Design and Verification of an Auxiliary System for High Vacuum Die Casting

Vacuum die casting is the optimal method to produce high quality aluminum alloy components.At present,there are still very few systematic studies on vacuum die casting theory and equipment design.On the basis of the existing theories of the vacuum die casting pumping and venting systems,a simplified model is established in this research.The model has an aggregate unit consisted of ＂vacuum pump ＋ buffer tank＂ and a cylindrical container（including the shot sleeve,cavity and exhaust channel）.The theoretical analysis is carried out between the cavity pressure and the pumping time under different volume models.An auxiliary system for high vacuum die casting is designed based on the above analysis.This system is composed of a vacuum control machine and a new vacuum stop valve.The machine has a human-computer control mode with ＂programmable logic controller（PLC） ＋ touch screen＂ and a real-time monitoring function of vacuum degree for buffer tank and die cavity.The vacuum stop valve with the ＂compressed gas ＋ piston rod ＋ labyrinth groove＂ structure can realize the function of whole-process vacuum venting.The new system shows great advantages on vacuuming the cavity with a much faster speed by making tests on an existing die casting mold and a 250 t die casting machine.A die cavity pressure less than 10 kPa can be reached within 0.8 s in the experiment and the porosity of castings can be greatly decreased.The systematic studies on vacuum die casting theory and equipment have a great guiding significance for high vacuum die casting,and can also be applied to other high vacuum forming in related theoretical and practical research.

水击补气式压力罐及水力瞬变仿真

空气阀常常安装在输水管检修孔侧壁,进气后部分气体就会存留在检修孔上部产生气垫式压力罐的水击防护作用。据此,提出了水击补气式压力罐装置的设计方法,即利用泵站事故断电产生的水击负压现象,通过真空破坏阀或空气阀给压力罐补气,以防止输水管发生液体汽化现象并削减水击最大压力。然后,建立了水击补气式压力罐水力瞬变数值仿真数学模型。最后,以一个实际输水工程为例,计算比较了分别设置空气阀、空气阀调压室及真空破坏阀补气式压力罐时的水击防护效果,结果表明,补气式压力罐水击防护效果最好。

波纹管与阀杆真空电子束焊接工艺研究

真空电子束焊接是一种能量集中、熔深较大的精密焊接方法。阀用波纹管壁厚较薄时,与阀杆或法兰焊接具有较大的困难,通过优化焊接接头,设计合理的焊接工装,消除波纹管与阀杆或法兰的配合间隙,采用真空电子束焊接,可以很好地解决这一问题。

真空遮断阀吸取系统动态特性研究

遮断阀在多吸盘真空吸取系统中对失效的吸盘进行自适应遮断,从而让未失效吸盘内的真空度保持在正常的范围内。以ZP2V遮断阀为核心,建立真空遮断阀吸取系统的动态模型进行理论分析,并在单吸盘真空吸取系统上进行模拟仿真,搭建试验平台对仿真结果进行验证。根据实际工况搭建了多吸盘真空吸取系统,在两种失效形式下进行了遮断阀性能动态特性测试,分析各因素对系统真空度及流量的影响和规律,为采用遮断阀的真空吸取系统的设计和选型提供依据。

夹管式真空界面阀设计与通过性模拟研究

船舶上的真空排污系统中作为阻隔大气与真空的核心部件真空界面阀,设计一款可靠实用的真空界面阀对整个真空排污系统至关重要。文章设计了一款真空界面阀,利用ANSYS Workbench对橡胶阀芯进行有限元分析,探究压强不同、阀芯结构不同情况下形变量与应力规律,利用DPM粒子模型检测出口粒子所占百分比模拟通过性,得出界面阀的最佳设计参数比例为1.40:1。通过出口粒子呈现正态分布现象,结合粒子轨迹云图、速度云图,分析出口粒子呈现正态分布原因在于直径不同的粒子,质量速度不同,粒子受到重力以及萨夫曼剪切提升力作用不同,解释了出口粒子分布原因。由于阀芯结构导致的形变量不同,使得粒子离壁面的距离不同,因此不同结构模型壁面对粒子的吸收程度也不同,这就使得出口粒子所占百分比不同,由此分析解释了真空界面阀结构不同所导致的阀门通过性差异。

Application of vacuum sealing drainage technique in poor healing wounds after heart valve surgery

Background： Poor healing wounds or postoperative infection after open-heart surgery are most commonly seen, especially in secondary surgery for heart diseases, with an incidence rate of 2.2% after a valve replacement surgery. If not treated in time or the infection progresses, it can lead to sternal infection, even mediastinal and pericardial infection, causing a higher mortality rate. It becomes a really troublesome and complicated case when a poor healing occurs in midsternal incision after the heart valve surgery and a higher medical cost may be needed. Methods From January 2009 to February 2013, 162 patients who underwent heart valve surgery through midsternal incision approach and had a poor healing of wound were observed for prospective randomized controlled trial. The patients were randomly assigned to a vacuum sealing drainage group （n = 81） who received vacuum sealing drainage for healing of the wound or a control group （n = 81） who received traditional treating for the infected wound. Their therapeutic effects, healing time and treatment costs, etc were compared. Results Two patients from the vacuum sealing drainage group came back to hospital for repair due to dehiscence of the incision after discharge, and no patient died. Six patients from the control group came back to hospital for repair due to dehiscence of the incision after discharge, two came back to hospital for surgery due to chronic osteomyelitis, and one patient died two weeks later after surgery due to severe chest infection. Wound healing time for vacuum sealing drainage group was 14.6 ± 3.6 days, which was significantly shorter than that of the control group （21.2 ± 7.8 days, P 〈 0.05）, while the medical costs showed no significant difference between the two groups （P 〉 0.05）. Seventy-eight patients （96.29%） in the vacuum sealing drainage group showed a good healing of the wound and sternum after a six-month follow-up. Conclusion The use of vacuum sealing drainage technique in poor-healing wounds after heart valve surgery through midsternal incision approach could achieve good therapeutic efficacy, with shorter wound healing time and similar costs as traditional treatment.

制氦装置应用三偏心真空蝶阀密封圈的探索

基于氦气本身特性、制氦装置高密封性要求以及液氦资源经济性的考虑,以三偏心蝶阀为研究对象,对制氦装置用密封圈设计进行了多方面的探索和研究。首先针对多种密封圈方案进行尝试,探讨其各自的优缺点和局限性。然后提出了一种采用金属骨架橡胶密封圈来有效解决真空密封问题的设计,并从密封性、工作力矩及寿命等方面对该设计进行了理论和试验验证。最后对该设计的整体经济性进行了阐述。该金属骨架橡胶密封圈设计能充分满足常温下制氦装置中调节蝶阀的密封要求。

Vacuum sealing drainage technique in the treatment of poor healing wounds after heart valve surgery:experience in cardiac nursing

Background Poor wound healing or postoperative infection after open-heart surgery is most commonly seen. If not treated in time or the infection progresses, it can lead to sternal infection, even mediastinal and pericardial infection, causing a higher mortality rate. Vacuum sealing drainage （VSD） is a new technology to promote wound healing. We studied the use of VSD technique in poor wound healing after heart valve surgery to see if it could achieve good therapeutic efficacy. Methods From 2013 October to 2014 October in Guang- dong General Hospital, 86 cases of the application of vacuum sealing drainage technique in the treatment of cardiac nonunion after valve replacement in patients with nursing observation. The treatment time, death rate and infection rate, etc were compared. Results Wound healing time of 86 patients receiving vacuum sealing drainage was 14.6 ± 3.6 days, and no patient died. Two patients came back to hospital for repair due to dehis- cence of the incision after discharge. Conclusion Nursing observation and drainage management were the key of VSD. VSD technique is worthy to be popularized clinically.

汽轮机真空波动原因分析及处置

汽轮机排气真空度高低直接影响整个机组运行的安全性、稳定性和经济性。机组出现真空波动时,从凝气系统和冷却水两个角度入手分析排查出汽轮机真空波动的原因是大气安全阀内漏引起的真空抽气器凝液液封破封,并在机组不停机的情况下解决系统真空波动问题,在保证压缩机安全运行的同时,为同行业异常工况处理提供一定的参考。

真空系统在模拟火星表面低气压环境的应用

火星一直被认为是太阳系中除地球外生命最有可能繁盛过并生存至今的地方,故而对其表面环境的模拟,对火星探索起着重要的作用。本文依托于XX大学空间模拟装置火星尘舱系统项目的需求,设计了一套火星表面低气压环境模拟系统,采用真空泵组降低火星尘舱内的气压,采用气动调节型阀门进行高精度动态压力调节,维持舱内压力稳定,详细介绍了系统设计技术参数、组成、工况及抽速计算流程。

高坝洲电厂真空破坏阀改进

高坝洲电厂真空破坏阀在机组转轮室形成真空时开启,起到破坏真空,可有效减轻转轮叶片空蚀的产生。高坝洲电厂机组自投产以来真空破坏阀装置存在调整和维护检修不方便等问题,在检修期间对1F机组真空破坏阀进行整体换型改进,将原使用多年弹簧更换为新弹簧,采用挂重法,对弹簧受力进行调整。经本次整体换型改进的优化处理后,真空破坏阀密封良好,效果显著。

变压吸附制氧性能提升实践

介绍了真空变压吸附制氧工作原理、设计性能参数、运行控制时序及阀位调整等基本概念。通过对四塔流程优化前、后运行参数的性能对比分析,论述了时序、阀位及鼓风机进气条件对制氧性能的影响。

真空吸鱼泵控制系统的设计与实现

本文设计的真空吸鱼泵控制系统,采用水环真空泵产生负压,设计了一套基于伺服进行精准位置控制的四通阀装置,实现了吸鱼和排鱼过程的高效切换,提高了吸鱼效率、降低了在捕捞输送过程中对渔获的损伤。整机控制系统基于PLC 控制模块为核心、配置了现场操作的触摸显示人机界面,并通过组态技术,从端到云构建了在 Web 端和移动端对装备进行监控的系统,实现了对装备的本地和远程监控。

汽轮机门杆漏汽系统典型问题分析及处理

汽轮机门杆漏汽系统对机组运行的安全性和经济性有较大影响。在介绍门杆漏汽系统的作用与结构基础上,详细阐述了门杆漏汽引起的轴封母管压力波动、上下缸温差大、真空严密性不合格、停机后轴封带压等典型问题的分析及处理方法,针对门杆漏汽接入轴封供汽母管的机组、接入相应压力等级抽汽管道的机组和接入凝汽器疏水扩容器的机组,提出了相应的建议,为大型火力发电机组门杆漏汽系统的安全运行及合理设计提供了借鉴意义。

南水北调睢宁二站真空破坏阀优化设计与应用

本文介绍了一种全新的断电闭阀型真空破坏阀,该破坏阀用于泵站的断流装置,可以在主水泵机组运行和停运状态下实现流道内的真空破坏,以防止水泵和电机的损坏。与现有的断电开阀型真空破坏阀相比,本破坏阀采用断电闭阀的方式,通过主弹簧和电磁铁的协同作用,在主机组运行时保持进气通道关闭,停机时打开进气通道,实现流道内外的气压平衡。该破坏阀具有节能、安全可靠等优点,可以有效提高破坏阀的运行效率和使用寿命。

15NiMoSiCr10中速船用针阀体的热处理工艺开发

针阀偶件是船用柴油机的一种重要零件,在船舶航行的安全性和可靠性中发挥关键作用。利用低压脉冲真空渗碳高压气淬技术,在国内率先成功开发了15NiMoSiCr10船用针阀体的热处理工艺,同时较系统地研究了其热处理性能特点。渗碳温度选用960℃,采用VC-Sim 1.4.1专家软件对渗碳时间和乙炔脉冲进行仿真,降低工艺开发成本。960℃渗碳后直接进行18 bar高压氮气淬火,经-120℃冷处理2 h后分别在不同温度下进行抗回火性试验。试验结果表明,15NiMoSiCr10针阀体具有回火抗力好、金相组织优良以及芯部硬度较高等较好的工艺性,使用寿命超过6000 h,相比其他材料针阀体,其使用寿命得到大幅提高,有效提升了产品的市场竞争力,带来了较大的经济效益。

真空压铸中高真空排气阀与薄片通道式排气阀的排气性能对比

利用自制盒状压铸试验模具,在650t冷室压铸机上,对传统的薄片通道式真空排气阀及高真空排气阀空压射动作的型腔背压进行了测量。在压射冲头静止状态下,对型腔的最大真空度等排气阀性能参数进行了试验测量,并系统研究了不同的真空压铸模具密封工艺对型腔内实际达到真空度的影响。分别利用两种不同的排气阀进行了A383铝合金的真空压铸,针对铸件上不同位置的密度进行了取样分析,对两种排气阀的排气性能以及应用于真空压铸工艺的可行性进行了评估。

真空压铸用真空阀及真空控制装置的开发

开发了具有自主知识产权的真空压铸的关键技术——真空阀及其控制系统。真空阀的工作原理是利用金属液的冲击力,通过杠杆驱动关闭排气通道。真空系统采用PLC和触摸屏控制,确保真空阀处于正常可靠的工作状态。真空压铸技术已在汽车底盘悬架、变速箱体、3G通讯腔体等关键零部件上获得了应用,效果良好。

真空技术在真空排污系统中的应用

真空排污系统是利用负压管道中的负压梯度将用户处排放的污水逐步输送、收集至真空站后集中处理及排放的污水收集系统。综述了真空排污系统的分类及适用范围,真空的获得及真空检漏测试的标准。介绍了真空排污系统中用户终端的形式和关键阀件。简述了真空排水管网的输送机理。比较了不同的真空罐排放方式及其技术关键。

在不同真空度下的卷心菜真空冷却实验对比研究

在卷心菜真空冷却实验中,真空度是影响冷却时间和效果的主要因素。本文通过设定不同的自动补气阀工作压力范围来控制真空室的压力,进行卷心菜真空冷却实验,并分析了此过程中水分在低压下的气化过程。实验发现,自动补气阀工作压力范围分别为700 Pa-900 Pa、1000 Pa-1200 Pa和1300 Pa-1500 Pa时,当温度最低处(表叶)达到预定的0．7℃时,耗时分别为11 min、22 min和43 min,中心温度分别为3．86℃、6．68℃和9．11℃。结果表明：700 Pa～900 Pa的自动补气阀工作压力范围,对卷心菜进行真空冷却实验的效果较好；对于特定食品的真空冷却,应该可以找到各自恰当的自动补气阀工作压力范围,以提高冷却的效率。