Study On The Influence Law Of Rotor Structure Parameters On Pumping Performance Of Screw Vacuum Pump

With its structural characteristics of the core rotor,the screw vacuum dry pump has the advantages of adapting to complex working conditions and high reliability,and is widely used in the semiconductor industry,pharmaceutical chemical equipment and other industries.At this stage,domestic and foreign experts and scholars have done a lot of research work on the screw pump rotor line and working process.This topic mainly studies the rotor pumping performance of the rotor by theoretical calculation,numerical simulation and experimental analysis.The law of influence explores the influence of different types of rotors on the gas physical parameters of the pump,and then evaluates the structural characteristics and performance advantages of a certain rotor,and provides reference and support for the design theory of the rotor,thus promoting the autonomous design of domestic dry pump products.Starting from the principle of screw rotor design,the end face profile of the involute rotor is deduced by coordinate transformation and meshing principle,and the detailed profile parameter equation is obtained.The MATLAB numerical simulation analysis platform is used to realize the rotor parameterization program modeling,so as to quickly output different types of rotor profiles by changing the characteristic parameters.According to the assembly condition of the actual product,the difference of the rotor volume utilization coefficient under different inner and outer diameter ratios under the condition of constant center distance is calculated,and the influence of the involute base circle radius on the performance of the end face line is discussed.In addition,based on different axial profile lines,the composition of the rotor interstage leakage channel and the mathematical expression method are analyzed for the equal pitch and the gradient pitch rotor,which provides the calculation basis for the flow state of the gas between the subsequent stages.Using the basic law in engineering fluid mechanics,the gap leakage of the screw vacuum pump is simplified into the annular gap flow and the thin-wall small hole model processing,and the expression of the total leakage of the pressure flow and the shear flow caused by the rotation of the screw rotor is obtained.Conservative and flow conservation are used to derive the governing equations of physical parameters between stages,and then the interstage pressure distribution and leakage amount of different types of rotors are solved.Based on the actual product related parameters,different gaps,internal and external ratios,and leads are calculated and analyzed.The pressure and return flow changes caused by the number and rotor deployment mode are used to explore the physical parameters of the gas in the screw vacuum pump.In addition,the amount of leakage caused by different backflow methods is discussed,and the proportion of different leakage modes between the levels is analyzed.In addition,based on Fluent,the dynamic mesh technique is used to analyze the internal flow field of the screw pump,and the distribution of pressure field,velocity field and temperature field is analyzed,which provides a reference for the internal gas state of the screw pump.The internal pressure fields of rotor structures with different gaps,different lead numbers and different deployment modes are analyzed under the condition that other rotor structural parameters are unchanged.The internal pressure of the screw pump gradually increases from the inlet end to the exhaust end and is obviously distributed in a gradient.There is a backflow phenomenon between the stages.This phenomenon is more serious in the high pressure area on the exhaust side;the gas flow rate is evenly distributed inside the pump chamber.However,the velocity at the inlet and outlet is larger and the velocity is the largest at the inlet,and the gas velocity suddenly increases at the small gap;the internal temperature increases step by step,and the maximum temperature occurs on the exhaust side.The internal pressure conditions under different gaps are analyzed.The change of the gap greatly affects the ultimate pressure and the inter-stage pressure difference.As the gap becomes smaller,the return flow becomes smaller,the ultimate vacuum increases and the pressure difference between the stages increases.The higher exhaust pressure suppresses under-compression during venting.The internal pressure of different lead times is analyzed.With the increase of the number of leads,the pressure distribution between the stages is more uniform,which is beneficial to reduce the ultimate pressure.In addition,the pressure field distribution of the rotor with the variable pitch and the variable pitch rotor can be obtained.The pitch has an advantage in the ultimate pressure,and the variable pitch is more stable due to the presence of internal compression.Finally,the experimental research on the effects of rotors with pumping performance on different pumping performances was carried out.The screw rotors with equal pitch,gradual pitch and three-stage pitch were designed to facilitate performance comparison and control the geometric parameters and pumping capacity of each rotor.The same,and static interference and dynamic interference check to ensure the feasibility of manufacturing.According to the actual working conditions,the temperature distribution and constraints are applied.The threestructure rotors are analyzed by thermal-structural coupling.The deformation of the three rotors under stable working conditions is compared,which provides reference and support for the gap design of the three rotors.Based on the vacuum dry pump pumping theory experimental platform,the screw pump test content and the test method for pumping performance and internal temperature are determined.It is proposed to realize the performance measurement scheme of various structural rotors in the same pump cavity,and combined with the actual pump cavity structure.Adjust the position of the test point for pressure and temperature.The effects of different compression modes on the pumping performance of the screw pump were analyzed around the pumping pressure curve,the power consumption pressure curve and the interstage pressure test.In summary,this paper analyzes the pumping performance of different types of rotors of screw vacuum dry pump.Based on the basic theorem of fluid mechanics,the theoretical calculation of pressure and leakage between stages was completed.The pump was analyzed by Fluent numerical simulation.The flow field distribution analysis of the cavity was carried out,and the pumping performance experiment of the equal pitch was completed by using the dry pump pumping theoretical test platform.Through theoretical calculation,numerical simulation and experimental verification,this paper provides a theoretical basis for the design and development of the screw vacuum pump rotor and the internal gas state research.