Author(s): I. C. Drula; T. Ciocan; A. Stuparu; R. F. Susan-Resiga

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Abstract: Optimizing the linear blade cascade geometry aims at achieving a prescribed flow deviation with minimum hydraulic losses. However, when using the simplified model of an inviscid incompressible fluid in steady irrotational flow one needs a different objective function to be minimized. In this paper we introduce an inviscid optimization method for two-dimensional blade cascades whereby the integral magnitude of the strain rate is minimized. We show that, within the framework of streamfunction formulation and finite element solver, this objective function is evaluated with negligible aditional computational costs. For given flow direction upstream and downstream, a cascade pitch and a blade thickness distribution we optimize the blade camberline and simultaneously determine its stagger angle. Numerical examples show that such inviscid optimal blade geometries also achieve lower hydraulic losses when assessed in viscous turbulent flow. Being numerically tractable, this method can be employed for multi-point optimization which is essential in design hydraulic turbines for a wide operating range.

DOI: https://doi.org/10.1088/1755-1315/1561/1/012020

Year: 2025