Computational Investigation and Design Study of Adaptive Axial-Flow Turbomachinery Rotor Blade

Gas turbine blades of conventional rotorcraft engines are generally optimized to operate at nearly a fixed speed with fixed blade geometries for the design operating condition. When the operating condition of the engine changes, then the flow in the compressor or turbine may need to be guided to more optimum direction. Articulating the pitch angle of turbine blades in coordination with adjustable nozzle vanes can improve performance by maintaining flow incidence angles within the optimum range at all operating conditions of a gas turbine engine. Maintaining flow incidence angles within the optimum range can prevent the likelihood of flow separation in the blade passage and also reduce the thermal stresses developed due to aerothermal loads for variable speed gas turbine engine applications. U.S. Army Research Laboratory has partnered with University of California San Diego and Iowa State University Collaborators to conduct high fidelity stator-rotor interaction analysis for evaluating the aerodynamic efficiency benefits of articulating axial flow turbine blade concept. In addition, a design study for articulating turbine or compressor rotor blade using smart material based actuators using Shape Memory Alloy (SMA) has been carried out. In this paper, the computational flow patterns are compared between the baseline fixed geometry blades and articulating conceptual blades. The computational fluid dynamics studies were performed using a stabilized finite element method developed by the Iowa State University and University of California San Diego researchers, and using a commercial software, CONVERGE for comparison. The results from the simulations together with a design study using SMA actuator for articulating both stator and rotor blades synchronously for axial flow turbomachinery are presented in this paper.