Research On The Impact Of Variable Geometry Cascade By Tip Slotting

With the continuous development of gas turbine technology, variable working condition requirements are also gradually increasing. Variable geometry turbo technology is one of the effective means of adaptable ability, it can regulate the gas turbine performance in good operating point. However, this kind of design will bring about the blade tip clearance, so that the tip flow patterns change a lot ,and then generate additional leakage losses. The leakage flow in a turbine is very complex, almost 1/3 of the losses in a turbine stage can be associated with the tip clearance. In order to improve the turbine performance, nature of tip clearance flow and mechanisms of losses should be taken seriously, and then effective measures are taken to improve the leakage flow state, thereby achieving the purpose of controlling leakage losses.In this paper, the research has been taken the turbine vane cascade adopting passive control method-tip slotting for study. First of all, under the same boundary conditions,Contrasting the aerodynamic parameters and flow structure of the three kind of case including vane cascade without Shaft on the end zone, the vane cascade with shaft and the vane cascade with shaft by end slotting .The results showed that the slotted tip for variable geometry turbine cascade plays a very significant role in suppressing leakage. At the same time, the shaft and the recess change the status of the end zone leakage flow, So that the formation and development of leakage vortex are very different from the situations that the end without shaft.Then, transforming installation angle of the turbine vane cascade with slotted tip,comparing the -5,-3,0, +3, +5 degrees the five kinds of different angle on vane cascade of the numerical simulation. Contrasting the amount of leakage, the total pressure recovery coefficient,the pressure distribution and other parameter , analyzing the development patterns and trends of the tip leakage vortex and the passage vortex , summing up the impact of the entire flow structure and flow loss mechanism on variable geometry cascade with slotted tip. At last, according to principle of the labyrinth seals, different orientations of ribs are arranged in the notch in front of the shaft, the result shows that the lateral rib perpendicular to the flow direction structure making a great contribution to control the leakage vortex and passage vortex, and the adaptability of angle attack is great as well.