Experimental Performance Comparison of Tubular, Modified NACA 6512, and Modified NACA 6524 Runner Configurations in a Michell–Banki Cross-Flow Turbine

Abstract

Communities in non-interconnected zones frequently lack reliable access to centralized electricity networks. Michell–Banki cross-flow turbines are attractive for decentralized generation because of their simple construction, relatively low implementation cost, and stable operation under variable discharge. This study experimentally evaluates how runner blade geometry affects turbine performance. Three runners were designed, manufactured, and tested on a closed-loop hydraulic bench: a conventional tubular blade runner, a runner with modified NACA 6512 blades, and a runner with modified NACA 6524 blades. Tests were conducted at flow rates of 10.7 and 16.3 L/s over rotational speeds from 0 to 350 rpm. Shaft power was obtained from measured torque and angular velocity, and turbine efficiency was calculated from shaft power and the total hydraulic power at the inlet. At 10.7 L/s, the tubular, NACA 6512, and NACA 6524 runners reached maximum efficiencies of 65.40%, 80.69%, and 77.69%, respectively. At the design flow rate of 16.3 L/s, the corresponding values were 74.44%, 83.37%, and 72.53%. Relative to the tubular runner, the NACA 6512 configuration improved peak efficiency by 23.4% at the lower flow rate and by 12.0% at the design flow rate. The NACA 6524 configuration improved performance at the lower flow rate but reduced peak efficiency by 2.6% under the design condition. The results demonstrate that hydrodynamic blade profiles can improve Michell–Banki turbine efficiency, but the benefit depends on matching the blade geometry to the intended hydraulic regime.