Open air sprays of transcritical and supercritical Jet-A fuel into ambient conditions

Fuel injected as a supercritical fluid or into conditions exceeding the critical point has demonstrated mixing unlike classical atomization. Through a transition from turbulent breakup to diffusion-driven, dense fluid mixing, diesel combustion may be improved through more complete and efficient fuel/air mixing. As compression ignition conditions tend to exceed the critical point of the fuel injected, transitioning the fuel to a supercritical fluid prior to injection and maintaining it as such through the whole injection event is a viable prospect. To explore the effects of the transition across the critical point on fuel/air mixing and spray morphology, high-pressure, high-temperature Jet-A1 is injected into room temperature and pressure conditions. Diffuse backlit imaging, Mie scattering, schlieren imaging, and long-distance microscopy are used to observe and quantify the spray morphology. Differences in spray morphology are observed across the critical transition region of Jet-A1. Spray cone angle, spray tip penetration, spray tip velocity, and vapor-to-liquid ratio are quantified, with a significantly higher vapor percentage observed in supercritical cases. A new power-law model for spray tip penetration development in the near-nozzle regime with a temperature dependence is presented and compared to previous models and experimental data, and found to be a good fit for the data.