Study Of Flow Control And Design Methods In Low-Reaction Boundary Layer Suction Compressors

In recent years, the rapid development of aero-engine and gas turbine request higher pressure ratio, higher efficiency and stability for the design of compressor parts. Currently, the tip speed of compressor rotor could not been significantly improved due to the constraints of material, structure and security. Further improvement of aerodynamic loading will lead to large scale separation, low efficiency, stall, fltter or even surge for the compressor. Based on this understanding, a subsonic highly loaded low-reaction boundary layer suction compressor concept and its design method are proposed in this dissertation. It is validated through theoretical analisis, numerical simulation and experiment study.In this dissertation, the low-reaction boundary layer suction compressor concept and its design method are firstly described through theorectical analysis. The evaluation method of efficiency and loss for this new tyoe of compressor is discussed at different cycle levels. The accuracy and realability of the numerical software used to simulate the flow field of subsonic compressor is verified by the experiment data of a certain low speed two stage repeated compressor.A low speed subsonic two stage repeated compressor is redesigned into a single stage highly loaded compressor by using the low-reaction design concept. The flow field and design feature of the low-reaction rotor blade and stator cascade with boundary layer suction are all studied and analyzed. By using optimization method, the acceleration section near leading edge and the diffusion section near trailing edge of the stator cascade are modified and shaved which leads to a better flow field structure and higher performance. The stage performance with different boundary suction flow rate as well as the unsteady performance is studied under the condition of design back pressure. The numerical results predict that the single stage has a good off-design performance. The bowed blade technique is also studied by applied into the high turning angle stator cascades with boundary layer suction. The results show that positive bowed blades have a better effect than negative ones because of the strong secondary flow at the endwall region of the highly loaded stator cascades. The positive bowed blades reduce the endwall loading and thus the extra consumption work of the endwall boundary layer suction is decreased. The negative bowed blades raise the endwall loading and emphasis the boundary layer separation. On the basis of successful design procedure of single stage low-reaction compressor, the single stage low-reaction design concept is developed into a multi-stage low-reaction concept. By using the multi-stage design method, the last three stages of a certain heavy duty gas turbine is redesigned with two stages low-reaction boundary layer suction compressor. The stage counts are reduced by one while it contains one rotor blade and three stator rows. The two stages low-reaction boundary layer suction compressor has higher performance than the original three stages compressor. The geometry features, total performance and detailed flow field of the two stages is then analyzed. The open questions of the redesign work are summarized and the tentative ideas to improve them are given out.The experiment investigation of the single stage low-reaction boundary layer suction compressor is carried out to verify the feasibility of the low-reaction design concept and the accuracy of the numerical simulation. The total pressure contours and pitchwised averaged parameters along span at the stator exit as well as the speed line are analyzed. The flow control mechanism of boundary layer suction method is studied by the flow field and performance analysis of typical operation points. At last, the low-reaction boundary layer suction compressor concept and its design method is proved by the comparison of the experiment data and numerical results.