Method for determining and / or using the operating power of a burner device

Abstract

The invention relates to a method for determining and / or applying the operating performance of a combustion device (10), in particular a water heater device, which has at least one combustion unit (12), at least one gas supply unit (14) and at least one control and regulation unit (16), with at least one operating step (18) in which a gaseous medium is supplied to the combustion unit (12) via the gas supply unit (14), with at least one measuring step (28) in which an ion parameter of a flame generated by the combustion unit (12) is measured as an ionization signal by means of a sensor unit (22) of the combustion device (10), which allows a conclusion to be drawn about an ion current,wherein in at least one operating step (18) a gas flow into the combustion device (10) is regulated by means of a valve unit (24) of the gas supply unit (14) and wherein in at least one operating step (18) the control and regulation unit (16) of the combustion device (10) actuates the valve unit (24) and / or performs at least one evaluation step (26). It is proposed that in at least one evaluation step (26) the operating power is determined via the stability of the electrical ionization current, wherein the sensor unit is configured to determine an ionization current that is at least substantially proportional to a flame intensity of the flame, in particular an ion formation rate in the flame.

Description

State of the art

[0001] There is already a method for determining and / or applying the operating performance of a combustion device, in particular a water heater device, which has at least one combustion unit, at least one gas supply unit and at least one control and regulation unit, with at least one operating step in which a gaseous medium is supplied to the combustion unit via the gas supply unit, with at least one measuring step in which an ion parameter of a flame generated by the combustion unit is measured as an ionization signal by means of a sensor unit of the combustion device, which allows a conclusion to be drawn about an ion current,wherein in the at least one operating step, a gas flow into the combustion device is regulated by means of a valve unit of the gas supply unit, and wherein in the at least one operating step, the control and regulation unit of the combustion device controls the valve unit and / or carries out at least one evaluation step. Disclosure of the invention

[0002] The invention is based on a method for determining and / or applying the operating performance of a combustion device, in particular a water heater device, which has at least one combustion unit, at least one gas supply unit and at least one control and regulation unit, with at least one operating step in which a gaseous medium is supplied to the combustion unit via the gas supply unit, with at least one measuring step in which an ion parameter of a flame generated by the combustion unit is measured as an ionization signal by means of a sensor unit of the combustion device, which allows a conclusion to be drawn about an ion current,wherein in the at least one operating step, a gas flow into the combustion device is regulated by means of a valve unit of the gas supply unit, and wherein in the at least one operating step, the control and regulation unit of the combustion device controls the valve unit and / or carries out at least one evaluation step.

[0003] It is proposed that in at least one evaluation step the operating performance is determined via the stability of the electrical ionization current.

[0004] In this context, a "combustion device," in particular a water heater device, is understood to mean, in particular, a device configured to generate thermal energy by means of a combustion process and to transfer it to another medium. The thermal energy is preferably transferred to a liquid medium. The thermal energy is particularly preferably transferred to water. In particular, the water is heated by the combustion device. The combustion device is particularly preferably designed as a continuous-flow heater and / or boiler. Thermal energy is preferably supplied to the water by the combustion device, in particular a combustion unit of the combustion device. Furthermore, it is conceivable for the combustion device to transfer thermal energy to an intermediate medium, and consequently, the intermediate medium supplies the thermal energy, particularly with a loss value, to the water.Preferably, a flame is generated by a combustion unit of the combustion device. A gaseous medium serves as the fuel. Preferably, all design parameters, such as pressure distribution at the gas inlet, gas quality, ambient conditions, relative humidity, and altitude, are determined before an operating step to ensure the minimum performance for all manufactured devices.

[0005] In this context, a "combustor unit" is understood to mean, in particular, a unit of the combustion device that is configured to directly generate thermal energy. Preferably, a flame is generated by the combustion unit. Preferably, the thermal energy is generated by a flame. Preferably, the thermal energy is provided by the flame. Preferably, the flame is generated by the addition of a fuel through the combustion unit. Preferably, the fuel is formed and / or maintained by a gaseous medium. Preferably, the fuel is formed as a combustion fluid, in particular as a combustion gas. For example, the flame could be generated by the oxidation of fuel, in particular natural gas and / or hydrogen and / or methane. Alternatively, any other fuel that appears appropriate to a person skilled in the art for generating a flame by means of oxidation is conceivable.Preferably, the fuel is introduced into the combustion unit of the combustion device. Preferably, the fuel is injected into the combustion unit under pressure, for example, by a pump. Preferably, the combustion unit has at least one burner element. Preferably, a flame is generated by at least one burner element in an operating step. Preferably, the burner element is configured to generate a flame from a fuel.

[0006] In this context, a "gas supply unit" is understood to mean, in particular, a unit that supplies a gaseous medium to a combustion unit in one operating step. The gas supply unit is preferably designed to be gas-tight. The gas supply unit preferably has at least one gas reservoir element configured to receive a process gas. Alternatively, a gas supply unit without a gas reservoir element is conceivable, wherein the gaseous medium is supplied from a permanently installed gas supply. In particular, the at least one gas reservoir element is arranged at a distance from the combustion region. The gas supply unit preferably has a line element configured to conduct the gaseous medium to at least one combustion unit. The line element is preferably configured to supply a gaseous medium to a combustion unit in a coordinated manner.Preferably, the conduit element forms a coupling point with the gas reservoir element. Preferably, the conduit element forms a coupling point with the combustion unit. Preferably, the conduit element has a circular cross-section perpendicular to a main extension direction of the conduit element. A "main extension direction" of an object is understood in particular to mean a direction that runs parallel to a longest edge of a smallest geometric cuboid that just completely encloses the object.

[0007] In this context, a "control and regulation unit" is understood to mean, in particular, a unit with at least one control electronics unit. "Control electronics" is understood to mean, in particular, a unit with a processor unit and a memory unit, as well as with an operating program stored in the memory unit. The control and regulation unit is preferably configured to perform an evaluation step and an adaptation step. The control and regulation unit is preferably configured to control and regulate a valve unit. In particular, the ion parameters determined by the sensor unit in a measurement step are processed by the control and regulation unit in an evaluation step. The control and regulation unit is configured to determine the stability of the ion parameter from an ion parameter in an evaluation step.

[0008] In this context, an "operating step" is to be understood in particular as a method step in which a combustion process is carried out by the combustion device, in particular the combustion unit. Particularly preferably, in one operating step, a medium, in particular water, is heated by a combustion device through a combustion process. The operating step corresponds in particular to regular operation of the combustion device. Preferably, in one operating step, thermal energy is generated by the combustion unit. Preferably, in one operating step, a gaseous medium is ignited at the combustion unit, so that a flame is created. Preferably, in one operating step, thermal energy is generated by generating a flame by means of the combustion unit. Preferably, a medium, in particular water, is heated using the generated thermal energy.Preferably, in one operating step, a medium, in particular water, is heated to a target temperature. In particular, it is conceivable that, upon reaching the target temperature, the operating step is terminated and / or the operating power is reduced within one operating step. Particularly preferably, the method for determining and / or applying the operating power of a combustion device is configured to be used at a low power in one operating step. Preferably, the method for determining and / or applying the operating power of a combustion device is configured to determine an operating power in one operating step and, as a result, automatically calibrate the operating power to a minimum operating power.In this context, "operating power" is understood to mean, in particular, the power generated in one operating step by the combustion of the gaseous medium in a combustion unit. In particular, the operating power can be defined by an ionization current. Furthermore, it is conceivable that the operating power is defined by a temperature. Alternatively, any definition of operating power that appears reasonable to a person skilled in the art is conceivable.

[0009] In this context, a "measuring step" is understood to mean, in particular, a method step in which a sensor unit determines a process parameter of the flame generated by the combustion unit. Preferably, in a measuring step, an ion parameter of a flame generated by the combustion unit is measured as an ionization signal using a sensor unit of the combustion device, which allows a conclusion to be drawn about an ion current. Particularly preferably, an ionization current is determined in a measuring step using the sensor unit. In particular, the ionization current determined in a measuring step is transmitted to the control and regulation unit.

[0010] In this context, a "sensor unit" is understood to mean, in particular, a unit designed to record at least one parameter and / or a physical property. Recording can occur actively, such as by generating and transmitting an electrical measurement signal, and / or passively, such as by detecting changes in the properties of a sensor component. Various sensor units that would be deemed appropriate by those skilled in the art are conceivable. Preferably, the sensor unit is configured to measure an ion parameter of a flame generated by the combustion unit as an ionization signal, which allows a conclusion to be drawn about an ion current. Preferably, the sensor unit is designed as an ionization electrode. Preferably, an ionization current is determined in a measuring step using the sensor unit.The sensor unit is preferably configured to determine an ionization current that is preferably at least substantially proportional to a flame intensity of the flame, in particular an ion formation rate in the flame. The sensor unit preferably has at least one measuring range. The measuring range is preferably configured to generate an electrical current that is at least substantially proportional to the flame intensity. The measuring range is preferably perpendicular to a main extension direction of the burner elements. A "main extension direction" of an object is understood to mean, in particular, a direction that runs parallel to a longest edge of a smallest geometric cuboid that just completely encloses the object.

[0011] In this context, a "valve unit" is understood to mean, in particular, a unit configured to regulate a gas flow into the combustion device. The valve unit is preferably formed in a line element of the gas supply unit. The valve unit preferably controls a gas flow by changing the cross-section of the line element. In particular, it is conceivable for a valve element to be configured as a connecting element between a line element and a combustion unit. Preferably, a cross-section is changed perpendicular to the main extension direction of the line element. Preferably, in one operating step, the valve unit is automatically controlled via a control and regulation unit. In particular, it is conceivable for the valve unit to be operated manually. Alternatively, it is conceivable for the valve unit to additionally enable manual regulation.

[0012] In this context, an "evaluation step" is understood to mean, in particular, a method step in which the process parameters determined by the sensor unit are processed. Preferably, the ionization current determined by the sensor unit is processed in an evaluation step. Preferably, the stability of an ionization current is determined in an evaluation step. In particular, an independent value of an ionization parameter is defined in an evaluation step, which is independent of all parameters that influence the electrical current intensity. In particular, the voltage tolerances during ionization excitation, all design parameters, and the position of the sensor unit, in particular the ionization sensor, relative to the flame are parameters that influence the flame.Particularly preferably, the determined value is at least substantially completely independent of any parameter of the combustion device.

[0013] The inventive design of the method for determining and / or applying the operating power makes it possible to achieve advantageous properties with regard to adaptation to the minimum operating power. In particular, advantageous properties with regard to determining the operating power can be achieved. In particular, a standard combustion device, in particular a water heater device, can be used when carrying out the method for determining and / or applying the operating power. This makes it possible to provide, in particular, an advantageously cost-effective implementation of the method for determining and / or applying the operating power. In particular, by evaluating the operating power via the stability of the operating power, an advantageous determination of the operating power can be provided regardless of the design and / or process parameters of the combustion process of the combustion unit.In particular, the minimum operating range can be advantageously extended to an adaptation and determination using a method of the state of the art.

[0014] Furthermore, it is proposed that in the at least one evaluation step, an assessment of the combustion stability is carried out based on a metric of the variability of the ionization signal based on the determination of the operating power, particularly in a range of low operating power. A "metric" in this context is understood to be a quantity that is insensitive to parameters that influence the electrical current intensity. These include, for example, voltage tolerances of the electronic control unit (ECU) for the excitation driver of the ionization electrode, the position of the ionization sensor relative to the flame, and the gas quality. A range of low operating power is understood in this context to mean, in particular, an operating state of a combustion device in which the device only delivers reduced power.In this range, the combustion device exhibits, in particular, lower fuel consumption and reduced heat or energy output. Preferably, the evaluation step evaluates the combustion stability within a narrow operating power range. Preferably, the at least one evaluation step evaluates the combustion stability within a narrow operating power range of a combustion device with an open exhaust gas. In this context, an "open exhaust gas" is understood to mean that the combustion air is taken directly from the installation room and the exhaust gases are not hermetically sealed from the room. In such devices, the air supply and exhaust gas discharge are not regulated by fans; they are free of mechanical assistance and utilize the natural chimney draft for the combustion air supply and exhaust gas discharge.Preferably, the combustion ionization current is continuously monitored in the evaluation step to assess combustion stability. Particularly preferably, the combustion ionization current is continuously monitored in a low operating power range in the evaluation step to assess combustion stability. Preferably, the stability correlates directly with the combustion stability. Preferably, a flame-lift phenomenon of the combustion can be mapped in an evaluation step based on the combustion stability. In this context, a "flame-lift phenomenon" (flame lift) is understood to mean, in particular, the phenomenon in which a flame lifts from the burner element and loses direct contact with the burner opening. This occurs when the velocity of the outflowing gas-air mixture exceeds the burning velocity of the flame.As a result, the flame can no longer be held stably on the burner and "floats" above the burner element. The flame-lift phenomenon can lead to instabilities in the combustion process, reducing efficiency and increasing safety risks. Preferably, the measurement step and the evaluation step can be performed across the entire modulation range of the combustion device. Preferably, the measurement step and the evaluation step are performed in a range, particularly the modulation range, of low operating power of the combustion device. Preferably, in the evaluation step, the combustion device is indirectly conditioned by assessing combustion stability based on a metric of the variability of the ionization signal.Preferably, in the evaluation step, the occurrence of the flame-lift phenomenon is analyzed based on the assessment of combustion stability in order to identify areas of poor combustion. "Poor combustion" is understood in particular to mean an unstable burner operating range in which, for example, the flame-lift phenomenon occurs. Poor combustion is characterized by inefficient or incomplete combustion of the fuel, which can lead to increased emissions, energy losses, and potential safety risks. Preferably, in the evaluation step, an ionization measurement is assessed in a constant operating range. Preferably, there is a short time window in the constant operating range in which the ionization current is measured without changing any parameters of the combustion device.Preferably, no assessment of different modulation ranges takes place in an evaluation step. Preferably, the evaluation step assesses the current operating performance of the combustion device in an operating step. Preferably, the evaluation step determines a minimum operating performance of the combustion device by assessing the combustion stability based on a metric of the variability of the ionization signal. This allows, in particular, advantageous operation of the combustion device to be achieved. In particular, a modulation range can be expanded advantageously, which enables the combustion device to operate thermostatically under a wider range of operating conditions, for example, at low water flow or high water inlet temperature.

[0015] It is further proposed that in the at least one evaluation step, the normalized variance of the ionization current is determined in order to define the stability indicator independently of the absolute level of the ionization current. In the evaluation step, a stability indicator for the combustion stability is preferably defined by determining the normalized variance of the ionization current, which is independent of changes in the parameters of the combustion device. Preferably, in the evaluation step, a stability indicator for the combustion stability is defined by determining the normalized variance of the ionization current, which is independent of its relative amplitude change during a short time window in which the operating power remains constant. Preferably, in the evaluation step, a measurement step is evaluated in which a relative key figure is used that is evaluated over a small time window.In particular, in the at least one measuring step, an absolute ionization current is measured at a defined time interval of preferably a maximum of 50 ms, particularly preferably a maximum of 40 ms, particularly preferably a maximum of 30 ms, and preferably at least 2 ms. This allows, in particular, an advantageous assessment of combustion stability to be provided independently of other factors influencing the ionization current.

[0016] Furthermore, it is proposed that in at least one evaluation step, the normalized variance of the ionization current be used as an indicator of stability. Preferably, in an evaluation step, the stability of the ionization current is evaluated using the normalized variance of the ionization current. Preferably, the normalization is configured to define the ionization current in an evaluation step independently of influencing factors. In particular, for example, the voltage tolerances during ionization excitation, all design parameters, the position of the sensor unit, in particular of the ionization sensor, relative to the flame are influencing factors that influence the ionization current indirectly via the flame, independent of any parameter of the combustion device. Preferably, in an evaluation step, an operating performance is evaluated using the variance of the stability of the ionization current.Preferably, data points are standardized in an evaluation step. Alternatively, it is conceivable that a standardization is carried out from a graphic or diagram in an evaluation step. Preferably, data points are standardized in an evaluation step using a standardization value. Preferably, a value determined from the measuring step, for example, minimum value, maximum value, mean value, sum and / or median, is used as the standardization value in an evaluation step. Alternatively, a user-defined value is conceivable as the standardization value in an evaluation step. Particularly preferably, the standardization value is determined in an evaluation step using a mean value from the measuring step. Preferably, the data points are divided by the standardization value. This makes it possible, in particular, to provide an advantageous evaluation of the operating performance independent of other factors influencing the ionization current.In particular, an assessment of the minimum operating performance can be provided advantageously.

[0017] It is further proposed that, in at least one evaluation step, the combustion stability be assessed by the stability of the dimensionless or standardized electrical ionization current. "Dimensionless" in this context is understood to mean, in particular, an ionization current that has been scaled to a unitless value by division with a suitable reference value. A dimensionless ionization current is preferably understood to mean a current that has been divided by a characteristic current value to obtain a pure number without physical dimension. The dimensionless ionization current is preferably determined in one evaluation step. "Standardized" in this context is understood to mean, in particular, that the ionization current has been referenced to a specific reference value or standard value in order to put it into context and enable comparability between different measurements or systems.Preferably, standardized can also mean normalized. Preferably, the standardized ionization current is obtained by dividing the measured current by a maximum or characteristic current value. Preferably, the standardization of the ionization current is performed in an evaluation step. Preferably, in an evaluation step, the combustion stability is evaluated by the stability of the dimensionless or standardized electrical ionization current in any operating range, in particular operating point, of the combustion device. Preferably, in the evaluation step, the combustion stability is evaluated at any operating point for a predefined period of time, and the dynamic behavior is assessed, whereby the size variation across different operating points is disregarded. This makes it particularly advantageous to provide a statement about the combustion stability.In particular, combustion stability can be advantageously evaluated at a variable operating power, preferably a minimum operating power.

[0018] It is further proposed that in the at least one measuring step, a measurement of an absolute ionization current takes place at a defined time interval. Preferably, in one measuring step, a measurement of an absolute ionization current takes place at a constant, defined time interval. Alternatively, a measurement of an absolute ionization current at a variable, defined time interval is also conceivable. Furthermore, it is conceivable that in at least one measuring step, an automatic adjustment of the time interval between two measurements of an absolute ionization current takes place by means of the control and regulation unit. In particular, in the at least one measuring step, a measurement of an absolute ionization current takes place at a defined time interval of preferably a maximum of 50 ms, particularly preferably a maximum of 40 ms, particularly preferably a maximum of 30 ms and preferably at least 2 ms.Particularly preferably, in at least one measurement step, an absolute ionization current is measured at a defined time interval of 20 ms. In particular, any time interval between two measurements of an absolute ionization current in a measurement step that appears reasonable to a person skilled in the art is conceivable. Furthermore, it is conceivable that several measurement steps are performed consecutively. This can, in particular, provide advantageous representativeness of the sampling.

[0019] Furthermore, it is proposed that in the at least one evaluation step, the absolute values ​​be normalized to a mean value of the ionization current within a defined time window. Preferably, the normalization value is determined in an evaluation step using a mean value of a data set from the measurement step. Preferably, the data set of the ionization current is determined within a defined time window. In particular, a "defined time window" is understood to mean a time window of preferably a maximum of 10 s, preferably at least 5 s, particularly preferably a maximum of 3 s, and preferably at least 1 s. Particularly preferably, a defined time window is understood to mean a time window between 2 s and 3 s. Preferably, in an evaluation step, all data points within a time window are normalized to the mean using a formula, and the variance is calculated.Preferably, in an evaluation step, the mathematical formula for the empirical variance is supplemented by normalization to the mean value. Preferably, the mathematical formula includes the sum of each value of the ionization current measurement in the data set (xi), the mean value of the ionization current in the data set (. x ) and the number of measurements in the data set (N). IonStability Metric = ∑ i = 1 N x i − x ¯ x ¯ 2 N

[0020] Alternatively, it is conceivable that the variance, standard deviation, and normalization could be performed in a single step. This can be particularly advantageous for providing information about ionization stability. It can also be advantageous for evaluating operating performance.

[0021] It is further proposed that a real-time histogram of the normalized values ​​be created in the at least one evaluation step. Preferably, a real-time histogram of the normalized value of the ionization current is created in one evaluation step. The histogram preferably has an abscissa and an ordinate. Preferably, the normalized value of the ionization current is plotted on the abscissa and the CO emission on the ordinate. Alternatively, any other plotting of the normalized value of the ionization current that appears reasonable to a person skilled in the art is also conceivable. Alternatively, it is conceivable that the plotting is carried out with a time delay. In particular, a time delay of preferably a maximum of 1 s, preferably 0.5 s, and particularly preferably 0.1 s is conceivable. This makes it particularly advantageous to graphically represent an effect on an operating step by means of the ionization stability.

[0022] It is further proposed that the standard deviation of the histogram data be calculated in the at least one evaluation step. Preferably, the standard deviation of all the histogram data is calculated. Alternatively, it is also conceivable that a standard deviation of a temporal range is calculated in one evaluation step. Furthermore, it is conceivable that a plurality of standard deviations from a plurality of subsequent temporal ranges are calculated in one evaluation step. It is further proposed that the variance of the histogram data be calculated in the at least one evaluation step. Preferably, the variance of the histogram data is calculated using the standard deviation. Preferably, the standard deviation is squared to calculate the variance. Preferably, the standard deviation of a time-defined mean is used to calculate the variance. Preferably, an empirical variance is determined.Alternatively, the variance is calculated as the sum of the squared deviations of all measured values ​​from the arithmetic mean divided by the number of measured values. In this context, "variance" is understood as a measure of dispersion that characterizes the distribution of values ​​around the mean. This can be particularly advantageous for providing information about ionization stability. It can also be advantageous for evaluating operating performance.

[0023] Furthermore, it is proposed that in at least one adjustment step, the gas flow is adjusted by means of the valve unit so that the measurement of the normalized value of the ionization current variance corresponds to a target value. An "adjustment step" in this context is understood to mean, in particular, a method step in which a gas flow is regulated and adjusted via the valve unit using the process parameters determined and further processed by the sensor unit. A "target value" in this context is understood to mean a value that generally represents the desired value of a quantitative characteristic of a system, from which the actual value should deviate as little as possible. Preferably, the target value is specified by another system. Preferably, the actual value is equal to the target value.Preferably, in an adjustment step, the gas flow into the combustion unit is reduced if the normalized value of the ionization current variance, measured in a measuring step, is lower than the setpoint. Preferably, in an adjustment step, the gas flow is increased if the normalized value of the ionization current variance, measured in a measuring step, is higher than the setpoint. Preferably, in an adjustment step, no change to the gas flow is made if the actual value is equal to the setpoint. Preferably, in an adjustment step, the gas flow is automatically regulated by the valve unit using the control and regulation unit. In particular, it is conceivable for the adjustment step to take place parallel to an operating step. In particular, it is conceivable for the setpoint to represent a numerical range, wherein each numerical value within this numerical range is considered permissible.Alternatively, it is conceivable for the target value to have a tolerance within which a value measured in a measurement step is considered permissible. In an adjustment step, a tolerance of preferably a maximum of 10%, preferably a maximum of 5%, and particularly preferably a maximum of 3% of a target value is considered permissible. This makes it possible to provide particularly advantageous simplified properties with regard to precise evaluation and resource utilization in a minimum operating state.

[0024] It is further proposed that, in the at least one adjustment step, a minimum operating power is calibrated by assessing combustion stability. Preferably, in the adjustment step, a minimum operating power is calibrated by assessing combustion stability based on a metric of the variability of the ionization signal. A "minimum operating power" is understood, in particular, to be the lowest possible power at which a combustion device can be operated stably, safely, and efficiently without compromising combustion quality or operational reliability. Preferably, the adjustment step calibrates the minimum operating power at which the combustion device is free of a flame-lift phenomenon.Preferably, a minimum operating power is determined based on the operating power determined in the evaluation step with constant combustion stability. Preferably, in the adjustment step, a minimum operating power is calibrated depending on the minimum operating power determined in the evaluation step. This enables particularly advantageous properties with regard to CO emissions of the combustion device. Particularly advantageous properties with regard to the operation of the combustion device can be enabled.

[0025] It is further proposed that, in the at least one adaptation step, an operating range of the combustion device is restricted by assessing the combustion stability. Preferably, in the adaptation step, an operating range of the combustion device is restricted by calibrating the minimum operating power. Preferably, in the adaptation step, an operating range of the combustion device is restricted by increasing or decreasing the minimum operating power. Preferably, the operating range of the combustion device restricted in the adaptation step prevents operation of the combustion device in an unstable combustion range. Preferably, in the adaptation step, the gas flow is used as an actuation periphery to restrict an operating range of the combustion device.Preferably, an inherent adjustment step is utilized in the adjustment step by adjusting the gas flow, which allows combustion to be stabilized. Preferably, in the adjustment step, an operating range in which the flame is unstable and indirectly leads to higher operating emissions is prevented by restricting the operating range of the burner device. This allows, in particular, advantageous operation of the combustion device to be achieved. In particular, an operating range can be advantageously expanded, which allows the combustion device to operate thermostatically under a wider range of operating conditions, for example, at low water flow or high water inlet temperature.In particular, the advantageous properties of low-NOx burner technology can be utilized, as design-related limitations that lead to unstable and clean combustion at low heat input are avoided. Particularly advantageous properties with regard to stable and efficient combustion can be achieved by avoiding conditions under which the combustion device operates with unstable combustion. This also leads to a reduction in CO emissions, as combustion stability is ensured.

[0026] It is further proposed that the target value be defined in at least one development step. The target value is preferably defined as the absolute value of a normalized variance of the ionization current. Alternatively, a definition of the target value as a relative value is also conceivable. In this context, a "development step" is to be understood in particular as a method step in which a target value of a combustion device is defined. The target value is preferably defined for a type of combustion device. The target value is preferably determined in a development step prior to operation in a development phase of the combustion device. The target value is preferably determined experimentally in a development step prior to operation in a development phase of the combustion device.Alternatively, it is conceivable that the target value could be calculated during a development step prior to operation in a development phase of the combustion device. This could provide particularly advantageous simplified properties with regard to precise evaluation and resource utilization in a minimal operating state.

[0027] Furthermore, the invention proposes a combustion device, in particular a water heater device, for carrying out a method according to the invention. Preferably, the combustion unit of the combustion device has at least one burner element. Preferably, a flame above the burner element is generated by the burner element. Preferably, the combustion device has at least one sensor unit. Furthermore, the combustion device has a plurality of sensor units. Preferably, the sensor unit is arranged at a distance from the burner element of the combustion unit. Preferably, a sensor unit is configured to measure at least two burner elements in one measuring step. Preferably, the at least one sensor unit runs perpendicular to a main extension direction of the burner elements.A "main extension direction" of an object is understood to mean, in particular, a direction that runs parallel to the longest edge of a smallest geometric cuboid that just completely encloses the object. Alternatively, the burner elements are arranged on two opposite sides of the sensor unit. The sensor unit preferably has a round cross-section. Preferably, a measurement is performed with the entire sensor unit in one measuring step. Alternatively, only a partial area of ​​the sensor unit could form the measuring area. Preferably, the measuring area of ​​the sensor unit is arranged off-center in an edge area of ​​the flame and / or on the burner element. Preferably, the measuring area of ​​the sensor unit contacts the flame arranged in the edge area in at least one operating step.Preferably, the measuring range of the sensor unit is arranged contact-free and spaced apart from the combustion unit, preferably the burner elements of the combustion unit. The sensor unit preferably has at least one holding unit that fixes the sensor unit to the combustion unit, in particular electrically and / or thermally decoupled from the combustion unit. This makes it possible to provide, in particular, an advantageous combustion device for carrying out a method according to the invention for determining and / or applying the operating power of a combustion device.

[0028] The method according to the invention for determining and / or applying the minimum operating power of a combustion device is not intended to be limited to the application and embodiment described above. In particular, the method according to the invention for determining and / or applying the minimum operating power of a combustion device to fulfill a function described herein may have a number of individual elements, components, units, and method steps that differs from the number stated herein. Furthermore, in the value ranges specified in this disclosure, values ​​within the stated limits are also to be considered disclosed and can be used arbitrarily. drawing

[0029] Further advantages will become apparent from the following description of the drawings. The drawings illustrate an exemplary embodiment of the invention. The drawings, the description, and the claims contain numerous features in combination. Those skilled in the art will also expediently consider the features individually and combine them into useful further combinations.

[0030] They show: Fig. 1 shows a combustion device for carrying out a method according to the invention in a schematic representation, Fig. 2 shows a schematic structure of a combustion device according to the invention, Fig. 3 shows a schematic flow diagram of a method for determining and / or applying the operating performance of a combustion device, Fig. 4 shows a cause-effect relationship diagram of the power consumption, CO emissions and the ionization current stability in a schematic representation, Fig. 5 shows an alternative schematic flow diagram of an operating sequence of the combustion device in which unstable combustion occurs and its effects are shown and Fig. 6 shows an alternative schematic flow diagram of a method for determining and / or applying the operating performance of a combustion device. Description of the embodiment

[0031] Fig. 1shows a combustion device 10a for carrying out a method according to the invention. The combustion device 10a has a combustion unit 12a. The thermal energy is transferred to a liquid medium. Particularly preferably, the thermal energy is transferred to water. The combustion device 10a is designed as a continuous-flow heater and / or boiler. Thermal energy is supplied to the water by the combustion device 10a, in particular by a combustion unit 12a of the combustion device 10a. Furthermore, it is conceivable for the combustion device 10a to transfer thermal energy to an intermediate medium, and consequently for the intermediate medium to supply the thermal energy to the water with a loss value. A flame is generated by means of the combustion unit 12a of the combustion device 10a.All design parameters, such as pressure distribution at the gas inlet, gas quality, ambient conditions, relative humidity and altitude, are determined before each operation to ensure the minimum performance for all manufactured devices.

[0032] The combustion unit 12a of the combustion device 10a has at least one burner element 32a. A flame is generated above the burner element 32a by the burner element 32a. A flame is generated by the combustion unit 12a. The thermal energy is generated by a flame. The thermal energy is provided by the flame. The flame is generated by the addition of a fuel by the combustion unit 12a. The fuel is in the form of a gaseous medium. The fuel is in the form of a combustion fluid, in particular a combustion gas. For example, the flame could be generated by the oxidation of fuel, in particular natural gas and / or hydrogen and / or methane. Alternatively, any other fuel that appears appropriate to a person skilled in the art for generating a flame by means of oxidation is conceivable. The fuel is preferably introduced into the combustion unit 12a of the combustion device 10a.The fuel is injected under pressure into the combustion unit 12a, for example, by a pump. In an operating step 18a, a flame is generated by at least one burner element 32a. The burner element 32a is configured to generate a flame from a fuel.

[0033] The combustion device 10a has at least one sensor unit 22a. Furthermore, the combustion device 10a has a plurality of sensor units 22a. The sensor unit 22a is arranged at a distance from the burner element 32a of the combustion unit 12a. The sensor unit 22a is configured to measure at least two burner elements 32a in a measuring step 28a. The at least one sensor unit 22a runs perpendicular to a main extension direction of the burner elements 32a. Alternatively, the burner elements 32a are arranged on two opposite sides of the sensor unit 22a. The sensor unit 22a has a round cross-section. In a measuring step 28a, a measurement is performed with the complete sensor unit 22a. The sensor unit 22a has at least one measuring region 34a. The measuring region 34a is configured to generate an electrical current that is at least substantially proportional to the flame intensity.The measuring area 34a is oriented perpendicular to a main extension direction of the burner elements 32a. Alternatively, only a partial area of ​​the sensor unit 22a could form the measuring area 34a. The measuring area 34a of the sensor unit 22a is arranged off-center in an edge area of ​​the flame and / or on the burner element 32a. Preferably, the measuring area 34a of the sensor unit 22a contacts the flame arranged in the edge area in at least one operating step 18a. The measuring area 34a of the sensor unit 22a is arranged without contact and at a distance from the combustion unit 12a, in particular the burner elements 32a of the combustion unit 12a. The sensor unit 22a has at least one holding unit 36a, which fixes the sensor unit 22a to the combustion device 12a, in particular electrically and / or thermally decoupled from the combustion unit 12a. The sensor unit 22a is designed as an ionization electrode.In a measuring step 28a, an ionization current is determined using the sensor unit 22a. The sensor unit 22a is configured to determine an ionization current that is preferably at least substantially proportional to a flame intensity of the flame, in particular an ion formation rate in the flame.

[0034] Fig. 2shows a schematic structure of a combustion device 10a according to the invention. The combustion device 10a has a control and regulation unit 16a. The sensor unit 22a measures an ion parameter in a measuring step 28a and transmits it to the control and regulation unit 16a. The processes of the combustion device 10a are regulated and monitored by means of a control and regulation unit 16a. The control and regulation unit 16a is configured to carry out an evaluation step 26a and an adaptation step 46a. In a measuring step 28a, the ion parameters determined by the sensor unit 22a are processed by the control and regulation unit 16a in an evaluation step 26a. The control and regulation unit 16a is configured to determine a stability of the ion parameter from an ion parameter in an evaluation step 26a.The control and regulation unit 16a is configured to control and regulate a valve unit 24a. The valve unit 24a is formed in a line element 48 of a gas supply unit 14a. The valve unit 24a controls a gas flow by changing the cross-section of the line element 48a. In particular, it is conceivable for the valve unit 24a to be designed as a connecting element between a line element 48a and a combustion unit 12a. In an adaptation step 46a, the cross-section perpendicular to the main extension direction of the line element 48a is changed. In an operating step 18a, the valve unit 24a is automatically controlled via a control and regulation unit 16a. In particular, it is conceivable for the valve unit 24a to be operated manually. Alternatively, it is conceivable for the valve unit 24a to additionally enable manual regulation.The control and regulation unit 16a is supplied with electrical energy.

[0035] The combustion device 10a further comprises a gas supply unit 14a. The combustion device 10a comprises a combustion region 50a. The gas supply unit 14a is designed to be gas-tight. The gas supply unit 14a comprises at least one gas reservoir element 38a, which is configured to receive a process gas. Alternatively, a gas supply unit 14a without a gas reservoir element 38a is conceivable, wherein the gaseous medium is supplied from a permanently installed gas supply. The at least one gas reservoir element 38a is arranged at a distance from the combustion region 50a. The gas supply unit 14a comprises a line element 48a, which is configured to conduct the gaseous medium to at least one combustion unit 12a. The line element 48a is configured to supply a gaseous medium to a combustion unit 12a in a coordinated manner. The line element 48a forms a coupling point with the gas reservoir element 38a.The conduit element 48a forms a coupling point with the combustion unit 12a. The conduit element 48a has a circular cross-section perpendicular to a main extension direction of the conduit element. The combustion unit 12a generates thermal energy 40a and exhaust air 42a.

[0036] Fig. 3shows a schematic flow diagram of a method for determining and / or applying the operating performance of a combustion device 10a, in particular a water heater device. The combustion device 10a has a combustion unit 12a, at least one gas supply unit 14a, and at least one control and regulation unit 16a. In at least one operating step 18a, a gaseous medium is supplied to the combustion unit 12a via the gas supply unit 14a. In at least one measuring step 28a, an ion parameter of a flame generated by the combustion unit 12a is measured as an ionization signal by means of a sensor unit 22a of the combustion device 10a, and a conclusion is drawn about an ion current. In the at least one operating step 18a, a gas flow into the combustion device 10a is regulated by means of a valve unit 24a of the gas supply unit 14a.In the at least one operating step 18a, the valve unit 24a is controlled by the control and regulation unit 16a of the combustion device 10a and / or at least one evaluation step 26a is performed. In the at least one evaluation step 26a, the operating power is determined via the stability of the electrical ionization current.

[0037] In an operating step 18a, a medium, in particular water, is heated by a combustion device 10a through a combustion process. In an operating step 18a, thermal energy 40a is generated by the combustion unit 12a. In an operating step 18a, a gaseous medium is ignited at the combustion unit 12a, creating a flame. In an operating step 18a, thermal energy 40a is generated by generating a flame by means of the combustion unit 12a. A medium, in particular water, is heated using the generated thermal energy 40a. In an operating step 18a, a medium, in particular water, is heated to a target temperature. In particular, it is conceivable that, upon reaching the target temperature, the operating step 18a is terminated and / or the operating power within an operating step is reduced.The method for determining and / or applying the operating power of a combustion device 10a is configured to be used at a low power level in an operating step 18a. The method for determining and / or applying the operating power of a combustion device 10a is configured to determine an operating power level in an operating step 18a and subsequently automatically calibrate the operating power level to a minimum operating power level. The method comprises a method sequence 76a. The method sequence 76a comprises at least one measuring step 28a, at least one evaluation step 26a, and at least one adaptation step 46a.

[0038] In a measuring step 28a, an ion parameter of a flame generated by the combustion unit 12a is measured as an ionization signal using a sensor unit 22a of the combustion device 10a, which allows a conclusion to be drawn about an ion current. In a measuring step 28a, an ionization current is determined using the sensor unit 22a. The ionization current determined in a measuring step 28a is transmitted to the control and regulation unit 16a.

[0039] In an evaluation step 26a, the ionization current determined by the sensor unit 22a is processed. In an evaluation step 26a, the stability of an ionization current is determined. In an evaluation step 26a, an independent value of an ionization parameter is defined, which is independent of all parameters that influence the electrical current intensity. In particular, the voltage tolerances during ionization excitation, all design parameters, and the position of the sensor unit, in particular the ionization sensor, relative to the flame are parameters that influence the flame. The determined value is at least substantially completely independent of any design parameter of the combustion device 10a.

[0040] In the at least one evaluation step 26a, the normalized variance of the ionization current is used as an indicator of stability.

[0041] In an evaluation step 26a, the stability of the ionization current is evaluated using the standardized variance of the ionization current. The standardization is designed to define the ionization current independently of influencing factors in an evaluation step 26a. In particular, the voltage tolerances during ionization excitation, all design parameters, and the position of the sensor unit, in particular of the ionization sensor, relative to the flame are influencing factors that indirectly influence the ionization current via the flame, independent of any parameter of the combustion device 10a. In an evaluation step 26a, operating performance is evaluated using the variance of the stability of the ionization current. In an evaluation step 26a, several data points are standardized. Alternatively, it is conceivable that a standardization from a graph or diagram is performed in an evaluation step 26a.In an evaluation step 26a, data points are standardized using a standardization value. In an evaluation step 26a, a value determined from the measurement step 28a, for example, minimum value, maximum value, mean value, sum, and / or median, is used as the standardization value. Alternatively, a user-defined value can be used as the standardization value in an evaluation step 26a. The standardization value is determined in an evaluation step 26a using a mean value from the data points measured in the measurement step 28a. The data points are divided by the standardization value.

[0042] In at least one measuring step 28a, an absolute ionization current is measured at a defined time interval. In one measuring step 28a, an absolute ionization current is measured at a constant, defined time interval. Alternatively, a measurement of an absolute ionization current at a variable, defined time interval is also conceivable. Furthermore, it is conceivable that in at least one measuring step 28a, an automatic adjustment of the time interval between two measurements of an absolute ionization current takes place by means of the control and regulation unit. In at least one measuring step 28a, a measurement of an absolute ionization current is taken at a defined time interval of 20 ms. In particular, any time interval between two measurements of an absolute ionization current in a measuring step 28a that appears reasonable to a person skilled in the art is conceivable.Furthermore, it is conceivable that several measurement steps 28a are performed consecutively. In at least one evaluation step 26a, the absolute values ​​are normalized to an average value of the ionization current within a defined time window.

[0043] The normalization value is determined in an evaluation step 26a using an average value of a data set from the measurement step 28a. The data set of the ionization current is determined within a defined time window. A defined time window is understood to be a time window between 2s and 3s. In an evaluation step 26a, all data points within a time window are normalized to the average value using a formula and the variance is calculated. In an evaluation step 26a, the mathematical formula of the empirical variance is supplemented by normalization to the average value. The mathematical formula assigns the sum of each value of the ionization current measurement in the data set (xi), the average value of the ionization current in the data set ( x ) and the number of measurements in the data set (N).

[0044] In the at least one evaluation step 26a, a real-time histogram 56a of the normalized values ​​is created. Preferably, the normalized value of the ionization current is plotted on an abscissa 52a, and the CO emission is plotted on an ordinate 54a. Alternatively, any other plotting of the normalized value of the ionization current that appears appropriate to a person skilled in the art is also conceivable. Alternatively, it is conceivable that the plotting is carried out with a time delay. In particular, a time delay of preferably a maximum of 1 s, preferably 0.5 s, and particularly preferably 0.1 s is conceivable. In a histogram of the normalized ionization parameters, different stabilities of the ionization current in different temporal measurement ranges can be interpreted. In a first measurement range 58a with a high gradient, the ionization parameter is unstable because the variance between the data points is high.As the variance decreases, a transition to a stable ionization parameter is evident in a second measuring range 60a. In a third measuring range 62a, the variance is constant, thus a stable ionization parameter is present (see ). Fig. 4 ).

[0045] In the at least one evaluation step 26a, the standard deviation of the data in histogram 56a is calculated. The standard deviation is calculated from all data in histogram 56a. Alternatively, it is also conceivable for a standard deviation of a temporal range to be calculated in one evaluation step 26a. Furthermore, it is conceivable for multiple standard deviations of multiple subsequent temporal ranges to be calculated in one evaluation step 26a. In the at least one evaluation step 26a, the variance of the data in histogram 56a is calculated. The variance of the data in histogram 56a is calculated using the standard deviation. To calculate the variance, the standard deviation is squared. The standard deviation is used to calculate the variance within a time-defined mean value. An empirical variance is determined.Alternatively, the variance is calculated as the sum of the squared deviations of all measured values ​​from the arithmetic mean divided by the number of measured values.

[0046] In the at least one adjustment step 46a, the gas flow is adjusted by means of the valve unit 24a so that the measurement of the normalized value of the ionization current variance corresponds to a target value. The target value is specified by another system. In an adjustment step 46a, if the normalized value of the ionization current variance measured in a measuring step 28 is lower than the target value, the gas flow into the combustion unit 12a is reduced. In an adjustment step 46, if the normalized value of the ionization current variance measured in a measuring step 28a is higher than the target value, the gas flow is increased. In an adjustment step 46a, no change to the gas flow is made if the actual value is equal to the target value. In an adjustment step 46a, the gas flow is automatically regulated by the valve unit using the control and regulation unit 16a.In particular, it is conceivable that the adjustment step 46a takes place in parallel with an operating step 18a. In particular, it is conceivable that the target value represents a numerical range, with each numerical value within this numerical range being considered permissible. Alternatively, it is conceivable that the target value has a tolerance within which a value measured in a measuring step 28a is considered permissible.

[0047] The target value is defined in at least one development step 30a. The target value is defined as the absolute value of a normalized variance of the ionization current. Alternatively, a definition of the target value as a relative value is also conceivable. The target value is defined for a type of combustion device 10a. The target value is determined in a development step 30a prior to operation in a development phase of the combustion device 10a. The target value is determined experimentally in a development step 30a prior to operation in a development phase of the combustion device 10a. Alternatively, it is conceivable that the target value is determined computationally in a development step 30a prior to operation in a development phase of the combustion device 10a.

[0048] In the Figures 5 and 6A further embodiment of the invention is shown. The following descriptions and the drawings are essentially limited to the differences between the embodiments, whereby with regard to components with the same designation, in particular with regard to components with the same reference numerals, reference is also made to the drawings and / or the description of the other embodiment, in particular to the Figures 1 to 4 To distinguish the embodiments, the letter a is added to the reference numerals of the embodiment in the Figures 1 to 4 In the example of the Figures 5 and 6 the letter a is replaced by the letter b.

[0049] Fig. 5shows an alternative schematic flow diagram of an operating sequence of the combustion device in which unstable combustion occurs and its effects are illustrated. A user requires a lower operating power 64b. To achieve this, they initiate a targeted reduction in a gas flow 66b. This reduction in the gas flow leads to lean combustion 68b, in which the amount of supplied fuel is reduced while the fuel-to-air ratio remains the same. However, if the gas flow is reduced too much, unstable combustion 70b results, which causes an unstable ion signal 72b and simultaneously causes an increase in CO2 emissions 74b. This unstable ion signal 72b is detected in a measurement step within at least one process sequence 76b of the method. The process sequence 76b is then carried out to determine and calibrate the minimum operating power.The aim is to limit the operating range in such a way that unstable combustion and the resulting increased CO2 emissions are prevented.

[0050] Fig. 6 shows an alternative schematic flow diagram of a method for determining and / or applying the operating power of a combustion device. The method comprises a process sequence 76b. The process sequence 76b comprises at least one measurement step 28b, at least one evaluation step 26b, and at least one adaptation step 46b.

[0051] In at least one evaluation step 26b, based on the determination of the operating power, in particular in a range of low operating power, an assessment of the combustion stability is carried out on the basis of a metric of the variability of the ionization signal. In the evaluation step 26b, the combustion stability is assessed in a low operating power range. In the at least one evaluation step 26b, the combustion stability is assessed in a low operating power range of a combustion device 10b with an open exhaust gas. In the evaluation step 26b, the combustion ionization current is continuously monitored to assess the combustion stability. In particular, in the evaluation step 26b, the combustion ionization current is continuously monitored in a range of low operating power to assess the combustion stability. The stability correlates directly with the combustion stability.In an evaluation step 26b, a flame-lift phenomenon of combustion can be mapped based on the combustion stability. The measurement step 28b and the evaluation step 26b can be performed across the entire modulation range of the combustion device 10b. The measurement step 28b and the evaluation step 26b are performed in a range, in particular the modulation range, of low operating power of the combustion device 10b. In the evaluation step 26b, the combustion device 10b is indirectly conditioned by assessing the combustion stability based on a metric of the variability of the ionization signal. In the evaluation step 26b, the occurrence of the flame-lift phenomenon is analyzed based on the assessment of the combustion stability in order to identify areas with poor combustion. In the evaluation step 26b, an ionization measurement in a constant operating range is assessed.In the constant operating range, a short time window is defined in which the ionization current is measured without changing any parameters of the combustion device 10b. In an evaluation step 26b, no assessment of different modulation ranges takes place. In the evaluation step 26b, a current operating performance of the combustion device 10b is assessed in an operating step 18b. In the evaluation step 26b, a minimum operating performance of the combustion device 10b is determined by assessing the combustion stability based on a metric of the variability of the ionization signal.

[0052] In at least one evaluation step 26b, the normalized variance of the ionization current is determined in order to define the stability indicator independently of the absolute level of the ionization current. In evaluation step 26, by determining the normalized variance of the ionization current, a stability indicator for combustion stability is defined that is independent of changes in the parameters of the combustion device 10b. In evaluation step 26b, by determining the normalized variance of the ionization current, a stability indicator for combustion stability is defined that is independent of its relative amplitude change during a short time window in which the operating power remains constant. In evaluation step 26b, a measurement step 28b is evaluated in which a relative key figure is used that is evaluated over a small time window.In at least one evaluation step 26b, the combustion stability is evaluated by the stability of the dimensionless or standardized electrical ionization current. A dimensionless ionization current is understood to be a current that has been divided by a characteristic current value to obtain a pure number without physical dimension. The dimensionless ionization current is determined in an evaluation step 26b. The standardized ionization current is obtained by dividing the measured current by a maximum or characteristic current value. The standardization of the ionization current is performed in an evaluation step 26b. In an evaluation step 26b, the combustion stability is evaluated by the stability of the dimensionless or standardized electrical ionization current in any operating range, in particular operating point, of the combustion device 10b.In the evaluation step 26b, the combustion stability is evaluated at any operating point for a predefined period of time and the dynamic behavior is assessed, whereby the size variation across different operating points is disregarded.

[0053] In the at least one adjustment step 46b, a minimum operating power is calibrated by assessing the combustion stability. In the adjustment step 46b, a minimum operating power is calibrated by assessing the combustion stability based on a metric of the ionization signal variability. A "minimum operating power" is understood to be the lowest possible power at which a combustion device 10b can be operated stably, safely, and efficiently without compromising combustion quality or operational reliability. In the adjustment step 46b, the minimum operating power is calibrated at which the combustion device 10b is free of a flame-lift phenomenon. A minimum operating power is determined based on the operating power determined in the evaluation step 26b with constant combustion stability.In the adaptation step 46b, a minimum operating power is calibrated depending on the minimum operating power determined in the evaluation step 26b. In the at least one adaptation step 46b, an operating range of the combustion device 10b is restricted by assessing the combustion stability. In the adaptation step 46b, an operating range of the combustion device 10b is restricted by calibrating the minimum operating power. In the adaptation step 46b, an operating range of the combustion device 10b is restricted by increasing or decreasing the minimum operating power. The operating range of the combustion device 10b restricted in the adaptation step 46b prevents operation of the combustion device 10b in an unstable combustion range.In adjustment step 46b, the gas flow is used as an actuation peripheral to restrict the operating range of the combustion device 10b. In adjustment step 46b, an inherent adjustment step is utilized by adjusting the gas flow, which allows for stabilizing combustion. In adjustment step 46b, an operating range in which the flame is unstable and indirectly leads to higher operating emissions is prevented by restricting the operating range of the burner device 10b.

Claims

1. A method for determining and / or applying the operating performance of a combustion device (10), in particular a water heater device, which has at least one combustion unit (12), at least one gas supply unit (14) and at least one control and regulation unit (16), with at least one operating step (18) in which a gaseous medium is supplied to the combustion unit (12) via the gas supply unit (14), with at least one measuring step (28) in which an ion parameter of a flame generated by the combustion unit (12) is measured as an ionization signal by means of a sensor unit (22) of the combustion device (10), which allows a conclusion to be drawn about an ion current,wherein in the at least one operating step (18) a gas flow into the combustion device (10) is regulated by means of a valve unit (24) of the gas supply unit (14), and wherein in the at least one operating step (18) the control and regulation unit (16) of the combustion device (10) controls the valve unit (24) and / or carries out at least one evaluation step (26), characterized in that in which the operating power is determined via the stability of the electrical ionization current in at least one evaluation step (26), wherein the sensor unit (22) is designed to determine an ionization current which is at least substantially proportional to a flame intensity of the flame, in particular an ion formation rate in the flame.

2. Method according to claim 1, characterized in thatin which at least one evaluation step (26) based on the determination of the operating power, in particular in a range of low operating power, an assessment of the combustion stability is carried out on the basis of a metric of the variability of the ionization signal.

3. Method according to one of the preceding claims, characterized in that in which the normalized variance of the ionization current is determined in at least one evaluation step (26) in order to define the stability indicator independently of the absolute level of the ionization current.

4. Method according to one of the preceding claims, characterized in that in which the normalized variance of the ionization current is used as an indicator of stability in at least one evaluation step (26).

5. Method according to one of the preceding claims, characterized in thatin which at least one evaluation step (26) the combustion stability is evaluated by the stability of the dimensionless or standardized electrical ionization current.

6. Method according to one of the preceding claims, characterized in that in which at least one measuring step (28) involves measuring an absolute ionization current at a defined time interval.

7. Method according to one of the preceding claims, characterized in that in which in at least one evaluation step (26) the absolute values ​​are normalized to an average value of the ionization current within a defined time window.

8. Method according to one of the preceding claims, characterized in that in which a real-time histogram (56) of the normalized values ​​is created in at least one evaluation step (26).

9. Method according to one of the preceding claims, characterized in thatin which the standard deviation of the data of the histogram (56) is calculated in at least one evaluation step (26).

10. Method according to one of the preceding claims, characterized in that in which the variance of the data of the histogram is calculated in at least one evaluation step (26).

11. Method according to one of the preceding claims, characterized in that in which at least one adjustment step (46) the gas flow is adjusted by means of the valve unit (24) so ​​that the measurement of the normalized value of the variance of the ionization current corresponds to a desired value.

12. Method according to one of the preceding claims, characterized in that in which at least one adaptation step (46) a minimum operating power is calibrated by assessing combustion stability.

13. Method according to one of the preceding claims, characterized in thatin which at least one adaptation step (46) an operating range of the combustion device (10) is restricted by the assessment of the combustion stability.

14. Method according to one of the preceding claims, characterized in that in which the target value is defined in at least one development step (30).

15. Combustion device (10), in particular water heater device, for carrying out a method according to one of the preceding claims.

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