Method for operating a heating device, computer program and heating device

Abstract

A heating device (1) with a pneumatic gas-air system is proposed, comprising a split gas supply with at least one main channel (14) and an auxiliary channel (17), as well as a method for its operation, wherein the auxiliary channel (17) is closed during an ignition process of the heating device (1). This allows for an increase in the air-fuel ratio of the combustion mixture and thus increased safety during an ignition process.Additionally, within the framework of the proposed procedure, the closing and / or opening of the auxiliary channel (17) can be detected / verified by recording and evaluating at least one parameter from the following group during an opening and / or closing process of the auxiliary channel (17): a rotational speed n or a control signal of a conveying device of the heating appliance; a signal that allows a conclusion to be drawn about a flow rate of combustion air; a flame signal at a burner (3) of the heating appliance (1); a flow temperature and a return temperature of a heating circuit (18) connected to the heating appliance (1).

Description

[0001] The invention relates to a method for starting a heating device, a computer program and a heating device.

[0002] During the operation of a gas burner, the starting process in particular can trigger critical conditions. Examples of such critical conditions include a hard ignition, a deflagration, or a flame flashback. This can involve flame propagation from the burner into the fuel gas / combustion air supply during the start-up or ignition process, which can lead to damage to the heating appliance. When using hydrogen as the fuel gas, such critical conditions are even more likely due to hydrogen's significantly higher flame speed.

[0003] In heating appliances with a pneumatic mixture composition, a fuel gas mass flow rate is added according to a negative pressure generated by the volume flow of the intake combustion air in a throttling point, usually a Venturi nozzle. This provides a mixture of fuel gas and combustion air with a (fixed or predetermined) air-fuel ratio, also known as the combustion air ratio or lambda. The mixture is therefore preset before being supplied to the burner. Particularly during the start-up process, deviations in the quality of the fuel gas or other circumstances can lead to critical conditions.

[0004] To avoid such critical conditions, EP 3 992 529 A1 proposes using a pilot flame with its own fuel supply to ignite a main burner, the function of which can be monitored by a sensor and which is also arranged in such a way that the pilot flame cannot be extinguished by air escaping from the main burner. However, such a design is associated with considerable effort.

[0005] To enable more reliable ignition of a heating appliance, DE 10 2019 121 973 A1 proposes arranging a catalyst material within the heating appliance, specifically within the gas-air mixture flow. Due to its properties, the catalyst material can provide the necessary activation energy to initiate combustion without additional thermal energy, such as a spark or pilot flame. This solution, however, is also associated with considerable effort and expense.

[0006] DE 199 06 583 A1 discloses a method and a device for operating an atmospheric gas burner, in which several gas nozzles are divided into at least two groups for a main gas flow and a secondary gas flow. During burner start-up, the secondary gas flow can be released with a time delay relative to the main gas flow, thereby optimizing the burner start-up. However, this concept is not applicable to a premixing burner.

[0007] A similar method for regulating the primary air ratio of an atmospheric burner is described in DE 196 29 966 A1. This method also proposes two fluidically separated chambers, each with a gas outlet opening that leads into a mixing chamber of the burner. This method is also not applicable to a premixing burner.

[0008] DE 102 20 774 A1 describes a heating appliance with a device for controlling a burner with a pneumatic gas-air mixture, in which an additional control valve is located downstream of the fuel control valve. The device allows for precise control of the air-fuel ratio. However, the aforementioned problems during a burner start-up process cannot be resolved by the device, or can only be resolved to a negligible extent.

[0009] Based on this, the object of the invention is to propose a method for starting or operating a heating device, a computer program, and a heating device that at least partially overcome the problems of the prior art described above. In particular, the invention is intended to enable the reliable ignition of a heating device, especially a hydrogen-powered heating device with a pneumatic gas-air system.

[0010] Furthermore, the process should be suitable for at least partial automation and require as few structural changes as possible compared to a state-of-the-art heating device.

[0011] 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 technical teaching. Furthermore, the features specified in the claims are further specified and explained in the description, which also presents further preferred embodiments of the invention.

[0012] This is achieved by a method for starting or (subsequently) operating a heating appliance with a pneumatic gas-air system, wherein the heating appliance has at least one conveying device that supplies a mixture of combustion air and fuel to a burner, and a (at least) two-part gas supply with a main channel and an additional channel, wherein the additional channel is closed for an ignition process of the heating appliance.

[0013] The method serves to ensure the reliable starting of a heating appliance, in particular with a pneumatically supplied combustion mixture and a fuel gas containing hydrogen, where the hydrogen content can be above 80% or, in particular, 90%.

[0014] The heating appliance can include at least one heat generator, in particular a gas condensing boiler, which releases thermal energy by burning a fuel and can transfer it to a heating circuit via at least one heat exchanger. Consumers in the heating circuit can be connected to the heating appliance via a heating flow and a heating return. The exhaust gases produced during combustion can be routed to an exhaust system via an exhaust duct in the heating appliance. A circulation pump can be installed in the heating circuit within the heating appliance to circulate a heat transfer medium (heating water). Heated heat transfer medium is supplied to consumers, such as convectors or underfloor heating systems, via a heating flow and returned to the heat generator or the at least one heat exchanger via a heating return.

[0015] For this purpose, the heating appliance has a conveying device, in particular a blower, which can supply a mixture of combustion air and fuel (especially hydrogen or a hydrogen-containing fuel gas) to a burner of the heating appliance. The heating appliance forms a pneumatic gas-air system in which a fuel gas mass flow supplied via a gas supply is added to a combustion air mass flow, in particular according to a negative pressure (control pressure) of a throttling point, such as a Venturi nozzle, so that a predefined (predetermined) combustion air ratio (air ratio, lambda) can be established. This predefined combustion air ratio can, for example, be set by a qualified technician during the installation of the heating appliance via an adjustment option on the gas control valve.

[0016] The heating appliance has a (at least two-)divided gas supply system, comprising a main channel and (at least) one auxiliary channel. In other words, the gas supply system of the heating appliance can include at least a divided section, whereby fuel gas can flow through both the main channel and the auxiliary channel (provided both are open). The main channel and auxiliary channel can thus be understood as parallel and / or separate channels of the gas supply system. It is possible that the gas supply system includes a branch for the auxiliary channel and a subsequent merger into a (common) flow path, specifically in the form of a (local) bypass. For the sake of completeness, it should be noted that a division of the gas supply into more than two (parallel) channels is also conceivable. The channels can be implemented using separate pipe sections. The channels in the divided or separate section can be designed without a common wall.

[0017] Furthermore, the heating device may feature flame monitoring. This often involves the use of an ionization electrode, which utilizes the flame's ionization current to detect it. However, this principle is not reliably applicable to a hydrogen flame because significantly fewer free charge carriers are produced during hydrogen combustion. Therefore, hydrogen-powered heating devices often employ other methods, such as detecting the electromagnetic radiation emitted by the flame, particularly IR (infrared) and / or UV (ultraviolet) radiation, or measuring the flame temperature.

[0018] According to the invention, the auxiliary channel is designed to be closable, so that during the start-up process of the heating appliance, the air-fuel ratio (i.e., a lower proportion of fuel gas in the combustion mixture) can be increased compared to the air-fuel ratio specified for normal heating operation by closing the auxiliary channel. Closing the auxiliary channel reduces the flow cross-section available for the gas flow in the gas supply and, consequently, the mass flow rate of fuel gas flowing through the gas supply. Advantageously, this allows critical conditions of the heating appliance during the start-up process to be largely avoided, particularly in a heating appliance with a pneumatic gas-air system, by temporarily increasing the air-fuel ratio.

[0019] According to one embodiment, the additional channel can be closed by means of a valve.

[0020] According to one embodiment, the valve can be opened and closed electrically and by means of a coil drive or a stepper motor.

[0021] According to one embodiment, the ratio of the flow cross-section of the main channel to the flow cross-section of the additional channel can be in a range of 1 to 3, in particular between 1.5 and 2.5.

[0022] According to one embodiment, during the start-up process of the heating appliance, the auxiliary channel can be opened if the appliance's flame sensor detects a flame. Flame detection can signal successful ignition and thus the end of the start-up or ignition process. Opening the auxiliary channel makes the entire intended flow cross-section of the gas supply available, and the mass flow of the supplied fuel gas can increase, allowing the heating appliance's burner to be supplied with a combustion mixture with a predefined (normal) air-fuel ratio, corresponding to normal heating operation.

[0023] According to one embodiment, the closing and / or opening of the auxiliary channel can be detected / verified by capturing and evaluating at least one parameter from the following group during an opening and / or closing process of the auxiliary channel: A speed or control signal from a pumping device of the heating appliance, a signal that allows conclusions to be drawn about the combustion air flow rate, a flame signal from a burner of the heating appliance, a flow temperature and a return temperature of a heating circuit connected to the heating appliance. In other words, by detecting or evaluating one of the listed parameters, an opening and / or closing process of the auxiliary channel can be determined, and thus proper functioning can be verified.

[0024] A blockage of the device for closing and opening the auxiliary channel could lead to the aforementioned critical states during a startup process. Therefore, a way to check the functionality of the device for closing and opening the auxiliary channel is desirable. This can be achieved by capturing and evaluating at least one parameter from the aforementioned group. The following section explains how to detect a blocked auxiliary channel using the parameters mentioned.

[0025] The opening or closing of the auxiliary channel can be detected by monitoring the rotational speed or a control signal from the heating unit's conveying system. This control signal can be a pulse-width modulated (PWM) signal, which regulates the conveying system (often a fan). Opening of the auxiliary channel can be detected by an increase in the speed of the fan, as the additional hydrogen flowing through the auxiliary channel reduces the mixture density, thus requiring less power from the conveying system. If the speed is controlled at a constant value, a corresponding decrease in the PWM signal would be observed. If the mechanism for opening and / or closing the auxiliary channel is blocked, no change in the conveying system's speed or the PWM signal would be detectable.A closing process of the auxiliary channel can be detected by a reverse response in the speed or PWM signal. Advantageously, the opening / closing of the auxiliary channel can be detected based on the speed of the conveying unit or a control signal with the burner switched off or on. Both the fault condition "auxiliary channel does not open" and the fault condition "auxiliary channel was not closed" can be identified by capturing and evaluating the speed or control signal of the conveying unit. This allows for a check of the opening and closing function of the auxiliary channel before commissioning the heating unit or even during heating operation.

[0026] The signal that allows conclusions to be drawn about the combustion air flow rate can be provided, in particular, by a flow sensor (air mass flow sensor) or differential pressure sensor located in the combustion air supply. The opening of the auxiliary channel could be detected if the air mass flow decreases during the opening process. This could be explained by the constant delivery rate of the supply unit in conjunction with the additional volume of fuel gas supplied from the auxiliary channel. This method can also be advantageously implemented with the burner switched on or off and is suitable for detecting an opening or closing process.

[0027] A flame signal at a burner of the heating appliance could, for example, be a temperature signal from a flame temperature sensor, a signal from flame monitoring via ionization current measurement, or a signal from an optical sensor, such as a UV (ultraviolet) radiation sensor. Opening the auxiliary channel would result in an increase in the heating appliance's power output and a corresponding change in the flame signal, such as an increase in flame temperature, ionization current, or UV radiation from the flame. This parameter is also suitable for detecting the opening and closing of the auxiliary channel.

[0028] The flow and return temperatures of a heating circuit connected to the boiler can (assuming a constant mass flow rate in the heating circuit) serve as a measure of the burner's output. Therefore, the opening / closing of the auxiliary channel and the associated change in burner output can be detected based on the temperature difference between the flow and return temperatures. This parameter is also suitable for detecting the opening and closing of the auxiliary channel.

[0029] According to a further embodiment, information about a detected error when opening or closing the auxiliary channel can be displayed via a display device and / or made available for retrieval via a network, particularly the internet, and / or sent as a message. For example, the information can be made available for retrieval on an appliance interface of the heating device or on network storage (cloud). This allows, for example, a user / operator of the heating device and / or a service company to be informed about an error when opening and / or closing the auxiliary channel via a message, enabling the service company to schedule and carry out a maintenance and / or repair appointment accordingly.

[0030] In addition, a computer program is proposed that is designed to (at least partially) execute one of the procedures presented here. In other words, this specifically concerns a computer program (product) comprising commands that, when executed by a computer, cause it to perform the procedure proposed here. The computer program can, in particular, close the auxiliary channel before the heater starts or ignites, open the auxiliary channel upon detecting a burner flame, and / or check the function or detect a fault when opening and closing the auxiliary channel. This program can be executed on a control unit of the heater.

[0031] Another aspect that is proposed is a machine-readable storage medium on which the computer program is stored. This machine-readable storage medium is typically a computer-readable data carrier.

[0032] A control unit for a heating appliance with a pneumatic gas-air system may be provided, configured to carry out a procedure proposed herein. For this purpose, the control unit may, for example, include and / or have a processor. In this context, the processor may, for example, execute the procedure stored in a memory (of the control unit). The control unit may, in particular, be electrically connected to an auxiliary valve, a flame monitor, a temperature sensor for the flow and return temperatures of a heating circuit connected to the heating appliance, a conveying device or its control system, and / or a flow sensor or a differential pressure sensor in the air supply.

[0033] Another aspect proposed is a heating appliance with a pneumatic gas-air system, comprising a control and regulating device as suggested herein. The heating appliance can be a gas-fired appliance, in particular a hydrogen-powered gas-fired appliance. The gas-fired appliance can include a burner and a delivery system for supplying a mixture of combustion gas (hydrogen) and combustion air to the burner. The heating appliance can, in particular, regulate the mixture composition of combustion gas and combustion air (combustion air ratio) by incorporating a signal from a flame temperature sensor. Furthermore, the heating appliance can include a split gas supply with at least one main channel and one auxiliary channel, the auxiliary channel of which can contain an additional valve designed to open and close it.

[0034] The details, features, and advantageous configurations discussed in connection with the process can also occur in the computer program, control unit, and heating device presented here, and vice versa. In this respect, full reference is made to the explanations provided therein for a more detailed characterization of the features.

[0035] This document presents a method for starting and operating a heating device, a computer program, and a heating device that at least partially solve the problems described with reference to the prior art. In particular, the method for starting and operating the heating device, the computer program, and the heating device contribute to enabling reliable ignition of a heating device, especially a hydrogen-powered one. Furthermore, the method proposed here is advantageously fully computer-implemented and therefore requires no structural modifications to the heating device.

[0036] 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, and Fig. 2 to 4 : Parameter profiles that may occur when carrying out a procedure proposed here.

[0037] Fig. 1Figure 1 shows an exemplary and schematic representation of a heating device 1 proposed here. This device can include a burner 3 arranged in a combustion chamber 8. Combustion air can be drawn in via a combustion air supply 4, in which an air mass flow sensor 12 may be arranged, by a conveying device 2, in particular designed as a blower. The conveying device 2 can be connected to a control unit 22, which can regulate the speed n of the conveying device by means of a pulse-width modulated (PWM) signal. A safety valve 5 can supply fuel gas to a gas control valve 24, whereby the gas control valve 24 can add fuel gas to the drawn-in air mass flow according to a control pressure of a throttling point in the combustion air supply 4, often designed as a Venturi nozzle. The generated mixture of fuel gas and combustion air can flow to the burner 3 via a mixture channel 22.

[0038] The heating appliance 1 proposed here can be configured, in particular, for the combustion of hydrogen. A heat exchanger 23 arranged in the exhaust gas path of the burner 3 can transfer heat generated during combustion in the combustion chamber 8 to a heat transfer medium circulating in a heating circuit 18. A heating circuit supply temperature sensor 6, a heating circuit return temperature sensor 11, and a flow sensor 9 can be arranged on the heating circuit 18. Combustion products generated during combustion can be fed to an exhaust system 20 via an exhaust pipe 10 of the heating appliance 1. A flame temperature sensor 16 and a flame monitoring sensor 15 can be provided on the burner 3. The flame monitoring sensor 15 can, in particular, be a sensor for UV and / or IR radiation or an ionization electrode.

[0039] In the gas supply 8, the gas supply can be branched in a divided section into a main channel 14 and an auxiliary channel 17. An auxiliary valve 13 can be arranged in the auxiliary channel, configured to open or close the auxiliary channel 13. The auxiliary valve 13 can include a motor drive, and the opening or closing of the auxiliary valve 13 can be electrically controlled.

[0040] A control and regulating unit 7 can be configured to control the heating appliance 1. For this purpose, it can be electrically connected, for example, to the control unit 22 of the conveying device 2, the safety valve 5, the heating circuit supply temperature sensor 6, the heating circuit return temperature sensor 11, the flow sensor 9 in the heating circuit 18, the air mass flow sensor 12 in the air supply 4, the flame temperature sensor 16, the flame monitoring sensor 15, and the auxiliary valve 13.

[0041] Fig. 2shows a diagram in which the abscissa axis represents the time t and the ordinate axis represents the rotational speed n of the conveying device 2.

[0042] When carrying out the procedure proposed here, the auxiliary valve and thus the auxiliary channel 17 can be closed to start up the heating appliance 1 or to ignite the burner 3. The resulting reduction in the flow cross-section of the gas supply 8 can lead to a reduced fuel gas flow supplied to the combustion air mass flow, accompanied by an increase in the air-fuel ratio of the mixture supplied to the burner 3. The burner 3 can then be started by an ignition device (not shown here). In particular, after a flame is detected at the burner 3, for example, based on the signal from the flame temperature sensor 15 or the flame monitoring sensor 15, the auxiliary valve 13 can be opened by the control unit 7, allowing the heating appliance 1 to switch to normal heating operation with a predetermined air-fuel ratio.

[0043] Fig. 3Figure 1 shows a diagram where the abscissa represents time t and the ordinate represents a pulse-width modulated (PWM) signal from the control system 22 of the conveyor 2. The PWM signal can be expressed as a percentage of the nominal power of the conveyor 2.

[0044] Fig. 4 shows a diagram in which the abscissa axis represents time t and the ordinate axis represents an air mass flow in the combustion air supply 4 determined by means of the air mass flow sensor 12.

[0045] As part of the implementation of the procedure proposed here, the control unit 7 can check the function of the auxiliary valve 13. For this purpose, the pumping unit 2 can be driven to a starting speed 25, as shown by a first speed profile 26, a first PWM signal profile 29, and a first air mass flow profile 32. The starting speed 2 can be reached at time 19, at which the control unit 7 actuates and opens the auxiliary valve 13. A second speed profile 27, a second PWM signal profile 30, and a second air mass flow profile 34 show the expected profile after the auxiliary valve 13, and thus the auxiliary channel 17, opens at time 19. Thus, opening the auxiliary valve 13 and the resulting increase in the supplied fuel gas flow causes a change in the mixture density, combined with a lower power requirement of the pumping unit 2, which leads to an increase in its speed n in the second speed profile 27 after time 19.The speed control reduces the PWM signal (30) according to the second curve, lowering the speed n to the starting speed 25. As expected, the air mass flow also decreases. m , because due to the constant delivered mixture flow, an increased fuel gas flow results in a reduction of the air mass flow m in the supply of combustion air.

[0046] In contrast, a third speed curve 28, a third PWM signal curve 31 and a third air mass flow curve 33 show parameter curves that can indicate that the additional valve 13 and thus the additional channel 17 is not opening.

[0047] It should be noted as a precaution that the numerical terms used here ("first", "second", etc.) primarily serve (only) to distinguish between several similar objects, quantities, or processes, and thus do not necessarily dictate any dependency and / or sequence between these objects, quantities, or processes. Should a dependency and / or sequence be required, this is explicitly stated here, or it will be obvious to a person skilled in the art upon studying the specific configuration described. Where a component can occur multiple times ("at least one"), the description of one of these components may apply equally to all or some of the multiple components, but this is not mandatory. Reference symbol list

[0048] 1 Heating unit 2 Conveyor 3 Burner 4 Combustion air supply 5 Safety valve 6 Heating circuit flow temperature sensor 7 Control unit 8 Gas supply 9 Heating circuit flow sensor 10 Exhaust pipe 11 Heating circuit return temperature sensor 12 Air mass flow sensor 13 Auxiliary valve 14 Main duct 15 Flame monitoring sensor 16 Flame temperature sensor 17 Auxiliary duct 18 Heating circuit 19 Time 20 Exhaust system 21 Mixing duct 22 Control 23 Heat exchanger 24 Gas control valve 25 Starting speed 26 First speed curve 27 Second speed curve 28 Third speed curve 29 First PWM signal curve 20 Second PWM signal curve 21 Third PWM signal curve 32 First air mass flow curve 33 Second air mass flow curve 34 Third air mass flow curve

Claims

1. Method for starting a heating appliance (1) with a pneumatic gas-air compound, comprising a conveyor device (2) which supplies a mixture of combustion air and fuel to a burner (3) of the heating appliance (1), and a divided gas supply with at least one main channel (14) and one additional channel (17), characterised in that, for an ignition process of the heating appliance (1), the additional channel (17) is closed in order to increase the air ratio of the mixture.

2. Method according to claim 1, wherein the additional channel (17) is closed by an additional valve (13).

3. Method according to claim 2, wherein the additional valve (13) can be opened and closed by a coil drive or a stepper motor.

4. Method according to one of the preceding claims, wherein the additional channel (17) is opened when a flame can be detected at a burner (3) by a flame monitor (15).

5. Method according to one of the preceding claims, wherein closing and / or opening of the additional channel (17) is detected / checked by detecting and evaluating at least one parameter from the following group during an opening and / or closing process of the additional channel (17): - a rotational speed n or a control signal of a conveyor device of the heating appliance, - a signal that allows conclusions to be drawn about a combustion air flow rate , - a flame signal at a burner (3) of the heating appliance (1), - a flow temperature and a return temperature of a heating circuit (18) connected to the heating appliance (1).

6. Method according to claim 5, wherein detection of the closure of the additional channel (17) takes place during or prior to an ignition process or during burner operation.

7. Method according to claim 5 or 6, wherein, upon detection of an error during the closing and / or opening of the additional channel (17), information about this is displayed via a display device or made available for retrieval via a network or sent as a message and / or the heating appliance (1) is blocked for start-up.

8. Heating appliance (1) designed for the combustion of a combustible gas, with a pneumatic gas-air compound comprising a conveyor device (2) which supplies a mixture of combustion air and fuel to a burner (3) of the heating appliance (1), and a two-part gas supply with a main channel (14) and an additional channel (17), wherein an additional valve (13) is arranged in the additional channel (17), designed to open or close the additional channel (17) for a gas flow, and a regulating and control device (7), designed to carry out a method according to one of the preceding claims.

9. Computer program comprising instructions that cause the heating appliance of claim 8 to perform the method steps according to one of claims 1 to 7.

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