| Hydraulic servo valve was the core control component of hydraulic servo system,which was widely used in special equipment,aerospace,ship,automobile and military.As a power level hydraulic servo spool valve,the valve orifice was easy to be eroded by particle pollutants in high pressure jet oil,which led to the passivation of the valve orifice working edge and induced the performance degradation of the hydraulic servo valve.In order to solve the above problems,this study established a valve orifice flow field calculation model considering erosion morphology through external characteristic experiment of servo valve,flow field simulation calculation and erosion working edge profile analysis,proposed a precise calculation method of erosion valve orifice area based on elliptic curve,studied the influence of spool valve orifice erosion on servo valve performance,and revealed the erosion effect of hydraulic servo valve spool valve orifice.This paper provided theoretical basis for performance evaluation of high performance servo valve.The main work and research results were as follows:(1)Flow characteristics of valve orifice considering erosion morphology.The automatic zoom 3D topography instrument was used to measure the erosion morphology of the working edge of the spool,and the servo spool valve erosion surface model was established and the flow field simulation was carr ied out.The results showed that the influence of working edge erosion on the flow characteristics of small opening valve was significant.The spool valve orifice was eroded and worn,the position of the minimum flow cross section change d,the valve orifice area increased,the pressure gradient range increased,and the oil incidence angle decreased slowly at the valve orifice with a small opening.Compared with the valve orifice without erosion,it was easier to form a low pressure area and vortex under a small opening.(2)Accurate calculation model and method of erosive valve orifice area based on elliptic curve.Based on the analysis of the contour curve of the working edge,the fitting method of the contour of the working edge of the valve orifice with elliptic curve was proposed,and the valve orifice area was programmed by MATLab.With the increase of ellipse long diameter and the ratio of short diameter to long diameter,the area of erosion valve orifice increased and the sealing length of spool valve sleeve increased,which maked the valve orifice degenerate from zero opening to positive opening and led to the degradation of control performance near zero position of servo valve.(3)Influence of spool valve orifice erosion on servo valve external characteristics.An AMESim model for static and dynamic erosion characteristics of servo valve spool valve orifice was established,and the calculation results of erosion valve orifice area were input into the custom valve orifice model,and the influence of erosion valve orifice on the external characteristics degradation of servo valve was analyzed.The ratio of ellipse length-diameter to length-diameter was linear with pressure gain and leakage.When ellipse length-diameter increased by 4 times,pressure gain decreased by0.51 times and leakage increased by 4.17 times.When the ratio of ellipse short diameter to long diameter increased by 0.1,the pressure gain decreased by 0.1times and the leakage increased by 1 times.The erosion valve orifice had no effect on the dynamic characteristics of hydraulic servo valve. |
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