Phenomenological Multi-Step Modeling of Diesel Injection and Combustion

A previously developed injection system model has been enhanced including a quasi-dimensional, multi-zone, direct injection (DI) diesel combustion model, with the aim of taking into account the actual injection process, the spray formation and the droplet heating-vaporization processes. Such a goal is obtained by means of the integration of different modeling approaches. In a commercial simulation environment, a lumped parameter mechanical-hydraulic scheme is used to model the injection process, in terms of fuel flow rate and injection pressure. The spray formation processes and the droplet vaporization phenomena are then implemented in a self developed computation code, accounting for finite thermal conductibility of the liquid phase fuel. The coupling among the models allows for a detailed representation of the involved phenomena at each simulation step (e.g. fuel time pressure history, fuel properties, atomization, evaporation ambient condition); at the same time, it is possible to evaluate the operation of the injection system on the basis of atomization, vaporization and combustion behavior. The results of the numerical prediction are compared to experimental data referred to a DI diesel engine.