GMRC 2008 - The Parabolic Burning Curve.ppt
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The document discusses the parabolic burning curve, which shows the relationship between air-fuel ratio and combustion properties for different gases like methane and ethane. It notes key aspects like the lower explosion limit (LEL), upper explosion limit (UEL), and stoichiometric ratio. The curve is important for understanding combustion characteristics in engines and how mixtures outside the explosive range will not burn properly. It also discusses applications of rich-burn versus lean-burn engines and how the curve varies slightly between different fuel gases.
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GMRC 2008 - The Parabolic Burning Curve.ppt
- 1. The Parabolic Burning Curve 2008 GMRC October 6-8, 2008 Albuquerque, NM ACTT a Division of Compressor Engineering Corporation www.classactt.com Presented by: Randy L. Anderson
- 2. Introduction to the Parabolic Burning Curve Peak firing pressure Different engines operations Emissions Engine balance Detonation Misfires Dead cylinders Flame front velocity Lower explosion limits Upper explosion limits Stoichiometric mixtures
- 3. Why is it so important? Simple to explain Straightforward Easy to remember Critical to mastering combustion characteristics in a reciprocating engine
- 4. Opening Statement I have never been able to identify the original source of this information. Whoever you were, thank you! This is not intended to be a synopsis of trapped equivalence ratio, adiabatic flame temperatures or any other study of the basic laws of thermodynamics but rather a primer to help anyone understand the basic of air-fuel ratio and its affect on combustion and an instrument to help anyone to remember this information forever. And most importantly, in 35 years it has never led me astray.
- 5. Cornerstones It is based on a volumetric air-fuel ratio It is based on methane, CH4, with approximately 913 Btu (LHV) It is based on spark ignition and not a pre- combustion chamber It is based on the stoichiometry of methane, 9.52:1 or 9.52 parts air to 1 part fuel
- 6. Why a Volumetric Curve?
- 7. Typical Natural Gas Typical Composition of Natural Gas Methane CH4 70-90% Ethane C2H6 0-20% Propane C3H8 Butane C4H10 Carbon Dioxide CO2 0-8% Oxygen O2 0-0.2% Nitrogen N2 0-5% Hydrogen sulfide H2S 0-5% Rare gases A, He, Ne, Xe trace
- 8. BTU of Various Gases Methane CH4 913 Ethane C2H6 1636 Propane C3H8 2361 Iso-Butane C4H10 3103 N-Butane C4H10 3123 Iso-Pentane C5H12 3902 N-Pentane C5H12 3947 Hexane C6H14 5581 Carbon Dioxide CO2 0 Oxygen O2 0 Nitrogen N2 0
- 9. Changing Composition Changes BTU Gas Symbol A B C D E Methane CH4 94.0% 95.0% 94.0% 94.0% 94.0% Ethane C2H6 4.0% 3.0% 3.0% 2.0% 3.0% Propane C3H8 .6% .6% .6% .6% .6% Iso-Butane C4H10 .1% .1% .1% .1% .1% N-Butane C4H10 .1% .1% .1% .1% .1% Iso-Pentane C5H12 .05% .05% .05% .05% .05% N-Pentane C5H12 .05% .05% .05% .05% .05% Hexane C6H14 .1% .1% .1% .1% 1.0% Carbon Dioxide CO2 0% 0% 0% 0% 0% Oxygen O2 0% 0% 0% 0% 0% Nitrogen N2 1.0% 1.0% 2.0% 3.0% 3.0% BTU (LHV) 952.41 945.24 936.08 919.76 980.56
- 10. The Sunday BBQ or LEL and UEL
- 11. Ignition Temperatures (F) Bituminous coal 572 Butane 788 Carbon 1292 Carbon monoxide 1128 Charcoal 660 Ethane 859 Gasoline 536 Iso-butane 864 Alcohol 750 Methane 1076 n-Butane 761 n-Heptane 419 n-Hexane 437 n-Pentane 500 Propane 842
- 12. UEL LEL Stoichiometric by Volume and Weight Air : Fuel Ratio by Volume Air : Fuel Ratio by Weight UEL 了 LEL UEL 了 LEL Methane CH4 5.64 9.52 18.97 10.20 17.22 34.30 Ethane C2H 6 3.76 8.89 16.15 6.80 16.08 29.20 Propane C3H 8 3.48 8.66 14.82 6.30 15.66 26.80 n-Butane C4H 10 2.99 8.54 14.27 5.40 15.45 25.80
- 13. Volumetric Air Fuel Ratio 1:1 Air : Fuel Ratio 2:1 3:1 4:1 5:1 6:1 7:1 8:1 9:1 10:1 11:1 12:1 13:1 14:1 15:1 16:1 17:1 18:1 19:1 20:1 21:1 22:1 23:1 24:1 25:1 26:1
- 14. Volumetric Parabolic Burning Curve LEL, UEL and Stoichiometry of Methane 1:1 Volumetric Air-Fuel Ratio UEL = 5.64:1 Stoichiometric = 9.52:1 LEL = 18.96:1 2:1 3:1 4:1 5:1 6:1 7:1 8:1 9:1 10:1 11:1 12:1 13:1 14:1 15:1 16:1 17:1 18:1 19:1 20:1 21:1 22:1 23:1 24:1 25:1 26:1
- 15. Volumetric Parabolic Burning Curve UEL, LEL and Stoichiometric for Ethane 1:1 Volumetric Air-Fuel Ratio UEL = 3.76:1 Stoichiometric = 8.89:1 LEL = 16.15:1 2:1 3:1 4:1 5:1 6:1 7:1 8:1 9:1 10:1 11:1 12:1 13:1 14:1 15:1 16:1 17:1 18:1 19:1 20:1 21:1 22:1 23:1 24:1 25:1 26:1
- 16. Volumetric Parabolic Burning Curve UEL, LEL and Stoichiometric for Propane 1:1 Volumetric Air-Fuel Ratio UEL = 3.48:1 Stoichiometric = 8.66:1 LEL = 14.82:1 2:1 3:1 4:1 5:1 6:1 7:1 8:1 9:1 10:1 11:1 12:1 13:1 14:1 15:1 16:1 17:1 18:1 19:1 20:1 21:1 22:1 23:1 24:1 25:1 26:1
- 17. Volumetric Parabolic Burning Curve UEL, LEL and Stoichiometric for n-Butane 1:1 Volumetric Air-Fuel Ratio UEL = 2.99:1 Stoichiometric = 8.54:1 LEL = 14.27:1 2:1 3:1 4:1 5:1 6:1 7:1 8:1 9:1 10:1 11:1 12:1 13:1 14:1 15:1 16:1 17:1 18:1 19:1 20:1 21:1 22:1 23:1 24:1 25:1 26:1
- 18. Volumetric Parabolic Burning Curve Rich Versus Lean 1:1 Volumetric Air-Fuel Ratio UEL = 5.64:1 Stoichiometric = 9.52:1 LEL = 18.96:1 2:1 3:1 4:1 5:1 6:1 7:1 8:1 9:1 10:1 11:1 12:1 13:1 14:1 15:1 16:1 17:1 18:1 19:1 20:1 21:1 22:1 23:1 24:1 25:1 26:1 LEAN SIDE of Stoichiometric RICH SIDE Of Stoichiometric
- 19. Volumetric Parabolic Burning Curve Richening the Mixture 1:1 Volumetric Air-Fuel Ratio UEL = 5.64:1 Stoichiometric = 9.52:1 LEL = 18.96:1 2:1 3:1 4:1 5:1 6:1 7:1 8:1 9:1 10:1 11:1 12:1 13:1 14:1 15:1 16:1 17:1 18:1 19:1 20:1 21:1 22:1 23:1 24:1 25:1 26:1 Richening the mixture
- 20. Volumetric Parabolic Burning Curve Leaning a Mixture 1:1 Volumetric Air-Fuel Ratio UEL = 5.64:1 Stoichiometric = 9.52:1 LEL = 18.96:1 2:1 3:1 4:1 5:1 6:1 7:1 8:1 9:1 10:1 11:1 12:1 13:1 14:1 15:1 16:1 17:1 18:1 19:1 20:1 21:1 22:1 23:1 24:1 25:1 26:1 Leaning the mixture
- 21. Fuel Volumetric Parabolic Burning Curve On the rich side of stoichiometric what remains after combustion is fuel 1:1 Volumetric Air-Fuel Ratio UEL = 5.64:1 Stoichiometric = 9.52:1 LEL = 18.96:1 2:1 3:1 4:1 5:1 6:1 7:1 8:1 9:1 10:1 11:1 12:1 13:1 14:1 15:1 16:1 17:1 18:1 19:1 20:1 21:1 22:1 23:1 24:1 25:1 26:1
- 22. O2 Volumetric Parabolic Burning Curve On the lean side of stoichiometric what remains after combustion is O2 1:1 Volumetric Air-Fuel Ratio UEL = 5.64:1 Stoichiometric = 9.52:1 LEL = 18.96:1 2:1 3:1 4:1 5:1 6:1 7:1 8:1 9:1 10:1 11:1 12:1 13:1 14:1 15:1 16:1 17:1 18:1 19:1 20:1 21:1 22:1 23:1 24:1 25:1 26:1
- 23. Volumetric Parabolic Burning Curve Rich Burn 4-Stroke Cycle Engines with or without NSCR 1:1 Volumetric Air-Fuel Ratio UEL = 5.64:1 Stoichiometric = 9.52:1 LEL = 18.96:1 2:1 3:1 4:1 5:1 6:1 7:1 8:1 9:1 10:1 11:1 12:1 13:1 14:1 15:1 16:1 17:1 18:1 19:1 20:1 21:1 22:1 23:1 24:1 25:1 26:1
- 24. Volumetric Parabolic Burning Curve Lean Burn 4-Stroke Cycle with or without Oxidation Catalyst and Standard 2-Stroke Cycle Engines 1:1 Volumetric Air-Fuel Ratio UEL = 5.64:1 Stoichiometric = 9.52:1 LEL = 18.96:1 2:1 3:1 4:1 5:1 6:1 7:1 8:1 9:1 10:1 11:1 12:1 13:1 14:1 15:1 16:1 17:1 18:1 19:1 20:1 21:1 22:1 23:1 24:1 25:1 26:1
- 25. Volumetric Parabolic Burning Curve Lean Burn/Clean Burn 4 and 2- Stroke Engines With Pre-Combustion Chambers 1:1 Volumetric Air-Fuel Ratio UEL = 5.64:1 Stoichiometric = 9.52:1 LEL = 18.96:1 2:1 3:1 4:1 5:1 6:1 7:1 8:1 9:1 10:1 11:1 12:1 13:1 14:1 15:1 16:1 17:1 18:1 19:1 20:1 21:1 22:1 23:1 24:1 25:1 26:1
- 26. Volumetric Parabolic Burning Curve Methane - 913 BTU (LHV) 1:1 Volumetric Air-Fuel Ratio UEL = 5.64:1 Stoichiometric = 9.52:1 LEL = 18.96:1 2:1 3:1 4:1 5:1 6:1 7:1 8:1 9:1 10:1 11:1 12:1 13:1 14:1 15:1 16:1 17:1 18:1 19:1 20:1 21:1 22:1 23:1 24:1 25:1 26:1 200 BTU 400 BTU 600 BTU 800 BTU 1000 BTU
- 27. Volumetric Parabolic Burning Curve Methane - 913 BTU (LHV) 1:1 Volumetric Air-Fuel Ratio UEL = 5.64:1 Stoichiometric = 9.52:1 LEL = 18.96:1 2:1 3:1 4:1 5:1 6:1 7:1 8:1 9:1 10:1 11:1 12:1 13:1 14:1 15:1 16:1 17:1 18:1 19:1 20:1 21:1 22:1 23:1 24:1 25:1 26:1 200 BTU 400 BTU 600 BTU 800 BTU 1000 BTU 913 BTU
- 28. Volumetric Parabolic Burning Curve Ethane - 1616 BTU (LHV) 1:1 Volumetric Air-Fuel Ratio UEL = 3.76:1 Stoichiometric = 8.89:1 LEL = 16.15:1 2:1 3:1 4:1 5:1 6:1 7:1 8:1 9:1 10:1 11:1 12:1 13:1 14:1 15:1 16:1 17:1 18:1 19:1 20:1 21:1 22:1 23:1 24:1 25:1 26:1 300 BTU 600 BTU 900 BTU 1200 BTU 1500 BTU 1800 BTU 1616 BTU
- 29. Volumetric Parabolic Burning Curve Propane (2335 BTU/LHV) 1:1 Volumetric Air-Fuel Ratio UEL = 3.48:1 Stoichiometric = 8.66:1 LEL = 14.82:1 2:1 3:1 4:1 5:1 6:1 7:1 8:1 9:1 10:1 11:1 12:1 13:1 14:1 15:1 16:1 17:1 18:1 19:1 20:1 21:1 22:1 23:1 24:1 25:1 26:1 400 BTU 800 BTU 1200 BTU 1600 BTU 2000 BTU 2400 BTU 2335 BTU
- 30. Volumetric Parabolic Burning Curve n-Butane - 3041 BTU (LHV) 1:1 Volumetric Air-Fuel Ratio UEL = 2.99:1 Stoichiometric = 8.54:1 LEL = 14.27:1 2:1 3:1 4:1 5:1 6:1 7:1 8:1 9:1 10:1 11:1 12:1 13:1 14:1 15:1 16:1 17:1 18:1 19:1 20:1 21:1 22:1 23:1 24:1 25:1 26:1 600 BTU 1200 BTU 1800 BTU 2400 BTU 3000 BTU 3600 BTU 3041 BTU
- 34. Peak Firing Pressure Highest pressure in a power cylinder due to combustion Peak Firing Pressure
- 35. Flame Front Velocity Peak Firing Pressure Peak Firing Pressure Peak Firing Pressure Peak Firing Pressure Ignition 10o BTDC 0o TDC 8o BTDC 6o BTDC 4o BTDC 2o BTDC 10o ATDC 8o ATDC 6o ATDC 4o ATDC 2o ATDC 20o ATDC 18o ATDC 16o ATDC 14o ATDC 12o ATDC 30o ATDC 28o ATDC 26o ATDC 24o ATDC 22o ATDC The faster the flame the earlier peak firing pressure occurs the earlier peak firing pressure occurs the higher the peak
- 36. Rich and Lean Misfires
- 38. The Parabolic Burning Curve and NOx and CO formation As combustion temperature increases NOx increases, as combustion temperature decreases CO increases.
- 42. Warning! I CANT TELL YOU WHERE YOURE GOING IF YOU DONT KNOW WHERE YOU ARE. Not knowing where a specific engine type runs on the curve causes arguments on the affects of rich and lean mixtures. Richening a lean mixture increases flame front velocity, peak firing pressure and NOx. Richening a rich mixture decreases flame front velocity, peak firing pressure and NOx.
- 43. What does the parabolic burning curve tell us? Upper explosion limit Lower explosion limit Stoichiometric Rich mixtures Lean mixtures Rich misfires Lean misfires Detonation Affects on flame front velocity Affects on peak firing pressure Affects emissions (NOx and CO) Where and why different engines run in different parts of the curve