连续流态下旋涡结构抽气特性研究

发布时间：2018-09-06 16:01

【摘要】：高真空直排大气干泵结构紧凑、干净无油、极限真空度高，是真空获得领域的研究热点。其中旋涡结构由于体积小、结构简单且可进行多级设计，常用于其低真空侧的排气。旋涡结构抽气特性的优劣直接决定了高真空直排大气干泵的性能，是干泵设计的关键技术之一。为了深入研究结构参数、结构形式以及各种工况条件（包括转速、温度、入口流量、出口压强）等对旋涡结构抽气特性的影响，本文采用计算流体力学方法对连续流态下旋涡结构的抽气特性进行数值模拟，取得了以下研究成果： 1）用CFX软件滑移网格方法的模拟结果表明，气体在环形通道内沿螺旋线爬行，产生了明显的纵向旋涡，且监测点压强变化曲线与理论的变化曲线相吻合，说明该方法可以有效模拟连续流态下旋涡结构的内部流动；而采用CFX软件浸入实体方法的模拟发现气体在通道内没有产生旋涡，与实测结果不符，说明该方法结果不准确； 2）压缩比随转速的增大而增大；随温度、入口流量、出口压强的增大而减小。通过增大转速，设计冷却降低气体温度，可获得更好的抽气性能。旋涡结构多级串联，可以获得较高的极限真空，，将气体抽到过渡流状态； 3）压缩比随间隙的减小而增大。在不同转速和不同压强时，本文旋涡结构在48-72个叶片范围内都有较好的抽气性能，最佳叶片数目都在60附近。圆形流道比矩形流道抽气性能更好； 4）比较了几种单级旋涡结构的抽气性能，发现EPX泵旋涡结构的抽气性能要优于Ontool泵旋涡结构。多级串联旋涡结构的压缩比不仅取决于每一级的压缩比，还取决于级间的间隙返流情况。在设计中对间隙进行合理预估，减小间隙的返流，可以提高多级旋涡结构的抽气性能。
[Abstract]:High vacuum air dry pump with compact structure, clean and oil free, high limit vacuum, is the research hotspot in vacuum acquisition field. Because of its small volume, simple structure and multistage design, vortex structure is often used to exhaust the low vacuum side of vortex structure. The exhaust characteristics of vortex structure directly determine the performance of high vacuum air dry pump, which is one of the key technologies of dry pump design. In order to study the influence of structure parameters, structure form and various operating conditions (including speed, temperature, inlet flow rate, outlet pressure) on the exhaust characteristics of vortex structure, In this paper, the extraction characteristics of vortex structures under continuous flow are numerically simulated by using computational fluid dynamics method. The following results are obtained: 1) the simulation results of the sliding mesh method with CFX software show that, The gas crawls along the helical line in the annular channel, resulting in obvious longitudinal vortex, and the pressure variation curve of the monitoring point coincides with the theoretical variation curve, which shows that this method can effectively simulate the internal flow of the vortex structure in the continuous flow state. However, the simulation using the CFX software immersion entity method found that the gas did not produce vortex in the channel, which was not consistent with the measured results, which indicated that the results of the method were not accurate; 2) the compression ratio increased with the increase of rotational speed, and the flow rate increased with the increase of temperature and inlet flow. The outlet pressure increases and decreases. By increasing the rotational speed and cooling down the gas temperature, a better exhaust performance can be obtained. A high limit vacuum can be obtained by multi-stage series vortex structure, and the gas will be pumped into the transition flow state. 3) the compression ratio increases with the decrease of the gap. At different speeds and pressures, the vortex structure in this paper has better exhaust performance in the range of 48-72 blades, and the optimum number of blades is about 60. The pumping performance of the circular channel is better than that of the rectangular channel. 4) the pumping performance of several single-stage vortex structures is compared and it is found that the pumping performance of the vortex structure of the EPX pump is better than that of the vortex structure of the Ontool pump. The compression ratio of multi-stage series vortex structure depends not only on the compression ratio of each stage, but also on the gap reflux between stages. In the design, the clearance is estimated reasonably and the backflow of the clearance is reduced, which can improve the pumping performance of the multi-stage vortex structure.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TB752

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