Flow characteristics of a low-solidity cantilevered stator embedded in a 4-stage low-speed research compressor

Abstract

This research presents the influence of the low-solidity design on the loss and stability of the cantilevered stator and the evolution of the hub leakage vortex. The highly loaded 4-stage low-speed research compressor (LSRC) with an embedded cantilevered stator (CS) of Stator 3 (S3) was experimentally measured at the blade row outlet and in the S3 passage, respectively, and the URANS simulation method was calibrated accordingly. Then, the prototype CS blade number was reduced, namely low-solidity cantilevered stator (LSCS), to increase the blade loading. The diffusion factor (DF) of LSCS at the midspan at the design working condition is 5.2% higher than that of CS. The URANS results show that LSCS provides higher efficiency for the 1.5 stage compressor with a consistent stall margin. For S3, the total pressure loss of LSCS is lower than CS at the design point (DP) working condition, but it is the opposite at the near stall (NS) working condition. For LSCS at the NS point, the blockage region becomes large and occupies the lower half of the fore blade passage because the low-solidity stator could not provide the enough flow turning ability, and the core of the hub leakage vortex (HLV) moves forward and the intensity is strengthened. The high loss region of LSCS at the near stall condition is consistent with the size of two hub leakage vortices. The first HLV breakdown is caused by unsteady mixing flow, and then it twists downstream and contacts with the trailing edge of the adjacent blade pressure surface. The study of the hub leakage flow characteristics of the low-solidity cantilevered stator can help designers to control flow better.