Design of an UHBR Through Flow Nacelle and a Krueger Flap for the CRM-HL

Abstract

The design of a Vented Foldable Bullnose Krueger (VFBK) leading edge flap and an ultrahigh bypass ratio (UHBR) through flow nacelle as extension of the Common Research Model in High-Lift Configuration (CRM-HL) is presented. The modified model is an example of a modern, aerodynamically efficient transport aircraft in landing configuration. The design of the two modifications for the CRM-HL were performed using RANS CFD methods and were developed within the DLR project ADaMant. Special attention was paid to the mitigation of premature separations on the wing and the nacelle. Cross investigations were made, since the VFBK can also be examined with the existing NASA through flow nacelle of the CRM-HL and the UHBR nacelle can also be examined in combination with the existing slat of the CRM-HL. In addition, the aerodynamical performance of the CRM-HL and its modifications were analyzed in full-scale and as 5.2% model with the physical environmental conditions of the atmospheric low-speed wind tunnel DNW-NWB, where the model will be tested. The VFBK nearly achieves the target of providing a similar lift coefficient at maximum lift at full-scale conditions compared to the CRM-HL configuration with slat. In wind tunnel scaling and therefore at the low Reynolds number of the wind tunnel model a premature separation on the outboard VFBK prevents to achieve this goal. In contrast, the UHBR nacelle design including pylon and strake achieves a significant improvement by mitigating the flow separation on the wing and the nacelle itself. Thus, the UHBR nacelle integration achieves its goal of a comparable maximum lift coefficient in full- and in wind tunnel scaling with reference to the CRM-HL with original nacelle both in combination with VFBK and with slat.