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 method of making a centrifugal blower for HVACR applications, the method comprising:
 matching a scroll housing with a squirrel cage forward-curved blower fan;   placing the blower fan within the scroll housing such that the blower fan is rotatable about an axis, the blower fan having a radius and a circumference and the blower fan comprising a plurality of blades having a particular blade exit angle, the scroll housing having opposite axial sides and a spline-shaped wall, the spline-shaped wall extending axially from one of the axial sides to the other of the axial sides, the spline-shaped wall extending circumferentially over a range of scroll angles about the axis, and the spline-shaped wall being within two times the radius of the blower fan from the axis;   operatively coupling a motor to the blower fan to enable rotation of the blower fan about the axis at a first speed;   wherein the matching of the scroll housing with the blower fan comprises matching the shape of the spline-shaped wall with the blower fan such that rotation of the blower fan about the axis at the first speed causes air to be emitted from between the blades in a manner that:
 a) the emitted air at each point on the blower fan circumference within the range of scroll angles, in an axial plane located between the axial sides of the scroll housing, has an air velocity with a direction and a deviation angle, the deviation angle being defined as a difference between the direction of the air velocity and the blade exit angle, and the deviation angle at any point on the blower fan circumference does not differ from the deviation angle at any other point on the blower fan circumference by more than fifteen percent, and 
 b) the emitted air in the axial plane has an average tangential velocity in the space between the blower fan and the spline-shaped wall at each scroll angle within the range of scroll angles, the average tangential velocity being defined as an average of tangential velocities of air at points along a line extending in the axial plane at the scroll angle from the blower fan to the spline-shaped wall, and the average tangential velocity at any scroll angle does not differ from the average tangential velocity at any other scroll angle by more than thirty percent. 
   
     
     
         2 . A method of making 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 method of making a centrifugal blower in accordance with  claim 1  wherein the range of scroll angles of the spline-shaped wall extends circumferentially more than one hundred eighty degrees about the blower fan. 
     
     
         4 . A method of making a centrifugal blower in accordance with  claim 1  wherein in the matching of the scroll housing with the blower fan, the deviation angle at any point on the blower fan circumference does not differ from the deviation angle at any other point on the blower fan circumference by more than ten percent, and the average tangential velocity at any scroll angle does not differ from the average tangential velocity at any other scroll angle by more than ten percent. 
     
     
         5 . A centrifugal blower for HVACR applications produced by the method of  claim 4 . 
     
     
         6 . A method of making a centrifugal blower in accordance with  claim 1  wherein the matching of the shape of the spline-shaped wall with the blower fan comprises determining the shape of the spline-shaped wall based on airflow parameters. 
     
     
         7 . A method of making a centrifugal blower in accordance with  claim 6  wherein the airflow parameters include (i) deviation angle parameters corresponding to the blades of the blower fan, and (ii) average tangential velocity parameters corresponding to the scroll housing and the blower fan. 
     
     
         8 . A method of making a centrifugal blower in accordance with  claim 7  wherein the determining of the shape of the spline-shaped wall based on the airflow parameters comprises:
 (i) defining a multinodal spline curve as a potential shape of the spline-shaped wall; 
 (ii) evaluating the multinodal spline curve relative to the deviation angle parameters and the average tangential velocity parameters; 
 (iii) repeating steps (i) and (ii) until a convergence is obtained such that variation in deviation angles at respective points on the blower fan is maintained within a fifteen percent range, and variation in average tangential velocity at respective scroll angles is maintained within a thirty percent range, and 
 (iv) defining the shape of the spline-shaped wall based on the convergence that results from step (iii). 
 
     
     
         9 . A centrifugal blower for HVACR applications produced by the method of  claim 8 . 
     
     
         10 . A centrifugal blower for HVACR applications produced by the method of  claim 1 .