Overcoming theoretical limitations in small-scale HAWT analysis: A novel experimental-data fusion approach and revelation of unsteady flow characteristics

The small-scale Wind Energy Harvester (WEH) with a Horizontal Axis Wind Turbine (HAWT) structure is a key technology for powering remote sensors, but its centimeter-scale design faces fundamental challenges: traditional Blade Element Momentum (BEM) theory fails at low Reynolds numbers, leading to significant deviations between predicted results and actual performance. This study proposes a groundbreaking analytical method that effectively integrates Blade Element Theory with experimental data to resolve the critical challenge of accurately modeling wind-to-mechanical energy conversion in small-scale HAWTs. The core innovation of this method lies in the use of experimental rotational speed data to reversely calibrate key induction factors and systematically establish a universal relationship between the induction factors and the Strouhal number. The research results not only validate the accuracy of the method but also reveal an important phenomenon: under low Reynolds number conditions, the flow field near the small-scale HAWT rotors exhibits prominent unsteady flow behavior, fundamentally distinct from the quasi-steady assumption applied to large-scale wind turbines. This discovery provides a theoretical foundation for the efficient optimization design of small-scale WEHs, significantly enhancing the reliability of performance predictions and holding practical significance for the development of micro renewable energy technologies.