Numerical investigations on the leakage flow characteristics of pocket damper labyrinth seals

Abstract

A combined finite element analysis and computational fluid dynamics was developed to investigate the discharge characteristics and flow field of pocket damper seals at high pressure (up to 7.2 MPa) and high rotational speed (up to 50,200 r/min) flow condition. At first, the leakage flow rates of the published experimental pocket damper seals with the eight-bladed and eight-pocket were conducted at three different pressure drops and three different rotational speeds, and a comparison between finite element analysis and computational fluid dynamics results, experimental data and computational fluid dynamics results was presented. It showed that the utilized finite element analysis/computational fluid dynamics numerical method has sufficient precision (the maximum relative deviation is less than 1.3%) to predict the leakage flow rate through the pocket damper seals. The importance of taking rotor growth with rotational speed into consideration was made apparent by the rotor growth and leakage results. Then, six pressure ratios and seven rotational speeds were utilized to study the effects of these two factors on the leakage flow characteristics of the pocket damper seals. Numerical simulation results show that the leakage through a pocket damper seals increases with decreasing pressure ratio and asymptotically approach a maximum value corresponding to the choked flow condition when the pressure ratio is small enough (less than 0.26). The leakage flow rate with and without rotor growth included both decrease with the increasing rotational speed. In addition, it is quite necessary to take rotor growth with rotational speed into consideration when the rotational speed is very high (larger than 20,200 r/min) according to the numerical results and the engineering accuracy requirement. The influence of the pressure ratio on the structure of the leakage flow field in seal cavity is negligible. A significant influence of the rotational speed on the flow field in the active cavity has been observed. The circumferential partition wall can significantly decrease the circumferential flow in active cavity of the pocket damper seals.