Theoretical And Experimental Study On The Upstream Pumping Effect Of Face Grooves Of Gas Seals

Upstream pumping mechanical seal,as a typical structure of non-contact face seal,has been widely applied due to zero leakage,low friction and long operating life.In order to control the leakage characteristic of gas face seal,the theoretical and experimental study on the upstream pumping effect of face grooves of gas seals was conducted here.First,a mathematical model on the upstream pumping effect of spiral grooves gas face seals was built based on the gas lubrication theory,and geometrical parameters of spiral grooves as well as performance parameters of face seal are defined.The finite difference method was discussed to solve the theoretical model.The results showed that the finite difference method can achieve the flow conservation thus ensure the calculation accuracy of gas leakage.Second,theoretical analysis on leakage characteristic of the upstream pumping gas face seal with spiral grooves was analyzed.The results showed that a circumferential closed zone with high pressure exceeding seal pressure can be obtained near the higher-pressure side of seal face due to upstream pumping effect of spiral grooves at high rotational speed and low seal pressure,which prevents the inflow of high pressure sealed fluid and is beneficial to achieve zero leakage thus reversed leakage.Besides,it is shown that the leakage decreases first and then increases with the increase of rotational speed,number of grooves and film thickness,contrarily increases first and then decreases with the increase of groove depth,spiral angle and groove width ratio,and decreases with the increase of groove radius.The leakage direction changes reversely once rotational speed,film thickness and groove number reach certain values.Finally,experimental study on leakage characteristic of the upstream pumping gas face seal with spiral grooves was carried out.The results showed that the upstream pumping spiral groove can provide enough opening force to ensure that the mating faces can separate quickly during starting operation and achieve the non-contacting operation,thus avoid friction and wear.Upstream pumping effect of the spiral grooves can be generated to decrease leakage,which enhances with the increase of rotational speed.The zero leakage can be obtained by designed geometrical parameters of spiral grooves and operating parameters of face seal reasonably.Based on theoretical and experimental study on the upstream pumping effect of face grooves of gas seals,a method of controlling zero leakage of face seal was presented.An experiment was conducted to improve the design theory.The research results can be used to guide the engineering design and application.