Burner as well as boiler-burner assembly as well as method for generating a flame into the same

A boiler-burner assembly for burning a premixed air-fuel mixture (80) with a flame (A, B, C, D) generated inside (90) a boiler (9),

• said burner (1) comprising a frame member (5) remaining outside the boiler (9) and having associated therewith an elongated combustion head (2) protruding from said frame member (5) and having a first section (22) thereof remaining outside the boiler (9) or being connected to structures of the boiler (9) and having a second section (21) thereof extending into an interior of the boiler (9), and said combustion head (2) having what in a view from the frame member (5) of the burner (1) is its distal end provided with a tip plate (7), said combustion head (2) comprising an outer, larger diameter tube (3) for a mixture of combustion air and fuel as well as an inner, smaller diameter tube (4),
• whereby the combustion head (2) has its outer tube (3) formed with at least one array of aperture lines (31, 33) encircling said body of the outer tube (3) and, in addition, what in a view from the burner's (1) frame member is a distal end opening of the outer tube (3), i.e. an opening (35) at a tip (3a) of the outer tube (3), opens into a space (7d1) on a forward side (7d) of the tip plate (7), said outer tube (3) being provided with a supply of premixed air-fuel mixture (80) preferably from the burner's frame member (5) for conveying the premixed air-fuel mixture (80) outward of the combustion head (2) by way of the apertures (31, 33) included in the body of the outer tube (3), as well as by way of the outer tube's tip opening (35), and
• the inner tube (4) of the combustion head (2) is continuous and extends from the frame member (5) into a space (7d2) on a forward side (7d) of the tip plate (7), said tip plate (7) having a width (T) approximately equal to the diameter of the outer tube's (3) tip opening (35) and the direction of a plane (R) defined by the tip plate (7) is transverse to a longitudinal direction (P) of the combustion head (2), wherein the mouth of the inner tube (4) opens into the space (7d2) present on what in the combustion air traveling direction is a forward side (7) of the tip plate (7), and into alignment with the air openings (71) of the tip plate (7),
• characterized in that
• from the burner's (1) frame member (5) is provided a supply of combustion air (55) into the combustion head's (2) inner tube (4) for conveying the combustion air (55) by way of said inner tube to what in a view from the burner's (1) frame member (5) is a forward side (7d) of the tip plate (71) and further through air openings (71) included in the tip plate for cooling said tip plate, whereby the temperature of a flame portion (C) generated inside (90) the boiler (9), which temperature is established in the boiler interior (90) immediately behind the tip plate (71), is lower than the temperature of a main flame (B) surrounding the same,
• the combustion head (2) has its tip plate (71) located at such a distance from the outer tube's (3) mouth (35) that the gas, such as the fuel-air mixture (80), arriving in a space (7d1) on a forward side (7d) of the tip plate (7) has a flow connection from the space (7d1) on the forward side (7d) of the tip plate (71) into an interior (90) of the boiler (9) and, in addition, between a side edge (7a) of the tip plate (7) and a plane (R) defined by the tip plate (7) is an angle of incidence (a) as a result of which the gas (30) supplied to the forward side of the tip plate (7) is directed angularly away from a longitudinal center line (P) of the combustion head (2), generating a main flame (B) which surrounds said flame portion (C).

A method for generating a flame (A, B, C, D) inside of a boiler (9) of the boiler-burner assembly by burning a premixed air-fuel mixture (80) with a flame (A, B, C, D),

• wherein said burner (1) comprising a frame member (5) remaining outside the boiler (9) and having associated therewith an elongated combustion head (2) protruding from said frame member (5) and having a first section (22) thereof remaining outside the boiler (9) or being connected to structures of the boiler (9) and having a second section (21) thereof extending into an interior of combustion space of the boiler (9), and said combustion head (2) provided its distal end with a tip plate (7), said combustion head (2) comprising an outer, larger diameter tube (3) for a mixture of combustion air and fuel as well as an inner, smaller diameter tube (4), whereby
• the combustion head (2) has its outer tube (3) formed with at least one array of aperture lines (31, 33) encircling said body of the outer tube (3) and, in addition, an opening (35) at a tip (3a) of the outer tube (3), opens into a space (7d1) on a forward side (7d) of the tip plate (7), said outer tube (3) being provided with a supply of premixed air-fuel mixture (80) for conveying the premixed air-fuel mixture (80) outward of the combustion head (2) by way of the apertures (31, 33) included in the body of the outer tube (3), as well as by way of the outer tube's tip opening (35), and
• the inner tube (4) of the combustion head (2) is continuous and extends from the frame member (5) into a space (7d2) on a forward side (7d) of the tip plate (7), said tip plate (7) having a width (T) approximately equal to the diameter of the outer tube's (3) tip opening (35) and the direction of a plane (R) defined by the tip plate (7) is transverse to a longitudinal direction (P) of the combustion head (2), wherein the mouth of the inner tube (4) opens into the space (7d2) present on what in the combustion air traveling direction is a forward side (7) of the tip plate (7), and into alignment with the air openings (71) of the tip plate (7),
• characterized in that said method comprises at least following steps:
• arranging the combustion air (55) to flow from the combustion head's (2) inner tube (4) to a forward side (7d) of the tip plate (71) and further through air openings (71) included in the tip plate to cool said tip plate and to generate a flame portion (C) inside (90) the boiler (9), immediately behind the tip plate (71), said flame portion (C) having a temperature which is lower than the temperature of a main flame (B) surrounding the flame portion (C),
• arranging the gas, such as the fuel-air mixture (80), supplied in a space (7d1) on a forward side (7d) of the tip plate (7) to be in a flow connection from the space (7d1) on the forward side (7d) of the tip plate (71) into an interior (90) of the boiler (9)
• directing the gas flow angularly away from a longitudinal center line (P) of the combustion head (2) by means of an angle of incidence between a side edge (7a) of the tip plate (7) and a plane (R) defined by the tip plate (7) thus generating a main flame (B) which surrounds said flame portion (C), said main flame (B) having a conical burning zone at a tip of the combustion head (2).