Optimal turbine blade design enabled by auxetic honeycomb

Abstract

Gas turbine blades are subjected to unusually harsh operating conditions—rotating at high velocities in gas streams whose temperature can exceed the melting temperature of the blade. In order to survive these conditions, the blade must efficiently transfer heat to an internal cooling flow while effectively managing mechanical stresses. This work describes a new design strategy for the internal structure of turbine blades that makes use of architected materials tailored to reduce stresses and temperatures throughout the blade. A full 3D characterization was first performed to determine the thermomechanical properties of generalized honeycomb materials with different design parameters: honeycomb angle and wall thickness. A turbine blade cross section was then divided into multiple discrete domains so that different generalized honeycomb materials could be assigned to each of the domains. Optimization of the material assignments was performed in order to minimize the stress ratio—ratio of the maximum Mises’ stress and the temperature dependent yield stress—in the entire model. The optimized design showed substantial improvement with respect to a baseline model; the factor of safety was increased by 171%, while the maximum Mises’ stress and temperature decreased by 42% and 72% respectively. The use of generalized honeycomb materials allows for local control of the material properties to tune the performance of the turbine blade. The results of the optimization clearly indicate that auxetic honeycombs outperform conventional designs; since their lower in-plane stiffness helps to reduce stresses caused by thermal gradients. Our results demonstrated the feasibility of using 3D-printing compatible architected materials in turbine blades to increase their factor of safety and potentially increase operating temperatures to improve thermal efficiency.