Title of Project: Supersonic Business Jet Applications
Project PIs: S. Heister (PI), G. Blaisdell (co-PI), W. Crossley (co-PI), A. Lyrintzis (co-PI), C. Merkle (co-PI),
Project goals and description of work: (for Tasks 4 and 8)
[Task 4] Operating behind a supersonic inlet the fan of an SSBJ engine will experience flow distortion characteristics quite different to those of a conventional turbofan installation. The distortion may cause a considerable increase in fan source noise, which could become a significant source in overall aircraft noise, especially during landing. The effect of large inflow distortions may need to be addressed using a nonlinear CFD methodology. The study will investigate fan noise issues, including how inlet distortion may affect buzz saw noise from the fan, i.e. tones at multiples of fan rotation produced by non-uniform leading edge shock spacing on the fan leading edge. We propose to use the BASS code currently being developed at NASA Glenn as part of the QAT (Quiet Aircraft Technology) program. The code has been designed for aeroacoustic applications and has several high-order schemes. We will carry out a generic parametric investigation into the response of fan source noise to different distortion profiles (radial, circumferential) before evaluating the effect of more specific distortion characteristics.
[Task 8] The noise emissions of nozzles with internal mixers and ejectors employing geometry and conditions used for the new Rolls-Royce engine of the proposed supersonic business jet is being studied. The main objectives are to examine the effects of forced mixer and ejector design on the noise generation mechanisms, and to develop novel noise attenuation concepts. In our previous studies (in collaboration with Rolls-Royce and ISVR researchers), the noise from internal mixers was investigated based on a RANS approach coupled with semi-empirical models (i.e., the two-source model). We have analyzed experimental results obtained at NASA Glenn. We have also developed a high-order LES code for jet noise prediction and integral acoustics techniques for the computation of the noise signal. We are studying the flow with mixers and ejectors. The ejector will add additional dipolar noise sources; thus the existing two-source model will be extended to a multi-source model to capture the emissions from various nozzle components. Additional noise sources, advanced noise control concepts, and other possible model modifications and enhancements will be investigated. In particular, the feasibility of combining variable geometry features with dynamic actuators for the active suppression of the radiated noise at low frequency will be investigated, along with passive methods such as the use of sound absorption treatments for the high frequencies.