Fuel/air mixture and combustion apparatus and associated methods for use in a fuel-fired heating apparatus

A method of sound-attenuation in a fuel-fired furnace, the method comprising:

• creating a flow of air through an interior of a venturi structure having (i) a longitudinal axis extending through its interior, (ii) sidewall perforations, and (iii) first and second opposite end portions, while swirling about its longitudinal axis;
• creating a flow of gaseous fuel that impacts and mixes with the swirling flow of air creating a fuel/air mixture in a direction transverse to the longitudinal axis, wherein the flow of fuel is provided by radially directed interior fuel jets disposed within the first end portion of the venturi structure;
• and
• dampening pressure oscillations within the venturi structure, via a chamber disposed around the venturi structure, wherein the chamber is in fluid communication with the interior of the venturi structure through its sidewall perforations such that the fuel/air mixture enters the chamber, in a manner effective to attenuate fuel/air mixing noise generated within the venturi structure.

A method for reducing a NOx level of discharged combustion gases in a fuel-fired heating apparatus, the method comprising:

• creating, via a vane structure, a flow of air through an interior of a venturi structure having (i) a longitudinal axis extending through its interior, (ii) sidewall perforations, and (iii) first and second opposite end portions, while swirling about its longitudinal axis;
• creating, via radially directed interior fuel jets, a flow of gaseous fuel that mixes with the swirling flow of air in a direction transverse to the longitudinal axis;
• and
• dampening pressure oscillations within the venturi structure, via a chamber disposed around the venturi structure, wherein the chamber is in fluid communication with the interior of the venturi structure through its sidewall perforations;
• flowing a fuel/air mixture exiting the venturi structure through a secondary fuel/air mixing structure, wherein the fuel/air mixture is permitted to enter the chamber disposed around the venturi structure through the sidewall perforations;
• and then
• flowing the fuel/air mixture into a burner box of the fuel-fired heating apparatus,
• wherein the secondary fuel/air mixing structure is effective to further mix the fuel and air by providing further residence time for the fuel/air mixture created in the venturi structure housing, which is effective to reduce the level of NOx emissions created by the fuel-fired heating apparatus during firing thereof.