IMPINGING JET ATOMIZATION AT ELEVATED AND SUPERCRITICAL AMBIENT TEMPERATURE AND PRESSURE CONDITIONS

A study of a spray formed by a pair of liquid nitrogen jets impinging on one another at elevated up to above-critical ambient temperature and pressure conditions has been conducted using double-pulse, two-reference-beam holography and high-speed photography. Qualitative observations as well as quantitative measurements on droplet size distribution and its dependence on pressure and temperature were obtained. Droplet size measurements showed that, at subcritical conditions, the increase of the ambient pressure initially makes the atomization quality deteriorate. Further increase in pressure (above 50% of the critical pressure) improves the atomization quality. The spray pattern changed drastically as the ambient pressure approached and exceeded the critical pressure in an environment already at supercritrical temperature. At supercritical ambient conditions, the usual mechanisms of droplet formation are no longer in place. The liquid nitrogen spray undergoes a mixing process with the nitrogen environment.