Tonal Noise Radiation from an UHBR Fan { Optimized In-Duct Radial Mode Analysis

mounted sensors was applied to carry out a complete acoustic radial mode decomposition at high frequencies. In this case, Radial Mode Analysis (RMA) is in particular challenging due to the { compared to ducts of larger hub-to-tip ratios { large radial mode content. In this paper it will be shown that with the help of a regularization technique RMA results of high accuracy can be achieved with a minimized number of measurement positions. Further, the acquired test data will be used to verify that a partial RMA is feasible, which delivers the amplitudes of the dominant radial modes using the input of only a few seconds sound pressure measurements at a small number of sensor positions. In that way, i.e. the partial RMA enables an online-monitoring of the rotor-stator interaction modes. An application of the partial RMA technique is of high interest to monitor the active control of individual radial modes and respectively the assessment of the tonal sound power e.g. during fan rig accels or decels.

[1]  Philip A. Nelson,et al.  Optimal regularisation for acoustic source reconstruction by inverse methods , 2004 .

[2]  P. Nelson,et al.  Estimation of acoustic source strength within a cylindrical duct by inverse methods , 2004 .

[3]  Ulf Tapken,et al.  Optimisation of sensor arrays for radial mode analysis in flow ducts , 2006 .

[4]  Sebastien Guerin,et al.  Numerical Investigation of Geometry and Flow Effects on Acoustic Radiation from a Duct Inlet. , 2007 .

[5]  Takuro Okazaki,et al.  Axial Flow Compressor Noise , 1967 .

[6]  Graham Ashcroft,et al.  CFD/CAA Coupling Applied to the DLR UHBR-Fan: Comparison to Experimental Data , 2009 .

[7]  Ulf Tapken,et al.  Tonal Noise Radiation from UHBR Fan - Active Control of Radiation Characteristic , 2009 .

[8]  R. A. Burdisso,et al.  ACTIVE CONTROL OF INLET NOISE FROM A TURBOFAN ENGINE USING INLET WAVENUMBER SENSORS , 1999 .

[9]  Eberhard Nicke,et al.  Design of a Highly Efficient Low-Noise Fan for Ultra-High Bypass Engines , 2006 .

[10]  P. D. Joppa,et al.  Acoustic Mode Measurements in the Inlet of a Turbofan Engine , 1987 .

[11]  C. Morfey.  Acoustic energy in non-uniform flows , 1971 .

[12]  P. Nelson,et al.  ESTIMATION OF ACOUSTIC SOURCE STRENGTH BY INVERSE METHODS: PART I, CONDITIONING OF THE INVERSE PROBLEM , 2000 .

[13]  P. Joseph.  Active control of fan tones radiated from turbofan engines , 1997 .

[14]  Ulf Tapken,et al.  An investigation of low pressure turbine blade—vane interaction noise: Measurements in a 1.5-stage rig , 2009 .

[15]  C. J. Moore.  Measurement of radial and circumferential modes in annular and circular fan ducts , 1979 .

[16]  Ulf Tapken,et al.  Turbine blade/vane interaction noise: acoustic mode analysis using in-duct sensor rakes , 2001 .