||Wright-Patterson AFB, OH 454337103
|John Paul Clark
An improved understanding of internal/external flows and heat transfer under nonsteady conditions is necessary for the continued advancement of turbine engine technologies and related aircraft performance. The inability to accurately predict heat transfer of cooled and uncooled components in the hot section of turbine engines negatively impacts engine performance and the design and development costs of new engines. Furthermore, the inability to accurately predict the unsteady aerothermal forcing functions and blade loading results in the inaccurately predicted thermal or structural fatigue lifetimes, often resulted in premature failures. Increased performance, lifetime, optimized off design capabilities, increased aero/thermal/structural capability, reduced design time, and reduced cost require increased accuracy of unsteady computations, as well as experimental data for code verification and empirical models. Characterization of aerodynamic thermal and structural effects requires two- and three-dimensional computational schemes, and experimental techniques capable of spatial and temporal resolution comparable to that achievable computationally to support model development. These spatial scales/temporal resolutions need to approach wall flow scales in order to provide the accurate time-resolved blade vane interaction effects, as well as loss mechanisms and heat transfer associated with other unsteady secondary flow phenomena that are present. Unsteady shocks and shock boundary layer interactions can also play important roles.
Reductions in specific fuel consumption are largely related to our ability to increase turbine inlet temperature and cycle pressure ratio. Even with new materials, limitations are driven by the ability to cool the structures and remove or convert waste heat to a useful form. Important research areas include novel or optimized internal and external cooling of disk cavities, turbine blades, shrouds, vanes, and the resulting aerodynamic losses. Nearly all of these flows are three dimensional and unsteady, and can include nonlinear low Reynolds numbers effects such as separation and transition.
Specific experimental interests include turbine component aerodynamics and heat transfer, with special focus on three-dimensional unsteady phenomena; flow control for loss mitigation, secondary flow modification, lift improvement, and area modulation; methods to increase internal and film cooling effectiveness; techniques for increasing and decreasing heat transfer coefficients; and techniques for controlling aeroelastic effects and damping.
Specific computational interests are three-dimensional unsteady, multidisciplinary approaches that are capable of optimizing aerodynamic, thermal, and structural designs. Strong pressure gradients, density gradients, curvature, rotation, and compressive effects are present in many of these flows. Accurate Reynolds numbers effects on transition, separation, reattachment, and loss characterizations are necessary for efficient turbine performance over the operational envelope. Of particular interest are turbulence modeling and high order schemes, which specifically addresses unsteady turbine flows, and Large Eddy simulation techniques for three-dimensional rotating flows with mass addition on curved surfaces with pressure gradients.
Computational and experimental pulsed and continuous ejectors (with and without combustion) for lift/loading enhancement and flow control are of special interest, especially when combined with other flow control techniques.
Micro Optical Measurement Systems, hot wire anemometry, laser velocimetry, and particle image velocimetry are available for experimental measurements in high turbulence flows on flat plates, in cascades, and in full-scale rotating cascades. Desktop workstations and adequate computation facilities for three-dimensional computational work are available.
Turbomachinery; Three-dimensional models; Turbulent flows, computational methods; Reynolds numbers; Compressible flows; Turbojet engines; Aircraft aerodynamics; Heat transfer; Unsteady aerodynamics; Turbine engines;