Assessment of the Approximation Formula for the Calculation of Methane/Air Laminar Burning Velocities Used in Engine Combustion Models

Especially for internal combustion engine simulations, various combustion models rely on the laminar burning velocity. With respect to computational time needed for CFD, the calculation of laminar burning velocities using a detailed chemical mechanism can be replaced by incorporation of approximation formulas, based on rate-ratio asymptotics. This study revisits an existing analytical approximation formula [1]. It investigates applicable temperature, pressure, and equivalence ratio ranges with special focus on engine combustion conditions. The fuel chosen here is methane and mixtures are composed of methane and air. The model performance to calculate the laminar burning velocity are compared with calculated laminar burning velocities using existing state of the art detailed chemical mechanisms, the GRI Mech 3.0 [2], the ITV RWTH [3], and the Aramco mechanism [4]. The Aramco mechanism was chosen for further investigations, because it predicts very well new experimental data for ambient conditions presented in this work. Significant differences are observed between laminar burning velocities calculated with the original set of coefficients presented by Goettgens et al. [1] for the approximation formula and the Aramco mechanism. Hence, updated parameters for the approximation formulation are presented. The impact of the laminar burning velocity results on the combustion models is discussed.