الفهرس 
Applications of Inflatable Structures
Experimental work & ValidationOnly 14 pages are availabe for public view
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Abstract
The size of wind turbine blades is continuously growing in order to capture more energy from the wind. An innovative approach for the design and manufacturing large wind turbine blades is introduced. In this approach, blades are built of polymeric fabric which can be inflated to take the form of a HAWT (Horizontal Axis Wind Turbine) blade.
In order to withstand the wind loads, the blade is pressurized to increase its stiffness. Inflatable blades have the potential to overcome the drawbacks of traditional wind turbine blades. When compared to traditional blades made of fiberglass or carbon fibers, inflatable blades are lighter, less expensive, safer, easily manufacturable and transportable than traditional wind turbine blades.
This thesis starts by introducing inflatable structures, their applications and the motivation behind building an inflatable blade. Afterwards, a literature review is made to present the previous work done on inflatable structures that is related to the thesis topic. Related work includes: studying the bending behavior of inflatable beams, manufacturing of inflatable wings, and investigating different materials used in inflatable structures. An inflated wind turbine blade is then designed and tailored for Egyptian wind conditions. A NACA 0021 airfoil is selected for the inflatable blade. The wind turbine blade is designed using the Blade Element Momentum theory which helps to deduce the blade geometry and wind loads. After the design of the wind turbine, comes the phase of the inflatable blade fabrication. Beginning with choosing the inflatable fabric material, testing different fabric joining methods, then fabricating circular cross/section beams and testing their bending behavior. Afterwards, four prototypes of inflatable blade sections are manufactured and finally a full-size blade is fabricated.
In order to validate the inflatable blade concept, two inflatable blade sections are tested for geometrical accuracy. It is found that the average normalized error of the chord length and thickness are 3.37% and 1.67%, respectively. Afterwards the inflatable airfoil section is validated aerodynamically. They are tested in a wind tunnel in Chalmers university in Sweden, where the lift forces are measured using a six-component balance, while the drag forces are calculated from the wake measurements. The lift and drag coefficients are compared to those of a standard NACA 0021 airfoil. A good agreement between the inflatable and standard airfoils is observed. Moreover, the flow visualization is examined using both smoke generation and by using tufts. Measurements show that the boundary layer separation begins at an angle of attack not less than 15°, then it gradually increases to reach full stall at 25°. Moreover, the full-size blade is tested structurally by subjecting it to static bending loads representing the wind loads. Finally, the outcomes and conclusions of this study and future recommendations are presented.