Determination of underexpanded hydrogen jet flame length with a complex nozzle geometry

Abstract

With the growing number of hydrogen-powered cars and hydrogen filling stations, it is essential to have accurate and reliable engineering models for this infrastructure. The length of a hydrogen jet flame resulting from a high pressure release will have an impact on its consequences. This work examined the effect that nozzle geometry has on hydrogen jet flame length. The geometry was modified by varying the diameter of the spouting nozzle downstream from the choked nozzle upstream. These experimental results were compared with an existing model for estimating jet flame length. Sensors upstream from the complex nozzle geometry measured the temperature, mass flow rate, and pressure for the released hydrogen. A high-speed camera recorded the hydrogen jet flame at a stable pressure and mass flow. Flame lengths were determined with an image processing tool used to analyze the high-speed video for each experiment. By analyzing the dataset with the image processing tool, the jet flame length distribution, minimum and maximum jet flame length, and the jet flame length standard deviation could be computed. Results showed that the nozzle geometry can increase the jet flame length by 62% compared to a single nozzle configuration with equal mass flow rate. With the upstream nozzle as input, the smallest average relative deviation from previously published models was 13%. The discharge coefficients for different nozzles were calculated and presented.