密封槽结构形式对液压缸内泄漏的数值分析

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Mar.2013机 床 与 液 压Hydromechatronics Engineering Vo1.41 No.6DOI：10.3969/j.issn.1001-3881.2013.06.015Numerical Analysis about Effect of the Different ClearanceSeal on Hydraulic Cylinder Leakage RateTANG Jie ，WANG Liwen ，CHAI Xiaoming。，LIU JingJ.Aviation Ground Special Equipments Research Base，Civil Aviation University of China，Tianjin 300300，China 2.Hebei Steel Group Chengde Branch，Chengde o67lo2，China。

1.IntroductionAbstract：In this paper，according to the internal leakage of the low-friction hydraulic cylinder，ithas been compared that the leakage rate of the sealing groove of the three diferent structures byusing CFD software.And the optimal structure form of the clearance seal is obtained.Therefore。

this paper provides a basis for the rational design and selection of the hydraulic cylinder sea1。

Key words：sealing groove，internal leakage，numerical analysis，hydraulic cylinderIn the hydraulic system，the eficiency of the hy。

draulic cylinder is crucia1. Usually we can use thering seal and clearance seal to improve the eficiency。

For a cylinder with clearance seal，the volumetric efi-ciency wi1 be decreased as the increase of workingpressure and gap.On the contrary，the mechanical ef-ficiency will be jncreased.Therefore.according to thetheory of energy loss，there is a reasonable clearanceand working pressure which corresponds to the optimalefficiency.Simultaneously，the cylinder wi1 becomelow-friction as the existence of hydraulic centeringforce(as shown in Fig.1).Clearance seal cylindercan minimize friction to the maximal extent and im-prove the mechanical eficiency.It wil also enhancethe low speed performance.Therefore，creeping phe-nomenon can be avoided。

In this article，CFD software is used to analyzethe hydraulic cylinder leakage of three kinds of clear-anee seal structures.And the emciencies of the oorre。

sponding structures are obtained.Through the compari-sion，the optimal clearance seal structure has been de-termined and the influence of seal clearance on leak。

age and the value range of gap have been discussed。

Received：2012-10-29TANG Jie.E-mail：tangjfirst###yahoo.anAll the works mentioned above provide the basis forthe reasonable designing of clearance seal[1]。

Fig.1 Low-friction hydraulic cylinder2.The leakage of the clearance sealAs shown in Fig.2，the basic cause of leakage isthe pressure difference between A and B sides.Thepressure decreases from P1 to P2，and the pressuredrop is P P1-P2.The pressure drop is caused byfriction during the movement of liquid， which iscalled flow resistance for short.If part b is exposed toatmosphere，the pressure drop is equal to the pres-sure of working chamber(Pp1).If the leakage co-eficient is s， the leakage quantity is evaluatedby[2-3]：QsP。

Similar to the space between piston and cylindercasing，the space between piston rod and hydrauliccylinder is an annular channe1. For simplifcation，the influence of temperature and pressure are ig·nored.The equations of leak quantity are as follows：TANG Jie，et al ：Numerical Analysis about Effect of the Different ClearanceSeal on Hydraulic Cylinder Leakage Rate 79lows：Q ×10。(L/min) (1)The equation of pressure drop is defined as fol-p ×108(kg ) (2)The equation of seal length is defined as fol-lows： . ×1。 (cm)Where， s leak length， and 6 upper deviation of hole-lower deviation of the Axis2 and'/3 is kinematic viscosity of the hydraulic medium(×10 m /s)。

口尸bFig.2 Clearance seal3. Numerical computation of diferentseal structures3.1.Analysis of the model structureIn the Fig.3，the line represents the wall of cyl-inder and the lower half of these figures representsthe dynamical pressure slot. Assume that P 10MPa，the kinematic viscosity of the hydraulic mediumis 0.010 625(pa·s)，Leakage Flow Rate Q2(L/min)，the leak lengthformula(3)，the piston 40 mm。

0.3(mm).According tolength of clearance seal is L皿 (a)Triangle structure (b)Rectangular structure(c)Trapezoid structureFig.3 seal grooves3.2.Condition and methods of calculation3.2.1.Assumption of numerical analysis1)Liquid is under ful lubrication condition，and the liquid membrane is continuous。

3、The viscosity is constant.Seal remains non-contact.The generated heat is relatively smal，sothe change of fluid temperature could be ignored。

3.2.2.Control equation1)Mass conservation equation塑 生( ：0at ax a az2)Momentum conservation equation(4) ( )塑ox -CO'Txx- - ～ (5)O y OZ 、 (puV)塑Oy -OTxy- Fyco(p w)- (p ) - co'rxz- COy - COz (6)(7)Where，P is pressure； ，7-v and were the corn-ponents of viscous stress T on the micro unit F ，Fyand F z represent the component forces of externalforce at the three-dimensional space。

3)Energy conservation equationThe energy conservation is a basic law that thefluid system must meet.This law can be stated as fo1。

1ows：the energy increase of a micro unit is equal tothe total net increase of micro unit，work done bybody force and surface force4]。

p (e孚) (rV T)pfV (PV) (8)4.Analysis on the result of num erical cal-culationWhen the pressure in high pressure chamber is10 MPa and the low pressure is 0 MPa，CFD softwarewas adopted to simulate the fluid flow within sealclearance.And the main parameters of three differentkinds of structures could be obtained.These parame。

ters could reflect the fluid flow conditions withingaps·Fig.4 demonstrated the velocity distributions forthe three different kinds of sealing grooves.As shown8-5 -l --80 Hydromechatronics Engineeringin this Figure.there iS vortex located at the center ofthe groove.TrapezoidS vortex is the most obvious，and triangleS vortex is the weakest one.The sealperformance is inversely proportional to turbulent ex-tent. Therefore， the sealing ability of trapezoidalstructure iS the best one for these three structure，andthe triangular structure iS the worst。

(a)Triangle (b)Rectangle(c)TrapezoidFig.4 Velocity flow fieldFig.5 is the speed curve of sealing curve. Asshown in Fig.5，the speed of rectangle clearance isthe fastest one. The speed of triangle is thelowest one。

O0240O220O200018.0160.014曼 00120.010Oo08O 060004Oo02O0 0.01 0 O2 0 03 0 04L/mFig.5 Velocity curveThe leakage rates of these three kindsgrooves were shown in Tab.1.The leakageof sealrate oftriangular is the largest， and the trapezoid is thelast one。

Tab.1 Leakage rateseal structures The leakage rates(kg/s)trianglerectangletrapezoid0.220.200.165.ConclusionsBy comparing the perform ances of three differenttypes of seal structures， the following conclusioncould be drawn：1)Triangle has the lowest turbulent extent.Italso means that the dissipated energy is the lowest。

Therefore the sealing perform ance of triangle is theworst。

2)If the gap sizes are equal，the leakage rate oftriangle is the largest，and that of trapezoid is thesmallest。

密封槽结构形式对液压缸内泄漏的数值分析唐 杰 ，王立文 ，柴小明 ，刘 静1.中国民航大学 航空地面特种设研究基地，天津 300300；2.河北钢铁集团承德分公司，承德 067102JI Yanfei.LIU Zhiyong.The numerical ananysis of the influence of seal gap on leakage rateJ].Compressor tech-nology，2010(4)：9-10。

TIAN Chunyu.ZHANG Qiuxiang.Simulation of LineGroove Dynamic Seal By Use of Fluent[J].HydraulicsPneumatics&Seals。2008(4)：27-30。

LIU Yunyu，ZHANG Keyu.Th e study of Internal sprayfluids dynamic seal spindle structure and seal forceJ]。

MA Shim n，CHEN Xi.Numerical simulation of free pis-ton Stirling refrigerator compression piston clearance sealleakage[J].Cryogenics，2011(3)：24-28。

WANG Fujun.Computational Fluid Dynamics Analysis[M].Peking：Tsinghua University Press，2004。

摘要：针对低摩擦液压缸间隙密封的结构形式，通过 CFD软件对3种不同结构的密封槽泄露情况进行分析 ，得到 3种不同结构时液压缸的效率。通过对比分析得出间隙密封的最优结构形式，为液压缸密封形式的合理设计和选用提供 了依据。

关键词：密封槽；内泄漏；数值分析；液压缸中图分类号：TH121√ √、 。