Aeroacoustics

Experimental facilities include a unique electro-pneumatic driven 165 dB aero-acoustic noise generator to simulate combustion generated pressure fluctuations. Various test sections can be placed downstream of the noise generator including simple holes, various types of acoustic damping systems, individual fuel injectors (with or without fuel) or more representative combustor sectors. Data acquisition is performed using multi-channel Kulites (acoustics), PIV, PLIF, PDA and hotwire anemometry which provide the flow field (single and two-phase) response, impedance, acoustic energy transmission and reflection.

Studies include fundamental analysis of the mechanisms by which acoustic energy can be absorbed into the flow field generated by various geometrical features followed by the design and testing of less acoustically sensitive systems. New analysis techniques have been developed to enable the acoustically generated flow field structures to be isolated from the unsteady aerodynamics flows. The improved capture of the aero-acoustic processes facilitates understanding of the flow physics and peak absorption. These techniques are now employed to assess the effects of acoustic waves on the unsteady flow field characteristics associated with fuel injectors for both single and two-phase flows.

Experimental data have also enabled the development and validation of new analytical models which simulate acoustic absorption. These models can predict the performance of new configurations much more rapidly than traditional experiments and are therefore invaluable to the design process. Additionally, CFD based methods are also being developed and validated which incorporate the correct aero acoustic boundary conditions necessary to model these complex systems.