阅读说明：本技术 模块化燃烧器 (Modular burner ) 是由 卢卡·巴罗齐 埃托雷·埃滕齐 加布里埃列·甘加莱 桑德罗·卢利 于 2021-04-22 设计创作，主要内容包括：一种模块化燃烧器,包括多个混合器模块(10),多个混合器模块并排定位并且平行于纵向平面(Y),每个混合器模块具有平行于纵向平面(Y)测得的长度(L),并且排放表面(14)具有垂直于纵向平面(Y)测得的宽度(D),并且其中,两个相邻的排放表面(14)以垂直于纵向平面(Y)测得的距离(S)间隔开。距离(S)与宽度(D)之间的比率包含在0.4与0.7之间。(A modular burner comprising a plurality of mixer modules (10) positioned side by side and parallel to a longitudinal plane (Y), each mixer module having a length (L) measured parallel to the longitudinal plane (Y) and a discharge surface (14) having a width (D) measured perpendicular to the longitudinal plane (Y), and wherein two adjacent discharge surfaces (14) are spaced apart by a distance (S) measured perpendicular to the longitudinal plane (Y). The ratio between the distance (S) and the width (D) is comprised between 0.4 and 0.7.)

1. A modular burner comprising a plurality of mixer modules (10) positioned side by side and parallel to a longitudinal plane (Y), each mixer module having a length (L) measured parallel to the longitudinal plane (Y), wherein each mixer module (10) comprises:

a flow conduit (11) provided with an inlet opening (12) and with a plurality of outlet openings (13) arranged on a discharge surface (14);

wherein the discharge surface (14) is located in a discharge plane (100) of the modular burner;

wherein each discharge surface (14) has a width (D) measured perpendicular to the longitudinal plane (Y), and wherein two adjacent discharge surfaces (14) are spaced apart by a distance (S) measured perpendicular to the longitudinal plane (Y);

characterized in that the ratio between said distance (S) and said width (D) is comprised between 0.4 and 0.7.

2. Modular burner according to claim 1, comprising a rear bracket (20) provided with a main portion (21) having a plurality of through openings (22), wherein said through openings have a total area a, characterized by a dimensionless parameter K:

greater than 4, wherein N is the total number of mixer modules (10) and S is the distance (S) by which two adjacent discharge surfaces (14) are spaced apart.

3. The modular burner according to claim 2, wherein said through openings (22) have a circular shape and are arranged along two parallel rows, and wherein each space separating two adjacent mixer modules faces two of said through openings (22).

4. The modular burner according to claim 2, wherein the rear bracket (20) comprises a plurality of receptacles (23), each shaped to receive a respective rear coupling portion of the mixer module (10).

5. A modular burner according to claim 1, comprising a front bracket (30) provided with a main portion (31) having a through opening (32) in the shape of an elongated slot, wherein the through opening (32) of the front bracket faces the inlet opening (12) of the flow duct (11).

6. Modular burner according to claim 5, wherein said front bracket (30) comprises supporting feet (35) defined by folded lower edges of said front bracket (30) substantially perpendicular to the main portion (31) of said front bracket, i.e. parallel to said discharge plane (100).

7. The modular burner according to claim 1, comprising a plurality of mixer modules (10) positioned side by side and parallel to a longitudinal plane (Y), each mixer module having a length (L) measured parallel to said longitudinal plane (Y), wherein said mixer modules are spaced apart from each other by a mounting pitch (P) measured as the distance between the median longitudinal planes of two adjacent mixer modules (10), characterized in that the ratio between the length of the mixer modules and the mounting pitch (P) is greater than 11.

8. The modular burner according to claim 7, wherein the ratio between the length of the mixer module (10) and the mounting pitch (P) is about 12.3.

9. The modular burner of claim 1, wherein each mixer module (10) comprises: a flow conduit (11) provided with an inlet opening (12) and with a plurality of outlet openings (13) arranged on a discharge surface (14); wherein the discharge surfaces (14) are located in a discharge plane (100) of the modular burner and in the discharge plane (100) the discharge surfaces are spaced apart from each other by a free surface (15); characterized in that the ratio between the total area of the free surfaces (15) and the total area of the discharge surface (14) and the free surfaces (15) is less than 0.2.

10. The modular burner of claim 1, wherein each mixer module (10) comprises: a flow conduit (11) provided with an inlet opening (12) and with a plurality of outlet openings (13) arranged on a discharge surface (14); wherein the discharge surfaces (14) are located in a discharge plane (100) of the modular burner and in the discharge plane (100) the discharge surfaces are spaced apart from each other by a free surface (15); characterized in that in each of said mixer modules (10) the ratio between the total area of said outlet openings (13) and the area of said discharge surface (14) is comprised between 0.20 and 0.30.

Technical Field

The present invention relates to a modular burner which can be used, for example, in a wall-mounted boiler.

In particular, the invention relates to a modular burner comprising a plurality of mixer modules positioned side by side, also called "ramps".

Background

Each mixer module typically includes a flow conduit for an air-fuel mixture. The flow conduit is bent into a U-shape, i.e. it has a configuration comprising two portions which are slightly inclined with respect to each other and connected by a bend defining an angle not much smaller than 180 °. The flow conduit lies in a substantially vertical plane. The upper portion of the flow duct communicates with a series of outlet openings of elongated shape and arranged side by side on a substantially flat discharge surface, these outlet openings being intended to discharge a mixture of air and combustible gas. The discharge surface of the mixer module lies in the main discharge plane of the burner. The lower portion of the flow duct of each mixer module faces a nozzle for injecting combustible gas at a venturi arranged substantially perpendicular to the inlet opening of the flow duct.

The flow of combustible gas injected into the inlet of the flow conduit produces an entrainment of so-called primary air through the venturi, which primary air mixes with the fuel in the flow conduit. The air-fuel mixture flowing out of the flow duct through the outlet opening of the mixer module feeds the flame extending above the mixer module close to the outlet opening itself. Additional combustion air, referred to as secondary air, is fed to the flame from the surroundings, in particular through the spaces separating the respective adjacent mixer modules from each other.

An important geometrical feature of a modular burner is the ratio between the total area of the burner, which is considered to be the total area of the discharge surface of the mixer module and the space separating the discharge surfaces, and the total area of the space between the discharge surfaces of the mixer module. Both areas are measured in the main discharge plane of the burner.

In current modular burners, the above ratio is about 0.3. This determines a very significant contribution of secondary air to the completion of combustion. Thus, at the outlet of the mixer module, through the outlet opening, the air-fuel mixture has a relatively low lambda (lambda) (typically less than 1, i.e. less than stoichiometric). This means that in the region closest to the outlet opening of the mixer module the flame temperature is above a critical value for the formation of nitrogen oxides (NOx). This phenomenon is particularly pronounced in low power states of the boiler, which is of course undesirable for obvious reasons relating to the suppression of harmful emissions.

In italian patent application 102018000005589, the same applicant provided an effective solution to the above problem, describing a modular burner in which the ratio between the areas is less than 0.2, i.e. at least 60% lower than the same ratio in a traditional burner. In the modular burner of italian application 102018000005589, the mixer modules are located closer to each other than the traditional modular burners are provided.

The reduction in the ratio between these two areas makes it possible to reduce considerably the effect of the secondary air on the combustion occurring at the outlet of the outlet opening in the vicinity of the discharge surface and the discharge plane and thus to enable a reduction in the emissions of NOx.

Through extensive research, the applicant has identified further geometric parameters that enable the morphology of the modular burner to be defined more simply, while still further reducing the emissions of NOx.

Disclosure of Invention

An advantage of the burner according to the invention is that it does not require any particular modification of the structure of the wall-mounted boiler in which it is installed or of the burner itself, the overall structure of which is substantially similar to that of currently available burners.

Another advantage of the burner according to the invention is that the delivered power can be regulated more precisely.

Drawings

Additional features and advantages of the invention will become more apparent from the following detailed description of embodiments of the invention, which are illustrated by way of non-limiting example in the accompanying drawings, wherein:

FIG. 1 shows a schematic view of a mixer module that may be used in a combustor according to the present invention;

FIG. 2 schematically illustrates a boiler in which a burner according to the present invention may be used;

FIG. 3 shows an exploded isometric view of a burner according to the present invention;

FIG. 4 shows a top view of a modular burner according to the present invention;

FIG. 5 shows an enlarged view of FIG. 4;

FIGS. 6 and 7 show a rear view and a front view, respectively, of a burner according to the present invention;

FIG. 8 shows a top view with some important areas of the burner highlighted;

FIG. 9 shows a graph representing λ of an air-fuel mixture as a function of power delivered by a burner of the currently available burners;

fig. 10 shows a graph representing the variation of lambda of the air-fuel mixture with the power delivered by the burner according to the invention.

Detailed Description

The modular burner 1 according to the invention can be used in a boiler of the type schematically shown in fig. 2. The burner 1 generates a flame which heats the heat exchanger 3 above, in which a carrier fluid flows, which transfers the received heat to a defined destination. The fumes produced by the combustion are drawn by the fan 4 and sent to the exhaust.

The modular burner according to the invention comprises a plurality of mixer modules 10 positioned side by side. The mixer modules have a generally flat configuration and are arranged in parallel and are connected to each other by means of a rear bracket 20 and a front bracket 30, which enable the burner 1 to be constrained to a support structure. The mixer modules 10 are separated from each other by free spaces allowing air to pass through.

Each mixer module 10 comprises a flow duct 11, i.e. a duct for passing an air-fuel mixture. In the illustrated embodiment, the flow conduit 11 has a curved U-shaped configuration, wherein the lower portion 11a is connected to the upper portion 11b by a bend 11 c. The upper portion 11b may be slightly inclined upward from the bent portion 11 c.

The flow conduit 11 is provided with an inlet opening 12. The inlet opening 12 is located at the end of the lower part 11 a. The inlet opening 12 is intended to receive a predetermined flow of fuel discharged by the nozzle 2, which may be positioned in a forward position with respect to the inlet opening 12. The flow conduit 11 is further provided with a venturi tube 12a located downstream of the inlet opening 12. In a known manner, the flow of fuel generated by the nozzle 2 generates, by passing through the venturi tube 12a, a negative pressure which generates a suction of some of the air flow through the inlet opening 12.

The flow conduit 11 is further provided with a plurality of outlet openings 13 arranged on a discharge surface 14. The outlet opening 13 is obtained by a substantially strip-shaped plate having an elongated shape, which plate defines a discharge surface 14. In the embodiment shown, the outlet openings 13 are elongated in shape and parallel to each other, as can be seen in particular in fig. 4 and 5.

The mixer module 10 is arranged such that the discharge surface 14 is located in the discharge plane 100 of the burner. The discharge plane 100 is essentially a plane containing the discharge surface 14 except in the case of misalignment due to the assembly of the mixer module 10 and the effective geometry of the discharge surface 14. In any case, the discharge plane 100 contains the geometric projection of the discharge surface 14.

On the discharge plane 100, the discharge surfaces 14 are spaced apart from each other by a free surface 15. The free surface 15, represented by cross-hatching in fig. 8, is substantially defined by the geometric projection on the discharge plane 100 of the space separating the mixer modules 10. The discharge surface 14 is instead indicated by oblique lines.

Each discharge surface 14 has a width D, measured perpendicularly to the longitudinal plane Y, and this width is understood to be the distance separating the two longitudinal edges of the discharge surface itself parallel to the longitudinal plane Y.

Furthermore, two adjacent discharge surfaces 14 are spaced apart by a distance S, which is measured perpendicular to the longitudinal plane Y and is understood as the distance by which the adjacent longitudinal edges of two discharge surfaces 14 are spaced apart.

In the present modular burner, the ratio between the distance S separating two adjacent discharge surfaces 14 and the width D of each discharge surface 14 is comprised between 0.9 and 1.6. There is also a particular class of water-cooled modular burners in which the ratio of S/D is lower than 0.1.

In the modular burner according to the invention, the ratio between the distance S separating two adjacent discharge surfaces 14 and the width D of each discharge surface 14 is comprised between 0.4 and 0.7.

In essence, the mixer modules 10 in the modular burner according to the invention are closer to each other than provided in current modular burners. This reduces the space in which the mixer modules 10 are spaced apart from each other, thereby reducing the free surface 15.

This reduction of the operating ratio makes it possible to reduce significantly the effect of the secondary air on the combustion occurring at the discharge surface 14 and at the outlet of the outlet opening 13 near the discharge plane 100. In fact, as mentioned above, the mixer module 10 is separated by a much reduced space compared to the current burners, so that the free surface 15 available for the secondary air flow is likewise reduced.

The flow rate of the primary air sucked into the flow duct 11 through the inlet opening 12 becomes dominant, since the effect of the secondary air is significantly reduced. The flow rate of the primary air sucked into the flow conduit 11 through the inlet opening 12 is substantially and mainly dependent on the negative pressure generated by the fan 4 inside the boiler, whereas the effect of the negative pressure generated by the fuel flow through the venturi tube 12a can be substantially neglected. In other words, the flow rate of the primary air and the flow rate of the secondary air remain substantially constant as the power state of the boiler changes. Once the operating conditions of the fan 4 are fixed, the power of the burner can be adjusted by varying only the flow rate of the gas sent to the flow duct (i.e. by varying the feed pressure of the gas to the nozzle 2). Further, the flow rate of the primary air is kept substantially constant as the flow rate of the fuel sent to the venturi tube 12a is changed.

Due to the characteristics of the modular burner according to the invention, in particular due to the reduced flow rate of the secondary air, the flow rate of the primary air drawn into the flow duct 11 of each mixer module 10 can be set so that, at low operating power of the burner, the primary lambda (lambda) of the air-fuel mixture is relatively high, about 1.3 (fig. 9), and decreases with increasing power, until a value of about 0.9 is reached at maximum burner power. At about 85% of the burner's operating power, λ is equal to 1.

Due to the characteristics of the burner according to the invention, starting from a low operating power of the burner, the main lambda value of the air-fuel mixture is relatively high and therefore also close to the outlet opening 13 and to the discharge plane 100. This feature makes it possible to keep the flame temperature below the typical values that cause the formation of nitrogen oxides NOx from the early stages of combustion.

In contrast, in the present burners, when nitrogen oxides have formed near the discharge plane 10, the flame is not cooled below the critical temperature for the formation of NOx until after the secondary air has acted on.

The modular burner according to the present invention comprises a rear bracket 20 and a front bracket 30. By means of the rear holder 20 and the front holder 30, the mixer modules 10 are kept parallel to each other in the above-mentioned position. Furthermore, the rear bracket 20 and the front bracket 30 enable the burner 1 to be constrained to a supporting structure.

The rear bracket 20 comprises a main portion 21 positioned substantially perpendicular to the longitudinal plane Y and to the discharge plane 100. The main portion 21 is configured to be positioned facing the rear region of the mixer module 10, thereby closing the burner 1 from the rear. The main portion 21 is provided with a plurality of through openings 22. The through-openings 22 in the rear region of the burner ensure an optimum flow of secondary air.

Each through opening has a defined area. Thus, the total area a of the through openings 22 is the area available for the secondary air flow. Where N is the total number of mixer modules 10 constituting the burner 1 and S is the distance S separating two adjacent discharge surfaces 14, the dimensionless parameter K may be defined in the following manner:

in the burner according to the invention, the dimensionless parameter K is greater than 4. This allows the features of the burner to be further improved in terms of efficiency and reduction of NOx emissions.

The through openings 22 preferably have a circular shape and are arranged along two parallel rows spaced apart at a regular pitch. Preferably, two through openings 22 are aligned with each space separating two adjacent mixer modules 10.

The rear bracket 20 comprises a plurality of receivers 23, each shaped to receive a respective rear coupling portion of the mixer module 10. The receiving member 23 is in the form of a slot formed in two wings 23a, 23b of the rear bracket 20, which protrude transversely with respect to the main portion 21 towards the mixer module 10.

The front carriage 30 comprises a main portion 31 positioned substantially perpendicular to the longitudinal plane Y and to the discharge plane 100 (i.e. parallel to the main portion 21 of the rear carriage 20). The main portion 31 is configured to be positioned facing the front region of the mixer module 10, thereby closing the burner 1 from the front.

The main portion 31 of the front bracket 30 is provided with a through opening 32. The through opening 32 has an elongated slot shape and is positioned facing the inlet opening 12 of the flow duct 11 of the mixer module 10. The elongated channel shape (i.e. without any bridges or transverse partitions) enables a free flow towards the inlet opening 12 through the through opening 32 without any substantial turbulence.

The front bracket 30 comprises a plurality of receptacles 33, each shaped to receive a respective front coupling portion of the mixer module 10. The receiving member 33 is in the form of a slot, half of which is formed in an upper wing 33a projecting transversely with respect to the main portion 31 towards the mixer module 10, while the other half of the slot is formed on a lower rib 33b positioned below the main portion 31 and turned towards the mixer module 10.

The front bracket 30 also has a support foot 35 located below the main portion 31. The support feet 35 are defined by the edges of the front carrier 30 which fold substantially perpendicular to the main portion 31, i.e. substantially parallel to the discharge plane 100. In the embodiment shown, the support foot 35 faces backwards towards the mixer module 10, but it may also face towards the opposite side. In addition to contributing to the support of the burner 1 and its constraint on the support structure, the supporting feet 35 also contribute to considerably stabilizing the front bracket 30, which is partially weakened by the presence of the through opening 32.

The following additional geometrical parameters, taken alone or in any combination, make it possible to further improve the combustion characteristics of the modular burner according to the invention.

Preferably, but not necessarily, in the burner according to the invention, the operating ratio between the total free area resulting from the sum of the free surfaces 15 projected onto the discharge plane 100 and the total area of the burner resulting from the sum of the discharge surface 14 and the free surfaces 15 projected onto the discharge plane 100 is less than or equal to 0.2.

In contrast, in currently available modular combustors, the above-described operating ratio is about 0.3. Thus, in the modular burner according to the invention, the operating ratio is about 60% lower than that provided by currently available burners.

In the burner according to the invention, the ratio between the total area of the outlet openings 13 and the area of the discharge surface 14 is greater than 0.20 for each mixer module. For example, for each mixer module 10, the above-mentioned ratio is comprised between 0.20 and 0.30.

Considering that the mixer modules 10 have a standard size providing a length L of the discharge surface 14 of 160mm, in the burner according to the invention the mixer modules 10 are spaced apart by a mounting pitch P of about 13mm, whereas in the present burner the mounting pitch is comprised between 17mm and 20.5mm, the mounting pitch being measured as the distance between the average longitudinal planes of two adjacent mixer modules 10. In the burner according to the invention, the ratio between the length of the mixer module 10 and the mounting pitch P is greater than 11, whereas in the present burner it is at most 9.41. In a particularly advantageous embodiment, this ratio is about 12.3.