Abstract: A novel voice coil motor direct-drive single stage high-pressure pneumatic servo valve is designed. And then the gas flow jet angle is investigated with numerical simulation, while the high-pressure gas flows through the valve orifice for the servo valve. At present, many studies about flow force are concentrated mainly on hydraulic valves, not on pneumatic valves. It is the reason that the gas flow force acting on the spool of low-pressure pneumatic valve is less, owing to small viscosity and density of low-pressure gas; besides the research on high-pressure pneumatic servo valve is seldom-reported so far. However, the velocity of gas flow is up to sonic when high-pressure gas flows through the micro servo valve orifice. And therefore, the steady gas flow force, generated by high pressure and high speed gas flow, cannot be neglected and is an important disturbance for the voice coil motor direct-drive high-pressure pneumatic servo valve. The jet angle for spool valve is usually considered as 69° to calculate the steady flow force, whose prerequisite is two-dimensional, irrational, inviscid and incompressible flow. In this paper, the high pressure gas flows through the servo valve is 3D compressible flow. Consequently, the numerical simulation with computational fluid dynamics(CFD) is adopted to analyze the internal flow filed and jet angles for the servo valve orifice with different valve openings. The simulation results are compared with classical theoretical formula, the results demonstrate that the gas jet angle for the servo valve is more than 69° and different with various spool openings.

Key words: High-pressure electro-pneumatic servo valve, Jet angle, Numerical simulation, Rectangle spool valve orifice, Wall-attached gas jet