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In general, combustion is a spatially three-dimensional, highly
complex physi co-chemical process oftransient nature. Models are
therefore needed that sim to such a degree that it becomes amenable
plify a given combustion problem to theoretical or numerical
analysis but that are not so restrictive as to distort the
underlying physics or chemistry. In particular, in view of
worldwide efforts to conserve energy and to control pollutant
formation, models of combustion chemistry are needed that are
sufficiently accurate to allow confident predic tions of flame
structures. Reduced kinetic mechanisms, which are the topic of the
present book, represent such combustion-chemistry models.
Historically combustion chemistry was first described as a global
one-step reaction in which fuel and oxidizer react to form a single
product. Even when detailed mechanisms ofelementary reactions
became available, empirical one step kinetic approximations were
needed in order to make problems amenable to theoretical analysis.
This situation began to change inthe early 1970s when computing
facilities became more powerful and more widely available, thereby
facilitating numerical analysis of relatively simple combustion
problems, typi cally steady one-dimensional flames, with moderately
detailed mechanisms of elementary reactions. However, even on the
fastest and most powerful com puters available today, numerical
simulations of, say, laminar, steady, three dimensional reacting
flows with reasonably detailed and hence realistic ki netic
mechanisms of elementary reactions are not possible."
This volume collects the results of a workshop held at Aachen,
West-Germany, Oct. 12 - Oct. 14, 1981. The purpose in bringing
together scientists actively working in the field of numerical
methods in flame propagation was two-fold: 1. To confront them with
recent results obtained by large ac- tivation-energy asymptotics
and to check these numerically. 2. To compare different numerical
codes and different trans- port models for flat flame calculations
with complex che- mistry. Two test problems were formulated by the
editors to meet these objectives. Test problem A was an unsteady
propagating flat flame with one-step chemistry and Lewis number
different from unity while test problem B was the steady,
stoichiometric hy- drogen-air flame with prescribed complex
chemistry. The parti- cipants were asked to solve one or both test
problems and to present recent work of their own choice at the
meeting. The results of the numerical calculations of test problem
A are challenging just as much for scientists employing numerical
me- thods as for those devoted to large activation-energy asympto-
tics: Satisfactory agreement between the five different groups were
obtained only for two out of six cases, those with Lewis number Le
equal to one. The very strong oscillations that oc- cur at Le = 2
and a nondimensional activation energy of 20 were accurately
resolved only by one group. This case is par- ticular interesting
because the asymptotic theory so far pre- dicts instability but not
oscillations.
The combustion of fossil fuels remains a key technology for the foreseeable future. It is therefore important to understand combustion mechanisms, in particular, the role of turbulence within this process. This monograph presents a thorough introduction to the field of turbulent combustion. After an overview of modeling approaches, Peters considers the three distinct cases of premixed, nonpremixed, and partially premixed combustion, respectively. By demonstrating the current theories of turbulent combustion within a cohesive presentation, this book makes a unified contribution to engineering and applied mathematics.
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