Computations of gas exchange, heat release and transfer processes in engine fuelled with diesel or CNG

Abstract

The paper focuses on the conversion of a Diesel engine to CNG, with emphasis on the use within Australia where the refueling network is scarce, and the developments needed in the injection and combustion systems to further improve the fuel conversion efficiency and reduce the in-cylinder pollutant formation. For dual fuel CNG-Diesel operation, the best option is the adoption of two independent fuel injectors for the Diesel and the CNG, while for the single fuel CNG operation, the best option is the adoption of one direct CNG injector plus a jet ignition device accommodating a second CNG injector and a glow plug. With both designs, the CNG engine would operate following different modes of combustion, not only the traditional Diesel like, but also the traditional gasoline-like, a mixed gasoline/Diesel-like and finally HCCI-like depending on the injection strategy adopted for the two injectors of each cylinder. Computations of gas exchange, heat release and heat transfer processes are computed with an engineering performance simulation code with the model for the Diesel fuel validated versus extensive experimental data.