液壓橫移式加熱爐出鋼機設計含9張CAD圖

液壓橫移式加熱爐出鋼機設計含9張CAD圖,液壓,橫移式,加熱爐,出鋼機,設計,cad CHINESE JOURNAL OF MECHANICAL ENGINEERINGVo1.22，No.1，2009DOI：103901CJME200901109，available online at www.cjmenet.com；www.cjmenet.com.cn Water Hydraulic 22 Directional Valve with Plane Piston Structure GONG Yongjun，YANG Huayong ，and WANG Zuwen1 Laboratory of Fluid Power Transmission and Control Dalian Maritime University,DaLian 116026,China2 The State Key Lab of Fluid Power Transmission and Control Zhejiang University,Hangzhou 310027,ChinaReceived July 13，2008；revised November 19，2008；accepted December 3，2008；published electronically February 20，2009Abstract：Due to the fire resistance and environmental compatibility，using water as the working fluid in hydraulic circuits is receiving an increasing attention by both manufactures and usersThis hydraulic directional valve is developedWhen new water hydraulic directional valve is designed and manufactured，this paper introduces a water hydraulic 22 directional valve and its principleThe valve is composed of a hydraulically operated seat valve and a magnetic 32 direction valveAimed at the serious leakage and impact generating easily in reversing suddenly, an improved structure of water space seal is changed to direct seal，compaction force between main valve spool and main valve pocket was logically designed and damper in pilot valve port is matched with sensitive cavity in main valveFrom the view of flow control，the methods of cavitations resistance of the directional water hydraulic valve are investigatedThe computational fluid dynamics approaches are applied to obtain static pressure distributions and cavitations images in the channel of the main stage of the valve with two kinds of structure The results show that the method of optimized spout can effectively restrain cavitationsThe work provides some useful reference for developing water hydraulic control valve with the lower noise and lower vibrationMeantime，the structural parameters are optimized on the basis of information obtained from simulationStatic test，dynamic test and life test are accomplished，and the results show that the water hydraulic directional valve possesses good property, its pressure loss is 1.1MPa lower, switching time is shorter than 0.025 sand its strike crest is 0.8MPa lowerThe valve possess fine dynamic performance with the characteristic rapidly action and lower impulsionKey words：water hydraulic，directional valve，structure optimization，flow field analysis1 IntroductionFor its abundant transmission mediaEnvironmentally friendly, clean and safe，fire resistant，and so on，water hydraulic technology has been turned out to be a focus of research in the field of fluid power transmission and controll Water hydraulic valve as one of the key components，is studied extensivelyThe traditional oil hydraulic directional valve is of spool pilot valve，rotary valve or cone valveAlthough the unbalance force on the rotary valve and the pilot pool valve are weak，the force to operate them are weaker and the leakage are usually bigger with a larger tolerance for the relative movement of the valves and valve seats For its low viscositythe loss of leakage of water hydraulic system is much higherFor the same clearance and pressure，the loss of leakage of the water hydraulic system is several decade times that of oil hydraulic system In order to maintain a reasonable low leakage the clearance should be extremely small，which may lead to difficulty of machiningat the same timeit is easily for the moving parts to be choked and stuck As for the cone valvealthough has a smaller leakage，unbalanced axial fore on the valve exist，so a stronger force is needed to operate it For the incompressible and high stiffness，the hydraulic shock of the water hydraulic directional valve is more serious So how to lessen the leakagehow to realize direction change with low or even no hydraulic shock and how to improve its static and dynamic characteristic are the key issues of study So far-there is no report on the study of water hydraulic directional valve. In this Paper，a new serial of water hydraulic valves has been provided based on the change of seal pattern，reasonable design of pre-tightening force，and optimization of the flow passage2 Experimental Working Principle of the Water Hydraulic Directional Valve Fig.1 shows the water hydraulic directional valveIt is electrohydraulic directional valveThe pilot stage is a 23 electromagnetic directional ball valveBeing different from traditional oil hydraulic valvea valve pocket is added to the main valve，and the main valve pocket is over fitted to the valve bodyThe main valve spool is fitted to the main valve pocket，and the surface sealing is achieved by the plane of the valveLip-type packing are set in both ends to achieve no leakageThe spring is for compensation of the frictional forceBoth ends of the main valve spool are supported radically by bushes， which are made of wear-resisting materials， so the problem of abrasion is settled in this way Fig.1 Sketch of water hydraulic directional valve structureThe structural principle of the valve is as follows: there is damper at the valve port，two dampers in series act as half bridge resistant，and the controlling rib connects to the sensitive chamber on the right side of the valve by the central hole. When the electromagnet is out of power, main valve spool is moved to the right under the force of inlet, at the same time，water in the sensitive chamber is discharged through the pilot valve，and the main valve is openWhen the electromagnet is chargedwater for control is inducted to the sensitive chamber, and the main valve spool is compressed on the valve pocketand the main valve is shut down2.1 Design of the pressing force of main valve spoolThe contact surface of the main valve spool and the valve pocket is plane，there maintains a certain pressing force between them (Fig.2).The pressing force varies according to the change of control fluid pressure，the higher pressure is，the bigger the pressing force will beTherefore，leak age between the main valve spool and the valve pocket is nearly zeroThe stress condition of the main valve spool is as followsFig.2 Sketch of axial force of main valve spoolSuppose that the inlet pressure of the main valve is p，and pressure loss is neglected，so the pressing force of the main valve is p1,，we haveIt is obvious that p1 is positive，which ensures that the main valve spool is pressed against to the valve pocketIf pl is too weak，there will be leak age between the main valve spool and the valve pocket，and if pl is too high，the force for directional change will be bigger and abrasion between the main valve spool and the valve pocket will occursAccording to our experiments，the facial contact force for the main valve spool an d the valve pocket is at best 2 times the inlet pressure PIn the process of design，it is required that2.2 Meshing design of pilot valve damper and sensitive chamberFor the design of directional valve it is not only necessary for a quick directional change，but also a minimal hydraulic shockSo a dam per is set at the inlet of the pilot valve，two dampers in series act as half bridge resistant，a throttle backing pressure is then built up at the end of the main valve，which has a function of retardation andspeed-regulationProvided at any time, there is even pressure in thesensitive chamber an d the compressibility of the fluid omitted，equations will be acquired as follows：Where F is exterior force，f is frictional force，k is the stiffness of the spring，x is buffer distance，Ps is pressure of the sensitive chamber, Ad is area of the main valve spool end， m is the mass of main valve spool， a is shock accelerated velocity,p is differential pressure betweenimports and exports of dam per,A0 is flow area of the damper, v is shock velocity, qv is flow of the damper, cq is coefficient of discharge of inundated ports effluxFrom Eqs.(3)-(7)，the characteristic expression of the pilot valve port is deducedWhen shock energy is too big and throttling area is too smallshock is rather strong and can create bigger frontshock hump， and buffer effectiveness is not good；when the shock energy and throttling area are too big，shock is weak，buffering force is smaller, and residual velocity can exist which may create correlation equation assumed by Launder, the aeolotropism and eddy flow of turbulent current can be well predictedpacket oil phenomenon and bigger back-shock hump at the This paper uses Anisotropic k- model to simulate flow end of the shockTherefore，in the case of proper design，it is required that the damper should match with sensitive chamber，and the damper should have good performance and linearityAccording to experience，linearity of the damper should be less than 30 3 Flow Field Simulations and AnalysisWhen the directional valve is being designed Its pressure loss should be as small as possiblePressure loss of the directional valve usually is determined by experimentDevelopment of calculated hydromechanicsprovides a scientific approach to calculate pressure loss of the directional valve with complex flow passageIt turned out to be an effective method to make use of numerical calculation， with which optimization of the movement，flow and structure of the hydraulic component can be done3.1 Mesh divisionThe mesh of water hydraulic directional its main valve passage is shown in Fig3Main valve passage is threedimensional symmetrical structure， the passages threedimensional model is used for mesh division and flow field calculation in the studyFig3 Mesh of main valve flow passageBecause area gradient of flow field of the computational domain varies greatly, for the purpose of improving calculation accuracy and reducing amount of calculation work，the computational domain has been divided into multiple small sectorsInitial computational mesh is created in GambitIn high speed domain of the main valve port and nearby, velocity gradient is very big，and complex flow pattern exists，better structuring meshes in this domain and coarser unstructured meshes in other areaare applied32 Mathematic model321 Anisotropic k- turbulent modelBecause Anisotropic k-model adopt Reynolds stress correlation equation Assumed by Launder, the aeolotropism and eddy flow of turbulent current can be well predicted. This paper uses Anisotropic k- model to simulate flow pattern of flow field of the directional valves main valve，calculation equation of its turbulent kinetic energy k and turbulent dissipated energy is as follows：Calculation equation of turbulent current frequency isWhere，ui is fluctuation velocity sector in i direction ， ujis fluctuation velocity component in the J direction，P is fluid density, and is absolute viscosity3.2.2 Cavitations modelGas phase volume percent equation can be expressed aswhere，a is gas phase，aa is gas phase volume percent，Pa is gas phase densityl is fluid phasePl=998.2 kgm 3 (fluid phase density)，and l-aa is fluid phase volume percentMean density isAnd mal，is mass transfer between gas phase and fluid phase due to cavitations，it is expressed aswhere Pv is vaporization pressure；n is number of bubbles per unit volume；R is bubble radius which is expressed as3.3 Simulation results and analysis3.3.1 Flow characteristic analysisNumerical calculation is carried out with Fluent softwareIn the calculation there are some assumptions as followsReynolds stress The fluid is uncompressible，flow is of thermal insulation，and there is no slip on the wal1Suppose that the opening of valve port is 4 mmthe inlet flow is 120 Lminand the outlet pressure is the pressure of working water circuit，whose absolute pressure is 1MPaFig.4 shows the static pressure isoline along axial symmetry plane in the flow passage of the main valveIt can be seen that at the nozzle between the main valve spool and main valve pocketthe pressure contour is denser and pressure drop is bigger, which lowered to 0.7MPaFig4 Pressure isoline of mainvalve flow passage(MPa)Fig5 shows the velocity vector distribution along axial symmetry plane in main valve flow passageIt can be seen that after fluid enter chamber, spiral vortex is formed near the main valve spool comer, its central pressure is lower, and spiral vortex dissipates fluid kinetic energy by viscous frictionFig5 Velocity vector distributionof main valve3.3.2 Structure optimization and flow field analysisOn the basis of the analysis above，at the nozzle formed by the main spool and main valve pocket，the fluid will diffuse or shrink suddenly as is limited by the structurewhich may cause the streamline changing sharply, spiral vortex appeared on the comer point will dissipate thekinetic energy of the fluidall of which will cause great pressure 1oss In order to improve the performance of water hydraulic directional valvethe structure of nozzle has to be optimized Fig6 shows the comparison of flow passage before and after optimizationIn order to make the streamline smooth，the optimized valve spool is manufactured to be arc transitional surface，which voids appearance of death angleFig6 Comparison of flow passage beforeand after optimizationSimulation and computation of flow passage of the optimized main valve have been done under the same conditionand the pressure distribution in axial symmetry plane is shown as Fig7It can be seen that at the nozzle where fluid flows into the chamber, the density of pressureisoline decreases，pressure gradient reduces，and pressure loss reduces to 0.3MPa after the structure is optimizedFig7 Pressure isoline of flowpassage after optimization(MPa)The distribution of velocity vector after optimization along with axial symmetry plane is shown as Fig8Fig8 Velocity vector distributionof flow passage after optimizationThere is no spiral vortex on the corner point of main valve near the nozzle，so the optimized structure effectively restrains the appearance of low pressure area in the fluid field4 Experiment and Data Analysis41 Experiment device and methodThe water hydraulic directional valve designed is made of stainless materia1its rated pressure is 14 MPaand maximum flow up to 120 LminIn order to prove the correction of design principle and simulation results, experiments on both static and dynamic characteristics of the valve have been doneThe experiment method refers to related national standard GB 810687 of similar experiments of oil hydraulic directional valve The experiment has been done on the test rig of State Key Laboratory of Fluid Power Transmission and Control ofZheJiang University,Chinaas is shown in Fig.9Fig9 Test rig of water hydraulic componentsFig10 shows the schematic diagram of this experimentAs the medium of water is strongly corrosive， all components of this system are of stainless materialsFig10 Test principle of water hydraulic directional valve1Conversion 2Conversion motor 3 Tap water hydraulic pump4Filter 5Relief valve 6Thermometer 7 Pressure transducer8Valve tested 9Oneway throttle 1 0Flow meterDuring the experiment， relief valve 4 regulates the entrance pressure of the valve being checked，rotation speed of the variablefrequency electric motor 2 is regulated by frequencytransformer 3，which adjusts the discharge flow of water hydraulic pump 1The outlet backing pressure of the valve 9 is adjusted by oneway throttle valve 8 and is measured by flow meter4.2 Experiment results4.2.1 Flow-pressure difference experiment of water hydraulic directional valveIn the experiment of pressure lossrelief valve 4 serves as safety valve whose safety pressure is 18MPaThe valve tested is charged and then its spool is on the position of throughflowTo make the amount of fluid flowing through the valve 9 increase gradually from zero to rated flow by adjusting the discharge flow of water hydraulic pump，and choose several points to measure each points discharge pressure， based on which the valves flow-Pressure difference performance curve can be achievedThe outlet backing pressure of the valve tested 9 can be adjusted by oneway throttle valve 8The value of the flow is read out on the flow meter 1 0，the pressure of inlet and outlet display on the indicating instrument of pressure transducer 7Comparison of the characteristic of flowPressure difference between the result of simulation and experimentis shown as Fig.11Fig.11 Characteristic curve of qvpFrom Fig.11，it can be seen that，for qv=l5 Lmin，the pressure difference between inlet and outlet mainly results from the main valve passage and increases slowly almost like a linear as the flow increasesIn addition，the test result is bigger than the simulation resultThis is because the pressure loss in the test is the sum of the pressure loss of main valve and pilot valve while the optimized result from simulation and computation only includes the pressure loss of main valveFrom the comparison of the structure of main valve before and after optimization，it can be noticed that the optimized pressure loss of main valve decreases notablyAttention should be paid to that for qv 30 Lmin the result of simulation shows that the pressure loss between inlet and outlet decreases as the flow increases；however, this case does not appear, which indicates that there is much discrepancy for the simulation when the flow is smal14.2.2 Experiment of dynamic characteristics of water directional valveAdjust the overflow valve 4 and oneway throttle valve，make the pressure of inlet Pi of the tested valve 9 be the rated pressure 14MPa，and the pressure of outlet P。be the given backing pressure， the amount of fluid flowing through the tested valve is 80 of maximum flowThencharge and discharge the tested valve under rated voltage and the data acquisition system picks the dynamic response curve of the tested water hydraulic directional valveas is shown in Fig.12Fig12 Dynamic response curve of waterhydraulic directional valveFrom Fig.12，the pressure decreasing time t1 is smaller than 0.05 sthe pressure increasing time t2 is smaller than 0.05 sand the charging time and discharging time are almost the same The direction change is quick， the pressure peak produced while reversing is decrease 6 ，and the reversing shock is small，which indicates good dynamic response characteristics423 Experiment on the life of water hydraulic directional valveRespectively set the pressure of inlet pressure of the tested valve to be variable value and the pressure of outlet P。to be remained the specified backing pressure and the amount of fluid flowing through the tested valve to be 100 Lmin， continuously charge and discharge the electromagnet of the tested valve up to l0000 times，and then check the main components of the tested valve，there should be no damage inordinate wearFigs13(a)，13(b)show the response curve of continuous directional change under pressure of 12MPa and 14MPa It is clarified that the dynamic responsive characteristics of the valve are nearly uniform，and direction change is reliable and prompt5 Conclusions(1)This new water hydraulic directional valves pressure loss is small under rated conditionand its speed of directional change is fast while its hydraulic shock is weaktherefore，good dynamic characteristics are obtainedIn the life experimentsthe directional valve operates normally, and its direction change is reliableThe performance of this kind is comparable to the same kind oil hydraulic valveFig13. Life test curve of