In a water hydraulic jet pipe servo valve, the overall performance of the valve is directly influenced by the structure dimension of the receiver and the prestage— jet pipe amplifier. This paper deals with the influence rules of the structure dimension parameters and performance parameters on the buildup pressure in the two receiving holes, including the vertical clearance between the nozzle and the receiver, the diameter of the nozzle hole, the diameter of the receiving orifice, and the nozzle offset distance. The best combination of structure size is finally obtained by using numerical simulation, computer emulation and experiment analysis methods. Then build up the finite volume analysis models about the pressure field and the speed field of the jet pipe amplifier. Through analyzing the characteristics of the flow field, a mathematics relation between the jet nozzle offset and the pressure ratio inside the two receiver holes is established, which reveals the energy distribution and conversion mechanism. The conclusion could be an important reference for the design and research of jet pipe servo valve.

The cavitation flow characteristics in jet pipe amplifier with different nozzles were simulated using commercial computational fluid dynamics (CFD) software. The influence of operating parameters and structural parameters of jet nozzles on cavitation jets are the key objective. These parameters mainly include inlet pressure, outlet pressure, temperature of water, nozzle convergence angle, the length of the nozzle cylindrical section, nozzle diameter and nozzle export chamfer angle. The results provide methods to limit the emergence and development of the nozzle jet internal cavitations.