A new algorithm for the direct simulation of combustion systems and its application to reaction elimination

In this paper, a new explicit algorithm for the numerical solution of homogeneous gas-phase combustion systems is proposed, which is shown to outperform the solver SENKIN by more than two orders of magnitude for moderate accuracy and very large systems in the high temperature regime. Further speedup is achieved by identifying and removing irrelevant reactions from the mechanism whilst retaining all species. We show that in terms of computational efficiency this brings about another factor of at least 5 at an acceptable loss of precision. Due to its immediate relationship to stochastic direct simulation, our new (deterministic) algorithm can also be used as an easily applicable tool for the reaction flow analysis of mechanisms. Another characteristic of our method is that reactions in partial equilibrium are effectively removed from the mechanism, which can be regarded as an automatic separation of the fast from the slow timescales. The new algorithm and its usefulness for the elimination of reactions are investigated numerically for a mechanism that models the combustion of n-decane at constant pressure and contains 1218 species and 4825 reversible reactions. Further advantages of our method are its exceptional simplicity of implementation and negligible start-up costs, both of which can be attributed to the explicit nature of the algorithm.