Numerical simulation of the mixture distribution and its influence on the performance of a hydrogen direct injection engine under an ultra-lean mixture condition.

In this study, a three-dimensional numerical model of a hydrogen direct-injection engine was established, and the combustion model was verified by experimental data. The influence of the injection timing and nozzle diameter on ultra-lean combustion was evaluated. The results suggest that, with the delay in the injection timing, the mixture concentration near the spark plug and combustion speed gradually increase. The maximum thermal efficiency increased from 47.44% to 49.87%. The combustion duration and ignition lag are shortened from 19.15°CA to 11.15°CA to 16.13°CA and 5.92°CA, respectively. As the nozzle diameter increased, the injection duration was shortened, and the mixture distribution area became more concentrated. Furthermore, under ultra-lean combustion, the combustion rate is more sensitive to the distribution of the mixture. Appropriately increasing the equivalence ratio near the spark plug can significantly shorten the ignition lag and combustion duration and obtain a higher thermal efficiency. • The laminar flame speed model of hydrogen is calibrated by experimental results. • The G-equation is used to simulation the hydrogen combustion. • The in-cylinder mixture distribution, hydrogen jet and flow field were investigated. • The maximum indicated thermal efficiency reaches 50.05%. [ABSTRACT FROM AUTHOR]