1. Thermal Power Engineering U5MEA21
Prepared by
Mr.velu.r & Mr.babu.j.m,
Assistant professor,mechanical department,
Veltech dr.rr & dr.sr technical university.

2. UNIT I STEAM GENERATORS

3. Steam Generators (Boilers)
Types and classification Fire tube – Water tube
Low Pressure – High pressure Stationary – Mobile
Power generation – Processing Coal fired – Oil and gas fired Vertical – Inclined – Horizontal

4. Low Pressure Boilers Fire tube boilers Cochran Cornish Lancashire
Marine
Locomotive

5. Simple vertical Boiler

6. Cochran Boiler

7. Lancashire Boiler

8. Cornish Boiler

9. Locomotive Boiler

10. Locomotive – to haul a train

11. Low Pressure Boilers Water Tube Boilers Simple vertical boiler
Babcock Wilcox
Stirling

12. Babcock and Wilcox boiler

13. Babcock – Wilcox Boiler

14. Stirling Boiler principle

15. Stirling Boiler

16. Mountings – Safety fittings; must – without these boiler should not operate
Safety valve
Pressure gauge
Water level indicator
Steam stop valve
Fusible plug
Manholes, handholes
Blow off cock
Feed pump

17. Safety Valve – To release steam and reduce pressure inside boiler

18. Fusible Plug- melts and drops in combustion chamber making water to enter from water space to fire space

19. Water level Indicator – To show water level inside boiler

20. Steam stop valve – To permit or stop steam from boiler

21. Pressure gauge – To indicate the steam pressure inside the boiler

22. Blow-off cock – to shut down boiler and remove mud, rust, sludge etc

23. Accessories
Superheater
Economiser
Steam water separator
Air preheater

24. Economiser – To recover heat from waste flue gases and heat feed water

25. Steam water separator – to separate moisture (water) from steam

26. air preheater – to preheat the air entering into the combustion chamber – heated by flue gases

27. Boiler Trial Performance testing To find Equivalent evaporation
Boiler efficiency
Losses
Heat balance sheet

28. Equivalent Evaporation
Factor of evaporation
h-hf /2257
E = total heat required to evaporate feed water from and at 100oC
E= me(h-hf)/2257, where me is mass of steam actualy produced in kg/kg of fuel or like units
Efficiency of boiler = ms (h-hf)/mf.C

29. Criteria for selection of boilers
Capacity required, pressure and temperature of steam
Base load or peak load
Place of erection of boiler
Fuel and water available (Quality and quantity)
Probable permanency of the station

30. Losses in a boiler Losses due to unburnt coal
Losses due to moisture present in coal
Losses due to sulphur like elements
Heat lost in flue gases
Radiation heat loss

31. Difference between a Fire tube boiler and a Water tube boiler
Low pressure boiler p<80 bar
High pressure boiler p>80 bar
Shell must be present
Shell need not be there
Forced circulation very difficult
Forced circulation makes the heat transfer more effective
Explosion risk less
Explosion risk more
Transportation and Erection difficult
Transportation and Erection easy
Fixed capacity
Capacity can be increased by increasing the pressure
Scale formation and thus less heat transfer
Forced circulation and less or no scale formation
Lancashire bolier, Cochran boiler
Babcock and Wilcox boiler

32. La Mont Boiler – High pressure boiler (beyond the syllabus)

33. UNIT 2
STEAM NOZZLES

34. Types of Steam Nozzles
A convergent nozzle A divergent nozzle Steam out A convergent – divergent nozzle

35. Applications of a steam nozzle
In steam turbines to increase velocity of steam
In steam injectors to pump water into the boiler
In processing plants for drying the chemicals etc

36. Equation for velocity of steam through the nozzle
Isentropic expansion
C2 = [2(h1-h2)]1/2 m/s
where C2 is the exit velocity,
h1 and h2 are the enthalpy of steam at inlet of the nozzle and at the exit of the nozzle respectively (in J)

37. Velocity equation

38. Velocity equation and Mass equation

39. Nozzle friction and efficiency

40. Meta stable flow or supersaturated flow
Effect of friction
To increase dryness fraction of the steam
To reduce the total heat drop and thus reduce the exit velocity of the steam coming out of the nozzle

41. Problem

42. Relation between density, velocity and Area

44. Forms of nozzle for various types of flows

45. Steam Injector (for pumping water)

46. Problem

47. Steam Expansion in a nozzle

48. UNIT 3
STEAM TURBINES

49. A Parson turbine

50. A steam turbine
Rotary machine to convert heat energy of steam in to shaft work
Impulse turbine and reaction turbine
Used in power plants
First reaction turbine is hero engine
Single stage – multistage
Governing is needed to control the speed vis- à-vis load

51. Combined Velocity diagram

52. Pressure Compounding

53. Velocity Compounding

54. Pressure – Velocity compounding

55. Throttle governing

56. Nozzle governing

57. Bypass governing

58. COMPARISON ROTARY Balancing and lubrication easy Less vibration
Less linkages
Does not Need flywheel
Used in power plant
Less losses
Costly
RECIPROCATORY
Balancing and lubrication difficult
More vibration
More linkages
Need flywheel
Used in only small engines
More losses
cheap
Steam TURBINE
STEAM ENGINE

59. COMPARISON Works on reaction principle Big in size
Works on impulse principle
Small in size
More losses
More power per stage
Nozzle present
Symmetric blades
Does not need pressure tight casing
Flow only through nozzle
Cheap
DeLaval turbine
Works on reaction principle
Big in size
Less power per stage
No nozzles only guide blades
Aerofoil blades
Air tight casing needed
Flow through the entire annular space
Costly
Parson turbine
Impulse TURBINE
Reaction turbine

60. UNIT 4
I C ENGINES

61. Internal combustion engines
A reciprocating device that converts heat energy into shaft work
As per thermodynamic cycle
Otto cycle
Diesel cycle
Dual Cycle
As per Stroke
Two stroke
Four stroke

62. Types (continued) Vertical engines Horizontal ingines Incline engines
Inline engines
Radial engines
V-engines
Opposed cylinder engines
Single cylinder
Multi cylinder engines

63. applications Automobiles Agricultural equipments Power generation
Earth movers
Marine applications
Rail locomotives

64. P-v diagram of si engine

65. P-v diagram of ci engine

66. Working of 4-stroke spark ignition engine

67. Valve Timing Diagram

68. Working of 2-stroke compression ignition engine

69. P-v diagram of 2-stroke engine

70. Port timing diagram of a 2-stroke IC engine

71. Cooling system
To Cool the IC engine

72. lubrication
To lubricate the moving parts of an IC Engine

73. Fuel injection pump
To inject diesel into the combustion chamber at very high pressure for atomisation

74. Fuel injector

75. Scavanging
Pushing out the burnt gases out of the cylinder before taking the fresh charge is called as scavenging.
In 4-stroke engine scavenging takes place in exhaust stroke.
If scavenging is poor, then power produced will be reduced

76. supercharging
Supplying more air during the inlet or suction stroke by pressure is called supercharging.
This is done to improve volumetric efficiency
This increases the net power produced by the engine.
Supercharging is carried out by turbocharger, which is driven by the exhaust gas from the engine

77. Detonation
In SI engine ignition takes place before the TDC of the piston due to certain circumstances (like preignition). This is called as detonation.
Isooctane has zero detonation characteristics and any fuel is measured in octane rating.

78. Knocking
Due to the combustion, different wave fronts are formed inside the cylinder and the wavefronts compress the already compressed fuel. This increases the temperature and the compressed but yet to be ignited fuel burns and opposes the wave front thus producing knocking
Knocking is measured in Cetane rating

79. Performance of an ic engine
To find the power and performance characteristics, the performance tests such as brake power test, Morse test are conducted
Indicated power (IP) is the power produced inside the cylinder – measured by indicator
IP = pLANk/60 (Watt)
Brake power (BP) is the power obtained in a dynamometer outside the flywheel shaft
BP = 2πNT/60 (Watt)
Friction power = indicated power – Brake power

80. efficiencies Air standard efficiency Indicated thermal efficiency
Brake thermal efficiency
Mechanical efficiency
Volumetric efficiency

81. Losses in an ic engine Heat carried out by exhaust gases
Heat carried out by cooling fluid
Heat lost due to friction power
Unaccountable losses

82. Petrol engine – Diesel engine Comparison
SI ENGINE
Compression ratio 1:8
Petrol fuel
Spark ignition
Carburetor
Need current for ignition
More air std efficiency
Lighter cylinder
Less heat and vibration
Lighter flywheel
Cooling, balancing and lubrication easy
CI ENGINE
Compression ratio 1:22
Diesel fuel
Compression ignition
Fuel injector
Does not need current
Less air std efficiency
Heavier cylinder
Vibration and heat more
Heavier flywheel
Cooling, balancing and lubrication difficult

83. 2-stroke engine – 4-stroke engine Comparison
One power stroke in one revolution
Lighter flywheel
Suitable for small engines
Lubrication difficult
High specific power
High speed
More pollution, scavenging difficult
Starting easy
Special design for piston
No valves only ports
High specific fuel consumption
Low volumetric efficiency
One power stroke in TWO revolutions
Heavier flywheel
Suitable for heavy engines
Lubrication easy
Low specific power
Low speed
Less pollution, separate exhaust stroke
Starting difficult
Simple design for piston
valves present
Low specific fuel consumption
High volumetric efficiency

84. UNIT 5
GAS TURBINES

85. Gas turbine

86. A gas turbine

88. Gas Turbine
A rotary device, (a prime mover) transforms heat energy of gases into mechanical work or shaft work
An external combustion engine
Works on Brayton thermodynamic cycle (or reverese Joule’s cycle)
Used in airplanes, turbochargers and power generation
Two types of gas turbines are
Open cycle
Closed cycle

89. Brayton Thermodynamic Cycle
Processes
1-2 Isentropic compression
2-3 Constant pressure heat addition
3-4 Isentropic expansion (power process)
4-1 constant pressure heat rejection

90. Open cycle gas turbine Fuel Gas Turbine Generator Starting motor
Air Compressor
Exhaust gases
Atmospheric air

91. Closed cycle gas turbine

92. Comparison between Open cycle and closed cycle gas turbine
Mixing type combustion chamber
Air and gas as medium
Aviation fuel as fuel
Relatively cheap
High specific power
Used in airplanes
Power cannot be increased
Closed cycle
Non-mixing type
Helium or liquid sodium medium
Any low quality fuel
Costly
Low specific power
Power plants
Power can be increased by increasing the pressure ratio

93. Comparison between Gas Turbine and an IC Engine
Rotary device
High speed prime mover
Aviation fuel as fuel
Less balancing
Difficult to start
Used in airplanes
Lubrication easy
No flywheel
Governing difficult
IC Engine
Reciprocating device
Low speed
Petrol, diesel as fuel
Complicated balancing
Easy to start
Automobiles, Power plants
Lubrication difficult
Flywheel must
Governing easy

94. Work done and heat supplied
Net Power Produced =
Work done by Turbine – Work done on compressor
W = Wt – Wc
Work ratio = W /Wt
Efficiency of the Turbine system
= (Qs – Qr) /Qs
= [(T3-T2) – (T4-T1)] / (T3 – T2)
= 1 – (1 / rp (γ-1)/ γ)

95. Methods to improve efficiency of a gas turbine system
Intercooling
Reheating
Regeneration
Combination of the above

96. Intercooling

97. Reheating

98. Regeneration

99. Rotary compressor

100. Combustion chamber

101. THANK YOU