Investigation of diffuser-augmented wind turbines. Part II. Technical report

Abstract

This report was prepared as an account of work sponsored by the United States Government. Neither the United States itui the United States Energy R ermch and Development Administration, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranIy. express ui ittiplied, or a:Iiumou any legal liability or responsibility for the accuracy, completeness or usefulness of any information, apparatus, product or process disclosed, or represenls lhat its usc would not infringe v,ivatcly owned rights. This report has been reproduced directly from the best available copy.

Effect of shroud on the performance of horizontal axis hydrokinetic turbines

“…Although they observed Grumman Aerospace Corporation conducted extensive research on diffuser augmented wind turbines. Their aim was to make a compact diffuser with a small length to diameter ratio and a large exit area ratio to minimize the cost (Oman et al, 1977). They worked on two types of diffusers referred to as "boundary layer control" and "ring wing" diffusers.…”

“…The baseline diffuser had an exit area ratio of 2.78 and a length to diameter ratio of 0.5 and resulted in a maximum augmentation factor of 1.89. They chose the straight wall diffuser configuration and not the one with aerofoil cross section because of its greater peak augmentation as well as its relatively simple fabrication (Oman et al, 1977). They observed the included angle and exit area ratio control the amount of flow separation in the diffuser.…”

“…No flow separation is reported inside diffuser augmented wind turbines having included angles as large as 60° (Oman et al, 1977). The turbulence and the swirl created by the rotation of the rotor blade and imparted on the wake of the rotor improve the pressure recovery of the diffuser (Clausen, 1988;Kumar and Kumar, 1980;McDonald et al, 1971).…”

Investigation of the Optimal Omni-Direction-Guide-Vane Design for Vertical Axis Wind Turbines Based on Unsteady Flow CFD Simulation

“…However, VAWTs have also some drawbacks, and possessing a low starting torque, high torque fluctuations and a complex flow are some of the issues which hold back the potential market of VAWTs. To overcome these disadvantages, some studies such as those of Chong et al [6][7][8][9], Oman et al [10], and Thomas [11], have recently introduced a device named the omni-direction-guide-vane (ODGV).…”

A comparison between ducted turbine theory and inviscid simulation

“…Research on these ducted turbines -some also known as Diffuser Augmented Wind Turbines -has a long history, with many authors attempting to develop the concept and improve wind turbine performance. Notable contributions include early work by Lilley and Rainbird [1], wide ranging investigations by Foreman et al [2][3][4] and Igra [5] and the attempted development of a full scale commercial turbine by Vortec Energy [6]. Research has continued since and several small scale ducted turbines have entered production [7].…”