Development and validation of conceptual design framework for mid-size turbo-prop transport

Abstract

A turboprop aircraft is suitable for mid-range transport as it has high fuel efficiency in specific flying condition. For this reason, a mid-size turboprop aircraft has been re-drawing great interests in the design community concurrent with the growth of the airline industry. South Korea is in the process of designing and developing its own mid-size turboprop transport to keep pace with the international trend. For that purpose, we develop an in-house sizing program as a conceptual design tool and increase its accuracy by integrating high-fidelity CFD analysis into the sizing process. The reliability of the conceptual design framework is verified by analyzing the mission profile of existing turbo-prop aircraft. Moreover, a multi-level design framework is developed which sequentially employs the conceptual design framework of the sizing and the detailed design of adjoint-based optimization. First, gradient-free optimization to maximize cruise performance is carried out using the conceptual design framework with a limited number of geometric design variables to change wing planform. All the mission requirements are well-satisfied as they are imposed on the design process as the explicit form of the constraints. Second, gradient-based optimization is carried out to further detail the configuration optimized at the first level. A large number of design variables are included in this design level to minimize drag. By iterating those two levels, a more comprehensive design can be achieved with a large number of design variables while taking into account the entire mission from take-off to landing. As a result, 5.4% increase of L/D based on the inviscid drag is obtained from planform design and the sequential section design resuls in additional 3%, indicating the current design framework is successful.