A study of the stability enhancement achieved by the casing treatment of an oblique-flow impeller equipped with a rear-mounted volute housing

Experimentally studied and analyzed through a numerical simulation was the casing treatment of a small-sized high-speed oblique-flow impeller. The test results show that the casing treatment structure being designed can effectively enlarge the operating range of the oblique-flow impeller. By using a parallel calculation technology, numerically simulated was the flow field of the whole machine, including the casing treatment structure and volute housing of the impeller, revealing the mechanism governing the stability enhancement achieved by the casing treatment. The low-energy fluid in the area of the blade tip was sucked into the treatment slot by the casing treatment structure, flowed out of the circumferential slot in the area at the suction surface side inside the blade passage and jetted into the rotor passage, thus eliminating the blockage caused by the low-energy air mass in the area, improving the air flow status at the blade tip of the rotor and delaying stall occurrence.