination of hardness in boiler water is necessary to prevent
STEAM ENGINE:
38. Steam engines depend for their operation on the power of the steam.
39. The expansion ratio in steam engines is limited due to
40. The ratio of expansion in simple steam engines is of the order of
41. The efficiency of steam engines is dependend largely on the value of the
42. The ratio of area of actual indicator diagram to the area of theoretical card is called
43. The mechanical efficiency of steam increases as the load
44. Condensation losses in steam engine are related to the temperature difference existing in the cylinder which can be reduced by using
45. result in overall improvement in performance and water rate, and also reduces the cylinder condensation.
46. The efficiency of steam engines is expressed in terms of _______.
47. In ______arrangement of steam engine, the temperature of the residual steam at the end of compression is high which results in economy of steam.
48. Steam engine economy may be improved by separation of inlet and outlet ports, applying steam jackets to cylinders and heads, and using
49. Losses in steam engine cylinders are due to incomplete expansion, initial condensation, radiation and
50 cycle is the accepted thermodynamic standard for comparing the performance of the steam engine.
51. There is no compression or clearance in the _______.
STEAM TURBINES:
52. According to details of design, the steam turbines may be classified as impulse or reaction.
53. The total pressure drop for the stage is taken across the nozzles.
54. The flow through the rotor blades is substantially at constant static pressure.
55. Multivelocity stages occur in ______ turbine.
56. The total pressure drop assigned to the stage is divided equally between the stationary blades and the rotor blades.
57. The ______ buckets do much more turning of the steam.
58. Blade length/steam passage width.
59. Leakage loss of steam between inner circumference of stationary element and rotor is minimised by maintaining minimum practical clearance and by use of
60. In stages with short blades, the best net efficiency obtains with near design.
61. The presence of moisture in the steam causes extra
62. The ratio of total internal used energy to the isentropic available energy.
63. In condensing turbines expanding to high vacuum, the ratio of volume of steam at exhaust to that at inlet is around
64 keep the rotor turning at slow speed to maintain uniform temperature when the turbine is shutdown and cooling.
65 on the turbine rotor is caused by pressure and velocity differences across the rotor blades.
66. The performance of central-station turbine-generators is generally expressed as _______.
67. The unit of heat rate is _______.
ANSWERS::
1. a straight line
2. triple point line
3. sublimates
4. zero
5. critical point
6. zero
7. at critical point and above
8. perfect
9. can not
10. enthalpy
11. Mollier diagram
12. decreases
13. decreases
14. throttling
15. electrostatic precipitators
16. direct fired system
17. slow-speed, rotating drum type
18. burner
19. Primary air
20. Secondary air
21. Steam and air type
22. steam temperature
23. cyclone
24. 183kgf/cm2
25. superheater
26. economiser
27. recuperative
28. regenerative
29. natural
30. 4-6 times
31. once through type
32. stack
33. dissolved oxygen
34. deaerator
35. alkaline
36. electrical potential
37. scale
38. expansive
39. practical losses
40. 4
41. ratio of expansion
42. diagram factor
43. increases
44. cylinders in series
45. superheating
46. kg of steam per h.p. hour
47. uniflow
48. multiple expansion
49. throttling
50. Rankine
51. Rankine cycle
52. stage
53. impulse stage
54. impulse
55. curtis
56. reaction stage
57. impulse
58. aspect ratio
59. labyrinth packings
60. impulse
61. losses
62. internal efficiency
63. 1000
64. turning gear
65. axial thrust
66. heat rate
67. kcal/kWhr