Experimental study on the combustion and emission performance of the hydrogen direct injection engine

The influence of excess air coefficient, ignition timing, and injection timing were investigated to examine the combustion and emission performance of a hydrogen engine operating at low speed with low loads. Comprehensive experimental research was then undertaken to evaluate the engine performance across a wide range of loads and various combinations of factors. The experimental results show a substantial improvement in brake thermal efficiency (BTE) and a noteworthy reduction in NOX emissions with an increased excess air coefficient. Although the impact of injection timing on BTE is negligible, an appropriate injection timing delay effectively reduces NOX emissions. A lean mixture and a suitable ignition timing delay exhibit high thermal efficiency at a lower engine speed and simultaneously suppress knock. The BTE reaches 33.46% at a mean effective pressure of 10.0 bar. Improving the turbocharging capability under low-speed and high-load conditions is essential for enhancing the performance of hydrogen engines.