Experimental and Numerical Investigations of the Effect of Charge Motion on Abnormal Combustion in a Heavy-Duty H2 DI ICE

In modern hydrogen engines, abnormal combustion phenomena such as knock and pre-ignition limit the operational range. To overcome these limitations, the balance of required and supplied ignition energy needs to be understood. Charge motion is one way to increase the robustness against abnormal combustion in conventional spark-ignition engines. Hence, test bench measurements with three different cylinder heads on a 2.13 L research single-cylinder engine are presented and analyzed, focusing on high loads up to IMEP = 32 bars. These cylinder heads are derived from a commercial heavy-duty diesel engine and feature different intake port designs, ranging from a filling to a tumble port design. 3D-CFD simulations enable deeper insight into charge motion, homogenization, turbulence intensity and temperature distribution and are used to understand the influence of different port and spray-forming cap designs on mixture formation and combustion characteristics. The results show that, depending on injection configuration, increased charge motion can decrease or increase NOx emissions significantly but increases abnormal combustion tendency in all configurations by heating up the cylinder charge. This shows that significantly increased charge motion is not necessarily required for retrofitted heavy-duty hydrogen engines to reach diesel-like performance.