Low Noise High Efficiency Centrifugal Blower

Abstract

A centrifugal blower for HVACR applications includes a squirrel cage forward-curved blower fan and a scroll housing. The blower fan comprises a plurality of blades that are configured to emit air radially outward and tangentially from between the blades when the blower fan rotates at a first speed. The air so emitted has a deviation angle defined as the difference between the direction of the emitted air and the blade exit angle. The scroll housing has a spline-shaped wall that has an axial cross-section that is configured such that the deviation angle of the air emitted from the blower fan at an axial plane deviates by no more than fifteen percent circumferentially about the blower fan in-between the spline-shaped wall and the blower fan and such that the average tangential velocity of air between the spline-shaped wall and the blower fan deviates by no more than thirty percent.

What is claimed is: 
     
         1 . A centrifugal blower for HVACR applications, the centrifugal blower comprising a squirrel cage forward-curved blower fan and a scroll housing, the blower fan having a radius and being rotatable about an axis at least a first speed, the blower fan comprising a plurality of blades having a particular blade exit angle and being configured to emit air radially outward and tangentially from between the blades when the blower fan rotates at the first speed, the air so emitted having a deviation angle defined as the difference between the direction of the emitted air and the blade exit angle, the scroll housing having opposite axial sides and a spline-shaped wall extending from one of the axial sides to the other of the axial sides, the spline wall being within two times the radius of the blower fan from the axis, the spline-shaped wall having an axial cross-section that is configured such that the deviation angle of the air emitted from the blower fan at an axial plane located between the axial sides of the scroll housing deviates by no more than fifteen percent circumferentially about the blower fan in-between the spline-shaped wall and the blower fan and such that the average tangential velocity of air between the spline-shaped wall and the blower fan deviates by no more than thirty percent. 
     
     
         2 . A centrifugal blower in accordance with  claim 1  wherein the spline-shaped wall of the scroll housing has a cross-section perpendicular to the axis that remains constant between and from one of the opposite axial sides of the scroll housing to the other of the axial sides. 
     
     
         3 . A centrifugal blower in accordance with  claim 1  wherein the spline-shaped wall has an axial cross-section that is configured such that the deviation angle of the air emitted from the blower fan at the axial plane located between the side walls of the scroll housing deviates by no more than fifteen percent circumferentially more than one-hundred and eighty degrees about the blower fan in between the spline-shaped wall and the blower fan and such that the average tangential velocity of air between the spline-shaped wall and the blower fan deviates by no more than thirty percent circumferentially more than one-hundred and eighty degrees about the blower fan. 
     
     
         4 . A centrifugal blower in accordance with  claim 3  wherein the spline-shaped wall has an axial cross-section that is configured such that the deviation angle of the air emitted from the blower fan at the axial plane located between the side walls of the scroll housing deviates by no more than ten percent circumferentially more than one-hundred and eighty degrees about the blower fan in between the spline-shaped wall and the blower fan and such that the average tangential velocity of air between the spline-shaped wall and the blower fan deviates by no more than ten percent circumferentially more than one-hundred and eighty degrees about the blower fan.