Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N5/00—Systems for controlling combustion
  • F23N5/02—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium
  • F23N5/14—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using thermo-sensitive resistors
  • F23N5/143—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using thermo-sensitive resistors using electronic means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N1/00—Regulating fuel supply
  • F23N1/02—Regulating fuel supply conjointly with air supply
  • F23N1/022—Regulating fuel supply conjointly with air supply using electronic means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N3/00—Regulating air supply or draught
  • F23N3/08—Regulating air supply or draught by power-assisted systems
  • F23N3/082—Regulating air supply or draught by power-assisted systems using electronic means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N2225/00—Measuring
  • F23N2225/08—Measuring temperature
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N2233/00—Ventilators
  • F23N2233/06—Ventilators at the air intake
  • F23N2233/08—Ventilators at the air intake with variable speed

Definitions

• the invention relates to a method for operating a heater, a heater and a computer program.
• a large number of heating devices which burn a mixture of a fuel, in particular a gas or hydrogen, and ambient air in a combustion chamber in order to generate heat to supply a building or to provide hot water.
• Gas-fired heaters fueled by fossil fuels often utilize the ionization effect, which can be measured based on freely available charge carriers in the flame and at least one electrode in the flame.
• the measured ionization current then acts as a control variable to adjust the composition of the gas mixture in the heater.
• the central physical relationship underlying these systems is a change in the electrical flame resistance depending on the composition of the respective gas mixture.
• Common temperature sensors used for mixture control have a temperature-dependent resistance that is measured (e.g., PTC resistors - "positive temperature coefficient” resistors, or HSI - "hot surface igniter”).
• the resistance of the temperature sensor is subject to the aforementioned aging effects, such as those resulting from oxidation or contamination. Such a drift in the resistance leads over time to incorrect temperature measurements and thus to errors in the control of the gas mixture composition.
• the DE 10 2022 123 899 A1 describes a method for determining the combustion air ratio of a heater using a flame temperature sensor. An operating point of the heater is detected, the flame temperature sensor is then heated, and the supplied mass flow of combustion air is increased until the flame temperature sensor has cooled to the temperature before heating.
• the disadvantage of this method is that it is time-consuming and cannot detect or compensate for sensor drift.
• the object of the invention is to propose a method for operating a heater, a heater, and a computer program that at least partially overcome the described problems of the prior art.
• the invention is intended to enable combustion control or control of the composition of a gas-air mixture (hereinafter also referred to as the gas mixture) that ensures, at all permissible operating points (i.e., those occurring during normal operation), that the composition of the gas mixture intended for the respective operating point can be adjusted or regulated as precisely as possible.
• a gas-air mixture hereinafter also referred to as the gas mixture
• the heater has at least one combustion chamber with a burner for combusting a gas mixture supplied (to the burner or the combustion chamber), and a temperature sensor with a temperature-dependent electrical resistance for determining a temperature of a flame of the gas mixture combusted by the burner.
• a relative increase in a power parameter is used for combustion control, wherein the relative increase in the power parameter is determined based on a first power parameter value and a second power parameter value.
• the second power parameter value is detected while controlling an electrical power of the temperature sensor to a predetermined power
• the first power parameter value is detected before the start or after the end of controlling the electrical power of the temperature sensor to the predetermined power.
• the method is used to control the combustion of the heater, in particular to adjust the gas mixture or its composition.
• a combustion air ratio also referred to as lambda or air ratio
• lambda or air ratio can be derived or determined from the relative increase in the power parameter, which can be used to control combustion. Therefore, the method can be performed continuously during operation of the heater.
• a proposed method can be carried out fully automatically on a control unit of the heater.
• any sensor drift that may occur in the temperature sensor has no influence on the relative increase in the performance parameter.
• the method can enable particularly long-term stable combustion control of the heater.
• the electrical power of the temperature sensor can be regulated to the specified power using a suitable controller, for example a PI controller.
• a suitable controller for example a PI controller.
• the controller can regulate the electrical power, which corresponds to the product in terms of voltage and current, to the specified power.
• the specified power can be selected to cause a relevant temperature rise above a limit. For a heater, this can vary depending on the temperature sensor used. For example, a suitable power range can be from 2 watts to 20 watts. If necessary, a suitable power level that enables precise combustion control can be determined through laboratory tests. Before the start or after the end of the regulation of the electrical power of the temperature sensor thus refers to periods in which the regulation of the power of the temperature sensor is not active.
• the temperature sensor cannot be energized before and after the start of the regulation of the power, so that the temperature sensor is not heated. While the power of the temperature sensor is being regulated, the power regulation is active, which means that the electrical power of the temperature sensor is regulated and thus the temperature sensor is heated.
• the heater can in particular comprise at least one combustion chamber as a heat generator, in particular a gas condensing boiler.
• the heat generator releases thermal energy through the combustion of a fuel and can transfer this to a heating circuit via at least one heat exchanger, wherein consumers of the heating circuit can be connected to the heater via a flow and a return.
• the exhaust gases produced during combustion can be fed to an exhaust system via an exhaust duct of the heater.
• a circulation pump in the heating circuit can be configured to circulate a heat transfer medium (heating water), wherein heat transfer medium heated via a heating flow can be fed to consumers, such as convectors or surface heating systems, and returned to the heat generator or the at least one heat exchanger via a heating return.
• the heater can have a conveying device, in particular a fan, which can supply a mixture of combustion air and fuel (e.g., hydrogen) to a burner of the heater via a mixture channel.
• the conveying device can comprise a power control, in particular a speed controller.
• the speed controller can usually provide a speed signal of the fan.
• the heater can, for example, have an electronic gas-air connection, in which a signal from a flame monitor can be used to draw conclusions about the flame(s) and the combustion air ratio (also referred to as lambda or air ratio), thus enabling control of the combustion air ratio or the composition of the gas mixture.
• the burner can, for example, comprise at least one flat perforated plate or a cylindrical perforated plate arranged between a burner cavity and the combustion chamber.
• the burner cavity can be connected to the mixture channel in such a way that the gas mixture can flow from the mixture channel through the burner cavity, exit the perforated plate, and be combusted there.
• An ignition device can also be arranged in the region of the perforated plate, designed to ignite a mass flow of the gas mixture exiting through the perforated plate.
• the heater can be designed, in particular, to burn hydrogen as a fuel or a mixture containing hydrogen.
• the fuel mixture can have a hydrogen content of at least 55%, at least 80%, or at least 90%.
• the heater has a flame monitor.
• the flame temperature can be detected by means of a suitably positioned temperature sensor, in particular a PTC (positive temperature coefficient thermistor) resistor or sensor or a hot-surface igniter (HSI).
• a suitably positioned temperature sensor in particular a PTC (positive temperature coefficient thermistor) resistor or sensor or a hot-surface igniter (HSI).
• PTC positive temperature coefficient thermistor
• HAI hot-surface igniter
• the heater comprises a control unit that is designed to at least regulate the composition of the gas mixture supplied to the combustion chamber or to regulate the combustion of the gas mixture based on the relative increase in the power parameter.
• the control unit is also designed to carry out the described method.
• the first power parameter value and/or the second power parameter value can be detected in a steady-state state of the power parameter.
• a steady-state state is characterized by a parameter to be detected that does not oscillate or does not oscillate within a predetermined tolerance range, and thus only moves within predetermined tolerances within a predetermined period of time.
• the power parameter is largely stationary during detection. This can appear particularly relevant when detecting the second power parameter value, since a settling or stabilization of the power control of the temperature sensor should be waited for before detection takes place.
• a transient process can also occur when the first power parameter value is detected after the electrical power of the temperature sensor has been regulated to the predetermined power, or as a result of a modulation process of the heater prior to carrying out the method.
• the relative increase in the performance parameter can be determined by dividing the second performance parameter value by the first performance parameter value. This can be done automatically on the control unit of the heater.
• the combustion control can be carried out at least based on the relative increase in the performance parameter, a detected air mass flow or a detected speed of the conveying device and predefined reference data.
• a detected air mass flow and/or a detected speed of a conveying device of the heater can be used to determine a combustion parameter for the combustion control.
• the detected air mass flow and the detected speed of the conveying device thus indicate two possible parameters that allow a conclusion to be drawn about the mass flow of combustion air flowing through the heater.
• the reference data can establish a relationship between the determined relative increase in the performance parameter and a combustion parameter, in particular the combustion air ratio.
• the reference data can establish a relationship between a combustion parameter to be determined (combustion air ratio) and the relative increase in the performance parameter in conjunction with the air mass flow recorded at the time the first and/or second performance parameter value was recorded, or the speed of the conveying device recorded at the time the first and/or second performance parameter value was recorded.
• the reference data can be determined in advance in laboratory tests on a reference heater and stored, for example, in a memory of the heater's control unit.
• the inclusion of a recorded speed or a recorded air mass flow, since the relative increase in the performance parameter, particularly with a resistance value of the temperature sensor as a performance parameter, can depend on the occurring air mass flow. This relationship can also be taken into account by the reference data.
• the performance parameter can be a detected electrical resistance of the temperature sensor.
• the supplied air mass flow and the gas valve position are kept constant. In other words, the operating point of the heater is kept constant.
• the first performance parameter value and the second performance parameter value can be a detected speed of a conveyor device of the heater or a detected supplied air mass flow.
• a gas valve position is kept constant, and a resistance value of the temperature sensor is controlled using the air mass flow or the speed as the actuator.
• the gas valve position i.e., an opening position of the gas valve
• the resistance of the temperature sensor is controlled using the detected air mass flow or the detected speed as the actuator. In other words, the detected air mass flow or the detected speed is adjusted such that the resistance of the temperature sensor is kept constant.
• the first power parameter value and the second power parameter value can now be recorded, with the second power parameter value being recorded while regulating the electrical power of the temperature sensor to a predetermined power.
• the first power parameter value corresponds to a recorded speed or a recorded air mass flow before or after the start or end of regulating the electrical power of the temperature sensor to the predetermined power
• the second power parameter value corresponds to the recorded speed and the recorded air mass flow while regulating the electrical power of the temperature sensor to the predetermined power.
• the performance parameter value can be a detected gas valve position of the heater.
• a detected rotational speed of a conveyor device of the heater or a detected supplied air mass flow is kept constant, and a resistance value of the temperature sensor is controlled using the gas valve position as an actuator.
• This embodiment can be understood as the inversion of the previously described embodiment. For clarification, a sequence of this embodiment is described below as an example.
• the air mass flow flowing through the heater or a rotational speed of the conveyor device is kept constant, and the resistance of the temperature sensor is controlled using the detected gas valve position as an actuator. In other words, the detected gas valve position is adjusted such that the resistance of the temperature sensor is kept constant.
• the first performance parameter value and the second performance parameter value can now be detected, with the second performance parameter value being detected while an electrical power of the temperature sensor is controlled to a predetermined power.
• the first performance parameter value corresponds to a detected gas valve position before starting or after completing the regulation of the electrical power of the temperature sensor to the specified Power and the second power parameter value corresponds to the detected gas valve position while controlling the electrical power of the temperature sensor to the specified power.
• the detected air mass flow can be the signal from a mass or volume flow sensor or a signal from a differential pressure sensor. Other options for detecting air mass flow, for example, using a temperature sensor, are also expressly included.
• the speed of the conveying device can be measured or recorded. Fans often provide a speed signal, or this is accessible to a combustion control system anyway.
• the speed signal can also be a control signal from a speed controller, which is often implemented as a PWM (pulse-width modulated) signal.
• the first performance parameter value can be recorded before the electrical power of the temperature sensor is regulated to the specified power, and a third performance parameter value can be recorded after the electrical power of the temperature sensor is regulated to the specified power.
• a performance parameter value is recorded before, during, and after the electrical power of the temperature sensor is regulated to the specified power.
• the mean value of the first performance parameter value and the third performance parameter value is formed and the relative increase of the performance parameter is determined by the quotient of the second performance parameter value divided by the formed mean value.
• a heating device comprising a conveying device for a gas mixture, a combustion chamber with a burner for burning the supplied gas mixture, a temperature sensor for determining a temperature of a flame of the gas mixture burned by the burner and a control unit which is designed at least for regulating the composition of the gas mixture supplied to the combustion chamber or for regulating the combustion of the gas mixture on the basis of the temperature measured by the temperature sensor and is suitable for carrying out the described method.
• the electrically heatable temperature sensor has, in particular, a temperature-dependent electrical resistance.
• the combusted gas mixture has a lambda value/combustion air ratio.
• the temperature sensor has, in particular, an electrical voltage-resistance curve dependent on the lambda value.
• At least one data processing system which has means which are suitably equipped, configured or programmed to carry out the described method or which carry out the method.
• the heating device comprises a data processing system, e.g., a control unit, which has means for executing the steps of the described method and/or has means that are suitably equipped, configured, or programmed to execute the steps of the method or that execute the method.
• a data processing system e.g., a control unit
• the control unit has means for executing the steps of the described method and/or has means that are suitably equipped, configured, or programmed to execute the steps of the method or that execute the method.
• the means include, for example, a processor and a memory in which instructions to be executed by the processor are stored, as well as data lines or transmission devices that enable the transmission of instructions, measured values, data or the like between the elements mentioned.
• the “means” may in particular comprise one or more of the following components: controller(s), microcontroller, data memory, data connection, display devices (such as a display), counter or timer, at least one further sensor, an energy source, etc.
• a computer program comprising instructions which cause the described heating device to carry out the described method or which, when the computer program is executed by a computer, cause the computer to carry out the described method or the steps of the described method.
• a computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the described method or the steps of the described method.
• the statements regarding the method are particularly transferable to the heating device, the data processing system and/or the computer-implemented method (i.e. the computer program and the computer-readable storage medium) and vice versa.
• first primarily serve (only) to distinguish between several similar objects, quantities, or processes, and therefore do not necessarily specify any interdependence and/or sequence of these objects, quantities, or processes. Should a dependence and/or sequence be required, this is explicitly stated here or will be obvious to the person skilled in the art upon studying the specifically described embodiment. To the extent that a component can occur multiple times (“at least one"), the description of one of these components may apply equally to all or part of the majority of these components, but this is not mandatory.
• Fig. 1 shows a heater 1 that can include a burner 3 arranged in a combustion chamber 2.
• a heat exchanger 18 can be arranged on the combustion chamber 2, which transfers the heat generated during combustion to a heat transfer medium.
• Combustion air can be sucked in by a conveying device 9, in particular designed as a fan, via a combustion air supply 8, in which a flow sensor 12 can be arranged.
• the conveying device 9 can be connected to a speed controller 10, which can regulate a speed n of the conveying device 9 by means of a pulse-width modulated (PWM) signal.
• a gas valve 13 can add fuel gas from a gas supply 14 to the sucked-in air mass flow of combustion air and comprise a safety valve and a gas control valve for controlling the mass flow of fuel gas to be added.
• the generated gas mixture 4 of fuel gas and combustion air can flow via a mixture channel 11 to the burner 3 and burn there to form a flame 6.
• the burner 3 may have a cylindrical shape, whereby the gas mixture 4 can flow from the mixture channel 11 into the burner 3.
• the combusted gas mixture 7 can be fed to an exhaust system 16 via an exhaust channel 15 of the heater 1.
• a control unit 17 can be configured to regulate the heater 1. For this purpose, it can be electrically connected, for example, to the speed controller 10, the conveyor device 9, the gas valve 13, a temperature sensor 5 arranged in the combustion chamber 2, and a network 19 (Internet).
• the control unit 17 can be configured to carry out the method proposed here and, for example, have a computer program 33 configured to carry out a method proposed here.
• the control unit 17 can be capable of regulating the composition of the gas mixture 4 supplied to the combustion chamber 2 and/or regulating the combustion of the gas mixture 4 based on the temperature measured by the temperature sensor 5.
• the temperature sensor 5 of the heater 1 has a temperature-dependent resistance R T and is electrically heated.
• Fig. 2 shows a first curve 20 of the resistance RT of the temperature sensor 5 as a power parameter over time t, which can occur when carrying out a method proposed here.
• the heater 1 is operated with a lean gas mixture 4 while the first curve 20 is being recorded, for example with a combustion air ratio of 1.4.
• the power control of the temperature sensor 5 is switched on 21 to a predetermined power, as a result of which the resistance RT increases.
• the power of the temperature sensor 5 can be controlled, for example, with a PI controller, to a power of 5 watts.
• the second power parameter value 30 can be recorded in a period 23.
• the power control is then switched off 22.
• the resistance RT drops and oscillates, whereby after the settle-down, a period 24 results for recording the first power parameter value 28.
• the first power parameter value 28 can also be recorded before the power control is switched on 21.
• a relative increase in the resistance R T as a power parameter can be determined by forming a quotient of the second power parameter value 30 divided by the first power parameter value 28. In the Fig. 2 an absolute increase of 31 of the first trend of 20 is recorded.
• Fig. 3 shows a second curve 25, which was recorded analogously to the first curve 20, but during the combustion of a rich gas mixture 4, for example with a combustion air ratio of 1.1.
• an absolute increase 32 of the second curve 25 is recorded.
• the absolute increase 31, 32, and thus also the relative increase, is visible for a lean gas mixture 4 according to Fig. 2 significantly higher than with a rich gas mixture 4 according to Fig. 3 .
• the relative increase in the performance parameter can allow a conclusion to be drawn about the current combustion air ratio of the supplied gas mixture 4 and can thus be used for combustion control of the heater 1.
• Fig. 4 shows a curve of the resistance RT as a power parameter as a third curve 26 in the event of a drift in the operating point 27, which can be caused, for example, by heating of the gas valve 13.
• a drift in the operating point 27 of the heater 1 can be compensated by detecting a first power parameter value 28 before switching on 21 the power control and a third power parameter value 29 after switching off 22 the power control.
• an average of the first power parameter value 28 and the third power parameter value 29 can be calculated, which at least partially compensates for the drift in the operating point.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Control Of Combustion (AREA)

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Citations (5)

• 2024
  • 2024-03-22 DE DE102024108228.3A patent/DE102024108228A1/de active Pending
• 2025
  • 2025-03-18 EP EP25164296.3A patent/EP4621292A1/fr active Pending

Patent Citations (5)

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