Adam J. Medd’s research while affiliated with Syracuse University and other places

As a direct response to the need for further performance gains from current multistage axial compressors, an investigation of advanced aerodynamic design concepts that will lead to compact, high-efficiency, and wide-operability configurations is being pursued. Part I of this report describes the projected level of technical advancement relative to the state of the art and quantifies it in terms of basic aerodynamic technology elements of current design systems. A rational enhancement of these elements is shown to lead to a substantial expansion of the design and operability space. Aerodynamic design considerations for a four-stage core compressor intended to serve as a vehicle to develop, integrate, and demonstrate aerotechnology advancements are discussed. This design is biased toward high efficiency at high loading. Three-dimensional blading and spanwise tailoring of vector diagrams guided by computational fluid dynamics (CFD) are used to manage the aerodynamics of the high-loaded endwall regions. Certain deleterious flow features, such as leakage-vortex-dominated endwall flow and strong shock-boundary-layer interactions, were identified and targeted for improvement. However, the preliminary results were encouraging and the front two stages were extracted for further aerodynamic trimming using a three-dimensional inverse design method described in part II of this report. The benefits of the inverse design method are illustrated by developing an appropriate pressure-loading strategy for transonic blading and applying it to reblade the rotors in the front two stages of the four-stage configuration. Multistage CFD simulations based on the average passage formulation indicated an overall efficiency potential far exceeding current practice for the front two stages. Results of the CFD simulation at the aerodynamic design point are interrogated to identify areas requiring additional development. In spite of the significantly higher aerodynamic loadings, advanced CFD-based tools were able to effectively guide the design of a very efficient axial compressor under state-of-the-art aeromechanical constraints.

A pressure-loading tailoring scheme for transonic axial compressor blading is developed with the goal of managing the passage shock in order to reduce loss and enhance stability. This loading distribution along with other prescribed quantities is employed in a 3-D viscous inverse design procedure to refine initial rotor blade geometries of an advanced 2-stage transonic compressor. Key features of this loading strategy are discussed in the context of their impact on flow structure and performance. Results are presented showing the merits of this scheme.

We present a new Lagrangian-based shock-fitting technique for inversely designing transonic turbomachinery cascade geometries. This method, which consists of a two-dimensional flowfield integrator, a camberline generator, and a passage-averaged momentum/pressure boundary condition, generates a cascade geometry to match a prescribed flow turning distribution. A complex-lamellar flow decomposition is used, first to show how discontinuous geometries are created when one's total turning distribution is specified to be continuous and shock-generated entropy gradients are present and then to construct a shock-fitting treatment that actively modifies the specified turning distribution to counter this effect. Finally, numerical results are presented to illustrate that, with this new shock-fitting approach, our transonic cascades are both geometrically continuous and faithful to the prescribed flow turning distribution.

The convergence of an inverse design technique for constructing turbomachinery cascades is presented. The turbomachinery blade geometry is defined by using flow equations and camberline equation. The results revealed that the passage-averaged flow turning distribution can be used to derive an unsteady pressure boundary condition to further accelerate calculations to a steady state.