The Fluid-structure Interaction Analysis And Performance Research Of Curved And Twisted Steam Turbine Blades

In the context of energy conservation and emissions reduction, transformation ofturbine flow passage has been booming. The numerical simulation has beenconducted on the last stage’s blades of125MW steam turbine in this paper, thereasons of producing secondary flows are analyzed, and the measures of reducingsecondary flows are proposed. The fluid-structure coupling analysis of bowing bladeshas been applied to verify its comprehensive performance. Main work andconclusions are as follows:(1) The three dimensional simulation and verifying have been conducted on thelast stage’s blades of125MW steam turbine. At last, the number of mesh is0.7million, the size of boundary layer is0.01milimeter, the turbulent model is SSTmodel, the interface is Frozen Rotor interface, the boundary condition is Mass FlowInlet，Static Outlet.(2) The analysis has been conducted on the original blades and the curved blademeasures are proposed. It shows when the curving angle is10degrees has best effectin four kinds of curving angle. Finally we get curved and twisted blade afterimprovement according to design criteria. Numerical simulation results show that thecurved and twisted blade isentropic efficiency is89.09%, the shaft power is4494.21kW, it can be found the isentropic efficiency increases by1.96%, the shaft powerincreases by148.43kW.(3)The fluid-structure interaction method has been conducted on the curved andtwisted blade, the result is compared with conventional analysis without regard tofluid-structure interaction influence. The calculation results show when using thefluid-structure interaction method the maximum stress is249.97MPa and when usingthe conventional analysis the maximum stress is225.33MPa. The maximum stress iscloser to the actual situation when using the fluid-structure interaction method and thesafety factor of the blade is higher when designing according to the results offluid-structure interaction method. The modal analysis has been conducted on the curved and twisted blade on the basis of fluid-structure interaction analysis, thecalculation results show when using the fluid-structure interaction method thedistribution range of vibration frequency is612.9-1462.1HZ, when using theconventional method the distribution range of vibration frequency is608.3-1458.1HZ,the presence of stress strengthen the whole blade stiffness, vibration frequency of thefluid-structure interaction is bigger than the vibration frequency of conventionalmethod.(4) The optimal design has been conducted on the operating parameters of thecurved and twisted blade using the Workbench platform. Choosing the best pointfrom1000sample points, the inlet degree is75.17°,the inlet mass flow is1.4396kg/s,the outlet pressure is2.43MPa, the inlet temperature is653.07K. The isentropicefficiency is93.30%, the shaft power is4748.30kW, and the maximum stress is222.94MPa. Comparing with the original condition, the isentropic efficiencyincreases by1.21%, the shaft power increases by254.10kW, the maximum stressdecreases by34.89MPa.