NUMERICAL SIMULATION ON THE INFLUENCES

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不同头型高速射弹垂直入水数值模拟

不同头型高速射弹垂直入水数值模拟方城林;魏英杰;王聪;夏维学【摘要】The finite volume method, VOF (volume of fluid) multiphase flow model, and dynamic grid technique were introduced in order to conduct the numerical simulation of vertical high⁃speed water entry process of axisymmetric projectiles with five different heads. The influences of the head types on the cavity shape, the projectile hodrodynamics and trajectory properties were studied. The results show that the head type has significant influences on the cavity shapes, surface closing time of cavities, resistance, depth and speed of water entry process. The radius of the cavity induced by sphere and truncated sphere projectiles is smaller than that of the projectiles with the other three head types. The surface closing time decreases in the order of flat head, sphere head, cone head and truncated cone head. The pressure on the projectiles is pretty high and the distribution of the pressure on the sphere or truncated sphere head is uneven so that high shear stress exists on these heads. The water entry velocity decreases more slowly and the depth increases more quickly as the projectile head has a better streamline. The drag coefficient decreases in the order of flat head, truncated sphere head, truncated cone head, cone head, sphere head.%为研究不同射弹头型对高速射弹垂直入水的流体动力和流场特性的影响，采用有限体积法和VOF（ volume of fluid）多相流模型，并引入动网格技术，对5种不同头型的轴对称高速射弹垂直入水过程进行了数值模拟，分析了头型对空泡形态演化过程、射弹流体动力及弹道特性的影响规律。

平头弹撞击角度对2A12-T4铝合金板失效特性影响的数值模拟

平头弹撞击角度对2A12-T4铝合金板失效特性影响的数值模拟胡静;邓云飞;崔亚男;张银波【摘要】利用有限元软件ABAQUS建立模拟模型,开展38CrSi钢弹体撞击2A12-T4铝合金板数值模拟研究,分析撞击过程中弹体撞击角度对弹道姿态及靶体失效特性的影响.基于数值仿真和实验结果,分析靶体的失效特性,确立不同撞击条件下靶体主要失效模式的转变规律,以及由此对靶体抗撞击性能的影响.研究结果表明:弹体的弹道极限速度随其撞击角度的增大先减小后增大,弹道极限速度在撞击角度约为15°时达到最小值;弹体撞击角度对靶体失效模式存在很大影响,随着弹体撞击角度的增大,靶体主要失效模式由剪切破坏逐渐过渡到撕裂破坏,靶体的撕裂程度不断加剧;弹体初始撞击角度和速度对其在撞击过程中的弹道姿态存在影响,在弹道极限速度附近表现尤为显著.%A simulation model was established using finite element software ABAQUS,and the numerical simulations of 38CrSi steel projectile impacting 2A12-T4 aluminum alloy plates were conducted, then the influences of impact angles of projectile on the failure characteristics of target and ballistic attitude of projectile were analyzed.Based on numerical simulation and experimental results,the failure characteristics of the target were analyzed,the change laws of the dominant failure modes under different impact conditions,as well as the influences on the impact resistance of target because of that were established.The results show that with the increases of impact angles the ballistic limit velocity decreases,and then increases,and the ballistic limit reaches the minimum when the impact angle is about 15 degrees. In addition,the impact angle ofprojectile impacting greatly influences the failure mode of target,with the projectile angle increases,the dominant failure mode of target changes from shearing to tearing,and also increasing the degree of tearing the target.The initial impact angle and velocity of projectile have great influences on the trajectory attitude of the projectile during the impacts,especially in the vicinity of the ballistic limit velocity.【期刊名称】《中国机械工程》【年(卷),期】2018(029)009【总页数】6页(P1050-1054,1062)【关键词】撞击;2A12-T4铝合金板;平头弹体;失效模式【作者】胡静;邓云飞;崔亚男;张银波【作者单位】中国民航大学航空工程学院,天津,300300;中国民航大学航空工程学院,天津,300300;中国民航大学航空工程学院,天津,300300;中国民航大学航空工程学院,天津,300300【正文语种】中文【中图分类】O385;O3470 引言弹靶撞击属于经典的冲击动力学问题，撞击结果受到多种因素的影响，如弹靶材料力学性能、靶体结构、弹体几何形状、弹体撞击角度与速度等。

两级反射线性菲涅尔中高温集热系统热性能_吕明新

图 3 两级反射式线性菲涅尔集热系统热阻网络图 Fig． 3 Thermal resistance model of tw ostage linear Fresnel reflector concentrator
1. 2
传热过程数学模型
根据两级反射式线性菲涅尔太阳能集热器物理模型图 2 和热网络图 3 ，集热器玻璃盖板、金属吸热
第2 期
吕明新，等：两级反射线性菲涅尔中高温集热系统热性能
107
K ； T o —传热工质出口温度， K。度，通过上面的分析可得到反射式菲涅尔集热器的有用功 q u 和集热效率 η，分别为热损失 q loss 、 q loss = q C ， ga + q R， gs ， q u = mc p （ To － Ti ）， η= qu mc p （ To － Ti ） = 。 Ib D m Ib D m （ 5）（ 6）（ 7）
但集热效率不高。意大利的行了理论分析， GRENA R 采用硝酸盐作为传热工质，导致设备复
［8 ］杂并且影响系统的集热过程。印度的 SINGH P 等人推算了太阳直射时的 LFR 镜场设计公式，但该［9 ］优化布置理论在太阳斜射时并不通用。西班牙
［7 ］
3961 （ 2013 ） 02010506 文章编号： 1672-
两级反射线性菲涅尔中高温集热系统热性能
1， 2 1 1 1 1* 吕明新，宋固，董震，魏露露，赖艳华
（ 1．山东大学能源与动力工程学院，山东济南 250061 ； 2．天津大学热能研究所，天津 300072 ）
的 ABBAS R 等人采用不同优化方法对圆形－圆柱型和抛物线－圆柱型镜场的布置进行了研究，但仅考虑了镜面宽度的影响

Influences of mesh density and transformation behavior on the result quality of numerical calculatio

Inﬂuences of mesh density and transformation behavior on the result quality of numerical calculation of welding induced distortionC.Heinze a ,⇑,C.Schwenk a ,b ,M.Rethmeier a ,baFederal Institute for Materials Research and Testing,Division 5.5‘‘Safety of Joined Components’’,Unter den Eichen 87,12205Berlin,Germany b Fraunhofer-Institute for Production Systems and Design Technology IPK,Joining and Coating Technology,Pascalstraße 8–9,10587Berlin,Germanya r t i c l e i n f o Article history:Received 7March 2011Received in revised form 28April 2011Accepted 3May 2011Available online xxxx Keywords:Welding simulation Gas metal arc welding Welding-induced distortion Mesh analysis CCT sensitivitya b s t r a c tWelding simulation is a powerful,cost-efﬁcient tool to predict welding induced distortion.Nevertheless,effects on calculation result quality are often unknown,thus,sensitivity anal-yses should be performed to evaluate the inﬂuences of certain parameters on distortiondevelopment.In the present paper,a single-layer gas metal arc (GMA)weld of 5mm thick structuralsteel S355J2+N is experimentally and numerically investigated.Subsequent to welding,the numerical modeling begins with a mesh analysis based on modal analyses.Hereby,the inﬂuence of different coarsening methods and element edge length (EEL)in weldingdirection on the deformation behavior or the stiffness of the discrete geometry is the focusof the analysis.Secondly,phase transformations in structural steels such as S355J2+N aredecisive for ﬁnal product properties.The sensitivity of welding-induced distortion is exam-ined regarding different continuous cooling transformation (CCT)diagrams for S355J2+N.The present investigations deal with different relevant inﬂuences on numerical calcula-tion of welding-induced distortion.The quality and quantity of these effects are clariﬁedbased on the experimental and numerical set-up employed.Consequently,prediction ofwelding-induced distortion is possible and potential for pre-production optimization ispresent.Ó2011Elsevier B.V.All rights reserved.1.Introduction and motivationWelding-induced distortion arises from localized heating and subsequent non-uniform cooling during welding.Therefore,complex strains occur in the weld and adjacent regions producing stresses,which cause deformation of the welded compo-nent as Masubuchi (1970)described.Thus,any welding process is able to result in a certain distortion of the fabricated prod-uct.Radaj (1992)showed that the qualitative and quantitative evolution of distortion depends in general on the geometry of the joined components,the material,phase transformation,the welding process,the internal constraints of the structure being welded,and the external structural restraints of ﬁxtures used in welding operation.Because welding induced distortion directly affects the product quality of the joined components it is necessary to mit-igate distortion to meet product requirements.Mitigation techniques such as speciﬁc weld preparation,optimized welding sequencing,pre-bending,heat sinking,thermal straightening,thermal tensioning could be applied.Guirao et al.(2010)used an electron beam mock-up to show the signiﬁcant inﬂuence of a new welding sequence on distortion.Zeng et al.(2010)investigated welding of an aluminum cylinder concluding that welding sequence and weld length are decisive for the 1569-190X/$-see front matter Ó2011Elsevier B.V.All rights reserved.doi:10.1016/j.simpat.2011.05.001⇑Corresponding author.Tel.:+493081043893;fax:+493081041557.E-mail address:christoph.heinze@bam.de (C.Heinze).1848 C.Heinze et al./Simulation Modelling Practice and Theory19(2011)1847–1859corresponding welding-induced distortion and residual stresses.Adak and Mandal(2010)experimentally and numerically investigated the inﬂuence of heat sinking on deﬂection resulting in a model suitable for parameter optimization and distor-tion prediction.Deo and Michaleris(2003)have shown that thermal tensioning is applicable to reduce buckling distortion, but as a result angular distortions became evident.Subsequently,the angular distortion was mitigated using mechanical restraints.At this point,the numerical simulation of welding-induced distortion represents a useful tool because it enables predic-tion of distortion,which leads to a prior description of distortion development and allows well-directed optimization of welding-induced distortion evolution in practice.Over the past30years,theﬁnite-element method has been used in an at-tempt to predict distortion due to welding.Deng and Murakawa(2008)provide an example of numerical simulation of weld-ing-induced distortion regarding thin steel plates.Publications with respect to structural steel GMA butt-welds with plate thicknesses of about5mm or larger are rare in literature.Mollicone et al.(2008)investigated procedural inﬂuences such as tack welds,support conditions and clamping on 3–8mm butt welds.They state that tack welding had just little effect on welding-induced distortion development related to the applied conﬁguration.Furthermore,Wang et al.(2008)analyzed carbon steel in thickness ranges of3.2–4.5mm.The experimental and calculated results show good agreement but the experimental values are always more or less larger than the calculated.Wang et al.mention measurement error and meshing as the reasons for the differences.Meshing is a critical issue within the preprocessing of numerical simulations because its inﬂuence on deformation development due to welding. Tri-linear quadratic elements are usually preferred in analysis of problems in plasticity because they perform better than displacement based linear tetrahedrons as stated by Lindgren(2006).Schenk et al.(2009)experimentally and numerically investigated1mm thick DP600GMAW overlap joint based on modal analyses.It is shown that lateral mesh coarsening in less thermally and mechanically stressed zones,which is often used in numerical welding simulation due to decreased num-ber of nodes and elements resulting in savings of computing time,is actually not preferable with respect to acceptable re-sults of calculated bending distortion.In the case of the present5mm thick butt-weld model,the inﬂuence of the meshing on bending distortion is studied based on three mesh variations considering different coarsening strategies.Additionally, three different element edge lengths for one mesh are investigated on their effect on the bending behavior of the mesh.The interaction between welding-induced distortion and residual stress is described in different basic literature,see,e.g., Radaj(1992)or Feng(2005).When the yield strength of the present material or microstructural constituent is reached irre-versible deformation occurs.The formation of weld microstructures can be described by continuous cooling transformation (CCT)diagrams.Consequently,both residual stress and distortion evolution depend on the CCT behavior.Caron et al.(2010) have investigated the inﬂuence of CCT diagram variations on welding-induced residual stresses and found stress deviations up to90MPa considering CCT diagrams for a S355J2+N.For the structural steel S355J2+N the speciﬁcation of the chemical composition is given in a wide tolerable range,which implies a certain tolerated transformation behavior and mechanical properties resulting from different chemical compositions within the mentioned range.The inﬂuence of compositional dif-ferences on the CCT diagram and,ﬁnally,on the evolution of welding-induced distortion is numerically studied based on four CCT diagrams valid for the steel grade S355J2+N.Hereby,a CCT diagram is taken from the SYSWELD material database for S355J2,two calculated(software JMatProÒand EWIÒVirtual Joining Portal)and an experimentally determined CCT diagram are also included in the investigations.The EWI calculations are based on the publications of Bhadeshia(1982)and Ion et al. (1984).The present paper deals with two aspects,which show considerable inﬂuences on the numerical calculation of welding-induced distortion.The investigated effects are quantiﬁed for a certain experimental set-up and conclusions for the general set-up of numerical models for the prediction of distortion are drawn.2.Experimental procedureThe steel used for the welding experiments was S355J2+N(1.0577),a German standardized plain-carbonﬁne-grained construction steel with a minimum yield strength of355MPa.The chemical composition for S355J2plate material,as spec-iﬁed in the German DIN EN10025-2:2004standard,is provided in Table1.A stress-relief heat treatment,consisting of heating to570°C at5K/min,holding at temperature for3.5h,and furnace cooling to ambient temperature,was applied to the tack-welded plate material before welding to reduce any pre-existing residual stresses.The individual plate dimensions for the welding experiments were300mm length,100mm width,and5mm thickness containing a60°V-groove with seam edges milled.A single-pass complete-penetration gas metal arc weld was conductedTable1Nominal and measured chemical composition of S355J2+N plate material according to DIN EN10025-2:2004,values in wt.%.Nominal chemical compositionC Si Mn P S60.2360.661.760.03560.035Measured chemical compositionC Si Mn P S Fe0.140.200.670.0080.012Balancewelds;stochastic pattern for optical distortion measurement shown;plate dimensions:with G3Si1ﬁller metal wire of1.2mm diameter,in accordance with DIN EN ISO14341,using a shielding gas mixture of 82%Ar and18%CO2at aﬂow rate of18l/min,in accordance with DIN EN ISO14175.Welding conditions consisted of 261A welding current,30.4V average arc voltage,8.5m/min wire feed rate,and0.4m/min travel speed.This resulted in an approximate net heat input of1kJ/mm for the considered GMAW process.Type-K thermocouple wires with a diameter of0.5mm were used to acquire the temperature at positions on both the top and bottom of the welded plate directly adja-cent to the weld seam.The experimental conﬁguration,Fig.1,provided a force-free support of the plate,permitting free shrinkage during the welding process and subsequent cooling.Additionally,a ceramic weld backing was used for all con-ducted weld experiments.The welding-induced distortion was experimentally investigated using a direct image correlation system during the whole welding process including the initial state of the welded plate,the behavior during welding,and the cooling process down to30°C.The distortion evolution was investigated on one half of the plate.The inﬂuence of the pattern consisting of titanium dioxide(white layer)and iron oxide(black spots)on the welding process or weld seam quality is unclear,thus,a zone adjacent to the joint preparation was not provided with a pattern.Furthermore,welding results in an inevitable dete-rioration of the stochastic pattern close to the weld zone and HAZ,respectively,due to color changes and burn-off.During welding process,the arc causes overexposure of the digital cameras leading to a data loss in the corresponding areas.As a consequence,a matt black steel cover was attached to the torch limiting overexposure during welding.The experimental determined residual stress state,the numerical simulation of the residual stress evolution and a sen-sitivity analysis on the inﬂuence of CCT behavior on the residual stress state was evaluated in Caron et al.(2010)related to the material and experimental procedure described in this paper.3.Experimental resultsFig.2depicts the experimental weld macro section with the weld pool area outlined,weld metal microstructure near the fusion line,and the heat affected zone(HAZ)microstructure from a location that experienced a peak temperature of1159°C and a t8/5time of30.0s,where t8/5is the cooling time from800°C to500°C.Table2Summary of individual parameters for measured thermal cycles.Measurement Location Distance from weldcenterline(mm)Peaktemperature(°C)t8/5coolingtime(s)Top of plate8.495332C.Heinze et al./Simulation Modelling Practice and Theory19(2011)1847–18591851The weld metal microstructure consists mainly of Widmanstätten ferrite with aligned second phase(Fig.2b).The HAZ microstructure shown in Fig.2c consists of a mixture of grain boundary ferrite,polygonal ferrite,Widmanstätten ferrite withAdditionally,the element edge length (EEL)in welding direction (WD)was analyzed by three different conﬁgurations for the mesh type 3.Hereby,the EEL in WD or z -direction,referring to the coordinate system in Fig.7,was 1mm,2mm,and 3mm.The modal analyses used the PCG Lanczos method to extract a deﬁned number of 5modes.A force-free support was as-sured by idealized clamping of the specimen using elastic constraints of 1000N/mm on three nodes indicated in Fig.7.The subsequent numerical simulation calculations of temperature ﬁeld and mechanics in this study were performed with the commercial ﬁnite element software SYSWELD Òv2009on a standard PC with a Linux operating system.The most impor-tant simpliﬁcations and assumptions of the simulation are:Temperature dependent,homogeneous,and isotropic (except thermal conductivity in welding direction,factor 10applied)material properties with consideration of phase transformations.A solidus temperature of 1440°C for validation of the weld seam geometry.No consideration of preceding process steps,the specimen is assumed to be geometrically ideal and totally stress free,the weld reinforcement on the top and bottom side are considered.Phenomenological temperature ﬁeld calibration using double-ellipsoid Goldak and 3D-conical Gauss heat sources with time independent volumetric heat ﬂux density and no consideration of weld pool convection.Uniﬁed heat transfer on all outer surfaces with temperature dependent radiative losses according to Stefan–Boltzmann,a constant emission coefﬁcient of e =0.8,constant convective losses of 4W/mm 2,and an ambient temperature of 20°C. Idealized clamping of the specimen using elastic constraints of 1000N/mm for a force-free support.Elastic–plastic material behavior considering isotropic hardening.4.1.Thermal analysisFor the thermal analysis,the experimentally determined data were used to calibrate the heat source of the simula-tion.Two aspects were considered in the temperature ﬁeld adjustment.First,the cross-section geometry of the simu-lated weld pool was correlated with both the size and shape of the experimental macrosection of the weld seam.Second,the corresponding temperature cycles in the HAZ were correlated with the experimental measurements,with emphasis given to peak temperature and cooling time.With respect to the sensitivity of distortion on CCT behavior,each simulation was performed with an identically calibrated temperature ﬁeld.Subsequently,the inﬂuence of different transformation behavior on the evolution of welding induced distortion is numerically studied based on four CCT dia-grams valid for the steel grade S355J2+N.Hereby,a CCT diagram is taken from the SYSWELD Òmaterial database for S355J2,two calculated (software JMatPro Òand EWI ÒVirtual Joining Portal)and an experimentally determined CCT dia-gram are also included in the investigations.The CCT diagrams used for the analysis are described in Heinze et al.(in press).8.Thermophysical input data for S355J2+N;(a)phase speciﬁc thermal conductivity and thermal strain;(b)speciﬁc heat capacity and density;source: SYSWELD material database version2009.4.2.Mechanical analysisAvailable in the SYSWELDÒsoftware is the ability to integrate the effect of metallurgical phase transformations in weld-ing simulations.A thermal–metallurgical calculation isﬁrst completed using the thermal properties of the material,the cal-culated temperatureﬁeld derived and validated from the welding experiments,and the CCT behavior formulated mathematically.The thermal–metallurgical calculation data is then used as an input to the mechanical calculation,which determines stresses and strains according to the transient and spatial distribution of the previously calculated temperatures in the model.It is noted that this one-way coupling,also referred to as‘‘weak coupling’’,does not account for the effect of stress on phase transformation behavior.Furthermore,there is no interaction between the latent heat generated by solid state phase transformations and the calculated temperatureﬁeld.To perform accurate and detailedﬁnite element simulations,the thermal and mechanical properties of the material must be known at high temperatures.One of the advantages in selecting the S355J2+N alloy was the availability of complete mate-rial properties in the SYSWELDÒdatabase(Version2009),including metallurgical phase transformation temperatures,met-allurgical model parameters,transformation plasticity,thermophysical,and thermomechanical properties.Fig.8exhibits the corresponding thermophysical input data for S355J2+N.The thermomechanical properties are displayed in Fig.9.The phase transformations were calculated using the models based on Leblond and Devaux(1984),Leblond(1986,1989),and Koistinen and Marburger(1959).5.Numerical simulation resultsFirst,the calculated eigenfrequencies of the modal analysis are presented in Tables3and4.Regarding the different mesh types,Table3gives an overview of eigenfrequencies corresponding to different eigenmodes.1854 C.Heinze et al./Simulation Modelling Practice and Theory19(2011)1847–1859Table3Calculated eigenfrequencies for the analyzed meshes(Fig.6),EEL in WD is2mm.Eigenmode Eigenfrequencies(sÀ1)Type1Type2Type31st torsion6767671st bending1781771772nd torsion3203193182nd bending4454344363rd torsion586555567 Table4Fig.12.Validation of temperatureﬁeld:thermal cycles at top of the plate.Table5Calculated phase percentages for each CCT diagram,referring to a node with a peak temperature of1200°C andt8/5=25s.CCT diagram Phase(wt.%)Ferrite Bainite MartensiteSYSWELD0946Gleeble6904JMatPro53758EWI10000 For a better understanding of the effect of differences in calculated eigenfrequencies(Table3),Fig.10exhibits the tran-sient displacement in the thickness direction or bending,respectively,of the investigated mesh types.Hereby,the same tem-peratureﬁeld,see Figs.12and13,was applied for all three calculations.In the following,eigenfrequencies representing the inﬂuence of different element edge lengths on welding-induced dis-tortion are shown for mesh type3,Table4.Additionally to Table4,Fig.11clariﬁes how the determined differences in eigenfrequencies affect the calculated welding-induced distortion depending on EEL.The validation of the temperatureﬁeld is presented in Figs.12and13.The former shows both the experimental and the numerically calculated thermal cycles for two positions at the top of the plate.The latter exhibits the comparison for exper-iment and simulation related to the weld pool geometry.The validation results in a good agreement of weld pool geometry and thermal cycles considering the comparison of experiment andﬁnite element simulation.Table5depicts the resulting microstructural constituents of the validated temperatureﬁeld depending on the corre-sponding CCT diagram.The evaluation was performed on a node referring to a peak temperature of about1200°C and a cool-ing time t8/5of25s,corresponding to Fig.2c.displacement in thickness direction(bending)depending on CCT diagram used,Furthermore,the transient displacement u y is shown for the investigated CCT diagrams,see Fig.14.Hereby,the mesh type 3with an EEL of2mm was used instead of1mm due to the higher computation times occurred.Additionally,theﬁnal state of the whole plate after welding and cooling down to room temperature is exhibited in Fig.15.6.DiscussionFirst,modal analyses were performed resulting in lowest eigenfrequencies regarding eigenmodes2nd bending and3rd torsion for mesh type2,Table3.But the calculated displacements in Fig.10show a deviating behavior in favoring mesh type 3instead of type2.Thus,the transferability of the modal analysis results is not clear when comparing different mesh types. Nevertheless,the results of the modal analyses performed with mesh type3considering different EEL describe a clear cor-relation.In detail,the mesh with1mm EEL shows the lowest eigenfrequency563sÀ1for eigenmode3rd torsion.An increase in EEL results in higher eigenfrequencies for2mm EEL(567sÀ1)and for3mm EEL(570sÀ1).The corresponding difference in ﬁnal distortion between1mm and3mm EEL is about1mm,whereby,the computation time is approx.2.5times higher for the mesh with1mm EEL.Consequently,the modal analysis can give additional information about an appropriate meshing regarding the suitability for numerically calculated distortions,especially bending,but a mechanical analysis is necessary to assure the results of a model analysis.The obtained result for mesh type1,see Fig.10,is consistent with theﬁndings of Schenk et al.(2009)who do not recommend a mesh coarsening towards the plate edges.The various CCT diagrams used in the present welding simulation result in certain phase fractions after welding,Table5. The JMatProÒand the EWIÒCCT diagrams are based on calculations using the chemical composition for the test material (S355J2+N)given in Table1.The resulting differences are signiﬁcant.The calculation with the CCT diagram provided by JMatProÒleads to a martensite fraction of58wt.%,a bainite fraction of37wt.%,and a ferrite fraction of5wt.%for a peak temperature of1200°C and a cooling time t8/5of25s.For the same conditions the EWIÒcalculation gives no martensite and bainite,but100wt.%ferrite.The GleebleÒCCT diagram was obtained by combining information of hardness measure-ments,dilatometry,metallography,and literature data for S355J2+N,see Caron et al.(2010).It is obvious that there are sim-ilarities with the SYSWELDÒCCT diagram,which is based on experimental data published in Seyffarth et al.(1992).Fig.16shows that large fractions of martensite and bainite result in a lower deformability of the plate based on the JMat-ProÒCCT diagram.A lower martensite fraction occurs in the cases SYSWELDÒand GleebleÒ,thus,the deformability rises and theﬁnal dis-tortion increases up to3.5mm(GleebleÒ)at the point of evaluation.With respect to the experimentally determined micro-structure,Fig.2b and c,the EWIÒprediction shows the best agreement.However,that fact is not expressed in the calculated distortion compared to the experimental data,Fig.16.The reasons is the high transformation temperatures of the EWIÒ,e.g.transient ferrite fraction development indicating the temperature of ferriteﬁnish temperature1858 C.Heinze et al./Simulation Modelling Practice and Theory19(2011)1847–1859Since there is still a signiﬁcant deviation between quantitative results of simulation and experiment,several inﬂuences have to be mentioned.First,the experimental weld pool geometry meets the limits of the equivalent Goldak and Gauss heat sources,which results in differences between experimental and calculated weld pool geometries.Furthermore,the simula-tion represents a heat conduction problem neglecting the heat convection in the weld pool,which indeed plays a decisive role in the performed experiments because weld pool length was determined to be about35mm.However,welding-induced distortion is highly sensitive to the weld pool geometry.This effect will be investigated in detail within future research.Sec-ondly,the mesh used in the simulations considering different CCT diagrams represents a compromise between computation time and practicability.In relation to that,theﬁne mesh type3with1mm EEL(175,000nodes and206,000elements)was additionally investigated considering the Gleeble CCT diagram.The resultingﬁnal displacement in y-direction,which refers to the point of evaluation in Fig.10,is about3.9mm representing a value about0.6mm or18%higher than the calculation based on the Sysweld CCT and the mesh with1mm EEL,shown in Fig.11.This result shows ability to optimize welding-in-duced distortion calculations based on mesh and CCT diagram studies.The thermophysical and the thermomechanical material parameters used in the numerical model have an effect on the calculated results as well,especially,when considering a wide range of possible chemical composition for a S355J2+N steel. Finally,the processing technology in terms of tack welding can affect the resulting calculated distortions.In further inves-tigations,the inﬂuence of tack welding on calculation of welding-induced distortion will be clariﬁed.7.ConclusionsIn the present paper,modal analyses and a validated numerical simulation were used to investigate the inﬂuences of mesh density and different CCT behavior on result quality of calculation of welding-induced distortion.The modal analyses show that a coarsening with increasing distance to the weld seam is not preferable for the numerical calculation of distortion.However,coarsening in the thickness direction with increasing distance to the weld centerline has a positive effect on bending behavior of the investigated structure.The usage of modal analyses is possible in case of investi-gating the inﬂuence of different element edge lengths on the deformation behavior of a certain mesh type.But with respect to different mesh strategies mechanical analysis should be performed to assure the results of the modal analysis.Different CCT diagrams for the plain carbon steel S355J2+N were used to investigate the sensitivity of distortion on phase transformation characteristics.A signiﬁcant effect including differences of up to60%was found according to the displace-ment in the thickness direction(y-direction,bending).The authors recommend a thorough study of available CCT data before calculating distortions or residual stresses as well.Transformation plasticity and thermal strain as contributions to the total strain have to be considered for the evaluation of the present behavior in terms of CCT sensitivity of distortion.The combination of the presentﬁndings of modal analysis and CCT diagram studies result in an optimized simulation exhibiting improved welding-induced distortion calculation,whichﬁnally reduced the quantitative deviation between experiment and numerical simulation.AcknowledgmentThe presented work was accomplished within the project IGF15746N‘‘Optimization of distortion and residual stresses during welding of thick-walled components’’of the Arbeitsgemeinschaft industrieller Forschungsvereinigungen‘‘Otto von Guericke’’e.V.(AiF).The authors gratefully acknowledge theﬁnancial support for this research from of the Federal Ministry of Economics and Technology(BMWi)through the‘‘Arbeitsgemeinschaft industrieller Forschungsvereinigungen e.V.’’.Fur-thermore,the authors thank Dr.J.Caron,Prof.S.S.Babu and Prof.J.Lippold from the Ohio State University for their contri-butions to the present paper.References[1]M.Adak,N.R.Mandal,Numerical and experimental study of mitigation of welding distortion,Applied Mathematical Modelling34(2010)146–158.[2]H.Bhadeshia,Thermodynamic analysis of isothermal transformation diagrams,Metal Science16(1982)159–165.[3]J.Caron,C.Heinze,C.Schwenk,M.Rethmeier,S.Babu,J.Lippold,Effect of continuous cooling transformation variations on numerical calculation ofwelding-induced residual stresses,Welding Journal89(2010)151–160.[4]D.Deng,H.Murakawa,FEM prediction of buckling distortion induced by welding in thin plate panel structures,Computational Materials Science43(2008)591–607.[5]M.V.Deo,P.Michaleris,Mitigation of welding induced buckling distortion using transient thermal tensioning,Science and Technology of Welding andJoining8(2003)49–54.[6]Z.Feng,Processes and Mechanisms of Welding Residual Stress and Distortion,Woodhead Publishing Ltd.,2005.[7]J.Guirao,E.Rodríguez,A.Bayón,J.Pistono,L.Jones,FEM simulation of a small EB welded mock-up and new sequence proposed to improve theﬁnaldistortions,Fusion Engineering and Design85(2010)181–189.[8]C.Heinze,C.Schwenk,M.Rethmeier,J.Caron,Numerical sensitivity analysis of welding-induced residual stress depending on variations in continuouscooling transformation behavior,Frontiers of Materials Science5(2011)168–178.[9]J.C.Ion,K.E.Easterling,M.F.Ashby,A2nd report on diagrams of microstructure and hardness for heat-affected zones in welds,Acta Metallurgica32(1984)1949–1962.[10]D.P.Koistinen,R.E.Marburger,A general equation prescribing the extent of the austenite–martensite transformation in pure iron–carbon alloys andplain carbon steels,Acta Metallurgica7(1959)50–59.[11]J.-B.Leblond,J.Devaux,A new kinetic model for anisothermal metallurgical transformations in steel including effect of austenite grain size,ActaMetallurgica32(1984)137–146.。

垂直轴风力机尾缘开裂襟翼气动性能及其偏转角调节规律

第51卷第4期2020年4月中南大学学报(自然科学版)Journal of Central South University (Science and Technology)V ol.51No.4Apr.2020垂直轴风力机尾缘开裂襟翼气动性能及其偏转角调节规律张立军，顾嘉伟，朱怀宝，胡阔亮，江奕佳，缪俊杰，王旱祥，刘静(中国石油大学(华东)机电工程学院，山东青岛，266580)摘要：为提高垂直轴风力机的气动性能，提出在小型3叶片垂直轴风力机叶片尾缘加装开裂襟翼的设计方案。

首先，根据CFD 数值模拟和正交设计得到偏转角对风力机气动性能影响最大；然后，进一步分析了叶尖速比分别为1.5和2.5时襟翼偏转角对风力机气动性能的影响和增升机理；最后，提出了襟翼偏转角调节规律。

研究结果表明：襟翼的较优参数组合为长度l =20%c 、偏转角β=10°和布置位置t =90%c 。

当叶尖速比T SR 分别为1.5和2.5时，较小的襟翼偏转角(0°<β<10°)能提升叶片平均切向力系数C Tavg ，其中，襟翼偏转角β=10°时，风力机的风能利用率C P 分别提升了7.7%和4.6%；与原型风力机相比，应用襟翼偏转角调节规律后，风能利用率C P 分别提升12.4%和10.4%。

关键词：垂直轴风力机；开裂襟翼；正交设计；气动性能；调节规律中图分类号：TK83文献标志码：A开放科学(资源服务)标识码(OSID)文章编号：1672-7207（2020）04-0931-13Aerodynamic performance on the trailing edge split flap andregulation law of deflection angle of V AWTZHANG Lijun,GU Jiawei,ZHU Huaibao,HU Kuoliang,JIANG Yijia,MIAO Junjie,WANG Hanxiang,LIU Jing(College of Mechanical and Electronic Engineering,China University of Petroleum,Qingdao 266580,China)Abstract:In order to improve the aerodynamic performance of vertical-axis wind turbine (V AWT),a design scheme for adding a split flap on the trailing edge of the small 3-blade V AWT was proposed.Firstly,by using CFD numerical simulation and orthogonal design method,it was found that the deflection angle had the greatest influence on the aerodynamic performance of wind turbine.Secondly,the influences of the flap deflection angle on the aerodynamic performance of the wind turbine and the increasing mechanism of lift were analyzed when the tip speed ratio was 1.5and 2.5respectively.Finally,the regulation law of the flap deflection angle was proposed.The results show that the optimal length (l )is 20%c ,optimal deflection angle (β)is 10°and optimal arrangement position (t )is 90%c .When tip speed ratio (T SR )is 1.5and 2.5respectively,the smaller fixed deflection angle (0°<β<10°)can increase the average tangential force coefficient of the blade.The output power coefficient (C P )increases by 7.7%and 4.6%respectively when deflection angle is 10°.By using the regulation law of flapDOI:10.11817/j.issn.1672-7207.2020.04.008收稿日期：2019−08−12；修回日期：2019−10−20基金项目(Foundation item)：国家自然科学基金资助项目(51707204）；中央高校基本科研业务专项资助项目(17CX05021)(Project(51707204)supported by the National Natural Science Foundation of China;Project(17CX05021)supported by the Fundamental Research Funds for the Central Universities)通信作者：张立军，博士，教授，从事可再生能源技术和绿色装备制造研究；E-mail:******************.cn第51卷中南大学学报(自然科学版)deflection angle,the output power coefficient increases by12.4%and10.4%respectively compared with that ofthe prototype wind turbine.Key words:vertical-axis wind turbine(V AWT);split flap;orthogonal design;aerodynamic performance; regulation law风力发电机按照主轴相对于地面的安装位置可分为水平轴风力机和垂直轴风力机。

高压天然气管道泄漏扩散 CFD 数值模拟

高压天然气管道泄漏扩散 CFD 数值模拟周伟国;刘东京;滕卯寅【摘要】为了降低天然气管道泄漏对环境造成的危害，采用FLUENT软件对高压天然气管道泄漏后甲烷扩散特性进行数值模拟，分别模拟了稳态及非稳态时甲烷浓度分布及速度分布情况；探究不同管道压力和外界风速对天然气泄漏扩散过程的影响，并通过速度分布图和甲烷浓度分布图分析天然气的扩散特性和区域。

结果表明：管内压力越大，甲烷射流出口速度越大，甲烷扩散区域越大；风速越大，甲烷的偏转角度越大，在空气中扩散得越快。

%With the objective of reducing the damages of pipeline gas leakage to the environment , numerical simulation on gas diffusion feature of high-pressure piping was performed with FLUENT .The methane concentration and velocity profile at the steady and unsteady state were simulated , respectively .The influences of tubing pressure and wind velocity on gas leakage were investiga -ted,and the gas diffusion feature and area of nature gas were analyzed via the velocity profiles and methane concentration profiles . The results show that the bigger the tubing pressure is , the larger the outlet velocity of jet flowis ,and the larger the diffusion area is.The bigger the wind velocity is, the larger the deflection angle is , the faster the gas diffusion rate is .【期刊名称】《管道技术与设备》【年(卷),期】2015(000)005【总页数】4页(P5-8)【关键词】高压管道;天然气;管道泄漏;气体扩散;CFD【作者】周伟国;刘东京;滕卯寅【作者单位】同济大学，上海 200092;同济大学，上海 200092;同济大学，上海200092【正文语种】中文【中图分类】TE973近年来，随着天然气开发和利用的飞速发展，国内己建成天然气输送管道约2万km。

基于生死单元法的双辊铸轧过程热-力耦合数值模拟

基于生死单元法的双辊铸轧过程热力耦合数值模拟黄华贵1,2刘文文1,2 王巍2 杜凤山1,21.国家冷轧板带装备及工艺工程技术研究中心,秦皇岛,0660042.燕山大学,秦皇岛,066004摘要:以二辊ϕ160mm×150mm 立式铝带实验铸轧机为对象,基于M S C .M a r c 商用有限元软件及其二次开发接口,引入纯铝固液两相材料本构模型和界面压力热阻数学模型,建立了双辊铸轧过程热力耦合非线性有限元模型㊂采用生死单元法模拟铝液的连续浇入,解决了辊套和铸轧区铝带材间的连续耦合传热问题㊂通过数值模拟,给出了铸轧速度㊁浇铸温度㊁熔池高度等因素对K I S S 点位置和辊面温度时间历程的影响规律,并对典型工况温度模拟结果进行了实验验证㊂关键词:双辊铸轧;温度场;有限元法;生死单元法;数值模拟中图分类号:T G 233.6;T P 391.9 D O I :10.3969/j.i s s n .1004132X.2015.11.013T h e r m a l ‐m e c h a n i c a l C o u p l e d M o d e l l i n g an dN u m e r i c a l S i m u l a t i o n f o rT w i n ‐r o l l e r C a s t i n g P r o c e s sw i t hT e c h n i qu e o fD e a c t i v a t e a n dR e a c t i v a t eE l e m e n t H u a n g H u a g u i 1,2 L i u W e n w e n 1,2 W a n g W e i 2 D uF e n g s h a n 1,21.N a t i o n a l E n g i n e e r i n g R e s e a r c hC e n t e r f o rE q u i p m e n t a n dT e c h n o l o g y of C o l dS t r i p R o l l i ng ,Q i nh u a n g d a o ,H e b ei ,0660042.Y a n s h a nU n i v e r s i t y ,Q i n h u a n gd a o ,He b e i ,066004A b s t r a c t :A i m i n g a t t h e ϕ160mm×150mm v e r t i c a l t y p ee x pe r i m e n t a l t w i n ‐r o l l e r sc o n t i n u o u s c a s t e r ,a t h e r m a l ‐m e c h a n i c a l c o u p l e dF E M m o d e l of t w i n ‐r o l l e r c a s t i n gpr o c e s sw a s e s t a b l i s h e dw i t h M S C .M a r c a n d i t s ’s e c o n d a r y d e v e l o p m e n t i n t e r f a c eb a s e do n t h e s o l i d ‐l i qu i d t w o p h a s e s c o n s t i t u t i v e m o d e l o f p u r e a l u m i n u ma n d t h e t h e r m a l r e s i s t a n c em o d e l c o n s i d e r i n g t h e c o n t a c t p r e s s u r e .T h e t e c h -n i q u e o f d e a c t i v a t e a n d r e a c t i v a t e e l e m e n tm e t h o dw a s u s e d t o s i m u l a t e t h e c o n t i n u o u s c a s t i n g o f a l u -m i n u m s l i q u i d ,a n d t h e p r o b l e m o f c o u p l e dh e a t t r a n s m i s s i o nb e t w e e nt h ec a s t r o l l s h e l l a n da l u m i -n u ms t r i p i n t h e c a s t r o l l i n g ar e aw a s t h e r e f o r e r e s o l v e d .F r o mt h e s i m u l a t i o n r e s u l t s ,t h e i n f l u e n c e s o f c a s t i n g s p e e d ,c a s t i n g t e m p e r a t u r e ,t h e h e i g h t o f c a s t r o l l i n g ar e a o n t h e p o s i t i o n o fK I S S p o i n t a n d t h e t i m eh i s t o r y o f t e m p e r a t u r e o n t h e r o l l s u r f a c ew e r e p r e s e n t e d .A n t w i n ‐r o l l e r c a s t i n g e x pe r i m e n t w a s c a r r i e do u t ,a n dt h en u m e r i c a l s i m u l a t i o nr e s u l t s a r e i n g o o da g r e e m e n t sw i t ht h ee x pe r i m e n t a l d a t a .K e y wo r d s :t w i n ‐r o l l e r c a s t i n g ;t e m p e r a t u r e f i e l d ;f i n i t ee l e m e n tm e t h o d (F E M );d e a c t i v a t e a n d r e a c t i v a t e e l e m e n tm e t h o d;n u m e r i c a l s i m u l a t i o n 收稿日期:20140630基金项目:国家自然科学基金资助项目(51474189);河北省自然科学基金资助项目(E 2013203377)0 引言双辊薄带铸轧工艺是一种集金属快速凝固和热轧于一体的复合工艺,具有短流程和低能耗等优点,属于冶金及材料研究领域的前沿技术[1]㊂近年来,国内外学者围绕铸轧区金属熔体及带坯与铸轧辊间的换热行为㊁铸轧带材组织性能控制以及铸轧工艺,开展了大量的理论与实验研究工作[2‐7]㊂经过近十年的快速发展和应用实践,该技术已逐渐被应用于铝合金㊁低碳钢以及不锈钢和硅钢等难变形金属带材的工业生产[8]㊂作为双辊铸轧工艺的重要基础,铸轧区内固液相组成及其对轧制力和耦合传热行为的影响一直是国内外学者研究的热点,也是铸轧辊冷却结构的设计和铸轧工艺优化的重要依据㊂数值模拟技术作为铸轧过程仿真的重要手段[9],可实现铸轧过程热力耦合建模和辊体热平衡的动态仿真分析,其核心技术包括:金属熔体固液混合相(或半固态)变形抗力模型的建立㊁铸轧区带坯与铸轧辊表面换热系数的计算㊁熔体连续浇入模型的实现等㊂在实际铸轧生产过程中,铸轧区内金属形态主要由液相㊁固相和固液两相混合体组成,且需要轧制多圈后辊体温度场才会达到平衡状态㊂一般认为,金属熔体具有牛顿流体㊃3051㊃基于生死单元法的双辊铸轧过程热力耦合数值模拟黄华贵刘文文王巍等Copyright ©博看网. All Rights Reserved.的流变性能,固相金属的塑性流变性能目前已有较为成熟的理论模型,而固液两相混合体铸轧变形过程的流变应力曲线则需通过半固态金属的热压缩实验测试获得[10‐11]㊂湛利华等[5,12]在G l e e b l e上开展了铝合金连续铸轧过程流变行为物理模拟研究,并将其成功应用于铸轧工艺热力耦合分析㊂铸轧区金属熔体㊁固相带坯与辊面之间换热行为方面,国内外学者主要采用接触热阻测试实验,得到不同温度㊁接触压力和表面粗糙度等条件下的接触换热系数,并应用于铸轧辊温度场模拟[13‐15]㊂为获得铸轧辊辊体的平衡态温度场,对铸轧辊与带坯进行耦合传热有限元建模时,持续多圈的铸轧过程模拟需要大量的网格作为支持,这给模型求解带来较大困难㊂因此,解决金属熔体连续浇入建模问题,对实现铸轧过程热力耦合和辊体热平衡的动态仿真分析具有重要意义㊂本文以燕山大学二辊ϕ160mm×150mm铸轧机为对象,以铸轧区流变本构模型和接触换热数学模型为基础,通过M S C.M a r c二次开发子程序接口,采用生死单元法建立了纯铝双辊铸轧过程的热力耦合有限元模拟模型,解决了金属熔体的连续浇铸建模问题㊂目前,生死单元法在带钢卷取[16]㊁焊接[17]和工程施工[18]等工艺研究方面已有较多应用㊂1 双辊铸轧热力耦合有限元建模1.1 模型简化二辊ϕ160mm×150mm立式实验铸轧机如图1所示,设计最大轧制力50k N(5t),最大铸轧力矩1200N㊃m,主电机功率为3k W,具有振动铸轧功能[19],以改善铸轧带材的内部质量㊂为便于有限元建模,进行如下假设:①铸轧辊为刚性辊,铝液入口速度和温度恒定,带坯与辊面不发生相对滑动;②铸轧区内熔体㊁铸坯与铸轧辊沿宽度方向传热均匀,轧制力轴向分布均匀,铸轧成形过程简化为平面应变问题;③辊套与辊内冷却水对流换热系数为定值;④铸轧辊与熔体间的换热系数取常数,辊面与带坯间的换热系数与接触压力㊁温度有关㊂为减小计算规模,根据传热和变形的对称性,取二分之一结构进行建模,在M S C.M a r c软件平台上建立纯铝双辊铸轧过程热力耦合仿真模型,如图2所示㊂以铸轧厚度为3mm的铝带产品为例进行建模分析,辊套厚30mm,取铸轧区出口中心为坐标原点o,高度方向为y轴,辊面A点(图2)为验证实验温度检测点㊂图2中,y a为溶1.压下装置2.平衡弹簧3.铸轧辊4.铸轧带材5.浇铸系统6.铸轧辊7.振动机构图1 二辊铸轧机结构简图池液面高度,y k为单元杀死”的临界坐标,h2为辊套和冷却水之间的对流换热系数㊂图2 铸轧过程热力耦合模型1.2 传热边界条件(1)铸轧带坯与辊套之间接触换热边界表达为q f=h1(t Z P-t G TW)(1)其中,q f为轧辊与带坯间的热流密度;t Z P㊁t G TW分别为带坯表面温度和辊套表面温度;h1为带坯与辊套之间的接触换热系数,与界面接触压力有关,文献[14]通过界面热阻测试实验,给出了其回归公式:h1R ak m=2.35×10-3(p H)0.93+1.29×10-3(2)式中,R a为均方根表面粗糙度,μm;k m为调和平均热导率,W/(m㊃K);p为界面压力,M P a;H为较软接触副材料的微观硬度,M P a㊂(2)辊套与内侧冷却水间的对流换热边界表达为q w=h2(t G T N-t S)(3)式中,q w为辊套与冷却水之间的热流密度;t G T N和t S为辊套内表面温度和冷却水温度㊂模型中辊体㊁冷却水初始温度和环境温度均为30℃㊂h2取14k W/(m2㊃K)㊂(3)辊套与空气间的对流换热和辐射换热等价为综合换热系数,取25W/(m2㊃K)㊂(4)铸轧带坯中心对称面取绝热边界条件㊂㊃4051㊃中国机械工程第26卷第11期2015年6月上半月Copyright©博看网. All Rights Reserved.1.3 材料本构模型工业纯铝的凝固温度区间为614~659℃,凝固潜热为3.9414J /g,其热物性参数如表1所示[20]㊂表1 纯铝热物性参数温度t (℃)227327427527627660(固)660(液)670710质量热容(J /(k g㊃K ))99710401080114912311264117611771177热导率(W /(m ㊃K ))23623122521821020890.991.493 考虑固液两相混合体和固相纯铝的热变形流变特性差异,引用文献[12]中纯铝的材料本构模型:σ=2.37×108ε㊃0.8733e x p (-0.019(t +273))t ≥600℃3.71×107ε㊃0.6707e x p(-0.017(t +273))500℃<t <600℃9.161×103s i n h -1ε㊃0.043e x p (-0.0069(t +273))300℃<t ≤500℃2.356×103ε㊃0.5345e x p (-0.0041(t +273))t ≤ìîíïïïïïïïïïï300℃(4)式中,t 为变形温度,℃;σ为铝的流变应力,M P a ;ε㊃为应变速率,s-1㊂材料本构模型通过M S C .M a r c 二次开发接口子程序u r p f l o .f 嵌入有限元模型[21]㊂铸轧辊材料选用42C r M o ,相关热物性参数直接从M S C .M a r c 材料数据库中读取㊂1.4 生死单元法及连续浇铸建模由于铸轧辊表面与铸坯间的传热具有间断周期性特点,生产实践表明,铸轧辊达到热平衡至少需要工作10圈以上,铸轧带材数十米㊂若采用传统带辊耦合传热建模方法,则入口处需设置数量巨大的金属熔体”网格,给模型求解带来困难㊂如图2所示,本文利用M S C .M a r c 中的生死单元法(二次开发接口子程序u a c t i v e .f ),在铸轧入口浇铸区上方预先划分足够数量的网格,并将节点坐标y 大于y a (即熔池液面高度)的单元全部杀死”㊂随着铸轧辊的转动,铸轧区内金属网格会将死单元”带入铸轧区,当其节点坐标y 小于y a 时,通过子程序将新进入铸轧区的死单元”重新激活”㊂同样,为避免铸轧出口铝带长度过大而导致模型网格数量过多,在出口方向以y k 作为单元杀死”的临界坐标,单元节点坐标y 小于y k 时将被杀死”㊂因此,整个模拟过程中仅节点坐标在y k 和y a 之间的单元保持激活”状态,参与模型求解的单元数量大大减少,解决了连续浇铸模拟和快速仿真问题㊂2 模拟结果分析2.1 铝带单元激活”与杀死”处理图3是铸轧速度为2.4m /m i n 时,完成第一圈轧制后的辊面温度变化云图㊂从图3中可以看出,金属熔体入口液面始终保持不变,当铸轧出口带坯延伸至y k 点后,单元即被杀死”㊂在有限元法中,对于被杀死”的单元只是将其单元刚度矩阵乘上一个较小的参数(如1.0×10-6),并非将其从实际模型中删除㊂由于被杀死”单元的单元载荷㊁质量和热边界条件等其他同类参数均为0,故可大大提高模型求解效率㊂铝液入口单元温度初值则可在模型中设置,不受单元生死操作的影响㊂(a )时间τ=0(b )时间τ=4s(c )时间τ=12s(d )时间τ=18s图3 铸轧过程辊面温度分布变化模拟获得了铸轧区稳态温度场(图4a)和带坯等效应力分布(图4b ),从图4中可以看出铸轧区内液相区㊁固液两相区㊁固相区和K I S S 点高度,以及铝带等效应力分布㊂结合铸轧辊与铝带间接触压力模拟结果(图5)和式(2),可计算出铸轧区内铝带和铸轧辊间的接触换热系数分布曲线(图5),接触压力从入口到出口先增大后减小,接触换热系数与接触压力的变化趋势相一致㊂2.2 铸轧速度对K I S S 点高度和出口温度的影响取熔池液面高度y a =30mm ,铸轧速度v 分别为1.6m /m i n ㊁2.4m /m i n ㊁3.2m /m i n,浇铸温度t 0=700℃,K I S S 点高度和铝带出口温度变化㊃5051㊃基于生死单元法的双辊铸轧过程热力耦合数值模拟黄华贵刘文文王巍等Copyright ©博看网. All Rights Reserved.(a)温度场(b)等效应力图4 稳态铸轧区(τ=150s)图5 铝带与铸轧辊间接触压力和接触换热系数规律如图6所示㊂从图6中可以看出,当v =3.2m /m i n时,铝带出口温度处于固液两相区,会发生漏钢事故;当v =1.6m /m i n 时,出口温度较低,K I S S 点高度过高,易造成卡壳事故㊂模拟结果表明,当v =2.4m /m i n 时,K I S S 点高度由开始的12.74mm 随时间逐渐降低并稳定于8mm (图6b),铸轧过程稳定㊂(a)出口温度(b )K I S S 点高度(v =2.4m /m i n)图6 铸轧速度对K I S S 点高度和铝带出口温度的影响2.3 浇铸温度对K I S S 点高度和出口温度的影响取熔池液面高度y a =30mm ,铸轧速度v =2.4m /m i n ,浇铸温度t 0分别为680℃㊁700℃㊁720℃,K I S S 点高度和铝带出口温度的变化规律如图7所示㊂从图7中可以看出,三种工况下K I S S 点高度随铸轧圈数的变化趋势基本相似,浇铸温度每降低20℃,铝带出口温度约降低10℃(图7a),相同时刻K I S S 点高度升高约1m m (图7b )㊂(a)出口温度(b )K I S S 点高度图7 浇铸温度对K I S S 点高度和出口温度的影响2.4 熔池高度对K I S S 点高度和出口温度的影响取浇铸温度t 0=700℃,铸轧速度v =2.4m /m i n ,熔池高度y a 分别为20mm ㊁30mm 和40mm ,K I S S 点高度和铝带出口温度变化规律如图8所示㊂当熔池高度为20mm 时,铝带出口温度超过625℃,会出现漏钢事故(图8a );当熔池高度由30mm 升高至40mm 时,稳态K I S S 点高度由8mm 提高至19.3mm ,铝带出口温度由570℃降低至498℃㊂2.5 辊套热平衡分析及实验验证根据上述模拟结果,确定适于本实验铸轧机的合理工艺参数为:熔池高度30mm ㊁浇铸温度700℃㊁铸轧速度2.4m /m i n ,并以以上参数为基础进行辊套热平衡分析,模拟获得的辊面及辊套径向温度随时间变化曲线如图9所示,图中,h '为测点距辊面的距离㊂铸轧过程辊套内各点温度随时间呈周期性变化,距辊面越近,温度波动周期性越明显(图9b)㊂轧制9圈后辊套温度变化达到稳定状态,辊面最㊃6051㊃中国机械工程第26卷第11期2015年6月上半月Copyright ©博看网. All Rights Reserved.(a)出口温度(b )K I S S 点高度图8 熔池高度对K I S S点高度和铝带出口温度的影响(a)辊面温度1.h '=5mm 2.h '=10mm 3.h '=15mm4.h '=20mm 5.h '=25mm 6.h '=30mm (b)辊套径向温度图9 辊套热平衡模拟结果高温度为298℃,最低温度为125℃(图9a ),辊套内壁温度为45℃(图9b)㊂为验证模型精度,利用R a yt e k 红外测温仪对相同工况下(图10a )辊面温度进行采集㊂由于工作过程轧辊处于转动状态,无法对辊面进行定点测温,本文通过事先在辊面中心A 点(图2)对应的辊身端部贴签做标识,分别连续铸轧1圈㊁2圈㊁3圈后停机对A 点进行温度测试,结果表明,实测值与有限元模拟结果基本吻合(图10b)㊂(a)实验现场(b)辊面温度对比图10 温度模拟结果验证3 结束语本文较为系统地分析了双辊铸轧过程热力耦合有限元建模的核心数学模型,并采用生死单元方法,解决了金属熔体连续浇铸建模问题,为铸轧辊热平衡分析和工艺优化提供了新途径㊂以二辊ϕ160mm×150mm 立式实验铸轧机为对象,模拟分析了铸轧速度㊁熔池高度㊁浇铸温度对铸轧区K I S S 点高度和带材出口温度的影响规律,给出了合理的铸轧工艺规程及相应工况下的辊套热平衡演变过程,并通过铸轧实验对温度模拟结果进行了验证㊂参考文献:[1] 赵红阳,胡林,李娜.双辊薄带铸轧技术的进展及热点问题评述[J ].鞍钢技术,2007(6):1‐5.Z h a o H o n g y a n g ,H uL i n ,L iN a .D e v e l o p m e n to f T w o ‐h i g hT h i nS t r i p C a s t i n g a n dR o l l i n g T e c h n o l o -g y a n dK e y P o i n tR e v i e w [J ].A n g a n g T e c h n o l o g y ,2007(6):1‐5.[2] Z h a oH u ,L i P e i j i e ,H eL i a n g j u .C o u p l e dA n a l ys i s o fT e m p e r a t u r e a n dF l o w D u r i n g T w i n ‐r o l lC a s t i n g o fM a g n e s i u m A l l o y S t r i p [J ].J o u r n a l o fM a t e r i a l s P r o c e s s i n g T e c h n o l o g y,2011,211(6):1197‐1202.[3] W a n g B o ,Z h a n g J i e y u ,L iX i a n g m e i ,e t a l .S i m u -l a t i o no fS o l i d i f i c a t i o n M i c r o s t r u c t u r e i n T w i n ‐r o l l C a s t i n g S t r i p [J ].C o m pu t a t i o n a lM a t e r i a l sS c i e n c e ,2010,49(1):S 135‐S 139.[4] 陈守东,陈敬超.双辊薄带连铸凝固组织模拟微观模型的验证[J ].材料热处理学报,2012,33(7):㊃7051㊃基于生死单元法的双辊铸轧过程热力耦合数值模拟黄华贵刘文文王巍等Copyright ©博看网. 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[19] 李尧.双辊薄带振动铸轧过程仿真模拟及实验研究[D].秦皇岛:燕山大学,2011. [20] 王祝堂.铝合金及其加工手册[M].3版.长沙:中南大学出版社,2005.[21] 陈火红,尹伟奇,薛小香.M S C.M a r c二次开发指南[M].北京:科学出版社,2004.(编辑袁兴玲)作者简介:黄华贵,男,1978年生㊂燕山大学机械工程学院教授㊁博士㊂主要研究方向为材料加工工艺及装备㊂获国家发明专利6项,发表论文30余篇㊂刘文文,男,1990年生㊂燕山大学机械工程学院硕士研究生㊂王巍,女,1978年生㊂燕山大学机械工程学院讲师㊂杜凤山,男,1960年生㊂燕山大学机械工程学院教授㊁博士研究生导师㊂㊃8051㊃中国机械工程第26卷第11期2015年6月上半月Copyright©博看网. All Rights Reserved.。

论文2--纸浆模塑承载结构单元屈曲临界荷载数值分析1

纸浆模塑制品结构单元承载能力与缓冲性能数值分析*计宏伟1，王和敏2，陈金龙2(1. 天津商业大学包装工程系，天津，天津300134；2. 天津大学力学系，天津，天津300072)摘要：纸浆模塑包装制品的承载与缓冲功能是通过制品中各结构单元来实现的，结构单元的形态和几何尺寸直接影响整个制品的承载能力和缓冲性能。

应用ANSYS有限元软件分析了纸浆模塑结构单元在压缩载荷作用下的非线性变形特性和屈曲行为，给出了结构单元的临界载荷，由此确定了结构单元的临界承载力。

与此同时，计算分析了结构单元厚度变化对承载能力和缓冲性能的影响。

结果显示，随着结构单元壁厚的增加其承载能力也随之增加，但缓冲效果变弱，因此在纸浆模塑缓冲结构设计时必须平衡两者，针对不同包装要求调整纸浆模塑厚度，设计出满足不同承载要求且缓冲性能优良的包装结构。

关键词：纸浆模塑；结构单元；压缩屈曲；有限元中图分类号：TB482.2 文献标识码：ANUMERICAL ANALYSIS FOR LOAD-BEARING CAPACITY AND CUSHIONING PERFORMANCE OF STRUCTURAL UNIT OF MOLDEDPULP PRODUCT*JI Hong-wei1, WANG He-min2, CHEN Jin-long2(1. Dept. of Packaging Engineering, Tianjin Commerce University, Tianjin 300134, China; 2. Dept. of Mechanics, Tianjin University, Tianjin 300072, China) Abstract: The overall load-bearing capacity and cushioning function of a molded pulp packaging result from those of structural units. For each structural unit, its geometrical shape and dimensions can be identified to determine the performance of molded pulp product. The commercial code ANSYS was employed in the present study due to its high performance in non-linear analyses. The non-linear buckling behavior of the structural unit can be studied by numerical simulation, resulting in the bucking critical load under compression, to be used to evaluate the load-bearing capacity of the structural unit. In addition to the analyzing on load-bearing capacity, numerical simulations of the structural units are carried out to evaluate the influence of the wall thickness under static compressive loading. The research shows that the wall thickness significantly influences the buckling bearing capacity of the structural unit subjected to axial compression. With the increase of wall thickness, the bearing capacity of the structural unit increases while cushioning performance decreases. So both load-bearing capacity and cushioning performance must be compromised in the design of molded pulp cushioning packaging, and the wall thickness can be selected according to the required packaging performance.Key words: molded pulp; structural unit; compression buckling; finite element纸浆模塑是一种立体造纸技术产品。

波纹管和毛细管内液氮流动和换热特性研究（论文）

波纹管和毛细管内液氮流动和换热特性研究摘要随着超导技术的发展，高温超导电缆在电力输运中逐渐得到重视并进行了广泛的研究。

由于波纹管具有良好的柔韧性和收缩性，在高温超导电缆中得到应用。

波纹管内的流动压力损失参数是高温超导电缆低温容器的主要的设计参数，这是因为压力损失决定了高温超导电缆的结构强度、循环压力以及液氮泵的功率。

所以研究波纹管内的流动特性具有重要意义。

为此，对通径为6mm，8mm和10mm的波纹管内液氮、氮气和水的流动特性进行了实验研究，为了更好分析波纹管内的流动特性，对波纹管内液氮的流动特性进行了数值计算。

为了进行波纹管内液氮流动特性的实验研究，制作了波纹管实验段，实验段的真空绝热结构，搭建了实验台。

测量了液氮在通径为8mm波纹管内的流动压降。

分析发现：在10000～25000的雷诺数范围内，液氮在波纹管内流动具有波动性，压力损失随雷诺数的增大而增大，要远大于光管的压力损失。

为了对比分析不同流体在波纹管内的流动特性，搭建了氮气和水在波纹管内流动实验台。

测量了氮气和水在通径为6mm，8mm和10mm的波纹管内流动压降。

分析表明：在4000～40000的雷诺数范围内，压力损失随质量流量的增大而增大。

在同一质量流量下，压力损失由大到小依次为DN6mm﹥DN8mm﹥DN10mm。

压力损失随雷诺数的增大而增大。

在同一雷诺数下，压力损失由大到小依次为DN6mm﹥DN8mm﹥DN10mm。

波纹管的摩擦系数要高于光管的摩擦系数。

摩擦系数随波纹高度的减小而减小。

对比发现：在波纹管内液氮、氮气和水的流动特性类似。

不同的是：在同雷诺数下，液氮的压力损失介于水的压力损失和氮气的压力损失之I间，但是水的摩擦系数却要小于氮气的摩擦系数。

为了进一步研究液氮在波纹管内的流动特性，应用FLUENT软件对液氮在波纹管内的流动特性进行了数值计算，得到了液氮在不同波纹管内流动的压力、速度分布，并对结果进行了详细的分析。

分析表明：压力损失随入口速度的增大而增大；在波纹管的波纹的前端和后端具有不同的压力梯度分布，并且后端处的压力要高于前端处的，在波纹内形成了涡旋流；在所考察的40000～200000雷诺数范围内，雷诺数对摩擦系数的影响不大，而波纹尺寸对摩擦系数具有主要的影响。

基于CFD数值模拟的排污阀冲蚀磨损影响规律

第３９卷　第２期Ｖｏｌ．３９　Ｎｏ．２钟林基于ＣＦＤ数值模拟的排污阀冲蚀磨损影响规律钟林１，２，冯桂弘１，张计春１，魏刚１（１．西南石油大学机电工程学院，西南石油大学能源装备研究院，四川成都６１０５００；２．南方海洋科学与工程广东省实验室湛江分室，广东湛江５２４０００）收稿日期：２０２０－０２－０７；修回日期：２０２０－０３－２６；网络出版时间：２０２１－０２－０２网络出版地址：ｈｔｔｐｓ：／／ｋｎｓ．ｃｎｋｉ．ｎｅｔ／ｋｃｍｓ／ｄｅｔａｉｌ／３２．１８１４．ＴＨ．２０２１０２０１．１８２６．００２．ｈｔｍｌ基金项目：国家重点研发计划项目（２０１９ＹＦＣ０３１２３０５）；南方海洋科学与工程广东省实验室（湛江）科研项目（ＺＪＷ－２０１９－０３）；国家重点研发计划项目（２０１８ＹＦＣ０３１０２０１）；国家自然基金面上项目（５１７７５４６３）第一作者简介：钟林（１９８５—），男，河南南阳人，实验师，博士（通信作者，ｚｈｏｎｇｌｉｎ８５８２９６＠１６３．ｃｏｍ），主要从事摩擦学理论及应用、钻头与井下工具、石油天然气装备现代设计理论及方法研究．第二作者简介：冯桂弘（１９９４—），男，四川南充人，硕士研究生（ｇｕｉ９４８２８＠１６３．ｃｏｍ），主要从事油气装备类冲蚀磨损及防护研究．摘要：针对排污阀因长期排污工作导致的冲蚀失效问题，采用ＣＦＤ仿真模拟的方法开展关于流体流速、颗粒粒径、含砂体积比与阀门开度等因素对阀套式排污阀冲蚀磨损性能影响的评价分析．结果表明：阀芯、阀座密封接触壁面间的冲蚀破坏是造成整个排污阀失效的主要原因．在流速１～９ｍ／ｓ、颗粒粒径０．１～０．５ｍｍ、含砂体积比２％～１０％、阀门开度１５％～９０％时，冲蚀磨损率与流体流速呈指数型正相关，冲蚀磨损区域随流速增加明显扩大．砂浓度增多加大了颗粒碰撞阀腔壁面的频率，其冲蚀率近似呈线性增长．颗粒粒径变化对排污阀平均冲蚀磨损率影响较小，小颗粒冲蚀行为下产生的冲蚀破坏相比大颗粒更为均匀一些．排污阀开度在１５％～３０％过程中，阀冲蚀磨损程度变化剧烈，从６０％开度开始，阀的受损情况趋于平稳．同时，在阀门开度增大的过程中，阀芯最大冲蚀磨损区域从圆周壁面逐步移动到阀芯下端面．研究结果对排污阀的整体耐冲蚀性能评价具有指导意义．关键词：排污阀；冲蚀磨损；数值模拟；排污阀工况；固液两相流中图分类号：ＴＨ１１７　文献标志码：Ａ　文章编号：１６７４－８５３０（２０２１）０２－０１５１－０７Ｄｏｉ：１０．３９６９／ｊ．ｉｓｓｎ．１６７４－８５３０．２０．００４８钟林，冯桂弘，张计春，等．基于ＣＦＤ数值模拟的排污阀冲蚀磨损影响规律［Ｊ］．排灌机械工程学报，２０２１，３９（２）：１５１－１５７．ＺＨＯＮＧＬｉｎ，ＦＥＮＧＧｕｉｈｏｎｇ，ＺＨＡＮＧＪｉｃｈｕｎ，ｅｔａｌ．ＩｎｆｌｕｅｎｃｅｌａｗｏｆｅｒｏｓｉｏｎｗｅａｒｏｆｂｌｏｗｄｏｗｎｖａｌｖｅｂａｓｅｄｏｎＣＦＤｎｕｍｅｒｉｃａｌｓｉｍｕｌａｔｉｏｎ［Ｊ］．Ｊｏｕｒｎａｌｏｆｄｒａｉｎａｇｅａｎｄｉｒｒｉｇａｔｉｏｎｍａｃｈｉｎｅｒｙｅｎｇｉｎｅｅｒｉｎｇ（ＪＤＩＭＥ），２０２１，３９（２）：１５１－１５７．（ｉｎＣｈｉｎｅｓｅ）ＩｎｆｌｕｅｎｃｅｌａｗｏｆｅｒｏｓｉｏｎｗｅａｒｏｆｂｌｏｗｄｏｗｎｖａｌｖｅｂａｓｅｄｏｎＣＦＤｎｕｍｅｒｉｃａｌｓｉｍｕｌａｔｉｏｎＺＨＯＮＧＬｉｎ１，２，ＦＥＮＧＧｕｉｈｏｎｇ１，ＺＨＡＮＧＪｉｃｈｕｎ１，ＷＥＩＧａｎｇ１（１．ＣｏｌｌｅｇｅｏｆＭｅｃｈａｎｉｃａｌａｎｄＥｌｅｃｔｒｉｃａｌＥｎｇｉｎｅｅｒｉｎｇ，ＳｏｕｔｈｗｅｓｔＰｅｔｒｏｌｅｕｍＵｎｉｖｅｒｓｉｔｙ，ＥｎｅｒｇｙＥｑｕｉｐｍｅｎｔＲｅｓｅａｒｃｈＩｎｓｔｉｔｕｔｅ，ＳｏｕｔｈｗｅｓｔＰｅｔｒｏｌｅｕｍＵｎｉｖｅｒｓｉｔｙ，Ｃｈｅｎｇｄｕ，Ｓｉｃｈｕａｎ６１０５００，Ｃｈｉｎａ；２．ＺｈａｎｊｉａｎｇＢｒａｎｃｈｏｆＳｏｕｔｈＭａｒｉｎｅＳｃｉｅｎｃｅａｎｄＥｎｇｉｎｅｅｒｉｎｇＬａｂｏｒａｔｏｒｙｏｆＧｕａｎｇｄｏｎｇＰｒｏｖｉｎｃｅ，Ｚｈａｎｊｉａｎｇ，Ｇｕａｎｇｄｏｎｇ５２４０００，Ｃｈｉｎａ）Ａｂｓｔｒａｃｔ：Ａｉｍｅｄａｔｔｈｅｅｒｏｓｉｏｎｆａｉｌｕｒｅｏｆｔｈｅｓｅｗａｇｅｖａｌｖｅｄｕｅｔｏｌｏｎｇｔｅｒｍｓｅｗａｇｅｗｏｒｋ．ＴｈｅＣＦＤｓｉｍｕｌａｔｉｏｎｍｅｔｈｏｄｗａｓｕｓｅｄｔｏｅｖａｌｕａｔｅｔｈｅｅｒｏｓｉｏｎｗｅａｒｐｅｒｆｏｒｍａｎｃｅｏｆｔｈｅｓｌｅｅｖｅｔｙｐｅｂｌｏｗｄｏｗｎｖａｌｖｅｂｙｆａｃｔｏｒｓｓｕｃｈａｓｆｌｕｉｄｆｌｏｗｒａｔｅ，ｐａｒｔｉｃｌｅｓｉｚｅ，ｓａｎｄｃｏｎｔａｉｎｉｎｇｖｏｌｕｍｅｒａｔｉｏ，ａｎｄｖａｌｖｅｏｐｅｎｉｎｇ．Ｔｈｅｒｅｓｕｌｔｓｓｈｏｗｔｈａｔｔｈｅｅｒｏｓｉｏｎｄａｍａｇｅｂｅｔｗｅｅｎｔｈｅｖａｌｖｅｃｏｒｅａｎｄｔｈｅｓｅａｔｓｅａｌｉｎｇｃｏｎｔａｃｔｗａｌｌｓｕｒｆａｃｅｉｓｔｈｅｍａｉｎｒｅａｓｏｎｆｏｒｔｈｅｆａｉｌｕｒｅｏｆｔｈｅｅｎｔｉｒｅｄｒａｉｎｖａｌｖｅ．Ｗｈｅｎｔｈｅｆｌｏｗｒａｔｅｉｓ１－９ｍ／ｓ，ｔｈｅｐａｒｔｉｃｌｅｓｉｚｅｉｓ０．１－０．５ｍｍ，ｔｈｅｓａｎｄｃｏｎｔａｉｎｉｎｇｖｏｌｕｍｅｒａｔｉｏｉｓ２％－１０％，ａｎｄｔｈｅｖａｌｖｅｏｐｅｎｉｎｇｒａｎｇｅｉｓ１５％－９０％，ｔｈｅｅｒｏｓｉｏｎｗｅａｒｒａｔｅｉｓｐｏｓｉｔｉｖｅｌｙｃｏｒｒｅｌａｔｅｄｗｉｔｈｔｈｅｆｌｕｉｄｆｌｏｗｒａｔｅ．Ｔｈｅｅｒｏｓｉｏｎｗｅａｒａｒｅａｓｉｇｎｉｆｉｃａｎｔｌｙｉｎｃｒｅａｓｅｓｗｉｔｈｆｌｏｗｖｅｌｏｃｉｔｙｉｎｃｒｅａｓｉｎｇ．Ｉｎｃｒｅａｓｅｄｓａｎｄｃｏｎｃｅｎｔｒａｔｉｏｎｉｎｃｒｅａｓｅｓｔｈｅｆｒｅｑｕｅｎｃｙｏｆｐａｒｔｉｃｌｅｓｈｉｔｔｉｎｇｔｈｅｖａｌｖｅｃａｖｉｔｙｗａｌｌｓｕｒｆａｃｅ，ａｎｄｔｈｅｅｒｏｓｉｏｎｒａｔｅｉｎｃｒｅａｓｅｓａｐｐｒｏｘｉｍａｔｅｌｙｌｉｎｅａｒｌｙ．Ｔｈｅｃｈａｎｇｅｏｆｐａｒｔｉｃｌｅｓｉｚｅｈａｓｌｉｔｔｌｅｅｆｆｅｃｔｏｎｔｈｅａｖｅｒａｇｅｅｒｏｓｉｏｎｗｅａｒｒａｔｅｏｆｔｈｅｓｅｗａｇｅｖａｌｖｅ．Ｔｈｅｅｒｏｓｉｏｎｄａｍａｇｅｃａｕｓｅｄｂｙｔｈｅｅｒｏｓｉｏｎｂｅｈａｖｉｏｒｏｆｓｍａｌｌｐａｒｔｉｃｌｅｓｉｓｍｏｒｅｕｎｉｆｏｒｍｔｈａｎｔｈａｔｏｆｌａｒｇｅｐａｒｔｉｃｌｅｓ．Ｄｕｒｉｎｇｔｈｅｏｐｅｎｉｎｇｏｆｔｈｅｂｌｏｗｄｏｗｎｖａｌｖｅｉｎｔｈｅｒａｎｇｅｏｆ１５％ｔｏ３０％，ｔｈｅｄｅｇｒｅｅｏｆｅｒｏｓｉｏｎｗｅａｒｏｆｔｈｅｖａｌｖｅｃｈａｎｇｅｓｄｒａｓｔｉｃａｌｌｙ．Ｆｒｏｍ６０％ｏｆｔｈｅｏｐｅｎｉｎｇ，ｔｈｅｄａｍａｇｅｏｆｔｈｅｖａｌｖｅｔｅｎｄｓｔｏｂｅｓｔａｂｌｅ．Ａｔｔｈｅｓａｍｅｔｉｍｅ，ｉｎｔｈｅｐｒｏｃｅｓｓｏｆｉｎｃｒｅａｓｉｎｇｔｈｅｖａｌｖｅｏｐｅｎｉｎｇ，ｔｈｅｍａｘｉｍｕｍｅｒｏｓｉｏｎｗｅａｒａｒｅａｏｆｔｈｅｖａｌｖｅｃｏｒｅｇｒａｄｕａｌｌｙｍｏｖｅｓｆｒｏｍｔｈｅｃｉｒｃｕｍｆｅｒｅｎｔｉａｌｗａｌｌｓｕｒｆａｃｅｔｏｔｈｅｌｏｗｅｒｅｎｄｓｕｒｆａｃｅｏｆｔｈｅｖａｌｖｅｃｏｒｅ．Ｔｈｉｓｓｔｕｄｙｐｒｏｖｉｄｅｓｓｏｍｅｇｕｉｄａｎｃｅｓｆｏｒｔｈｅｏｖｅｒａｌｌｅｒｏｓｉｏｎｒｅｓｉｓｔａｎｃｅｅｖａｌｕａｔｉｏｎｏｆｂｌｏｗｄｏｗｎｖａｌｖｅｓ．Ｋｅｙｗｏｒｄｓ：ｂｌｏｗｄｏｗｎｖａｌｖｅ；ｅｒｏｓｉｏｎｗｅａｒ；ｎｕｍｅｒｉｃａｌｓｉｍｕｌａｔｉｏｎ；ｂｌｏｗｄｏｗｎｖａｌｖｅｃｏｎｄｉｔｉｏｎ；ｓｏｌｉｄ－ｌｉｑｕｉｄｔｗｏｐｈａｓｅｆｌｏｗ排污阀是进行排污作业的主要设备之一，其广泛应用于石油化工领域。

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This article was downloaded by: [Beijing Institute of Technology]On: 25 August 2014, At: 21:20Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registeredoffice: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK

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Numerical Simulation on the Influencesof Initial Temperature and InitialPressure on Attenuation Characteristicsand Safety Distance of Gas ExplosionBing-you Jiang a b , Bai-quan Lin a b , Shu-lei Shi c , Chuan-jie Zhu a b& Jun Ning a ba Faculty of Safety Engineering, China University of Mining &

Technology , Xuzhou , Chinab State Key Laboratory of Coal Resources and Safe Mining, China

University of Mining & Technology , Xuzhou , Chinac School of Management, Xuzhou Normal University , Xuzhou , China

Published online: 19 Jan 2012.

To cite this article: Bing-you Jiang , Bai-quan Lin , Shu-lei Shi , Chuan-jie Zhu & Jun Ning (2012)Numerical Simulation on the Influences of Initial Temperature and Initial Pressure on AttenuationCharacteristics and Safety Distance of Gas Explosion, Combustion Science and Technology, 184:2,135-150, DOI: 10.1080/00102202.2011.622321

To link to this article: http://dx.doi.org/10.1080/00102202.2011.622321

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Downloaded by [Beijing Institute of Technology] at 21:20 25 August 2014 NUMERICALSIMULATIONONTHEINFLUENCESOFINITIALTEMPERATUREANDINITIALPRESSUREONATTENUATIONCHARACTERISTICSANDSAFETYDISTANCEOFGASEXPLOSION

Bing-youJiang,1,2Bai-quanLin,1,2Shu-leiShi,3Chuan-jieZhu,1,2andJunNing1,21FacultyofSafetyEngineering,ChinaUniversityofMining&Technology,

Xuzhou,China2StateKeyLaboratoryofCoalResourcesandSafeMining,ChinaUniversity

ofMining&Technology,Xuzhou,China3SchoolofManagement,XuzhouNormalUniversity,Xuzhou,China

Understandingasafetydistancenecessarytoavoidtheharmsofashockwavetoundergroundpersonnelmayhavegreatsigniﬁcancetothesafetyofundergroundpersonnel,disasterreliefefforts,andthetreatmentofthegasexplosionincoalmines.Througharoad-waymodelwithacross-sectionareaof80Â80mm2andalengthof100m,theexplosiveattenuationcharacteristicsofamethane/airmixturewithafuelconcentrationof9.5%andaﬁllingratioof10%weresimulatedbyusingAutoReaGassoftwareforvariousinitialtemperatures(248–328K)andinitialpressures(20–200KPa).Theresultsshowthatthesafetydistanceincreaseswiththeincreaseoftheinitialtemperatureandfollowsthechan-gingtrendofdecreasing,increasing,anddecreasingagainwiththeincreaseoftheinitialpressure.Thetimeofﬂamearrivaltoeachpointawayfrominitiationandthemaximumdistanceofﬂamepropagationbothincreasewiththeincreaseoftheinitialtemperature,buttheyarealmostthesameforvariousinitialpressures.Beforetheattenuationoftheshockwaveoccurs,increasingtheinitialtemperatureincreasesthemaximumtemperature,butdecreasesthepeakoverpressure,themaximumdensity,themaximumcombustionrate,andthemaximumgasvelocity.However,increasingtheinitialpressureincreasesthepeakoverpressure,themaximumdensity,andthemaximumcombustionrate.Theinﬂuencesoftheinitialtemperatureandtheinitialpressureontheseparametersatthelongerdistancepointsfromtheignitionsourcearegreaterthanthoseattheshorterdistancepoints.