Mixing device for mixing fuel and air and furnace with a mixing device

Abstract

Mixing devices for mixing fuel and air for a premix burner or furnace and furnaces (e.g., premix) with mixing devices. Furnaces may be for heating an occupied space, and may produce lower NOx emissions. A mixing device may be located within an inlet tube, may have a surface that is perpendicular to the direction of fuel flow or that forms a circle, or may have two surfaces held at substantially opposite angles to induce swirl. A portion of the mixing device may extend over an orifice of the fuel injector. A mixing device may be attached to the fuel injector, may be made from a piece of sheet metal, and may have a hole for attachment to the fuel injector. Mixing devices may have a center, two arms, and two ends, which may be separated by bends. A burner plate may be sandwiched between surfaces to allow for expansion.

1 . A furnace for heating an occupied space, the furnace comprising:
 an air inlet passage comprising an inlet tube having an inlet end;   a fuel injector mounted at the inlet end of the inlet tube, the fuel injector comprising an orifice that dispenses the fuel, wherein the fuel injector is oriented so that the fuel injector dispenses the fuel into the inlet end of the inlet tube, and wherein space between the fuel injector and the inlet tube permits air to enter the inlet tube around the fuel injector;   a mixing device downstream of the fuel injector that mixes the air and fuel prior to combustion, wherein the mixing device is in addition to the inlet tube and the mixing device is located inside the inlet tube;   a burner plate downstream of the mixing device separating unburned air and fuel mixture on an upstream side of the burner plate from burning air and fuel and products of combustion on a downstream side of the burner plate, the burner plate comprising multiple ports therethrough that the air and fuel mixture pass through;   a combustion chamber downstream of the burner plate and defined on an upstream side by the burner plate;   a heat exchanger downstream of the combustion chamber that transfers heat from the products of combustion to air to be delivered to the occupied space; and   a fan downstream of the heat exchanger that draws air through the air inlet passage, mixing device, burner plate and combustion chamber, and that draws products of combustion through the heat exchanger.   
     
     
         2 . The furnace of  claim 1  wherein the mixing device comprises a surface that is substantially perpendicular to the direction of fuel flow exiting the injector and that is located in front of the orifice of the fuel injector. 
     
     
         3 . The furnace of  claim 2  wherein the surface of the mixing device substantially forms a circle. 
     
     
         4 . The furnace of  claim 1  wherein the mixing device comprises multiple surfaces that are held at angles so as to induce swirl in the inlet tube. 
     
     
         5 . The furnace of  claim 1  wherein the mixing device comprises multiple surfaces that are located downstream of the orifice of the fuel injector that are held at angles inducing swirl in the fuel being dispensed from the orifice of the fuel injector and inducing swirl in the air, whereby mixing of the fuel and the air is promoted. 
     
     
         6 . The furnace of  claim 1  wherein the mixing device comprises a piece of sheet metal comprising multiple bends. 
     
     
         7 . The furnace of  claim 1  wherein the mixing device comprises a hole that attaches the mixing device to the fuel injector. 
     
     
         8 . The furnace of  claim 1  wherein the mixing device comprises a center and two arms extending from the center to two ends, wherein each arm is separated from the center by a first bend, and wherein each end is separated from one of the arms by a second bend. 
     
     
         9 . The furnace of  claim 1  wherein the burner plate is attached by being sandwiched between opposing surfaces so that the burner plate slides against the opposing surfaces when the burner plate expands and contracts as the furnace cycles on and off. 
     
     
         10 . The furnace of  claim 1  wherein the mixing device comprises:
 a center; 
 a first end; 
 a second end; 
 a first arm extending from the center to the first end, the first arm having a first arm length extending from the center to the first end; 
 a second arm extending from the center to the second end, the second arm having a second arm length extending from the center to the second end; 
 a first bend between the center and the first arm; 
 a second bend between the center and the second arm; 
 a third bend between the first arm and the first end; and 
 a fourth bend between the second arm and the second end; wherein: 
 the center, the first end, the second end, the first arm, and the second arm all have a common thickness; 
 the center has a center width that is perpendicular to the first arm length, to the second arm length, and to the thickness of the center; 
 the first end has a first end width that is perpendicular to the first arm length and to the thickness of the first end; 
 the second end has a second end width that is perpendicular to the second arm length and to the thickness of the second end; 
 the first arm has a first arm width that is perpendicular to the first arm length and to the thickness of the first arm; 
 the second arm has a second arm width that is perpendicular to the second arm length and to the thickness of the second arm; 
 the center width is greater than the first arm width; 
 the center width is greater than the second arm width; 
 the first end width is greater than the first arm width; and 
 the second end width is greater than the second arm width. 
 
     
     
         11 . A mixing device for mixing fuel and air for a premix burner, the mixing device comprising:
 a center;   a first end;   a second end;   a first arm extending from the center to the first end, the first arm having a first arm length extending from the center to the first end;   a second arm extending from the center to the second end, the second arm having a second arm length extending from the center to the second end;   a first bend between the center and the first arm;   a second bend between the center and the second arm;   a third bend between the first arm and the first end; and   a fourth bend between the second arm and the second end; wherein:   the center, the first end, the second end, the first arm, and the second arm all have a common thickness;   the center has a center width that is perpendicular to the first arm length, to the second arm length, and to the thickness of the center;   the first end has a first end width that is perpendicular to the first arm length and to the thickness of the first end;   the second end has a second end width that is perpendicular to the second arm length and to the thickness of the second end;   the first arm has a first arm width that is perpendicular to the first arm length and to the thickness of the first arm;   the second arm has a second arm width that is perpendicular to the second arm length and to the thickness of the second arm;   the center width is greater than the first arm width;   the center width is greater than the second arm width;   the first end width is greater than the first arm width; and   the second end width is greater than the second arm width.   
     
     
         12 . The mixing device of  claim 11  wherein the first bend plus the second bend equals 180 degrees and the third bend plus the fourth bend equals 180 degrees. 
     
     
         13 . The mixing device of  claim 11  wherein the first arm length is greater than the first arm width and the second arm length is greater than the second arm length. 
     
     
         14 . The mixing device of  claim 13  further comprising a hole through the thickness and wherein the mixing device is made of sheet metal, the first bend plus the second bend equals 180 degrees, and the third bend plus the fourth bend equals 180 degrees. 
     
     
         15 . A mixing device for mixing fuel and air in a premix furnace, the mixing device comprising first portion comprising a hole through the first portion of the mixing device that attaches the mixing device to a fuel injector; and a second portion of the mixing device, which, when the mixing device is attached to the fuel injector, extends over an orifice of the fuel injector. 
     
     
         16 . The mixing device of  claim 15  further comprising at least one arm that extends from the first portion to the second portion. 
     
     
         17 . The mixing device of  claim 16  further comprising a first bend between the at least one arm and the first portion and a second bend between the at least one arm and the second portion. 
     
     
         18 . The mixing device of  claim 17  wherein the first bend plus the second bend equals 180 degrees. 
     
     
         19 . The mixing device of  claim 17  wherein the least one arm comprises a first arm and a second arm that each extend from the first portion to the second portion. 
     
     
         20 . The mixing device of  claim 15  wherein the mixing device is made of sheet metal.