Two-phase jet impingement for non-volatile residue removal

Abstract

Abstract

A high-speed jet impingement facility, which was developed for non-volatile residue removal from aerospace components in contact with liquid oxygen, has been fabricated and tested. A two-phase mixture, consisting of water droplets suspended in air, expands through a converging—diverging nozzle and the resulting jet impacts the target surface at high speed. The advantage of this facility over conventional high-speed water jets is that the water consumed is extremely low, typically 1.67 × 10⁻⁴-16.7 × 10⁻⁴kg/s. 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/liquid mixture temperature is as high as possible 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 residue removal mechanism is due to emulsification upon liquid droplet impact with the target surface. Potential applications for the jet impingement facility reach far beyond the aerospace industry.