Thermo-Fluid Dynamic Simulation of a S.I. Single-Cylinder H₂ Engine and Comparison With Experimental Data

This paper deals with the modelling and experimental work carried out on a BMW single cylinder spark ignition hydrogen engine. The authors have enhanced a 1D thermo-fluid dynamic simulation code in order to cope with the different chemical and physical aspects due to the fuelling of a spark ignition engine with hydrogen rather than with conventional gasoline. In particular the combustion module, which is based on a quasi-dimensional approach, has been extended by introducing the possibility of predicting the burning rate of the combustion of a homogeneous mixture of hydrogen and air. A fractal approach was followed for the turbulent flame speed evaluation, while an extend database for laminar burning velocities was created applying a kinetic simulation code for one-dimensional laminar flames. The modelling of the whole intake and exhaust systems coupled to the engine has been addressed, considering port-injection fuel system, in which hydrogen has been injected at very low temperature (cryogenic conditions). The fundamental 1D fluid-dynamic equations are solved by means of second order finite difference schemes; the working fluid is considered as a mixture of ideal gases, with specific heats depending on the gas temperature and the mole fractions of species, whose correlations for each specie (including para-hydrogen) have been extended in the region of low temperature. A first validation of the enhanced model is shown in the paper, comparing the computed results with the experimental data of in-cylinder pressures, intake and exhaust instantaneous pressure histories at different locations and NO emissions discharged by the cylinder.