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Centrifugal Blower Double Wall Casing with Microporous Holes in Inner Casing for Reducing Noise Air Stream

IP.com Disclosure Number: IPCOM000044829D
Original Publication Date: 1984-Oct-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Maling, GC: AUTHOR [+2]

Abstract

A centrifugal blower for use with reduced noise has a double wall casing. The inner wall has small holes that allow air to pass from the fan blade chamber into a chamber between the two walls. The outer wall is rigid and is impervious to air. The holes are made small enough that energy losses occur by the mechanism of viscous absorption in the thin sheet and noise in the air stream is reduced.

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Centrifugal Blower Double Wall Casing with Microporous Holes in Inner Casing for Reducing Noise Air Stream

A centrifugal blower for use with reduced noise has a double wall casing. The inner wall has small holes that allow air to pass from the fan blade chamber into a chamber between the two walls. The outer wall is rigid and is impervious to air. The holes are made small enough that energy losses occur by the mechanism of viscous absorption in the thin sheet and noise in the air stream is reduced.

Some data processing devices have fans that blow cooling air on heat producing components. A blower transmits sound through its casing and also transmits sound through its air stream. Noise from the blower casing is commonly reduced by locating sound absorbing material around the casing.

In viscous absorption, sound causes air to flow through a small hole with a high particle velocity that produces thermo- viscous losses and thereby reduces the sound power.

The inner wall can be made of a microporous plastic about 0.032 inches in thickness. It can be supported by a frame or molded to be self supporting. The flow resistance of the porous material is on the order of 1.5 times the characteristic impedance of air, approximately 600 N-s/m3 . A suitable pore size is on the order of 50 to 100 microns.

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