Response surface modeling of a small crossflow hydro turbine rotor

This paper presents the progress made in works aiming to design a modular low cost cross-flow turbine runner that is compatible with mass production. In an earlier study, stress and weight optimization analyses had been presented for a common runner design. This work includes analyses on segmented modular runner design iteration. Obtaining a closed form analytical formulation for complex mechanical structures such as turbine rotors with multiple blade assemblies can be very problematic. Building a prototype without optimizing the structural stress levels may result in unnecessary hardware costs. In this work, mathematical models for highest stress or lowest factor of safety on critical components of a small modular cross-flow hydro turbine rotor have been explored for various design options through a response surface analysis. The response surface model is obtained based on finite element analysis results following design of simulated experiments. Rotor design parameters have been investigated to optimize factor of safety on critical components without violating the specified weight limits. Box-Behnken data tables have been used to obtain the response surface model. The attained response model yields the maximum stress and lowest factor of safety for critical rotor components for various combinations of design parameters. Verification runs indicate that response model successfully predicts factor of safety levels close to finite element calculations.