Aerothermal Analysis of a Partially Shrouded Axial Turbine

摘要

This work presents the results of the aerodynamic and thermostructural analysis of three different shrouded axial turbine configurations. The blade geometry of the turbine stages and the tip clearances of the test cases under investigation are identical although the shroud design is varied. The first test case is representative of a full shroud geometry, and the second and third test cases adopt different partial shroud arrangements. The aerodynamic characteristics of these geometries have been investigated in previous studies, which are summarized in this paper. The influence of the shroud geometry on the heat load and mechanical stresses has been evaluated by a conjugate heat transfer approach coupled with finite element analysis. The combination of aerodynamic, centrifugal, and thermal loads has been applied to the solid blade model. Results show that the full shroud test case has higher mechanical stresses on the blade root but lower stress concentrations on the blade/shroud components. The partial shrouded cases have the lowest blade root stress. The last geometry is an optimized partially shrouded design, showing an improved lifetime achieved by a better stress distribution over the blade shroud compared to the other two cases. The effect of the shroud configuration on the aerodynamic performance, heat load, and mechanical stresses has been summarized, quantified, and discussed in detail. The combination of aerodynamic measurements and computational analysis shows that an optimum between aerodynamic performance and blade life is achieved by applying a small modification to the partial shroud geometry.