LEADING EDGE SKEWED-SWEPT DIAGONAL COMPRESSOR ROTOR AND NUMERICAL ANALYSIS ON ITS INTERNAL FLOW MECHANISM

Abstract

The structure of each part of a diagonal compressor directly affects its overall performance and internal flow. We introduce the Reynolds-averaged Navier-Stokes flow simulation for unit calculation on the whole system including a diagonal impeller, a vaneless diffuser and a volute. By analyzing different flow chromatograms of specific sections, we can compare the configuration of three types of diffusers and volutes and the meridian flow status of the corresponding diagonal compressors which serves as a basis for the impeller flow path as well as for its matching designs. Considering the interference between the rotor and the upstream and downstream stillness body, this thesis analyzes how the vaneless diffuser meridian flow path, the volute flow path and its section secondary flow affect the upstream rotor flow. Both the calculation and experimental data on the rotor outlet are compared, as well as the calculated numerical value of the meridian plane streamline distribution and the diffuser velocity distribution, upstream and downstream, coincides with the designed numerical value. Without changing the conventional quasi-three-dimensional design system, the thesis applies the annulus wall boundary layer theory and the velocity distribution diagram to sweep and skew the leading edge of the airfoil. A performance test shows that the leading edge skewed-swept diagonal rotor can better improve the stall characteristic in a low flow rate area and expand the surge margin, compared with conventional diagonal rotor. It can also efficiently restrain the low momentum fluid conglomeration near the wall region and reduce the secondary flow loss by sweeping and skewing the blade properly. The purpose of the thesis is to make a contribution to optimizing the overall structure design of diagonal compressors and to study further the complex internal flow between the leading edge skewed-swept diagonal rotor and the cover.