Optimization of the “S” characteristics of a pump-turbine with splitter blades utilizing bionic guide vanes

<p indent="0mm">The S-shaped characteristics of the performance curve of the turbine working model considerably impact the performance and stability of the pump-turbine. Here, we design bionic guide vanes inspired by the flipper of the humpback whale to improve the “S” characteristics of the pump-turbine. The results indicate that the bionic guide vane, derived from the mid-span cross-section of the flipper, is most effective for improving the “S” characteristics of the pump-turbine. The instability interval characterized by the infection points on the S-shaped performance curve is reduced by approximately 75%. The preferred bionic guide vanes can stabilize the flow in the guide vane region and the vaneless space where the area of the high-speed water ring and the number of vortex structures are increased. Moreover, in terms of energy characteristics, the preferred bionic guide vanes suppress the wake flow of the guide vane and the inter-blade vortex in the runner region under turbine design conditions, thereby, reducing the total production rate of the entropy in the stay vane, guide vane and runner region by 26.6% and ultimately improving the maximum efficiency by 2.1%. However, under pump design conditions, the bionic guide vanes aggravate the flow pattern in the stay vane region, thereby decreasing the maximum efficiency by 1.0%.