Development of vacuum pump driven by thermo-molecular effect of a rarefied gas

在稀薄气体中，即使在没有外力的情况下，气体的温度场在诱导气体与时间无关的流动中也起着重要的作用。在这项研究中，我们开发了一种由这些流动驱动的新型泵(热分子泵)。研究结果如下：1.热边缘泵：在以往的研究中，热分子泵的驱动力仅限于在具有温度梯度的管道或通道中诱导的热发汗流动。在本研究中，作者设计了一种新型的热缘流驱动泵。它是在加热(冷却)物体的尖锐边缘附近诱导的一种流动。新装置不需要固体壁面的温度梯度，而固体壁面的温度梯度是克努森压缩机所必需的，并且会造成泵的能量损失。对新型泵--热边泵浦的性能进行了实验研究。通过数值模拟得到的另一个结果是，热边界泵的设计种类繁多。微通道中的热缘泵作为一种工作在较高压力(如大气压)下的泵是很有前途的。2.热分子泵的气体分离效应：在热分子泵中，平均自由程的大小是不可忽略的。在这种情况下，气体混合物的速度取决于气体的香料。因此，在这些泵中分离气体混合物是可能的。通过对稀薄混合气体的DSMC模拟，发现热边泵具有较大的分离效果。

In a rarefied gas, the temperature field of the gas plays an important role in inducing time-independent flows of the gas even if there is no external force. In this study we develop a new type of pump (thermo-molecular pumps) driven by these flows. The results are as follows :1.Thermal Edge Pump :In the preceding studies, the driving force of the thermo-molecular pumps was limited to the thermal transpiration flow, which is induced in a pipe or channel with a temperature gradient. In this study, the author devised a new type of pump driven by the thermal edge flow. It is a flow induced at the vicinity of a sharp edge of heated (cooled) body. The temperature gradient of the solid walls, which is necessary in the Knudsen compressor and causes energy loss of the pump, is not required in the new device. The performance of the new pump -thermal edge pump- was examined experimentally. Another result, which is obtained by numerical simulation, is that the design of thermal edge pumps has wide varieties. The thermal edge pump in the micro channel is promising as the pump which works at higher pressures (e.g.atmospheric pressure).2.Gas Separation Effect of Thermo-molecular Pumps :In the thermo-molecular pumps, the size of the mean free path is not negligible. In this situation, the velocity of the mixture of the gas depends on the spices of gas. Thus it may be possible that the mixture of the gas is separated in these pumps. By using the DSMC simulation of the rarefied mixture of gases, it is found that the thermal edge pump has fairly large separation effect.