Modeling Hydrogen-Assisted Combustion of Liquid Fuels in Compression-Ignition Engines Using a Double-Wiebe Function

This article discusses the potential of using the double-Wiebe function to model combustion in a compression-ignition engine fueled by diesel fuel or its substitutes, such as hydrotreated vegetable oil (HVO) and rapeseed methyl ester (RME), and hydrogen injected into the engine intake manifold. The hydrogen amount ranged from 0 to 35% of the total energy content of the fuels burned. It was found that co-combustion of liquid fuel with hydrogen is characterized by two distinct combustion phases: premixed and diffusion combustion. The premixed phase, occurring just after ignition, is characterized by a rapid combustion rate, which increases with an increase in hydrogen injected. The novelty in this work is the modified formula for a double-Wiebe function and the proposed parameters of this function depending on the amount of hydrogen added for co-combustion with liquid fuel. To model this combustion process, the modified double-Wiebe function was proposed, which can model two phases with different combustion rates. For this purpose, a normalized HRR was calculated, and based on this curve, coefficients for the double-Wiebe function were proposed. Satisfactory consistency with the experiment was achieved at a level determined by the coefficient of determination (R-squared) of above 0.98. It was concluded that the presented double-Wiebe function can be used to model combustion in 0-D and 1-D models for fuels: RME and HVO with hydrogen addition.