On Fluid Characteristics And Spool Deformation Of The Spool Valve In A Small Opening For A Electro-hydraulic Servo Valve

Electro-hydraulic servo valve is the core component of the electro-hydraulic control system, its performance is directly dominated to the control characteristic of the control system. Now the research mainly concentrates on the control characteristics, but the study on the effect of valve fluid characteristics and spool deformation to the performance of the servo valve is just beginning. On account of this, a 6 mm valve of two stage servo valve is used as a basic structure. In order to investigate the influence of the flow field and spool deforming of the spool valve for servo valve with a small opening to the valve, the theory of computational fluid dynamics, numerical calculation method, FLUENT and ANSYS, were used to simulate the flow field and the deformation of spool. The main work is as follows:(1) With the simulation of the flow field in steady-state and transient-state by FLUENT, the contours of velocity were obtained. The results show that the jet angle is increasing as the decrease of the opening. When the opening is 0.5mm, the jet angle is smallest, 58 degree, and, the jet angle is about 83 degree at the 0.1mm of opening. By extracting the calculation data, the curves of flow characteristic, steady-state flow force and transient-state flow force of the valve port were drawn and then the differences between theoretical curve and simulated curve were discussed.(2) Simulation of the flow field for various openings equispaced on spool and different velocity was performed and then the influences of characteristic on valve port were analyzed. The results show that: the 8 openings equispaced on spool have a smaller steady-state and transient-state flow force, the 2 openings equispaced on spool have a larger steady-state and transient-state flow force.(3) The simulation result of flow field is loaded to ANSYS structural analysis software for co-simulation. Simulation of the spool deforming for different valve opening and various openings equispaced on spool was performed. The results show that, the maximum deformation is gradually decrease in the range of 0- 0.5mm; the maximum deformations increase from 8.54μm to 8.58μm in the range of 0.2- 0.3mm; spool shoulder deforming is very small, almost negligible; the maximum deformations decrease gradually with the number increase of openings equispaced on spool. The 8 openings equispaced on spool has the least deformtion, about 2.73μm. In order to have a low manufacture cost, the 4 openings equispaced on spool should be used.