Flow Field Characteristics Research And Malfunction Simulation Analyses On The Three-stage Servo Valve

As the key component in electro-hydraulic servo control system, three stageelectro-hydraulic servo valve has been widely used in many testing equipments andheavy machinery. In order to design a more high-performance three stageelectro-hydraulic servo valve, while reducing the cost of equipment development,we must study all the key technologies of three-stage electro-hydraulic servo valve.Generally, the power stage of three stage electro-hydraulic servo valve is aspool valve. In the flow field characteristic analysis of main power slide valve, thefluid simulation software is FLUENT which is widely used internationally. Nullposition characteristic of the ideal valve is acquired by simulations. Then thedetailed simulation and analysis of main power slide valve taking into account valvespool edge rounding and radial clearance are studied, thus discharge characteristiccurve and discharge coefficient are acquired. All the characteristic curves arecompared with the ideal characteristic curves, the influence law is obtained.Then flow states switching phenomenon at valve port of main valve issimulated based on the dynamic mesh technique for the first time. The simulationresults show that Flow states switching phenomenon leads the dischargecharacteristic of main valve to be discontinuity. It is discovered that the roundingcorner of valve stem and spool land will improve the linearity of dischargecharacteristic of main valve, accordingly reduce the negative impact of flow statesswitching phenomenon.Furthermore, this paper studies the steady-state fluid force of the slide valvebased on the dynamic mesh technique. The influences of different work temperatureand different working pressure on the steady-state fluid force are respectivelyresearched, Results show that in the allowable range of working conditions, workingtemperature and pressure have little effect on the steady-state fluid force. Finally,the measure that how to reduce the steady-state fluid force of the slide valve isresearched.In the simulation study of typical faults of three stage electro-hydraulic servovalve, this paper chooses AMEsim and MATLAB/Simulink software as researchtools. First, the whole simulation model of three stage electro-hydraulic servo valveis established based on AMEsim, then this paper simulates the common failure ofthree stage electro-hydraulic servo valve and obtains fault simulation curve samplesof common fault of the servo valve. Through fault simulation systems revealed a state of failure, fault diagnosis for hydraulic system and provided reference. Finally,based on MATLAB/Simulink software, this paper establishes the simulation modelof three servo valve and studies on the effect of sphere wear and flutter on theperformance of the servo valve. The simulation results show that the sphere wearcan lead a deterioration of the no-load flow characteristics and Flutter signa l caneffectively eliminate the clearance generated by the dry friction and prevent theblockage of three stage electro-hydraulic servo valve.