EP3969812B1 - Method for monitoring a burner and/or a burner behavior, and burner unit - Google Patents

Description

The invention relates to a method for monitoring a burner and/or the combustion behavior of a burner. An ionization signal is measured and the measured ionization signal is used to monitor the burner. The method preferably also serves to regulate the burner or the combustion behavior of the burner. Furthermore, the invention relates to a burner arrangement with a burner, a heat exchanger, at least one ionization electrode, an air-fuel mixture supply for the burner and a control device. The control device is connected to the ionization electrode and monitors the burner and/or a burning behavior of the burner based on ionization signals measured with the at least one ionization electrode. The burner is preferably a gas burner.

The basic structure of a burner arrangement with a burner, a surrounding heat exchanger and an ionization electrode is shown, for example, in FIG WO 2013/032324 A1 , as well as the EP 2 017 531 B1 .

In such a burner, an air-fuel (or alternatively: air-gas) mixture is burned (see also e.g. the DE 34 15 946 C2 ). The fuel is, for example, propane, butane or z. B. in the gaseous state converted diesel or a mixture of these components. During the burning process, the flame emanates from the surface of the burner.

In order to monitor the presence of a flame or the combustion quality itself and preferably to regulate the behavior of the burner or the combustion process based thereon, it is known in the prior art to use so-called ionization electrodes. The construction and use of ionization electrodes for monitoring or for detecting a flame is described, for example, in B. the EP 1 036 984 A1 , the EP 1 707 880 A1 , the DE 10 2010 055 567 B4 or the EP 2 357 410 A2 . Further measurement arrangements can be found, for example, in WO 2016/140681 A1 , the DE 201 12 299 U1 , the DE 198 17 966 A1 , the DE 10 2017 204 014 A1 , the DE 10 2010 046 954 A1 or the DE 102 20 773 A1 . The control of the combustion behavior that follows the measurement is carried out, for example, by controlling the air ratio. This is done with the aim, for example, of fully premixing surface burners, to achieve a safe, clean and efficient to ensure combustion. For example, a gas valve and a combustion air fan are controlled separately depending on the ionization signal (ie the ionization voltage and/or the ionization current).

In the aforementioned method for monitoring the presence of a flame in a gas burner, the ionization effect of a flame is used. An AC voltage is applied to an area where the flame should be, either via two electrodes or via one electrode and a ground electrode. If a flame burns in this area, this causes a rectifier effect on the AC voltage, which in turn causes a current to flow, e.g. B. caused by the ground to the ionization electrode. This current flow is recorded by measuring electronics and can be provided in the form of an ionization voltage as a measure of the ionization current that actually occurs. A limit value is usually specified for the measured ionization voltage, exceeding which is evaluated as the presence of a flame and falling below it is interpreted to mean that no flame is burning. Overall, an ionization signal is thus determined which, depending on the design, can be a voltage or a current.

It is known to use the surface of the burner (that is, the burner surface) from which the flame emanates as electrical ground. The ionization electrode is attached relative to this surface or to this ground electrode. The position of the electrode relative to the flame or burner surface is decisive for measuring the ionization voltage.

Gas burners and in particular fan-operated gas burners are often exposed to changing environmental conditions that can lead to variable combustion behavior. Such environmental parameters are, for example, air pressure, temperature of the combustion air, gas pressure (ie the pressure at which the fuel gas is supplied), type of gas and also the energy value of the gas. It should be noted that the composition of the fuel gas can often vary. For example, the composition of typical gas mixtures such as LPG (Liquefied Petroleum Gas; Autogas) or typical propane/butane mixtures can vary. Depending on the gas supply, it is possible for pure propane, pure butane or even an undefined propane/butane mixture to be fed in.

Due to the variable environmental parameters, there is therefore the possibility that the gas burner is not operated at the optimum operating point, at which the fuel is burned optimally and the pollutant emissions are minimal. If the ratio between fuel gas and (atmospheric) oxygen is such that complete combustion takes place by the fuel gas reacting completely with the (atmospheric) oxygen, this is referred to as stoichiometric combustion, which corresponds to lambda = 1. If the lambda value is less than 1, i.e. sub-stoichiometric, this means that the air-fuel mixture is such that rich, incomplete combustion occurs with a lack of oxygen. If the lambda value is greater than 1, i.e. over-stoichiometric, the combustion takes place mathematically with excess air. In technical combustion, depending on the area of application, different lambda ranges are used for clean and low-emission combustion. In fully mixing gas burners, a range from lambda = 1.2 to lambda = 1.5 is often used. In this lambda range, the combustion takes place completely and hygienically. Combustion outside these limits leads to reduced efficiency and increased emissions of harmful exhaust gas components.

The EP 0 770 824 B1 provides that, starting from a lean, over-stoichiometric burner operation, the excess air is reduced until the combustion is under-stoichiometric. To do this, the ionization voltage is measured between an ionization electrode and the burner surface. Since the ionization voltage is at a maximum in the case of stoichiometric combustion, the ionization voltage initially increases in the method described when the excess air is reduced. If the ionization voltage subsequently falls after reaching the maximum, this is a sign that the combustion is sub-stoichiometric.

The qualitative course of the ionization signal usually shows reproducible characteristic features in the relevant lambda range. However, the absolute values can be subject to deviations. So e.g. B. the absolute value of the ionization voltage depends on the position of the ionization electrode (another name is also ionization candle), on aging properties, on the nature of the fuel or on the altitude at which the combustion process takes place. Hence a calibration of the measuring arrangement in order to use the ionization signal as a controlled variable for combustion control.

The calibration consists, for example, in finding the aforementioned maximum of the ionization voltage by varying the mixing ratio by making the air-fuel mixture richer. The combustion is gradually made richer until the maximum voltage is determined by running a blower for the combustion air at a lower speed or by allowing more gas to flow in through a valve. Alternatively, it is known to carry out a calibration by leaning the gas-air mixture (see e.g EP 2 014 985 A2 ).

In particular, approaching the rich or sub-stoichiometric range has the disadvantage of increased carbon monoxide formation, increased aging of the burner surface or z. B. also the increased formation of soot.

The object on which the invention is based is to propose a method for monitoring a burner and a corresponding burner arrangement with a burner that can be monitored in this way, which represent an alternative to the prior art.

The invention achieves the object by a method which is characterized in that the ionization signal is measured between an ionization electrode and a counter-electrode spaced apart from a burner surface of the burner.

The monitoring consists, for example, in determining an amount for an ionization voltage or an ionization current from the ionization signal measured relative to the counter-electrode and with a known lambda value, and in comparing this value with a desired value. If the determined value deviates from the target value by more than a tolerance range, the air/fuel mixture is corrected, e.g. B. the proportion of air is increased or decreased. One of the following configurations describes how such a target value is determined or how the method is subjected to a calibration.

The method is used to monitor a burner or specifically the burning behavior of a burner. The method preferably serves to monitor or regulate the combustion of the air-fuel mixture by the burner, ie the combustion behavior of the burner. In one of the following configurations, the method also includes a calibration or a determination of the parameters used for the monitoring.

The burner is preferably a fully premixed surface burner.

In the prior art, the burner or specifically the burner surface, from which the flames generated during combustion emanate, serves as a counter-electrode, opposite which the ionization signal (eg the ionization voltage or the ionization current) is measured with the ionization electrode. In the method according to the invention, however, this takes place via a counter-electrode spaced apart from the burner surface. The counter-electrode is therefore primarily not a part of the burner and is—depending on the configuration—galvanically isolated from the burner or in particular from the burner surface.

The idea is that an electrical ionization signal (that is, depending on the design, an electrical voltage or an electrical current) is measured between the ionization electrode and a counter-electrode spaced apart from the burner surface. From the ionization signal measured in this way, it is then determined whether the firing process is taking place optimally and whether it may be necessary to intervene to regulate the burner or the entire firing arrangement.

In one possible configuration, the counter-electrode is a heat exchanger that at least partially surrounds the burner surface. The heat exchanger or z. B. an inner housing of the heat exchanger facing the burner surface is at least partially electrically conductive. In one embodiment, the heat exchanger is used to transfer the thermal energy of the flue gas generated during combustion to a fluid, e.g. B. water is transferred.

Depending on the design, a single ionization electrode is used, which is further away from the flame area - i.e. in particular from the burner surface - compared to the prior art, or at least two ionization electrodes - For example, at different distances from the burner surface - used to measure ionization signals. When measuring with only one ionization electrode, this is preferably located in one embodiment centrally between the burner surface and the heat exchanger housing as an example of the counter-electrode that differs from the burner.

In one variant, a spark plug is used both to ignite the combustion process of the burner and as an ionization electrode.

In one embodiment--based on the at least one ionization signal--the burner is supplied with an air-fuel mixture. For example, the air supply or the fuel supply is changed. Alternatively or additionally, and/or the composition of an air-fuel mixture with which the burner is supplied is acted upon, e.g. B. changed.

One embodiment provides that the ionization signal is measured between the ionization electrode and the counter-electrode by electrically connecting the counter-electrode to ground.

In addition to the measurement of an ionization signal between the ionization electrode and the counter-electrode, in one embodiment an—additional or supplementary—ionization signal is measured between the ionization electrode and a burner surface of the burner. This ionization signal is thus preferably used in addition to the ionization signal between the ionization electrode and the counter-electrode for monitoring the burner.

In the case of the aforementioned separate ionization signals, the burner surface or, in general, the burner and the counter-electrode are preferably galvanically isolated from one another, ie electrically isolated from one another.

In another embodiment, a type of mixed ionization signal (possibly as a supplementary signal in addition to an ionization signal measured only between the ionization electrode and the counter-electrode) is measured by measuring the heat exchanger—or a heat exchanger housing—and the burner—or preferably the burner surface - are electrically connected to ground and preferably to the same ground.

Depending on the design, the different ionization signals result from the following measuring arrangements: The ionization signal is measured between the ionization electrode and the counter-electrode, with the burner surface being electrically insulated from the counter-electrode. Alternatively or additionally, the ionization signal is measured between, on the one hand, the counter-electrode and burner surface, both of which are connected to one another or to ground, and, on the other hand, the ionization electrode. In a further embodiment--as is customary in the prior art--a (preferably supplementary) ionization signal is measured between the ionization electrode and the burner surface, which is connected to ground and is electrically insulated from the counter-electrode. In one configuration, the counter-electrode is formed in particular by a heat exchanger surrounding the burner surface.

In one configuration, ionization signals are recorded via ionization electrodes located at different positions.

In particular for measuring the ionization signal between the ionization electrode and the counter-electrode, such an ionization electrode is used which is located in a region around the mean distance between the burner (or specifically the burner surface) and the counter-electrode. In one embodiment, the range lies within plus or minus 20% of the mean distance. In another embodiment, the range is within plus or minus 10% relative to the mean distance. In one embodiment, the ionization electrode used for measuring the ionization signal is located closer to the counter-electrode than to the burner surface.

As already explained with regard to the prior art, when using the ionization signals it is advantageous and relevant to safety to carry out calibrations or at least occasionally or at least when starting up for the first time the parameters used for monitoring and preferably controlling the combustion behavior (e.g. target or limit values) to determine.

If the ionization signals are now determined between the ionization electrode and the spaced-apart counter-electrode, as in the method according to the invention, this permits the following method steps, with the great advantage being that the calibration or parameter determination takes place in the emaciated area. Among other things, this reduces the environmental impact.

The method according to the invention provides that for a calibration and/or for a determination of parameters used in the monitoring of the burner, ionization signals are measured in an over-stoichiometric combustion, and that a local extreme (e.g. a minimum of the amount) of the ionization signal is determined as a function of a lambda value of an air-fuel mixture supplied to the burner and is used for the calibration or the determination.

In this embodiment, measurements of the ionization signal in the depleted area, i.e. H. made with an excess of air. In this case, the ratio of air and fuel is varied—preferably only—in the lean range (ie the lambda value is changed) and the respective ionization signals are measured and evaluated. In this case, in particular, a local extremum of the ionization signal is determined as a function of the lambda value. This extremum is then used for calibration or for determining the parameter adjustment that may be required. The advantage of the above steps is that the measurements are carried out in the gentle lean range. The ionization signal is preferably measured between at least one ionization electrode and the counter-electrode spaced apart from the burner. Depending on the sign of the measured ionization signal or depending on how - z. B. considering the magnitude - the ionization signal is evaluated, the local extremum is a minimum or a maximum.

In this context, reference is made to the fact that many investigations have shown that the ionization signals measured relative to the described counter-electrode in the emaciated area show a special course, which is shown in the measurement according to FIG does not occur with the state of the art and which allows the calibration or the determination of the parameters to be carried out.

Therefore, in this method step, a local extremum of the measured ionization signals is determined via lambda in the area of the lean air/fuel mixture (that is, with a lambda value greater than 1). In one embodiment, this extremum is then approached for the calibration. The lambda value is then reduced by a predetermined value, for example by reducing the speed of the combustion air fan, in order to thereby achieve a desired combustion process.

It has been shown that the extreme is in a range of the lambda value in which critical combustion instability does not have to be expected.

Alternatively or additionally, one embodiment provides for ionization signals to be measured via at least two ionization electrodes for calibration and/or for determining the parameters used in monitoring the burner, with the ionization electrodes being at different distances from a burning surface of the burner and/or the counter electrode. The ionization signals are measured—preferably by varying the lambda value of the air/fuel mixture fed to the burner—in such a way that at least the counter-electrode is grounded.

In one embodiment, the ionization signals are measured with different lambda values. In an associated embodiment, an intersection of the two curves (that is, the dependency, for example, of the amplitude of the ionization signal on the lambda value) is used for calibration or for determining the parameters. In this variant, too, in one embodiment, the measurements are preferably only carried out in the over-stoichiometric range.

Furthermore, the invention solves the problem by a burner arrangement, which is characterized in that the control device for monitoring - and / or regulation - the burner and / or a combustion behavior of a burner at least one between The ionization signal measured by the ionization electrode and the heat exchanger is used as the counter electrode.

The refinements of the method are preferably carried out by the burner arrangement, so that the relevant statements also apply to the variants of the burner arrangement. In particular, the control device allows monitoring or control by implementing at least one of the preceding configurations of the method.

One embodiment provides that the ionization electrode is arranged in an area around a mean distance between a burner surface and the heat exchanger.

In a further embodiment, the ionization electrode is arranged in a range of plus/minus 20% around the average distance between a burner surface and the heat exchanger. If the mean distance is M, the ionization electrode in this embodiment is in a range between 0.8*M and 1.2*M.

The configuration according to the invention includes that the control device leans the air-fuel mixture supplied to the burner for a calibration and/or for a determination of parameters used in monitoring the burner via the air-fuel mixture supply and with the leaned air Evaluates fuel mixture measured ionization signals, and that the control device for the calibration or the determination of the parameters determines a local extreme of the ionization signals.

In one variant, an ionization electrode is also used for classic flame monitoring and/or as a spark plug to start a combustion process.

Fig. 1

ein schematisches Blockschaltbild einer erfindungsgemäßen Brenneranordnung,

Fig. 2

einen Schnitt durch ein schematisches Blockschaltbild einer alternativen Ausgestaltung einer erfindungsgemäßen Brenneranordnung,

Fig. 3

zwei Messkurven der Ionisationsspannung für zwei lonisationselektroden in unterschiedlichen Abständen zur Brenneroberfläche, wobei nur die Brenneroberfläche auf Masse liegt, und

Fig. 4

zwei Messkurven der vorgenannten zwei lonisationselektroden, wobei die Brenneroberfläche und der umgebende Wärmetauscher auf Masse liegen und

Fig. 5

zwei Messkurven der vorgenannten zwei lonisationselektroden, wobei nur der die Brenneroberfläche umgebende Wärmetauscher auf Masse liegt.

In detail, there are a number of possibilities for embodying and developing the method according to the invention and the burner arrangement according to the invention. In this regard, reference is made on the one hand to the claims subordinate to the independent patent claims Claims, on the other hand, to the following description of exemplary embodiments in conjunction with the drawing. It shows the:

1

a schematic block diagram of a burner arrangement according to the invention,

2

a section through a schematic block diagram of an alternative embodiment of a burner arrangement according to the invention,

3

two measurement curves of the ionization voltage for two ionization electrodes at different distances from the burner surface, with only the burner surface being grounded, and

4

two measurement curves of the aforementioned two ionization electrodes, with the burner surface and the surrounding heat exchanger being grounded and

figure 5

Two measurement curves of the two ionization electrodes mentioned above, with only the heat exchanger surrounding the burner surface being grounded.

The 1 1 schematically shows a burner arrangement 1 with a burner 2 which is supplied with an air-fuel mixture via an air-fuel mixture supply 5 . The fuel is, for example, a combustible gas such as propane or butane or diesel that has been converted into the gaseous state.

The air-fuel mixture is burned by the burner 2, with a flame—not shown—forming here above the burner surface 2' of the burner 2.

The burner surface 2' is surrounded by a heat exchanger 3, in which the heat generated by the combustion process - in the form of the flame and the flue gas generated - is transferred to another medium, e.g. B. is transferred to water or a glycol-water mixture.

The heat exchanger 3 is designed to be electrically conductive at least partially and preferably on the inner side facing the burner surface 2′. This conductivity allows the heat exchanger 3 to be electrically connected to ground or the ionization voltage to be measured via the at least one ionization electrode 4 in relation to the heat exchanger 3.

An ionization electrode 4, via which an ionization signal (here, for example, the ionization voltage) is measured, serves to monitor or control the firing process--only in the illustrated embodiment. Alternatively, an ionization current can be measured.

To measure the voltage (alternatively the current), either the burner surface 2' of the burner 2 or the previously mentioned, at least partially electrically conductive inner surface of the heat exchanger 3 is connected to ground, so that the ionization electrode 4 is used to measure the ionization voltage with respect to the burner 2 or with respect to the heat exchanger 3 is measured. It is also provided in one embodiment that the heat exchanger 3 and the burner surface 2' are at the same mass, so that the ionization signal from the ionization electrode 4 is measured opposite both as a counter-electrode.

Depending on the variant or method step, the ionization signal is measured by the at least one ionization electrode 4 with the burner surface 2', with the heat exchanger 3 as individual counter-electrodes, or with the burner surface 2' and the heat exchanger 3 as a common counter-electrode. These three differently measured ionization signals are then processed individually or together and used to monitor the burner 2 or as a controlled variable for the combustion behavior of the burner 2 .

In one embodiment, the burner surface 2' and the heat exchanger 3 are of the same mass, so that the ionization signal is measured relative to the burner surface 2' and the heat exchanger 3. The options between which components the electrical voltage is measured are indicated in the figure by the double arrows.

The ionization electrode 4 is connected to the control device 6, which evaluates or processes the measurement signal (ie the ionization signal) and which acts on the air/fuel mixture supply 5 based on the measurement values. This happens e.g. B. by regulating the amount of fuel or e.g. B. by controlling a - the air-promoting blower - not shown here. The action of the control device 6 on the control of the combustion process is indicated by the dashed arrow.

In one embodiment, the control device 6 acts on a - not shown here - starting device for starting a combustion process, if z. B. shows from the ionization signal that no flame is burning. The arrangement 1 thus also allows flame monitoring.

The cut of the 2 1 shows a burner arrangement 1 with two ionization electrodes 4, 4', which are located radially at different distances between the burner surface 2' and the inside of the heat exchanger 3. It can be seen that the burner surface 2 ′ has a circular cross-section in this embodiment, which is surrounded by the inner wall of the circular-cylindrical heat exchanger 3 . The representation is not true to size.

In one embodiment, the burner surface 2' has a diameter of 50 mm, the distance between the burner surface 2' and the inner edge of the heat exchanger 3 being 38 mm. The two ionization electrodes 4', 4 in this exemplary embodiment have a distance of between 5 mm and 9 mm (for the ionization electrode 4' that is closer to the burner surface 2') or between 14 mm and 22 mm (for the ionization electrode 4' that is further from the burner surface 2 'Removed ionization electrode 4) to the outer surface of the burner surface 2'.

The position of the inner ionization electrode 4' corresponds to the configuration known in the prior art. The short distance from the burner surface 2' has the advantage that there is a high probability that the ionization electrode 4' will project directly into a flame. This therefore relates in particular to the use of the ionization electrode 4' for flame detection.

The radially further outer ionization electrode 4 is located here in an area around a central distance between the burner surface 2' and the inner edge of the heat exchanger 3.

In order to measure the ionization signal, in one variant the inner wall of the heat exchanger 3 is grounded and the electrical ionization signal is measured via the ionization electrode 4 with respect to this ground.

The diagrams of Figures 3 to 5 show exemplary measurements that clarify the course of the curves. The measured values are heavily dependent on the given dimensions of the components of the burner assembly or z. B. also from the power with which the burner is operated.

The 3 shows two ionization voltages with the two ionization electrodes 4, 4 'of the embodiment of 2 have been measured.

The voltages were measured (the voltages are plotted with a negative sign on the y-axis) in each case with respect to the burner surface 2', which was grounded. This measurement thus corresponds to the state of the art. During the measurements, the heat exchanger 3 was electrically isolated from the burner surface 2'. The lambda value increasing from left to right is plotted on the x-axis. The mixture thus becomes leaner from left to right.

It can be seen how, starting from a maximum (identified by an arrow) in the lambda=1 range, the voltage values decrease as the lambda value—that is, the lean air-fuel ratio—increases. This curve of the falling signal from a maximum is generally reproducible and is known from the prior art.

The 4 shows the curves of the voltage values when the voltages between on the one hand the respective ionization electrode 4, 4' and on the other hand both the burner surface 2' and the surrounding heat exchanger 3 of the embodiment of FIG 2 be measured. In contrast to the measurements of 3 the burner surface 2 'and the heat exchanger 3 electrically connected to each other and thus on the same ground.

The upper curve was measured with the ionization electrode 4' positioned closer to the burner surface 2'. The lower curve originates from the measurement via the ionization electrode 4, which is further away from the burner surface 2'.

It can be clearly seen that the voltage of the ionization electrode 4' lying closer to the burner surface 2' shows the known falling course of the ionization signal.

Starting from the maximum at lambda=1, the ionization signal of the ionization electrode 4 that is further away initially falls, in order then to rise again after a local minimum—which is the local extremum sought here. In the further course of the measurement curve--not shown here--the amplitude of this ionization signal also falls towards zero, as in the curve of the ionization electrode 4' located closer to the burner surface 2'.

This results in a local minimum in this emaciated area, which is used for calibration. This minimum is marked by an arrow in the figure.

A number of tests have shown that the local minimum mostly occurs between lambda = 1.4 and lambda = 1.6. In the measurement shown here, the minimum is around lambda = 1.55.

After passing through the minimum, the ionization signal increases again and then decreases again. With these larger lambda values, the flame is also clearly lifted off the burner surface.

Experiments show that the position and the form of the minimum in the lean range also depend on the area loading of the burner (ratio of the energy supplied and the usable burner surface). Therefore, in one embodiment, it is provided that whenever there is a change in the output at which the burner 2 is operated, the control parameters are determined anew, ie a new calibration is carried out.

A method for calibration - and thus, for example, as part of the method for monitoring the burner or for controlling the combustion process - is that the air-fuel mixture is leaned and that a local minimum of the ionization signal between the ionization electrode and the heat exchanger is sought as an example of a surrounding counter-electrode. The minimum is then used for calibration so that the combustion behavior of the burner can finally be monitored or the combustion process can be regulated using the calibration data. A big advantage is that the calibration is carried out in the lean range.

Alternatively, starting from the minimum, a target value is calculated which—in particular as a function of the output or the surface load of the burner—is higher by a previously specified value and is then used as a controlled variable.

In the figure 5 shows the course of the ionization voltages measured across the two ionization electrodes 4, 4' for the case in which only the heat exchanger 3 as the counter-electrode to the respective ionization electrode 4, 4' is electrically connected to ground and galvanically isolated from the burner surface 2'. As in the two previous figures, the negative voltage is plotted on the y-axis and the lambda value increasing from left to right is plotted on the x-axis.

The upper curve belongs to the ionization electrode 4' of FIG 2 , which is closer to the burner surface 2'. There is the known maximum around the area with lambda = 1 and the decrease towards increasing lambda values.

The course of the lower curve, which was measured with the ionization electrode 4 located centrally between the burner surface 2' and the counter-electrode 3, differs from this. Here, too, there is a maximum at lambda=1. In the lean range, the absolute value of the amplitude of the measured voltage decreases in order to pass a minimum as the extreme in the area indicated by the arrow. After this minimum, the curve rises again, only to fall toward zero—in the area not shown here—with larger lambda values.

Here, too, there is an extremum that can serve to calibrate or determine or correct the control parameters.

Reference List

1

burner arrangement

2

burner

2'

burner surface

3

heat exchanger

4.4'

ionization electrode

5

Air-Fuel Mixture Supply

6

control device

Claims (5)

1. A method of monitoring a burner (2) and/or a burning behavior of a burner (2),

   wherein at least one ionization signal is measured, and

   wherein the measured ionization signal is used for monitoring the burner (2) and/or the burning behavior of the burner (2), and

   wherein the ionization signal is measured between an ionization electrode (4, 4') and a counter-electrode (3) spaced apart from a burner surface (2') of the burner (2),

   wherein for a calibration and/or for a determination of parameters used when monitoring the burner (2), ionization signals are measured during a hyperstoichiometric combustion, characterized in

   that a local extremum of the ionization signal is determined during the hyperstoichiometric combustion in dependence on a lambda value of an air-fuel mixture supplied to the burner (2) and is used for the calibration and/or determination.
2. The method according to claim 1,
   wherein a heat exchanger (3) is used as a counter-electrode.
3. The method according to claim 1 or 2,
   wherein the ionization signal is measured between the ionization electrode (4, 4') and the counter-electrode (3) by electrically connecting the counter-electrode (3) and the burner surface (2') to ground.
4. A burner assembly (1) comprising a burner (2), a heat exchanger (3), at least one ionization electrode (4, 4'), an air-fuel mixture supply unit (5) for the burner (2), and a control device (6),

   wherein the control device (6) is connected to the at least one ionization electrode (4, 4'),

   wherein based on ionization signals measured by means of the at least one ionization electrode (4, 4'), the control device (6) monitors the burner (2) and/or a burning behavior of the burner (2), and

   wherein for monitoring the burner (2) and/or a burning behavior of the burner (2) the control device (6) uses at least one ionization signal measured between the ionization electrode (4, 4') and the heat exchanger (3) as a counter-electrode,

   characterized in

   that for a calibration and/or for a determination of parameters used when monitoring the burner (2), the control device (6) leans the air-fuel mixture supplied to the burner (2) via the air-fuel mixture supply unit (5), and evaluates ionization signals measured by means of the leaned air-fuel mixture, and

   that for the calibration and/or the determination of the parameters the control device (6) determines a local extremum of the ionization signals by means of the leaned air-fuel mixture.
5. The burner assembly (1) according to claim 4,
   wherein the ionization electrode (4, 4') is arranged in an area of plus/minus 20% around a mean distance between a burner surface (2') and the heat exchanger (3).

Images