Superequilibrium O Concentrations and Prompt NO Formation in Laminar Premixed Methane-Air Flames

Narayan, S.; Rajan, S.

doi:10.1080/00102209808952085

Cited by 3 publications

(5 citation statements)

References 12 publications

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“…When this laminar turbulence model also generated plots of r.m.s. tursubroutine was used to simulate a steady, laminar, bulence intensity versus crank angle, which closely premixed flame, equation (7) gave results that agreed resembled [18] those based on experimental measwell with those published in the literature [10].…”

Section: Computation Of Flamefront No Emissions From Spark Ignition Enginesmentioning

confidence: 80%

“…), c(x) is the mean temperature profile HCN recycle route HCN $NCO, CN, NH$NO led through a turbulent premixed flame[23, 24], which to negligible prompt NO formation in a lean, preis given by a formula of Clavin and Williams [25] as mixed flame[10], a finding also confirmed byNishioka et al [28]. Glarborg et al[7] point out that…”

mentioning

confidence: 87%

“…at different locations in the laminar flame, using steady state and partial equilibrium relationships [10]. It is especially important to calculate accurately where á=1 Õ c(x), â= c(x) and ç =w /( w max I 3 ) and c the CH concentrations because the reaction CH is the non-dimensional temperature distribution in a +N 2 HCN+N initiates the formation of flamepremixed laminar flame, given in reference [23].…”

Section: Steady Flame Subroutinementioning

confidence: 99%

“…It is equally important to compute the O is the mass fraction of species i at a particular location atom concentration in the flamefront. The steady in an equivalent laminar premixed flame; it is easy state relationships given in reference [10] give results to obtain from any laminar premixed flame code. A for CH and O mass fraction profiles in laminar prelaminar flame subroutine, described later, was develmixed flames which are in agreement with those of oped as part of this work and also computes numeri-Correa and Smooke [8].…”

Section: Steady Flame Subroutinementioning

confidence: 99%

“…flame (mol/m 3 s) However, the simplified flamefront NO chemistry x distance through turbulent, used in the model does predict successfully the NO premixed flamefront (m) generated in steady premixed laminar flamefronts Y i (c) mass fraction of component i in [10], and the wrinkled laminar flame model of Bray laminar flame at c and Moss is an accepted method of computing Ȳ i (c) mass fraction of component i in species profiles in a turbulent premixed flame [23].…”

Section: Computation Of Flamefront No Emissions From Spark Ignition Enginesmentioning

confidence: 99%

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Computation of flamefront NO emissions from spark ignition engines

Narayan

Rajan

2001

International Journal of Engine Research

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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-

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Section: Computation Of Flamefront No Emissions From Spark Ignition Enginesmentioning

confidence: 80%

mentioning

confidence: 87%

Section: Steady Flame Subroutinementioning

confidence: 99%

Section: Steady Flame Subroutinementioning

confidence: 99%

Section: Computation Of Flamefront No Emissions From Spark Ignition Enginesmentioning

confidence: 99%

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Computation of flamefront NO emissions from spark ignition engines

Narayan

Rajan

2001

International Journal of Engine Research

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The reduced kinetic description of lean premixed combustion

Sánchez

Lepinette

Bollig

et al. 2000

Combustion and Flame

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Lean premixed methane-air flames are investigated in an effort to facilitate the numerical description of CO and NO emissions in LPP (lean premixed prevaporized) combustion systems. As an initial step, the detailed mechanism describing the fuel oxidation process is reduced to a four-step reduced description that employs CO, H 2 and OH as intermediates not following a steady-state approximation. It is seen that, under conditions typical of LPP combustion, the mechanism can be further simplified to give a two-step description, in which fuel is consumed and CO is produced according to the fast overall step CH 4 + f 0 2 -*• CO + 2H 2 0, while CO is slowly oxidized according to the overall step CO + |0a -*• CO2-Because of its associated fast rate, fuel consumption takes place in thin layers where CO, H2 and OH are all out of steady state, while CO oxidation occurs downstream in a distributed manner in a region where CO is the only intermediate not in steady state. In the proposed description, the rate of fuel consumption is assigned a heuristic Arrhenius dependence that adequately reproduces laminar burning velocities, whereas the rate of CO oxidation is extracted from the reduced chemistry analysis. Comparisons with results obtained with detailed chemistry indicate that the proposed kinetic description, not only reproduces well the structure of one-dimensionai flames, including profiles of CO, temperature and radicals, but can also be used to calculate NO emissions by appending an appropriate reduced chemistry description that includes both the thermal and the N 2 0 production paths. Although methane is employed in the present study as a model fuel, the universal structure of the resulting CO oxidation region, independent of the fuel considered, enables the proposed formulation to be readily extended to other hydrocarbons. INTRODUCTIONPollutant emissions have become one of the limiting factors when designing combustion chambers of gas turbine engines. In general, traditional design methodologies, largely based on empirical correlations, fail to provide reliable predictions of CO and NO emissions. With the ever increasing computer power, the numerical computation of the associated reacting flow fields has become a commonly used design tool. For the numerical results to be meaningful, the computations must incorporate adequate models for the turbulent flow field, as well as an accurate representation for the underlying chemistry. The chemistry descriptions currently utilized

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Turbulent Temperature Fluctuations in Spark Ignition Engines and Their Effect on NOx Emissions

Narayan¹,

Rajan²

2004

SAE Technical Paper Series

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Superequilibrium O Concentrations and Prompt NO Formation in Laminar Premixed Methane-Air Flames

Cited by 3 publications

References 12 publications

Computation of flamefront NO emissions from spark ignition engines

Computation of flamefront NO emissions from spark ignition engines

The reduced kinetic description of lean premixed combustion

Turbulent Temperature Fluctuations in Spark Ignition Engines and Their Effect on NOx Emissions

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