Session: 37-02 CFD Solver Methods

Paper Number: 84035

84035 - New Concept for Design in Turbomachinery Applications using Full RANS Gradient Methodology 

Radial compressors and turbomachines in general were historically designed for a limited operation range around the BEP (Best Efficiency Point) and the focus was manly oriented towards the impeller geometry. The vaned diffuser geometry has been usually rather simple, with prismatic blades or wedges, despite to the fact that the impeller outflow is quite distorted.

In order to extend the operating range of radial compressors it makes therefore sense to include modifications of the basic geometry of the diffuser. A condition to perform such improvements is to obtain a detailed understanding of local flow structures at off-design conditions, requiring robust flow solvers with mixing-plane and advanced turbulence modelling capabilities.

In recent years PEW (Profiled End Wall) modifications in the diffuser were performed, mainly based on a manual trial-and-error approach and showing considerable potential for improvements. To accelerate the process and to allow automation, which is crucial in industrial applications, it is suggested to use an Adjoint-based optimization algorithm for shape optimization.

In this study a discrete Adjoint solver implemented into a robust CFD framework based on a coupled pressure-based solver is used. The method allows the calculation of the gradient of an objective function with respect to predefined physical parameters. The geometric parameter space is thereby not restricted. Automatic differentiation is used, which allows flexibility also with respect to turbulence modeling. For mesh morphing direct deformation of the surface mesh or FFD (Free Form Deformation) with simple and fast set-up procedure is available.

The proof of concept will be performed on the RWTH Aachen “Radiver” centrifugal compressor case with vaned diffuser. The goal is to have a more favorable machine characteristic with extended operation range.

Presenting Author: Armando Del Rio Lucerne University of Applied Sciences and Arts

Presenting Author Biography: Armando Del Rio graduated in Mechanical Engineering at Lucerne University of Applied Sciences and Arts.<br/>He is working since 2016 in the Competence Centre of Fluid Mechanics and Numerical Methods at the Lucerne University of Applied Sciences and Arts, where he is currently employed as a research associate.

Authors:

Armando Del Rio Lucerne University of Applied Sciences and Arts
Ernesto Casartelli Lucerne University of Applied Sciences and Arts
Benno Fleischli Lucerne University of Applied Sciences and Arts
Luca Mangani Lucerne University of Applied Sciences and Arts