Performance Analysis of Inter-Stage Leakage Flows at Rotating Conditions in an Axial Compressor

For the compressor with shrouded stator blades, the stator well is a rotor-stator space between the rotating drum and the stationary shroud. Due to the pressure difference, a reverse leakage flow would travel through the stator well and inject into the main flow path. Although, the labyrinth seal is commonly placed under the shroud, the rotation effect and seal clearance variation in actual operation process have great impact on the characteristics of this inter-stage leakage, as well as the compressor performance. In this paper, experiments were conducted at a compressor inter-stage seal test rig. The leakage flow rates, total temperatures and swirl ratios were obtained at different speeds and working clearances. The proportions of rotation effect and the clearance reduction effect were analyzed by data processing. Comparisons indicate that the working clearance and leakage flow reduce about 43% and 50% respectively, when the rotational speed ω =8100 r/min. The proportion of reduction caused by the rotation effect is around 15%, while the influence of working clearance variation is much greater, accounting for about 35%. The windage heating coefficient and swirl ratio in the outlet cavity are almost in exponential relationship with the rotor speed. The increases in total temperature and swirl ratio generated by the rotation effect are found to be about 80%. In addition, the swirl and radial velocity profiles in the cavities were discussed by validated numerical simulations to reveal the typical flow characteristics. The data presented can provide guidance for better leakage conditions prediction as well as the inter-stage seal design enhancement.