鱼塘水电站溢洪道底流消能设计

贵州省遵义市鱼塘水电站岸坡式溢洪道底流水跃消能工设计中 ,比较了各种型式的消力墩、消力坎的作用及布置和常用的消力池型式。对矩形断面下挖式消力池与综合式B型消力池进行了对比分析 ,探讨了在大单宽流量、高流速情况下 ,如何合理运用消力墩、消力坎以改善消力池的工作状况 ,提高了消能效率 ,最大限度地减轻了下游河道冲刷     

复合涂层激光熔池温度场及流场的数值模拟

建立了复合涂层激光熔池三维准稳态流场及温度场的数值模型,计算出熔池温度分布和速度分布及几何形状。分析了激光功率对熔池温度场、流场及形状的影响。计算结果表明,对于厚度为0.08mm的Ti-Al(30%)复合涂层系统,功率为750W时,复合涂层没有熔化,但Al基材产生熔化;功率为1400W时,在不同材料层内形成上下两个分离的熔池。复合涂层先熔化还是Al基材先熔化,依赖复合涂层厚度。激光重熔实验确认了分离熔池的存在,同时计算结果和实验结果基本吻合。     

NUMERICAL SIMULATION OF PENETRATION PROCESS BASED ON THE VARIATION OF HEAT TRANSFER CONDITION

1.IntroductionInautomaticarcwelding,someworkpieceWhichhavevallableheattransfercondition,suchasvariablethicknessworkpieceorvariablesectionworkpiece,havethedifferentthermalconductiveconditionbecauseofthechangeoftheirthicknessandsectionareainthewidthdirection.'ImschangestheheatoutputoftheweldingPOol,aridthereforewemustadjusttheweldingparameters(weldingcurrentorweldingvoltage)inreal--timetoensureastablepenetration.Ifweonlyfindoutthethermalparameterswhichreflectthevariationofthicknessandsectionare…     

TIG焊变频电流下熔池谐振检测与研究

建立基于弧光传感的试验系统,在定点电弧在连续行走电弧下,利用频率线性变化的变动焊接电流对薄钢板ＴＩＧ焊熔池进行激振,当熔池固有振荡频率同激振电流频率一致时,熔池发生谐振。通过对电弧弧光采样数据幅值提取,检测出熔池振荡特征信号并可证明为熔池谐振信号,可用于实时判断焊接熔池尺寸信息,为解决连续行爱控制开辟了一条新途径。     

送粉式激光熔覆熔池深度的分析模型及其影响因素

在分析送粉式激光熔覆过程中能量分配和粉末颗粒云对激光束衰减规律的基础上,通过建立能量平衡方程,推导出熔池深度与工艺参数之间的定量关系表达式,系统分析了影响熔池深度的因素。结合相关的物理参数、工艺参数和金相检测的熔覆层宏观参数,对方程进行了理论计算。同金相法实际检测的熔池深度相比,理论值高于实际值,两者反映的规律是一致的,客观地反映了激光熔覆中工艺参数和工艺结果之间的关系。在激光参数保持不变的条件下,熔池深度随扫描速度和送粉速率的增大而减小。为熔覆工艺参数的优化、熔覆层质量的评定和现场控制系统的设计提供了理论依据。     

涉县游泳馆循环水设计

结合设计实例,对室内中小型游泳池循环水作了详细叙述,提出了对于室内中小型游泳池采用顺流循环供水方式应当注意的问题。     

Numerical study on the heat transfer characteristics of LIVE-L4 melt pool with a partial solidification process

Using the source-based SIMPLE algorithm based on a fixed grid method, a two-dimensional numerical model for a convection-diffusion controlled mushy region phase-change problem was developed to investigate the heat transfer characteristics of LIVE L4 melt pool subjected to a partial solidification process in a Pressurized Water Reactor (PWR) lower plenum during a hypothetical severe accident. For the binary non-eutectic mixtures of L4 melt, a linear liquid fraction temperature relationship was implemented on the calculations of the velocity and enthalpy in the mushy zone. The effect of fluid flow in the melt pool was analyzed, and numerical results for the cases with and without phase change model were calculated to investigate the effects of solidification on the heat transfer characteristics of L4 melt pool. Numerical results indicated that the phase-change model could well predict the main parameters of melt pool, e.g. the melt pool temperatures, heat flux through the melt pool, and the crust thickness. Results also indicated that the predicted Nu number without solidification was overestimated by about 12%, compared with that with solidification.     

The burning behaviors of pool fire flames under low pressure

To investigate the influence of low pressure on pool fire behaviors, liquid n‐heptane pool fires with the diameters of 6, 8, and 10 cm were tested in a low‐pressure altitude chamber. The tests were conducted under different static chamber pressures, ranging from 40 to 60 to 80 to 101 kPa. Fuel mass loss and high‐speed flame video were recorded during the whole burning process of each test. The mass burning intensity is determined by the convective and radiative heat feedback to the fuel, and analysis shows that the convective part is the major contributor to fuel evaporation. Video recordings show that flame height increases with the reduction of pressure, as supported by the dimensionless analysis. The flame puffing amplitude increases under low pressure, resulting in a portion of the flame being quenched. A special phenomenon was observed from the flame videos in that flame rotation emerged at the ending burning stage, which was attributed to the Coriolis force effect. Copyright © 2014 John Wiley & Sons, Ltd.     

Weld appearance prediction with BP neural network improved by genetic algorithm during disk laser welding

The appearance of welds is the external manifestation of welding quality. The morphology of molten pools is significantly associated with the weld appearance, but the approach to measure the morphology of molten pools during laser welding remains an outstanding challenge up to now. In this study, the shadows of molten pools were formed to describe the morphology of molten pools. Principal components analysis (PCA) is applied to analyze the characteristics of the molten pools’ shadow in order to reduce their redundancy. Then BP neural network improved by genetic algorithm (GABP) is established to model the relation between welding appearance and the characteristics of the molten-pool-shadows. The effectiveness of the established model is analyzed through two different welding speed experiments, and the results verify its prediction performance. The work provides an effective way to predict the weld appearance and assess the welding quality in real-time.     

倾斜基体表面激光立体成形沉积特性研究

针对基体表面倾斜条件下的激光沉积特性展开研究, 通过表征倾斜基体表面上激光沉积过程熔池的形貌特征以及几何特性, 揭示基体表面倾斜特性对熔池的形貌特征、几何特性和表面粘粉的影响规律, 并探讨其影响机制。研究结果表明: 在倾斜基体上, 熔池受重力作用流动铺展, 当沿着倾斜基体上坡扫描时, 熔池气液界面向下凹陷, 并且熔池随倾斜角度的增加逐渐变长; 当沿着倾斜基体下坡扫描时, 熔池随倾斜角度的增加逐渐变短。由于激光能量在斜面上分布状态不同, 上坡时熔池后沿能量低, 粉末未能完全熔化, 导致沉积层表面有粘粉, 且随着角度的增大表面粘粉增多; 下坡时熔池后沿能量高, 表面粘粉较少甚至没有粘粉, 成形表面质量较好。