Validation and assesment of lower order aerodynamics based design of Ram Air Turbines

Ram Air Turbines (RATs) are small-scale wind powered turbines installed in commercial and military aircraft to generate power for in-flight hydraulics and electronics, in the event of total power failure. There is a need for efficient design of RATs that maximizes the power by minimizing weight and cost. The Lifting Line (LL) theory is applied towards the aerodynamic analysis of a 2- bladed RAT and the approach is validated against experimental data. The goal of this paper is to demonstrate the feasibility of the LL theory as an efficient tool for conceptual design of RATs. First, the methodology is validated by reproducing an existing RAT blade design for a known operating condition. Next, off-design conditions are explored for a design point. The validation study demonstrated that the LL theory can predict aerodynamic performance of RATs within 20% up to the transonic regime. Given the simple computational implementation, cheap computational cost and observed level of accuracy the LL theory appears to be an attractive approach towards the conceptual design and design space exploration of RATs. Thus, the paper also investigates the aerodynamic design capabilities of the LL theory, given some constraints and operating condition.