CFD Investigations of Vertical Axis Wind Turbine

Abstract

The purpose of this graduation thesis is to perform and report the CFD investigations of a VAWT. There are various reasons why the research in the field of VAWTs is picking up the pace in recent times. Even though the history of VAWTs goes way back and past HAWTs, lesser efficiency is primarily the reason behind slow-paced research in field of VAWTs. Recently, the competition in viable Wind spots for HAWTs are attracting more researchers and companies to pick up the slack in research for VAWTs. There are numerous Objectives outlined in this Thesis. The most crucial and important ones are, studying the effects of Constant Pitching, deriving an equation for Optimized Pitching and ultimately applying this Pitching approach to Multi-Blade Rotor System. The comparisons are drawn between Unpitched system and Literature, wherever similar research is found. Some of the other objectives of the thesis are, Understanding the operating principles and CFD approaches for Simulating VAWTs from Literature, comparing the effects of the Mesh Quality on Torque in CFD analysis and comparing the type of Analysis approach used for Simulation. The above stated objectives are achieved in different stages with different Geometry, meshes, Boundary conditions. Each study is tailor made to achieve a specific objective. In order to understand the effects of different Pitching angles on Torque, numerous Solver Definition files are generated each with a specific Blade pitch angle in place. The results are then compared, and an Optimum pitching angle equation is created. The equation so created is utilized in next study, where the geometry is modified to include two blades instead of one and the results of the Optimized Pitching are reported. The mesh is varied in ICEM CFD to alter the number of elements and hence the quality of mesh and results are reported as well. The results of this thesis are in accordance to what is expected from such an approach. There is an in increase in the amount of Torque generated by the rotor system when Variable Pitching is applied. There is an increase of 52.8% in case of Single blade system and an increase of 48.2% in case of two-bladed system. This increase validated the utility of the equation generated to optimize the pitching angle. 66 This research is a one of its kind with no complete resemblance to any other Literature and as with any other research, there is a lot of future scope in order to expand it. Some of the future research opportunities lie in the validation of the Pitching results by corroboration with experimental setup such as Wind tunnel studies on prototype or actual live-scale model. Another aspect of future research would be to perform the same approach on different number of Blades in a rotor system. As reported, the effect of increasing number of blades can cause Turbulent flow if TSR is not optimized. So, this would be an interesting research topic. Another valid and an important future extension of this research would be to complete a full-fledged 3-D study instead of a Quasi-2D approach and study the effects of constant and variable pitching. This would be highly time expensive and require a huge computational power. But such a study would be as close as possible to reality of an actual Wind Tunnel. Another suggestion for future scope would be to incorporate different Airfoil types, Symmetrical and Asymmetrical to study the effects of Variable pitching on different Airfoils.