Low-NOx burner

A burner device forming a combustion area on the downstream side of an air throat portion with use of a combustion air flow through the air throat portion and a fuel injected through a fuel nozzle comprising:

• preheating means for alternately introducing the combustion air flow being fed to a primary combustion area and the exhaust combustion gas produced therein through a regenerator and preheating the combustion air flow by means of a heat exchange action effected through a regenerator between the exhaust combustion gas and the combustion air;
• an enlarged diameter portion of a burner tile having an internal diameter greater than an internal diameter of said throat portion so as to define a secondary combustion area around the outlet of the air throat portion;
• first fuel injection means for injecting a fuel from the secondary combustion area to the combustion air flow in an inclined angle thereto;
• and
• a second fuel injection means for injecting a fuel to the combustion air flow introduced through the air throat portion;
• wherein said air throat portion injects the combustion air flow preheated by said preheating means in an axial direction of the air throat portion toward said primary combustion area, said secondary combustion area extends radially outward of the air throat portion adjacent to the outlet thereof and said first fuel injection means is positioned in a periphery zone of said enlarged diameter portion so as to inject the fuel toward a central section of said combustion air flow;
• and
• wherein said second fuel injection means is adapted to feed the fuel to the combustion air flow in the air throat portion when a temperature level in the primary combustion area is in a relatively low range, whereas said first injection means is adapted to feed the fuel to said combustion areas when said temperature is raised up to a high temperature range above a predetermined temperature.

A burner device having an air flow injection means for feeding a combustion air flow to a combustion area, fuel supply means for feeding a fuel to the combustion air flow, and air preheating means for preheating the combustion air to be supplied to the air flow injection means, comprising:

• the air flow injection means having an outlet for injecting air flow oriented so as to direct the preheated air flow to the combustion area;
• chamber forming means for defining a cylindrical secondary combustion chamber on the downstream side of said outlet adjacent thereto, said chamber forming means being formed in a periphery of the outlet so as to surround the combustion air flow discharged from the outlet whereby a recirculation flow of the combustion gas produced in the combustion area is caused by an inducement action of the combustion air flowing out of the outlet said fuel supply means oriented to inject fuel toward a central region of said cylindrical secondary combustion chamber;
• wherein said combustion area includes a flame stabilizing region, a recirculation combustion region and a slow combustion region, said fuel supply means injects the fuel from said secondary combustion chamber toward said combustion area to generate a stable combustion reaction in said flame stabilizing region, a part of the fuel and the recirculation flow, including said combustion gas, generate a combustion reaction of a relatively low oxygen density in said recirculation combustion region, and the combustion gas produced in the flame stabilizing region generates a gently performing combustion reaction in said slow combustion region.

A burner device forming a combustion area on the downstream side of an air throat portion with use of a combustion air flow through the air throat portion and a fuel injected through a fuel nozzle comprising:

• preheating means for alternately introducing the combustion air flow being fed to a primary combustion area and the exhaust combustion gas produced therein through a regenerator and preheating the combustion air flow by means of a heat exchange action effected through a regenerator between the exhaust combustion gas and the combustion air, said regenerator having a honeycomb structure for allowing the combustion air to be introduced therethrough and is positioned on an upstream side of said air throat portion;
• an enlarged diameter portion of a burner tile having an internal diameter greater than an internal diameter of said throat portion so as to define a secondary combustion area around the outlet of the air throat portion;
• first fuel injection means for injecting a fuel from the secondary combustion area to the combustion air flow in an inclined angle thereto;
• and
• a second fuel injection means for injecting a fuel to the combustion air flow introduced through the air throat portion in a direction substantially perpendicular to the combustion air flow in the throat portion;
• wherein said air throat portion injects the combustion air flow preheated by said preheating means in an axial direction of the air throat portion toward said primary combustion area, said secondary combustion area extends radially outward of the air throat portion adjacent to the outlet thereof and said first fuel injection means is positioned in a periphery zone of said enlarged diameter portion so as to inject the fuel toward a central section of said combustion air flow;
• and
• wherein said second fuel injection means is adapted to feed the fuel to the combustion air flow in the air throat portion when a temperature level in the primary combustion area is in a relatively low range and capable of terminating a fuel injection operation, whereas said first injection means initiates a fuel injection operation at a predetermined temperature and is adapted to feed the fuel to said combustion areas when said temperature is raised up to a high temperature range above the predetermined temperature;
• reducing means for reducing a cross-section of a combustion air flow passage which is provided between said regenerator and said air throat portion, whereby the combustion air flow having passed through the regenerator has an increased flow velocity, such that the higher flow velocity combustion air flow flowing out of the air throat portion toward the primary combustion area generates a negative pressure in said secondary combustion area so as to induce a combustion gas produced in the primary combustion area into the secondary combustion area.