DSMC Simulation Study Of Disk Type Molecular Pumps In Transition Ranges

Disk-type molecular pump is one kind of the drag molecular pump, and flowing direction of gas is radial and it is different from axial flowing drag molecular pump. For its special property, the physical dimension of pump cavity in disk-type molecular pump is very important for pumping speed and ultimate pressure. So when we design these pumps, we must make out the most important point how to let the gas fluid efficiently at the radial direction. In practice, there are many theory modeled lines and many kind of methods being used in research. This paper mainly studies the arc modeled line of pump cavity and uses Direct Simulation Monte Carlo Method (DSMC method). In this type of pump, arc type modeled line is used very widely, because the line is simple to be described and easy to be processed, and becomes the chief type of disk molecular pump modeled line. At the same time, disk type molecular pump has compacted structure and light weight, so in the compound molecular pump it is shorter than circular column as the drag stage, and reduces the height of pump body, and enhances the pump's dynamic balance. Direct Simulation Monte Carlo Method is an advanced method to study rarefied gas dynamics. In this method, it adopts grad method, sampling collision method, uncoupling of Moving and collision method and random numbers method to describe the status of molecular, then statistics and analyses moving, collision, reflecting , rotating , chemical reaction of molecular. This method also records the position , velocity, temperature, mass, number density, degree of freedom , momentum, energy of molecular, and obtains the macroscopic flow parameters and character. Using these results, we can analysis kinematics, dynamics , thermodynamics properties of rare gas. This thesis uses Direct Simulation Monte Carlo Method to study the pumping process of disk-type molecular pump, and keeps on professor Ba Dechun's study in other field include molecular temperature, surface temperature , reflect model of surface , gas species and collision model. From this thesis, we get that the molecular temperature influences pumping properties greatly,...