SBIR-STTR Award

The objective of this SBIR is to deliver an improved physics-based design system for turbine component durability by providing a means to predict aerodynamic forcing and aerodynamic damping in relevant geometries via a single high fidelity calculation. A nine-month, four-phase work plan is proposed to develop the capability for the solver Code Leo and demonstrate its use in turbine component design. Specifically, a non-linear harmonic balance analysis method coupled with an advanced transpiration boundary condition is proposed for aerodynamic damping prediction, which we believe will enable designers to gain both accuracy and speed. This capability will be validated against an existing turbine geometry and then used to modify that geometry for resonant stress reduction. During Phase I, attention will also be given to the formulation of a structural solver for Code Leo to enable fully coupled fluid/structure computations as part of Phase II. Discussions with gas turbine manufacturers indicate strong support for this type of capability for high cycle fatigue and flutter prediction. Williams International is especially interested and has provided AeroDynamic Solutions a Letter of Support for this proposal.

Benefit:
The proposed system will improve the ability for commercial and military engine manufacturers to anticipate and mitigate resonant stress-related issues during design, resulting in lower incidence of fatigue failure and improved aircraft life cycle costs. For aircraft and hovercraft engines (Air Force, NASA), the system could be used to address durability challenges common in fan and low pressure turbine designs. The system is may also be applied equally as effectivly to other sectors of the turbomachinery market, such as industrial gas turbines (HCF), automotive turbochargers (HCF) and wind turbines (flutter).

The increased demand for higher efficiency gas turbine engines is driving new designs capable of operating at higher temperatures and pressure ratios, in fewer stages, and with higher airfoil loads. These conditions pose a great challenge for turbomachinery designer systems. One particular area of challenge occurs when accounting for the strong time-varying airfoil loads produced by modern small axial gap designs. Without reliable and accurate predictions, designers can compromise the durability, reliability and performance of next generation military and commercial gas turbine engines. Developing a viable solution for estimating the dynamic stresses on the airfoil has two requirements. First, unsteady forces induced by the relative motion between vanes and blades and aerodynamic damping due to vibrating airfoils must be accurately predicted. Second, the unsteady solution turnaround time must be compressed from days to hours. In Phase I, ADS explored the feasibility of applying a Non-Linear Harmonic Balance (NHB) solution methodology for fast periodic unsteady flow problems (FA8650-13-M-2404). Results were encouraging as they showed that the NHB method has potential to provide fast and repeatable periodic unsteady flow solutions. For Phase II, ADS proposes further development and commercial release of an Advanced Unsteady Flow Solver module in ADSCFD software that gives accurate, reliable and fast predictions of unsteady aerodynamic loading on airfoil due to relative motion between blades and vanes as well as vibrations of the airfoil by itself. In addition, a Code Coupling Module will also be built and released that maps outputs from structural dynamic codes onto the CFD mesh of a vibrating airfoil surface for unsteady aerodynamic damping predictions. By combining these two modules, it will result in a system that will provide improved predictions of resonant stress for turbine components and make it possible for turbomachinery designers to quickly and accurately estimate dynamic stress levels due to blade/vane interaction during design to arrive at more durable, more reliable, and higher performance military and commercial gas turbine engines. To ensure the success of the Phase II project, ADS has assembled a world-class team to supplement the skills of Dr. Ron Ho (Bob) Ni, the principle investigator. The team includes, Mr. Gary Hilbert, a Pratt & Whitney Fellow (retired) in Aeromechanics, Structures & Dynamics, and Professor Vince Capece of the University of Kentucky, who is an expert in steady and unsteady aerodynamics as well as in fluid-structure interaction of turbomachinery.

Benefit:
With the ability to accurately and quickly predict aerodynamic loads and stresses during design, gas turbine OEMs can iterate and optimize designs without the time and cost penalties incurred by traditional ?design and test? development techniques. Strategically, this capability speeds the delivery of superior products to market, and gives gas turbine OEMs tools for achieving higher efficiencies and thrust-to-weight ratios as well as a means to combat high development costs, maturing markets and fierce global competition. High fidelity CFD simulation is widely applicable to all sectors of the turbomachinery industry, including military and commercial jet engines, industrial gas turbines and centrifugal compressors.

Keywords:
Cfd, Turbomachinery Blading, Resonance Stress Prediction, Unsteady Flow Analysis, Non-Linear Harmonic Balance, Fluid-Structure Interaction, Aerodynamic Damping