Method for operating a heating device, computer program, control and control device, heating device and use of a determined electrical resistance

Abstract

A method is proposed for operating a heating appliance (1) with a burner (3) to which a mixture of combustion air and fuel gas is supplied, and with control of the combustion air ratio of the mixture based on a signal from a resistance-based flame temperature sensor (6), comprising at least the following steps: a) determining the electrical resistance of the flame temperature sensor (6) with the burner (3) of the heating appliance (1) switched off, b) determining a deviation (16) from a resistance of the flame temperature sensor (6) assumed for the control of the combustion air ratio, c) determining a scaling of the resistance of the flame temperature sensor (6) that compensates for the deviation (16) determined in step c), and d) operating the heating appliance (1) with the electrical resistance of the flame temperature sensor (6) scaled in this way.Advantageously, the proposed method can compensate for sensor drift of a flame temperature sensor (6) and thus enable long-term stable operation of the heating device (1).

Description

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

[0002] Gas-fired heating appliances often use combustion air ratio (lambda) control based on measuring the flame's ionization current. A measured flame resistance of a gas flame can thus provide information about the combustion air ratio and be used to regulate it. However, hydrogen-fired heating appliances do not contain a sufficient number of free charge carriers in the flame, making a robust evaluation of the ionization current often impossible. Therefore, other parameters / measurement methods are used to control and monitor the combustion air ratio of a hydrogen flame in hydrogen-fired heating appliances. One known method is measuring the UV (ultraviolet) radiation emitted by the flame, but this is expensive and prone to contamination.

[0003] Alternatively, DE 10 2004 065 716 A1 proposes a method for controlling a combustion system that incorporates the burner temperature. A potential problem here is the occurrence of sensor drift in the temperature sensor used. This is almost unavoidable due to aging effects, such as oxidation. Sensor drift is a slow change in the sensor signal under constant measurement conditions and thus causes a control error in the heating appliance, resulting in incomplete combustion and reduced efficiency.

[0004] DE 196 22 126 A1 proposes a method for ignition or flame monitoring in a vehicle heater, in which, depending on a time value and / or a temperature value, the resistance values ​​of the components in the signal path are measured, and the determined total value is stored as a reference value in a memory and included in the measurement during flame monitoring. However, this method is not sufficiently precise for a sensor used for combustion control.

[0005] DE 198 58 994 A1 describes a control method for a gas-fired water heater in which temperature sensors are calibrated after the gas burner is shut down. This calibration can compensate for age-related signal drift in the temperature sensors. However, this method is not sufficiently precise for temperature sensors used for combustion control.

[0006] Based on this, the object of the invention is to propose a method for operating a heating device, a computer program, a control and regulation device, and a heating device that at least partially overcome the problems of the prior art described above. In particular, a simple and cost-effective method for operating a heating device with control of the combustion air ratio, incorporating a temperature signal from the flame, is to be provided, enabling consistently precise control. Furthermore, the method should be suitable for at least partial automation.

[0007] 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.

[0008] This involves a method for operating a heating appliance with a burner, wherein a mixture of combustion air and fuel gas is supplied to the burner, and a control system regulates or adjusts the combustion air ratio of the mixture based on a signal from a resistance-based flame temperature sensor, comprising at least the following steps: a) Determining the electrical resistance of the flame temperature sensor with the burner of the heating appliance switched off, b) Determining the deviation of the resistance determined in step a) from an electrical resistance of the flame temperature sensor assumed for the control of the combustion air ratio, c) Determining a scaling of the electrical resistance of the flame temperature sensor that compensates for the deviation determined in step c), and d) Operating the heating appliance with the electrical resistance of the flame temperature sensor scaled in this way.

[0009] Steps a), b), c), and d) can be performed at least once in the specified order during normal operation. It is possible to execute steps a) and b) at least partially simultaneously or in parallel. Advantageously, steps a), b), and c) can also be repeated at regular intervals or triggered by an event.

[0010] The method serves in particular to ensure the permanently safe operation of a heating device with a temperature signal-based control of the combustion air mixture, especially to compensate for any sensor drift occurring in a flame temperature sensor used.

[0011] 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.

[0012] For this purpose, the heating appliance can have a conveying device, in particular a blower, that supplies a mixture of combustion air and fuel (hydrogen) to a burner of the heating appliance. The heating appliance can also have an electronic gas-air mixture control, i.e., a control of the combustion air ratio (air ratio, lambda) that incorporates a parameter allowing conclusions to be drawn about the properties of the flame, which can in particular be a flame temperature. For this purpose, a target flame temperature, which can correspond to a specified combustion air ratio, can be preset for the control system, depending on the operating state of the heating appliance, in particular its current power output.

[0013] The heating appliance may have a flame temperature sensor arranged in such a way that the flame temperature of the heating appliance can be measured (directly or indirectly). For this purpose, the flame temperature sensor may be located on or in the combustion chamber of the heating appliance, particularly in an area of ​​the combustion chamber where a flame develops during normal use.

[0014] The flame temperature sensor can be positioned at the flame core, base, or tip when the burner is in operation. Alternatively, it can be positioned at a distance from the flame. The sensor could be attached to the burner itself or to a burner door; such a design can be easily integrated into existing assembly processes. The temperatures measured by the flame temperature sensor can range, for example, from 100 °C to 1,500 °C.

[0015] The flame temperature sensor can be any temperature sensor that can provide an electrical signal as a measure of its temperature. This signal can consist of, for example, a measurable electrical resistance, such as a measuring resistor like a platinum or silicon resistor, a thermistor (NTC), or a positive temperature coefficient (PTC). The flame temperature sensor can also be a semiconductor temperature sensor that provides a directly processable electrical signal representative of the temperature. Alternatively, temperature sensors incorporating a quartz crystal, a thermocouple, pyroelectric materials, and / or a fiber optic sensor can also be used.In particular, the flame temperature sensor can also be a hot surface igniter, i.e., a resistance heater that can be heated to a temperature above the ignition temperature of the fuel-air mixture. This advantageously reduces the complexity of the heating device proposed here, since the ignition device, temperature sensor, and a device for heating the temperature sensor can be implemented in a single component. For example, the temperature sensor can be a silicon nitride or silicon carbide hot surface igniter.

[0016] According to one embodiment, steps a), b), and c) can be repeated several times, with the flame temperature sensor in particular being subjected (sequentially) to different (predefined) electrical powers in step a). In each case, the (resulting or determined) electrical resistance of the flame temperature sensor is calculated, in step b) a function of the deviation, and in step c) a function of the scaling. The different electrical powers can consist of applying different electrical voltages.

[0017] According to one embodiment, further operating parameters of the heating device can be included in determining the scaling in step c). Including additional operating parameters of the heating device can enable a more precise determination of the sensor drift.

[0018] According to one embodiment, the other operating parameters can be an ambient temperature, a temperature in the supply air of the heating device, a mass flow in an air supply or a mixture channel of the heating device and / or a temperature in a flow and / or a return of the heating device.

[0019] According to another aspect, a computer program is also proposed, which is designed to (at least partially) execute one of the procedures presented here. In other words, this specifically concerns a computer program (product) comprising instructions that, when executed by a computer, cause it to carry out the procedure proposed here. According to a further aspect, a machine-readable storage medium is also proposed, on which the computer program is stored. The machine-readable storage medium is typically a computer-readable data carrier.

[0020] Another aspect is the proposal for a control unit for a heating appliance, designed to execute a procedure proposed herein. This control unit may, for example, include a processor. In this context, the processor can, for instance, execute the procedure stored in the control unit's memory. Advantageously, the control unit's memory may also contain operating data and, for example, one or more assumed resistance values ​​of the flame temperature sensor.

[0021] Another aspect being proposed is a heating appliance comprising a control and regulation 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, include a control system for the mixture composition of combustion gas and combustion air (combustion air ratio) incorporating a signal from a flame temperature sensor.

[0022] Another aspect involves using the electrical resistance of a flame temperature sensor, measured when the burner of a heating appliance is switched off, to compensate for sensor drift. The heating appliance can then be specifically configured to regulate the combustion air ratio based on the flame temperature determined by the sensor.

[0023] The details, features, and advantageous configurations discussed in connection with the process may also occur in the computer program, control unit, heating device, and application 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.

[0024] This document presents a method for operating a heating appliance, a computer program, a control and monitoring device, a heating appliance, and an application that at least partially solves the problems described with reference to the prior art. In particular, the method for operating the heating appliance, the computer program, the control and monitoring device, the heating appliance, and the application contribute to enabling reliable and long-term stable control of a heating appliance, especially of the combustion air ratio, based on a measured flame temperature. Furthermore, the method proposed here is advantageously fully computer-implemented and therefore requires no structural modifications to the heating appliance.

[0025] 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 sequence of a method presented here, and Fig. 2: a heating device proposed here.

[0026] Fig. 1 Figure 1 shows an exemplary and schematic representation of the procedure proposed here. The procedure serves to calibrate a flame temperature sensor 6 or to compensate for sensor drift of the flame temperature sensor 6. The sequence of steps a), b), c) and d), represented by blocks 110, 120, 130, 140, can occur during normal operation.

[0027] Fig. 2 Figure 1 shows an exemplary and schematic representation of a heating appliance 1 proposed here. This appliance can include a burner 3 arranged in a combustion chamber 8. Combustion air can be drawn in by a blower 2 via a combustion air supply 4, and fuel gas can be added to the intake air flow via a gas valve 5. The mixture of fuel gas and combustion air can then be supplied to the burner 3 via a mixture channel 12. The heating appliance 1 proposed here can be configured, in particular, for the combustion of hydrogen. A heat exchanger 11 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 (not shown here). Combustion products can be conveyed to an exhaust system 10 via an exhaust pipe 9.In the combustion chamber 8, a flame temperature sensor 6 can be arranged in such a way that a flame temperature at the burner 3 can be detected.

[0028] A control unit 7 can be configured to regulate the heating appliance 1. For this purpose, it can be electrically connected to at least the flame temperature sensor 6, the blower 2, and the gas valve 5. Based on the flame temperature detected by the flame temperature sensor 6 at the burner 3, the control unit 7 can deduce the combustion air ratio (lambda) and regulate it.

[0029] Fig. 3 Figure 1 shows an exemplary and schematic diagram that depicts the resistance R of the flame temperature sensor 6 as a function of a rotational speed n of the blower 2. The resistance R can be directly related to the air-fuel ratio. The diagram in Figure 2 shows the resistance R of the flame temperature sensor 6 as a function of the rotational speed n of the blower 2. Fig. 3 Figure 13 shows a resistance curve of a new flame temperature sensor 6 without sensor drift, and thus resistance values ​​that are used by the control unit 7 to regulate the combustion air ratio. A resistance curve 14 of a flame temperature sensor 6 with sensor drift deviates significantly from the resistance curve 13 without sensor drift and thus causes errors in the regulation of the combustion air ratio.

[0030] Fig. 4 Figure 1 shows an exemplary and schematic diagram illustrating the resistance R of the flame temperature sensor 6 as a function of the applied voltage U. Here, a resistance curve 13 is shown for a flame temperature sensor 6 without sensor drift, and a resistance curve 14 is shown for a flame temperature sensor 6 exhibiting sensor drift.

[0031] The resistance curve 14 of the flame temperature sensor 6 with sensor drift can be determined in block 120 according to step a). For this purpose, with burner 3 switched off, the (electrical) resistance R of the flame temperature sensor 6 can be determined by measuring the electric current flowing through the flame temperature sensor 6 at different electrical voltages U and applying Ohm's law.

[0032] In block 120, according to step b), a deviation 16 from an assumed resistance of the flame temperature sensor 6 for controlling the combustion air ratio can be determined. The assumed resistance of the flame temperature sensor 6 can correspond to the resistance curve 13 of a new flame temperature sensor 6. The deviation 16 can also be understood as a deviation curve as a function of the voltage U.

[0033] In block 130, according to step c), a scaling of the resistance (or the resistance curve 14) of the flame temperature sensor 6 can be determined, which compensates for the deviation 16 determined in step c).

[0034] Fig. 5 shows an exemplary and schematic diagram in analogy to Fig. 3 , which maps the resistance R of the flame temperature sensor 6 as a function of a speed n of the blower 2. A scaled resistance curve 15 is shown after performing step c) (block 130), which is (largely) identical to the resistance curve 13 and thus enables precise control of the combustion air ratio by the control unit 7.

[0035] In block 140, the heating device 1 can be operated with the scaled resistance curve 15 of the flame temperature sensor 6, whereby a sensor drift of the flame temperature sensor 6 is compensated. Reference symbol list

[0036] 1 Heater 2 Blower 3 Burner 4 Combustion air supply 5 Gas valve 6 Flame temperature sensor 7 Control unit 8 Combustion chamber 9 Exhaust pipe 10 Exhaust system 11 Heat exchanger 12 Mixture channel 13 Resistance curve of flame temperature sensor without sensor drift 14 Resistance curve of flame temperature sensor with sensor drift 15 Scaled resistance curve 16 Deviation

Claims

1. Method for operating a heating appliance (1) with a burner (3) to which a mixture of combustion air and fuel gas is supplied, and for controlling the combustion air ratio of the mixture on the basis of a signal from a resistance-based flame temperature sensor (6), comprising at least the following steps: a) measuring the electrical resistance of the flame temperature sensor (6) when the burner (3) of the heating appliance (1) is switched off, b) determining a deviation (16) between the electrical resistance determined in step a) and an electrical resistance of the flame temperature sensor (6) assumed for the control of the combustion air ratio, c) determining a scaling of the electrical resistance of the flame temperature sensor (6) which compensates for the deviation (16) determined in step c), and d) operating the heating appliance (1) with the electrical resistance of the flame temperature sensor (6) scaled in this way.

2. Method according to claim 1, wherein the resistance-based flame temperature sensor (6) is a hot surface igniter.

3. Method according to one of the preceding claims, wherein steps a), b) and c) are repeated several times, whereby the flame temperature sensor (6) is subjected to different electrical powers in step a) and the electrical resistance of the flame temperature sensor (6) is determined in each case, and a function of the deviation (16) is determined in step b) and a function of the scaling is determined in step c).

4. Method according to one of the preceding claims, wherein further operating parameters of the heating appliance (1) are included in the determination of the scaling in step c) or the determination of the deviation (16) in step b).

5. Method according to claim 4, wherein the further operating parameters are selected from the following group: an ambient temperature, a temperature in the supply air of the heating appliance (1), a mass flow in an air supply or a mixture channel of the heating appliance (1), a temperature in a flow and / or a return of the heating appliance (1).

6. Control and regulation device (7) for a heating appliance (1), wherein the heating appliance (1) is designed to combust a mixture of combustion air and fuel gas and comprises a resistance-based flame temperature sensor (6), wherein the control and regulation device (7) is designed to cause the heating appliance (1) to perform the method steps according to one of claims 1 to 5.

7. Heating appliance (1) designed to combust a mixture of combustion air and combustible gas, comprising a burner (3), a resistance-based flame temperature sensor (6) and a control and regulation device (7) according to claim 6.

8. Computer programme comprising instructions that cause the heating appliance of claim 7 to perform the steps of the method according to one of claims 1 to 5.

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