Experimental And Numerical Investigations On Aerodynamic Performance Of Turbine Cascade With Winglet-Shroud

Gas turbine as an energy conversion and transmission device, has been widely used in various important industrial sectors. In its core component turbine, blade tip clearance leakage flow will bring the influence of two aspects:one is to reduce the gas flow rate through the blade passage, then the turbine output power is reduced; the second is to deteriorate the turbine cascade aerodynamic performance by the interaction in the clearance and mixing between the mainstream and the tip leakage flow. Therefore, controlling the tip clearance leakage flow is an effective method to improve the flow structure, reduce the aerodynamic losses and improve the overall efficiency of turbine.Based on the existing blade tip structure, a novel structure called winglet-shroud has been designed as the main research object. Wind tunnel experiment and numerical simulation studies were carried out. The aerodynamic parameters in the plane after the trailing edge and the static pressure distribution are measured in a low speed and large scale wind tunnel.By means of numerical simulation, the vortex structure variation and loss distribution in the cascade are analyzed in detail.Firstly, The aerodynamic performance comparison of four cascades with different width winglet is carried out numerically. The results showed that the vortex loss decreased with the increase of the width. The aerodynamic performance is improved slightly by the increase of winglet width. Considering the flow development and winglet structure characteristics, the optimal width is determined.Three different winglet-shroud structures are designed based on the above optimal winglet. The numerical results show that compared to the other two winglet-shrouds, the "0.5Cax" winglet-shroud inhibited the leakage vortex generation and development obviously, resulting in a significant reduction in the aerodynamic losses and leakage mass flow rate, which makes it to be the optimal structure.Secondly, Experiments and numerical simulations are further conducted to investigate the aerodynamic performance and the adaptability to incidence variation of the turbine cascade with the optimal winglet-shroud. Results indicate that compared to the winglet, winglet-shroud suppresses the upper passage vortex and tip separation bubble formation, reduces the strength of the passage vortex and trailing edge vortex, reduces the leakage vortex strength by decreasing the tip leakage mass flow rate; In the experimental incidence range, the strength of the upper passage vortex and the tailing edge vortex increases with the increase of the incidence and leakage vortex strength is not sensitive to the incidence variation. In summary, total loss increases with the increase of the incidence, negative incidences can improve the aerodynamic performance. However, aerodynamic loss increases when the incidence is less than a certain value.Then experimental and numerical methods are adopted to research the winglet-shroud width impact on aerodynamic performance. Results show that the increase of width has little effect on the vortex structure. With an increase in the width of the winglet part, improvements in aerodynamics is limited.Finally, exploratory research is adopted to study the aerodynamic performance of turbine cascade with sealed winglet-shroud in numerical and experimental methods. The results show that the leakage vortex intensity is reduced, and the upper passage vortex and trailing edge vortex intensity are increased. In general, the application of this structure can further reduce the aerodynamic loss.