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Investigation of the internal flow field for a subsonic stage of high pressure compressor through model testing

A large-scale four-stage low-speed research compressor was designed to represent the flow field structure in a subsonic stage, which is the seventh stage of a high pressure compressor. The aim of the design work was to undertake a careful high-to-low speed transformation. The low-speed compressor was designed as an “approximate repeating-stage” configuration, in which the third stage is the model stage and is slightly different from the other stages, while the first two stages and the last stage set up inlet and outlet conditions for it, respectively. The tip–hub ratio, solidity, and aspect ratio of the low-speed research compressor were restricted to be as close as possible to those of high pressure compressor. The blade sections along the span were designed to match the distributions of high-speed surface static pressure coefficient; furthermore, stacking rules of high pressure compressor apply to low-speed blades. The low-speed blades have been tested at the 4-Stage Research Compressor Facility of Nanjing University of Aeronautics and Astronautics. Detailed traverse flow measurements were conducted in the stator blade passages of the third stage and between blade rows, along with static pressure measurements on stator blade surface and particle image velocimetry measurements in the rotor passage. Experiment results show that due to the boundary layer separated below the mid-span of the rotor blade, the total pressure loss increases at the hub region of both the rotor and stator. In addition, the experimental results in the stator blade passage reflect the characteristics of the flow field in the bowed stator passage. The results indicated that the seventh stage of high pressure compressor needs to be optimized by inhibiting the boundary layer separation mainly on the rotor blade surface below the mid-span, which is our further work.