World Congress on Sustainable Technologies (WCST-2016) Simulation of Difuser Augmented Wind Turbine Performance Hossam M. Elbak ' , Ahmed A.A. Attia 2 , Osama Ezzat Abdelatif, M. S. Zahran Mechanical Engineering Department, Benha University,Shoubra Faculty of Engineering Cairo,Egypt Email: elbakri.eng07@gmail.com •• Ahmed.atia@feng.bu.edu.eg 2 Abstract - The main objective of this research is to optimize the diffuser design of Diffuser Augmented Wind Turbine (DA WT). Specifcally, this study investigates the effect of different shapes of diffusers to develop the suitable diffuser parameter for the wind turbine power enhancement. For that purpose, two diffuser cases have been recommended as an effective design in increasing wind speed, using a validated model of a small commercial wind turbine (AMPAIR-300) in it were developed and each case is simulated and analyzed using design sofware Solid-works and Computational Fluid Dynamic (CFD) sofware Fluent-ANSYS- 15, As per the study, for diffuser case-I,the diffuser splitter degrades the diffuser effect when its open angle higher than the diffuser open angle, for diffuser case-2 the diffuser splitter enhance the diffuser effect when its open angle lower than diffuser open angle, also adding inlet shroud directs the wind fow into the inlet of diffuser and the diffuser fange effect on the power enhancement was signifcant and also its induced axial load was signifcant, and it is recommended to study the optimum dimension of inlet shroud, diffuser fange and diffuser splitter to minimize the coefcient of thrust and to enhance the coefcient of power. Keywords: Wind Power, CFD, Augmented difser wind turbine I. INTRODUCTION Wind energy technologies have become one of the fastest growing energy sources in the world and it symbolize a virtual endless resource, however, in comparison with the growing worldwide energy demand, the scale of wind energy is still very meager, as for many causes including cost [1], [2]. Diffuser augmented wind turbine (DAMWT) have been an exciting topic in wind energy technologies since 1979, its ideology is to increase the extracted power by increasing the mass fow through the rotor, Diffser generated a sub atmospheric region at its outlet, which appears to draw more wind through the rotor compared to a bare turbine, a slight increase in wind speed can result in a large increase in power output, since wind power generation is proportional to the cube of the wind speed, Diffser augmented wind turbines have been investigated for more than ffy years as a remedy in wind industry [3]. They showed that the speed-up is not only infuenced by the thrust coeffcient but by three other coeffcients namely: shroud inlet effciency, pressure recovery coefcient, and base pressure coeffcient, all of which can be related to the shroud shape and geometry [4], [5]. They Studied the power augmentation of a small wind turbine (AMPAIR-300) shrouded with a simple fustum diffser, based on diffser length and area ratio (outlet area/inlet area) using 3D-CFD simulations, and stated that 978-1-908320-70/4/$31.00 ©2016 IEEE viscous loss in the inlet is negligible and fow separation in the diffuser leads to a signifcant performance loss, and proposed a well-designed duct as a fanged diffser that creates a large base pressure [6], [7]. They Developed the Vortec-7 DWT where multi-slotted diffuser to prevent separation was used, which has been unsuccessfl, because of the immense loading on the duct in storm conditions or in yawed fows. Also they demonstrated that the power augmentation provided by a duct could be obtained at lower cost by extending the rotor diameter. Which have been modeled at fow speed of 1 mis, an extended blade with diameter equal to the diameter of shroud exit generates the same power as the shrouded turbine [8], [6], [1]. Using CFD investigated the effect of adding fange at the diffuser exit plane, examined the optimal form of the fanged diffuser, and demonstrated that power augmentation by a factor of about four to fve, as the base pressure at the exit plane can be lowered frther due to the vortex formation at the outlet plane, the pressure down-stream of the fanged diffser turbine will be lower and hence greater fow rate is drawn into the rotor [9], [10]. They investigated the effect of diffuser with airfoil (NACAOOI5) cross section geometrical features, using CFD, to fmd the infuence of shroud geometrical features and found that fow separation of difser wall and base pressure coeffcient is the most infuential parameter in Cp, while inlet effciency has only small impact [11]. Throughout the development of diffsers for a Diffuser Augmented Wind Turbine (DAWT), computational modeling has proved to be a valuable tool. It has been used to interpret fll-scale feld results fom the Vortec 7 prototype DAWT, in an effort to fnd a difser design which is both aerodynamically effcient and can be manufactured at a reasonable cost [13]. The research presented in this paper parameterizes the power augmentation of a validated model of a small wind turbine (AMPAIR-300) shrouded with a simple fustum diffuser, the results of bare turbine simulations are compared with experimental data fom the wind turbine manufacturer and [11], This study aims to validate and analyze the two diffuser cases mentioned in table. 1, recommended fom [2] as an effective design in increasing wind speed and it is recommended to consider momentum transfer to the turbine blade to be optimized in terms of wind turbine (AMPAIR-300) power coeffcients. The difser parameter dimensions mentioned in Table 1 and Fig. 1, As the difser length presented in by Ref[2] equals to 250% of turbine rotor, which cannot be feasible to apply in simulation because of high no. of mesh elements 40