Analysis of liner performance using the NASA Langley Research Center Curved Duct Test Rig

Abstract The NASA Langley Research Center Curved Duct Test Rig (CDTR) is designed to test aircraft engine nacelle liner samples in an environment approximating that of the engine on a scale that approaches the full scale dimensions of the aft bypass duct. The modal content of the sound in the duct can be determined and the modal content of the sound incident on the liner test section can be controlled. The effect of flow speed, up to Mach 0.5 in the test section, can be investigated. The results reported in this paper come from a study to evaluate the effect of duct configuration on the acoustic performance of single degree of freedom (SDOF) perforate-over-honeycomb liners. Variations of duct configuration include: asymmetric (liner on one side and hard wall opposite) and symmetric (liner on both sides) wall treatment; inlet and exhaust orientation, in which the sound propagates either against or with the flow; and straight and curved (outlet is offset from the inlet by one duct width) flow path. The effect that duct configuration has on the overall acoustic performance is quantified. The redistribution of incident mode content is shown, in particular the mode scatter effect that liner symmetry has on symmetric and asymmetric incident mode shapes. The Curved Duct Test Rig is shown to be a valuable tool for the evaluation of acoustic liner concepts.

[1]  Daniel L. Sutliff,et al.  Active Control of Low-Speed Fan Tonal Noise Using Actuators Mounted in Stator Vanes: Part III Results , 2003 .

[2]  P. Joppa.  An acoustic mode measurement technique , 1984 .

[3]  W. R. Watson,et al.  Comparison of measured and calculated mode redistribution associated with spinning mode transmission through circumferentially segmented lined ducts , 1983 .

[4]  Michael G. Jones,et al.  Report on Recent Upgrades to the Curved Duct Test Rig at NASA Langley Research Center , 2011 .

[5]  L. Homyak,et al.  Acoustic performance of inlet suppressors on an engine generating a single mode , 1981 .

[6]  D. L. Palumbo,et al.  An operations manual for the Spinning Mode Synthesizer in the Langley Aircraft Noise Reduction Laboratory , 1981 .

[7]  Willie R. Watson,et al.  Uncertainty and Sensitivity Analyses of a Two-Parameter Impedance Prediction Model , 2008 .

[8]  David Alan Bies,et al.  Propagation of sound in a curved bend containing a curved axial partition , 1978 .

[9]  A. V. Saule,et al.  Analysis of radiation patterns of interaction tones generated by inlet rods in the JT15D engine , 1979 .

[10]  W. R. Watson.  An evaluation of circumferentially segmented duct liners , 1983 .

[11]  Carl H. Gerhold,et al.  Configuration Effects on Liner Performance , 2012 .

[12]  Brian J. Tester,et al.  The propagation and attenuation of sound in lined ducts containing uniform or “plug” flow , 1973 .

[13]  R. J. Silcox.  Experimental investigation of geometry and flow effects on acoustic radiation from duct inlets , 1983 .

[14]  Carl H. Gerhold,et al.  Advanced Computational and Experimental Techniques for Nacelle Liner Performance Evaluation , 2009 .

[15]  R. J. Silcox,et al.  Experimental investigation of the radiation of sound from an unflanged duct and a bellmouth, including the flow effect , 1980 .

[17]  C. L. Morfey,et al.  Sound transmission and generation in ducts with flow , 1971 .

[18]  Bruce N. Walker,et al.  Active Control of Low-Speed Fan Tonal Noise Using Actuators Mounted in Stator Vanes Part 2: Novel Error Sensing Concepts , 2003 .

[19]  Ricardo A. Burdisso,et al.  Time-Averaged Active Controller for Turbofan Engine Fan Noise Reduction , 1996 .

[20]  R H Thomas,et al.  A Mode Detection Method Using the Azimuthal Directivity of a Turbofan Model , 1999 .

[21]  Scott D. Sommerfeldt,et al.  Active Control of Low-Speed Fan Tonal Noise Using Actuators Mounted in Stator Vanes: Part 1 Control System Design and Implementation , 2003 .

[22]  R. E. Kraft,et al.  Design and performance of duct acoustic treatment , 1991 .

[23]  Douglas M. Nark,et al.  Improved Inlet Noise Attenuation by Alteration of Boundary Layer Profiles , 2004 .

[24]  D. Chestnutt,et al.  Survey of inlet noise reduction concepts for gas turbine engines , 1976 .

[25]  Edmane Envia,et al.  Fan Noise Reduction: An Overview , 2002 .

[26]  Leo L. Beranek,et al.  Noise and vibration control , 1971 .

[27]  Carl H. Gerhold,et al.  Configuration Effects on Acoustic Performance of a Duct Liner , 2008 .

[28]  Willie R. Watson,et al.  Investigation of Liner Characteristics in the NASA Langley Curved Duct Test Rig , 2007 .

[29]  Harold C. Lester,et al.  Sound Propagation Through a Variable Area Duct: Experiment and Theory , 1982 .

[30]  Carl H. Gerhold,et al.  Development of an Experimental Rig for Investigation of Higher Order Modes in Ducts , 2006 .

[31]  Carl H. Gerhold,et al.  Active Control of Fan-Generated Tone Noise , 1997 .

[32]  Willie R. Watson,et al.  Comparison of Two Waveguide Methods for Educing Liner Impedance in Grazing Flow , 2004 .

[33]  K. J. Baumeister,et al.  Optimization of suppression for two-element treatment liners for turbomachinery exhaust ducts , 1976 .

[34]  R. Burdisso,et al.  Experiments on the active control of inlet noise from a turbofan jet engine using multiple circumferential control arrays , 1996 .

[35]  Carl H. Gerhold.  Determination of fan inlet duct mode structure using in‐duct microphone array measurement , 2001 .

[36]  P. Vaidya,et al.  The state of the art of duct acoustics , 1977 .

[37]  T. G. Sofrin,et al.  Modal propagation angles in a cylindrical duct with flow and their relation to sound radiation , 1979 .

[38]  Willie R. Watson,et al.  Effects of Liner Geometry on Acoustic Impedance , 2002 .