| As an important control component of a hydraulic system,the working performance of hydraulic valve has an important impact on the stability,accuracy,and reliability of the hydraulic system.Exploring the variation of parameters such as fluid velocity and pressure in the valve with operating conditions and further exploring the distribution of flow field in the valve is of great significance for the rational design of valve core,valve body,and flow channel structures to improve the comprehensive performance of hydraulic valves.Hydraulic valves were subjected to interference from flow force almost all the time during operation.Excessive flow force can hinder the movement of the valve core,cause inaccurate movements,and even cause valve core opening and closing failures,jitters,and loss of control.Therefore,it is important to explore the forms and influencing factors of flow force and reasonably compensate for flow force to improve the stability and accuracy of hydraulic valves.CFD was used in this thesis to analyze the steady-state flow field distribution of hydraulic valves under different opening conditions,different pressure differential conditions,and different annular cavity diameter ratios.By analyzing the steady flow field of a hydraulic valve under different opening conditions,it was found that the jet angle at the throttle outlet is inversely proportional to the opening.When the jet angle was small,a larger area of vortex would be generated at the outer wall of the outlet.The angle between the pressure interface at the throttle outlet and the horizontal plane gradually decreased as the opening increased.By analyzing the steady-state flow field of a hydraulic valve under different pressure differentials,it was found that the distribution of fluid velocity,pressure,and pressure interface within the valve were not affected by pressure differentials,but the pressure and velocity at the same location were proportional to the pressure differentials,the maximum velocity of the fluid was nonlinearly related to the pressure differentials,and the maximum pressure of the fluid was approximately linearly related to the pressure differentials.By analyzing the steady flow field of a hydraulic valve under different annular cavity diameter ratios,it was found that the larger the annular cavity diameter ratio,the greater the fluid velocity in the annular cavity,the smaller the pressure,and the less obvious the vortices in the cavity.The calculation formulas for the throttling area of common U-shaped and triangular throttling grooves were derived in detail.Based on Matlab/Simulink,the calculation models for the throttling area of the two types of throttling grooves were established,and the influence of structural parameters of the throttling groove on the throttling area was studied.The steady-state flow field distribution of the throttling groove under different opening conditions and different pressure differential conditions was analyzed.The causes of hydraulic valve flow force were analyzed,and the calculation formulas for steady-state and transient flow force of hydraulic valve were derived in detail.The key factors affecting flow force were pointed out.Based on the mechanism of flow force generation,a jet guiding groove was proposed to compensate for the flow force of hydraulic valves.By comparing the steady-state flow fields of the two valves under different opening conditions and different pressure differentials,it was found that the jet guiding groove could effectively increase the jet angle at the throttle outlet.By comparing the flow forces of the two valves under different opening conditions and different pressure differentials,it was found that the flow forces of both valves increase with the increase of opening,and the greater the pressure differentials,the more obvious the changes in flow forces with opening.The flow forces of both valves increase with the increase of pressure differentials,and the greater the opening,the more obvious the change of flow forces with pressure differentials.The influence of the structural parameters of the jet guiding groove on the flow force compensation characteristic was analyzed,and the optimization analysis of the jet guiding groove was carried out with the minimum flow force as the optimization objective.A polynomial regression model of the flow force and the structural parameters of the jet guiding groove was fitted,and the single factor response and interactive factor response of each parameter were analyzed,and the relationship between each parameter and the response was explored.The response surface of each parameter and flow force was established.Through the analysis of the surface graph and contour map,the specific gravity of the influence of each factor on the flow force was further explored,and the optimal solution of the structural parameters of the jet guiding groove with the goal of minimizing the flow force was obtained.The effectiveness of the jet guiding groove for flow force compensation was verified through experiments,and the stability characteristics of the flow force compensation were analyzed. |
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