Modeling and Simulation of a Dual Fuel (Diesel/Natural Gas) Engine With Multidimensional CFD

Abstract

A dual fuel engine simulation model was formulated and the combustion process of a diesel/natural gas dual fuel engine was studied using an updated KIVA-3V Computational Fluid Dynamic (CFD) code. The dual fuel engine ignition and combustion process is complicated since it includes diesel injection, atomization and ignition, superimposed with premixed natural gas combustion. However, understanding of the combustion process is critical for engine performance optimization. Starting from a previously validated Characteristic-Timescale diesel combustion model, a natural gas combustion model was implemented and added to simulate the ignition and combustion process in a dual fuel bus engine. Available engine test data were used for validation of both the diesel-only and the premixed spark-ignition operation regimes. A new formulation of the Characteristic-Timescale combustion model was then introduced to allow smooth transition between the combustion regimes. The models were applied to suggest methods for further engine improvement for better emission performance. The model was extended to consider the direct injection natural gas case by modeling gas jet injection. A comparison of the combustion and emission of the two different gas supply methods was conducted. The research demonstrated that multidimensional modeling is useful for dual fuel engine study and optimization.