A complete 0D thermodynamic predictive model for direct injection diesel engines

Ideal models provide the simplest way to reproduce internal combustion engine (ICE) cycles, but they usually do not represent with sufficient accuracy the actual behaviour of an ICE. A suitable alternative for research and development applications is provided by zero-dimensional (0D) thermodynamic models. Such models are very useful for predicting the instantaneous pressure and temperature in the combustion chamber, which in turn allows the prediction of engine operation characteristics. However, they use simplifying hypotheses which lead, in some cases, to a lack of accuracy or a limited predictive capability.This paper describes a 0D single-zone thermodynamic model that takes into account the heat transfer to the chamber walls, the blow-by leakage, the fuel injection and engine deformations, along with the instantaneous change in gas properties. Special attention has been paid to the description of the specific sub-models that have been used for the calculation of the energy and mass equations terms. The procedures followed for the estimation of some mechanical and heat transfer parameters and the combustion model fitting are also detailed. After the fitting, the model was validated in different operation points in a 4-cylinder 2-l DI diesel engine, showing a good capability for accurate predictions of engine performance and the gas state in the closed cycle.

► A model to predict pressure evolution in a diesel engine has been proposed.
► Specific sub-models for heat transfer, heat release, blow-by, fuel injection, deformations and gas properties are considered.
► Model fitting and validation carried out with a complete experimental matrix in a 2-l engine.
► Good agreement between experimental and simulated pressure traces was found.
► The effect of sub-model in the final results has been analysed.