EP4290135A1

EP4290135A1 - Premix gas burner

Info

Publication number: EP4290135A1
Application number: EP22382547.2A
Authority: EP
Inventors: Ane Miren SIERRA BALENZIAGA; Mikel OCAÑA SOLA; Aimar ARIN GUTIERREZ
Original assignee: Orkli SCL
Current assignee: Orkli SCL
Priority date: 2022-06-08
Filing date: 2022-06-08
Publication date: 2023-12-13

Abstract

Premix gas burner for a gas boiler comprising a combustion area and a mixing unit communicated with the combustion area, with a mixture of an oxidizer and a fuel being generated in the mixing unit, which mixture is driven towards the combustion area by a fan. The burner further comprises between the mixing unit and the combustion area a first passage area 5 comprising a first shutter 6 which, in a resting position, prevents the passage of the mixture, with said first shutter 6 being configured for being moved and allowing the passage of the mixture when the mixture exerts a pressure higher than a first threshold pressure on said shutter 6, and a second passage area arranged between the first passage area 5 and the combustion area comprising a second shutter 7. The second shutter 7 comprises a resting position in which the passage of a minimum flow rate of the mixture through the second passage area is allowed, with the second shutter 7 being configured for being moved and allowing the passage of a larger flow rate of the mixture when said mixture exerts a pressure higher than a second threshold pressure greater than the first threshold pressure.

Description

TECHNICAL FIELD

The present invention relates to premix gas burners, particularly to burners comprising several passage areas for the mixture of an oxidizer and a fuel.

PRIOR ART

Premix gas burners comprising several passage areas for the mixture of an oxidizer, for example air, and a fuel, for example gas, are known.
EP3754267A1 , for example, describes a gas burner comprising a combustion area and a mixing unit communicated with the combustion area, a mixture of air and gas being generated in the mixing unit. The mixing unit comprises a fan driving the mixture towards the combustion area according to a flow direction, the burner further comprising between the mixing unit and the combustion area a first passage area comprising a first shutter which, in a resting position, prevents the passage of the mixture and is configured for being moved and allowing the passage of the mixture when the mixture exerts a threshold pressure on said first shutter, and a second passage area between the first passage area and the combustion area comprising a second shutter. Like the first shutter, the second shutter also comprises a resting position which prevents the passage of the mixture, being configured for being moved and allowing the passage of the mixture when the mixture exerts the threshold pressure on said second shutter. Each shutter, therefore, acts like a non-return valve, providing a burner with dual safety.

DISCLOSURE OF THE INVENTION

The object of the invention is to provide a premix gas burner, as defined in the claims.
The premix gas burner of the invention comprises a combustion area and a mixing unit communicated with the combustion area, a mixture of an oxidizer and a fuel being generated in the mixing unit, which mixture is driven towards the combustion area according to a flow direction by a fan comprised in the mixing unit. The oxidizer is preferably air and the fuel is preferably gas. The burner further comprises between the mixing unit and the combustion area a first passage area comprising a first shutter which, in a resting position, prevents the passage of the mixture, said first shutter being configured for being moved and allowing the passage of the mixture when the mixture exerts a pressure higher than a first threshold pressure on said shutter, and a second passage area arranged between the first passage area and the combustion area comprising a second shutter. The second shutter comprises a resting position in which the passage of a minimum flow rate of the mixture through the second passage area is allowed, he second shutter being configured for being moved and allowing the passage of a larger flow rate of the mixture when said mixture exerts a pressure higher than a second threshold pressure greater than the first threshold pressure.
With the burner of the invention, it is possible to stabilize the burner when working at low power. When the mixing unit supplies a minimum flow rate, the burner is said to work at a low power and when the mixing unit supplies a maximum flow rate, the burner is said to work at a high power, with a modulation ratio, which is the ratio of minimum to maximum power, being defined.
When the fan, which drives the flow of the mixture generated towards the combustion area, works at low powers, i.e., at low revolutions per minute, it is usually unstable and can cause a back-and-forth opening and closing movement in the corresponding shutter, changing the section of the corresponding passage area. In the burner of the invention, it is not necessary to move the second shutter so as to allow the passage of the minimum flow rate of the mixture, and therefore said back-and-forth movement is removed when the burner works at low power. Furthermore, the pressure to be exerted by the mixture on the second shutter (second threshold pressure) is larger than the pressure to be exerted in order to move the first shutter (first threshold pressure), which allows the power of the fan to be increased in order to supply the same minimum flow rate, whereby the fan, and accordingly the burner as well, is more stable. Moreover, in the burner of the invention it is also possible to reduce the minimum flow rate even further, maintaining the stability in the supply of said minimum flow rate, thereby enabling the modulation ratio of the burner to be expanded.
Like the first shutter, while in the resting position, it does not allow the passage of the mixture, acting as a non-return valve, preventing the flame from being able to move back in the event of a malfunction of the burner. Therefore, the burner of the invention provides a more stable burner when it works at low power without sacrificing safety, and with the possibility of expanding the modulation ratio.
These and other advantages and features of the invention will become apparent in view of the figures and of the detailed description of the invention.

DESCRIPTION OF THE DRAWINGS

Figure 1 shows a perspective view of the burner according to a first embodiment of the invention.
Figure 2 is an exploded perspective view of the burning of Figure 1 but without the main conduit and without the combustion area.
Figure 3 shows a first sectioned detail of the valve assembly and the sealing gasket of the burner of Figure 1.
Figure 4A shows a first sectioned perspective view of the valve assembly, the sealing gasket, the transition part of the mixing unit and of the main conduit of the burner of Figure 1, with the first shutter and second shutter being depicted in the resting position.
Figure 4B shows a second sectioned perspective view of the valve assembly, the sealing gasket, the transition part of the mixing unit and of the main conduit of the burner of Figure 1, wherein the second shutter is depicted in the resting position and the first shutter is depicted displaced from its resting position.
Figure 4C shows a third sectioned perspective view of the valve assembly, the sealing gasket, the transition part of the mixing unit and of the main conduit of the burner of Figure 1, wherein both the first shutter and second shutter are depicted displaced from their resting position.

DETAILED DISCLOSURE OF THE INVENTION

Figure 1 shows a premix gas burner 100 associated with a gas boiler not shown in the figures. The gas burner 100 of the invention comprises a combustion area 1 and a mixing unit 2 communicated with the combustion area 1, with a mixture of an oxidizer and a fuel being generated in the mixing unit 2, which mixture is driven towards the combustion area 1 according to a flow direction A by a fan 2.1 comprised in the mixing unit 2. Preferably, the oxidizer is air and the fuel is gas. The burner 100 further comprises between the mixing unit 2 and the combustion area 1 a first passage area 5 comprising a first shutter 6 which, in a resting position, prevents the passage of the mixture, as seen in Figure 4A, with said first shutter 6 being configured for being moved and allowing the passage of the mixture when the mixture exerts a pressure higher than a first threshold pressure on said first shutter 6 according to the flow direction A, as seen in Figure 4B. The burner 100 also comprises a second passage area 8 arranged between the first passage area 5 and the combustion area 1 comprising a second shutter 7, with the second shutter 7 therefore being arranged downstream of the first shutter 6 according to the flow direction A. The second shutter 7 comprises a resting position in which the passage of a minimum flow rate of the mixture through the second passage area 8 is allowed, with the second shutter 7 being configured for being moved and allowing the passage of a larger flow rate of the mixture when said mixture exerts a pressure higher than a second threshold pressure greater than the first threshold pressure, as seen in Figure 4C.
With the burner 100 of the invention, the gas boiler associated with said burner 100 is successfully stabilised when the gas boiler works at low power. When the mixing unit 2 supplies a minimum flow rate, the burner 100, i.e., the boiler, is said to work at low power, and when the mixing unit 2 supplies a maximum flow rate, the burner 100, i.e., the boiler, is said to work at high power, the modulation ratio of a boiler being defined as the ratio between the minimum and maximum power. The higher the modulation ratio, the greater the capability of the boiler to adapt to different power needs that are required, both in heating and in domestic hot water (DHW). On one hand, this allows the number of times the boiler is switched on and off, but on the other hand, the greater the modulation ratio of the boiler the greater the comfort perceived by the user. As a result of improvements in new technologies (for example in the incorporation of thermostatic taps, radiant floor heating, etc.), it is increasingly more common to encounter situations in which the powers required by the heating system such as domestic hot water (DHW) can be very low, so it is necessary for gas boilers to be very stable, even at low powers.
When the fan 2.1, which drives the flow of the mixture generated towards the combustion area 1, works at low powers, i.e., at low revolutions per minute, it is usually unstable and can cause a back-and forth opening and closing movement in the corresponding shutter, changing the section of the corresponding passage area. In the burner 100 of the invention, it is not necessary to move the second shutter 7 so as to allow the passage of the minimum flow rate of the mixture, and therefore said back-and-forth movement is removed when the burner 100 works at low power. Furthermore, the pressure to be exerted by the mixture on the second shutter 7 (second threshold pressure) is larger than the pressure to be exerted in order to move the first shutter 6 (first threshold pressure), which allows the power of the fan 2.1 to be increased in order to supply the same minimum flow rate, whereby the fan 2.1, and accordingly the burner 100 as well, is more stable. Moreover, as the pressure drop in the burner 100 of the invention increases as a result of the second shutter 7, it is possible to reduce the minimum flow rate even further, maintaining the stability in the supply of said minimum flow rate, thereby enabling the modulation ratio of the burner to be expanded 100.
Moreover, with the first shutter 6 in the resting position, it does not allow the passage of the mixture and therefore acts as a non-return valve, preventing the flame from being able to move back in the event of a malfunction of the burner 100. Therefore, the burner 100 of the invention provides a more stable burner 100 when the boiler works at low power without sacrificing safety, and with the possibility of expanding the modulation ratio of the burner 100.
In the preferred embodiment of the invention, the second shutter 7 comprises a through hole 7.1, preferably having a circular section although the shape of the hole is not relevant, which allows the passage of the minimum flow rate when said second shutter 7 is in the resting position. The through hole 7.1 can be arranged in the geometric centre of the second shutter 7, as shown in Figure 2 for example, or on one side, the positioning thereof not being relevant provided that it allows the passage of said minimum flow rate.
In another embodiment not shown in the Figures, the second shutter 7 is smaller than the second passage area 8, such that with the second shutter 7 in the resting position, between the second shutter 7 and the second passage area 8 there is such a clearance that the passage of the minimum flow rate is allowed through said clearance. In a non-limiting example, the clearance between the second shutter 7 and the second passage area 8 is arranged on the peripheral contour of the second shutter 7, for example on the sides of said second shutter 7, as will be described in detail below.
As shown in Figure 1, the combustion area 1 and the mixing unit 2 are communicated through a main conduit 3. Said main conduit 3 and the combustion area 1 preferably form a single part. The main conduit 3 and the mixing unit 2 are attached through a flange 3.1, such that the disassembly of the burner 100 is allowed, which is advantageous for burner 100 maintenance.
In the preferred embodiment of the invention, a valve assembly 4 is arranged inside said main conduit 3, preferably close to the flange 3.1. Said valve assembly 4 comprises the first shutter 6 and the second shutter 7, as will be described in detail below.
The mixing unit 2 comprises the fan 2.1, as shown in Figure 1, but also comprises an inlet conduit for the oxidizer and an inlet conduit for the fuel, which are not shown in the drawings, with said inlet conduit for the fuel being associated with a valve that regulates the amount of fuel. The fan 2.1 causes the mixture of the oxidizer and the fuel inside the mixing unit 2, the fan 2.1 driving said mixture towards the combustion area 1 according to the flow direction A through the first passage area 5 and the second passage area 8.
The mixing unit 2 runs into a transition part 9 which is circular, as shown in the example of Figure 2, said transition part 9 being part of the flange 3.1 so as to allow the attachment with the main conduit 3. The transition part 9 comprises a main passage opening 5.1, which defines the first passage area 5, so as to allow the passage of the mixture towards the combustion area 1 when the first shutter 6 is displaced from the resting position, pushed by the mixture itself as it exceeds the first threshold pressure.
As shown in the detail of Figure 4A, the transition part 9 comprises a frame 9.1 surrounding the main passage opening 5.1 of the mixing unit 2, such that in the resting position the first shutter 6 rests on said frame 9.1, blocking the passage of the mixture in both directions, i.e., from the first passage area 5 towards the combustion area 1 according to the flow direction A and vice versa, i.e., from the combustion area 1 towards the mixing unit 2.
As seen in the detail of Figure 3, the valve assembly 4, which in use is arranged inside the main conduit 3, comprises a hollow main body 10, with there being formed therein a passage channel 10.3 running into the second passage area 8, such that the flow of the mixture exiting the first passage area 5 when said mixture exerts a pressure higher than the first threshold pressure on the first shutter 6 is directed towards the second passage area 8 through said passage channel 10.3. The passage area 8 comprises an additional passage opening 8.1, as shown in Figure 2.
The valve assembly 4 comprises a frame 10.1 surrounding the additional passage opening 8.1 and may also comprise a rib 10.2 going through the second passage area 8 and, therefore, divides the additional passage opening 8.1 in two, such that in the resting position the second shutter 7 rests on at least part of said frame 10.1 and/or on the rib 10.2. When the second shutter 7 does not comprise the through hole 7.1 which allows the passage of the minimum flow rate towards the combustion area 1, the second shutter 7 can rest on the rib 10.2 in order to maintain the second shutter 7 in the resting position, thus allowing the necessary clearance between the peripheral edge of the second shutter 7 and the frame 10.1 to be generated so as to allow the passage of the minimum flow rate of the mixture towards the combustion area 1. In the absence of the rib 10.2 dividing the additional passage opening 8.1, part of the second shutter 7, for example the front part, can be supported on part of the frame 10.1, whereas the necessary clearance is provided on the sides of the second shutter 7 so as to allow the passage of the minimum flow rate of the mixture.
Figure 4B depicts the position of the first shutter 6 and of the second shutter 7 corresponding to the boiler's low power operating mode. The first shutter 6 is displaced from its resting position pushed by the mixture after exceeding the first threshold pressure, but said mixture does not yet exert sufficient pressure on the second shutter 7 to exceed the second threshold pressure, and therefore the second shutter 7 remains in its resting position, such that the flow rate passing through the through hole 7.1, i.e., the minimum flow rate, is directed towards the combustion area 1 in a stable manner, without all the back-and-forth. Although there can be a small back-and-forth movement in the first shutter 6 due to the instability of the fan 2.1 by working at low power, the second shutter 7 remains stable in the resting position.
Figure 4C depicts the position of the first shutter 6 and of the second shutter 7 when the boiler is working in normal mode, i.e., according to a power between the minimum and maximum power. In this operating mode, both shutters 6 and 7 are displaced with respect to their corresponding resting positions. The first shutter 6 is displaced from its resting position pushed by the mixture, after exceeding the first threshold pressure, and the second shutter 7 is also displaced pushed by the mixture after exceeding the second threshold pressure.
In the preferred embodiment of the invention the second shutter 7 is heavier than the first shutter 6, preferably twice as heavy or heavier, and very preferably three times as heavy or heavier. Since the second shutter 7 is heavier, it is also more robust than the first shutter 6 such that said second shutter 7 exerts greater resistance to the passage of the flow of the mixture, which allows assuring, when working at minimum powers, that the second shutter 7 remains in the resting position without producing unwanted back-and-forth movements, while the passage of the minimum flow rate is allowed through the through hole 7.1 of the second shutter 7.
In the preferred embodiment of the invention, the second shutter 7 comprises an active area 7a and a non-active area 7b, with the active area 7a being configured for bending with respect to the non-active area 7b when the mixture exerts a pressure on the active area 7a higher than the second threshold pressure, moving the second shutter 7 away from the resting position. The second shutter 7 comprises an axial protuberance 7.3 arranged in the non-active area 7b which is housed in a housing 13 of the valve assembly 4, as seen in Figure 3, to retain the non-active area 7b in the valve assembly 4, particularly in the main body 10 of the valve assembly 4.
To assure the correct assembly of the second shutter 7 in the main body 10 of the valve assembly 4, the second shutter 7 may comprise a stop 7.31, arranged perpendicular to the protuberance 7.3, as seen in Figure 3, which cooperates with a wall 13a surrounding the housing 13 so as to delimit the penetration of the non-active area 7b of the second shutter 7 in said housing 13. The protuberance 7.3 and the stop 7.31 (if it comprises said stop 7.31) are arranged in the non-active area 7b.
In the preferred embodiment of the invention, the thickness of the active area 7a is greater than the thickness of the non-active area 7b, providing a transition area 7c between both areas 7a and 7b, that is preferably curved, which favours the active area 7a being able to bend with respect to the non-active area 7b when pushed by the mixture upon exceeding the second threshold pressure, such that the transition area 7c becomes the pivoting shaft of the second shutter 7.
The second shutter 7 is made with a flexible material, preferably silicone, which favours it being able to bend about its pivoting shaft more easily, i.e., on the transition area 7c, said transition area 7c being arranged between the active area 7a and the assembly formed by assembling the protuberance 7.3 in the housing 13 of the main body 10.
The burner 100 of the invention also comprises a sealing gasket 11, which is arranged in the attachment area between the main conduit 3 and the mixing unit 2, for hermetically sealing said attachment area. Since the valve assembly 4 is arranged inside the main conduit 3, the sealing gasket 11 is also arranged between the mixing unit 2 and the valve assembly 4, as shown in Figure 2, hermetically sealing the mixing unit 2 and the valve assembly 4, thereby assuring that the entire mixture flows from the first passage area 5 towards the combustion area 1 through the passage channel 10.3 of the valve assembly 4, preventing the mixture from leaking.
In the preferred embodiment of the invention, the first shutter 6 is a prolongation of said sealing gasket 11, as seen for example in Figure 2, such that with the first shutter 6 in the resting position, it is supported on the frame 9.1 of the transition part 9, as seen in Figure 4A, blocking the main passage opening 5.1 of the mixing unit 2, as discussed.
In the preferred embodiment of the invention, the sealing gasket 11 is an annulus and the first shutter 6 extends from the periphery of said annulus towards the first passage area 5 through an attachment arm 6.1. Said attachment arm 6.1 is trapped between the transition part 9 and the valve assembly 4, more specifically by the main body 10, as seen in Figures 3 and 4A, becoming the pivoting shaft 12 of the first shutter 6, such that the first shutter 6 is configured for bending with respect to said attachment arm 6.1 when the mixture exerts a pressure higher than the first threshold pressure, moving it away from the resting position, as depicted in Figure 4B.
To make it easier to manufacture the first shutter 6, said shutter is made of the same material as the sealing gasket 11, giving rise to a flexible shutter 6.

Claims

Premix gas burner comprising a combustion area (1) and a mixing unit (2) communicated with the combustion area (1), with a mixture of an oxidizer and a fuel, preferably air and gas, being generated in the mixing unit (2), and the mixing unit (2) comprising a fan (2.1) driving the mixture towards the combustion area (1) according to a flow direction (A), the burner (100) further comprising between the mixing unit (2) and the combustion area (1) a first passage area (5) comprising a first shutter (6) which, in a resting position, prevents the passage of the mixture and is configured for being moved and allowing the passage of the mixture when the mixture exerts a pressure higher than a first threshold pressure on said shutter (6), and a second passage area (8) between the first passage area and the combustion area (1) comprising a second shutter (7), characterised in that the second shutter (7) comprises a resting position in which the passage of a minimum flow rate of the mixture through the second passage area (8) is allowed, with the second shutter (7) being configured for being moved and allowing the passage of a larger flow rate of the mixture when said mixture exerts a pressure higher than a second threshold pressure greater than the first threshold pressure.
Premix gas burner according to claim 1, wherein the second shutter (7) comprises a through hole (7.1), preferably having a circular section, which allows the passage of the minimum flow rate when said second shutter (7) is in the resting position.
Premix gas burner according to claim 1, wherein being the second shutter (7) in the resting position, between the second shutter (7) and the second passage area (8) there is such a clearance that the passage of the minimum flow rate is allowed.
Premix gas burner according to any of claims 1 to 3, wherein the first passage area (5) comprises a main passage opening (5.1) arranged in the mixing unit (2), such that in the resting position the first shutter (6) rests on a frame (9.1) surrounding the main passage opening (5.1) of the mixing unit (2).
Premix gas burner according to any of claims 1 to 4, comprising a main conduit (3) communicating the combustion area (1) and the mixing unit (2), the main conduit (3) comprising therein a valve assembly (4) comprising the first shutter (6) and the second shutter (7).
Premix gas burner according to claim 5, wherein the second passage area (8) comprises an additional passage opening (8.1) arranged in the valve assembly (4), such that in the resting position the second shutter (7) rests on at least part of a frame (10.1) of the valve assembly (4) surrounding the additional passage opening (8.1) and/or on a rib (10.2) going through said additional passage opening (8.1).
Premix gas burner according to claim 5 or 6, wherein the valve assembly (4) comprises a hollow main body (10), inside of which a passage channel (10.3) is formed running into the second passage area (8), such that the flow of the mixture exiting the first passage area (5) when said mixture exerts a pressure higher than the first threshold pressure on the first shutter (6) is directed towards the second passage area (8) through the passage channel (10.3).
Premix gas burner according to any of claims 5 to 7, wherein the second shutter (7) comprises an active area (7a) and a non-active area (7b), with the active area (7a) being configured for bending with respect to the non-active area (7b) when the mixture exerts a pressure on the active area (7a) higher than the second threshold pressure, the second shutter (7) comprising a protuberance (7.3) arranged in the non-active area (7b) which is housed in a housing (13) of the valve assembly (4) to retain the non-active area (7b) and allow the active area (7a) to bend.
Premix gas burner according to any of claims 5 to 8, wherein the burner (100) also comprises a sealing gasket (11) arranged between the mixing unit (2) and the valve assembly (4), the first shutter (6) being a prolongation of said sealing gasket (11).
Premix gas burner according to claim 9, wherein the sealing gasket (11) is an annulus, the first shutter (6) extending towards the first passage area (5) through an attachment arm (6.1), the first shutter (6) being configured for bending with respect to said attachment arm (6.1) when the mixture exerts a pressure higher than the first threshold pressure on said first shutter (6), moving it away from the resting position.
Premix gas burner according to claim 9 or 10, wherein the first shutter (6) is made of the same material as the sealing gasket (11).
Premix gas burner according to any of the preceding claims, wherein the second shutter (7) is heavier than the first shutter (6), preferably twice as heavy and very preferably three times as heavy.
Premix gas burner according to any of the preceding claims, wherein both the first shutter (6) and the second shutter (7) are flexible, at least the second shutter (7) preferably being made of silicone.
Premix gas burner according to any of the preceding claims, wherein the mixing unit (2) also comprises an inlet conduit for the oxidizer and an inlet conduit for the fuel, said inlet conduit for the fuel being associated with a valve that regulates the amount of fuel, the fan (2.1) causing the mixture of the oxidizer and the fuel inside the mixing unit (2) depending on the power of the fan (2.1), the fan (2.1) driving said mixture towards the combustion area according to the flow direction (A) through the first passage area (5) and the second passage area (8).
Gas boiler comprising a premix gas burner according to any of the preceding claims.