Engineers Without Borders has tasked us with a humanitarian aid mission in the Guatemalan city of Quetzaltenango where we must design a wind turbine to provide power to the citizens. However, there are specific requirements that we need to follow. The primary function of the turbine is to produce enough energy to power simple electrical devices such as LED lights. Some engineering constraints include locally sourced material accessibility, availability of wind to generate energy, and easily maintainable and long-lasting parts. Overall, we must design a unique aerodynamic wind turbine system that is durable, cost-effective, and can withstand weather variations according to the given locale criteria.
For this Project, our main objectives were to build a long lasting, simple and an energy productive turbine blade. The turbine location was in a village therefore we had to consider a design with basic structure that was easily assembled and replicated. In addition to this, we wanted a flexible and stress resistant material that was durable and cost efficient. The constraints we had were that the materials had to be sourced locally and the parts to be small so that the locals could easily carry them. For the relevant MPI of our scenario, our primary objective was to minimize production energy and our secondary objective was to minimize mass. We calculated the MPI strength and stiffness. To minimize our objectives, we followed a series of steps where we first stated the objective and constraint followed by eliminating the free variable and lastly rearranging the equation to show objectives.
We decided to select low-alloy steel because it matched our objective of being a widely available and fit within the constraints and functions of our scenario. When we used Granta Edu Pack to narrow down materials, our top two choices were carbon-fiber and low-alloy steel. We decided to go with steel instead of carbon fiber because steel is more accessible as it is a natural material, while carbon fiber is a manufactured. We also used a weighted design matrix which factored in the importance of each specification specific to our scenario, and low-alloy steel had the most points.
4 scenarios with different thickness of 15 mm, 30 mm, 50 mm and 150 mm for the blade respectively were analyzed and the deflection of each case calculated. It was noted increase in thickness resulted in a decrease in the deflection of the blade. All the calculations were compared to test out thickness level which satisfied the given turbine blade’s stiffness-limited design constraint.
8.5mm < δ < 10mm
The chosen thickness was tested for deflection simulation in Autodesk Inventor. The thickness was then adjusted repeatedly to arrive at a thickness level that resulted in blade deflection within the acceptable range. For the blade design, a thickness of 22 mm resulted in deflection of:
δ = 8.82mm < 10mm
Figure 1. Solid model of turbine blade
Figure 2. Deflection simulation on the turbine blade
