Pumping speed of cryopump for xenon

The xenon pumping speed testing system of the large-diameter external cryopump was designed to meet the plume test requirements for prototype electric propulsion.The flowmeter method was utilized to measure the xenon pumping speed.The test results show that the averaged effective pumping speed of doublecryopumps is 52 200L/s,and that of single-cryopump is 27 100L/s.The pumping speed ratio of two configurations is 1.93.It can be concluded that the pumping speed has in linear relationship with the number of cryopump,and the coefficient is irrelevant with the gas type.The averaged effective pumping speed of xenon is less than its nominal pumping speed,and the averaged pumping efficiency is 0.83.Under the identical inflow conditions,the averaged effective pumping speed ratio of nitrogen is 0.53,slightly less than the theoretical pumping speed ratio of 0.55.Consequently,it can be concluded that results assessment of large-diameter external cryopump design index can guide the engineering application,showing certain reference significance.

大口径低温泵抽速性能研究

针对大口径大抽速低温泵的抽速性能进行了研究。由于我国对小于400 mm的低温泵的抽速测试有规范,但是对1250 mm大口径的低温泵还没有规范,因此类比电子行业标准低温泵总规范SJ/T11259-2001中规定的抽速测试方法,提出了一种在真空系统中实际测量低温泵抽速的方法;采用流量标定法获得低温泵在不同氮气流量下的压强和抽速,最后将抽速的理论值和试验值进行了比较分析。结果表明,低温泵在1-10 m L/min小进气条件下的抽速为44441-53280 L/s,在大进气条件200-800 m L/min时抽速为51393-59132 L/s,均小于低温泵的理论抽速60891 L/s。小流量进气条件下的实际抽速低于大流量下的实际抽速。并给出影响抽速的因素不仅与被抽气体物性参数、低温泵流导参数及冷凝板面积等自身参数有关还受到真空舱的体积、实际材料放气等因素的影响。

活性炭的预处理对低温泵工作性能的影响

低温泵是利用低温吸附而达到获取真空的装置。与其他真空获取设备相比,其具有无油、低振动等优势。活性炭是低温泵常用的一种吸附剂,其对低温泵的工作性能起着关键性的作用。根据真空度的需求,一般要求低温泵对氢的抽速较大。这就需要适合于氢的吸附的活性炭。椰壳活性炭的孔隙大小对氢的吸附比较适合。本文首先对活性炭进行了预处理,用扫描电子显微镜和低温吸附仪对其结构和吸附性能进行了表征,并将其用于低温泵的吸附镇,发现安装了经过处理活性炭的低温泵其抽气速率和极限真空都有一定的提高。