Computation of flamefront NO emissions from spark ignition engines

Abstract

Flamefront NO emissions from spark ignition The Fenimore mechanism [5] is yet another reacengines are estimated in this work using a two-zone thermo-tion pathway that leads to 'prompt' NO formation dynamic combustion model, an unsteady engine flame in a flamefront and also in post-flame gases of very model, the wrinkled laminar flame model of Bray and Moss, rich premixed flames [6]. In all premixed flames, O the k-å theory and simplified flamefront NO chemistry atom concentrations are much above chemical equiwhich has been verified in steady laminar premixed flames. librium levels, augmenting the rates within the The results show that as much as 230 ppm of flamefront NO flamefront of the Zeldovich and N 2 O reaction rates may be formed under stoichiometric engine operating con-[6]. Flamefront NO emissions, including Fenimore's ditions. The present approach is an alternative to the empiriprompt NO, from steady laminar methane/air cal correlations used to compute engine flamefront NO flames have been successfully predicted by a number which are based on highly extrapolated data. of workers [6-9], because of exponential increases in computing capabilities and more accurate chemical Key words: flamefront NO emissions, prompt NO, kinetic data. The flamefront NO mechanism in prespark ignition engine, methane fuel, two-zone engine mixed flames is very complex [6], but has recently combustion model been simplified by a number of workers [9, 10]. It is difficult to predict flamefront NO emissions from turbulent flames because turbulent flame codes cannot incorporate more than a few chemical reac-

Modelling cycle to cycle variations in an SI engine with detailed chemical kinetics

“…Increasingly stringent restrictions on vehicle emissions have led to much research into reducing these emissions. Spark ignition (SI) engine NO x emissions have been studied both experimentally [1] and with models of varying complexity [2][3][4][5]. The high temperatures reached in SI engines cause the conversion of atmospheric nitrogen to nitric oxide (NO).…”