气候变化领域集成服务门户

Because of higher concerns about increasing global warming, energy consumption and reduction of conventional energy resources and growing attention are given to renewable energy and to cross flow turbines such as the Darrieus turbine to harness water energy (water currents, reservoirs, rivers, and oceans). The aim of the experimental investigation presented in this paper is to evaluate the effect of hydro Darrieus turbine blades fixation pitch angle "i(g)" on its performance. Four main sets of experimental tests were conducted for the same vertical-axis hydro turbine model (VAHT) with four blade fixation pitch angles (i(g) = -1.75 degrees, -4.5 degrees, 1.75 degrees, and 4.5 degrees), at various water flow velocities (V = 0.3-0.64 m/s corresponding to a water free flow Reynolds number of 2.5 x 10(4) to 4.36 x 10(4)). A comparison between the results of the present work and with those of a previous experimental study for i(g) = 0 degrees shows that the best performance of the tested turbine is obtained when the blades are set at a pitch angle of 1.75 degrees. In fact, the corresponding optimum mechanical power and power coefficient relative increases are respectively as much as 82% and 67% with respect to i(g) = 0 degrees at V = 0.37 m/s and as much as 65% and 77% at V = 0.46 m/s. The worst performance is obtained for the negative blades fixation pitch angle of -4.5 degrees; at the water flow velocity of 0.37 m/s, this leads to power, and power coefficient relative decreases respectively about 75% and 81% with respect to the results obtained for i(g) = 1.75 degrees and respectively about 54% and 68% of those obtained in the previous work for i(g) = 0 degrees.