Mechanisms of Rotor–Rotor Interactions on Blade Loading in Vaneless Counter-Rotating Compressors at Different Matching Speeds

Abstract

Abstract. Comparative analysis is conducted to clarify the influence mechanisms of rotor–rotor interactions on the blade loading of vaneless counter-rotating compressors at different matching speeds. Results reveal that the upstream rotor (R1) blade loading originates from shock waves and potential flow of the downstream rotor (R2). At low speeds, the unsteady pressure fluctuation intensity (Su) on R1 blades is the smallest, less than 700 Pa. As speed increases, R2 blades generate normal shock waves, and the maximum Su increases to about 40,000 Pa. The larger the Mach number (Ma) before shock wave, the stronger Su. When R2 shock waves are oblique shock waves, the maximum Su decreases to about 20,000 Pa. R2 blade loading originates from wake and wake vortices of R1. Su distributes across the entire blade surface. At low speeds, Su is less than 6000 Pa. As speed increases, the pressure difference between R1 wake and mainstream increases. R2 blades generate shock waves to sweep R1 wake and form shedding vortices. The maximum Su increases to about 40,000 Pa, and its distribution is related to the flow velocity near R2 blade. It is higher in subsonic regions than in supersonic regions. Additionally, the influence of the relative position between R2 and R1 on blade loading is investigated under different axial clearances. For R1, Su remains stable when the absolute clearance is less than 1.25 times the original midspan clearance (δ0), and decreases when it is greater than 1.25 δ0. For R2, Su on the blade decreases with increasing clearance.