Orifice Characteristics Analysis And Restrictor Design With Stability Enhanced And Leakage Controlled Of Hydrostatic Dry Gas Seal

Pharmaceutical reactor is the key equipment to production various APIs.Its shaft seal is used to isolate the reactor cavity and the external environment,which is the key to create a highly clean and sterile reactor cavity environment.Throttle orifice hydrostatic dry gas seal is a good choice of high clean and low-speed pharmaceutical kettle because it can form stable lubricating film with large bearing capacity and stiffness at low speed.However,there are still some problems in hydrostatic DGS,such as low accuracy and efficiency of numerical solution of sealing performance,poor bearing capacity,stiffness and stability of lubricating film.On the basis of the accurate and efficient numerical method of hydrostatic DGS and the study of the classical throttle orifice characteristics of hydrostatic DGS,the optimization of the a single restrictor structure shape and the matching of the distribution patterns of multiple restrictors are proposed to achieve high film bearing capacity,stiffness and high stability of hydrostatic DGS.It is of great practical and strategic significance to ensure the long-term stable operation of high clean pharmaceutical reactors and even the pharmaceutical safety in China.Efficient and accurate solution of the pressure distribution of hydrostatic DGS is the key to the solution of its steady-state performance such as opening force,film stiffness and leakage rate.According to different structure restrictors and functional requirements of hydrostatic DGS,the turbulent large eddy simulation and Reynolds equation based on laminar flow assumption are proposed to solve the film pressure distribution,and the correctness of the numerical model is verified by the independently developed hydrostatic DGS film pressure distribution test platform.The non equidistant difference grid is proposed to solve the problem of cross scale solution between the throttle orifice and the seal surface.A new method for measuring the pressure distribution at any point of the seal surface is proposed by combining the circumferential rotation of the static ring with the radial translation of the test ring.The reasonable value of the main geometric parameters of the classical throttleorifice hydrostatic dry gas seal restrictor and the gas film,and its correlation with the steady-state performance are the basis of the structure optimization of the restrictor.The classic orifice throttle hydrostatic DGS is taken as the research object.The influence of the main geometric parameters in the inlet hole,throttle orifice,equalizing groove and lubricating film on the throttling outlet pressure and steady-state performance of hydrostatic DGS is numerically analyzed.The key influencing factors and the parameter range of the geometric parameters are obtained.Based on the neural network algorithm,a correlation structure-effect model was obtained between the steady-state performance,throttling outlet pressure and key geometric parameters of hydrostatic DGS.Fluid flow characteristics near the orifice outlet and in the equalizing groove and pressure distribution have a significant influence on the film bearing capacity and stability of hydrostatic DGS.Hyperelliptic curve with good geometric characterization is introduced to describe the orifice outlet and the equalizing groove section profile and investigate the effects of the cross-sectional shape of orifice outlet shape and equalizing groove on the lubricating film bearing capacity,leakage rate and stability of hydrostatic DGS.On the basis of considering the machining feasibility,the influences of the chamfer,fillet in the orifice outlet and the regular section shape of equalizing groove are studied,and obtain the optimal section shape of the orifice outlet and equalizing groove.The distribution pattern of the restrictor on the seal surface has a significant effect on the pressure distribution of whole seal surface.Inspired by the structure of porous restrictor with high bearing capacity and film stability,micro array orifice and radial multi-row orifices of hydrostatic DGS are proposed.Based on the large eddy simulation theory,compare and analyze the film bearing capacity and leakage characteristics of hydrostatic DGS with three different types of restrictor,i.e.classical throttle orifice,micro array orifice and multi-row orifices,and focuse on the influence of radial orifice outlet mode and its mechanism,and proposes a new structure of hydrostatic dry gas seal with adjustable outlet mode.The research results of this paper systematically put forward the design method of high stability and low leakage throttle orifice hydrostatic DGS restrictor,which can provide theoretical basis for the engineering selection and optimization design of high performance dry gas seal for low-speed pharmaceutical reactor.