METHOD FOR OPERATING A HEATING APPLIANCE, COMPUTER PROGRAM, CONTROL AND REGULATION DEVICE AND HEATING APPLIANCE

Description

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

[0002] A wide variety of heating appliances are known that burn a mixture of fuel, especially gas or hydrogen, and ambient air in a combustion chamber to generate heat for supplying a building or for providing hot water.

[0003] Such heating appliances typically feature flame monitoring, which detects when the flame goes out and thus prevents the escape of unburned fuel. Several methods of flame monitoring are known. Often, the ionization current of the flame is detected, although this is only partially effective with hydrogen-powered heating appliances because a hydrogen flame releases very few charge carriers. For example, the UV (ultraviolet) radiation emitted by the flame(s) can be detected to monitor a hydrogen flame. Measuring the flame temperature using a suitable temperature sensor is also a known method.

[0004] The inertia of the sensors or connected electronics, such as amplifiers or filters, can make it difficult to detect a loss of flame, especially to distinguish it from a regular reduction in the heating appliance's power output.

[0005] From DE 199 03 305 A1, a vehicle heater is known in which flame monitoring is carried out by evaluating a first, second, and third gradient from three temperature sensors. A disadvantage is that the arrangement of three temperature sensors is complex, and furthermore, the proposed flame monitoring cannot provide sufficient detection of flame losses in heating appliances for buildings.

[0006] DE 10 2021 108 014 A1 describes a method for observing or monitoring flames in the combustion chamber of a heating appliance, in which the temperature is measured at a measuring point in or on the combustion chamber and calculated using a mathematical model from other operating data measured on the heating appliance or specified by the user. The measured temperature and / or its behavior over time is compared with the calculated temperature, and if there are deviations above a threshold value, it is determined whether the flame has ignited or gone out. It is desirable to further improve the monitoring, particularly with regard to robustness, in order to distinguish flame loss from a reduction in power output even more reliably.

[0007] US Patent 8,333,584 B2 discloses a method for operating a water heater with a burner arranged in a combustion chamber, in which a temperature reading from the combustion chamber is used to detect flame loss. However, this method is not sufficiently precise, especially for hydrogen-powered burners.

[0008] Based on this, the object of the invention is to propose methods for operating a heating appliance that at least partially overcome the problems of the prior art described above. In particular, the method should enable the reliable detection of a flame loss in a burner, and especially the differentiation between a flame loss and a normal reduction in the heating appliance's output. Furthermore, the method should enable the detection of an impending flame flashback.

[0009] Last but not least, the invention should not significantly increase the complexity of a heating device, and should require no or only minor structural changes to a heating device and / or enable easy integration into an existing production process.

[0010] These problems are solved by the features of the independent claims. Further advantageous embodiments of the solutions proposed here are specified in the dependent claims. In addition, the features specified in the claims are further detailed and explained in the description, which also presents further preferred embodiments of the invention.

[0011] This involves a method for operating a heating appliance. The heating appliance comprises a flame monitoring system for a burner of the heating appliance with at least one sensor, wherein By including a first derivative and a second derivative of the signal from at least one sensor, a comparison value is calculated and a flame state is determined by comparing the comparison value with a first predetermined threshold value.

[0012] According to an alternative embodiment of the method, the flame monitoring of the heating device has at least one UV sensor, and a first derivative of the signal from the UV sensor is compared with a second predetermined threshold value, and raw data of the signal from the UV sensor is compared with a third predetermined threshold value, and a flame state is determined.

[0013] These methods can be performed continuously and permanently during the operation of a heating appliance and serve to reliably monitor the flame, in particular to distinguish between a loss of flame and a normal reduction in the heating appliance's output. Furthermore, the methods enable the detection of an impending flame flashback.

[0014] The heating appliance is, in particular, a gas-fired heating appliance designed to combust a fuel gas, such as natural gas or, more specifically, hydrogen, with the addition of ambient air, and to generate thermal energy, for example, to heat a heat transfer fluid in a heating circuit or to provide hot water. In particular, the heating appliance may be a condensing boiler, which may preferably be designed for the combustion of hydrogen or a hydrogen-containing mixture. The heating appliance typically has a combustion chamber and a conveying device or fan that can convey a mixture of fuel and combustion air via a mixture channel into a combustion chamber in which a burner is located. The combustion products can then be discharged through an exhaust duct of the heating appliance into an exhaust system.

[0015] The heating appliance can, in particular, adjust (modulate) the burner output to the demand. To this end, upon detecting a change in heat demand, for example, by taking into account the flow and return temperatures of a heating circuit connected to the appliance, a control unit can adjust the output of the heating appliance's fan and thus the mass flow of combustion air to the heat demand. Simultaneously, a control system can adjust the fuel mass flow to the changing mass flow of combustion air.

[0016] The burner can comprise at least one perforated plate connected to a burner cavity. The burner cavity is connected to the mixture channel, allowing the combustion mixture to flow through the cavity and perforated plate and be combusted. An ignition device can also be arranged in the area of ​​the perforated plate, configured to ignite a mass flow of combustion mixture exiting through the perforated plate. The burner cavity, also referred to as the burner body, can be designed, in particular, as a cylinder (a right circular cylinder), with one base surface of the cylinder connected to the mixture channel and the opposite base surface closed. Alternatively, the burner cavity can also be cuboidal, bounded on the top by the perforated plate.

[0017] The burner can be located in the combustion chamber of the heating appliance, within a burner door. For this purpose, an opening in the burner door can connect the burner cavity to the mixture channel, and the burner can be attached to the burner door. Additionally, a flame monitor can also be attached to or integrated with the burner door.

[0018] The heating appliance has a flame monitoring system that can detect the presence of a flame at the burner. The flame monitoring system includes a sensor that provides a signal suitable for flame detection. According to an alternative embodiment of the method, the sensor is either a UV sensor, i.e., a sensor for detecting the intensity of the ultraviolet radiation emitted by the flame, or a temperature sensor. The flame monitoring system can also include additional sensors, such as an ionization electrode for detecting the ionization current of the flame. Furthermore, a signal from the flame monitoring system can be used to regulate and control the heating appliance, in particular to determine and regulate the combustion air-fuel ratio of the gas mixture.

[0019] A UV sensor can be oriented so that a flame forming at the burner of the heating appliance lies in the sensor's detection direction. The UV sensor can be located inside the combustion chamber or, protected from the high temperatures inside, outside of it with detection through a viewing window. The UV sensor can provide a signal that corresponds to the intensity of the detected UV radiation. The UV sensor can also have a saturation range, whereby above a certain radiation intensity threshold, the sensor emits a constant signal.

[0020] A temperature sensor can be positioned to detect the temperature of the heater's flame. For this purpose, the temperature sensor can be located on or in the immediate vicinity of the heater's burner. The temperature sensor can be any suitable type, such as a low-temperature (NTC) or positive-temperature (PTC) thermistor, or a semiconductor temperature sensor. Alternatively, the temperature sensor can be a hot surface igniter (HSI), which can also function as the heater's igniter.

[0021] The heating appliance includes a control unit designed to regulate and control its operation. In particular, the control unit can set a predetermined combustion air ratio (also known as lambda) for the heating appliance. The procedures proposed here are suitable for implementation on the control unit.

[0022] Determining a flame condition can include, in particular, detecting flame loss and / or flame flashback. Determining flame flashback can include, in particular, detecting an impending or imminent flame flashback.

[0023] According to the invention, a reference value is calculated using a mathematical first and second derivative (also referred to as the first- and second-order gradients, respectively) of the sensor signal. This reference value is then compared with a predetermined first threshold value, and the flame loss is determined as a result of this comparison. The first and second derivatives denote the first and second differential quotients, respectively, i.e., the slope of the tangent to a function of the sensor signal. This can be done using numerical methods or by interpolating a function of the sensor signal.

[0024] According to one implementation, the comparative value can be calculated by calculating the first and second derivatives, then multiplying each by a predetermined weighting factor, and determining the average as the comparative value. In other words, the first derivative can be multiplied by a first factor and the second derivative by a second predetermined factor.

[0025] According to one configuration, different first or second factors can be specified for different operating states. For this purpose, the factors can be specified, for example, in the form of a characteristic map for defined operating states or ranges of operating states.

[0026] The first and second factors can be determined beforehand using a reference heating device in laboratory tests. For a computer-implemented version of the method proposed here, the first and second factors can be stored in a memory, for example, in the heating device's control unit. Calculating the reference value based on the first and second derivatives can be particularly useful for sensors with inertia. The sensor signal may already be electronically processed (amplified, filtered), which can contribute to the sensor's inertia.

[0027] The first, second and / or third threshold values ​​may also have been determined in advance as part of laboratory tests on a reference heating device and stored in a memory of the control and regulating unit or the heating device.

[0028] Alternatively, a first derivative of the sensor signal is compared with a second predefined threshold, and the raw sensor data is compared with a third predefined threshold, so that a flame loss can be detected. This can, in particular, enable the detection of an impending or early detection of a flame flashback.

[0029] According to an alternative embodiment of the invention, the sensor is a UV sensor that does not operate in the saturation range. In this case, noise in the sensor signal may occur immediately before a flame flashback, but by comparing the raw sensor data with a third threshold and the first derivative with a second threshold, reliable detection of flame loss and / or flame flashback is nevertheless enabled.

[0030] Raw data refers to an electronically unprocessed signal from the sensor, specifically one that has not been electronically amplified or filtered. Due to the inertia of electronic signal processing circuits, using raw sensor data can shorten the time required to detect flame loss or flashback.

[0031] It is noted that the procedure can also be carried out for multiple sensors, for example a combination of the UV sensor and a temperature sensor.

[0032] 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.

[0033] Another aspect proposed is a heating appliance designed for the combustion of fuel in a burner and including flame monitoring with at least one sensor. The heating appliance also includes a control unit configured to execute the procedure proposed here.

[0034] Another aspect involves the proposal of a computer program comprising commands that cause a control unit of a heating device proposed herein to execute a procedure proposed herein. In other words, this specifically concerns a computer program (product) comprising commands that, when executed by the control unit, cause it to carry out a procedure proposed herein.

[0035] The control unit can, 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 can also contain data necessary for executing the procedure, such as a first, second, and / or third threshold value and / or a first and / or second factor, or a characteristic map thereof.

[0036] The details, features, and advantageous designs discussed in connection with the processes may also occur in the computer program and / or 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.

[0037] This document presents methods for operating a heating device, a computer program, and a heating device that at least partially solve the problems described with reference to the state of the art. In particular, the methods, the computer program, and the heating device contribute to providing particularly reliable flame monitoring, enabling robust and reliable detection of a flame or flame loss across the entire modulation range of the heating device. Furthermore, a method proposed here allows for the early detection of a flame flashback.

[0038] A particularly advantageous aspect of carrying out the procedure described here is that it does not require any structural modifications to a heating device, but can instead be implemented through the implementation of software.

[0039] 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 limited by the exemplary embodiments shown. In particular, it should be noted that the figures, and especially the depicted dimensions, are only schematic. They show: Fig. 1: a heating device proposed here, Fig. 2: a sequence of a method proposed here, and Figs. 3 and 4: parameter curves that can occur when carrying out a method proposed here.

[0040] Fig. 1 Figure 1 shows an exemplary and schematic representation of a proposed heating appliance 1 with a flow direction 16. This appliance can have an air supply 4 for combustion air, in which a conveying device 2 is arranged for conveying a mass flow of combustion air. A gas valve 5 can add a mass flow of fuel gas from a gas supply 8 to the mass flow of combustion air conveyed by the conveying device 2. The mixture of fuel gas and combustion air can be supplied to a burner 3 via a mixture channel 12 and combusted. A heat exchanger 13 can be arranged at the burner 3, which can transfer the heat generated during combustion to a heating circuit 14 with a supply line 6 and a return line 9.

[0041] An igniter 17 can be arranged on the burner 3, configured to be heated to a temperature sufficient to ignite the combustion mixture exiting the burner 3. The igniter 17 can, for example, be a glow plug, which can be used as a temperature sensor for carrying out a method proposed here.

[0042] Furthermore, a flame monitoring sensor 15 can be arranged on burner 3. Sensor 15 can be, in particular, a UV sensor or a temperature sensor.

[0043] Downstream of the burner 3, an exhaust pipe 10 can feed combustion products to an exhaust system 11. A control and regulating unit 7 of the heating appliance 1 can be electrically connected to at least the gas valve 5, the sensor 15, the igniter 17 and the conveying device 2.

[0044] Fig. 2 The diagram shows, by way of example and schematically, the sequence of a procedure proposed here. From a signal 18 y(t) of sensor 15, differential 19 can be derived. dy dt , that is, the first derivative of signal 18, can be formed. Subsequently, another differential 19 can be calculated. d y ˙ dt be formed, so that now the first derivative dy dt and the second derivative d y ˙ dt These can each be assigned to a weighting of 20, where the first derivative dy dt and the second derivative d y ˙ dt The values ​​are multiplied by a weighting factor. Subsequently, an average can be calculated. The determined average can be fed into an evaluation logic, which compares the average with a first threshold value and outputs a flame state, 23, as a result.

[0045] Fig. 3 Figure 18 shows an example signal 18 from a sensor 15 configured as a UV sensor, which is not in the saturation range. A flame flashback can occur at time 24. Noise in signal 18 is discernible prior to time 24, the occurrence of the flame flashback. Here, a comparison of a first derivative is particularly useful. dy dt The signal 18 of the sensor 15 with a second predefined threshold and the raw data of the sensor 15 with a third predefined threshold enable safe and early detection of the flame flashback.

[0046] Fig. 4 shows a signal 18 from sensor 15 according to Fig. 2 , whereby sensor 15 is not in a saturation state. A very low level of noise is noticeable in the period leading up to time 24, the occurrence of a flame flashback. Here too, a comparison of a first derivative can be made. dy dt The signal 18 of the sensor 15 with a second predefined threshold and the raw data of the sensor 15 with a third predefined threshold enable safe and early detection of the flame flashback. Reference symbol list

[0047] 1 Heating unit 2 Conveyor 3 Burner 4 Air supply 5 Gas valve 6 Flow 7 Control unit 8 Gas supply 9 Return 10 Exhaust pipe 11 Exhaust system 12 Mixing channel 13 Heat exchanger 14 Heating circuit 15 Sensor 16 Flow direction 17 Igniter 18 Signal sensor 19 Differential 20 Weighting 21 Averaging 22 Evaluation logic 23 Flame state 24 Time of flame flashback

Claims

1. Method for operating a heating appliance (1) comprising a flame monitor for a burner (3) of the heating appliance (1) with at least one sensor (15), wherein a comparison value is calculated on the basis of a first derivative and a second derivative of the signal (18) from the sensor (15) and a flame status (23) is determined on the basis of a comparison of the comparison value with a first predetermined threshold value.

2. . Method for operating a heating appliance (1) comprising a flame monitor for a burner (3) of the heating appliance (1) with at least one UV sensor (15), wherein a first derivative of the signal (18) of the sensor (15) is compared with a second predetermined threshold value and raw data of the signal of the sensor (15) is compared with a third predetermined threshold value, and a flame state (23) is determined.

3. . Method according to claim 1, wherein the comparison value is calculated by calculating the first derivative and the second derivative, multiplying each by a predetermined weighting factor (20) and determining a mean value as the comparison value by means of averaging (21).

4. . Method according to claim 3, wherein different weighting factors (20) are specified for different operating states of the heating appliance (1).

5. . Method according to one of the preceding claims, wherein the determination of the flame state (23) includes a determination of a flame loss and / or a flame flashback.

6. . Method according to claim 2, wherein the signal from the UV sensor (15) is not within a saturation range.

7. . Method according to one of the preceding claims, wherein the heating appliance (1) is operated with hydrogen as fuel.

8. . Heating appliance (1) designed to burn fuel in a burner (3), featuring flame monitoring with at least one sensor (15) and a control and regulation device (7) designed to carry out the steps of a method according to one of claims 1 to 7.

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