A high speed jet impingement facility, which is used for nonvolatile residue removal from aerospace components in contact with liquid oxygen, has been fabricated and tested. A two-phase jet, consisting of water droplets suspended in air, expands through a converging-diverging nozzle and impacts the target surface at high speed. The design of the facility is similar to that reported by Caimi and Thaxton (1). The advantage of this facility over conventional high speed water jets is that the amount of water consumed is extremely low, typically 30-40 ml/min. Thus the disposal of the waste water is greatly simplified. This work explores the performance of the jet impingement facility over a range of operating conditions using different nozzle configurations. The performance is characterized by the rate of residue removed, which is measured using a laser reflectivity technique. It is demonstrated that the optimum rate of residue removal is achieved when the air temperature is as high as possible without evaporating liquid and the water flow rate is as high as possible without water droplets agglomerating. Based on theoretical considerations in conjunction with the experimental results, there exists strong evidence that the residue removal mechanism is due to emulsification upon liquid droplet impact with the target surface. Potential applications for the jet impingement facility, such as use with non-ozone depleting solvents, reach far beyond the aerospace industry.
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