1. Chapter: 08
POWER CYCLES

2. Power CYCLEs

3. A Vapour Power Station: a bird’s eye view
Vapour Power Systems

4. Vapour Power Systems POWER CYCLES:
There are four principal control volumes involving components:
Turbine
Condenser
Pump
Boiler
All energy transfers by work and heat are taken as positive in the directions of the arrows on the schematic and energy balances are written accordingly.
Vapour Power Systems

5. The processes are: Vapour Power Systems VAPOUR POWER CYCLE:
Process~1-2: vapor expands through the turbine developing work
Process~2-3: vapor condenses to liquid through heat transfer to cooling water
Process~3-4: liquid is pumped into the boiler requiring work input
Process~4-1: liquid is heated to saturation and evaporated in the boiler through heat transfer from the energy source
Vapour Power Systems

6. IDEALIZATION:
Born: 1 June 1796, in Palais du Petit-Luxembourg, Paris, France
Died: 24 August, 1832 (age 36) Paris, France
Nationality: French
Fields: Physicist and engineer
Vapour Power Systems

7. Vapour Power Systems CARNOT CYCLE: Four Processes in CARNOT cycle:
Turbine: Isentropic
Condenser: Isothermal
Pump: Isentropic
Boiler: Isothermal
Vapour Power Systems

8. why is this impractical?
CARNOT CYCLE:
why is
this impractical?
Vapour Power Systems

9. Vapour Power Systems Ideal RANKINE CYCLE: Processes in RANKINE cycle:1 2 3 4
Processes in RANKINE cycle:
Turbine: Isentropic
Condenser: Isobaric
Pump: Isentropic
Boiler: Isobaric
Vapour Power Systems

10. Vapour Power Systems Ideal RANKINE CYCLE: Turbine: Isentropic1 2 3 4
Processes in RANKINE cycle:
Turbine: Isentropic
Condenser: Isobaric
Pump: Isentropic
Boiler: Isobaric
Vapour Power Systems

11. Vapour Power Systems Ideal RANKINE CYCLE: Processes in RANKINE cycle:1 2 3 4
Processes in RANKINE cycle:
Turbine: Isentropic
Condenser: Isobaric
Pump: Isentropic
Boiler: Isobaric
Vapour Power Systems

12. Wcycle = Qin – Qout Vapour Power Systems Ideal RANKINE CYCLE:1 2 3 4
Energy Analysis: 1 2 3 4
Wcycle = Qin – Qout
Vapour Power Systems

13. Each component is analyzed as a control volume at steady state.
IDEALIZATION:
Engineering model:
Each component is analyzed as a control volume at steady state.
The turbine and pump operate adiabatically.
Kinetic and potential energy changes are ignored.
Vapour Power Systems

14. Vapour Power Systems Ideal RANKINE CYCLE:
Energy Analysis ¬ Component wise: 1 2 3 4
Vapour Power Systems

15. Vapour Power Systems Ideal RANKINE CYCLE: Performance Parameters:
Net Power output:
Efficiency:
Steam Rate:
Vapour Power Systems

16. Gas
Power
Cycle

17. Gas
Power
Cycle

18. Gas Power Cycle:
 OTTO CYCLE
 DIESEL CYCLE

19. Gas Power Cycles
OTTO CYCLE

20. Gas Power Cycles
Thermodynamic
Analysis

21. Gas Power Cycles

22. Gas Power Cycles
pressure

23. Thermodynamic Analysis
Gas Power Cycles
pressure
Thermodynamic
Analysis
The Diesel cycle is executed in a closed system, and disregarding the changes in kinetic and potential energies

24. Power Cycles
A steam turbine plant operates on Rankine cycle with steam entering turbine at 40 bar, 350ºC and leaving at 0.05 bar. Steam leaving turbine condenses to saturated liquid inside condenser. Feed pump pumps saturated liquid into boiler. Determine the net work per kg of steam and the cycle efficiency assuming all processes to be ideal. Also show cycle on T-s diagram. Also determine pump work per kg of steam considering linear variation of specific volume.
[Ans. Net work per kg of steam = kJ/kg, Cycle efficiency = 36.67%, Pump work per kg of steam = 4.02 kJ/kg]

25. Power Cycles
A four stroke SI engine has the compression ratio of 6 and swept volume of 0.15 m3. Pressure and temperature at the beginning of compression are 98 kPa and 60ºC. Determine the pressure, volume and temperatures at all salient points if heat supplied to it is 150 kJ/kg. Also find out work done, efficiency and mean effective pressure of cycle assuming cp = 1 kJ/kg · K, cv = 0.71 kJ/kg · K. Also plot the cycle on T-S diagram.
[Ans. Net Work = kJ, = 51.17%, m.e.p. = kPa]

26. Power Cycles
In an IC engine using air as working fluid, total 1700 kJ/kg of heat is added during combustion and maximum pressure in cylinder does not exceed 5 MPa. Compare the efficiency of following two cycles used by engine: (a) cycle in which combustion takes place isochorically. (b) cycle in which half of heat is added at constant volume and half at constant pressure. Temperature and pressure at the beginning of compression are 100ºC and 103 kPa. Compression and expansion processes are adiabatic. Specific heat at constant pressure and volume are kJ/kg · K and kJ/kg · K.
[Ans. Otto = 50.83%; mixed = 56.47%]

27. Power Cycles