Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download Broadband Noise Of Fans With Unsteady Coupling Theory To Account For Rotor And Stator Reflection PDF full book. Access full book title Broadband Noise Of Fans With Unsteady Coupling Theory To Account For Rotor And Stator Reflection.
| Author | : United States. National Aeronautics and Space Administration |
| Publisher | : |
| Total Pages | : |
| Release | : 2002* |
| Genre | : |
| ISBN | : |
| Author | : Donald B. Hanson |
| Publisher | : BiblioGov |
| Total Pages | : 100 |
| Release | : 2013-08 |
| Genre | : |
| ISBN | : 9781289273941 |
This report examines the effects on broadband noise generation of unsteady coupling between a rotor and stator in the fan stage of a turbofan engine. Whereas previous acoustic analyses treated the blade rows as isolated cascades, the present work accounts for reflection and transmission effects at both blade rows by tracking the mode and frequency scattering of pressure and vortical waves. The fan stage is modeled in rectilinear geometry to take advantage of a previously existing unsteady cascade theory for 3D perturbation waves and thereby use a realistic 3D turbulence spectrum. In the analysis, it was found that the set of participating modes divides itself naturally into "independent mode subsets" that couple only among themselves and not to the other such subsets. This principle is the basis for the analysis and considerably reduces computational effort. It also provides a simple, accurate scheme for modal averaging for further efficiency. Computed results for a coupled fan stage are compared with calculations for isolated blade rows. It is found that coupling increases downstream noise by 2 to 4 dB. Upstream noise is lower for isolated cascades and is further reduced by including coupling effects. In comparison with test data, the increase in the upstream/downstream differential indicates that broadband noise from turbulent inflow at the stator dominates downstream noise but is not a significant contributor to upstream noise.
| Author | : National Aeronautics and Space Adm Nasa |
| Publisher | : Independently Published |
| Total Pages | : 98 |
| Release | : 2018-09-23 |
| Genre | : Science |
| ISBN | : 9781723944666 |
This report examines the effects on broadband noise generation of unsteady coupling between a rotor and stator in the fan stage of a turbofan engine. Whereas previous acoustic analyses treated the blade rows as isolated cascades, the present work accounts for reflection and transmission effects at both blade rows by tracking the mode and frequency scattering of pressure and vortical waves. The fan stage is modeled in rectilinear geometry to take advantage of a previously existing unsteady cascade theory for 3D perturbation waves and thereby use a realistic 3D turbulence spectrum. In the analysis, it was found that the set of participating modes divides itself naturally into "independent mode subsets" that couple only among themselves and not to the other such subsets. This principle is the basis for the analysis and considerably reduces computational effort. It also provides a simple, accurate scheme for modal averaging for further efficiency. Computed results for a coupled fan stage are compared with calculations for isolated blade rows. It is found that coupling increases downstream noise by 2 to 4 dB. Upstream noise is lower for isolated cascades and is further reduced by including coupling effects. In comparison with test data, the increase in the upstream/downstream differential indicates that broadband noise from turbulent inflow at the stator dominates downstream noise but is not a significant contributor to upstream noise.Hanson, Donald B.Glenn Research CenterTURBOFAN ENGINES; ENGINE NOISE; ROTOR STATOR INTERACTIONS; NOISE MEASUREMENT; TURBULENT FLOW; SIGNAL ANALYZERS; ACOUSTIC COUPLING; SOUND TRANSMISSION; WAVE REFLECTION; BROADBAND
| Author | : |
| Publisher | : |
| Total Pages | : 98 |
| Release | : 2001 |
| Genre | : |
| ISBN | : |
| Author | : |
| Publisher | : |
| Total Pages | : 1102 |
| Release | : 2004 |
| Genre | : Government publications |
| ISBN | : |
| Author | : National Aeronautics and Space Administration (NASA) |
| Publisher | : Createspace Independent Publishing Platform |
| Total Pages | : 86 |
| Release | : 2018-06-11 |
| Genre | : |
| ISBN | : 9781721026104 |
The problem of broadband noise generated by turbulence impinging on a downstream blade row is examined from a theoretical viewpoint. Equations are derived for sound power spectra in terms of 3 dimensional wavenumber spectra of the turbulence. Particular attention is given to issues of turbulence inhomogeneity associated with the near field of the rotor and variations through boundary layers. Lean and sweep of the rotor or stator cascade are also handled rigorously with a full derivation of the relevant geometry and definitions of lean and sweep angles. Use of the general theory is illustrated by 2 simple theoretical spectra for homogeneous turbulence. Limited comparisons are made with data from model fans designed by Pratt & Whitney, Allison, and Boeing. Parametric studies for stator noise are presented showing trends with Mach number, vane count, turbulence scale and intensity, lean, and sweep. Two conventions are presented to define lean and sweep. In the "cascade system" lean is a rotation out of its plane and sweep is a rotation of the airfoil in its plane. In the "duct system" lean is the leading edge angle viewing the fan from the front (along the fan axis) and sweep is the angle viewing the fan from the side (, perpendicular to the axis). It is shown that the governing parameter is sweep in the plane of the airfoil (which reduces the chordwise component of Mach number). Lean (out of the plane of the airfoil) has little effect. Rotor noise predictions are compared with duct turbulence/rotor interaction noise data from Boeing and variations, including blade tip sweep and turbulence axial and transverse scales are explored.Hanson, Donald B.Glenn Research CenterINTERACTIONAL AERODYNAMICS; ROTORS; STATORS; CASCADE FLOW; TURBOFAN ENGINES; HOMOGENEOUS TURBULENCE; NOISE PREDICTION; ENGINE NOISE; POWER SPECTRA; LEADING EDGES; DUCTS; BROADBAND; BLADE TIPS; AIRFOILS; BOUNDARY LAYERS; MACH NUMBER; SWEEP ANGLE
| Author | : National Aeronautics and Space Administration (NASA) |
| Publisher | : Createspace Independent Publishing Platform |
| Total Pages | : 46 |
| Release | : 2018-07 |
| Genre | : |
| ISBN | : 9781722135096 |
A two dimensional linear aeroacoustic theory for rotor/stator interaction with unsteady coupling was derived and explored in Volume 1 of this report. Computer program CUP2D has been written in FORTRAN embodying the theoretical equations. This volume (Volume 2) describes the structure of the code, installation and running, preparation of the input file, and interpretation of the output. A sample case is provided with printouts of the input and output. The source code is included with comments linking it closely to the theoretical equations in Volume 1. Hanson, Donald B. Unspecified Center NAS3-25952; RTOP 535-03-10...
| Author | : National Aeronautics and Space Administration (NASA) |
| Publisher | : Createspace Independent Publishing Platform |
| Total Pages | : 34 |
| Release | : 2018-06-24 |
| Genre | : |
| ISBN | : 9781721791934 |
An experimental proof-of-concept test was conducted to demonstrate reduction of rotor-stator interaction noise through the use of rotor-trailing edge blowing. The velocity deficit from the viscous wake of the rotor blades was reduced by injecting air into the wake from a continuous trailing edge slot. Hollow blades with interior guide vanes create flow channels through which externally supplied air flows from the blade root to the trailing edge. A previous paper documented the substantial tonal reductions of this Trailing Edge Rotor Blowing (TERB) fan. This report documents the broadband characteristics of TERB. The Active Noise Control Fan (ANCF), located at the NASA Glenn Research Center, was used as the proof-of-concept test bed. Two-component hotwire data behind the rotor, unsteady surface pressures on the stator vane, and farfield directivity acoustic data were acquired at blowing rates of 1.1, 1.5, and 1.8 percent of the total fan mass flow. The results indicate a substantial reduction in the rotor wake turbulent velocity and in the stator vane unsteady surface pressures. Based on the physics of the noise generation, these indirect measurements indicate the prospect of broadband noise reduction. However, since the broadband noise generated by the ANCF is rotor-dominated, any change in the rotor-stator interaction broadband noise levels is barely distinguishable in the farfield measurements. Sutliff, Daniel L. Glenn Research Center E-15171, NASA/TM-2005-213814, AIAA Paper 2005-3028
| Author | : Harvey H. Hubbard |
| Publisher | : |
| Total Pages | : 620 |
| Release | : 1991 |
| Genre | : Aerodynamic noise |
| ISBN | : |
| Author | : |
| Publisher | : |
| Total Pages | : 980 |
| Release | : 1998 |
| Genre | : Aeronautics |
| ISBN | : |
