Validation of the DLR dual stream jet noise test rig at the Aeroacoustic Wind Tunnel Braunschweig

Kurzfassung

Since its refurbishment in 2019, DLR's dual stream jet noise test rig has seen many long cowl and short cowl experiments powered by the DNW-NWB 1.4MW screw compressor air supply (3kg/s, 6bar.g). The tremendous jet diameters of 80-100mm enable the installation of well-sized wing models, but cause a rather large (i.e. non-pointwise) source distribution in the mid-sized test room. The knowledge of the source distribution allows AWB to achieve good comparison of their Rmic/Djet=20 data to conventionally measured large-scale far-field data (Rmic/Djet=100), to build advanced engine models and to optimize its instrumentation for testing large models in small test rooms. The rig capabilities and limits due to engine model size (using jet diameters of 31.5mm, 50mm, 80mm) as well as internal and external rig noise were recently determined and evaluated with help of contemporary evaluation techniques. All in all, this presentation is meant to help understand how to design a test and the instrumentation for large models in small test rooms, considering the limitations of the test facility.