Modular burner

Abstract

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.

Description

Technical Field

[0001] The present invention relates to a modular burner that can be used, for example, in a wall-mounted boiler.

[0002] Specifically, the present invention relates to a modular burner comprising multiple mixer modules, also known as "ramp", positioned side by side. Background Technology

[0003] Each mixer module typically includes a flow conduit for the air-fuel mixture. The flow conduit is U-shaped, meaning it has a configuration comprising two parts that are slightly inclined relative 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 conduit communicates with a series of elongated outlet openings arranged side-by-side on a substantially flat exhaust surface, these outlet openings being designed to discharge the mixture of air and combustible gas. The exhaust surface of the mixer module lies within the main exhaust plane of the burner. The lower portion of the flow conduit in each mixer module faces a nozzle for injecting the combustible gas at a venturi tube arranged substantially perpendicular to the inlet opening of the flow conduit.

[0004] The flow of combustible gas injected into the inlet of the flow duct generates a so-called primary air entrainment through the venturi tube, which mixes with the fuel within the flow duct. The air-fuel mixture flowing out of the flow duct through the outlet opening of the mixer module supplies the flame extending above the mixer module. Additional combustion air, called secondary air, is fed into the flame from the surrounding environment (particularly through the spaces separating adjacent mixer modules).

[0005] A key geometric feature of modular burners is the ratio between the total area of ​​the burner and the total area of ​​the space between the exhaust surfaces of the mixer modules. The total area of ​​the burner is considered to be the sum of the exhaust surfaces of the mixer modules and the space separating the exhaust surfaces. Both areas are measured on the main exhaust plane of the burner.

[0006] In current modular burners, the aforementioned ratio is approximately 0.3. This establishes a very significant role for secondary air in combustion completion. Consequently, at the mixer module outlet, through the outlet opening, the air-fuel mixture has a relatively low λ (lambda) (typically less than 1, i.e., less than the stoichiometric ratio). This means that in the region closest to the mixer module outlet opening, the flame temperature is above the critical value for nitrogen oxide (NOx) formation. This phenomenon is particularly pronounced at low boiler power levels and is certainly undesirable for obvious reasons related to suppressing harmful emissions.

[0007] In Italian patent application 102018000005589, the same applicant provided an effective solution to the above-mentioned problem, describing a modular burner in which the ratio between areas is less than 0.2, that is, at least 60% lower than the same ratio in conventional burners. In the modular burner of Italian application 102018000005589, the mixer modules are closer together than the distance set in conventional modular burners.

[0008] The reduction in the ratio between these two areas allows for a significant reduction in the effect of secondary air on combustion occurring at the outlet of the outlet opening near the emission surface and the emission plane, thereby enabling a reduction in NOx emissions.

[0009] Through extensive research, the applicant has identified further geometric parameters that allow for a simpler definition of the modular burner's shape while further reducing NOx emissions. Summary of the Invention

[0010] The advantage of the burner according to the invention is that no specific modifications are required to the structure of the wall-mounted boiler in which the burner is installed or to the burner itself; the overall structure of the burner is substantially similar to that of currently available burners.

[0011] Another advantage of the burner according to the invention is that it can more precisely regulate the delivered power. Attached Figure Description

[0012] Additional features and advantages of the invention will become more apparent from the following detailed description of embodiments thereof, in which embodiments of the invention are illustrated by way of non-limiting example in the accompanying drawings, wherein:

[0013] Figure 1 A schematic diagram of a mixer module that can be used in a burner according to the present invention is shown;

[0014] Figure 2 A boiler in which a burner according to the invention can be used is schematically shown;

[0015] Figure 3 An exploded isometric view of a burner according to the present invention is shown;

[0016] Figure 4 A top view of the modular burner according to the present invention is shown;

[0017] Figure 5 It shows Figure 4 Enlarged image;

[0018] Figure 6 and 7Rear and front views of the burner according to the present invention are shown respectively;

[0019] Figure 8 A top view is shown, highlighting some key areas of the burner;

[0020] Figure 9 A graph showing the variation of λ, representing the air-fuel mixture, with the power delivered by the burners in currently available burners is shown.

[0021] Figure 10 A graph showing the variation of λ, representing the air-fuel mixture, with the power delivered by the burner according to the invention is shown. Detailed Implementation

[0022] The modular burner 1 according to the present invention can be used in Figure 2 This is used in a boiler of the type schematically shown. Burner 1 produces a flame that heats the heat exchanger 3 above, in which a carrier fluid flows and transfers the received heat to a designated destination. The flue gas produced by combustion is drawn in by fan 4 and sent to the exhaust port.

[0023] The modular burner according to the invention includes a plurality of mixer modules 10 positioned side by side. The mixer modules have a generally flat construction and are arranged in parallel, and are connected to each other by a rear support 20 and a front support 30, which allow the burner 1 to be constrained to a support structure. The mixer modules 10 are separated from each other by free spaces that allow air to pass through.

[0024] Each mixer module 10 includes a flow conduit 11, i.e., a conduit through which an air-fuel mixture passes. In the illustrated embodiment, the flow conduit 11 has a curved U-shaped configuration, wherein a lower portion 11a is connected to an upper portion 11b via a bend 11c. The upper portion 11b may be slightly inclined upward from the bend 11c.

[0025] The flow conduit 11 is provided with an inlet opening 12. The inlet opening 12 is located at the end of the lower portion 11a. The inlet opening 12 is used to receive a predetermined fuel flow discharged from the nozzle 2, which can be positioned in front of the inlet opening 12. The flow conduit 11 is also provided with a venturi tube 12a located downstream of the inlet opening 12. In a known manner, the fuel flow generated by the nozzle 2 generates a negative pressure as it passes through the venturi tube 12a, which creates a suction of some airflow through the inlet opening 12.

[0026] The flow conduit 11 is also provided with a plurality of outlet openings 13 arranged on the discharge surface 14. The outlet openings 13 are obtained by means of a plate having an elongated, substantially strip-like shape, which defines the discharge surface 14. In the illustrated embodiment, as specifically possible... Figure 4 and Figure 5 As seen in the image, the outlet openings 13 are elongated in shape and parallel to each other.

[0027] The mixer module 10 is arranged such that the exhaust surface 14 lies within the exhaust plane 100 of the burner. The exhaust plane 100 is essentially a plane that includes the exhaust surface 14, except for misalignment caused by the assembly of the mixer module 10 and the effective geometry of the exhaust surface 14. In all cases, the exhaust plane 100 includes the geometric projection of the exhaust surface 14.

[0028] On the discharge plane 100, the discharge surfaces 14 are spaced apart from each other by free surfaces 15. Figure 8 The free surface 15, represented by crosshairs, is essentially defined by the geometric projection of the spaces that space the mixer modules 10 apart onto the discharge plane 100. The discharge surface 14 is instead represented by diagonal lines.

[0029] Each emission surface 14 has a width D measured perpendicular to the longitudinal plane Y, and this width is understood to be the distance between the two longitudinal edges of the emission surface itself, which are parallel to the longitudinal plane Y.

[0030] In addition, two adjacent emission surfaces 14 are separated by a distance S, which is measured perpendicular to the longitudinal plane Y and is understood as the distance between the adjacent longitudinal edges of the two emission surfaces 14.

[0031] In current modular burners, the ratio between the distance S between two adjacent exhaust surfaces 14 and the width D of each exhaust surface 14 is between 0.9 and 1.6. Certain categories of water-cooled modular burners also exist where the S / D ratio is less than 0.1.

[0032] In the modular burner according to the invention, the ratio between the distance S between two adjacent exhaust surfaces 14 and the width D of each exhaust surface 14 is between 0.4 and 0.7.

[0033] Essentially, compared to that in current modular burners, the mixer modules 10 in the modular burner according to the invention are closer together. This reduces the space between the mixer modules 10 and thus reduces the free surface 15.

[0034] This reduction in the operating ratio allows for a significant reduction in the effect of secondary air on combustion occurring at the outlet of the outlet opening 13 near the exhaust surface 14 and the exhaust plane 100. In fact, as described above, the mixer module 10 is separated by a significantly reduced space compared to the current burner, thus also reducing the free surface 15 available for secondary airflow.

[0035] Because the effect of secondary air is significantly reduced, the flow rate of main air drawn into flow duct 11 through inlet opening 12 becomes dominant. The flow rate of main air drawn into flow duct 11 through inlet opening 12 depends essentially and primarily on the negative pressure generated by fan 4 within the boiler, while the effect of the negative pressure generated by the fuel flow through venturi tube 12a is essentially negligible. In other words, the flow rates of main air and secondary air remain essentially constant as the boiler's power state changes. Once the operating state of fan 4 is fixed, the burner power can be adjusted by simply changing the flow rate of gas supplied to flow duct 11 (i.e., by changing the gas feed pressure to nozzle 2). Furthermore, the flow rate of main air remains essentially constant as the flow rate of fuel supplied to venturi tube 12a changes.

[0036] Due to the features of the modular burner according to the invention, particularly due to the reduced secondary air flow rate, the flow rate of the main air drawn into the flow duct 11 of each mixer module 10 can be set such that, at low operating power of the burner, the main λ (lambda) of the air-fuel mixture is relatively high, approximately 1.3. Figure 9 ), and decreases with increasing power until it reaches a value of approximately 0.9 at the maximum burner power. At approximately 85% of the burner's operating power, λ equals 1.

[0037] Due to the characteristics of the burner according to the invention, the primary λ value of the air-fuel mixture is relatively high from the low operating power of the burner, and therefore also close to the outlet opening 13 and the exhaust plane 100. This feature allows the flame temperature to be maintained below the typical value that causes the formation of nitrogen oxides (NOx) from the early stages of combustion.

[0038] In contrast, in current burners, when nitrogen oxides have already formed near the emission plane 100, the flame is not cooled below the critical temperature for NOx formation until secondary air comes into play.

[0039] The modular burner according to the invention includes a rear support 20 and a front support 30. The mixer module 10 is kept parallel to each other in the aforementioned positions by means of the rear support 20 and the front support 30. Furthermore, the rear support 20 and the front support 30 allow the burner 1 to be constrained to a support structure.

[0040] The rear support 20 includes a main portion 21 positioned substantially perpendicular to the longitudinal plane Y and perpendicular to the discharge plane 100. The main portion 21 is configured to face the rear region of the mixer module 10, thereby enclosing the burner 1 from the rear. The main portion 21 is provided with a plurality of through openings 22. The through openings 22 located in the rear region of the burner ensure optimal flow of secondary air.

[0041] Each through-opening has a defined area. Therefore, the total area A of the through-openings 22 is the area available for secondary airflow. Where N is the total number of mixer modules 10 constituting the burner 1, and S is the distance S separating two adjacent exhaust surfaces 14, the dimensionless parameter K can be defined as follows:

[0042]

[0043] In the burner according to the invention, the dimensionless parameter K is greater than 4. This allows for further improvements in burner characteristics in terms of efficiency and NOx emission reduction.

[0044] The through opening 22 preferably has a circular shape and is arranged along two parallel rows spaced at a regular pitch. Preferably, the two through openings 22 are aligned with each space that separates two adjacent mixer modules 10.

[0045] The rear support 20 includes a plurality of receptacles 23, each receptacle being shaped to receive a corresponding rear coupling portion of the mixer module 10. The receptacles 23 are in the form of slots formed in two airfoils 23a, 23b of the rear support 20, which project laterally toward the mixer module 10 relative to the main portion 21.

[0046] The front support 30 includes a main portion 31 positioned substantially perpendicular to the longitudinal plane Y and perpendicular to the discharge plane 100 (i.e., parallel to the main portion 21 of the rear support 20). The main portion 31 is configured to be positioned facing the front region of the mixer module 10, thereby enclosing the burner 1 from the front.

[0047] The main part 31 of the front support 30 is provided with a through opening 32. The through opening 32 has an elongated groove shape and is positioned to face the inlet opening 12 of the flow conduit 11 of the mixer module 10. The elongated groove shape (i.e., without any bridging or lateral partitions) allows free flow through the through opening 32 to the inlet opening 12 without any substantial turbulence.

[0048] The front support 30 includes a plurality of receptacles 33, each receptacle being shaped to receive a corresponding front coupling portion of the mixer module 10. The receptacles 33 are in the form of slots, one half of which is formed in an upper wing-shaped member 33a that projects laterally toward the mixer module 10 relative to the main portion 31, while the other half of the slot is formed on a lower rib 33b that is positioned below the main portion 31 and faces toward the mixer module 10.

[0049] The front support 30 also has a support foot 35 located below the main portion 31. The support foot 35 is defined by an edge of the front support 30 that folds substantially perpendicular to the main portion 31, i.e., substantially parallel to the exhaust plane 100. In the illustrated embodiment, the support foot 35 faces rearward toward the mixer module 10, but it may also face toward the opposite side. In addition to contributing to the support of the burner 1 and its constraint on the support structure, the support foot 35 also helps to make the front support 30, which is partially weakened due to the presence of the through opening 32, quite stable.

[0050] The following additional geometric parameters, used individually or in any combination, enable further improvement in the combustion characteristics of the modular burner according to the invention.

[0051] Preferably, but not necessarily, in the burner according to the invention, the operating ratio between the total free area obtained by the sum of the free surfaces 15 projected onto the exhaust plane 100 and the total area of ​​the burner obtained by the sum of the exhaust surface 14 and the free surfaces 15 projected onto the exhaust plane 100 is less than or equal to 0.2.

[0052] Conversely, in currently available modular burners, the aforementioned operating ratio is approximately 0.3. Therefore, in the modular burner according to the invention, the operating ratio is approximately 60% lower than that provided by currently available burners.

[0053] In the burner according to the invention, for each mixer module, the ratio between the total area of ​​the outlet opening 13 and the area of ​​the discharge surface 14 is greater than 0.20. For example, for each mixer module 10, the ratio is between 0.20 and 0.30.

[0054] Considering that the mixer module 10 has a standard length L providing a 160 mm exhaust surface 14, in the burner according to the invention, the mixer modules 10 are spaced apart by an installation pitch P of approximately 13 mm, while in conventional burners, this installation pitch is between 17 mm and 20.5 mm, and the installation pitch is measured based on 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 installation pitch P is greater than 11, while in conventional burners it is at most 9.41. In a particularly advantageous embodiment, this ratio is approximately 12.3.

Claims

1. A modular burner comprising a plurality of mixer modules (10), the plurality of mixer modules being positioned side-by-side and parallel to a longitudinal plane (Y), each of the mixer modules having a length (L) measured parallel to the longitudinal plane (Y), wherein, Each of the mixer modules (10) includes: The flow conduit (11) is provided with an inlet opening (12) and a plurality of outlet openings (13) arranged on the discharge surface (14). The emission surface (14) is located in the emission plane (100) of the modular burner; Each of the emission surfaces (14) has a width (D) measured perpendicular to the longitudinal plane (Y), and two adjacent emission surfaces (14) are spaced apart by a distance (S) measured perpendicular to the longitudinal plane (Y). The feature is that the ratio between the distance (S) and the width (D) is between 0.4 and 0.7; The modular burner includes a rear support (20), which has a main section (21) with multiple through openings (22), wherein the through openings have a total area A, and the dimensionless parameter K is: Greater than 4, where N is the total number of the mixer modules (10) and S is the distance (S) between two adjacent discharge surfaces (14). The through openings (22) are arranged along two parallel rows, and each space that separates two adjacent mixer modules faces the two through openings (22).

2. The modular burner according to claim 1, wherein, The through opening (22) has a circular shape.

3. The modular burner according to claim 1, wherein, The rear support (20) includes a plurality of receptacles (23), each of the receptacles being shaped to receive a corresponding rear coupling portion of the mixer module (10).

4. The modular burner according to claim 1, comprising a front support (30), the front support having a main portion (31) having a through opening (32) in the shape of an elongated slot, wherein, The through opening (32) of the front support faces the inlet opening (12) of the flow conduit (11).

5. The modular burner according to claim 4, wherein, The front support (30) includes a support foot (35) defined by a folded lower edge of the front support (30), the lower edge being substantially perpendicular to the main portion (31) of the front support, i.e., the lower edge being parallel to the discharge plane (100).

6. The modular burner according to claim 1, wherein, The mixer modules are spaced apart from each other by an installation pitch (P), which is measured based on the distance between the intermediate longitudinal planes of two adjacent mixer modules (10), and wherein the ratio between the length of the mixer module and the installation pitch (P) is greater than 11.

7. The modular burner according to claim 6, wherein, The ratio between the length of the mixer module (10) and the installation pitch (P) is 12.

3.

8. The modular burner according to claim 1, wherein, In the emission plane (100), the emission surfaces (14) are spaced apart from each other by free surfaces (15); and wherein the ratio between the total area of ​​the free surfaces (15) and the total area of ​​the emission surfaces (14) and the free surfaces (15) is less than 0.

2.

9. The modular burner according to claim 1, wherein in the exhaust plane (100), the exhaust surfaces (14) are spaced apart from each other by free surfaces (15); and wherein, In each of the mixer modules (10), the ratio between the total area of ​​the outlet opening (13) and the area of ​​the discharge surface (14) is between 0.20 and 0.30.

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