Pollutant formation modelling in natural gas SI engines using a level set based flamelet model

Abstract

The level set flamelet model for turbulent premixed combustion was recently extended to improve the modelling of the spark ignition process, to incorporate the influence of unsteady flame kernel development on turbulent flame propagation, to embrace flame—wall interaction, and to comprise pollutant prediction models. The formation of nitrogen oxides (NO _x ) is predicted using the extended Zeldovich mechanism. The concentrations of the involved intermediate species are determined using a chemical equilibrium assumption. The formation of engine-out unburnt hydrocarbons (UHCs) and carbon monoxides (COs) is directly linked to incomplete combustion due to flame quenching at the time the flame hits the wall.

In this paper, the new model is used for the analysis of combustion in a homogeneous charged natural gas SI engine operating on lean conditions. The investigated engine operating (PAM) points differ in the applied equivalence ratio, ignition timing, and rate of exhaust gas recirculation. The influence of the load on the peak pressures, peak pressure locations, and pollutant formations is discussed in detail. A good agreement with experimental data was obtained among all engine operating points.

Keywords

engine pollutant modelling premixed combustion

Get full access to this article

View all access options for this article.

References

Peters

Turbulent combustion, 2000 (Cambridge University Press).

Ewald

A level set based flamelet model for the prediction of combustion in homogeneous charge and direct injection spark ignition engines. PhD Thesis, RWTH-Aachen, 2006.

Ewald

Peters

On unsteady premixed turbulent burning velocity prediction in internal combustion engines. In Proceedings of the Combustion Institute, 2006, pp. 3051–3058. DOI:10.1016/j.proci.2006.07.119.

Herrmann

Numerical simulation of turbulent Bunsen flames with a level set flamelet model. Combust. Flame, April 2006, 145, 357–375.

Herrmann

Numerical simulation of premixed turbulent combustion based on a level set flamelet model. PhD Thesis, RWTH Aachen, 2001.

Tan

Reitz

R. D.

An ignition and combustion model based on the level-set method for spark ignition engine multidimensional modeling

Combust. Flame, 2006, 145, 1–15.

Peters

The turbulent burning velocity for large-scale and small-scale turbulence

J. Fluid Mech., 1999, 384, 107–132.

Sethian

J. A.

Level set methods and fast marching methods, 1996, 1999 (Cambridge University Press).

Tennekes

Lumley

J. L.

A first course in turbulence, 1972 (MIT Press, Cambridge, MA).

10.

Abdel-Gayed

Bradley

Flame propagation along flat plate turbulent boundary layers. Phil. Trans. R. Soc. Lond., A 301, 1981, 1457, 1–25.

11.

Damköhler

Zeitschr

Elektrochemie

Ang. Phys. Chem., 1940, 46(11), 601–626.

12.

Peters

A spectral closure for premixed turbulent combustion in the flamelet regime

J. Fluid Mech., 1992, 242, 611–629.

13.

Launder

B. E.

Spalding

D. B.

Computer Methods in Applied Mechanics and Engineering, 1974, 3, 269–89.

14.

Seshadri

Peters

The inner structure of methane-air flames

Combust. Flame, 1990, 81, 96–118.

15.

Müller

U. C.

Bollig

Peters

Approximation for burning velocities and Markstein numbers for lean hydrocarbon and methanol flames

Combust. Flame, 1997, 108, 349–356.

16.

Peters

Williams

F. A.

The asymptotic structure of stoichiometric methane–air flames

Combust. Flame, 1987, 68, 185–209.

17.

Zeldovich

Y. B.

The oxidation of nitrogen in combustion and explosions. Acta Physiochim., USSR 21, 1946, 577.

18.

Damköhler

Der Einfluss der Turbulenz auf die Flam-mengeschwindigkeit in Gasgemischen

Z. Elektrochem, 1940, 46, 601–652.

19.

Fenimore

C. P.

Studies of fuel-nitrogen in rich flame gases. In Proceedings of the 17th Symposium (International) on Combustion, The Combustion Institute, Pittsburgh, 1979, pp. 661–670.

20.

Barths

Simulation of diesel engine and gas turbine combustion using multiple flamelets with detailed chemistry. PhD Thesis, RWTH Aachen, 2000.

21.

Peters

Technische Verbrennung (RWTH Aachen), 2006.

22.

Bollig

Berechnung laminarer Kohlenwasserstoffflammen im Hinblick auf die Stickoxidbildung in Verbrennungsmotoren. PhD Thesis, RWTH Aachen, 1998.