Research On The Aerodynamic Design Of Low Capacity Mixed-Flow Steam Turbine

An analysis is made on the shortcomings of axial-flow steam turbine,especially the low-capacity turbine,which has few stages,and is among the main products of the company.Based on that,the mixed-flow steam turbine was proposed as a concept,which is free from the intrinsic shortcomings of axial-flow steam turbine to get a better performance.Then a review is made on the previous research work from two aspects:the research and application of the radial turbine and the performance prediction of the governing stage of the steam turbine.According to the parameters of the main products of the company,a set of performance indices is selected as the design requirement,based on which a mixed-flow turbine and an axial flow turbine are designed respectively,and the differences between them are compared and analyzed.The design processes of the regulating stage and pressure stages are customized respectively,for the mixed-flow and the axial-flow steam turbines.The prediction formulas of friction,blowing and steam exclusion losses are derived for both the radial-flow regulation stage and the axial-flow one.The regulation-performance curve is defined for the evaluation of the performance of the whole turbine.The 1D thermodynamic design,the blade airfoil selection,the flow channel design and the 3D CFD analysis are done for the regulation stages;while the 1D thermodynamic design and off-design performance prediction are done for the pressure stages;so that the performance maps of the two regulation stages and the pressure stages are obtained.Based on that,the regulation-performance curves of the axial-flow turbine and the mixed-flow ones are acquired.Finally,the loss of the chamber between the pressure stages and the regulation stage of the two steam turbines are calibrated through annual CFD analysis.The result of this research project shows that:the application of mixed-flow structure in steam turbine design can result in an increase of efficiency by 0.93%at design point,and 0.75%一1.8%in off-design condition,compared with the traditional axial-flow turbine,while still use the current airfoils for axial-flow turbine without any modification,under the common design requirements of the company.