CN212644589U - Gas premixing system suitable for feeding a burner and boiler - Google Patents

Abstract

The present invention relates to a gas premixing system and boiler adapted to feed a burner. The gas premixing system comprises: a premixing body defining a premixing chamber including an inlet for an air/gas mixture and configured to supply the air/gas mixture to a burner; and a staging device dividing the premixing chamber into first and second sections, the first section being configured to feed a first region of the combustor and the second section being configured to feed a second region of the combustor, the staging device comprising an enclosure device configured to prevent the passage of an air/gas mixture between the two sections of the premixing chamber. The sectioning means comprise a sectioning element defining a closed profile inside the premixing chamber, the closed profile being a second section, the first section externally surrounding the sectioning element. The sectional element comprises an opening which communicates the two sections of the premixing chamber, the closing means closing the opening in the closed position, so that the gas/air mixture reaches only the first section in the closed position.

Description

Gas premixing system suitable for feeding a burner and boiler

Technical Field

The present invention relates to a gas premixing system adapted to feed a burner, in particular a burner of a condensing boiler, and a boiler comprising such a gas premixing system.

Background

Combustion systems suitable for boilers or water heaters are known, comprising a combustion system in which fuel (preferably gas) is mixed with air driven by means of a fan before being fed to the corresponding burner.

Document WO2008/066223a1 describes a combustion device of a boiler, which improves the boiler regulation. The device includes: a fan; a proportional control valve for controlling the gas supply; a plurality of injectors connected in parallel to each other and connected to the proportional control valve and supplying gas according to opening and closing of the auxiliary valve; a premixing chamber for mixing air and gas before the burner; and a control device for controlling the number of rotations of the fan according to opening and closing of a proportional control valve and an auxiliary valve, which allow only an amount of air required for combustion to be supplied.

Document EP 339499 a2 discloses a burner divided into two parts. The first portion having a smaller surface has larger holes for generating a longer flame. The second portion having a larger surface has smaller pores than the first portion. The burner in turn includes an ionization sensor disposed on the first portion. Furthermore, the burner comprises mixing ducts which extend from the lower part of the burner and are fed by common air and fuel ducts. The mixing duct feeding the first part contains a smaller proportion of air than the mixing duct feeding the second part, so as to produce a longer flame in the first part of the burner.

Document DE 19635974 a1 discloses a combustion system comprising: a fan; a combustion premixing device having a body defining a premixing chamber and an inlet to the premixing chamber for a fuel and air mixture; and a burner having a combustion zone supplied with a fuel gas mixture. The premixing device includes a lug for controlling passage through an opening communicating with the combustion zone. The lug moves in accordance with the amount of air directed towards the combustion chamber, thereby changing the cross-section of the opening. The combustion zone is always the same, i.e. remains constant. The lobe allows for control of flow to the combustion zone.

Documents DE 19728965 a1 and EP 2975324 a1 disclose a combustion system comprising: a fan; a combustion premixing device having a body defining a premixing chamber and an inlet to the premixing chamber for a fuel and air mixture; and a burner having a combustion region to which a fuel gas mixture can be supplied. The premixing device includes a lobe that, when driven by the gas and fuel mixture, adjusts the combustion region of the combustor, the lobe moving between a position of minimum combustor power, at which the lobe restricts the mixture from entering a first portion of the combustion region, and a position of maximum combustor power, at which the lobe is disposed substantially orthogonally such that the mixture may enter the entire combustion region.

SUMMERY OF THE UTILITY MODEL

It is an object of the present invention to provide a gas premixing system adapted to feed burners, in particular burners of condensing boilers.

According to the utility model discloses a gas mixes system in advance includes: a premixing body defining a premixing chamber including an inlet for an air/gas mixture, the premixing chamber being configured to supply the air/gas mixture to a burner; and a staging device dividing the premixing chamber into at least a first section and a second section, the first section being configured to feed a first region of the combustor and the second section being configured to feed a second region of the combustor, the staging device comprising a closure device configured to prevent passage of an air/gas mixture between the first section and the second section of the premixing chamber.

The segmenting device comprises a segmenting element which delimits a closed contour inside the premixing chamber, said closed contour being a second section, the first section externally surrounding the segmenting element, the segmenting element comprising an opening which communicates the first and second sections of the premixing chamber, the closure device closing said opening in the closed position, so that the gas/air mixture only reaches the first section in the closed position.

Hereby is obtained a premix system which achieves a very high power regulation ratio, i.e. a ratio of more than 1:30, by controlling the emission of CO and NOx generated at low power. Furthermore, the premixing system allows operation at low power densities with ionization signals that are larger than the prior art and sufficiently stable so that they can be detected.

These and other advantages and features of the invention will be readily understood in view of the drawings and the detailed description of the invention.

Drawings

Fig. 1 shows a schematic view of a condensing boiler comprising a gas premixing system according to the present invention.

Fig. 2 shows a top view of the burner of the condensing boiler shown in fig. 1.

FIG. 3 illustrates a front view of the premixing system illustrated schematically in FIG. 1 with the staging device in a first configuration.

FIG. 4 illustrates a perspective view of the premixing system illustrated in FIG. 3.

FIG. 5 illustrates a cross-sectional view of the premixing system illustrated in FIG. 3.

FIG. 6 illustrates a detailed view of a first configuration of a staging device included in the premixing system illustrated in FIG. 3.

FIG. 7 illustrates another detailed view of a first configuration of a staging device included in the premixing system illustrated in FIG. 3.

FIG. 8 illustrates a cross-sectional view of a first configuration of a staging device included in the premixing system illustrated in FIG. 3.

FIG. 9 illustrates a detailed view of a second configuration of a staging device included in the premixing system illustrated in FIG. 3.

Fig. 10 shows a cross-sectional view of the segmenting means shown in fig. 9.

FIG. 11 illustrates a detailed view of a third configuration of a staging device included in the premixing system illustrated in FIG. 3.

Fig. 12 shows a cross-sectional view of the segmenting means shown in fig. 11.

FIG. 13 illustrates a cross-sectional view of a fourth configuration of a staging device included in the premixing system illustrated in FIG. 3.

Detailed Description

Fig. 1 schematically shows a combustion system 1 of a condensing boiler. In addition to the combustion system 1, the condensation boiler comprises an exchanger 7 in which heat exchange takes place between the combustion gases generated in the combustion chamber 2 of the combustion system 1 and the heated fluid circulating through the main circuit, and an outlet duct 8 for the gases generated in the combustion chamber 2.

The combustion system 1 of the boiler comprises a burner 9 housed in the combustion chamber 2 and a premixing system 10 according to the present invention, the premixing system 10 being configured to feed a mixture of air and fuel, preferably gas, to said burner 9.

Although a premixing system adapted to a burner of a condensing boiler is described below, the premixing system according to the present invention is not limited to boilers, but may be used for burners of other appliances such as ovens, fryers, etc.

The premixing system 10 includes: at least one air intake duct 6 a; a mixing device 6, the mixing device 6 communicating with the intake duct 6a and being supplied with air 6b, the gas and the air being mixed in the mixing device 6; at least one valve 5, the at least one valve 5 configured to regulate a flow rate of gas into the mixing device 6; and a fan 4, the fan 4 configured to meter a volume of air introduced into the premixing system 10. The mixing device 6 draws in air by means of the fan 4 and, when a certain pressure is detected in the mixing device, activates the corresponding valve 5, which valve 5 will control the amount of gas to be mixed with the air. The mixture driven by the fan 4 is directed towards the premixing body 11 of the premixing system 10 through the feed conduit 3.

The premixing body 11 of the premixing system 10, shown in detail in fig. 3 to 5, delimits a premixing chamber 12 and comprises an inlet 13 connected to the feed conduit 3 and communicating with the premixing chamber 12, the premixing chamber 12 being configured to allow the passage of the air and gas mixture towards the burner 9. The thorough mixing of the gas and air in the mixture takes place in said premixing chamber 12, directing the flow towards the burner 9 in laminar flow to obtain a specific velocity field of the air-gas mixture at the outlet of the burner 9, and thus a more uniform flame of the burner 9.

The premixing system 10 according to the present invention comprises a segmenting device 14, 14', 14 "' (shown in detail in fig. 6 to 13), which segmenting device 14, 14', 14"' divides the premixing chamber 12 into at least a first section a and a second section B, said first section a being configured to feed a first region C (shown in fig. 2) of the burner 9 and said second section B being configured to feed a second region D (shown in fig. 2) of the burner 9, the first region C externally surrounding the second region D of the burner 9. The sectioning means 14, 14', 14 ", 14'" symmetrically divide the burner (first zone C and second zone D) so as to ensure the uniformity of the flame inside the combustion chamber 2 and the uniform heat transfer to the exchanger 7, while preventing losses of efficiency of the premixing system 10, hot spots in the zone of the combustion chamber 9 and greater ageing of the material of the zone and of the lugs of the exchanger 7. The regions of the burner 9 which are separated by the segmenting means 14, 14', 14 ", 14'" are substantially concentric with one another. Ignition and flame detection electrodes (not shown) of the combustion system 1 are arranged in the first region C of the burner 9 to ensure that the burner is on and to allow detection of a suitable flame detection signal throughout the power range.

In the embodiment depicted, the burner 9 has a disk shape as schematically shown in fig. 2, so that a first zone C fed through the first section a of the premixing chamber 12 has a circular ring-shaped geometry and a second zone D fed through the second section B of the premixing chamber 12 has a disk-shaped geometry, the first zone C surrounding the second zone D. The ratio between the areas of the burners 9 (i.e. the ratio between the area of the first zone C and the area of the second zone D) defines the power density of the burners 9 at low power.

In other not shown embodiments, the burner 9 may have another geometry, but the first zone C will still surround the second zone D, the two zones being substantially concentric with each other. Thus, the burner 9 operates symmetrically at any power.

The segmenting means 14, 14', 14 "' comprise a segmenting element 15, which segmenting element 15 delimits a closed contour inside the premixing chamber 12, said closed contour being a second section B, the first section a externally surrounding the segmenting element 15. The sectional element 15 comprises an opening 20 which communicates the sections a and B of the premixing chamber 12. The segmenting means 14, 14', 14 "' further comprise closing means 17, 17', 17"', which closing means 17, 17', 17 "' are configured to prevent the passage of the air/gas mixture between the two sections a and B of the premixing chamber 12 in the closed position. In this position, the closure device 17, 17', 17 ", 17'" blocks the opening 20 so that the air/gas mixture reaches only the first section a in the closed position. The closed position corresponds to operation of the boiler at low power. In said case, the air/gas mixture is distributed only to the first zone C of the burner 9, so that the flame is generated only in the first zone C of the burner 9 (outer ring of the burner 9) as described above. Above a certain operating power of the boiler (transition power), the closing means 17, 17', 17 ", 17'" no longer block the opening 20, allowing the air/gas mixture to also enter the second section B, i.e. above the transition power, the air/gas mixture reaches the entire surface of the burner 9.

In the embodiment shown in the figures, the first section a and the second section B are arranged substantially concentrically to each other.

The sectional element 15 comprises a base 15c and a wall 15a extending from the base 15c, the wall 15a having a tubular geometry. A wall 15a separates the first section a from the second section B. Fig. 6 to 10 show different configurations of the sectional element 15, each configuration corresponding to an embodiment of the premixing system according to the present invention. In the configuration shown in the figures, the wall 15a is substantially cylindrical, but in other embodiments the tubular wall may have a prismatic geometry. Regardless of the specific geometry of the tubular wall, the wall 15a comprises an opening 20, which opening 20 is configured to allow the gas/air mixture to enter the second section B in the open position. In the configuration shown in the figures, the wall 15a comprises a planar portion 15b, the planar portion 15b comprising an opening 20. The planar portion 15b is disposed facing the inlet 13. The opening 20 of the sectional element 15 is preferably arranged such that it is aligned with the inlet 13 of the premixing body 11.

In the configuration of the segmenting means 14, 14', 14 ", 14'" shown in fig. 6 to 13, the segmenting element 15 is made of a metallic material, in particular of aluminum. As shown in fig. 5, the sectional element 15 extends until it contacts the homogenizing plate 23 which delimits said premixing chamber 12 with the premixing body 11. Thereby obtaining lower CO and NOx emissions. The homogenizing plate 23 is known in the art and therefore a more detailed description is not considered necessary.

Furthermore, the closing means 17, 17', 17 "' comprise a flap (flap)18, 18' configured to close the opening 20. The baffles 18, 18' are arranged to face the inlet 13 of the premixing body 11 in the closed position. The closing means 17, 17', 17 ", 17'" are passive means, i.e. the baffle 18, 18 'blocks the opening 20 until the flow rate of the air/gas mixture entering the premixing chamber 12 through the inlet 13 exerts sufficient pressure on the baffle 18, 18' to move it with respect to the opening 20 and allow the air/gas mixture to pass also to the second section B, which occurs when the boiler is operating above the transition power. The opening 20 of the sectional element 15 is arranged such that it is aligned with the inlet 13 of the premixing body 11 to reduce head loss above transition power.

In the configuration of the sectioning arrangement shown in the figures, the baffles 18, 18' are arranged such that they are pivotably secured to the sectioning element 15. In particular, the baffles 18, 18' are arranged so that they are coupled to the planar portion 15b of the sectional element 15 by means of an axis not shown in the figures.

Furthermore, the closing means 17, 17', 17 ", 17 '" comprise magnetic means 19, 19', which magnetic means 19, 19' are configured to keep the flaps 18, 18' against the sectional element 15 in the closed position to keep the passage of the air/gas mixture closed between the two sections a and B. An on-off system is thereby obtained, wherein emissions at low power are minimized and a higher regulation ratio can be achieved.

In the configuration of the segmented means 14, 14', 14 ", 14'" shown in fig. 6 to 10, the magnetic means 19 comprise at least several magnets fixed to the segmented element 15, in particular to the planar portion 15b of the segmented element 15. In particular, in the embodiment shown in fig. 6 to 8, the shutter 18 is made of a metallic material, in particular of a ferromagnetic metallic material. When the boiler is operating at low power, the attraction force exerted by said magnetic means 19 against the shutter 18 exceeds the pressure exerted by the air/gas mixture on the shutter 18, so that the passage towards the second section B remains closed. In the configuration of the segmented device 14 'shown in fig. 9 and 10, the baffle 18' is a film made of a polymer material and comprises at least one ferromagnetic metal part or ferromagnetic coating 21. In this configuration, the metal part 21 surrounds the baffle 18'. At low power, the magnetic means 19 exert an attractive force on the metal part 21 of the shutter 18 'which is greater than the pressure exerted by the air/gas mixture on the shutter 18'.

In other configurations of the staging device 14 ", the magnets may be disposed in the baffle rather than in the pre-mix body. Thus, in the configuration shown in fig. 11 and 12, the magnetic means 19' comprise a magnet arranged in the baffle 18 and at least one ferromagnetic metal part or ferromagnetic coating 24 located in the sectional element 15, in particular in the planar portion 15b of the sectional element 15. In the configuration shown in fig. 11 and 12, the baffle 18 is a metal baffle, but it may also be a polymer baffle 18'.

Furthermore, the closing means 17, 17', 17 "' of the segmenting means 14, 14', 14" ' of the premixing system 10 according to the present invention comprise sealing means 25, 25', which sealing means 25, 25' are configured to seal the flap 18, 18' against the closure formed by the segmenting element 15, thereby preventing leakage towards the second section B in the closed position, which contributes to obtaining a better regulation ratio.

In the configuration of the segmented means 14, 14', 14 "shown in fig. 5 to 12, the sealing means 25 are arranged such that they are fixed to the segmented element 15, in particular to the planar portion 15b of the segmented element 15, around the periphery of the opening 20.

In the configuration of the segmented device shown in fig. 13, a sealing device 25 'is arranged in the baffle 18, said sealing device 25' being configured to seal the periphery of the opening 20 of the segmented element 15. In particular, the sealing means 25' comprise a gasket surrounding the periphery of the baffle 18. Preferably, the gasket is a rubber gasket. In the configuration shown in fig. 13, the baffle 18 is a ferromagnetic baffle, but it may also be a polymeric baffle 18'. The magnetic means 19' are arranged in the shutter 18 and are at least partially inserted in the rubber gasket. The magnetic means 19' are arranged so that they are adhered or screwed to the rubber gasket.

In other configurations not shown in the figures, the segmented device may comprise a segmented element having magnetic means configured according to any of the described configurations without comprising sealing means, and vice versa, the segmented device may comprise a segmented element having sealing means configured according to any of the described configurations without comprising magnetic means.

Claims (15)

1. A gas premixing system adapted to feed a combustor, the gas premixing system comprising: a premixing body (11), the premixing body (11) defining a premixing chamber (12), the premixing chamber (12) comprising an inlet (13) for an air/gas mixture, the premixing chamber (12) being configured to feed the air/gas mixture to the burner (9); and a segmenting device (14, 14', 14 "') dividing the premixing chamber (12) into at least a first section (A) and a second section (B), the first section (A) being configured to feed a first region (C) of the combustor (9) and the second section (B) being configured to feed a second region (D) of the combustor (9), the segmenting device (14, 14', 14"') comprising a closing device (17, 17', 17 "') configured to prevent the air/gas mixture from passing between the first section (A) and the second section (B) of the premixing chamber (12),

characterized in that said segmenting means (14, 14', 14 "') comprise a segmenting element (15), said segmenting element (15) delimiting inside said premixing chamber (12) a closed contour, said closed contour being said second section (B), said first section (A) externally surrounding said segmenting element (15), said segmenting element (15) comprising an opening (20), said opening (20) putting in communication the first and second sections (A, B) of said premixing chamber (12), said closing means (17, 17', 17"') closing said opening (20) in a closed position, so that in said closed position the air/gas mixture reaches only said first section (A).

2. Gas premixing system according to claim 1 characterized in that said sectional element (15) has a wall (15a) of tubular geometry separating said first section (a) from said second section (B).

3. Gas premixing system according to claim 2, characterized in that said wall (15a) comprises a planar portion (15b), said planar portion (15b) being arranged facing said inlet (13) of said premixing body (11), and said inlet (13) and said opening (20) comprised in said planar portion (15b) being arranged so that they are aligned with each other.

4. Gas premixing system suitable for feeding a burner according to any of the claims 1 to 3 characterized in that said closing means (17, 17', 17 "') are passive means.

5. Gas premixing system suitable for feeding burners according to claim 1, characterized in that said closing means (17, 17', 17 "') comprise: a shutter (18, 18'), said shutter (18, 18') being configured to close said opening (20); and magnetic means (19, 19'), said magnetic means (19, 19') being configured to keep said shutter (18, 18') against said sectional element (15) in said closed position, so as to keep the passage of said air/gas mixture between said first section (a) and said second section (B) closed.

6. Gas premixing system suitable for feeding a burner according to claim 5 characterized in that said baffle (18, 18') is pivotable with respect to said sectional element (15), said baffle (18, 18') being arranged facing said inlet (13) in said closed position, so that said air/gas mixture entering said premixing chamber (12) through said inlet (13) in said closed position is orthogonal to said baffle (18, 18 ').

7. Gas premixing system suitable for feeding burners according to claim 5 or 6, characterized in that said baffle (18) is made of ferromagnetic metallic material.

8. Gas premixing system suitable for feeding burners according to claim 5 or 6, characterized in that said baffle (18') is made of polymeric material and comprises ferromagnetic metal parts or ferromagnetic coatings (21).

9. Gas premixing system suitable for feeding burners according to claim 5 or 6 characterized in that said magnetic means (19) comprise permanent magnets fixed to said sectional element (15).

10. Gas premixing system suitable for feeding burners according to claim 5 or 6 characterized in that said magnetic means (19') comprise permanent magnets fixed to said baffles (18, 18') and said sectional element (15) comprises a ferromagnetic metal part or coating (24).

11. Gas premixing system suitable for feeding a burner according to claim 5 or 6 characterized in that said closing means (17, 17', 17 ") comprise sealing means (25), said sealing means (25) surrounding the periphery of said opening (20) and being fixed to said sectional element (15), said sealing means (25) being configured to form a closed seal of said baffle (18, 18') against said sectional element (15).

12. Gas premixing system suitable for feeding a burner according to claim 5 or 6 characterized in that said closing means (17 "') comprise sealing means (25') fixed to said baffles (18, 18'), said sealing means (25') being configured to seal the perimeter of said opening (20) of said sectional element (15).

13. Gas premixing system according to any of the claims 1 to 3 characterized in that said sectional element (15) is housed in said premixing body (11), said sectional element (15) being configured to contact a homogenizing plate (23) delimiting said premixing chamber (12) together with said premixing body (11).

14. Gas premixing system suitable for feeding a burner according to any of the claims 1 to 3 characterized in that said first section (A) and said second section (B) are arranged concentrically to each other.

15. A boiler comprising a burner (9) and a gas premixing system (10) adapted to feed a burner according to any of claims 1-14.

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