Experimental and Numerical Momentum Flux Analysis of Jets from a Hydrogen Injector

The use of hydrogen in internal combustion engines is an effective approach to significantly support the reduction of CO₂ emissions from the transportation sector using technically affordable solutions. The use of direct injection is the most promising approach to fully exploit hydrogen potential as a clean fuel, while preserving targets in terms of power density and emissions. In this frame, the development of an effective combustion system largely relies on the hydrogen-air mixture formation process, so to adequately control the charge stratification to mitigate pre-ignitions and knock and to minimize NOx formation. Hence, improving capabilities of designing a correct gas jet-air interaction is of paramount importance. In this paper the analysis of the evolution of a high-pressure gas jet produced by a single-hole prototype injector operated with different pressure ratios is presented. The experimental analysis is carried out using global momentum flux measurement with the support of Schlieren imaging and needle lift detection. A combined CFD analysis of the injection process is used to investigate the details of the momentum flux device operation, offering an interesting insight in the measurement mechanisms and in the jet evolution. The final goal of the combined experimental-numerical approach is to provide quantitative description of the injection process dynamics and spatial/temporal jet evolution and morphology so to support the combustion system design.