수소 및 메탄 분사의 출구 유동 조건 및 거시적 제트 특성 비교

초록

In the transportation sector, gaseous fuels such as natural gas and hydrogen are being considered as alternative fuels due to their potential to reduce carbon emissions. However, since natural gas is still not a carbon-free fuel, its transition to hydrogen has been considered to ultimately achieve net-zero emissions. Therefore, understanding the jet characteristics of natural gas and hydrogen is crucial to support this transition. This study aims to compare the exit flow conditions and the macroscopic jet characteristics of methane and hydrogen injected through a multi-hole injector. Compressible flow theories are used to characterize exit flow conditions, and the Z-type Schlieren imaging technique is used to visualize and analyze the macroscopic jet characteristics such as jet axial penetration and jet area. Two injection pressures (2 MPa and 4 MPa) are applied, and the ambient pressure is adjusted from 0.1 MPa to 2 MPa according to the injection pressure conditions. The results showed that the mass flow rate of methane was 2.76 times greater than hydrogen, primarily due to its higher density. Meanwhile, the momentum flux was 1.04 times slightly higher for hydrogen, attributed to the higher exit flow velocity of hydrogen. Hydrogen showed longer jet axial and radial penetration than methane by at least 2%, 7% each, and therefore, the jet area was also at least 10% wider in all applied injection conditions due to its higher momentum flux and mass diffusivity.

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