Modelling and Simulation of Wankel Engine Flow Fields 900029
The meaningfulness of numerical studies on Wankel engine flow fields depends strongly on turbulence modelling and the numerical methods used to obtain solutions. This investigation examined two different turbulence models and several variations of a numerical method for calculating turbulent flow fields inside one of the combustion chambers of a motored, two-dimensional Wankel engine. The two turbulence models examined were the standard k-ε model with wall functions and the low Reynolds number k-ε model of Chen and Patel. The numerical method used in this investigation was the approximate-factorization method of the ADI type with upwind differencing of the convection terms based on flux-vector splitting. Four variations of this method were investigated and they are first-order upwind differencing, second-order upwind differencing, first-order upwind differencing with Newton-Raphson iteration at each time step, and second-order upwind differencing with Newton-Raphson iteration at each time step. Iteration was used to minimize numerical errors arising from approximate-factorization and time-linearization. Results are presented which show the predicted velocity vector fields, contours of the turbulent kinetic energy and its dissipation rate, and average pressure and temperature of the gas within one combustion chamber of a motored, two-dimensional Wankel engine.