Investigation of the combustion process of hydrogen jets under argon-circulated hydrogen-engine conditions

Abstract

The feasibility of argon-circulated hydrogen engines for use in vehicles was recently investigated. The substitution of the noble gas argon (Ar) as the working gas in a hydrogen engine led to the realization of a zero-emission, high-efficiency engine that allows low-ignitability hydrogen to ignite instantaneously after injection. The objective of this study was to investigate the combustion processes of hydrogen jets under argon-circulated hydrogen-engine conditions. Experiments were conducted in a constant-volume combustion vessel under varying conditions with respect to atmosphere, oxygen concentration, injection pressure, ambient temperature, and nozzle-hole diameter. Furthermore, the ignition characteristics and the combustion processes of the hydrogen jets were observed using high-speed shadowgraph images. Under short ignition delay conditions, the experimental results for the Ar–O2 atmosphere indicated a lower heat-release rate, which continued to the end of the injection and resulted in a longer combustion period, whereas the heat-release rate under the air (N2–O2) atmosphere terminated simultaneously with the end of the injection. The ignition delay for the hydrogen jet under an Ar–O2 atmosphere increased with decreasing ambient temperature, similar to the behaviour observed under the air atmosphere. Other fundamental characteristics that may help control the operation of argon-circulated hydrogen engines were obtained and discussed.