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滑阀节流棱边圆角对流量特性影响的三维模型仿真

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机床与液压 Jun.2013 Hydromechatronics Engineering Vo1.41 No.12 DOI:10.3969/j.issn.1001—3881.2013.12.002 Numerical Simulation Study on the Influence of Arris-edge Fillet of Spool Valve on Flow Characteristics WANG Dongwei,YE Zhengmao School of Mechatronics Engineering,Harbin Institute of Technology,Harbin 150001,China Abstract:The flow characteristic of the spool valve affects the performance of the servo valve.U・ sing Fluent,this paper discusses the following four cases:the ideal spool valve,the spool valves with arris-edge fillets of 5,8 and 10 tam.The effects of diferent fillets 0n the valve’s flow charac- teristics are discussed and a correction formula for the flow coefficient of ideal spool valve is pro- posed by polynomial approximation of the simulation results. Key words:flow characteristics,Fluent,the working arris-edge fillet The research on the flow characteristics of spool 1.Introduction valve is quite dififcult for the following two reasons: ①It is dififcult to detect a opening of only a few mi- A three—stage electro—hydraulic selwo valve is the crons in the experiment.( The theoretical formula key component of high power electro—hydraulic servo is derived from the simplified model and thus the for. control systems.Because of its outstanding features mula is not effective in certain circumstances l 5 f. such as large capacity,high-frequency response, Numerical simulation can overcome these shortcom. high resolution and high reliability,etc,three-stage ings,and it is relatively easy to apply,so this paper electro.hydraulic servo valves have been widely used studies the effect of the working arris—edge fillet of in many high-performance apparatus including 6一DOF valve spool on the flow characteristics using Fluent. motion simulators.vibrating tables and load simula- tors,etc『1—2].Generally,the main valve of a 2.Theoretical formula of the slide valve three—stage electro.hydraulic servo valve is a spool lfow characteristics valve.and its fluid flow rate is controlled by chan. ging the flow area of the valve port by the relative mo— The ideal model of the spool valve is shown in tion of the valve spool and sleeve『3]. Fig.1,it shows that,aside rfom the two left and fight The flow characteristic of the spool valve affects control channels,the valve has four channels con- the performance of the servo valve.Actually,the necting the outside hydraulic circuits,namely port P, working arris-edge fillet is unavoidable in practical port T,port A and port B.Port P connects to the manufacture.The presence of the fillet has great in. pressure oil source,port A and port B connect to the lfuence on the servo valve flow characteristics. two load cavities of actuator respectively,and port T Therefore,this study provides insightful guidance for connects to the tank.It is often assumed that the pos- the manufacture and testing of servo valve J 4 1. itive direction of the spool valve is moving to the irght,thus,port 1 and port 4 are open,port 2 and port 3 are closed.In this assumption,port 1 and port Received:2013—03—17 4 are working valve ports. National Natural Science Foundation for young(51205077) YE Zhengmao.Associate professor.E—mail:yezhm@hit.edu ideal spool valve,the valve port model is shown in Fig.2. ca WANG Dongwei,et al:Numerical Simulation Study on the Influence of Arris-edge Fillet of Spool Valve on Flow Characteristics 7 teristic curve should be the asymptote based on the lfow characteristic curve of the ideal spool valve.The lfow characteristic curve is shown in Fig.4. Q l/min J Fig.1 Structure of the ideal spool valve alve —/ O xJtjm Fig.4 Flow characteristic curve 3.The geometry model and the simula- tion method Fig.2 The valve port model of ideal cylindrical spool valve According to the Fluid mechanics,the flow for— The simulation model in this paper is shown in mula is: Fig.1.The following four spool valve models are es— Q。=CzA (1) tablished:the ideal spool valve,the spool valves with Where: Q。 is flow,Cd is flow coefifcient,A is the flow working arris—edge fillets of 5p,m,8p.m and lOp ̄m. area of throttling port,P is density of hydraulic oil From Fig.1.the conclusions can be drawn that the (kg/m ),Pl pressure inlet(Pa),P2 is pressure valve has two symmetircal valve chambers and both outlet(Pa). valve chambers are axisymmetrica1.To reduce the In this paper,the spool valve is made up of four calculation.only 1/4 model of a single valve cham— throttling ports,so the flow formula of spool valve is: ber needs to be established. Q=4Q0=4CdA (P 一P2)/V (2) hTe main purpose of the simulation is to obtain However,the radius of the arris—edge fillet for a the flow through the throttling port of the valve.The real spool can not be zero.An actual spool model is overall length of the model is up to 30 mm.Howev. shown in Fig.3. er,the size of the opening is just tens of or even sev— eral microns.the proportion of the two sizes is so large that it brings great diifculties to give the model a proper mesh.To ensure the accuracy of the calcu. 1ation and improve computational efifciency.the local mesh refinement method should be adopted[6].The meshed model is shown in Fig.5. Fig.3 The actual spool valve model Now the flow formula of the spool valve is: Q=4c B 丽一r) (3) where B is the width of the throttling port. The flow characteristics can be analyzed by the Fig.5 The meshed model formula(2)and(3).Ifthe change ofthe flow coef- ifcient is ignored,for ideal spool valve,the flow will hTe meshed models are imported into Fluent,a change with the opening of the valve linearly. series of parameters should be set[7].After running And for the actual spool valve,its flow charac- the simulation,the flows in different openings can be 8 Hydromechatronics Engineering obtained and the flow coefifcients in different opening can be calculated accordingly. leakage at the zero position.And larger fillet radius ) will lead to greater flow leakage.The larger the fillet 222221ll1lOOO radius is,the greater the flow leakage will be. 864208642O 864 4.Simulation results and analysis 5.Effects on the flow coefficient This paper mainly discusses the situation when the opening is less than 100 m,and 17 points are selected for research.The three.dimensional models in these different openings are established。then the The following conclusions can be drawn from Fig.7: 1)For an ideal spool valve,it is generally be— models are meshed and simulated,and a series of the lfow values can be obtained.From the simulation re. suits,the flow characteristic curves can be drawn as shown in Fig.6 and Fig.7. 50o0O 400o0 暑300o0 20000 1O00o 0 0 20 40 6O 8O 100 Openingh ̄m Fig.6 The flow characteristic curve 0 20 40 60 80 10O Opening. m Fig.7 The flow coefifcient curve According to Fig.6,the following conclusions can be drawn: 1)The flow characteristic curve of the ideal spool valve is approximately linear. 2)With the same opening,the flow increases with the arris-edge fillet. 3)If the arris—edge fillet is held constant,with the increase of opening,the influence of the fillet on the flow becomes smaller and smaller. When the 0一 pening is large enough,the lfow characteristics of the actual spool valve get close to the flow eharacteristics of the ideal spool valve. 4)Because of the arris—edge fillet,there is lfow lieved that the flow coefifcient is constant.However, the flow coefficient changes along with the opening and this change is particularly obvious in the micro—o. pening.Then with the opening increasing,the flow coefficient is substantially a constant. 2、If there is a arris-edge fillet on the spool valve.its flow coefficient will be larger than that of the ideal spool valve and wil1 increase with the fillet’ s size.This can be explained by the fact that the presence of the fillet lcads to the increase of the flow area. Apply a polynomial approximation to the flow coefifcient of the ideal spool valve(when the opening is less than 40 m)and the formula can be ex. pressed as: Cd=一8.315 7×10一 +8.539×10-5 :一 0.003 2x:+0.054 5x.,+0.374 6 this is the correction formula for the flow coemcient and it can be used directly to calculate the flow in later applications without any complex simulations. 6.Conclusions In this paper,the influence of the arris-edge fil— let on the flow characteristics of spool valve is stud. ied.First this paper uses the theory of lfuid dynamics to analyze the effect ofthe arris.edge fillet on the flow characteristics.Then based on Fluent。numerical sim. ulation of the above.mentioned effect is carried out. The result of simulation indicated that the exist— ence of the arris—edge fillet will increase the flow area of the spool valve,1 eading to the deterioration of the lfow curve linearity. Larger fillet will result in worse linearity and greater leakage at zero position,and this will seriously affect the performance of the servo valve.Therefore,a more reasonable processing tech— nology should be adopted to minimize the arris-edge ifllet. Finally,based on the simulation results,this paper gives the flow coefficient correction formula at WANG Dongwei,et al:Numerical Simulation Study on the Influence of Arris.edge Fillet of Spool Valve on Flow Characteristics 9 the micro・・opening to avoid the complicated simula-・ value hydraulic measuring system and the key technics of tions.The flow can be directly obtained by the f0r- the systeml J 1.Dissertation for the doctorla degree in en. ?u a,which pr。Vides guidance r sp。。 Va Ve’s es。 [4]gineering,2007(9):7—20. tln g・ Finnemore E J。Franzini J B.Fluid mechanics and engi. neering application[M].Beijing:China Machine Press,2005. References: [5] Tsukiji T.Discrete.vortex simulation of a two.dimension. al lfow in oil hydraulic valves[J].Journal of lFuid Con— HAN Junwei,LI Hongren.Application of Fluid Control trol,1991,21(1):43. Technology in the Environment Analogue and Simulation [6] Chen Q,Stfofel B.CFD simulation of a hydraulic coni— Test Facilities『J].nuid Power Transmission and Con— cal valve with cavitation and poppet movement[c]// tro1.2005,3(2):34—38. 4th International Fluid Power Conference.Germany: [2] FANG Qun,WANG Zeng.Developing Process,Re- Dresden,20o4:331—339. search Actuality and Trend of Electrohydraulic Senrova1v0 [7] Pountney D C,Weston W,Banieghbal M R.A Numefi. [J].Machine Tool and Hy ̄aulics,2007(11):162 cal Study of Turbulent Flow Characteristics of Senro.valve —165. Oriifces[C]//Proc Instn Mech Engrs.1991:139—147. [3] PAN Xudong. Study on ser ovalve spool valve overlap 滑阀节流棱边圆角对流量特性影响的三维模型仿真 王东魏,叶正茂 哈尔滨工业大学机电工程学院,哈尔滨150001 摘要:滑阀的流量特性直接影响伺服阀的性能。使用Fluent软件对滑阀在不存在棱边圆角(理想滑 阀),棱边圆角分别为5 m、8 m和10 m等4种情况进行数值仿真研究,得出棱边圆角对滑阀流 量特性的影响规律,并对理想滑阀的流量系数进行了修正。 关键词:流量特性;Fluent;节流棱边圆角 中图分类号:TH12 

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