Abstract:Compressed air is used to transport hail particles in the hail continuous ejection device. In order to study the hail ejection motion low the corresponding pneumatic transport calculation model is established to study the hail ejection velocity velocity law, and the calculation results are analyzed to guide the design of hail ejection device. The flow of compressed air in the system is simplified as a fluid network. For the flow in friction pipe with constant cross-section, the initial value problem is solved by Runge Kutta method to obtain the distribution of total pressure, static pressure and other parameters. The free flow resistance model of particles is used to analyze the force of particles in the ejection pipe, and the motion process and final ejection velocity are obtained. The key factors affecting the ejection velocity are analyzed. The results show that with the increase of the air pressure, the air flow and the ejection speed increase gradually, and the ejection speed increases slowly; With the increase of the length of the ejection tube, the air flow rate decreases gradually, and the ejection velocity first increases and then remains unchanged; With the increase of the inner diameter of the ejector tube, the air flow increases exponentially, and the ejection speed also increases, but the growth trend is gradually slow. It can be seen that the diameter and length of the ejector pipe should not be too large. The calculation results are of guiding significance for the design of the test device.