International Conference on Economic Engineering and Manufacturing Systems Braşov, 25 – 26 October 2007 RECENT, Vol. 8, nr. 3a(21a), November, 2007 331 ON THE POSSIBILITY OF IMPROVING THE WIND GENERATORS Liviu MORAR * , Dumitru POP ** , Adrian PISLA * , Camelia VLAD * * Technical University of Cluj-Napoca, Romania ** “Voievodul Gelu” College, Zalău, Romania Abstract. The article proposed an algorithm for generating sets of blades used for wind generator’s propeller. The main goal is to design and realise a 1 kW wind generator that can work with high efficiency at the specific wind condition from Romania. Since a big amount of time the wind speed is lower, usually under 3 m/s it was designed a propeller that has a starting speed of 2.7 m/s. A low Reynolds number airfoil is selected regarding to the low working speed of the propeller’s generator. This airfoil is considered the reference. Based on the airfoil, the necessary calculations are made in order to obtain all the points that will form the blade. It was analysed the influence of tip speed ratio, lift coefficient and attack angle upon the blade profile and generate two sets of blades. A Pascal software was written with which can directly build the NC files. In order to correct the influence of the radius of the cutter upon the final shape of the blade, was also implemented a procedure that will adjust the initial coordinates. For machining the blades a CNC milling machine was designed and realised. Keywords: wind generator, propeller, blade design, CNC milling machine 1. Introduction The research proposed takes in consideration the possibility of improving the wind generator efficiency. The redaction of wind speed is the one possibility. The large number of wind generators function from minimum 4 m/s of wind speed. For this purpose is very important the geometry of blade propeller, elasticity and fluid flow. The value proposed for wind speed will allowed to build wind generators on a large surface of Romania (figure 1) 2. The modelling and design of blade’s propeller A method of understanding propeller behaviour is blade element theory (BET) which is used to estimate the characteristics of propeller analytically. The inputs for analysis are chord and twist variation along the propeller radius and aerodynamic characteristics of airfoils at different blade radius. The design of horizontal axis windmills can be performed using inverse design methods, based on the minimum induced loss windmill, as defined by Glauert and Prandtl during the 1920’s. For the analysis under off-design conditions, simple blade element methods and more complex vortex lattice methods lead to accurate results. The final blade geometry can be tailored exactly to the desired main operating range by using a suitable inverse design method for the airfoil sections. For a small horizontal axis wind turbine, the main project data were proposed considering the particularities of local wind places and the Aeolian potential of Romania. The basic parameters of the windmill were a variable speed AC generator which is linked to an accumulator system. The blade angle is constant and not adjustable. The number of blades was limited to three. To achieve high yearly power regarding manufacturing costs on times, with short low Figure 1. Wind map of Romania