Research on the inducing factors and characteristics of knock combustion in a DI hydrogen internal combustion engine in the process of improving performance and thermal efficiency

Hydrogen energy is gaining greater attention because of the energy crisis and CO2 emissions, and knock combustion has become the main obstacle to improving thermal efficiency and power performance of hydrogen engines, which is an important method of hydrogen energy application. In this paper, the knock characteristic parameters and the factors affecting knock tendency of a 2.0 L DI hydrogen engine are investigated experimentally. The results reveal the variation in knock intensity is not linear with the retarding of SOI, which is related to the cylinder mixture distribution. Furthermore, methods such as increasing injection pressures can be useful in reducing the knock intensity. Equivalence ratio has a greater impact on knock compared with other parameters. The conclusions can be used in the further exploration of the knock combustion mechanism in DI hydrogen engines.