Method for operating a heating device, computer program, control and control device, and heating device to implement the method

Abstract

A method for operating a heating appliance (1) is proposed, which includes a conveying device (2) for conveying a combustion mixture of fuel and combustion air to a burner (3) and a flame temperature sensor (13) for detecting a temperature (20). The method may include at least the following steps: a) detecting an operating point and associated operating parameters of the heating appliance (1), b) heating the flame temperature sensor (13), c) increasing the supplied mass flow of combustion air until the temperature (20) of the flame temperature sensor (13) corresponds to the temperature (20) detected in step a), and detecting the required change in the mass flow of combustion air to cool the flame temperature sensor (13) to the temperature (20) detected in step a), and d) determining a combustion air ratio (27) based on the change in the mass flow of combustion air detected in step c).The method enables the detection and compensation of a sensor drift of a flame temperature sensor (13) used for flame monitoring and a related third element of a determined combustion air ratio (27).

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] A variety of heating devices are known that feed a combustion mixture of a fuel, in particular a fuel gas such as natural gas or hydrogen, conveyed by a conveying device, to a burner and burn it, and use the resulting heat to supply a building.

[0003] These heating appliances typically have a control system for the composition of the combustion mixture and thus the combustion air ratio (also known as lambda or air ratio). This is usually achieved using one or more signals from a flame monitoring system, which both monitors the presence of a flame at the burner and can also be used to regulate the combustion air ratio.

[0004] Flame monitoring often involves measuring the flame's ionization current, from which the combustion air-fuel ratio can be inferred. However, measuring the ionization current is not reliably possible with hydrogen-powered heating appliances because the combustion of hydrogen does not produce a sufficient number of free charge carriers. Therefore, other sensor systems are used in hydrogen-powered heating appliances, in particular measuring the radiation emitted by the flame, especially UV radiation, or measuring the flame temperature. DE 10 2004 055 716 C5 proposes a method for controlling a combustion device that uses temperature measurement as an input parameter.

[0005] In particular, temperature sensors used to measure flame temperature can be subject to sensor drift, meaning a slow change in the signal under identical measurement conditions. When used for controlling the air-fuel ratio, sensor drift can lead to an unsafe control system, for example, a combustion mixture with an excessively high proportion of fuel (hydrogen) and an air-fuel ratio (lambda) λ < 1, i.e., a rich mixture.

[0006] Sensor drift can be monitored, for example, using a parallel lambda sensor. However, lambda sensors are expensive, and the heating unit also requires structural modifications.

[0007] DE 10 2004 030 300 A1 describes a method for adjusting an operating parameter of a combustion unit, in which the mixing ratio of the supplied air-gas mixture is set based on a maximum of the temperature generated by the combustion unit. However, the method only allows for indirect control of the mixing ratio. Furthermore, when the method is implemented and the mixing ratio is varied, unsafe operating conditions can occur.

[0008] IT MI 20 130 013 A1 describes a flame control device for a premixing burner that enables self-adjustment. It proposes the use of a flame temperature sensor that detects the temperature of an outer surface of a combustion chamber. The detected temperature is used to maintain a constant flame response curve and thus a constant air-fuel ratio. However, the device does not allow for sufficiently precise combustion control and cannot compensate for sensor drift.

[0009] US Patent 8,500,441 B2 describes a method for controlling a combustion system in which a signal from a temperature sensor, which detects a temperature in the flame region, is used to regulate the combustion air ratio, regardless of the type and quality of the supplied gas. This method also fails to provide sufficiently accurate combustion control and cannot compensate for sensor drift.

[0010] DE 37 16 641 C2 also describes a burner device for combustion control, but this solution also does not enable sufficiently accurate combustion control and cannot compensate for sensor drift.

[0011] US 10,502,418 B2 describes a mixing device for fuel gas and combustion air with a thermal mass flow sensor. Due to the lack of a combustion parameter, this solution cannot provide precise control.

[0012] 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. The invention is intended to enable the verification of a sensor signal from a temperature sensor for controlling a combustion mixture in a heating device, in particular a hydrogen-powered heating device.

[0013] 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.

[0014] These problems are solved by the features of the independent claims. Further advantageous embodiments of the solution proposed here are specified in the dependent 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.

[0015] This involves a method for operating a heating appliance, wherein the heating appliance includes a conveying device for supplying a mixture of fuel and combustion air to a burner and a flame temperature sensor. The method comprises at least the following steps: a) Determining an operating point and associated operating parameters of the heating device, including a temperature detected by the flame temperature sensor; b) Heating the flame temperature sensor; c) Increasing the supplied mass flow of combustion air until the temperature of the flame temperature sensor corresponds to the temperature detected in step a); and determining the required change in the mass flow of combustion air to cool the flame temperature sensor to the temperature detected in step a); and d) Determining a combustion air ratio based on the change in the mass flow of combustion air detected in step c).

[0016] Steps a), b), c), and d) can be performed at least once in the specified order. In particular, steps a) to d) can be performed at regular intervals (hourly or minutely) during the operation of a heating appliance. This procedure serves, in particular, to verify a signal from a flame temperature sensor and / or a set combustion air ratio of the combustion mixture.

[0017] 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 flow and a return line. 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 of 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 line and returned to the heat generator or the at least one heat exchanger via a heating return line.

[0018] For this purpose, the heating appliance can have a conveying device, in particular a blower, that can supply a combustion mixture of combustion air and fuel (hydrogen) to a burner of the heating appliance. The conveying device can include a power control, in particular a speed controller. The heating appliance can form a pneumatic gas-air system in which a mass flow of fuel gas supplied via a gas supply is added to a mass flow of combustion air according to a negative pressure (control pressure) at a throttling point, such as a Venturi nozzle, so that a predefined (specified) combustion air ratio (air ratio, lambda) can be established.The heating appliance can alternatively feature an electronic gas-air mixture control system, in which a signal from a flame monitor allows for inferences about the flame and the combustion air-fuel ratio (also known as lambda or air-fuel ratio), thus enabling its regulation. The heating appliance can be specifically designed for the combustion of hydrogen as fuel or a mixture containing hydrogen. The mixture can have a hydrogen content of at least 80% or at least 90%.

[0019] Furthermore, the heating appliance may have flame monitoring. This may include a flame temperature sensor designed to detect the flame temperature or a temperature that provides an indication of the flame temperature (burner or housing temperature). In particular, the flame temperature sensor is located in or in the immediate vicinity of the heating appliance's flame.

[0020] In principle, any temperature sensor can be used to measure the flame temperature of the heating device. In particular, a resistance-based temperature sensor, such as a thermistor (NTC) or positive temperature coefficient (PTC), a platinum or silicon measuring resistor, or even a semiconductor temperature sensor can be used.

[0021] According to a preferred embodiment, the temperature sensor can be an ignition device, in particular a hot-surface igniter (HSI) of the heating device. Advantageously, this does not increase the complexity of the heating device, and no additional components or structural modifications to the heating device are necessary to carry out the method proposed here.

[0022] According to one embodiment, the supplied mass flow of fuel gas (and thus the opening position of the gas valve) can remain constant during steps a) to c), so that a change (increase in the combustion air ratio λ) occurs during step c). Advantageously, this ensures that the heating device does not enter unsafe operating states during the execution of the procedure proposed here.

[0023] It is understood that the signals from several (different) flame temperature sensors and thus several measured temperatures can also be included in the method proposed here.

[0024] To carry out the procedure proposed here, the heating appliance can be in operation, and its control system can adjust the combustion air ratio based on a measured flame temperature. For the procedure to be carried out, the heating appliance should not be modulated, i.e., its operating point should not change, or such changes should have occurred shortly beforehand, so that the heating appliance is in a state that is as steady as possible.

[0025] According to step a), an operating point and associated operating parameters of the heating appliance can be recorded. An associated operating parameter of the heating appliance is, in particular, the temperature of the flame temperature sensor or a temperature determined by the flame temperature sensor. Step a) can be performed, in particular, by a control unit of the heating appliance, whereby the recorded operating parameters can be stored in a memory of the control unit.

[0026] According to one configuration, at least the following operating parameters can be recorded: a mass flow of combustion air, based on a signal from the conveying device and / or a flow sensor, a mass flow of fuel, based on a valve position of a gas valve and / or a flow sensor.

[0027] According to one embodiment, the conveying device can in particular be a blower and a performance of the conveying device can be its rotational speed.

[0028] According to step b), the flame temperature sensor can be heated. In particular, the flame temperature sensor can be heated by a predetermined temperature difference.

[0029] According to one embodiment, the flame temperature sensor can be heated using electrical energy. Heating by a predetermined temperature difference can be achieved, in particular, by heating the flame temperature sensor with a predetermined electrical power. The (current) temperature of the flame temperature sensor can then be continuously measured.

[0030] According to step c), the supplied mass flow rate of combustion air can be increased until the temperature of the flame temperature sensor corresponds to the temperature measured in step a), and the necessary change in the mass flow rate of combustion air can be measured. Increasing the supplied mass flow rate of combustion air enhances the cooling effect, or the effect of the forced convection caused by the mass flow of combustion air, thus cooling the flame temperature sensor. This allows the necessary change in the power output of the conveying system to be measured, which is required to cool the (heated or electrically powered) flame temperature sensor to the temperature measured in step a).Due to the different physical properties of fuel and combustion air, the change in the performance of the conveying device also depends on the combustion air ratio, so that this can be determined from the calculated change in the performance of the conveying device.

[0031] According to one design, the change in the performance of the funding institution to be recorded could, for example: This could be a change in rotational speed, a change in a control signal (for example, a PWM (pulse width modulated) signal), and / or a change in the power consumption of the conveying device.

[0032] In this context, it should be noted that a mass flow rate (combustion air, fuel, or a mixture of both) can also characterize a volume flow rate, and vice versa. Thus, a mass flow rate can easily be converted into a volume flow rate, and vice versa, if the density and temperature of the medium are known.

[0033] According to step d), a combustion air ratio can now be determined based on the required change in the output of the conveying device recorded in step c). For this purpose, a reference relationship can be used, for example, which was empirically determined beforehand in (laboratory) tests on a reference heating device and assigns a combustion air ratio to a determined required change in the mass flow rate of combustion air for cooling the flame temperature sensor.

[0034] According to one embodiment, the reference relationship can also be a characteristic map depending on a modulation point of the heating device.

[0035] According to an optional step e), a deviation of the combustion air ratio determined in step d) from the combustion air ratio stored in step a) can be compensated. For this purpose, for example, a correction function can be determined which, implemented in the control system of the heating appliance, converts a combustion air ratio determined by the flame temperature sensor into a corrected combustion air ratio. Alternatively or cumulatively, the setpoint or actual value of the temperature sensor can be iteratively adjusted in the control system according to the deviation to be compensated.

[0036] To compensate for sensor drift, a compensation routine is performed at regular intervals or as needed. With the heating unit running and at a given operating point, the following sequence is preferably carried out: 1 - Save operating point: First, the heating unit states from the starting point are saved. These include, in particular, the air volume (fan speed, air mass flow measurement, etc.), the gas volume (valve position, gas mass flow measurement, etc.), and the temperature measurement from the mixture control. 2 - Hold unit state: Now the control is paused and the state is held, i.e., the air volume and gas volume remain constant. 3 - Energize the flame temperature sensor (e.g., 5W power-controlled): Electrical power is applied to the flame temperature sensor of the mixture control, causing the flame temperature sensor to heat up compared to the starting point in step 1. 4 - Increase fan speed (lambda rises and the sensor is cooled) until temperature = initial temperature: Now the air volume is gradually increased. This causes the lambda value to rise and the sensor to cool.The airflow is increased until the temperature reached is the one recorded as the starting point in step 1. 5 - Store required speed difference: Software can evaluate the required airflow difference necessary for cooling the input electrical power. If the difference is greater / less than an expected (stored or calibrated) difference, the sensor setpoint can be iteratively increased / decreased until the target speed difference is reached again. The reason for this is that the required airflow for cooling the supplied electrical energy depends on the initial state of the device.

[0037] 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 carry out the procedure proposed here. The computer program can, in particular, be executed on a control unit of the heating device.

[0038] Another aspect that is proposed is a machine-readable storage medium on which the computer program is stored.

[0039] The machine-readable storage medium is usually a computer-readable data carrier.

[0040] In addition, a control unit for a heating appliance is proposed, designed to carry out a procedure proposed herein. This control unit may, for example, include a processor. In this context, the processor can execute the procedure stored in the control unit's memory. The control unit may be electrically connected to a conveying device and a flame temperature sensor. Furthermore, data acquired or required during the execution of this proposed procedure can be stored in the control unit's memory, such as an operating point acquired in step a) or related operating parameters and / or a reference reference.

[0041] Another aspect proposed is a heating appliance comprising a control and regulation device. This heating appliance can be a gas-fired appliance, specifically a hydrogen-powered gas-fired appliance. The gas-fired appliance can include a burner and a delivery system for supplying a mixture of fuel (hydrogen) and combustion air to the burner. Furthermore, the heating appliance can include a flame temperature sensor, which can be positioned on the burner in such a way that the flame temperature can be detected directly or indirectly.

[0042] Another aspect proposes the use of a detected speed change of a conveying device of a heating appliance, wherein the detected speed change is required to cool a temperature sensor by a predetermined temperature amount and is used to determine a combustion air ratio of the heating appliance.

[0043] 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.

[0044] This document describes a method for operating a heating appliance, a computer program, a control and monitoring device, a heating appliance, and its application, which at least partially solve the problems described with reference to the prior art. In particular, the method for operating a heating appliance, the computer program, the control and monitoring device, the heating appliance, and its application contribute, at least in part, to verifying a combustion air ratio determined from the flame temperature of a heating appliance and, if necessary, to compensating for any errors in this ratio.

[0045] A further advantage is that the method proposed here can be implemented entirely by computer and therefore does not require any structural changes to a heating device.

[0046] 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 proposed here, Fig. 2: a heating device proposed here, and Figs. 3 to 6: parameter curves that can occur when carrying out a method proposed here.

[0047] Fig. 1Figure 1 shows an exemplary and schematic representation of the sequence of a procedure proposed here. The execution of steps a), b), c, and d), depicted in blocks 110, 120, 130, and 140, can be carried out at least once in the specified order during a regular procedure. The procedure serves to verify a combustion air ratio (λ) 27 determined by a flame temperature sensor 13 and, if necessary, to correct it. The procedure can be carried out, in particular, on a heating appliance 1 that is in operation.

[0048] Fig. 2Figure 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 via a combustion air supply 4, in which a mass flow sensor may be arranged, by a conveying device 2, in particular designed as a blower. The conveying device 2 can be connected to a speed controller 6, which can regulate the speed n of the conveying device 2 by means of a pulse-width modulated (PWM) signal. A gas valve 5 can add fuel gas from a gas supply 14 to the drawn-in mass air flow of combustion air and includes a safety valve and a gas control valve for controlling the mass flow of fuel gas to be added. The generated mixture of fuel gas and combustion air can flow to the burner 3 via a mixture channel 11 and be ignited there by an ignition device 12 during a start-up process of the heating appliance 1.The burner 3 can have a cylindrical shape, the base of which can be attached to a burner door 15 in such a way that the combustion mixture can flow from the mixture channel 11 into the burner 3. After combustion, the combustion products can be discharged to the outside via an exhaust pipe 9 of the heating appliance and an exhaust system 10. A heat exchanger 16 can also be arranged in the combustion chamber 8, which can transfer the heat generated during combustion to a heat transfer medium circulating in a heating circuit.

[0049] The heating device 1 proposed here can be configured specifically for the combustion of hydrogen. Furthermore, the heating device 1 can have a flame temperature sensor 13 in a burner door 15 as a device for flame monitoring.

[0050] A control unit 7 can be configured to control the heating appliance 1. For this purpose, it can be electrically connected, for example, to the speed controller 6, the conveying device 2, the gas valve 5, and the flame temperature sensor 13. The control unit 7 can be configured to carry out a procedure proposed here.

[0051] The Figs. 3 to 6 The parameter profiles shown are those that can occur when carrying out a procedure proposed here, namely a profile of a valve position 17 of the gas valve 5, a rotational speed 18 of the conveying device 2, an electrical power 19 for heating the flame temperature sensor 13, a temperature 20 of the flame temperature sensor 13 and the combustion air ratio 27 in the Figs. 3 and 4 for normal operation with a combustion air ratio (λ) 27 in a range of approximately 1.35 and in the Figs. 5 and 6with an increased proportion of fuel gas in the combustion mixture and a resulting lower combustion air ratio 27 of approximately 1.15.

[0052] As part of the implementation of the procedure proposed here, an operating point and associated operating parameters of the heating device 1 can be recorded in block 110 according to step a). The operating parameters to be recorded can, in particular, be a mass flow of combustion air, based on the rotational speed 18 of the conveying device 2, a mass flow of fuel, based on a valve position 17 of a gas valve 5, and / or a temperature 20 of the flame temperature sensor 13.

[0053] Step a) can be performed while the heating device 1 is in operation. Step a) can be carried out by the control unit 7.

[0054] In block 120 according to step b), the flame temperature sensor 13 can be heated. The heating can begin at a first time 21 by subjecting the flame temperature sensor 13 to a power 19 of approximately 5 W [watts] for heating. This allows the temperature 20 of the flame temperature sensor 13 to increase from approximately 900°C [degrees Celsius] to 1000°C by a temperature change 26.

[0055] In block 130, according to step c), the supplied mass flow of combustion air can be increased until the temperature 20 of the flame temperature sensor 13 corresponds to the temperature 20 detected in step a), in this case, the temperature 20 at the first time point 21 being approximately 900 °C. For this purpose, from a second time point 22, the rotational speed 18 of the conveying device 2 can be increased until, at a third time point, the temperature 20 of the flame temperature sensor 13 at the first time point 21 is reached. In addition, the necessary change in the mass flow of combustion air to cool the flame temperature sensor 13 to the temperature 20 detected in step a) (of approximately 900 °C) can be detected (i.e., a temperature change 26 corresponding to the heating in step b)), in this case approximately 100 K [Kelvin]). The corresponding rotational speed change 25 is, according to the... Figs. 3 and 4approximately 500 rpm [revolutions per minute] and when operating with a rich combustion mixture with a lower air-fuel ratio in the Figs. 5 and 6 approx. 625 rpm. An increase in the time required for the cooling of the flame temperature sensor 13 in step c) can also be observed, from the first time point 21 to the second time point 22.

[0056] In block 140, according to step d), a combustion air ratio 27 can be determined based on the change in the mass flow of combustion air recorded in step c), in this case the change in rotational speed 25.

[0057] 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

[0058] 1 Heater 2 Feed system 3 Burner 4 Combustion air supply 5 Gas valve 6 Speed ​​controller 7 Control unit 8 Combustion chamber 9 Exhaust pipe 10 Exhaust system 11 Mixture channel 12 Ignition device 13 Flame temperature sensor 14 Gas supply 15 Burner door 16 Heat exchanger 17 Gas valve position 18 Feed system speed 19 Heating output Flame temperature sensor 20 Temperature 21 First time point 22 Second time point 23 Third time point 24 Duration 25 Speed ​​change 26 Temperature change 27 Combustion air ratio

Claims

1. Method for operating a heating appliance (1) comprising a conveyor device (2) for conveying a combustion mixture of fuel and combustion air to a burner (3) and a flame temperature sensor (13) for detecting a temperature (20), wherein the method comprises at least the following steps: a) detecting an operating point and associated operating parameters of the heating appliance (1), including a temperature (20) detected by the flame temperature sensor (13), b) heating the flame temperature sensor (13), c) increasing the mass flow of combustion air supplied until the temperature (20) of the flame temperature sensor (13) corresponds to the temperature (20) detected in step a), and detecting the required change in the mass flow of combustion air to cool the flame temperature sensor (13) to the temperature detected in step a) (20) detected in step a), and d) Determining a combustion air ratio (27) based on the change in the mass flow of combustion air detected in step c).

2. Method according to claim 1, wherein in step a) at least one of the following operating parameters of the heating appliance (1) is further detected: - a mass flow of combustion air, based on a signal from the conveyor device (2) and / or a flow sensor, - a mass flow of fuel, based on a valve position (17) of a gas valve (5) and / or a flow sensor.

3. Method according to one of the preceding claims, wherein during the execution of steps a) and b) the mass flows of combustion air and fuel are kept constant.

4. Method according to one of the preceding claims, wherein in step b) the flame temperature sensor (13) is supplied with electrical energy in order to heat it.

5. Method according to one of the preceding claims, wherein the conveyor device (2) is a blower and in step c) a rotational speed of the conveyor device (2) is increased and a change in rotational speed (25) is detected.

6. Method according to one of the preceding claims, wherein in step d) a combustion air ratio (27) is determined by comparing the change in the mass flow of combustion air detected in step c) with a reference relationship.

7. Method according to one of the preceding claims, wherein in a further step e) a deviation of the combustion air ratio (27) determined in step d) from a combustion air ratio (27) stored in step a) is compensated.

8. Control and regulation device (7) for a heating appliance (1), the heating appliance comprising a conveyor device (2) for conveying a combustion mixture of fuel and combustion air to a burner (3) and a flame temperature sensor (13) for detecting a temperature (20), wherein the control and regulation device (7) is designed to cause the heating appliance (1) to carry out the method according to one of claims 1 to 7.

9. Heating appliance (1) comprising a flame temperature sensor (13) for detecting a temperature (20), a conveyor device (2) for conveying a combustion mixture of fuel and combustion air to a burner, further comprising a control and regulation device (7) according to claim 8.

10. Computer program comprising instructions which, when executed by the control unit of a heating appliance (1) according to claim 9, cause the heating appliance (1) to perform the steps of a method according to one of claims 1 to 7.

Images