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Combustion Limits in Gas Turbines Chris Lawn Queen Mary, University of London PowerPoint Presentation
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Combustion Limits in Gas Turbines Chris Lawn Queen Mary, University of London

Combustion Limits in Gas Turbines Chris Lawn Queen Mary, University of London

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Combustion Limits in Gas Turbines Chris Lawn Queen Mary, University of London

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  1. CI Oxford, 2006 Combustion Limits in Gas Turbines Chris Lawn Queen Mary, University of London

  2. CI Oxford, 2006 Frank Whittle (1937)

  3. CI Oxford, 2006 • Combustion Limits in Gas Turbines • Background information • Combustion requirements and limits • Some specific combustion topics

  4. CI Oxford, 2006 Annular Combustor (Rolls-Royce, 1996)

  5. CI Oxford, 2006 Air-blast Atomiser

  6. CI Oxford, 2006 Siemens 94.3A Annular Combustion Chamber

  7. Typical Parameters Civil Aero G.TIndustrial G.T CI Oxford, 2006 Fuel Fuel:Air Ratio Pressure Ratios Pressure Compressor Delivery Temps. (T3) Combustor Exit Temps. (T4) Residence time Kerosene (C11H23) Natural Gas (CH4 +) Partially mixed Premixed (?) 0.01-0.03 0.02-0.03 25-45 (2) 15 6-45 bar (0.4) 15 bar 750-950 K (300K) 650 K 1400-1950 K 1550 K 4-7 mS 30 mS

  8. CI Oxford, 2006 Flame Stabilizing and Airflow Pattern (Rolls-Royce, 1996)

  9. CI Oxford, 2006 PRIMARY SECONDARY TERTIARY DILUTION ZONE 25:1 15:1 60:1 Secondary Combustion Combustion/ Dissociation Dilution to Reduce Temp for Turbine Airflow Distribution

  10. CI Oxford, 2006 Secondary Primary Dilution Air Flow 25% 20% 55% AFR 15:1 25:1 60:1 Temp: 800K 2500K 2100K 1800K Turbine Inlet Temp Rise: 1700K1300K 1000K Combustion and Dissociation Secondary Combustion Dilution for temperature suitable for turbine Combustion Chamber Zones

  11. CI Oxford, 2006 Engine Requirements I Combustion Requirements Possible Solutions Concerns Lower specific fuel consumption Lighter Cheaper Longer life Higher T3 and T4 Higher combustion intensity Less complex can More durable can

  12. CI Oxford, 2006 S.f.c Benefits from Improved Thermal Cycle (Rolls-Royce)

  13. CI Oxford, 2006 Engine Requirements I Combustion Requirements Possible Solutions Concerns Higher T materials Ceramic integrity Lower specific fuel consumption Lighter Cheaper Longer life Higher T3 and T4 Higher combustion intensity Less complex can More durable can

  14. CI Oxford, 2006 Combustion Chamber Outer Casing INCO 718 Manifold - Stainless steel Injector - Stainless steel/Stellite 31 Outlet Guide Vane - INCO 718 Combustion Chamber Inner Casing INCO 718 • Combustor - C263 • Head - C263 • Heatshields - C1023 Combustion Components - Materials

  15. CI Oxford, 2006 Engine Requirements I Combustion Requirements Possible Solutions Concerns Higher T materials Tailored T4 distribution Ceramic integrity Flame stability Ignition Lower specific fuel consumption Lighter Cheaper Longer life Higher T3 and T4 Higher combustion intensity Less complex can More durable can

  16. CI Oxford, 2006 Predicted traverse Measured traverse scale: 1450-1850 K scale: 1454 - 1781 K Combustor - annular rig test

  17. CI Oxford, 2006 Flame Stability Diagram (Rolls-Royce, 1996)

  18. CI Oxford, 2006 Engine Requirements I Combustion Requirements Possible Solutions Concerns Lower specific fuel consumption Lighter Cheaper Longer life Higher T3 and T4 Higher combustion intensity Less complex can More durable can Higher T materials Tailored T4 distribution Ceramic integrity Flame stability Ignition/extinction More effective cooling Fewer penetrations Cheaper/lighter materials Better t.b.c.bonding Pressure drop Temperature distribution Durability Coating integrity

  19. CI Oxford, 2006 QMUL Gas Turbine Rig ….showing signs of overheating!

  20. CI Oxford, 2006 Engine Requirements II Combustion Requirements Possible Solutions Combustion Concerns Rich burn/lean quench (staged) Lower pollutant emissions Lower environmental noise Less global warming Cheaper fuel ‘Improved’ combustion Lower C fuels Carbon-neutral fuels

  21. NOx Emissions CO UBHC Idle Max Power CI Oxford, 2006 Emission Characteristics

  22. 1000 100 10 1 Idle A B C CO Emissions g CO/kg fuel CO Limit Full Power NOx Limit 0.1 1 10 100 NOx Emissions gm NOx/kg fuel CI Oxford, 2006

  23. CI Oxford, 2006 Radial staging (courtesy of General Electric) Axial staging (courtesy of Pratt and Whitney) Staged Combustors (Correa, 1998)

  24. CI Oxford, 2006 Twin Annular Premixing Swirler (Mongia, 2006)

  25. CI Oxford, 2006 Engine Requirements II Combustion Requirements Possible Solutions Combustion Concerns Lower pollutant emissions Lower environmental noise Less global warming Cheaper fuel ‘Improved’ combustion Lower C fuels Carbon-neutral fuels Rich burn/lean quench (staged) Flame stability Lean prevaporized premixed Direct lean injection Auto-ignition Humming/Dynamics Unburnt hydro-carbons

  26. Typical Operational Envelope of an Industrial Gas Turbine in Fully Premixed Mode Acoustic Instability EquivalenceRatio Mass Flow Rate CI Oxford, 2006 Typical Operational Envelope in Fully Premixed Mode Typical Operational Envelope in Fully Premixed Mode Typical Operational Envelope in Fully Premixed Mode Acoustic Instability Acoustic Instability Acoustic Instability EquivalenceRatio EquivalenceRatio EquivalenceRatio Mass Flow Rate Mass Flow Rate Mass Flow Rate

  27. CI Oxford, 2006 Engine Requirements II Combustion Requirements Possible Solutions Combustion Concerns Lower pollutant emissions Lower environmental noise Less global warming Cheaper fuel ‘Improved’ combustion Lower C fuels Carbon-neutral fuels Rich burn/lean quench Lean prevaporized premixed Direct lean injection Flame stability Auto-ignition Humming/Dynamics Unburnt hydro-carbons H2 enriched fuels Biomass fuels Gasified coal (industrial) Fuel volume Flame stability Ignition Pollutants

  28. CI Oxford, 2006 • Turbulent Mixing and Stretch • Can flame stabilisation with the new fuels be assured? • Can the temperature distribution at exit be made more uniform or tailored?

  29. CI Oxford, 2006 Flame Stability Diagram (Rolls-Royce, 1996)

  30. CI Oxford, 2006 Similarity Analysis

  31. Assume and If stability is mixing-controlled, the modelling parameter is or If stability is stretch-controlled, the modelling parameter is or c.f. Ballal and Lefebvre (1979) : CI Oxford, 2006

  32. NO CI Oxford, 2006 Stability limit of a well-stirred reactor and of a Pratt and Whitney generic combustor. (Sturgess and Shouse, 1997)

  33. CI Oxford, 2006 • Lean Blow-Out with Fuel Sprays • (Ateshkadi et al., 2000)

  34. CI Oxford, 2006 QMUL Model Burner

  35. CI Oxford, 2006

  36. CI Oxford, 2006

  37. CI Oxford, 2006

  38. CI Oxford, 2006

  39. CI Oxford, 2006

  40. CI Oxford, 2006 f=0.75 f=0.59 , upstream ignition f=0.59, downstream ignition f=0.56 Premixed Flame Images and Predicted Mean Heat Release for Rotary Matrix Burner (Bradley et al., 1998)

  41. CI Oxford, 2006 CH4 CH4/H2 Effect of H2 Addition on Time-averaged OH PLIF Images of a Swirled Premixed Flame (Wicksall et al., 2004)

  42. CI Oxford, 2006 Case I 30º vanes Case II 45º vanes Reynolds averaged flow field in vertical mid-plane Reynolds averaged flow field in horizontal mid-plane Density-weighted temperature in the horizontal mid- plane Large Eddy Simulation of a Tay Combustor (di Mare et al., 2004)

  43. CI Oxford, 2006 • Turbulent Mixing and Stretch • Can flame stabilisation with the new fuels be assured? • Best RANS combustion models may predict adequately. • Can the temperature distribution at exit be made more uniform or tailored? • Probably need ‘inverse’ LES code to configure combustor.

  44. CI Oxford, 2006 Conclusions • Plenty of interesting research relating to gas • turbines still to be done. • Derek Bradley had better keep going!

  45. CI Oxford, 2006 Acknowledgements John Moran Rolls-Royce plc Andy Hewitt RAF Cranwell Cath Goy E.On UK

  46. CI Oxford, 2006 • Turbulence/Chemistry Interactions • Can auto-ignition in LPP be avoided • Can ignition of new fuels be assured (even under altitude relight condition)?

  47. CI Oxford, 2006 Predicted Ignition Delays of Various Natural Gases at T=1254 K (Spadaccini and Colket, 1994)

  48. CI Oxford, 2006 • Mixtures investigated; • Methane/oxygen/75% argon (MOA) (φ=0.5). • Methane(85%)/ethane(15%)/oxygen/75% argon mixtures (MEOA) (φ=0.5). • 2.0 bar< P <3.5 bar • Spark schlieren photography was employed to capture flame images. Auto-ignition Data for Methane/Ethane Mixtures (Gardner, 2005).

  49. CI Oxford, 2006 Minimum Ignition Energy (Lewis and von Elbe, 1987)

  50. CI Oxford, 2006 Minimum Laser Ignition Energy for CH4/Air at 1 bar (Phuoc and White, 1999)