Experimental and theoretical investigations on dry gas seal transient performance and its disparity with steady performance

Through high-speed dry gas seal test rig, the real-time film thickness and leakage rate of spiral grooved dry gas seal have been monitored under different closing forces which are changed by adjusting spring compression. Under the conditions of different spring pressures and seal face deflection rates, the change rules of transient opening force and leakage rate are obtained by solving the transient-state Reynolds equation based on the measured real-time film thickness. Meanwhile, the steady opening force and leakage rate are figured out by solving the steady-state Reynolds equation using the average value of the real-time film thickness. Results show that the variation trends of calculated results based on steady-state or transient-state theory coincide well with experimental results. But with the influence of nonlinear effect, the average value of transient opening force and leakage rate are larger than steady opening force and leakage rate calculated with the average value of real-time film thickness, and compared with the value of steady leakage rate, the average value of transient leakage rate considered seal face deflection is closer to the experimental monitoring results.