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Turbulent combustion process in diesel engine

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  1. Turbulent combustion process in diesel engine http://www.made-in-china.com/image/2f0j00OCcTrbPlgDoGM/R6105C-Marine-Diesel-Engine.jpg MVK 135: Turbulent Combustion Lund Institute of technology Xue-Song BAI Henrik Gummesson Fanny David JihyeHwang Guillaume Becquin

  2. subject M is working with a big diesel engine that has open combustion chambers, direct injection and operates at 310 rpm. The engine has 26-cm bores and a 73-cm stroke, and compression ratio 16.5. M wants to know more details about how the engine works.

  3. Introduction • Configurations of diesel engines and the flow field • Typicalfuels for diesel enginecombustion • Features of turbulent combustion process in diesel engines • Phenomenologicalanalysis of the combustion process in diesel engines

  4. I. Configurations of diesel engines and flow field • Mean piston speed: • Stroke = 0.73 m • Bore = 0.26 m • n=310 rpm • N=310/60 • L = S = 0.73 m Sp = 2*L*N Sp= 7.543 m/s

  5. I. Configurations of diesel engines and flow field • Turbulent motions in cylinder: • Swirl • Tumble • Squish • Turbulence intensity and swirl

  6. I. Configurations of diesel engines and flow field • Intake valve configuration and swirl a,c,d: centeredintake valve b: non centeredintake valve

  7. I. Configurations of diesel engines and flow field • Intake valve design and swirl

  8. I. Configurations of diesel engines and flow field • Cylinderhead configuration and swirl « May Fireball »

  9. II. Typical fuel for diesel engine combustion • Auto-ignition time: • Factorsaffecting the auto ignition time: • Temperature (τ ∞ 1/T) and pressure • Compression ratio (τ ↓ whenrc ↑) • Injection timing • Concentration of oxygen • Fuel composition: • Cetanenumber : ↑ CN →↓ Ignition delay time

  10. II. Typical fuel for diesel engine combustion • Auto-ignition time: From The Internal Combustion Engine Fundamentals, by John B.Heywood • is the mean piston speed ( ) • is the temperature in the combustion chamber : • is the pressure in the combustion chamber: • isdefined as:

  11. II. Typical fuel for diesel engine combustion • Fuels in diesel engine: • Common diesel fuel: C10H20to C15H28 • Most used: C12H23 • Mean characteristics:

  12. III. Features of turbulent combustion process in diesel engines • Different stages: • Injection of fuel • Auto-ignition • Premixedflame propagation • Diffusion flame structure • Diffusion flame propagation after the end of fuel injection

  13. III. Features of turbulent combustion process in diesel engines • Injection of fuel • High speed injection ≈ 150m/s • Fuel sprayed in small drops • Vaporization of the fuel due to temperature and pressure conditions • Mixing of the fuel and air beforeauto-ignition: • Large eddies in air flow: depends on bore diameter • Large eddies in fuel flow: depends on the nozzlediameter • Mixing time ≈ large eddy time

  14. III. Features of turbulent combustion process in diesel engines • Auto ignition • Piston raises up = Temperature Pressure Auto ignition of the premixed air/fuel mixture (propagation of the premixedflamethrough the rich and lean mixture)

  15. III. Features of turbulent combustion process in diesel engines • Diffusion flame structure • The premixedflamereach the fuel jet = non- premixedflameappears • Stabilizationaroundstoichiometric mixture fraction • Stabilizationat the lift off distance from the injection nozzle • Mixing time >>> reaction time Burke-Schumann structure

  16. III. Features of turbulent combustion process in diesel engines • Diffusion flame propagation after the fuel injection: The flamefollows the instantaneous line where Z=Zst • Quenching of the diffusion flame: • Fuel concentration • Lean fuel reaction • Temperature • Quenching

  17. III. Features of turbulent combustion process in diesel engines • Effect of engine speed and turbulence: Engine speed Turbulence level Auto ignition time Diffusion Flamelenght Duration of combustion

  18. IV. Phenomenologicalanalysis of the combustion process in diesel engines • Air-flow: • Integral scale: • Kolmogorovscale:

  19. IV. Phenomenologicalanalysis of the combustion process in diesel engines • Flamescales: • Ka and Da:

  20. IV. Phenomenologicalanalysis of the combustion process in diesel engines • Fuel flow: Same constants than in air flow • Integral scale: • Kolmogorov scale:

  21. IV. Phenomenologicalanalysis of the combustion process in diesel engines • Flame scales: • Ka and Da:

  22. IV. Phenomenologicalanalysis of the combustion process in diesel engines • The structure of the flame in diesel engine

  23. OH radical distribution • Turbulent non-premixed flame • Thin zone -> Thicker zone • OH zone becomes wrinkled • Flame broadening by turbulence

  24. IV. Phenomenological analysis of the combustion process in diesel engines • Regime of the combustion process • A-B: Ignition delay • B-C: Premixed or rapid combustion phase • C-D: Mixing-controlled combustion phase • D-E: Late combustion phase

  25. IV. Phenomenological analysis of the combustion process in diesel engines • Factorscontrolling the flametemperature and emissions: • Emissions: Nox, CO, unburnedhydrocarbon,soot • High peaktemperaturerapid NO formation • Injection timing • Wall quenching • Fuel bubblefalling • For reducingemissions: • Temperaturereduction • Low-Noxburner • Oxy/Gas combustion • Reburn

  26. IV. Phenomenologicalanalysis of the combustion process in diesel engines • Fuel injection velocity: • Flamelenght:

  27. IV. Phenomenologicalanalysis of the combustion process in diesel engines • Fuel injection timing changes ignition delay time • Retarded fuel injection reducesNoxemission • Controlling injection rate: Injectorarea pressure fuel/air mixing rate heat release rate • CO emission: Fuel/air equivalence ratio

  28. Conclusion • Applied project: • Using the theories seen in lecture • Formulas application • Working in team • Dealing with short deadline • Overcome difficulties (which hypothesis; how to find fuels features….) Dealing with real engineering problem