| In recent years,people's health consciousness has been increasing with the improvement of living standard,which has increased the demand for high quality medicines.Medical equipment is the first step to ensure the quality of drugs.The stirring kettle is the key equipment in the pharmaceutical industry,and its shaft end seal is the key technology to ensure the cleanliness of the medium in the kettle and prevent the drug contamination.The dry gas seal of the kettle is working at low speed,medium pressure fluctuation and severe swing.It is very easy to cause seal face wear and seal ring collision,resulting in seal failure,which poses a great threat to the safety and reliability of the device.The hydrostatic dry gas seal is widely used in the low speed kettle and other equipment because of its characteristics of small leakage rate and not limited by the rotate speed.As a key structure of hydrostatic dry gas seal,the equalizing groove has the important function of improving the sealing opening force and enhancing the stiffness of the gas film,which can greatly improve the reliability and stability of the sealing work.The influence of different pressure equalizing groove structures on hydrostatic dry gas seal is studied to obtain higher reliability and strong stability of hydrostatic DGS,which is of great significance to the rapid and healthy development of the pharmaceutical industry in China.Firstly,four typical pressure equalizing grooves HS-DGS in circular,elliptical,fan and annular are used as the analysis objects.Based on the finite difference method,the calculation model of HS-DGS is established.The double iteration and relaxation iterative method is used to solve the HS-DGS Reynolds Equation,and the end face gas pressure distribution is obtained.The comparison of the literature value is compared.and the correctness of the calculation procedure is proved.On this basis,through the analysis of the pressure and flow field characteristics of the end face of four kinds of pressure equalizing grooves HS-DGS,the influence mechanism of the pressure equalizing grooves on the performance of HS-DGS and the change law of the sealing performance parameters with the groove type are revealed.In order to obtain the stronger film stiffness,the optimum groove and the optimum range of the structure of the HS-DGS pressure equalizing groove are obtained.Secondly,the HS-DGS experimental device that can measure the opening force,gas film thickness and leakage rate.is independently designed and built.The effect of pressure equalizing groove structure and working conditions on the sealing opening force and leakage rate is obtained,and the theoretical calculation results are verified.The results show that the overall performance of HS-DGS can be improved significantly by opening pressure equalizing groove.The experimental and theoretical results of the sealing performance parameters vary with the working conditions,and the theoretical prediction value of the opening force is in good agreement with the experimental values.Finally,the influence of the gas vortex in the pressure equalizing groove on the flow and pressure fluctuation characteristics is studied based on the large eddy simulation theory,and the inducement of the HS-DGS's micro amplitude vibration and the self excited vibration of the air hammer is revealed.On this basis,a new type of HS-DGS with a spoiler structure is proposed and compared with the characteristics of gas flow and pressure fluctuation in the traditional HS-DGS.The results show that the new pressure equalizing groove structure can effectively suppress the cyclone phenomenon,improve the gas flow characteristics and the stability of the gas film obviously.The range of the value of the key dimension parameters of the spoiler structure is obtained. |
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