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.