Integrated CFD-Experimental Methodology for the Study of a Dual Fuel Heavy Duty Diesel Engine

This paper deals with the experimental and numerical investigation of a 2.0 litre single cylinder Heavy Duty Diesel Engine fuelled by natural gas and diesel oil in Dual Fuel mode. Due to the gaseous nature of the main fuel and to the high compression ratio of the diesel engine, reduced emissions can be obtained. An experimental study has been carried out at three different load level (25%, 50% and 75% of full engine load). Basing on experimental data, the authors recreated a 45° mesh sector of the engine cylinder and performed CFD simulations for the cases at 50% and 75% load levels. Numerical simulations were carried out on the 3D code Ansys FORTE. The aim of this work is to study combustion phenomena and, in particular, the interaction between natural gas and diesel oil, respectively represented by methane and n-dodecane. A reduced kinetic scheme for methane auto-ignition was implemented while for n-dodecane two set of reactions were utilised. The first one consisting of a one-step mechanism is compared with the far more detailed second one including 100 species and 432 reactions. The validation of the model is provided in terms of pressure, temperature, heat release rate and emissions. Results show that the reduced mechanism allows a correct prediction of the methane burning rate while the more detailed one provides a reliable description of CO formation.