Eualuation of a Turbulent Combustion Model for Internal Combustion Engine Applications

Multidimensional numerical models of internal combustion engine processes require closure approximations for the effective turbulent reaction rates for the reactive mixture. In the present paper, an engineering level approach, called the “Eddy-Burn-Rate” model, is proposed which attempts to reconcile the multiscale effects of turbulence on flame propagation. Two rate limiting steps are considered: an entrainment or mixing step and a burn or microscale reaction step. The model treats mixing via a two-equation second order closure turbulence model (k,w) and defines a time constant for the fuel oxidation reaction based on laminar flame consumption on the Taylor micro-scale. The Eddy-Burn Rate model is evaluated against alternative turbulent reaction rate closure methods as well as data from two different combustion bombs. Model simulations are compared to combustion bomb data for cylindrical flame evolution in a highly swirling flowfield and in a stagnant but highly turbulent flow. The results indicate that under conditions relevant to IC engine operation the model provides a relatively good representation of the fully developed flame evolution.