A Stochastic Mixing Model for Predicting the Temperature Field in a Motored Engine

This paper is concerned with development of a Stochastic Mixing Model for determining the temperature variance field in a motored engine. The first step in this model is solution of the k and ϵ equations for the assumed isotropic turbulence from which turbulence velocities and the integral time scale(τ_T) are calculated. The charge in the engine at each moment in time is treated as N_p discrete particles of equal mass. Piston motion from one angle to the next is assumed instataneous and is frozen at each crankangle position for the time it takes to move from one angle to the next in reality. In the time that the piston motion is frozen, fluid particles move stochastically through distances corresponding to the calculated velocities in the time available in directions dictated by the components of velocity. During this motion, fluid particles may lose or gain heat through exchange with the wall or the mean flow. Fluid particle temperature increase due to isentropic compression is accounted for during the instataneous motion from one crankangle position to the next.

In a comparison of model predictions with experimental results from a motored engine, with an electrically heated exhaust valve, results show reasonable agreement.