Performance Enhancement of Auxiliary Air Intakes Using Vortex Generators

Abstract

The strong competition between the leading civil aircraft manufacturers Boeing and Airbus and new economical and ecological constraints have lead to new aircraft concepts and to a change of the aircraft architecture design. In particular the bleedless architecture of the more electrical aircraft promises new optimization potential. However, in the conventional aircraft architecture bleed air is generated by the compressor of the engines, in the more electrical aircraft architecture the lack of bleed air has to be compensated by additionally inducted air. Furthermore, when taking into account that the conventional centralized hydraulic system shall also be replaced by electrical actuators or local hydraulic units, then, more additional cooling air from the outside atmosphere has to be inducted to fulll the new additional cooling requirements of the equipment. The higher amount of required fresh and cooling air can only be provided by either additional air intakes or up-scaled air intakes. Both approaches have a crucial effect on the overall efficiency of the aircraft in particular in regard to the additional produced drag of the new or up-scaled air intakes. Even in the early design phase of the aircraft the air intake type has to be specified, and details of the geometrical design and the placement of air intakes have to be fixed. However, a design freeze is only possible when sophisticated evaluation techniques have been applied which guarantuee for certain intake types optimal positions in regard to performance and integration. Only then an efficiency benefit in comparison to conventional aircraft architecture can be obtained. Nevertheless, constraints might inhibit proposed locations, which, in fact, means taking into account performance losses on the air intake side. Therefore, further optimization potential has to be opened i.e. by using additional ow manipulating devices in combination with the chosen air intake. Thus, the main objective of the presented research work is to evaluate the potential of vortex generators for the enhancement of the efficiency of air intakes. In the presented work essential aspects of the air-intake design and the effect of vortex generators on the ow eld will be discussed. In particular constraints which lead to a decision for a NACA air-intake type and a certain combinations of vortex-generators will be explained. One goal of the work is to demonstrate that it is possible to use state of the art grid deformation techniques to improve the performance of such a complex aircraft system. Hereto, two congurations will be considered, one is a wind tunnel configuration, the other is an A340 like DLR F12 aircraft configuration. Results of CFD simulations for the air-intake and vortex-generator combinations will be shown and discussed. Associated fl ow phenomena will be visualized and analyzed. Finally based on the CFD results suitable vortex-generator and air-intake combinations will be evaluated and compared.