  Using argon as the working fluid in an internal combustion engine holds the
potential of substantially enhancing thermal efficiency because of its high
specific heat ratio. Burning hydrogen, not with air but with pure oxygen, in a
closed-loop argon power cycle would lead to an emission-free exhaust
composition, effectively containing only water and argon, which can be
separated by condensation. One of the current challenges is the high-pressure
direct injection of both fuel and oxidizer, which directly controls the
combustion process. To support the development of such an injection strategy,
high-pressure injections of hydrogen in pressurized argon and nitrogen are
investigated using high-speed Schlieren and pressure transducers in a
non-heated constant-volume chamber at varying conditions. We show that hydrogen
mass flow is well described by choked flow theory, while jet penetration and
angle are determined by the pressure ratio between the fuel line and the
ambient. A correlation is presented between jet penetration and pressure ratio
for argon or nitrogen ambient at room temperature.
