On the design of propeller hydrokinetic turbines: the effect of the number of blades

Abstract

A design study of propeller hydrokinetic turbines is explored in the present paper, where the optimized blade geometry is determined by the classical Glauert theory applicable to the design of axial flow turbines (hydrokinetic and wind turbines). The aim of the present study is to evaluate the optimized geometry for propeller hydrokinetic turbines, observing the effect of the number of blades in the runner design. The performance of runners with different number of blades is evaluated in a specific low-rotational-speed operating conditions, using blade element momentum theory (BEMT) simulations, confirmed by measurements in wind tunnel experiments for small-scale turbine models. The optimum design values of the power coefficient, in the operating tip speed ratio, for two-, three-and four-blade runners are pointed out, defining the best configuration for a propeller 10 kW hydrokinetic machine.

On the upscaling approach to wind tunnel experiments of horizontal axis hydrokinetic turbines

“…As reported by the works [41,45] BEM methods trend to over-predict the C p × curves in turbines in regions not close to the nominal operating region. Figure 12 shows CFD and experimental results for the free-flow speeds used in the wind tunnel tests (8,10, and 12 m/s). As presented in Fig.…”

“…Data from simulations of the hydrodynamics and the electromechanical systems of this hydrokinetic turbine have been reported by [38,40,46,47]. The experimental study was conducted for a small-scale turbine model of 1/20th of real dimensions to better represent the dominant scenario of the wind tunnel laboratories, worldwide [4,8,12,24]. For the model, the same profile already defined was employed to keep the geometric similarity between both machines.…”

“…The polar curves ( C L = C L ( , Re L ) , and C D = C D ( , Re L ) ) as a function of attack angle, , and local Reynolds number, Re L , are computed employed the XFOIL tool at the low Reynolds number ( ∼ 10 4 ) for the model, and high Reynolds number ( ∼ 10 6 ) for full-size prototype turbine. In order to compute the local Reynolds number in each blade section, it is necessary to calculate the rotational velocity of the rotor, the tangential velocity in the blade radial position and the induction factors, involving polar curves, in an iterative process [8,9]. The BEM method applied to a rotor geometry under specific operating conditions can estimate, beside hydrodynamical forces and moments, the power coefficient as in Eq.…”

Fatigue life estimation of hydrokinetic turbine blades

“…The blade element theory (BET) is widely used in the design of wind and hydrokinetic turbines [6]. In this method, the blade is sectioned into multiple parts along its length, as shown in Fig.…”

“…Thus, there is a need to develop other forms of energy generation which have low environmental impact, such as hydrokinetic energy (energy from water streams). As stated in [2][3][4][5][6], hydrokinetic technology offers several advantages over traditional forms of hydraulic generation, for example, the possibility of not using dams.…”