Theoretical study of the effect of hydrogen addition to natural gas-fueled direct-injection engines

The preparation of air–fuel mixture is considerably dependent on fluid flow dynamics to achieve improved performance, efficiency, and engine combustion in the appearance of flow. In this study, the effects of mixtures of hydrogen and compressed natural gas (CNG) on a spark ignition engine are numerically considered. This article presents the results of a direct-injection engine using methane–hydrogen mixtures containing H2 between 0% and 15% by volume. The result shows that the percentage of hydrogen in the CNG increases the burning velocity of CNG and reduces the optimal ignition timing to obtain the maximum peak pressure of an engine running with a blend of hydrogen and CNG. With hydrogen addition to natural gas, the peak heat release rates increase. For 15% hydrogen, the maximum values at crank angles (CAs) for in-cylinder temperature and heat release rate are achieved at 8° CA, and the maximum temperature is approximately 150 K. Port injection gasoline is converted into direct injection by CNG fuel in this engine.