Exit flow conditions and macroscopic jet characteristics of hydrogen and methane injected from a multi-hole injector

초록

The transition from natural gas to hydrogen has been pursued to achieve net-zero emissions in internal combustion engines. When natural gas is substituted with hydrogen, the emerging flow conditions and jet characteristics would vary, which need to be thoroughly investigated to calibrate engine parameters for optimal combustion. This study compares the exit flow conditions and macroscopic jet characteristics of methane and hydrogen injected from a multi-hole injector. Three injection pressures from 2 MPa to 4 MPa are applied, and the ambient pressures are adjusted from 0.1 MPa to 1 MPa, where the flows are in choked flow conditions. First, the exit flow conditions are characterized using compressible flow theories. The mass flow rate of methane was 2.76 times greater than hydrogen, but the momentum flux was 1.04 times higher for hydrogen, attributed to the higher exit flow velocity of hydrogen. Second, the macroscopic jet characteristics of both fuels are compared using Z-type Schlieren imaging. Hydrogen showed greater penetration and a larger jet width than methane under all conditions. However, the difference in jet penetration diminished at higher injection and ambient pressures. Overall, hydrogen exhibited more spreading characteristics in axial and radial directions compared to methane.

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