Technical Report 17, c4e-Preprint Series, Cambridge
A New Method for the Automatic Elimination of Reactions from Large Mechanisms
ref: Technical Report 17, c4e-Preprint Series, Cambridge
Associated Theme: Numerics
In this paper a new explicit algorithm for the numerical solution of homogeneous gas-phase combustion systems is proposed, which is shown to outperform conventional solvers by more than two orders of magnitude for moderate accuracy and large systems. 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 five 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 is investigated numerically for a mechanism which 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. These properties suggest as typical application large operator-splitting problems requiring moderate accuracy, such as PDF transport models for example.
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