Numerical Investigation On The Flow In Tip Clearance Of The Last Three Stages Of Industrial Steam Turbine With High Output Power

In order to ensure the nonoccurrence of the friction between stator and rotor in the operation of the axial flow turbine, clearance is designed between the rotor tip and the cylinder’s internal surface. Therefore, the clearance leakage happens on the rotor tip. The loss caused by the clearance leakage flow and the mixing between the leakage vortex and the mainstream of the industrial steam turbine has become the key problems to improve the aerodynamic performance and efficiency of the steam turbine.At present, there is no accurate calculation model for the tip leakage losses for the high power industrial steam turbine of 100MW,which has affected the efficiency accounting and performance evaluation of the industrial steam turbine; And which reduces the competitiveness of similar products of our country in the international market.For the accurate evaluation of the last stages’ performance and the exploration of the last stages’tip leakage feature, the calculation model of the last three stages was builded, based on the data and design parameters of the last three stages blade provided by the HangZhou Turbine Company, Firstly, the equilibrium condensation model was applied. According to the results of numerical calculation, the flow of the overall passage of the last three stages and the flow phenomenon of the tip clearance were analyzed; the formation and development of clearance leakage flow were analyzed in detail, and the mixing of the clearance leakage flow and the mainstream was fully expounded. Secondly, numerical calculations were done under different inlet flow rate condition, the steam turbine performances of the last stages were also compared under different inlet flow rate condition, and the influence for the flow and the clearance leakage were analyzed under different inlet flow rate condition. The tip clearance values of the last three stages were changed to explore the relationship between different tip clearance values and the performance of the steam turbine under design condition and the relationship between the mainstream and leakage flow was analyzed’.The influence of the change of the tip clearance and the axial clearance was analyzed for the performance parameters of the last stages. A formula fitting method of the performance parameters and the tip clearance value were provided in the paper, and formulas of the polytropic efficiency and the tip leakage rate had been fitted.The formulas were proved having certain reference value after the error analysis. Finally, the deformation calculations of the turbine rotor were carried on by the way of solid structure, one-way fluid-structure coupling and two-way fluid-structure coupling. The blade radial elongation was comparative analyzed using different solid deformation calculation method under the condition of the high speed rotating, and the relationship between the blade radial elongation and the performance parameters of the last three stages were also analyzed.Conclusion of this study can provide the theoretical support for the future market development of industrial steam turbine, as well as can provide the theory basis for higher levels of industrial turbine research and development.