Two-phase jet impingement for non-volatile residue removal

A high-speed jet impingement facility, which was developed for non-volatile residue removal from aerospace components in contact with liquid oxygen, h as been fabricated and tested. A two-phase mixture, consisting of water dro plets suspended in air, expands through a converging-diverging nozzle and t he resulting jet impacts the target surface at high speed. The advantage of this facility over conventional high-speed water jets is that the water co nsumed is extremely low, typically 1.67 x 10(-4)-16.7 x 10(-4) kg/s. Thus t he disposal of the waste water is greatly simplified. This work explores th e performance of the jet impingement facility over a range of operating con ditions using different nozzle configurations. The performance is character ized by the rate of residue removed, which is measured using a laser reflec tivity technique. It is demonstrated that the optimum rate of residue remov al is achieved when the air/liquid mixture temperature is as high as possib le without evaporating liquid and the water flowrate is as high as possible without water droplets agglomerating. Based on theoretical considerations in conjunction with the experimental results, it is demonstrated that the r esidue removal mechanism is due to emulsification upon liquid droplet impac t with the target surface. Potential applications for the jet impingement f acility reach far beyond the aerospace industry.