Zero-Dimensional Modeling of Combustion and Heat Release Rate in DI Diesel Engines

Zero-dimensional heat release rate models have the advantage of being both easy to handle and computationally efficient. In addition, they are capable of predicting the effects of important engine parameters on the combustion process. In this study, a zero-dimensional combustion model based on physical and chemical sub-models for local processes like injection, spray formation, ignition and combustion is presented. In terms of injection simulation, the presented model accounts for a phenomenological nozzle flow model considering the nozzle passage inlet configuration and an approach for modeling the characteristics of the Diesel spray and consequently the mixing process. A formulation for modeling the effects of intake swirl flow pattern, squish flow and injection characteristics on the in-cylinder turbulent kinetic energy is presented and compared with the CFD simulation results. The applied combustion model accounts for the turbulence-controlled as well as the chemistry-controlled combustion. The effects of EGR on ignition delay and combustion are described as well. This model is validated using measurement data of different Diesel engines applying EGR and various injection strategies. The results of heat release rate and center of combustion are compared with measurement results over the entire engine map of a heavy-duty Direct Injection Diesel engine.