Research On Internal Temperature Field Analysis And Control Mechanism Of Dry Screw Vacuum Pump

As one of the new dry vacuum pump pumps in the 21st century,the Dry Screw Vacuum Pumps(DSVP)are widely used in various industries,and have been involved in petroleum and petrochemical,aerospace,semiconductor,electronic devices,food packaging,surface science and other industries.During the operation of DSVP,the high-speed rotating rotors continuously compress the gas to generate a higher exhaust gas temperature.In some severe process environments,the pumped medium is decomposed into highly toxic and highly corrosive substances.There are serious security risks.With the in-depth study of DSVP by Chinese researchers,the research direction of achieving basic pumping performance has gradually evolved into process control research under application.Combining theoretical research methods and numerical simulation techniques,this paper studies the gas thermal process before and after the gas temperature control in the dry screw vacuum pump,and obtains the optimal control range of process parameters such as pressure and temperature.In this paper,the constant lead DSVP and the single-stage gradational lead DSVP are studied.According to the basic laws of thermodynamics,the gas thermal process of the singlestage gradational lead DSVP under three different internal compression modes of adiabatic compression,multi-variable compression and isothermal compression was studied.Taking DSVP with a nominal pumping speed of 200m3/h as an example,the change rule of exhaust temperature with inlet pressure and the change rule of various thermodynamic parameters with working time are obtained.Before the over-compression condition appeared,in the low pressure section of the inlet,the exhaust gas temperature increased with the increase of inlet pressure.When the exhaust gas temperature reached the maximum value,as the pressure increases,the exhaust temperature decreases,until the over-compression condition occurs.However,since the constant lead DSVP has no internal compression,the exhaust gas temperature decreases linearly with the increase of the inlet pressure.For the study of the regulation of the internal gas temperature of DSVP,this paper introduces the aeration compression control mode innovatively on the pump cavity,and carries out the relevant thermal derivation calculation of the aeration compression process,and obtains the variation of the exhaust gas temperature with the aeration pressure.When the exhaust gas temperature decreases by a certain value,the change rule of gas temperature with working time in each stage of the pump is discussed.Since the constant lead DSVP has no internal compression,the gas transport process is equal pressure and equal volume transport,and the value of each state parameter at the end of the transport is equal to the end of the inhalation.Therefore,this paper only studies the final-stage aeration control process of the constant lead DSVP.The single-stage gradational lead DSVP has internal compression in advance,except for the suction lead,the other leads are subjected to aeration compression control research.Under the same aeration temperature,the optimal aeration pressure regulation range of each lead is determined.This paper provides theoretical guidance for the regulation of gas temperature in the pump during process production.Based on the actual structural size of the 200m3/h DSVP with nominal pumping speed,the thermal-structural coupling simulation analysis of the screw rotor was completed under the ANSYS WORKBENCH simulation platform.The temperature field distribution of the screw rotor and the total axial and radial deformation of each stage were obtained.It provides a reference for the calculation of the gap value and the calculation of the gas leakage return flow in the development stage of DSVP product.Combining the existing computing resources,the fluid calculation domain model is scaled down and simplified,and the FLUENT dynamic mesh simulation technology is used to complete the numerical simulation analysis of the internal flow field before and after the temperature adjustment of the constant lead DSVP,and the overall trend of gas pressure field and temperature field in the pump are obtained,the two changes echo each other.The gas pressure and temperature from the inlet to the exhaust port continue to increase,the neighboring two-stage numerical gradient before the regulation is relatively large.In summary,this paper provides a scientific basis for the reliability operation analysis of DSVP under special working conditions through theoretical derivation calculation and numerical simulation technology research method.At the same time,it provides theoretical support for the adjustment of the process parameters of DSVP,the modification of the pump cavity structure and the optimization design of the exhaust port structure.