Study On Flow Mechanism And Design Methodfor The Return Channel With Large Turning Angle

With the development of aerospace power generation by generation, centrifugal compressor thrust weight ratio is increasing, the aerodynamic load each compressor weight unit beared is continuously upgrad, multi-stage centrifugal compressor used more and more widely. The return channel is an important part of multistage centrifugal compressor, a correct understanding of the return channel characteristics in the reactor is of great significance to improve the whole level of compressor performance. Therefore, the method of numerical simulation is adopted to study the flow law and design technology of return channel in this paper, the main work is as follows:1. Programing the modeling design program with Delphi. In the program, we design meridional channel at first with the program, then combine camber line with thickness of leaf blade to generate blade.2. Study on the characteristics and effect of the meridional channel configuration to return channel. The U bend outlet flow angle in the wheel side near wall region reaches a maximum value. In blade passages, two secondary flow vortex leads to flow angle of blade outlet non-uniform distribution.It will lead to emerging the flow separation and increasing flow loss that when the radius of curvature of U type curve wheel type line is too small. Expanding blade passage outlet area, can reduce the flow velocity to decrease the flow loss, but expand too much will cause flow separation, but increase the loss. When The wheel type line of L bend turn too fast,it will increase the flow loss, enhance the return channel outlet flow angle distribution non-uniform.3. Study on law of angle of attack, the blade turning angle, blade number, blade loading distribution form and thickness to the return channel performance and flow characteristics. 0 degree of attack angle into the return channel blade results in minimum flow loss, increasing the angle of attack could increases the flow loss. Positive angle of attack in small range can enhance airflow transition, improving the exit flow angle distribution.When the blade turning angle is too small, the friction losses are higher, but the return channel outlet flow angle’s distribution is well;when the blade turning angle is too large, the flow separation will emerge. No matter that the number of leaves is too small or too small, flow separation will emerge. Properly increasing the number of blades, can improve the exit flow angle uniformity. Uniform loaded vane return channel make flow loss minimum, the former load blade is the most beneficial to improve flow turning. When the load is more concentrated to the leading edge of the blade, the flow turning is more improved. Blade thickness will increase the flow loss, but can inhibit the development of second flow, improving the uniformity of the outlet flow angle distribution.