Efficiency optimization of twin helical hydrokinetic turbines based on the Taguchi method

Abstract

The influence law of different design parameters on the output power of the turbine is explored in this paper to improve the output power of twin-rotor vertical axis helical turbines. Taguchi method is used to analyze five parameters that affect the efficiency of the twin-rotor helical turbine:airfoil, pitch angle, envelope ratio, spacing ratio, and rotation direction at four levels. A five-factor and four-level orthogonal table is built to calculate the conditions in the orthogonal table numerically. Results show that the optimized efficiency of twin vertical axis helical hydrokinetic turbines is 22.86% higher than that of the initial design turbine. The effect of each parameter on the efficiency of the turbine is in order of profile > pitch angle > spacing ratio > enwinding ratio > rotation direction. The best combination of five parameters is A4 (0024), B3 (3°), C1 (1.00), D4 (- -), and E2 (1.6). The canyon effect is the main reason for improving the efficiency of twin vertical axis helical hydrokinetic turbines. The interference of twin helical hydrokinetic turbines to the flow of the tail vortex is strong; therefore, the arrangement of turbines should utilize this feature reasonably. The results of this study can provide a reference for the optimal design of vertical axis turbines.