Design and Analysis of an Adaptive Turbofan Engine Inlet

Abstract

The design of an turbofan inlet involves a compromise across several conflicting requirements, including low drag and low inlet distortions in high angles of attack and cross wind as well as sufficient protection against icing, bird strikes and acoustic noise and loads. Adapting or morphing the shape of the inlet could potentially enable better performance over the multiple operating points thereby saving fuel and reducing the harmful environmental impact. This paper outlines the structural design of such an adaptive inlet which features hybrid elastomeric composite materials and a means of active actuation. Since the inlet geometry features both radial and circumferential axes, any change in one axis creates a change in the other, resulting in the need of stretchable materials if unwanted steps and gaps are to be prevented for favourable laminar-turbulent transition. A fluid-structure tool is developed and presented which serves to provide both structural and aerodynamic evaluations of the adaptive design over the relevant flight operating points. This tool begins with the parameterisation of the nacelle geometry via a class-shape transformation (CST) tool which is used in both computational fluid dynamics (CFD) and finite element analysis (FEA). The goal of the development of this tool is to automate this coupling between aerodynamic and structural disciplines to be able to explore a variety of designs over the feasible design space.