Burner body with variable gas outlet area
By adjusting the number and area of outlet openings on the burner body and combining the chamber and baffle design, the flashback risk and narrow power adjustment range problems of the hydrogen burner are solved, the stability and safety of the flame are achieved, the working range is expanded, and the efficiency of the burner is improved.
Patent Information
- Application Number
- CN202480012266.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-03-10
- Filing Date
- 2024-02-28
- Publication Date
- 2025-09-09
AI Technical Summary
Existing fully premixed gas burners have problems with high flashback risk and narrow operating power adjustment range when using hydrogen as fuel. In particular, the flashback risk is significant at low power, and it is difficult to achieve stable combustion within a wide range.
By setting movable elements on the burner body to adjust the number and area of outlet openings, the outflow speed of the air and fuel gas mixture is changed to ensure flame stability. The burner power can be flexibly adjusted through the design of the chamber and baffle to avoid the risks of backfire and flameout.
It achieves flame stability and safety at low and high power, expands the operating power adjustment range of the burner, reduces the risk of backfire and flameout, and improves the efficiency and safety of the burner.
Smart Images
Figure CN120615151A_ABST
Abstract
Description
[0001] illustrate A burner body for a gas burner is described below, which is suitable for a full premix gas burner.
[0002] Specifically, the burner body described below is suitable for use in a power-adjustable full premixed gas burner, wherein the fuel gas contains hydrogen or is mainly composed of hydrogen, such as a gaseous fuel with a hydrogen volume percentage greater than 90%.
[0003] In gas boilers, it is known to use hydrocarbons as fuel gas, such as hydrocarbons containing methane (CH4), propane (C3H8) or butane (C4H10).
[0004] It is common practice to premix the fuel gas with the combustion air to reduce pollutant emissions, particularly nitrogen oxides (NOx), and as is also known, to provide more air than the stoichiometric amount, i.e. to operate in excess air mode.
[0005] In this regard, the excess air ratio λ is defined as a pure number that defines the relationship between the actual air-fuel ratio of the mixture and the stoichiometric air-fuel ratio.
[0006] However, excess air leads to reduced burner efficiency: generally, a good compromise to minimize pollutant emissions without unduly compromising burner efficiency is to have a burner with an excess air coefficient λ of approximately 1.25 - 1.35.
[0007] However, using light hydrocarbons such as methane as fuel still presents a significant pollution problem, namely carbon dioxide emissions.
[0008] Using hydrogen as fuel gas appears to be a promising solution for reducing polluting emissions from gas boilers; however, hydrogen burns very differently from light hydrocarbons: in particular, hydrogen molecules have a much higher burning velocity than light hydrocarbon molecules (for example, the flame speed of hydrogen is approximately seven times faster than that of methane).
[0009] The high-altitude flow velocity of fuel gas with a high hydrogen content results in a greater risk of flashback compared to the combustion of fuel gas without hydrogen or with a low hydrogen content.
[0010] In particular, it has been noted that in hydrogen combustion, the risk of flashback is particularly pronounced when the air / gas mixture is ignited or when the burner is operated at reduced power. Under these conditions, the flame speed is reduced, causing it to anchor on the burner surface and overheat it to temperatures that promote flashback phenomena.
[0011] Another disadvantage found in premix burners fed by hydrogen is the lower adjustable range of operating power compared to burners using conventional hydrocarbons (e.g., modulation ratio values exceeding approximately 1:4 - 1:5 have not been found in premix burners fueled by hydrogen).
[0012] In premix burners, a burner of elongated shape, for example substantially and / or essentially cylindrical, is provided, which is inserted into a combustion chamber.
[0013] The air and fuel gas are first premixed in a ratio sufficient for complete combustion with low pollutant emissions, and the resulting mixture escapes through a plurality of holes or openings located in the outer surface of the burner body, thereby forming a flame.
[0014] The shape, size, and number of openings affect the velocity of the fuel gas and air mixture escaping from the burner body openings.
[0015] Therefore, in order to avoid or reduce the risk of flashback, it is important to always keep the outflow velocity of the mixture above the laminar velocity of combustion.
[0016] In summary, some solutions are proposed below to at least partially overcome the problems of the prior art.
[0017] Specifically, a solution is proposed to reduce the risk of flashback in premixed hydrogen combustion when the burner is ignited and when the burner is operated at low power.
[0018] Furthermore, solutions are described that allow safer management of burners for the combustion of air and hydrogen mixtures while also enabling a wider range of operating power modulation.
[0019] These and other objects are achieved by a burner body for a premix gas burner according to claim 1 .
[0020] Further objects are achieved by the additional features of the relevant dependent claims.
[0021] Some possible embodiments of a burner body for a premix gas burner will be described below with reference to the accompanying drawings, in which: - Figure 1 is a schematic diagram showing a burner body in a first operating mode; - Figure 2 Shown with Figure 1 the same burner body as in the embodiment but in a second operating mode; - Figure 3 is a schematic diagram illustrating a second embodiment of a burner body in a first operating mode; - Figure 4 Shown with Figure 3 the same burner body as in the embodiment but in a second operating mode; - Figure 5 is a schematic diagram showing a third embodiment of a burner body in a first operating mode; - Figure 6 Shown with Figure 5 the same burner body as in the embodiment but in a second operating mode; - Figure 7 is a schematic diagram showing a burner device including a burner body according to the present invention.
[0022] The following describes some variant features of the invention using the reference numerals included in the drawings. It should be noted that the above drawings, although schematic, reproduce the components of the invention according to proportional relationships between spatial dimensions and orientations that are compatible with possible practical implementations.
[0023] It should also be noted that any size and spatial terms (such as "lower", "upper", "inner", "outer", "front", "rear", etc.) refer to the position of components shown in the drawings and do not impose any limitations on possible operating positions.
[0024] Special reference Figure 7 , reference numeral 1 denotes a burner body for a power-adjustable full premixed gas burner.
[0025] The burner body 1 is intended to be part of a burner assembly 10 (hereinafter referred to as "burner 10") and comprises at least: - a fan 11 for the air flowing in through a supply line 18, - a fuel gas supply line 12 consisting essentially and / or predominantly of hydrogen, - a valve 13 for regulating the fuel gas flow rate, - an air and fuel gas mixing unit 14, - A combustion chamber 19 into which the burner body 1 projects.
[0026] Depending on the required heating power, the fan 11 may be a variable speed (intermittent or continuous speed change within a given speed range) centrifugal fan.
[0027] The burner 10 thus allows discrete (stepped) or continuous regulation of the thermal power within a predetermined power range.
[0028] In the example shown, the air and fuel gas mixing unit 14 is positioned upstream of the fan 11 ; in an alternative embodiment (not shown), the mixing unit 14 may be positioned downstream of the fan 11 .
[0029] The burner 10 is further provided with conventional ignition means 15, such as an ignition electrode, and conventional sensing means 16 for detecting at least one combustion parameter, such as a temperature sensor or a sensor for detecting the presence of a flame.
[0030] An electronic regulator 17 is also provided for adjusting, for example, the fuel gas flow rate and the air flow rate.
[0031] The burner body 1 , which may be substantially and / or essentially cylindrical in outer shape, comprises an inlet opening 2 for the inflow of an air and fuel gas mixture.
[0032] As from Figures 1 to 6 and Figure 7 As can be seen more clearly in the figure, the burner body 1 comprises a plurality of outlets for the outflow of the air and fuel gas mixture arriving through the inlet opening 2. n outlet openings 31.a, 31.b; 32.a, 32.b; 33.a, 33.b, 33.c.
[0033] The shape, size and arrangement of the outlet openings 31.a, 31.b; 32.a, 32.b; 33.a, 33.b, 33.c on the surface of the burner body 1 can be changed as required.
[0034] The burner body 1 comprises at least one movable element 41 ; 42 ; 43 for varying the number of outlet openings 31 . a , 31 . b ; 32 . a , 32 . b ; 33 . a , 33 . b , 33 . c communicating with the inlet opening 2 .
[0035] By means of at least one movable element 41; 42; 43, the number of outlet openings 31.a, 31.b; 32.a, 32.b; 33.a, 33.b, 33.c and thus the outlet area of the burner body 1 from which the fuel gas and air mixture flows out can be varied.
[0036] As better described below, the partialisation of the number of outlet openings 31.a, 31.b; 32.a, 32.b; 33.a, 33.b, 33.c of the burner body 1 makes it possible to adjust the flame length emerging from the burner body and therefore to maintain the stability of the flame even in the case of significant variations in the operating thermal power.
[0037] In other words, by changing the flame outlet area (by changing the number of outlet openings 31.a, 31.b; 32.a, 32.b; 33.a, 33.b, 33.c), the stability of the flame can be improved so that the outflow velocity of the air / gas mixture always remains higher than the propagation velocity of the flame, and the outlet area is reduced when the burner 10 is modulated at a lower power, and the outlet area is increased when the burner 10 is operated at a higher power.
[0038] The described technical solution thus enables operation at reduced power (avoiding the risk of flashback) and at high power (avoiding the risk of flameout).
[0039] As a non-limiting example, by using pure hydrogen as the fuel gas, a power modulation ratio of approximately 1:10 can be achieved.
[0040] It should also be noted that by enabling regulation of the flame height coming out of the burner, operation with a constant lambda is possible even at low powers.
[0041] In other words, the described technical solution ensures high efficiency both at low and high operating powers.
[0042] Furthermore, the described technical solution enables the burner 1 to be used with fuels of different properties while maintaining flame stability.
[0043] In some embodiments, for example Figures 1 to 6 In the example shown in the accompanying drawings, the burner body 1 may include a plurality of n chambers 51.a, 51.b; 62.a, 62.b; 73.a, 73.b, 73.c, for example, two chambers (such as Figures 1 to 4 ) or three chambers (such as the embodiment shown in the drawings Figure 5 and Figure 6 ).
[0044] The chambers 51.a, 51.b; 62.a, 62.b; 73.a, 73.b, 73.c are delimited by fixed partition walls inside the burner body 1 and parts of the outer wall of the burner body 1.
[0045] The burner body 1 includes a plurality of n In an embodiment of the chambers 51.a, 51.b; 62.a, 62.b; 73.a, 73.b, 73.c, each of them is connected to the inlet opening 2, and each chamber 51.a, 51.b; 62.a, 62.b; 73.a, 73.b, 73.c is connected to the n Parts of the outlet openings 31.a, 31.b; 32.a, 32.b; 33.a, 33.b, 33.c are connected.
[0046] For example, in the version of the burner body 1 with two chambers 51.a, 51.b; 62.a, 62.b (see Figures 1 to 4 ), it is possible to provide two chambers 51.a, 51.b; 62.a, 62.b each of which is substantially connected to half of the total flame outlet area, which area is defined by the openings 31.a, 31.b; 32.a, 32.b provided on the surface of the burner body 1.
[0047] Thus, in this embodiment, each of the two chambers 51 . a , 51 . b ; 62 . a , 62 . b is capable of outputting approximately half of the maximum thermal power that the burner 10 is capable of outputting.
[0048] In the version of the burner body 1 with three chambers 73.a, 73.b, 73.c (see Figure 5 and Figure 6 ), each chamber is essentially in communication with approximately one third of the total flame outlet area defined by the outlet openings 33.a, 33.b, 33.c.
[0049] Thus, in this embodiment, each of the three chambers 73 . a , 73 . b ; 73 . c is capable of outputting approximately one third of the maximum thermal power that the burner 10 is capable of outputting.
[0050] In particular, Figure 5 and Figure 6 The burner body 1 can work with one chamber 73.a, two chambers 73.a, 73.b or all three chambers 73.a, 73.b, 73.c.
[0051] In the embodiment of the burner body 1 of the accompanying drawings, the chambers 51.a, 51.b; 62.a, 62.b; 73.a, 73.b, 73.c are shown to be connected to the outlet openings 31.a, 31.b; 32.a, 32.b; 33.a, 33.b, 33.c, which define a total flame outlet area with a substantially similar dimensional development in each of the chambers.
[0052] However, embodiments of the burner body 1 may also be provided in which the total flame outlet area has a dimensional development that is not similar in each chamber 51.a, 51.b; 62.a, 62.b; 73.a, 73.b, 73.c, thereby enabling output of unequal proportions of the thermal power that the burner 10 is capable of outputting.
[0053] According to the present invention, then set n-1movable elements 41; 42; 43, which are positioned n-1 62.b; 73.b, 73.c upstream and downstream of the inlet opening 2 to open and close the inlet opening 2 and the n-1 The communication between the chambers 51.b; 62.b; 73.b, 73.c.
[0054] In some of the embodiments shown, n-1 The movable elements 41; 42; 43 are baffles adapted to open and close the corresponding passage openings, which separate the inlet opening 2 from the n-1 The chambers 51.b; 62.b; 73.b and 73.c are connected.
[0055] Therefore, in an embodiment of the burner body 1 in which multiple chambers are provided, one of the chambers 51.a; 62.a; 73.a is always passed through by the air flow of the air and fuel gas mixture, thereby ensuring that the burner 10 obtains the minimum power required for its proper operation, while the other chambers 51.b; 62.b; 73.b, 73.c are only passed through by the air and fuel gas mixture when their corresponding baffles 41; 42; 43 are opened.
[0056] Reference Figure 5 and Figure 6 In the embodiment, at the ignition moment of the burner 10 or when the burner 10 operates at a power of approximately less than one-third of the maximum power, only the chamber 73.a is open, while the other two chambers 73.b and 73.c remain closed.
[0057] When the burner 10 is operating at a power level between approximately one third and two thirds of the maximum power, one damper 43 is open and the other is closed, so that only two of the three chambers 73.a, 73.b are in operation.
[0058] When the burner 10 is operating at a power level between approximately two-thirds and three-thirds of maximum power, both dampers 43 are open, so that all three chambers 73.a, 73.b, 73.c are in operation.
[0059] The movable element 41 ; 42 ; 43 (hereinafter referred to as “the baffle 41 ; 42 ; 43 ”) may be axially movable or capable of swinging (for example, by 90°).
[0060] These shutters 41 ; 42 ; 43 arranged upstream of the chambers 51 . b ; 62 . b ; 73 . b , 73 . c may be, for example, eccentrically hinged tilting plate-shaped shutters.
[0061] In some specific embodiments, the baffles 41; 42; 43 can be electric baffles (see Figure 5 、 6 and the variant shown in 7 ): For this purpose, a drive mechanism 430 may be provided to operate the flaps 41 ; 42 ; 43 , for example an electric motor with 90° rotation.
[0062] The motorized shutter 41; 42; 43 can be switched from a configuration completely closing the passage opening to a configuration completely opening the passage opening.
[0063] The switching of the motorized damper 41 ; 42 ; 43 between the two operating position configurations can be performed, for example, as a function of the number of revolutions of the fan 11 .
[0064] Naturally, other operating parameters may also be used to adjust the motorized dampers 41 ; 42 ; 43 .
[0065] For example, in alternative embodiments of the burner 10, the operating position of the motorized dampers 41; 42; 43 may be adjusted based on the mass flow rate of the air / fuel gas mixture, the mass flow rate of air, or the mass flow rate of the fuel gas.
[0066] Therefore, the speed of the air and fuel gas mixture flowing out through the outlet openings 31.a, 31.b; 32.a, 32.b; 33.a, 33.b, 33.c can be adjusted by the operating position of the electric dampers 41; 42; 43 to maintain the flame height within a range where the flame remains stable and avoids the risk of backfire or flameout.
[0067] Furthermore, in other forms of use of the burner body 1 , at the moment of ignition of the burner 10 , provision can be made for the motorized dampers 41 ; 42 ; 43 to remain closed, thereby operating with a smaller number of outlet openings 31 . a ; 32 . a ; 33 . a and reducing the risk of flashback.
[0068] Preferably, a hysteresis function is provided for the operation of the dampers 41 ; 42 ; 43 in order to avoid excessive oscillations of the burner regulating system 10 .
[0069] In other embodiments, the flaps 41 ; 42 ; 43 are not provided with a drive mechanism 430 and are configured to mechanically open in a self-adapting manner when the pressure upstream of the flap is significantly greater than the pressure downstream thereof.
[0070] On the contrary, when the pressure difference is less than a preset value, the adaptive baffles 41 ; 42 ; 43 are mechanically closed.
[0071] According to these embodiments, the opening of the flaps 41 ; 42 ; 43 occurs against a recall force towards the closed position, such as the weight of the flaps and / or the force of elastic means, such as a spring operating in compression.
[0072] 43 is thus in an angular position corresponding to a point of equilibrium between the torque generated by the thrust of the air and gas mixture and the drag torque generated by, for example, the weight of the baffle and / or by elastic means.
[0073] Figures 1 to 6 The embodiment of the burner body 1 shown in the accompanying drawings has proven suitable for solving the technical problem of adjusting the outflow speed of the air / gas mixture from the outlet openings 31.a, 31.b; 32.a, 32.b; 33.a, 33.b, 33.c according to the operating power of the burner 1, thereby avoiding flashback when the burner 10 is operated at a lower power.
Claims
1. A burner body (1) for a fully premixed power-adjustable gas burner (10), comprising: - an inlet opening (2) for the inflow of the air and fuel gas mixture, - a plurality of on the surface of the burner body (1) n outlet openings (31.a, 31.b; 32.a, 32.b; 33.a, 33.b, 33.c), for allowing the air and fuel gas mixture to flow out, It is characterized by: It includes: - at least one movable element (41; 42; 43) for varying the number of said outlet openings (31.a, 31.b; 32.a, 32.b; 33.a, 33.c) communicating with said inlet opening (2), - a plurality of fixed partitions inside the burner body (1) and parts of its outer wall n chambers (51.a, 51.b; 62.a, 62.b; 73.a, 73.b, 73.c), Each of the chambers (51.a, 51.b; 62.a, 62.b; 73.a, 73.b, 73.c): - communicates with said inlet opening (2), - with the plural n A portion of each of the outlet openings (31.a, 31.b; 32.a, 32.b; 33.a, 33.b, 33.c) is connected, - Positioning n-1 upstream of the chambers (51.b; 62.b; 73.b, 73.c) and downstream of the inlet opening (2) n-1 a movable element (41; 42; 43) for opening and closing the inlet opening (2) and the plurality of n The communication between the outlet openings (31.a, 31.b; 32.a, 32.b; 33.a, 33.b, 33.c).
2. The burner body (1) according to claim 1, characterized in that: described n-1 The first movable element (41; 42; 43) is an electric baffle, which is actuated by a drive mechanism (430).
3. The burner body (1) according to claim 2, characterized in that: The electric damper (41; 42; 43) is suitable for completely closing the inlet opening (2) and the plurality of n a configuration in which the plurality of outlet openings (31.a, 31.b; 32.a, 32.b; 33.a, 33.b, 33.c) are connected to each other, and a configuration in which the communication is fully opened is switched to a configuration in which the communication is fully opened. The configuration is adjusted according to the fan (11) speed and / or the flow rate of the air / fuel gas mixture flowing into the burner body (1) through the inlet opening (2).
4. The burner body (1) according to claim 1, characterized in that: described n-1 The movable element (41; 42; 43) is a damper adapted to be mechanically opened and closed in an adaptive manner and which, against a return force towards the closed position, assumes an angular position determined according to the speed of the fan (11) and / or the flow rate of the air / fuel gas mixture flowing into the burner body (1) through the inlet opening (2).
5. The burner body (1) according to any one of claims 1 to 4, characterized in that: With the plural n The chambers (51.a, 51.b; 62.a, 62.b; 73.a, 73.b, 73.c) connected to the outlet openings (31.a, 31.b; 32.a, 32.b; 33.a, 33.b, 33.c) are in each of the chambers (51.a, 51.b; 62.a, 62.b; 73.a, 73.b, 73.c) define a total flame outlet area of similar size.
6. The burner body (1) according to any one of claims 1 to 4, characterized in that: With the plural n The chambers (51.a, 51.b; 62.a, 62.b; 73.a, 73.b, 73.c) connected to the outlet openings (31.a, 31.b; 32.a, 32.b; 33.a, 33.b, 33.c) are in each of the chambers (51.a, 51.b; 62.a, 62.b; 73.a, 73.b, 73.c) define total flame outlet areas of dissimilar sizes.
7. Full premixed adjustable power gas burner (10), comprising a burner body (1) according to any one of claims 1 to 6, comprising at least: - a fan (11) for the air flowing in through the supply line (18), - a fuel gas supply line (12), said fuel gas being mainly and / or substantially hydrogen, - a valve (13) and a corresponding electronic regulator (17) for regulating the flow rate of the fuel gas, - a mixing unit (14) for said air and fuel gas, - a combustion chamber (19) into which the burner body (1) extends - an ignition device (15) of the burner (10).