Continuous-Scan Phased Array Measurement Methods for Turbofan Engine Acoustic Testing

ATA Engineering, Inc., (ATA) proposes an SBIR project to advance the technology readiness level (TRL) of a method for measuring phased array acoustic data for complex distributed noise sources using continuously moving (referred to here as continuous-scan, or CS) microphones in conjunction with state-of-the-art phase-referencing techniques. The proposed project aims to develop two novel modules to the existing suite of tools for CS acoustic measurements: (1) A continuous-scan beamforming (CSBF) tool for arrays located in the mid to far field to perform source diagnostics in low-SNR wind tunnel environments., and (2) An azimuthal modal decomposition tool for near-field arrays having partial azimuthal coverage, enabling acoustical holography without full source enclosure. The first module will enable small-aperture beamforming (BF) arrays to adopt the CS method, resulting in reduced maximum sidelobe levels and higher-quality BF images that approach the theoretical limits associated with the theory. The second module will enable CS near-field arrays that avoid the requirement for full coverage, greatly simplifying the array coverage requirements and making acoustical holography systems more practical in testing facilities. In Phase I, ATA will demonstrate feasibility of the methods through application to existing acoustic measurement data sets. In Phase II, the methods will be optimized and rigorously validated through experiments using small-scale turbofan engine models. Ultimately, we will transition these methods to NASA and industry stakeholders for adoption in relevant facilities.