Experimental Study On The Atomization Characteristics Of Impinging Jets

Because of the good atomization and mixing characteristics under different injection pressures, and the structure is simple, easy to manufacture and maintenance, dual impinging jets has been widely used in liquid rocket engine. The quality of the spray formed by impinging jets atomizer is affected by jet velocity, impingement angle, nozzle characteristics, and the liquid characteristics, therefore, to study the effect of various factors on the atomization characteristics is of great significance for the understanding and application of impinging jets.This paper reviews the liquid sheet, spray angle, droplet characteristics, as well as the measurement system in the research of impinging jets at home and abroad firstly. Then, based on the shortcomings of current research content and methods, the research content, research programs and conditions of this article were determined.According to the research content, the principles of the experiment platform was determined: high-pressure nitrogen gas drive high-speed flow of liquid forming two jets, the spray would form after two jets passing through the azimuth adjustment system and impinged together at an angle. We calculated frictional resistance and local resistance of the pipeline system, to determine the required pressure value, and system specific parameters. Finally, we debugged the experiment platform and CCD camera system, to ensure they were in the best working state.With deionized water as the working fluid, we explored the influence of jet velocity, impingement angle, nozzle diameter on atomization characteristics. The results showed that when the weber number was small, the liquid sheet was complete, but when the weber number was in larger context, liquid sheet began to break down, the droplet distributed like segment under the sheet. At the same time, increasing the weber number could cause the spray angle increases and decreases average droplet diameter. Increasing the jets impingement angle could lead to more severe impingement, make the liquid sheet unstable, the aspect ratio decreasing, spray angle increasing, the droplet size decreasing. We compared the droplet diameter variance under different weber number and impingement angle, found that increasing the weber number and impingement angle could help increasing instability of liquid sheet, make the droplet distribution more uniform. Also, we found the nozzle diameter had little influence on atomization characteristics through contrasting the spray field formed by 0.67 mm, 0.86 mm and 1.07 mm three different inner diameter nozzle.We studied the effect of viscosity on atomization characteristics, the results showed that glycerol solution had high viscosity, could withstand more severe outside interference, in the process of increasing the weber number, the liquid sheet size would increase gradually, and the greater the liquid viscosity, the greater the size of liquid sheet. In the study of 40% concentration of glycerol solution atomization characteristics, we observed the phenomenon of liquid sheet flip, multiple consecutive perpendicular liquid sheet could appear down from the impact point. Liquid sheet formed by glycerol solution was not easy to expand to the sides because of its higher viscosity, and its greater density made gravity influence more obvious, so spray field of glycerol solution showed small spray angle, under the same conditions of the jet velocity, and the greater the viscosity, the smaller spray angle. We analyzed the characteristics of droplets formed by different viscosity liquid, found that the average droplet diameter increasing with the viscosity increasing, but droplets characteristics was less affected by viscosity, under the condition of high weber number.