双螺杆真空泵工作过程数值模拟
Numerical Simulation for Working Process in Twin Screw Vacuum Pump

对等螺距和变螺距2种螺杆真空泵分别进行了分析,通过能量守恒、质量守恒方程及泄漏模型分别计算了2种真空泵工作过程中的气体压力变化及极限真空度、功耗、抽速等性能参数,由此搭建了真空泵实验系统试验台,展开了双螺杆真空泵压力变化及泄漏的实验研究,分析了2种真空泵性能差别的原因及变螺距螺杆真空泵的优势,并对变螺距真空泵性能进行了实验研究。数值模拟结果表明,变螺距真空泵不论在极限真空压力,还是在指示功率大小方面,均优于等螺距真空泵。实验结果表明,所建物理模型能很好地描述真空泵的实际工作过程,对于所研究的机型,变螺距齿型相对于等螺距齿型,其极限真空压力从3.75 Pa降低到2.32 Pa,指示功率降低了11％。以上内容在螺杆真空泵设计和改型,以及螺杆真空泵产品开发和性能的预测方面都有指导意义。
The existing gradational lead and constant lead vacuum pumps were analyzed respectively. The geometric properties of these two types of pumps, including working volume, length of contact line, length of tip circle, and area of leakage, were evaluated according to the given rotor profile. Energy and mass conservation equations and leakage models were considered to acquire the performances of these two types of vacuum pumps. Gas pressure in the working volume, ultimate vacuum, power consumption and pumping speed were calculated. The performance differences between the gradational lead and constant lead vacuum pumps and the advantages of gradational lead type were discussed. The simulation shows that ultimate vacuum and indicated power in the existing gradational lead vacuum pump are lower than those in the constant lead vacuum pump, the ultimate vacuum reduces from 3.75 Pa to 2.32 Pa, and the indicated power reduces by 11％