Extending on-demand noise reduction to industry-scale models for tactical aircraft

This paper summarizes a university-industry cooperative project to develop a new method of noise reduction applicable to US Navy Tactical Aircraft. The current most acute need is the reduction of the noise produced during take-off on aircraft carriers. The on-demand fluidic insert noise reduction method, pioneered at Penn State University, has the potential to be applied on next generation low bypass ratio turbofan aircraft engines. This method introduces fluidic inserts installed in the divergent wall of a CD nozzle that can be used on demand. By altering the configuration and operating conditions of the fluidic inserts, active noise reduction for both mixing and shock noise has been obtained. Substantial noise reductions have been achieved for mixing noise in the maximum noise emission direction and in the forward arc for broadband shock associated noise. A key step in the development of the methodology to ultimately use on aircraft is its extension to industry laboratory size such as that used in the GE Aviation Cell 41 Jet Noise Facility. This report describes the activities of the past year and a half to alter the original “small scale design” for successful application to industry-scale model experiments. Experiments were successfully conducted in the GE Laboratory and noise reductions were achieved that were very comparable to those previously obtained at Penn State. Extension of some of the operating parameters produced noise reductions that in some cases exceeded the comparable results at Penn State. Scaling the GE experiments to full scale aircraft engine in an aircraft carrier environment produced reductions in the A weighted spectral peaks that exceeded 7 dB.in the directions of maximum noise emission. Plans are underway to continue experiments with more parameter variations of the detailed parameters of the fluidic insert system operation.