Study of Stage Gap for a 2-bladed 2-stage Savonius-like-hydro-kinetic Turbine Performance Involving End Plates and Overlapping

Savonius-like-hydrokinetic turbine (SLHT) is a revelation for small-scale (micro/pico) power generation from perennial rivers at low water velocities and low tip speed conditions. However, for its operation at such sites, efficiency is to be improved by design modifications and flow control. This work entails a flow control strategy that combines the mean flow with overlapping flow, gap flow between stages, and flow between end plates. Here, the performance of a two-bladed two stage SLHT with end plates and 15% blade overlapping is examined in a water channel with stage gaps in mm (0-20), low water velocities in m/s (0.45-0.65) under applied braking loads in g (100-1500). The results demonstrate that SLHT produces more power and torque under a low-stage gap as the brake load rises, reaching the highest hydrodynamic torque (0.056 Nm) during a maximum load of 1250 g. The minimal stage gap is 5 mm, turbine braking loading 1250 g, 0.248 TSR, and 0.55 m/s water velocity yield the highest power coefficient (0.058), which is greater than some published SLHT designs. Thus, as much as blade profile modifications, flow control through SLHT can be the future direction for further improvement of its performance.