Experimental and numerical investigation on effects of pre-ignition positions on knock intensity of hydrogen fuel

The higher self-ignition temperature of hydrogen facilitates a higher compression ratio of H2ICEs (hydrogen internal combustion engines), which improves the thermal efficiency of engines. However, further increase of the compression ratio would unfortunately result in a super-knock, which would destroy engine parts severely. H2ICEs are vulnerable to occur pre-ignition, which is a main factor to cause a super-knock, but not always result in a super-knock. In this research, the pre-ignition position is considered as a significant factor to affect the knock intensity. To explore the relationship between the pre-ignition position and the formation of super-knock, a self-designed detonation bomb experiment was conducted. It's found that the super-knock would only occur in the situation that the pre-ignition occurs in one side of the chamber, whereas only mild knock would occur if the pre-ignition occurs in the center of the chamber. Based on numerical studies, it's found that the pre-ignition position would decide the shock wave distribution and the end-gas condition, which would further decide the onset of detonation as well as the super-knock. Therefore, avoiding the factors that may cause pre-ignition in one side of the chamber could help to avoid the super-knock and decrease the knock intensity.