Optimizing the interplay between the chord to radius ratio, camber and pitch of cross-flow turbine blades

Abstract

This study examines the combined impact of cross-flow turbine blade geometry—specifically, the chord-to-radius ratio (c/R), blade camber, and preset pitch—on turbine performance. While prior research has examined individual effects of c/R and pitch, this work focuses on their interaction with camber and the resulting aerodynamic behaviors. Central to the analysis is the concept of virtual camber and virtual incidence, which arise from the curved trajectory of the blades and are quantified using a conformal transformation. Using two experimental datasets—one varying preset pitch, c/R, blade count, and Reynolds number, and the other examining blade camber and pitch under near-identical conditions—this work demonstrates links between blade pitch and camber influences. We propose a potential pathway for reducing the design space by combining geometric variables and coupled virtual effects into two effective parameters: net camber and net incidence. These composite variables provide a more unified and descriptive framework for understanding turbine performance and design behavior, offering a pathway for more consistent optimization of turbine geometry.