LES Study of the Mixing Process and Cyclic Variation of a
Direct-Injection Hydrogen Engine 2023-01-7025
Hydrogen internal combustion engine is considered to be one of the promising ways
to achieve zero-carbon emissions in the automotive industry. However, the
problem of high NOx emissions from hydrogen engines needs to be
addressed. Although homogeneous lean-mixture combustion could reduce engine-out
NOx emissions, it is necessary to ensure mixing homogeneity to
avoid excessive NOx formation from the rich mixture packets. In this
study, large-eddy simulations (LES) of a direct-injection hydrogen engine were
carried out to assess the hydrogen-air mixing process in forming homogeneous
charges with consideration of cyclic variations. The high-speed hydrogen jet
flow was modeled in a constant-volume vessel first to verify the LES model.
Engine simulations were then performed to study the effects of the injector
location (side vs. central), injection pressure, and injector type (pintle vs.
outward opening) on the mixing process, mixture homogeneity, and cyclic
variations. The results show that the mixture homogeneity and its cyclic
variations are influenced by these parameters, and the centrally located pintle
injector with an injection pressure of 10 MPa can produce the best mixture
homogeneity and minimal cyclic variations among the cases
studied.