unit_2.pptx
Download as PPTX, PDF
0 likes7 views
This document discusses various thermodynamic cycles used in diesel, gas turbine, and combined cycle power plants. It defines the Otto, Diesel, Dual, Brayton, and actual gas turbine cycles. For each cycle, it outlines the key processes, equations, and variables used to calculate efficiency. It notes that the Otto and Diesel cycles are special cases of the more general Dual cycle. The Brayton cycle models the thermodynamics of a gas turbine as an open system. Overall, the document provides a theoretical overview of common thermodynamic cycles applied in different power plant technologies.
unit_2.pptx
- 1. UNIT II DIESEL, GAS TURBINE AND COMBINED CYCLE POWER PLANTS Otto, Diesel, Dual & Brayton Cycle Analysis & Optimisation. Components of Diesel and Gas Turbine power plants. Combined Cycle Power Plants. Integrated Gasifier based Combined Cycle systems.
- 2. Engine Terms Clearance volume Displacement volume Compression ratio
- 3. Engine Terms Mean effective pressure (MEP)
- 4. Otto Cycle Processes of Otto Cycle: Isentropic compression Constant-volume heat addition Isentropic expansion Constant-volume heat rejection
- 5. OTTO CYCLE
- 6. Otto Cycle Ideal Otto Cycle Four internally reversible processes 1-2 Isentropic compression 2-3 Constant-volume heat addition 3-4 Isentropic expansion 4-1 Constant-volume heat rejection
- 7. Otto Cycle Closed system, pe, ke 0 Energy balance (cold air std)
- 8. Otto Cycle Thermal efficiency of ideal Otto cycle: Since V2= V3 and V4 = V1 Where r is compression ratio k is ratio of specific heats
- 9. Otto Cycle
- 15. Spark and Compression Ignition Spark (Otto), air-fuel mixture compressed (constant-volume heat addition) Compression (Diesel), air compressed, then fuel added (constant-pressure heat addition)
- 16. DIESEL CYCLE
- 17. Diesel Cycle Processes of Diesel cycle: Isentropic compression Constant-pressure heat addition Isentropic expansion Constant-volume heat rejection
- 18. Diesel Cycle For ideal diesel cycle With cold air assumptions
- 19. Diesel Cycle Cut off ratio rc Efficiency becomes
- 25. Process 1 2 Isentropic compression Process 2 2.5 Constant volume heat addition Process 2.5 3 Constant pressure heat addition Process 3 4 Isentropic expansion Process 4 1 Constant volume heat rejection Dual Cycle Qin Qin Qout 1 1 2 2 2.5 2.5 3 3 4 4 ) ( ) ( ) ( ) ( 5 . 2 3 2 5 . 2 5 . 2 3 2 5 . 2 T T c T T c h h u u m Q p v in
- 26. Thermal Efficiency ) ( ) ( 1 1 5 . 2 3 2 5 . 2 1 4 h h u u u u m Q m Q in out cycle Dual 1 ) 1 ( 1 1 1 1 c k c k c const Dual r k r r v 1 1 1 k Otto r 1 1 1 1 1 1 c k c k const c Diesel r r k r V Note, the Otto cycle (rc=1) and the Diesel cycle (=1) are special cases: 2 3 5 . 2 3 and where P P v v rc
- 27. The use of the Dual cycle requires information about either: i) the fractions of constant volume and constant pressure heat addition (common assumption is to equally split the heat addition), or ii) maximum pressure P3. Transformation of rc and into more natural variables yields 1 1 1 1 1 1 1 1 k r V P Q k k r k in c 1 3 1 P P rk For the same initial conditions P1, V1 and the same compression ratio: Diesel Dual Otto For the same initial conditions P1, V1 and the same peak pressure P3 (actual design limitation in engines): otto Dual Diesel
- 29. Brayton Cycle Gas turbine cycle Open vs closed system model
- 30. Brayton Cycle Four internally reversible processes 1-2 Isentropic Compression (compressor) 2-3 Constant-pressure heat addition 3-4 Isentropic expansion (turbine) 4-1 Constant-pressure heat rejection
- 31. Brayton Cycle Analyze as steady-flow process So With cold-air-standard assumptions
- 32. Brayton Cycle Since processes 1-2 and 3-4 are isentropic, P2 = P3 and P4 = P1 where
- 33. Brayton Cycle
- 34. Brayton Cycle Back work ratio Improvements in gas turbines Combustion temp Machinery component efficiencies Adding modifications to basic cycle
- 39. Actual Gas-Turbine Cycles For actual gas turbines, compressor and turbine are not isentropic