Numerical analysis of aerodynamic performance of the Ram Air Turbine in an aircraft

Abstract

A rotor design of a Ram Air Turbine (RAT) for a commercial aircraft was created taking three sections with different airfoils along the blade; those sections were assessed to evaluate their performance at different critical velocities (41, 81 and 251 m/s) and choose the best profile configuration generating a new proposal to increase the glide ratio by reducing the drag, which is helpful in emergency cases. The Blade Element Momentum (BEM) theory and Computational Fluid Dynamics (CFD) were used to analyze an initial design, then validating these results with the open software QBlade. For the BEM theory a program was created for the design and performance of the RAT adding the Viterna methodology for airfoil analysis. 16 designs were proposed by strategically interchanging wing profiles in different blade sections. These designs were analyzed by CFD, using the complete rotor and the SSTk−ω turbulence model. An optimal geometry was found, presenting a significant drag reduction of 25% generating an increase in the glide ratio and improving aircraft control in addition to maintaining the power generation above the desired values; therefore, it recommends using different airfoils for each section of a RAT's rotor blade.