Mechanical Design, Analysis, and Manufacturing of Wind Tunnel Model and Support Structure

Sammanfattning: This volume covers the phases from design to manufacturing of a wind tunnel test support structure for a conceptual blended wing-body UAV designed by KTH Green Raven Project students. The innovative aircraft design demonstrates sustainability within aviation by utilizing a hybrid electric-fuel cell propulsion system. The wind tunnel test to be conducted at Bristol University will produce data to evaluate the aerodynamic properties of the model for design verification. The wind tunnel model is a small-scaled 1.5m-span model supported by struts that change the pitch and yaw angles during testing. An external force balance provided by Bristol University measures the loads and moments experienced by the model. The main requirements for the structure are to withstand the aerodynamic loads imposed by the model and to change the model's orientation while maintaining wind speed during the test. The maximum aerodynamic loads were provided in a matrix, the largest of which was used as the load condition for the support equating to a 512N lift at 14 degrees AOA. Trade studies were conducted to determine the mechanisms to satisfy the requirements while staying within budget. The chosen design for the support structure includes a circular base plate constrained by a locking ring with positioning pins to change the yaw angle. The main strut is mounted at the the center of the circular base plate. A hinge bracket at the top of the strut interfaces with another hinge bracket within the model via a clevis pin. An electric linear actuator mounted downstream of the main strut is used to vary the pitch angle, with the center of rotation at the clevis pin. Once the design was finalized, finite element analysis was done to verify the structural stability of the design. The FEA results were compared to Euler-Bernoulli approximations for deflection. Manufacturing of the components was out-sourced while assembly and programming of the actuator was done in-house.