Prediction and Avoidance of Turbine Blade Fatigue Using a Fluid/Thermal/Structure Interaction Methodology

ABSTRACT: The drive to increase turbine inlet temperature and overall pressure ratio as well as to reduce turbine weight has led to increases in aerodynamic/thermal loads that can induce flutter and resonance in blades responsible for structural fatigue. In the past, analyses of the unsteady flows that could excite structural failure modes were performed over an array of aerodynamic conditions that encompassed likely disturbance frequencies and inter-blade phase of blade vibrations to obtain a measure of the structural damping response. However, the prescription of vibration modes, non-deforming blades, and lack of circumferential non-uniformities in geometry and thermal effects limited their accuracy. With advances in computer speed, automation, parallelization, and numerical techniques, a direct coupled approach to resonant stress/fatigue analysis is now possible. Our approach is to compute the coupled unsteady fluid, thermal, and structural fields simultaneously at points along the engine operation line and at design and off-design conditions. Airfoils are allowed to deflect under the aerodynamic and thermal loads and can include the effects of thermal coatings as well as film-cooling. The simulations will produce stress and deflection fields as well as a measure of aerodynamic damping that can be used during design to reduce or avoid structural fatigue. BENEFIT: The commercial products foreseen from this SBIR program are physics based analytical tools which would be valuable in providing a means to predict both aerodynamic forcing and aerodynamic damping in relevant geometries via a single high-fidelity calculation. These will help improving the physics-based design systems for turbine-component durability. The proposed analytical and numerical tools are applicable to commercial and military engine manufacturers in order to design airfoils for advanced demonstrator engines. If they are adopted as a standard procedure they could result in reducing the life-cycle costs. The deliverable system at the end of phase II will include software package, experimental database, and comprehensive operating procedures.