Gas burner

Abstract

An air-cooled gas burner (1) comprises: a plurality of ramp-shaped elements (2), each comprising a first intake duct (21) and a second intake duct (22) having respective inlets (21A, 22A) and respective outlets (21B, 22B), wherein the plurality of ramp-shaped elements (2) are arranged continuously along a transverse direction (T); a manifold (3) configured to supply gas to the inlets of the first intake duct (21) and the second intake duct (22), wherein the first intake duct (21) and the second intake duct (22) are configured to suck gas and primary air into their respective inlets (21A, 22A) by the Venturi effect; a respective diffuser (4) for each ramp-shaped element (2), which defines a plurality of holes (40) through which flames are generated from the combustion of the gas from the first intake duct (21) and the second intake duct (22).

Description

Field of the Invention

[0001] The present invention relates to a gas burner and a method of burning a gas. Background Art

[0002] In particular, the burner of the present invention is suitable for boilers and water heaters. Burners including a plurality of elements (or ramps or plates) are known in the art, which are arranged parallel to each other and define ducts thereinside, and gas is supplied to these ducts through a manifold located at a first end of the elements. The gas is drawn into the ducts together with air (referred to as primary air) and reaches a second end (or head) of the elements, where there is a diffuser through which the gas generates a flame that propagates into the combustion chamber. Burners are known in the prior art in which each element (or ramp or plate) defines two ducts configured to draw in primary air and gas in parallel; such burners are particularly advantageous in terms of the uniform distribution of the gas towards the diffuser and thus in terms of the heat flux generated in the combustion chamber. For example, examples of burners having two intake ducts are described in the following patent documents: FR2745891B1, WO2016 / 193904, CN204438118U. Other examples of burners are provided in the following patent documents: DE4207814A1, EP1201990A1, and DE3338126A1.

[0003] The burners of the prior art release a large amount of nitrous emissions (nitrogen oxide emissions, NO x ) and other toxic substances, and there are also problems with flame stability. In particular, if combustion occurs under stoichiometric or sub-stoichiometric conditions, the head of the element overheats, resulting in a large amount of NO x There is also a large amount of carbon monoxide emissions; this problem is particularly evident when the thermal power used by the burner is close to the minimum of the operating range. To overcome this problem, some burners of the prior art (for example, the burner described in the document WO2016 / 193904 in the name of the applicant) use a water cooling system that allows the head to be kept at a low temperature, thus ensuring that NO x emissions remain at a low level throughout the operating range. However, such a cooling system is very expensive and significantly increases the final cost of the burner. Summary of the Invention

[0004] The object of the present disclosure is to provide a burner and a method of burning a gas that overcome the above disadvantages of the prior art. This object is fully achieved by the burner and method of the present disclosure characterized in the appended claims.

[0005] According to one aspect, the present disclosure relates to a gas burner. The gas or gaseous fuel refers to natural gas that mainly includes methane at least. Preferably, the burner is air-cooled. Preferably, the burner does not have a water-cooling system.

[0006] The burner includes a plurality of ramp-shaped (or plate-shaped) elements. The ramp-shaped elements are arranged parallel to each other. More specifically, each ramp-shaped element is located in a corresponding extension plane parallel to the longitudinal direction and the intake direction. Thus, the positioning planes of the ramp-shaped elements are parallel to each other. Each ramp-shaped element includes a first intake duct and a second intake duct. For each ramp-shaped element, the first intake duct and the second intake duct each have a corresponding inlet. For each ramp-shaped element, the first intake duct and the second intake duct may each have a corresponding outlet (each of these outlets extends half of the entire length of the ramp in the longitudinal direction); alternatively, the first intake duct and the second intake duct may have a common outlet (which extends the entire length of the ramp in the longitudinal direction). Preferably, the first intake duct and the second intake duct are geometrically symmetric with each other; more specifically, they are symmetric about an axis oriented along the intake direction and located between the first intake duct and the second intake duct. Preferably, the first intake duct and the second intake duct are configured such that the air-fuel ratio (also known as lambda) is constant, that is, the air-fuel ratios in the first intake duct and the second intake duct are the same.

[0007] In one or more embodiments, each ramp-shaped element further includes a third intake duct. In one embodiment, each ramp-shaped element may further include fourth and / or fifth intake ducts.

[0008] The first intake duct and the second intake duct (and the third and / or fourth and / or fifth intake ducts if provided) are spaced apart from each other along a certain direction; this direction may be the longitudinal direction (in this case, preferably, the inlets of the intake ducts are vertically oriented), or alternatively they may be vertically spaced apart (in this case, preferably, the inlets of the intake ducts are longitudinally oriented). In both of these examples, one or more outlets of the intake ducts may be vertically oriented.

[0009] The first intake duct and the second intake duct (and the third and / or fourth and / or fifth intake ducts, where provided) are spaced apart from each other along the longitudinal direction. The first intake duct and the second intake duct (and the third and / or fourth and / or fifth intake ducts, where provided) extend between an inlet and an outlet in a direction having at least one component parallel to the intake direction. It should be noted that the first intake duct and the second intake duct (and the third and / or fourth and / or fifth intake ducts, where provided) may not be parallel to each other; in fact, each of them extends in a direction having a component parallel to the intake direction, but this direction may also have other components not parallel to the intake direction. A plurality of ramp-shaped elements are arranged continuously along the transverse direction; this transverse direction is perpendicular to the longitudinal direction and the intake direction.

[0010] The burner includes a manifold configured to supply gas to the inlets of the first intake duct and the second intake duct of the ramp-shaped element. More specifically, the manifold includes a plurality of nozzles; the inlets of the first intake duct and the second intake duct of the ramp-shaped element are respectively arranged near the corresponding nozzles to receive the gas flowing out from the nozzles. Thus, for each ramp-shaped element, the manifold includes a first nozzle and a second nozzle (and includes a third and / or fourth and / or fifth nozzle in one or more embodiments). The first intake duct and the second intake duct of the ramp-shaped element are configured to suck gas and primary air into their respective inlets by the Venturi effect. The gas flowing into each duct comes from the corresponding nozzle; the primary air enters the duct from the outer periphery of the inlet of the duct. Inside each Venturi tube, the primary air is mixed with the gas; thus, at the outlet of each duct, there is a mixture of primary air and gas. It should be noted that the diameter of the nozzle is preferably between 0.3 and 1.5 mm (for example, 0.8 mm); in this way, the ratio of the amount of primary air to the amount of gas sucked by the Venturi tube is high enough.

[0011] For each of the plurality of ramp-shaped elements, the burner includes (at least) one corresponding diffuser. The diffuser is arranged at the outlets of the first intake duct and the second intake duct. The diffuser defines a plurality of holes through which flames are generated by the combustion of the gas from the first intake duct and the second intake duct (i.e., by the reaction of the gas with the oxygen present in the primary air).

[0012] It should be noted that according to one aspect of the present disclosure, the geometry of each ramp-shaped element is such that a very large amount of air flows into the duct, so that the combustion of the mixture of primary air and gas occurs under super-stoichiometric conditions at least in part of the operating range (close to the minimum power level), that is, the air exceeds the ideal amount required to produce a complete combustion reaction. Therefore, combustion occurs at a reduced temperature, thereby reducing NO even in the absence of a water cooling system. xGeneration. In particular, the ratio of the width along the transverse direction of the outlets of the first intake duct and the second intake duct of each ramp-shaped element respectively, divided by the spacing along the transverse direction between the first ramp-shaped element and the consecutive second ramp-shaped element, is greater than 0.15 (or 0.16 or 0.17 or 0.18); preferably greater than 0.2 or 0.25; more preferably greater than 0.3 or 0.35 or 0.4. It should be noted that the "spacing" refers to the distance between two corresponding points of two consecutive ramp-shaped elements (especially the first ramp-shaped element and the consecutive second ramp-shaped element). Therefore, the width along the transverse direction of the outlets of the first intake duct and the second intake duct of each ramp-shaped element (also known as the width below the head) is greater than that of the burners of the prior art, which allows a larger amount of primary air to flow in, thus having a beneficial effect in terms of NO x generation.

[0013] For example, the width below the head can be 6 mm (preferably, this width is constant along the longitudinal direction), and the spacing between the first ramp-shaped element and the second ramp-shaped element is 17 mm; in this way, the ratio is 0.353. Compared with the NO x generation amount of 118 mg / kWh in the prior art with a ratio of 0.17 (obtained by a width below the head of 2.9 mm and a spacing between the first ramp-shaped element and the second ramp-shaped element of 17 mm), the NO x generation amount obtained from the experimental test in this example is 96 mg / kWh. Therefore, the tests conducted show that when the width below the head increases and thus the ratio of the width below the head to the spacing between two consecutive ramp-shaped elements increases, the NO x generation amount is improved.

[0014] It should be noted that preferably, the ratio between the maximum (or nominal) thermal power of the burner and the total opening cross-sectional area of the outlets of the ramp-shaped elements is between 3 and 6 W / mm 2 preferably between 4 and 5 W / mm 2 ; for example, in a burner with 17 burner elements having a maximum (or nominal) thermal power of 35 kW and an opening cross-sectional area of 441 mm 2 each (for the first duct and the second duct) at the outlets, the ratio between the maximum thermal power and the total opening cross-sectional area of the outlets of the ramp-shaped elements will be 4.27 W / mm 2 .

[0015] According to another aspect of the present disclosure, between a first ramp-shaped element and a successive second ramp-shaped element, the burner defines an inlet opening (or slot) for directing secondary air towards the diffuser. The secondary air flows through this opening towards the diffuser outside the ducts of the ramp-shaped elements. More specifically, the burner includes a plate positioned between the first ramp-shaped element and the successive second ramp-shaped element. The plate defines (or includes) an opening for the secondary air to pass through (or flow into). Preferably, the burner includes a plurality of openings, with one opening between each pair of successive ramp-shaped elements. More specifically, the burner includes a plurality of plates, that is, it includes a corresponding plate for each pair of successive ramp-shaped elements, which defines a corresponding opening for the secondary air to pass through and is positioned between this pair of ramp-shaped elements.

[0016] The plate (or each plate) for the secondary air is oriented parallel to the transverse direction; more specifically, it is oriented perpendicular to the plane of extension of the ramp-shaped elements. The opening allows the secondary air to flow through it along the intake direction; thus, the secondary air follows a path having at least one component parallel to the intake direction towards the diffuser. The shape of the opening defined in the plate (or in each plate) is elongated along the longitudinal direction. One or more transverse openings may also be defined between the transverse edge of the plate and the wall of the ramp-shaped element; the shape of such one or more transverse openings is preferably elongated along the longitudinal direction. These transverse openings allow the temperature of the head to be reduced, thus avoiding problems caused by the head turning red and incandescing.

[0017] It should be noted that for each of the first ramp-shaped element and the successive second ramp-shaped element, the diffuser is elongated along the longitudinal direction and defines (at least) one corresponding row of holes arranged continuously along the longitudinal direction. The length of the opening for the secondary air to pass through in the longitudinal direction is at least equal to the length of the row of holes in the longitudinal direction.

[0018] The plates for separating the secondary air have beneficial effects in terms of NO x emissions because they reduce the temperature of the diffuser (not only because the inflow of secondary air reduces the combustion temperature, but also because the plates act as heat sinks). However, they make the flame more fluctuating and thus the flame stability worse, increasing the tendency for the flame to detach from the burner. In fact, the lower combustion temperature results in less heating of the head (i.e., lower specific energy), which can cause the flame to detach from the burner and appear at a certain distance from the gas outlet holes. This phenomenon is called flame detachment and is particularly evident at low power. The consequences may be incomplete fuel combustion, and even the flame may go out; incomplete combustion is particularly undesirable because it increases the production of carbon monoxide. Therefore, in the absence of counteracting features, the plates for the secondary air, although beneficial in terms of NO xIt is beneficial in terms of emissions, but especially at low power, it reduces the possibility of regulating the burner.

[0019] According to one aspect of the present disclosure, the manifold includes a first manifold portion configured to supply gas to a first group of ramp-shaped elements and a second manifold portion configured to supply gas to a second group of ramp-shaped elements different from the first group. The manifold includes a partition for separating the first manifold portion from the second manifold portion. The partition is preferably fixed, but it can also be movable. Thus, gas can be supplied to the first and second groups of ramp-shaped elements independently of each other. In this way, when the burner needs to be adjusted to low power, gas can be supplied only to one manifold portion; thus, only some of the plurality of ramp-shaped elements are supplied with gas, thereby reducing the power of the burner while keeping the flame active and stable in the ramp-shaped elements supplied with gas. In fact, the reduction in power is not achieved by reducing the flame propagation speed (which, as described above, would cause flame detachment), but by reducing the number of ramp-shaped elements that remain ignited. This is particularly advantageous when providing plates for separating the secondary air, as these plates tend to increase the tendency of the burner to experience flame detachment, but it is also useful when not providing these plates, as it still allows the burner to operate at low power without changing the operating state of the individual ramp-shaped elements that remain ignited.

[0020] More specifically, the manifold includes a gas supply valve connected to a first gas fitting and a second gas fitting; the gas supply valve is positioned upstream of the first and second gas fittings and regulates the flow of gas to the fittings. More specifically, the gas supply valve is operable to reach its closed position where it blocks the flow of gas to the manifold (i.e., both manifold portions), its partially open position where it allows gas (through the respective gas fittings) to flow to only one of the first and second manifold portions, and its fully open position where it allows gas (through the respective gas fittings) to flow to both the first and second manifold portions. The burner includes a control unit; the control unit is configured to receive an item of information representative of a thermal power request from a user. The control unit is configured to drive the gas supply valve to the closed position, open position, or partially open position according to the thermal power request received from the user.

[0021] It should be noted that the manifold can also include a third and / or fourth gas fitting (and other gas fittings if necessary) connected to a corresponding third and / or fourth manifold portion; the description above regarding the first and / or second gas fittings also applies to the third and / or fourth gas fittings (and any other gas fittings if necessary) with the necessary changes.

[0022] According to one aspect of the present disclosure, each diffuser defines a first row of holes and a second row of holes; the first row of holes and the second row of holes are arranged continuously along the longitudinal direction; the second row of holes is different from and separated from the first row of holes. In other words, the first row and the second row are separated from each other and parallel. The first row of holes and the second row of holes preferably extend continuously along the outlets of the first intake duct and the second intake duct. This arrangement of the holes improves flame stability especially at reduced power.

[0023] According to one aspect of the present disclosure, each ramp-shaped element has a first upper end portion and a second upper end portion that are opposite to each other along the longitudinal direction and are arranged at the upper end portion along the intake direction. The upper end portion refers to the end portion of each ramp-shaped element where the duct for sucking gas into it is provided with respect to the intake direction. The corresponding diffuser is supported on the first upper end portion and the second upper end portion. In an exemplary embodiment, the upper central region of the ramp-shaped element that is located at the upper end portion and is included between (intermediate) the first upper end portion and the second upper end portion is offset (specifically, lower) along the intake direction from the first upper end portion and the second upper end portion; thus, a gap is formed between the diffuser and the upper central region along the intake direction. More specifically, the gap is formed between the wall of the diffuser having holes and the upper central region of the ramp-shaped element. The size of this gap is preferably at least 2 mm. In other words, the diffuser is supported on the first end portion and the second end portion, rather than on the upper central region. This feature helps to reduce the generation of NO x . In other embodiments, no gap is provided (i.e., it is 0 mm).

[0024] The present disclosure also provides a boiler including a combustion chamber and a burner according to one or more aspects of the present disclosure. The boiler can be of an open combustion chamber type or a closed combustion chamber type (i.e., equipped with a fan for discharging combustion flue gas).

[0025] The present disclosure also provides a method of combusting a gas. The method includes the step of preparing a plurality of ramp-shaped elements; these ramp-shaped elements are formed according to one or more aspects of the present disclosure; more specifically, these ramp-shaped elements are oriented parallel to each other and are arranged continuously along a transverse direction perpendicular to the plane of extension of the ramp-shaped elements. For each of the plurality of ramp-shaped elements, the method includes preparing a corresponding diffuser. The diffuser is provided at the outlets of the first intake duct and the second intake duct (thus covering the outlets of the first intake duct and the second intake duct). The diffuser is formed according to one or more aspects of the present disclosure.

[0026] The method includes the step of supplying gas to the inlets of the first intake duct and the second intake duct (and the third and / or fourth and / or fifth intake ducts if provided) of the plurality of ramp-shaped elements through a manifold. The manifold is formed according to one or more aspects of the present disclosure.

[0027] The method includes the step of sucking gas and primary air into a first intake duct and a second intake duct of a plurality of ramp-shaped elements by the Venturi effect.

[0028] The method includes, for each of the plurality of ramp-shaped elements, the step of generating a flame from the holes of a corresponding diffuser by combustion of the gas from the first intake duct and the second intake duct. An igniter provided near the diffuser can be used to ignite the flame.

[0029] The method preferably includes the step of supplying secondary air through an opening defined in a plate positioned between a first ramp-shaped element and a successive second ramp-shaped element of the plurality of ramp-shaped elements.

[0030] The method can include the step of selectively supplying gas to a first manifold portion configured to supply gas to a first group of ramp-shaped elements or a second manifold portion configured to supply gas to a second group of ramp-shaped elements different from the first group. The first manifold portion is separate from the second manifold portion. More specifically, the method can include the step of controlling a gas supply valve to drive it to its closed position where it blocks the flow of gas to the manifolds, its partially open position where it allows gas to flow to only one of the first manifold portion and the second manifold portion, and its fully open position where it allows gas to flow to both the first manifold portion and the second manifold portion.

[0031] Thus, the present disclosure provides many viable features for reducing NO x emissions and at the same time avoiding flame detachment. These features can be adopted individually or in combination. The results of experimental tests conducted on the burner of the present disclosure are shown by way of example below. The experimental tests were carried out using a fuel gas called the second family as the reference gas, that is, a gas composed of 100% methane (represented by the label G20 in European regulations). First, a burner with 17 ramp-shaped elements of the type described in the applicant's document WO2016 / 193904, which has no cooling system, was used; the measured amount of initially generated NO x was 137 mg / kWh. Then the nozzle size was reduced to 0.8 mm, thereby obtaining a measured amount of NO x of 128 mg / kWh. Next, the cross-sectional area of the openings in the burner head was increased to 441 mm 2 ; due to this change, a measured amount of NO x of 118 mg / kWh was obtained. Next, the outlet widths of the first intake duct and the second intake duct were increased to 6 mm; due to this change, a measured amount of NO xNext, the central region of the upper end portion of the ramp-shaped element is lowered, thereby obtaining a measured amount of NO of 92 mg / kWh x . It is noted that the benefits of these changes in NO x production are offset by the deterioration of the burner characteristics in terms of flame detachment (resulting in an increase in carbon monoxide production from an initial 340 ppm by 30 ppm). Then, a plate for separating the secondary air is implemented and two separate gas fittings are provided; due to these measures, a measured amount of NO x is observed to drop to 57 mg / kWh and the measured amount of carbon monoxide drops to 418 ppm. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] These and other features will become more apparent from the following detailed description of the preferred embodiments shown by way of non-limiting example in the drawings, in which:

[0033] - Figure 1 A burner according to one or more aspects of the present disclosure is shown in a perspective view;

[0034] - Figure 2 The burner of Figure 1 is shown in another perspective view;

[0035] - Figure 3 The burner of Figure 1 is shown in a top view;

[0036] - Figure 4 The burner of Figure 1 is shown in a side view;

[0037] - Figure 5 and Figure 6 show three ramp-shaped elements of the burner of Figure 1 having corresponding diffusers and corresponding plates for secondary air;

[0038] - Figure 7 and Figure 8 show a single ramp-shaped element of the burner of Figure 1 ;

[0039] - Figure 9 shows a plate for secondary air of the burner of Figure 1 ;

[0040] - Figure 10A and Figure 10B respectively show embodiments of diffusers of the burner of Figure 1 . DETAILED DESCRIPTION

[0041] For the present disclosure, reference numeral 1 denotes a burner. The burner 1 includes a plurality of ramp-shaped elements 2. The ramp-shaped elements 2 are oriented along respective extension planes parallel to the longitudinal direction L and the intake direction A. The intake direction A is perpendicular to the longitudinal direction L. The ramp-shaped elements 2 are arranged side by side along the transverse direction T. The transverse direction T is perpendicular to the longitudinal direction L and the intake direction A.

[0042] Each ramp-shaped element 2 includes a first intake duct 21 and a second intake duct 22. The first intake duct 21 and the second intake duct 22 are shaped as Venturi tubes, that is to say, they include a converging portion and a diverging portion located downstream of the converging portion. The first intake duct 21 and the second intake duct 22 have respective inlets 21A, 22A and respective outlets 21B, 22B. The first intake duct 21 and the second intake duct 22 are oriented along a direction having at least one component parallel to the intake direction A; in one embodiment, they are oriented along a direction parallel to the intake direction A. Thus, the inlet 21A of the first duct is offset along the intake direction A from the outlet 21B of the first duct; similarly, the inlet 22A of the second duct is offset along the intake direction A from the outlet 22B of the second duct.

[0043] In the drawings, the letter P denotes the spacing between a pair of consecutive ramp-shaped elements 2; the spacing P is the distance between two corresponding points of the pair of consecutive ramp-shaped elements 2. Preferably, the spacing can be between 15 and 20 mm (for example, 17 mm).

[0044] The burner 1 includes a manifold 3 which is configured to supply gas to the inlets 21A of the first intake ducts 21 and the inlets 22A of the second intake ducts 22 of the ramp-shaped elements 2. More specifically, the manifold 3 includes a first duct 31 and a second duct 32 which are oriented in the transverse direction T and are parallel to each other. The ducts 31 and 32 are each provided with a plurality of nozzles 33. Each nozzle 33 is positioned at the inlet of an intake duct. More specifically, the nozzles 33 of the first duct 31 are positioned near the respective inlets 21A of the first ducts 21, and the nozzles 33 of the second duct 32 are positioned near the respective inlets 22A of the second ducts 22. The first duct 31 and the second duct 32 are each divided into a first part and a second part by an internal partition. Thus, the first part of the first duct 31 and the first part of the second duct 32 form a first part 36 of the manifold 3 for supplying the first group 2A of ramp-shaped elements 2. The second part of the first duct 31 and the second part of the second duct 32 form a second part 37 of the manifold 3 for supplying the second group 2B of ramp-shaped elements 2. The manifold 3 further includes a first gas fitting 34 connected to the first part 36 of the manifold 3 and a second gas fitting 35 connected to the second part 37 of the manifold 3. The first gas fitting 34 and the second gas fitting 35 can be supplied independently of each other.

[0045] The burner 1 includes a plurality of diffusers 4. Each diffuser 4 is positioned at the outlet 21B of the first intake duct 21 and the outlet 22B of the second intake duct 22 of a respective ramp-shaped element 2. Each diffuser 4 covers the outlet 21B of the first intake duct 21 and the outlet 22B of the second intake duct 22. Each diffuser 4 defines a plurality of holes 40 for generating a flame. The holes 40 are arranged in at least one row in an orderly manner along the longitudinal direction L. More specifically, in one embodiment, the holes 40 are arranged along a first row 40A and a second row 40B that are oriented in the longitudinal direction L and parallel to each other; in this embodiment, the holes 40 of the first row 40A are separated from the holes 40 of the second row 40B.

[0046] It should be noted that each ramp-shaped element 2 has a first upper end 20A and a second upper end 20B; the first upper end 20A and the second upper end 20B are positioned opposite to each other on the upper side of the burner 1. The upper side refers to the side that is at a greater vertical height when the burner 1 is positioned such that the flame extends vertically (i.e., along the intake direction A). The diffuser 4 is fixed to the first upper end 20A and the second upper end 20B.

[0047] The upper side is variable in height along the intake direction A. More specifically, the first upper end 20A and the second upper end 20B are elevated relative to the upper central region that defines the outlet 21B of the first intake duct 21 and the outlet 22B of the second intake duct 22. The offset between the first (or second) upper end 20A (20B) and the upper central region along the intake direction A is denoted as D2. Due to this offset D2, the wall of the diffuser 4 that defines the holes 40 does not rest on the upper central region, and thus a gap is formed between the wall of the diffuser 4 and the upper central region of the ramp-shaped element 2.

[0048] It should be noted that the width of the respective outlets 21B, 22B of the first intake duct 21 and the second intake duct 22 of each ramp-shaped element 2 along the transverse direction T is denoted as D1. The width D1 is preferably equal for the first intake duct 21 and the second intake duct 22. The width D1 is greater than a respective minimum value; thus, the ratio between the width D1 and the spacing P between the first ramp-shaped element 2 and the consecutive second ramp-shaped element 2 is also greater than a respective minimum value (0.15 or 0.2 or 0.25 or 0.3). Preferably, the ratio between D1 and the maximum width of the plate 5 in the transverse direction T is between 0.4 and 0.6 (e.g., it can be 0.5, where D1 is 6 mm and the width of the plate 5 is 12 mm).

[0049] Preferably, the ratio of the sum of the cross-sectional areas of the outlet 21B of the first intake duct 21 and the outlet 22B of the second intake duct 22 divided by the spacing P in the transverse direction T between the first ramp-shaped element 2 and the successive second ramp-shaped element 2 is between 40 and 60 (or between 45 and 55, or between 50 and 55). When calculating this ratio, the cross-sectional area can be expressed in mm 2 and the spacing can be expressed in mm. The cross-sectional area of flow is the cross-sectional area having a width D1. For example, the sum of the cross-sectional areas of flow can be 899 mm 2 and the spacing is 17 mm, so the ratio defined as above is 52.9.

[0050] Preferably, the ratio of the sum of the minimum cross-sectional areas of the first intake duct 21 and the second intake duct 22 divided by the spacing P in the transverse direction T between the first ramp-shaped element 2 and the successive second ramp-shaped element 2 is between 8 and 15 (or between 9 and 14, or between 10 and 13). When calculating this ratio, the cross-sectional area can be expressed in mm 2 and the spacing can be expressed in mm. Preferably, the minimum cross-sectional areas of the intake ducts 21, 22 are defined in the duct sections oriented parallel to the intake direction; this section preferably defines a region 202 having a constant cross-sectional area. For example, the sum of the minimum cross-sectional areas of flow of the first duct and the second duct can be 190 mm 2 and the spacing is 17 mm, so the ratio defined as above is 11.2.

[0051] The burner 1 includes a plurality of plates 5. Each plate 5 is interposed between a pair of adjacent ramp-shaped elements 2. Each plate 5 is oriented in a plane parallel to the longitudinal direction L and the transverse direction T. Each plate 5 defines an opening 50 for separating secondary air. The axis of the opening 50 is parallel to the intake direction A; in other words, the opening 50 allows secondary air to flow therethrough along the intake direction A. Each plate 5 has a first surface facing the inlet 21A of the first intake duct 21 and the inlet 22A of the second intake duct 22, and a second surface opposite the first surface, facing the outlet 21B of the first intake duct 21 and the outlet 22B of the second intake duct 22. The opening 50 is located in the central region of the plate 5, equidistant from the two adjacent ramp-shaped elements 2 and elongated in shape along the longitudinal direction L. Preferably, the width of the opening 50 is constant along the transverse direction T. The length of the opening 50 in the longitudinal direction L is (at least) equal to the length of a row of holes 40 of the diffuser 4; thus, the secondary air can flow uniformly along the flame. The ratio between the width of the opening 50 in the transverse direction T and the (maximum) width of the plate 5 in the transverse direction T is preferably between 0.05 and 0.1; for example, it can be 0.083 (where the width of the opening 50 is 1 mm and the maximum width of the plate 5 is 12 mm).

[0052] It should be noted that the width of each plate 5 in the transverse direction T is preferably not constant; in fact, at least at the first end and the second end opposite the first end, the plate 5 has a first width (or maximum width), and a second width smaller than the first width in the region between the first end and the second end. There may also be a portion with the first width in the central region between the first end and the second end (preferably equidistant from the first end and the second end); in this case, the plate 5 has the first width at its first end, in the central region, and has a second width smaller than the first width at its second end, in the intermediate region between the first end and the central region, and in the intermediate region between the central region and the second end. The ratio of the first width to the second width can be between 1.1 and 1.3 (for example, it can be 1.2); for example, the first width of the plate 5 can be 12 mm, and the second width can be 10 mm. The lengths of the regions with the first width located at the first end, in the central region, and at the second end along the longitudinal direction L are each 0.01 to 0.05 (for example, 0.03) times the total length of the plate 5 in the longitudinal direction L. For example, the length of the plate 5 in the longitudinal direction L can be 155 mm, and the length of each region with the first width in the longitudinal direction L can be 5 mm.

[0053] Thus, an additional opening (or side opening) 51 is defined between the edge of the plate 5 in the region having the second width and the wall of the ramp-shaped element 2. The shape of the additional opening 51 is elongated in the longitudinal direction. The additional opening 51 facilitates the cooling of the head.

[0054] This shape improves the heat dissipation from the diffuser 4 through the plate 5.

[0055] The burner 1 includes a frame on which the ramp-shaped element 2 and the manifold 3 are mounted. The frame includes a first side bracket 61A and a second side bracket 61B, between which the ramp-shaped element 2 is positioned. More specifically, the first side bracket 61A is connected to the first ramp-shaped element 2 and the second side bracket 61B is connected to the last ramp-shaped element 2 among the successive ramp-shaped elements 2. The other ramp-shaped elements 2 are positioned between the first ramp-shaped element 2 and the last ramp-shaped element 2 and are connected to each other. The frame further includes a first connecting element 62A and a second connecting element 62B. The first connecting element 62A is connected to the first side bracket 61A and defines an opening for receiving the first end of the manifold 3. The second connecting element 62B is connected to the second side bracket 61B and defines an opening for receiving the second end of the manifold 3 opposite to the first end.

[0056] It should be noted that preferably, the ratio of the occupied area of the outlets of the first intake duct 21 and the second intake duct 22 divided by the pitch P is between 55 and 70 (or between 60 and 65). The "occupied area" refers to the sum of the cross-sectional area of the fluid flow plus the thickness of the duct wall. For example, the occupied area may be 1094 mm 2 and the pitch may be 17 mm, so the ratio defined as above is 64.4.

[0057] It should be noted that each of the intake ducts 21, 22 preferably includes a first region 201 having a converging cross-section, a second region 202 connected to the first region 201 and having a constant cross-section (the second region is preferably vertically oriented), a third region 203 connected to the second region 202 and having a diverging cross-section, a fourth region 204 connected to the third region and also having a diverging cross-section inclined at a greater angle relative to the intake direction A than the third region 203, and a fifth region 205 connected to the fourth region and having a constant cross-section that defines the outlet of the duct. The fifth region 205 may also be referred to as the region below the head. Preferably, in the interconnecting region between the third region 203 and the fourth region 204, the ratio of the sum of the cross-sectional areas of the first duct 21 and the second duct 22 divided by the pitch P is between 20 and 30 (or between 24 and 28). For example, in the interconnecting region between the third region and the fourth region, the sum of the cross-sectional areas of the first duct 21 and the second duct 22 may be 452 mm and the pitch is 17 mm, so the ratio is 26.6.

[0058] It should be noted that the holes 40 of each diffuser are inscribed in a rectangle. Preferably, the ratio between the area of the rectangle circumscribing the holes 40 and the pitch P is between 50 and 70 (or between 55 and 65). For example, the area of the rectangle can be 988 mm 2 and the pitch is 17 mm, so the ratio is 58.1.

[0059] Preferably, the ratio of the sum of the cross-sectional areas of the holes 40 among the plurality of holes 40 divided by the pitch P is between 22 and 30 (or between 23 and 26). For example, the sum of the cross-sectional areas of the holes 40 can be 419 mm and the pitch is 17 mm, so the ratio is 24.6.

[0060] The sum of the cross-sectional areas of the holes 40 among the plurality of holes divided by the rectangle circumscribing the holes 40 defines the porosity of each diffuser 4. Preferably, the porosity of each diffuser 4 is between 0.35 and 0.43 (or between 0.4 and 0.42).

[0061] The following paragraphs, listed in alphanumeric order for reference, are non-limiting examples for describing the present invention.

[0062] A. A module for a gas burner, comprising:

[0063] - A ramp element (2) which is arranged along a respective extension plane parallel to the longitudinal direction (L) and the air intake direction (A) and comprises a first air intake duct (21) and a second air intake duct (22) having respective inlets (21A, 22A) and outlets (21B, 22B), wherein the first air intake duct (21) and the second air intake duct (22) are oriented in the extension plane of the respective ramp element (2);

[0064] - A diffuser (4) which is arranged at the outlets (21B, 22B) of the first air intake duct (21) and the second air intake duct (22) and defines a plurality of holes (40), from which flames are generated by the combustion of the gas from the first air intake duct (21) and the second air intake duct (22).

[0065] A1. The module according to paragraph A, wherein the first air intake duct (21) and the second air intake duct (22) extend between the inlets (21A, 22A) and the outlets (21B, 22B) in a direction having at least one component parallel to the air intake direction (A).

[0066] Module according to paragraph A or A1, wherein the diffuser (4) extends along a longitudinal direction (L) and defines a first row (40A) of holes (40) and a second row (40B) of holes (40) that are continuously arranged along the longitudinal direction (L), and wherein the second row (40B) of holes (40) is different from and separated from the first row (40A) of holes (40).

[0067] Module according to paragraph A2, wherein the first row (40A) of holes (40) and the second row (40B) of holes (40) extend along the outlets (21B, 22B) of the first intake duct (21) and the second intake duct (22), and the outlets extend along the entire length of the longitudinal direction (L).

[0068] Module according to any one of paragraphs A to A2.1, wherein each ramp element (2) has a first upper end (2A) and a second upper end (2B) that face each other along the longitudinal direction (L) and are arranged at the upper end portions along the intake direction (A), and wherein the corresponding diffuser (4) is supported on the first upper end and the second upper end, and wherein the upper central region of the ramp element (2) that is included between the first upper end (2A) and the second upper end (2B) is lower than the first upper end (2A) and the second upper end (2B) along the intake direction (A), so that a gap is defined between the diffuser (4) and the upper central region along the intake direction (A).

[0069] Module according to any one of paragraphs A to A3, wherein the ratio between the maximum (or nominal) thermal power generated by gas combustion and the total outlet cross-sectional area of the first duct and the second duct of the ramp element (2) is between 2 and 6 (preferably between 3 and 5).

[0070] Module according to any one of paragraphs A to A4, wherein each ramp element (2) among the plurality of ramp elements (2) has a corresponding outlet (21B, 22B).

[0071] Module according to any one of paragraphs A to A4, wherein the plurality of ramp elements (2) have a common outlet.

[0072] Module according to any one of paragraphs A to A6, wherein the intake direction (A) is vertical.

[0073] Module according to paragraph A7, wherein the inlets (21A, 22A) and the outlets (21B, 22B) of the intake ducts (21) are vertically oriented.

[0074] Module according to paragraph A7 or A7.1, wherein the manifold (3) is positioned lower than the intake ducts (21), and the inlets (21A, 22A) are positioned above the manifold (3).

[0075] A8. A module according to any one of paragraphs A to A7.2, wherein the longitudinal direction (L) is orthogonal to the intake direction (A).

[0076] A9. A module according to any one of paragraphs A to A8, wherein the first intake duct (21) and the second intake duct (22) are spaced apart from each other along a predetermined direction.

[0077] A9.1. A module according to paragraph A9, wherein the predetermined direction is the longitudinal direction (L).

[0078] A10. A module according to any one of paragraphs A to A9.1, wherein the first intake duct (21) and the second intake duct (22) are vertically spaced apart from each other.

[0079] A10.1. A module according to paragraph A10, wherein the manifold (3) is located on one side of the intake duct (21).

[0080] A10.2. A module according to paragraph A10 or A10.1, wherein the inlets (21A, 22A) are oriented along the longitudinal direction (L), and the outlet (21B, 22B) or the outlets (21B, 22B) are vertically oriented.

[0081] B. A burner comprising a plurality of modules according to any one of paragraphs A to A10, wherein a plurality of ramp-shaped elements (2) are continuously arranged along a transverse direction (T) perpendicular to the longitudinal direction (L) and the intake direction (A).

[0082] B1. The burner according to paragraph B, comprising a manifold (3) configured to supply gas to the inlets of the first intake duct (21) and the second intake duct (22) of a plurality of ramp-shaped elements (2), wherein the first intake duct (21) and the second intake duct (22) of the plurality of ramp-shaped elements (2) are configured to suck gas and primary air into their respective inlets (21A, 22A) by the Venturi effect.

[0083] B2. The burner according to paragraph B or B1, wherein the ratio of the width of the transverse direction (T) of the outlets (21B, 22B) of the first intake duct (21) and the second intake duct (22) of each ramp-shaped element (2) to the spacing (P) in the transverse direction (T) between the first ramp-shaped element (2) and the consecutive second ramp-shaped element (2) is greater than 0.15 (preferably greater than 0.2, more preferably greater than 0.3 or 0.35).

[0084] B3. Burner according to any one of paragraphs B to B2, wherein the ratio of the sum of the cross-sectional flow areas of the outlet (21B) of the first intake duct (21) and the outlet (22B) of the second intake duct (22) to the spacing (P) in the transverse direction (T) between the first ramp element (2) and the successive second ramp element (2) is between 40 and 60 (or between 45 and 55, or between 50 and 55).

[0085] B4. Burner according to any one of paragraphs B to B3, wherein the ratio of the sum of the minimum cross-sectional flow areas of the first intake duct (21) and the second intake duct (22) to the spacing (P) in the transverse direction (T) between the first ramp element (2) and the successive second ramp element (2) is between 8 and 15 (or between 9 and 14, or between 10 and 13).

[0086] B5. Burner according to any one of paragraphs B to B4, comprising an opening (50) for the passage of secondary air between the first ramp element (2) and the successive second ramp element (2).

[0087] B5.1. Burner according to paragraph B5, comprising a plate (5) located between the first ramp element (2) and the successive second ramp element (2), wherein the plate defines an opening (50) for the passage of secondary air.

[0088] B5.1.1. Burner according to paragraph B5.1, wherein the plate (5) is oriented parallel to the transverse direction (T).

[0089] B5.2. Burner according to any one of paragraphs B5 to B5.1.1, wherein the opening (50) allows secondary air to flow therethrough along the intake direction (A) and / or extends along the longitudinal direction (L).

[0090] B5.3. Burner according to any one of paragraphs B5 to B5.3, comprising a respective plate (5) and an opening (50) for the passage of secondary air and located between a pair of successive ramp elements (2) for each pair of successive ramp elements (2) among the plurality of ramp elements (2).

[0091] B6. Burner according to any one of paragraphs B to B5.3, wherein the manifold (3) comprises a first manifold part (36) configured to supply gas to a first group (2A) of ramp-shaped elements (2) and a second manifold part (37) configured to supply gas to a second group (2B) of ramp-shaped elements (2) different from the first group (2A), and wherein the burner (1) comprises a first fitting (34) for supplying gas to the first manifold part (36) and a second fitting (35) for supplying gas to the second manifold part (37).

[0092] B6.1. Burner according to paragraph B6, comprising a gas supply valve connected to the first gas fitting (34) and the second gas fitting (35) and operable to a closed position in which it blocks the flow of gas to the manifold (3), a partially open position in which it allows gas to flow only to one of the first manifold part (36) and the second manifold part (37), and a fully open position in which it allows gas to flow to both the first manifold part (36) and the second manifold part (37).

[0093] B6.1.1. Burner according to paragraph B6.1, comprising a control unit configured to drive the gas supply valve to the closed position, the open position or the partially open position according to a thermal power request received from a user.

[0094] B7. Burner according to any one of paragraphs B to B6.1.1, wherein the burner is air-cooled.

[0095] C. A boiler comprising a combustion chamber and a burner (1) according to any one of the preceding paragraphs.

[0096] D. A method of combusting a gas, comprising the steps of:

[0097] - preparing a plurality of ramp-shaped elements (2), each arranged along a respective plane of extension parallel to the longitudinal direction (L) and the intake direction (A) and comprising a first intake duct (21) and a second intake duct (22) having respective inlets (21A, 22A) and outlets (21B, 22B), wherein the first intake duct (21) and the second intake duct (22) are oriented in the plane of extension of the respective ramp-shaped element (2), and wherein the plurality of ramp-shaped elements (2) are arranged continuously along a transverse direction (T) perpendicular to the longitudinal direction (L) and the intake direction (A);

[0098] - preparing a respective diffuser (4) for each of the plurality of ramp-shaped elements (2), which is arranged at the outlet of the first intake duct (21) and at the outlets (21B, 22B) of the second intake duct (22) and defines a plurality of holes (40);

[0099] - Supply gas to the inlets (21A, 21B) of the first intake pipe (21) and the second intake pipe (22) of a plurality of ramp-shaped elements (2) through a manifold (3);

[0100] - Draw in gas and primary air into the first intake pipe (21) and the second intake pipe (22) of a plurality of ramp-shaped elements (2) by the Venturi effect;

[0101] - For each of the plurality of ramp-shaped elements (2), generate a flame from the holes (40) of the corresponding diffuser (4) by combustion of the gas from the first intake pipe (21) and the second intake pipe (22).

[0102] D1. The method according to paragraph D, wherein the ratio of the width along the transverse direction (T) of the outlets (21B, 22B) of the first intake pipe (21) and the second intake pipe (22) of each ramp-shaped element (2) to the spacing (P) along the transverse direction (T) between the first ramp-shaped element (2) and the consecutive second ramp-shaped element (2) is greater than 0.15 (preferably greater than 0.2, more preferably greater than 0.3).

[0103] D2. The method according to paragraph D or D1, wherein the ratio of the sum of the cross-sectional areas of the flow passages of the outlet (21B) of the first intake pipe (21) plus the cross-sectional area of the flow passage of the outlet (22B) of the second intake pipe (22) to the spacing (P) along the transverse direction (T) between the first ramp-shaped element (2) and the consecutive second ramp-shaped element (2) is between 40 and 60 (or between 45 and 55, or between 50 and 55).

[0104] D3. The method according to any one of paragraphs D to D2, wherein the ratio of the sum of the minimum cross-sectional areas of the flow passages of the first intake pipe (21) plus the minimum cross-sectional area of the flow passage of the second intake pipe (22) to the spacing (P) along the transverse direction (T) between the first ramp-shaped element (2) and the consecutive second ramp-shaped element (2) is between 8 and 15 (or between 9 and 14, or between 10 and 13).

[0105] D4. The method according to any one of paragraphs D to D3, which includes the step of supplying secondary air through an opening (50) or slot defined between the first ramp-shaped element (2) and the consecutive second ramp-shaped element (2) among a plurality of ramp-shaped elements (2).

[0106] D4.1. The method according to paragraph D4, wherein the opening (50) is defined in a plate (5) located between the first ramp-shaped element (2) and the consecutive second ramp-shaped element (2).

[0107] D4.1.1. According to the method of paragraph D4.1, wherein the opening (50) extends along the longitudinal direction (L).

[0108] D5. According to the method of any one of paragraphs D to D4.1.1, wherein the manifold (3) includes a first manifold portion (36) configured to supply gas to a first group (2A) of ramp-shaped elements (2) and a second manifold portion (37) configured to supply gas to a second group (2B) of ramp-shaped elements (2) different from the first group (2A), and wherein the method includes the step of selectively supplying gas to the first manifold portion (36) and / or the second manifold portion (37).

[0109] D5.1. According to the method of paragraph D5, wherein the step of selective supply includes controlling a gas supply valve in accordance with a heat power request received from a user to drive it to a partially open position where it allows gas to flow only to one of the first manifold portion (36) and the second manifold portion (37), or to a fully open position where it allows gas to flow to the first manifold portion (36) and the second manifold portion (37).

[0110] D6. According to the method of any one of paragraphs D to D5.1, which includes an air cooling step, that is, wherein water cooling is not provided.

[0111] D7. According to the method of any one of paragraphs D to D6, wherein each of the plurality of ramp-shaped elements (2) has a respective outlet (21B, 22B).

[0112] D8. According to the method of any one of paragraphs D to D6, wherein the plurality of ramp-shaped elements (2) have a common outlet.

[0113] D9. According to the method of any one of paragraphs D to D8, wherein the intake direction (A) is vertical.

[0114] D9.1. According to the method of paragraph D9, wherein the inlets (21A, 22A) and outlets (21B, 22B) of the intake ducts (21) are vertically oriented.

[0115] D9.2. According to the method of paragraph D9 or D9.1, wherein the manifold (3) is positioned lower than the intake ducts (21), and the inlets (21A, 22A) are positioned above the manifold (3).

[0116] D10. According to the module of any one of paragraphs D to D9.2, wherein the longitudinal direction (L) is orthogonal to the intake direction (A).

[0117] D11. According to the module of any one of paragraphs D to D10, wherein the first intake duct (21) and the second intake duct (22) are spaced apart from each other along a predetermined direction.

[0118] Module according to paragraph D11, where the predetermined direction is the longitudinal direction (L).

[0119] Module according to any one of paragraphs D to D11.1, where the first intake duct (21) and the second intake duct (22) are vertically spaced apart from each other.

[0120] Module according to paragraph D12, where the manifold (3) is located on one side of the intake duct (21).

[0121] Module according to paragraph D12 or D12.1, where the inlets (21A, 22A) are oriented along the longitudinal direction (L), and the outlet (21B, 22B) or the plurality of outlets (21B, 22B) are vertically oriented.

Claims

1. An air-cooled gas burner, which comprises: - a plurality of ramp-shaped elements, each of which is arranged parallel to the longitudinal direction and parallel to the air inlet direction along a corresponding extension plane and includes a first air inlet duct and a second air inlet duct having corresponding inlets and outlets, wherein the first air inlet duct and the second air inlet duct are oriented in the extension plane of the corresponding ramp-shaped element and are spaced apart from each other along the longitudinal direction, and wherein a plurality of the ramp-shaped elements are continuously arranged along a transverse direction perpendicular to the longitudinal direction and perpendicular to the air inlet direction; - a manifold configured to supply gas to the inlets of the first air inlet ducts and the second air inlet ducts of the plurality of ramp-shaped elements, wherein the first air inlet ducts and the second air inlet ducts of the plurality of ramp-shaped elements are configured to suck gas and primary air into their respective inlets by the Venturi effect; - a corresponding diffuser for each of the plurality of ramp-shaped elements, which is provided at the outlets of the first air inlet duct and the second air inlet duct and defines a plurality of holes, and flames are generated from the holes by the combustion of the gas from the first air inlet duct and the second air inlet duct; the gas burner includes a plate positioned between the first ramp-shaped element and the consecutive second ramp-shaped element, wherein the plate defines an opening for the secondary air to pass through; For each of the first ramp-shaped element and the consecutive second ramp-shaped element, the diffuser extends along the longitudinal direction and defines a corresponding row of holes continuously arranged along the longitudinal direction, wherein the length of the opening for the secondary air to pass through along the longitudinal direction is at least equal to the length of the row of holes along the longitudinal direction.

2. The gas burner according to claim 1, wherein, the plate is oriented parallel to the transverse direction, and the opening allows the secondary air to flow therethrough along the air inlet direction and extends along the longitudinal direction.

3. The gas burner according to claim 1 or 2, which includes a corresponding plate for each pair of consecutive ramp-shaped elements among the plurality of ramp-shaped elements, the plate defines a corresponding opening for the secondary air to pass through and is positioned between the paired ramp-shaped elements.

4. The gas burner according to claim 1 or 2, wherein, the ratio of the width of the outlet of each first air inlet duct and each second air inlet duct of each ramp-shaped element along the transverse direction to the spacing along the transverse direction between the first ramp-shaped element and the consecutive second ramp-shaped element is greater than 0.

15.

5. The gas burner according to claim 1 or 2, wherein, the ratio of the sum of the cross-sectional areas of the outlets of the first air inlet duct and the cross-sectional areas of the outlets of the second air inlet duct divided by the spacing along the transverse direction between the first ramp-shaped element and the consecutive second ramp-shaped element is between 40 and 60.

6. The gas burner according to claim 1 or 2, wherein, The ratio of the sum of the minimum flow cross-sectional area of the first intake duct and the minimum flow cross-sectional area of the second intake duct to the spacing along the transverse direction between the first ramp element and the successive second ramp element is between 8 and 15.

7. The gas burner according to claim 1 or 2, wherein, the first intake duct and the second intake duct of each of the ramp elements extend between an inlet and an outlet in a direction having at least one component parallel to the intake direction.

8. The gas burner according to claim 1 or 2, wherein, the manifold includes a first manifold portion configured to supply gas to a first group of the ramp elements and a second manifold portion configured to supply gas to a second group of the ramp elements different from the first group, and wherein the gas burner includes a first fitting for supplying gas to the first manifold portion and a second fitting for supplying gas to the second manifold portion.

9. The gas burner according to claim 8, which includes a gas supply valve connected to the first fitting and the second fitting and operable to a closed position in which it blocks the flow of gas to the manifold, a partially open position in which it only allows the flow of gas to one of the first manifold portion and the second manifold portion, and a fully open position in which it allows the flow of gas to both the first manifold portion and the second manifold portion.

10. The gas burner according to claim 1 or 2, wherein, each of the diffusers extends along the longitudinal direction and defines a first row of holes and a second row of holes that are successively arranged along the longitudinal direction, wherein the second row of holes is different from and separated from the first row of holes.

11. The gas burner according to claim 1 or 2, wherein, each of the ramp elements has a first upper end portion and a second upper end portion that are opposite to each other along the longitudinal direction and are arranged at the upper end portion of the ramp element along the intake direction, wherein the corresponding diffuser is supported on the first upper end portion and the second upper end portion, and wherein an upper central region of the ramp element between the first upper end portion and the second upper end portion is offset from the first upper end portion and the second upper end portion along the intake direction, thereby defining a gap between the wall of the diffuser having the holes and the upper central region along the intake direction.

12. The gas burner according to claim 1 or 2, wherein, the first intake duct and the second intake duct in each of the ramp elements are geometrically symmetric to each other.

13. The gas burner according to claim 1 or 2, wherein, the intake direction is vertical and the longitudinal direction is orthogonal to the intake direction.

14. The gas burner according to claim 1 or 2, wherein, one of the following conditions is satisfied: i) each of the ramp elements among the plurality of ramp elements has a corresponding outlet; ii) the plurality of ramp elements have a common outlet.

15. A boiler, comprising a combustion chamber and a gas burner according to claim 1 or 2.

16. A method of combusting a gas, which comprises the following steps: - Preparing an air-cooled gas burner, wherein the gas burner comprises a plurality of ramp-shaped elements, each of which is arranged parallel to the longitudinal direction and parallel to the intake direction along a respective extension plane and comprises a first intake duct and a second intake duct having respective inlets and outlets, wherein the first intake duct and the second intake duct are oriented in the extension plane of the respective ramp-shaped element and are spaced apart from each other along the longitudinal direction, and wherein the plurality of ramp-shaped elements are arranged continuously along a transverse direction perpendicular to the longitudinal direction and perpendicular to the intake direction, wherein the gas burner further comprises a respective diffuser for each of the plurality of ramp-shaped elements, which is arranged at the outlets of the first intake duct and the second intake duct and defines a plurality of holes; - Supplying gas to the inlets of the first intake duct and the second intake duct of the plurality of ramp-shaped elements through a manifold; - Drawing gas and primary air into the first intake duct and the second intake duct of the plurality of ramp-shaped elements by the Venturi effect; - For each of the plurality of ramp-shaped elements, generating a flame from the holes of the respective diffuser by combustion of the gas from the first intake duct and the second intake duct; - A step of supplying secondary air through an opening defined in a plate, the plate being positioned between the first ramp-shaped element and the consecutive second ramp-shaped element among the plurality of ramp-shaped elements, wherein, for each of the first ramp-shaped element and the consecutive second ramp-shaped element, the diffuser extends along the longitudinal direction and defines a respective row of holes arranged continuously along the longitudinal direction, and wherein the length of the opening for passing the secondary air along the longitudinal direction is at least equal to the length of the row of holes along the longitudinal direction.

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