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What is robust design optimization (RDO), and is it better than standard optimization? In this customer case, we describe a multi-disciplinary optimization of a turbocharger compressor from FORD Motor Company, in which we demonstrate it is.
RDO combines standard numerical optimization with sensitivity analysis to take into account the influence of manufacturing variations and operating uncertainties on product performance early in the design process. This type of CFD optimization enables engineers to find optimal designs that are less sensitive to these uncertainties, giving more stable performance results.
This Ford turbocharger optimization case aimed to extend the compressor’s flow capacity and improve surge margins. We used an active self-recirculation casing treatment.
Given their varying geometries, we created two separate meshes for the points near the choke and the stall with Fidelity Automesh. The simulation domain consisted of the impeller, a vaneless diffuser, the self-recirculation casing and the volute for fluid flow simulation (CFD), and the solid blade with a back plate for structural simulations (CS). Fidelity Optimization was used to run the optimization on the impeller shape.
The design space consisted of 19 design variables, performed as multi-point optimizations, and three operating points on two different speed lines. The robust optimization accounted for the following uncertainties:
Comparing the performances of Deterministic Design 1 and Robust Design 1, we learned that the mean values of choke mass flow and efficiency varied in a similar range. However, the standard deviations of these objectives were drastically reduced by the robust design only.
Mean values of choke mass flow and efficiency vary in a similar range
Standard deviations of choke mass flow and efficiency were drastically reduced by the robust designs only
The resulting blade designs were also notably different:
Accounting for uncertainties in the optimization process resulted in designs that are less sensitive to uncertainties. The standard deviation of the choke mass flow was reduced by 33% and the efficiency by nearly 48% in the robust design, leading to significantly more performance stability.
You may also be interested in Fluid-Structure Interaction (FSI) modeling. If you are, make sure not to miss this webinar: