Aerodynamic testing of helicopter novel air intakes

Aerodynamic engine integration with respect to emission reduction is one key issue of rotorcraft design in classical transport missions. This paper deals with experimental investigations and aerodynamic optimization of engine side air intakes of a lightweight helicopter aiming to improve aerodynamic engine integration. For this purpose, comprehensive wind tunnel tests are performed on a novel full scale model of a helicopter fuselage section at the Chair of Aerodynamics and Fluid Mechanics of the Technical University of Munich (TUM-AER). To simulate engine mass flow rates corresponding to realistic helicopter operation conditions the new wind tunnel model incorporates a duct system, venturi meter and a radial fan. A rake of 5-hole pressure probes is employed to obtain a total pressure ratio and distortion coefficient as aerodynamic evaluation parameters at the Aerodynamic Interface Plane (AIP). For different air intake variants, namely a "static" side intake, a "semi-dynamic" side intake as well as a "dynamic" side intake including a scoop, significant trends in dependence of mass flow rate and freestream velocity are determined. Based on the results of three baseline variants, retrofit geometric solutions are developed such as a rear spoiler and an inlet guide vane, which fit the baseline 2 intake geometry. The best retrofit solutions are presented and their aerodynamic characteristics are compared to the baseline variants.