Influence of blade chord and number on the power output and self-starting performance of twin H-type hydrokinetic turbine cluster

Recent studies on H-type hydrokinetic turbines have increasingly focused on turbine clusters to improve performance. However, the effects of blade chord length and blade number on turbine performance within clusters remain insufficiently examined. This study uses two-dimensional numerical simulations to evaluate the influence of blade chord length and blade number on turbine performance. The results show that, for an isolated turbine, an optimal blade chord length exists that maximizes power output, and turbines with fewer blades generally exhibit better performance. This behavior is mainly attributed to trailing-edge wake interference. For turbines with identical solidity, configurations with more blades experience stronger trailing-edge wake interference than those with larger blade chord lengths, which results in reduced performance. Within clusters, turbines with shorter blade chord lengths achieve greater performance enhancement, whereas turbines with a moderate blade number exhibit the maximum enhancement. These findings indicate that the effects of blade number and blade chord length on improving isolated turbine performance differ from their effects on performance enhancement within turbine clusters. Regarding self-starting behavior, larger blade chord lengths and higher blade numbers increase turbine static torque.