Accession Number : ADA189226


Title :   Measurement and Analysis of the Noise Radiated by Low Mach Numbers Centrifugal Blowers


Descriptive Note : Doctoral thesis


Corporate Author : PENNSYLVANIA STATE UNIV STATE COLLEGE APPLIED RESEARCH LAB


Personal Author(s) : Yeager, D M ; Lauchle, G C


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a189226.pdf


Report Date : Nov 1987


Pagination or Media Count : 221


Abstract : An investigation was performed of the broad band, aerodynamically generated noise in low tip-speed Mach number, centrifugal air moving devices. An interdisciplinary experimental approach was taken which involved investigation of the aerodynamic and acoustic fields, and their mutual relationship. The noise generation process was studied using two experimental vehicles: 1) a scale model of a homologous family of centrifugal blowers typical of those used to cool computer and business equipment, and 2) a single blade from a centrifugal blower impeller which was placed in a known, controllable flow field. The radiation characteristics of the model blower were investigated by measuring the acoustic intensity distribution near the blower inlet and comparing it with the intensity near the inlet to an axial flow fan. Aerodynamic studies of the flow field in the inlet and at the discharge to the rotating impeller were used to asses the mean flow distribution through the impeller blade channels and to identify regions of excessive turbulence near the rotating blade row. New frequency- domain expressions for the correlation area and dipole source strength per unit area on a surface immersed in turbulence were developed which can be used to characterize the noise generation process over a rigid surface immersed in turbulence. An investigation of the noise radiated from the single, isolated airfoil (impeller blade) was performed using modern correlation and spectral analysis techniques. Results showed that radiation from the single blade was dominated by the effects of the incident turbulence.


Descriptors :   *BLOWERS , *IMPELLERS , ACOUSTIC FIELDS , ACOUSTIC MEASUREMENT , ACOUSTIC SIGNALS , AERODYNAMIC FORCES , AERODYNAMIC NOISE , AERODYNAMICS , AIR , AIRFOILS , AXIAL FLOW FANS , BLADES , BROADBAND , CENTRIFUGAL FIELDS , CHANNELS , COMPUTERS , COOLING , CORRELATION , DIPOLES , DISTRIBUTION , FLOW , FLOW FIELDS , FLOW VISUALIZATION , INLETS , INTENSITY , ISOLATION , MEAN , MODEL TESTS , MOTION , RADIATED NOISE , RADIATION , RIGIDITY , ROTATION , SCALE MODELS , SOURCES , SPECTRUM ANALYSIS , STRENGTH(GENERAL) , SURFACES , TURBULENCE


Subject Categories : Air Condition, Heating, Lighting & Ventilating
      Acoustics
      Fluid Mechanics


Distribution Statement : APPROVED FOR PUBLIC RELEASE