Numerical Analysis And Experimental Research On The Internal Flow Mechanism Of The Leading Edge Skewed-Swept Diagonal Rotor

Since the molding methods of the skewed-swept blade were proposed from 1960's, the Researches from all over the world attach high importance to it. With the development of the related subjects, the Research on the skewed-swept blade-molding rule gradually develop into a subject of "sweep aerodynamics". It can change the static pressure grads distribution; restrain the development of the secondary flow; reduce the conglomeration of the low-momentum fluid near the wall region and improve the aerodynamic characteristic of the turbomachinery by sweeping and skewing the blade properly. In order to explore the effective approach of improving the stall margin of fans and compressors by sweeping and skewing the rotor, the leading edge skewed-swept diagonal rotor is designed and studied, its internal flow mechanism is analyzed by numerical simulation and experimental research in this dissertation.The quasi-three-dimensional design method of the leading edge skewed-swept diagonal rotor is given in detail. This design method is based on the virtual-equivalent velocity triangle diagram and the one-seventh boundary layer rule. In order to keep the blade cascade characteristic is the same with the practical data, the theoretical correcting equations and methods, which was originally proposed by Schlichting, is also given. The computer software is programmed to design the leading edge skewed-swept diagonal rotor in this dissertation. The designed skewed-swept diagonal rotor has the following distinctive features: The leading edge is skewed and swept near the hub and casing wall region. The blade's camber line is the same as the conventional rotor; that is to say, the rotor's exit flow angle is the same as the conventional rotor. So the leading edge skewed-swept diagonal rotor can be designed under the conventional design system.The leading edge skewed-swept diagonal rotor is designed. Its aerodynamic characteristic curve is measured on the own-made automatic testing equipment that was designed according to the AMCA210-85 and GB1236-2000 standards. The tested results show that the skewed-swept diagonal rotor diminished the stall region that was usually existed at the lower flow rate for the normal diagonal rotor. The newly designed diagonal rotor increased the working range. The calculated characteristic curve of the skewed-swept It is supported by the National Natural Science Foundation of China (No: 50176012 ) and the Doctorate Foundation of the Ministry of Education(No: 20020487025)diagonal rotor is in good agreement with the tested data.The complex internal flow phenomena of the leading edge skewed-swept diagonal rotor are calculated and analyzed by using commercial CFD software. The internal flow mechanism of the skewed-swept diagonal rotor is revealed. The backflow that existed at the suction surface near the leading edge and hub wall region of the normal diagonal rotor is eliminated by the leading edge skew and sweep. The low energy fluid near the hub wall region is sucked into the high-energy fluid near the blade's middle region. The conglomeration of low energy near the hub wall region is reduced. The fluid block and loss is decreased. The calculated results showed that, the wake of the skewed-swept diagonal is weaker than that of the normal diagonal rotor; the influence of the casing and hub wall on the wake is weakened; the blockage of the low energy fluid near the hub wall region is reduced and the working range of the leading edge skewed-swept diagonal rotor is increased.The leakage vortex and the tip clearance flow mechanism is revealed and discussed at different clearance size and different flow rate by using CFD simulation. At large tip clearance size, there exists the strong rolling up of the fluid between the clearance flow and the main flow. The leakage vortex is generated at the axial position of 33% chord length of the blade tip, and it is near the blade's suction surface. The leakage vortex moves toward the adjacent blade's pressure surface in the blade's flow passage along the rever...