Heating device and use of a flame dividing device

Abstract

A heating device (10) is proposed for the combustion of a combustion mixture of a fuel gas and combustion air, which is supplied to a burner arrangement (1) via a conveying device (6) through a mixture channel (7), exits through a burner outlet element (4) into a combustion chamber (3) and is combusted. A flame-splitting device (5) is provided in the combustion chamber (3), arranged downstream of the burner outlet element (4) in a flow direction (15) of the heating device (10). The flame-splitting device (5) is designed and arranged such that the flow cross-section within the combustion chamber (3) is segmented and flow channels (20) are formed. The flame-splitting device (5) divides the flow cross-section in the combustion chamber (3) into two to eight flow channels (20).

Description

[0001] The invention relates to a heating device designed for the combustion of a fuel gas and the use of a device for flame splitting.

[0002] Heating appliances designed for the combustion of a fuel gas are known in large numbers from the prior art. During combustion, self-induced vibrations can occur in such heating appliances at certain operating points due to flame instabilities, which, in conjunction with the natural frequencies of the heating appliance, can lead to the occurrence of disturbing noises.

[0003] To avoid noise generation, for example in DE 10 2005 052 881 A1 or EP 3 173 698 A1, it is proposed to couple a Helmholtz resonator to a flow channel of the heating device. However, this solution is complex and cannot prevent the occurrence of high-frequency noise.

[0004] In addition, the use of special silencers or the insertion of additional flow resistances in a flow channel of the heating device is known. However, these solutions cannot prevent the occurrence of high frequencies, especially above 1 kilohertz.

[0005] EP 2 708 814 A1 describes a dark radiator with a flame flashback protection device which, unfortunately, cannot reduce noise generation.

[0006] US Patent 9,447,665 B2 discloses a burner with a reaction vessel designed to contain combustion within its interior in order to reduce emissions. This reaction vessel also fails to reduce noise.

[0007] It is therefore an object of the invention to at least partially alleviate or solve the problems described with reference to the prior art. In particular, a heating device is to be provided that prevents the occurrence of noise emissions across the entire audible frequency spectrum. Furthermore, it is desirable that the invention can be easily retrofitted to existing heating devices and, in particular, requires only minor structural modifications.

[0008] These problems are solved by the features of the independent claims. Further advantageous embodiments of the solution proposed here are specified in the independent claims. It should be noted that the features listed in the dependent claims can be combined with one another in any technologically meaningful way and define further embodiments of the invention. Furthermore, the features specified in the claims are further specified and explained in the description, which also presents further preferred embodiments of the invention.

[0009] This is achieved using a heating device designed to combust a mixture of fuel gas and combustion air. This mixture is fed to a burner arrangement via a conveying device through a mixture channel, and exits through a burner outlet element into a combustion chamber where it is combusted. Within the combustion chamber, a flame-splitting device is arranged downstream of the burner outlet element (viewed from the direction of flow through the heating device). This device is designed and positioned such that the flow cross-section within the combustion chamber is segmented, at least in one section. The flame-splitting device divides the flow cross-section in the combustion chamber into two to eight flow channels.

[0010] The heating unit can supply a building with heating and / or hot water and can be wall-mounted or freestanding. In particular, the heating unit can provide a heat output of up to 50 kilowatts.

[0011] The heating appliance can draw in a mass flow of combustion air via an air supply using a conveying device. A mass flow of fuel gas, corresponding to a predetermined combustion air ratio (also known as lambda or air-fuel ratio), is added to this mixture. The resulting combustion mixture can be fed to the burner assembly via a mixture channel and flow into a burner cavity. From there, it exits through the burner outlet element into the combustion chamber and is combusted. The heating appliance may include an ignition device to ignite the combustion mixture at the burner outlet element. The combustion products can then be discharged via an exhaust duct from the heating appliance into the building's exhaust system.

[0012] The burner assembly can comprise at least one burner cavity and a burner outlet element through which the combustion mixture can exit into a combustion chamber for combustion. The burner cavity can also have a burner hood, which often contains an inlet for the combustion mixture. In the case of a cylindrical burner, the burner hood frequently consists of a burner door that simultaneously delimits the combustion chamber. In the case of a flat burner or a burner with a flat burner outlet element, the burner hood can separate the burner cavity from the surrounding environment.

[0013] The heating appliance can have a gas valve to control the mass flow of fuel gas, which typically includes a gas safety valve and a gas control valve. The gas control valve can be, in particular, a stepper motor valve capable of setting a defined mass flow of fuel gas. Alternatively, the gas control valve can also deliver a mass flow of fuel gas according to a transmitted control pressure. The control pressure can be measured in a Venturi device and serve as a measure of the delivered mass flow of combustion air. This configuration is also known as a pneumatic gas-air system. The safety valve is designed to prevent the escape of unburned hydrogen and, for example, during the heating appliance's start-up process, is only released after the delivery system has been activated to a starting power level suitable for the start-up process. The aforementioned components can be any part of the heating appliance itself.

[0014] The heating appliance can adjust its burner output to the demand, a process also known as "modulation." Upon detecting a change in heat demand, for example, by considering the flow and return temperatures of a heating circuit connected to the appliance, a control unit can adjust the fan output and thus the combustion air flow rate to the heat demand. Simultaneously, a control system adjusts the fuel gas flow rate to the changing combustion air flow rate. To prevent flame flashbacks at low output levels, the combustion air ratio is often adjusted, particularly by increasing the proportion of combustion air. The resulting increase in flow velocity (at the same appliance output) and reduction in flame speed can mitigate the risk of flame flashbacks.Nevertheless, during a modulation process of the heating device there is an increased risk of flame flashback or combustion noise, which can be reduced by the measures proposed here.

[0015] Different flame zones form at different modulation points. In particular, the flame height can vary, and thus the distance of the flame tips from the burner outlet element, or in other words, the height of the flame zone, can vary.

[0016] The burner outlet element can have a cylindrical or, in particular, a flat shape. It comprises a multitude of openings through which the combustion mixture can flow. A burner outlet element is often also referred to as a perforated plate. During normal operation of the heating appliance, the combustion mixture passes through the burner outlet element and then burns in the combustion chamber above it. A flame zone is formed downstream of the burner outlet element, viewed in the direction of flow through the heating appliance.

[0017] The combustion chamber can include one or more heat exchangers that transfer the heat generated during combustion to a heat transfer fluid circulating in a heating circuit or to domestic hot water. The heating appliance can be, in particular, a condensing boiler, in which the exhaust gas is cooled to a temperature that allows the utilization of the condensation heat of the water vapor contained in the exhaust gas. For example, a primary heat exchanger can be located at least partially in or on a wall of the combustion chamber, thus enabling the transfer of heat from the exhaust gas flow as well as the heat radiation from the flame to a heat transfer fluid.

[0018] According to one embodiment, the heating appliance can be configured to burn a fuel gas containing at least 80 percent (pure) hydrogen. In particular, the heating appliance can be configured to burn a fuel gas containing at least 90 or 95 percent hydrogen, or even virtually pure hydrogen.

[0019] The flame-splitting device can be a three-dimensional structure that segments the flowable length (i.e., the extent of the combustion chamber in the direction of flow) at least in one (preferably predominant) section, the flow cross-section available for flame formation and exhaust gas flow. Segmented in this context means, in particular, that the flow cross-section of the combustion chamber is divided into segments (separate chambers), which are referred to here specifically as flow channels. The flow channels or segments can have any cross-section, for example, an n-sided flow cross-section. The flow direction of the flow channels corresponds to the flow direction of the heating device or the combustion chamber and can be oriented perpendicular to the burner outlet element. The flame-splitting device thus has an inlet side and an outlet side for the flames.The exhaust gas is drawn in, with the inlet side facing the burner outlet element. The outlet side can face the exhaust pipe. The flame splitting device segments the flame area, at least in one section, relative to its length in the flow direction. The flow channels are generally designed in the form of a straight cylinder, with the base area corresponding to the flow cross-section. Each flow channel can, in particular, have a flow direction that corresponds to a normal direction of the burner outlet element in the area of ​​the respective flow channel. It is also possible for the flow cross-section of the flow channels to increase with increasing distance from the burner outlet element. This can make it possible to adapt the flame splitting device to the shape of the surface of the burner outlet element.The inlet side can also be adapted to the shape of the surface of the burner outlet element, for example, by having a curvature. In particular, the inlet side of the burner outlet element can be shaped and arranged such that it is as close as possible to equidistant from the burner outlet element.

[0020] According to one embodiment, the flame-splitting device can have a length and be arranged in such a way that the flame area occurring in the entire modulation range of the heating device (or its length in relation to the flow direction) is covered.

[0021] According to one embodiment, the flame splitting device can, for example, have a distance to the burner outlet element of 50 millimeters [mm] to 100 mm and, in particular, of 60 mm to 80 mm.

[0022] According to one embodiment, the flame splitting device can have flow channels with any flow cross-section, for example a rectangular, circular, oval, n-sided or triangular flow cross-section.

[0023] According to one embodiment, the length of the flame-splitting device in the direction of flow can be in a range of 40 mm to 140 mm.

[0024] According to one embodiment, the flame-splitting device can divide the flow cross-section in the combustion chamber into two to eight flow channels, which have a rectangular, circular, oval, n-sided, or triangular flow cross-section. In particular, the flow cross-section of the combustion chamber can be divided into at least four flow channels. A maximum of eight flow channels are formed.

[0025] According to one embodiment, the distance between flow channels of the flame-splitting device and / or between the flame-splitting device and an (inner) wall of the combustion chamber may be a maximum of 50 mm, 60 mm and / or 70 mm.

[0026] According to one embodiment, the flame-splitting device can be thermally coupled to a heat exchanger in the combustion chamber. This can advantageously cool the flame-splitting device.

[0027] The flame dividing device can be fixed in the combustion chamber in any number of ways. For example, it can be wedged in place or simply inserted into the combustion chamber. The flame dividing device can, for instance, use the pipes of a heat exchanger within the combustion chamber for fixation. It can also be fixed in the combustion chamber using suitable fasteners. In particular, the flame dividing device can be welded in place.

[0028] The flame-splitting device can be made of any material that can withstand the conditions, particularly the temperatures, within the combustion chamber. This could, for example, be sheet steel. The device could be a sheet steel arrangement in which several sheets are stacked like shelves, thereby defining the flow channels, possibly together with the combustion chamber wall.

[0029] Another aspect proposes the use of a flame-splitting device arranged in the combustion chamber of a heating appliance, which segments the flow cross-section within the combustion chamber and thus forms flow channels aligned in the direction of flow through the heating appliance, to avoid combustion noise from the heating appliance.

[0030] The details, features, and designs discussed in connection with the heating appliance may also occur in a use proposed here, and vice versa. In this respect, the features relating to the heating appliance can also be used to characterize the use, and vice versa.

[0031] This invention describes a heating appliance and a flame-splitting device that at least partially solve the problems described with reference to the prior art. In particular, the heating appliance and its use contribute to the largely complete elimination of combustion noise in a particularly simple manner across the entire modulation range and frequency spectrum of the combustion noise. Furthermore, the invention can also increase operational reliability in conjunction with flame stability.

[0032] Furthermore, the invention is very well suited for retrofitting existing heating appliances and can often be achieved by simply inserting the flame splitting device into a combustion chamber of a heating appliance.

[0033] The invention and its technical context are explained in more detail below with reference to the accompanying figures. It should be noted that the invention is not intended to be limited by the exemplary embodiments shown. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the situations described in the figures and combine them with other components and findings from the present description. It should be emphasized that the figures, and especially the depicted dimensions, are only schematic. They show: Fig. 1 : a heating device suggested here, Fig. 2 : a combustion chamber of a heating appliance proposed here with a flame-splitting device, and Fig. 3 . another illustration of a combustion chamber of a heating appliance presented here.

[0034] Fig. 1 Figure 10 shows an exemplary and schematic representation of a heating device 10. This device can include a burner assembly 1, which is at least partially arranged in a combustion chamber 3. Combustion air can be drawn from the environment via an air supply 13 in a flow direction 15 by means of a conveying device 6, which is designed here as a blower. The conveying device 6 can have an electric motor as its drive, which can be connected to a speed control 9 that can regulate the speed of the conveying device 6 by means of a pulse-width modulated (PWM) signal. A gas valve 12 can add fuel gas (here hydrogen) from a fuel gas supply 11 to the intake air mass flow and includes a safety valve and a fuel gas control valve for controlling the mass flow of fuel gas to be added. The resulting combustion mixture of fuel gas and combustion air can flow to the burner assembly 1 via a mixture channel 7 and be ignited there by an ignition device.The heat generated during combustion can be transferred, for example, to a heat transfer medium in a heating circuit by means of a heat exchanger 19.

[0035] The burner assembly 1 comprises a burner hood 2, a burner cavity 21 into which the combustion mixture is supplied from the mixture channel 7 and exits via a burner outlet element 4 into the combustion chamber 3, where it is combusted, forming a flame zone 16. After combustion, the combustion products can be discharged to the outside via an exhaust gas channel 18 located in the heating unit 10 and an exhaust system 17 in the flow direction 15. A flame-splitting device 5 can be arranged in the flame zone 16, which is designed and shaped such that at least one section of the flame zone 16 is located within the flame-splitting device 5.

[0036] Furthermore, the heating device 10 can have a flame monitoring device 14, which can be designed, for example, as an electrode for measuring ionization current. Alternatively or additionally, another sensor, e.g., a thermal, optical, acoustic, or chemical sensor, can be provided to fulfill the function of flame monitoring 14. In particular, the use of a sensor for UV (ultraviolet) radiation emitted by the flame has proven suitable for flame monitoring 14 of a flame zone 16 of hydrogen combustion.

[0037] A control and regulating unit 8 can be configured to regulate the heating device 10. For this purpose, it can be electrically connected, for example, to the speed control 9, the conveying device 6, the gas valve 12, and the flame monitoring 14.

[0038] Fig. 2 Figure 1 shows in detail and schematically a burner arrangement 1, which is equipped with a largely flat burner outlet element 4. The combustion mixture can enter the burner cavity 21 in the flow direction 15 and, after passing through the burner outlet element 4, form a flame zone 16. The combustion chamber 3 can be bounded by the heat exchanger 19, to which the heat transfer fluid is supplied from a return line of a heating circuit and, after heating, discharged into a supply line of the heating circuit. The combustion products can be evacuated from the combustion chamber 3 via a discharge 22 in the flow direction 15 and fed into the exhaust gas channel 18.

[0039] The flame-splitting device 5 has an inlet side 23 facing the burner outlet element 4, at which the flow channels 20 begin, with respect to a flow direction 25 of the flow channels 20. The flow direction 25 of the flow channels 20 can be aligned as closely as possible with the flow direction 15 of the heating element 10. The inlet side 23 of the flame-splitting device 5 can be adapted to the curved surface of the burner outlet element 4 such that the inlet side 23 maintains a nearly uniform distance from the burner outlet element 4 at every point. Furthermore, the flame-splitting device comprises an outlet side 24, which is arranged opposite the inlet side 23.

[0040] Fig. 3Figure 1 shows an example of a combustion chamber 3 of a heating device 10 with a flame splitting device 5. This has six flow channels 20 with a rectangular flow cross-section. Reference symbol list

[0041] 1 Burner assembly 2 Burner hood 3 Combustion chamber 4 Burner outlet element 5 Flame splitting device 6 Conveyor device 7 Mixture channel 8 Control and regulating unit 9 Speed ​​control 10 Heater 11 Fuel gas supply 12 Gas valve 13 Air supply 14 Flame monitoring 15 Flow direction heater 16 Flame area 17 Exhaust system 18 Exhaust duct 19 Heat exchanger 20 Flow channel 21 Burner cavity 22 Combustion product discharge 23 Inlet side 24 Outlet side 25 Flow direction flow channel

Claims

1. Heating device (10), configured for the combustion of a combustion mixture of a fuel gas and combustion air, which is supplied by means of a conveying device (6) through a mixture channel (7) to a burner arrangement (1), exits through a burner outlet element (4) into a combustion chamber (3) and is burned, wherein a flame splitting device (5) is provided in the combustion chamber (3), arranged downstream of the burner outlet element (4) in a flow direction (15) of the heating device (10), which is designed and arranged such that the flow cross-section within the combustion chamber (3) is segmented and flow channels (20) are formed, and wherein the flame splitting device (5) divides the flow cross-section in the combustion chamber (3) into two to eight flow channels (20).

2. Heating device (10) according to one of the preceding claims, wherein the flame splitting device (5) is aligned perpendicular to the burner outlet element (4) and at least partially segments a developing flame area (16) at the burner outlet element (4).

3. Heating device (10) according to one of the preceding claims, wherein the flame splitting device (5) has a distance to the burner outlet element (4) in a range of 60 mm to 80 mm.

4. Heating device (10) according to one of the preceding claims, wherein the flame splitting device (5) is fixed in the combustion chamber (3) by means of clamping, insertion and / or welding and / or on tubes of a heat exchanger in the combustion chamber (3).

5. Heating device (10) according to one of the preceding claims, wherein the heating device (10) comprises a Venturi device and forms a pneumatic gas-air system.

6. Heating device (10) according to one of the preceding claims, wherein the heating device (10) is configured for the combustion of a fuel gas containing at least 80% hydrogen.

7. Use of a flame splitting device (5) arranged in the combustion chamber (3) of a heating appliance (10), which segments the flow cross-section within the combustion chamber (3) and thus forms flow channels (20) aligned in the flow direction (15) to avoid combustion noise of the heating appliance (10).

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