Despite of having high thermal efficiency and wide range of operation, compression ignition (CI) engines have high exhaust emissions of particulate matter (PM) and nitrogen oxides (NOx) which are harmful for the environment. In order to keep up with the latest stringent regulations on emissions, CI engines have been pushed to work with different fuels. In particular, the usage of gaseous fuels along with diesel fuel in dual fuel mode demonstrated to be a valid solution, especially for large bore applications. Indeed, a large part of the diesel liquid fuel is substituted with alternative gaseous fuels that is injected into the intake manifold to form a premixed charge with air, which significantly reduces PM and, in many cases, NOx. Even though, methane has been the mostly used gaseous fuel for dual fuel CI engine, the necessity to reduce CO2 emissions as well, has led hydrogen to be one of the most promising alternatives. Because of its faster burning velocity and wide range of air to fuel ratios, a different model for its combustion must be used for predictive purposes. In current work, a dual-fuel combustion model has been implemented in GT-Power with the aim of simulating and investigating the characteristics of hydrogendiesel combustion. Initially, a dual fuel model with methane was used and experimentally validated. A laminar flame speed model was built and incorporated in the software with the approaches of Heywood and Gülder studies. Design of experiments and design optimizer were used to find the optimal values of the combustion model parameters matching in-cylinder pressure curves. Once the model was validated with methane, the same methodology has been adapted to use hydrogen instead. Two new correlations are built and implemented in the code starting from literature experimental measurements. The simulated results of hydrogen-diesel combustion allow to foresee a burn rate consistent with methanediesel ones
R. De Robbio
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