Method for controlling a burner of a heat generator, burner, heat generator and heating system

Abstract

The invention provides a method for controlling a burner 10a of a heat generator 100, particularly for use in a heating system, during an ignition phase to ignite a burner flame, wherein the burner 10a comprises an ignition electrode 13 configured to ignite an air-fuel mixture that can be introduced into a combustion chamber of the burner 10a, and the method includes generating an electrical ignition voltage at the ignition electrode 13, introducing an air-fuel mixture into the combustion chamber of the burner 10a, detecting a burner flame in the combustion chamber, comprising measuring an electrode current IE present at the ignition electrode 13, and controlling the burner 10a during the ignition phase by adjusting a mixing ratio α of the air-fuel mixture introduced into the combustion chamber, which describes a ratio of fuel quantity to air quantity, depending on a detection result.

Description

Technical area

[0001] The present invention relates to methods for controlling a burner of a heat generator during an ignition phase, burners for use in a heat generator, a heat generator and a heating system with a heat generator. Background of the invention

[0002] Burners for use in heat generators are known from the state of the art, in which an air-fuel mixture is introduced into a combustion chamber and burned in a controlled manner in a burner flame to provide heat energy.

[0003] To start such a combustion process, the burners go through an initial ignition phase in which the air-fuel mixture introduced into the combustion chamber is ignited using an ignition electrode in order to provide a stable burning burner flame at the end of said ignition phase.

[0004] This typically involves detecting the presence of the burner flame to confirm successful ignition and the presence of a stable burner flame at the end of the ignition phase. For this purpose, the burner typically includes an ionization electrode subjected to an electrical voltage. This electrode utilizes an ionization effect to measure an ionization current caused by the presence of the burner flame, thus confirming the presence of a successfully ignited burner flame.

[0005] Successful ignition of the introduced air-fuel mixture depends on various, mostly unknown factors, including the precise geometric dimensions of the burner, which, for example, influence the flow behavior of the introduced air-fuel mixture and are unknown due to the tolerance-related manufacturing of individual burner components. EP 2 116 771 A1 discloses a method for controlling a burner with the features of the preamble of the first claim.

[0006] Likewise, specific properties of the fuel are not exactly known, since it is usually provided by an energy supplier as a mixture of various basic fuels (e.g. various alkanes: methane, ethane, propane, butane, etc.), whereby the corresponding composition ratio is usually unknown, may change under certain circumstances and is not specified exactly by the energy supplier, but only within a certain tolerance range.

[0007] Due to the multitude of unknown factors, the burner cannot be optimally adjusted in advance to ignite the air-fuel mixture introduced into the combustion chamber, which results in an increased risk of an unsuccessful ignition phase of the burner without igniting the burner flame.

[0008] In order to minimize this risk and to ensure successful ignition during the ignition phase at least to the greatest extent possible, the solutions known from the state of the art introduce an air-fuel mixture with a relatively high fuel content during the ignition phase (a so-called rich air-fuel mixture), which inevitably increases the ignitability of the air-fuel mixture.

[0009] Although successful ignition is favored by a rich air-fuel mixture, this is associated with relatively high emission rates of undesirable combustion products, such as soot or carbon monoxide, which not only pollute the environment but also significantly reduce the service life of individual burner components and increase maintenance costs. Summary of the invention

[0010] An object of the present invention is therefore to provide a more efficient way of igniting a burner flame of a burner compared to the prior art.

[0011] To solve this problem, a method according to claim 1 and a burner according to claim 6 are proposed.

[0012] The respective dependent claims relate to preferred embodiments of the method according to the invention, which can be provided individually or in combination. Furthermore, dependent claims relate to a heat generator and a heating system.

[0013] According to a first aspect of the invention, a method is provided for controlling a burner of a heat generator, in particular for use in a heating system, during an ignition phase for igniting a burner flame, wherein the burner comprises an ignition electrode configured to ignite an air-fuel mixture, in particular an air-gas mixture, that can be introduced into a combustion chamber of the burner.The method comprises generating an electrical ignition voltage at the ignition electrode, introducing an air-fuel mixture, in particular an air-gas mixture, into the combustion chamber of the burner, detecting a burner flame in the combustion chamber, comprising measuring an electrode current present at the ignition electrode and controlling the burner during the ignition phase by adjusting a mixing ratio of the air-fuel mixture introduced into the combustion chamber, which describes a ratio of fuel quantity to air quantity, depending on a detection result.

[0014] The ignition phase is an operating phase of the burner with a predetermined duration during which the burner is controlled via the electrical voltage generated at and applied to the ignition electrode, subject to successful ignition of the burner flame. Successful ignition, i.e. a successfully completed ignition phase, means that at the end of the ignition phase there is a stable burner flame in the combustion chamber of the burner which does not go out or break off as a result of deviations or malfunctions in the burner.

[0015] The ignition voltage is generated or applied to the ignition electrode by a voltage generator in such a way that electrical ignition sparks occur between the ignition electrode and its counterpart, which is also arranged on the burner - usually a part of a flame body of the burner or a separately arranged ground electrode - which correspond to an electrical current flowing in plasma channels between the ignition electrode and its counterpart, which in principle enables ignition of the introduced air-fuel mixture.

[0016] In the method according to the invention, the detection of the burner flame, i.e., the detection of the presence of the burner flame in the combustion chamber, is advantageously carried out based on the measured electrode current at the ignition electrode. This requires only one electrode—in the case of the invention, the ignition electrode—which is used both for igniting the air-fuel mixture through the generated ignition voltage and for detecting the presence of the burner flame in the combustion chamber.

[0017] The method according to the invention uses the ionization effect of combustion flames, which is basically known from the prior art, to detect the burner flame, which describes a conductivity and a rectifying effect of combustion flames

[0018] If the air-fuel mixture is ignited by the ignition sparks during the ignition phase, the burner flame is formed and the aforementioned ionization effect occurs, as a result of which the burner flame acts as a rectifier and thus inhibits the current flow in the plasma channels between the ignition electrode and its counterpart. In other words, an oppositely directed ionization current is formed, which counteracts the current flow in the plasma channels.

[0019] This effect is inevitably recorded when measuring the electrode current present at the ignition electrode and thus allows conclusions to be drawn about the presence of the burner flame in the combustion chamber without having to rely on a separate ionization electrode known from the state of the art (see also Fig. 1A ).

[0020] This advantageously eliminates the need for the ionization electrode, which, for example, reduces manufacturing costs or the space required for the burner. Maintenance and repair work for the burner are also reduced, as there is now at least one less electrode to maintain.

[0021] The invention thus provides a more cost-effective, low-maintenance and space-saving option for igniting a burner (ignition of the burner flame) compared to the prior art, which is controlled according to the described method during the ignition phase.

[0022] Furthermore, in the course of the method according to the invention, the mixing ratio of the introduced air-fuel mixture is adjusted depending on the detection result, which enables a control adapted to the presence of the burner flame and thus particularly efficient control during the ignition phase.

[0023] Thus, in time periods in which no burner flame is detected or has not yet been detected, it may be useful to adjust the mixture ratio in such a way that the ignitability of the air-fuel mixture is increased in order to successfully complete the ignition phase, whereas in time periods in which a burner flame is detected, the mixture ratio is adjusted under the proviso that emission rates of undesirable combustion products, such as soot or carbon monoxide, are reduced or at least not increased.

[0024] In other words, an ignition phase with a comparatively high success rate for successful ignition is made possible while at the same time keeping the emission rate of undesirable combustion products low.

[0025] The mixture ratio serves to describe the quantitative relationship between air and fuel in the air-fuel mixture. Alternatively to the described fuel-to-air mixture ratio, a reciprocal combustion air ratio can also be used, which describes the ratio of air to fuel. In the case of the aforementioned mixture ratio, an increase in the air-fuel ratio is equivalent to a "richening" of the air-fuel mixture, i.e., an increase in the fuel content, whereas a decrease in the air-fuel ratio is equivalent to a "leaning" of the air-fuel mixture, i.e., an increase in the air content in the air-fuel mixture.

[0026] The mixing ratio can be adjusted by changing the amount of fuel while maintaining the amount of air (e.g. by changing the amount of fuel using a control valve), by changing the amount of air while maintaining the amount of fuel (e.g. by changing the volume flow of a provided air flow) or by a combination of the two aforementioned steps.

[0027] The detection result is provided in the form of a detection parameter, in particular in the form of a temporal profile of the detection parameter, which can assume at least a first or a second value, wherein the first value indicates that no burner flame is detected in the combustion chamber, and the second value indicates that a burner flame is detected in the combustion chamber. This provides a comparatively simple description of the detection result, preferably of a binary nature, which distinguishes between the basic cases "burner flame detected" (also referred to as a "positive detection result") and "no burner flame detected" (also referred to as a "negative detection result").

[0028] Preferably, the detection parameter can further assume a plurality of continuously distributed values ​​that describe the probability of the presence of the burner flame in the combustion chamber. This advantageously enables improved control of the burner. In contrast to the case with purely binary information of the detection result, this allows, for example, fine adjustments of the mixture ratio even with minor changes in the value of the detection parameter, so that the system does not only become active in the case of "no burner flame detected," but can already counteract the exemplary case of an increasing probability of the burner flame extinguishing in a timely manner.

[0029] Preferably, the detection of the burner flame in the combustion chamber occurs continuously throughout the entire ignition phase.

[0030] Preferably, the ignition voltage is generated at the ignition electrode over the entire, specified duration of the ignition phase. This ensures that the air-fuel mixture can, in principle, be ignited at any time during the ignition phase.

[0031] In a preferred embodiment, the detection of the burner flame in the combustion chamber, in particular the measurement of the electrode current present at the ignition electrode, takes place while the electrical ignition voltage is generated at the ignition electrode.

[0032] In other words, the burner flame is detected based on the measured electrode current while the ignition voltage leading to the ignition spark is generated or present at the ignition electrode. This can occur only over a portion of the ignition phase or over the entire duration of the ignition phase.

[0033] In this way, at least in a temporal portion of the ignition phase, it is possible to provide a generated ignition spark or a generated sequence of a plurality of successive ignition sparks with simultaneous detection of the burner flame at one and the same electrode, thereby enabling continuous monitoring of the ignition phase with regard to successful ignition of the burner flame at only one electrode and thus more efficient control of the burner during the ignition phase.

[0034] In a preferred embodiment, when adjusting the mixture ratio to control the burner during the ignition phase, a temporal rate of change of the mixture ratio in time ranges of the ignition phase in which no burner flame is detected is greater than a temporal rate of change of the mixture ratio in time ranges of the ignition phase in which the burner flame is detected.

[0035] A temporal rate of change of the mixing ratio is understood to mean any time-related description of a change in the mixing ratio within the specified time ranges. This can be, but is not limited to, an average temporal rate of change in the form of a quotient with a difference between the mixing ratios at the end and beginning of the respective time range as the dividend and a duration of the respective time range as the divisor, or a local temporal rate of change in the form of a time derivative of the mixing ratio.

[0036] In this way, in time periods in which ignition has so far been unsuccessful, a mixture ratio is advantageously increased or the air-fuel mixture is enriched more than in time periods in which the burner flame is detected.

[0037] As a result, the ignitability of the air-fuel mixture is systematically increased by enrichment during phases without a detected burner flame and, at the same time, a particularly clean ignition phase is enabled in which there is no unnecessary increase in the fuel quantity during a detected burner flame, which would lead to an increased emission rate of undesirable combustion products.

[0038] In a preferred embodiment, the mixing ratio of the air-fuel mixture introduced into the combustion chamber for controlling the burner during the ignition phase is adjusted in such a way that the mixing ratio is adjusted according to a first adjustment rule in time ranges of the ignition phase in which no burner flame is detected, i.e. the detection result is negative, and that the mixing ratio is adjusted according to a second adjustment rule in time ranges of the ignition phase in which the burner flame is detected, i.e. the detection result is positive.

[0039] The adaptation rules can be defined explicitly or implicitly and depend on one or more input variables, such as time, a volume flow of the introduced air-fuel mixture, a temperature of the introduced air-fuel mixture, a temperature in or time derivatives of any order of the aforementioned variables.

[0040] In this way, a systematic adjustment of the mixture ratio can be made depending on the presence of the burner flame in order to enable the cleanest possible ignition (low emission rate of undesirable combustion products).

[0041] In a preferred embodiment, according to the first adaptation rule, the mixing ratio is increased monotonically, in particular strictly monotonically, over time, and according to the second adaptation rule, the mixing ratio is kept constant over time.

[0042] In a preferred embodiment, the mixing ratio is adjusted during the control of the burner in such a way that its temporal progression is substantially constant throughout the ignition phase.

[0043] In this way, a continuous continuation of the mixture ratio is made possible, particularly in transitions between time periods with and without a detected burner flame, in such a way that an unnecessarily high enrichment of the air-fuel mixture, for example by a sudden progression, is avoided in order to provide a clean ignition.

[0044] The detection of the burner flame in the combustion chamber further comprises determining an ionization current on the basis of the electrode current measured at the ignition electrode, determining a value of a detection parameter on the basis of the determined ionization current, wherein the detection parameter can assume at least a first or a second value, wherein the first value indicates that no burner flame is detected in the combustion chamber, and the second value indicates that a burner flame is detected in the combustion chamber, and outputting the determined value of the detection parameter as a detection result.

[0045] This extracts the ionization current caused by the burner flame from the measured electrode current, thus providing an isolated current signal as a basis for detecting the burner flame. Preferably, the determination of the ionization current from the measured electrode current takes into account the generated ignition voltage and / or the mixture ratio of the air-fuel mixture in order to increase the accuracy of the determination step. Preferably, the determination of the ionization current also includes numerical signal filtering, during which fluctuations in the measured electrode current caused by interference are filtered out, such that they are not taken into account when determining the ionization current.

[0046] In a preferred embodiment, the value of the detection parameter is determined in such a way that the first value is assigned to the detection parameter if the determined ionization current lies in a first value range, and that the second value is assigned to the detection parameter if the determined ionization current lies in a second value range.

[0047] The value of the detection parameter is determined in an event-based manner, such that the value of the detection parameter switches from the first to the second value if the determined ionization current exceeds a first ionization current limit value, and the value of the detection parameter switches from the second to the first value if the determined ionization current falls below a second ionization current limit value.

[0048] In this way, event-based detection is provided, which prevents unnecessary switching of the detection parameter caused by fluctuations in the ionization current by providing a buffer range between the said limit values.

[0049] The value of the detection parameter is additionally determined on the basis of the measured electrode current and in an event-based manner, such that the value of the detection parameter switches from the first to the second value if the ionization current exceeds a first ionization current limit value or the measured electrode current falls below a first electrode current limit value, and the value of the detection parameter switches from the second to the first value if the ionization current falls below a second ionization current limit value or the measured electrode current exceeds a second electrode current limit value.

[0050] This allows event-based detection to be extended by an additional event size, thereby increasing the accuracy of the value determination of the detection parameter.

[0051] Preferably, the method further comprises adjusting an initial mixture ratio of the air-fuel mixture introduced into the combustion chamber at the beginning of the ignition phase, wherein the initial mixture ratio is adjusted such that it is a lean air-fuel mixture. Lean is understood here to mean that, taking into account a stoichiometric ratio during the combustion of the fuel with the air, there is an excess of air in the air-fuel mixture. This ensures that there is no rich air-fuel mixture at the beginning, the ignition of which would result in comparatively higher emissions of undesirable combustion products.

[0052] In a preferred embodiment, the control of the burner during the ignition phase is additionally carried out by adjusting one or more of the following variables depending on the detection result: a supply rate of the air-fuel mixture introduced into the combustion chamber; a temperature of the air-fuel mixture introduced into the combustion chamber; or a pressure of the air-fuel mixture introduced into the combustion chamber.

[0053] In this way, the method according to the invention advantageously has a large number of possible actuators available, which can be adapted accordingly to control the burner during the ignition phase in order to implement even more complex control processes.

[0054] A further method for controlling a burner of a heat generator, in particular for use in a heating system, during an ignition phase for igniting a burner flame is also provided, wherein the burner comprises at least one ignition electrode configured to ignite an air-fuel mixture, in particular an air-gas mixture, that can be introduced into a combustion chamber of the burner, and an ionization electrode. The method comprises generating an electrical ignition voltage at the ignition electrode, generating an electrical measuring voltage at the ionization electrode, introducing an air-fuel mixture, in particular an air-gas mixture, into the combustion chamber of the burner, detecting a burner flame in the combustion chamber,comprising measuring an ionization current present at the ionization electrode of the burner and controlling the burner during the ignition phase by adjusting a mixture ratio of the air-fuel mixture introduced into the combustion chamber, which mixture ratio describes a ratio of fuel quantity to air quantity, depending on a detection result, such that the mixture ratio is adjusted according to a first adjustment rule in time periods of the ignition phase in which no burner flame is detected, and that the mixture ratio is adjusted according to a second adjustment rule in time periods of the ignition phase in which the burner flame is detected.

[0055] This process enables a systematic adjustment of the mixture ratio, which takes place depending on the presence of the burner flame, in order to enable the cleanest possible ignition with the lowest possible emission rate of undesirable combustion products.

[0056] Thus, in time periods in which no burner flame is detected or no burner flame has yet been detected, it may be appropriate to adjust the mixture ratio according to the first adjustment rule in such a way that the ignition readiness is increased in order to successfully complete the ignition phase, whereas in time periods in which a burner flame has been detected, the mixture ratio is adjusted according to the first adjustment rule in such a way that the emission rate of undesirable combustion products, such as soot or carbon monoxide, is reduced or at least not increased.

[0057] In other words, the process also enables an ignition phase with a comparatively high success rate for successful ignition while at the same time keeping the emission rate of undesirable combustion products low.

[0058] The statements made regarding the features designated by the same terms in the first aspect of the invention also apply analogously to the above method. Furthermore, a majority of the additional features of the preferred embodiments of the method according to the first aspect correspond to the additional features of the preferred embodiments described below according to the second aspect, for which the advantages already described apply analogously and whose repeated description is omitted below.

[0059] In a preferred embodiment, a temporal rate of change of the mixing ratio according to the first adaptation rule is greater than a temporal rate of change of the mixing ratio according to the second adaptation rule.

[0060] In a preferred embodiment, the mixing ratio is increased monotonically, in particular strictly monotonically, over time according to the first adaptation rule, and the mixing ratio is kept constant over time according to the second adaptation rule.

[0061] In a preferred embodiment, the mixing ratio is adjusted such that its temporal progression is substantially constant throughout the ignition phase.

[0062] In a preferred embodiment, the burner is additionally controlled during the ignition phase by adjusting one or more of the following variables depending on the detection result: a supply rate of the air-fuel mixture introduced into the combustion chamber; a temperature of the air-fuel mixture introduced into the combustion chamber; or a pressure of the air-fuel mixture introduced into the combustion chamber.

[0063] Preferably, the detection result is provided in the form of a detection parameter, in particular in the form of a temporal profile of the detection parameter, which can assume at least a first or a second value, wherein the first value indicates that no burner flame is detected in the combustion chamber, and the second value indicates that a burner flame is detected in the combustion chamber.

[0064] Preferably, the detection parameter may further assume a plurality of continuously distributed values ​​that describe a probability of the presence of the burner flame in the combustion chamber.

[0065] Preferably, the value of the detection parameter is determined in such a way that the first value is assigned to the detection parameter if the measured ionization current lies in a first value range, and that the second value is assigned to the detection parameter if the measured ionization current lies in a second value range.

[0066] Preferably, the value of the detection parameter is determined in an event-based manner, such that the value of the detection parameter switches from the first to the second value if the measured ionization current exceeds a first ionization current limit value, and the value of the detection parameter switches from the second to the first value if the measured ionization current falls below a second ionization current limit value.

[0067] According to the invention, a burner designed to carry out the method of the invention is provided according to independent claim 6 for use in a heat generator, in particular in a heat generator of a heating system.

[0068] The burner according to the invention also offers the advantages described in the course of the method according to the invention, in particular the advantage of the increased success rate in the ignition of the burner with a simultaneous low emission rate of undesirable combustion products.

[0069] Preferably, the detection device is configured to detect a burner flame in the combustion chamber during the generation of the electrical ignition voltage at the ignition electrode by the voltage generator, in particular the measuring device is configured to measure the electrode current present at the ignition electrode during the generation of the electrical ignition voltage at the ignition electrode by the voltage generator.

[0070] Preferably, the control device is configured to adjust the mixture ratio during the ignition phase such that a temporal rate of change of the mixture ratio in time ranges of the ignition phase in which no burner flame is detected is greater than a temporal rate of change of the mixture ratio in time ranges of the ignition phase in which the burner flame is detected.

[0071] Preferably, the control device is configured to adapt the mixture ratio during the ignition phase in such a way that the mixture ratio is adapted according to a first adaptation rule in time ranges of the ignition phase in which no burner flame is detected, and that the mixture ratio is adapted according to a second adaptation rule in time ranges of the ignition phase in which the burner flame is detected, and in particular to adapt the mixture ratio continuously throughout the ignition phase.

[0072] Preferably, the detection device comprises a determination device which is configured to determine an ionization current on the basis of the electrode current measured at the ignition electrode by the measuring device and to determine a value of a detection parameter on the basis of this current, wherein the detection parameter can assume at least a first or a second value, wherein the first value indicates that no burner flame is detected in the combustion chamber, and the second value indicates that the burner flame is detected in the combustion chamber, and to output the determined value of the detection parameter to the control device.

[0073] Preferably, the determination device is configured for event-based determination of the detection parameter, in the course of which the value of the detection parameter is switched from the first to the second value if the determined ionization current exceeds a first ionization current limit value, and the value of the detection parameter is switched from the second to the first value if the determined ionization current falls below a second ionization current limit value.

[0074] Preferably, the control device is configured to adjust a feed rate of the air-fuel mixture introduced into the combustion chamber at the introduction device and / or a temperature of the air-fuel mixture introduced into the combustion chamber at a tempering device of the introduction device and / or a pressure of the air-fuel mixture introduced into the combustion chamber, in particular depending on the detection result of the detection device.

[0075] A burner configured to carry out the above-mentioned method is also provided for use in a heat generator, in particular in a heat generator of a heating system. The burner comprises an introduction device configured to mix an air-fuel mixture from air and fuel according to a mixing ratio that describes a ratio of fuel quantity to air quantity in the air-fuel mixture and to introduce this mixture into a combustion chamber of the burner, an ignition electrode configured to ignite the air-fuel mixture introduced into the combustion chamber of the burner, an ionization electrode, a first voltage generator configured to generate an electrical ignition voltage at the ignition electrode, a second voltage generator configured to generate an electrical measuring voltage at the ionization electrode, a detection device,which comprises a measuring device configured to measure an ionization current present at the ionization electrode, wherein the detection device is configured to detect a burner flame in the combustion chamber on the basis of an ionization current measured by the measuring device, a control device for controlling the burner, which is coupled to the introduction device and the detection device and is configured to adapt the mixing ratio of the introduced air-fuel mixture during an ignition phase for igniting the burner flame at the introduction device as a function of a detection result of the detection device such that the mixing ratio is adapted according to a first adaptation rule in time periods of the ignition phase in which no burner flame is detected, and that the mixing ratio in time periods of the ignition phase in which the burner flame is detected,is adjusted in accordance with a second adjustment provision.

[0076] The burner also offers the advantages described in the process according to the second aspect, in particular the advantage of an increased success rate in the ignition of the burner with a simultaneous low emission rate of undesirable combustion products.

[0077] Preferably, the control device is configured to adjust the mixture ratio during the ignition phase such that a temporal rate of change of the mixture ratio in time ranges of the ignition phase in which no burner flame is detected is greater than a temporal rate of change of the mixture ratio in time ranges of the ignition phase in which the burner flame is detected.

[0078] Preferably, the control device is configured to adjust a feed rate of the air-fuel mixture introduced into the combustion chamber at the introduction device and / or a temperature of the air-fuel mixture introduced into the combustion chamber at a tempering device of the introduction device and / or a pressure of the air-fuel mixture introduced into the combustion chamber, in particular depending on the detection result of the detection device.

[0079] Preferably, the detection device is configured for event-based determination of the detection parameter, during which the value of the detection parameter is switched from the first to the second value if the determined ionization current exceeds a first ionization current limit value, and the value of the detection parameter is switched from the second to the first value if the determined ionization current falls below a second ionization current limit value.

[0080] A heat generator for transferring thermal energy to an energy transport medium is provided, which can be used in a heating system, wherein the heat generator comprises at least one burner according to the invention and a heat exchanger coupled to the burner, which is designed to transfer the thermal energy generated by the burner to the energy transport medium.

[0081] Due to the advantageous design with the burner of the invention, a particularly clean ignition can be implemented during an ignition phase of the burner, e.g. after receipt of a heat request at the heat generator, which is expressed, among other things, in an extremely low emission rate of undesirable combustion products, such as soot or carbon monoxide.

[0082] One of the advantages of this is that soot deposits on the heat exchanger coupled to the burner can be greatly reduced, which in turn increases the efficiency of heat exchange or the transfer of thermal energy to the energy transport medium.

[0083] In addition, a second electrode functioning purely as an ionization electrode can be omitted, which in turn reduces the required installation space for the entire heat generator as well as potential maintenance requirements. For example, only one electrode, in this case the ignition electrode, needs to be cleaned during regular maintenance or repair work.

[0084] The heat exchanger is preferably designed as a coiled-tube heat exchanger, in which a pipe through which the energy transport medium flows is arranged spirally around the burner. This allows the thermal energy provided by the burner flame to be transferred to the energy transport medium particularly efficiently without requiring excessive installation space.

[0085] According to the invention, a heating system is provided which comprises at least one heat generator according to the invention

[0086] By using the burner, which enables a particularly clean ignition process with low emission rates of undesirable combustion products, as part of the heat exchanger of the heating system, for example, not only can the resulting emission of emissions into the environment of the heating system be reduced, but the formation of combustion-related contamination, such as soot, can also be significantly reduced, at least during the ignition process of the burner, so that the exhaust gas paths of the heating system are less polluted, which in turn significantly reduces the maintenance effort and the associated maintenance costs.

[0087] Further aspects and their advantages as well as more specific embodiments of the aforementioned aspects and features are described below with the aid of the drawings shown in the attached figures:

[0088] Figure 1A and Figure 1Bshow exemplary time courses of ignition phase-related variables and parameters of the method for controlling a burner according to a preferred embodiment of the invention during a successfully ending ignition phase

[0089] Figure 2A and Figure 2B show exemplary time courses of ignition phase-related variables and parameters of the method for controlling a burner according to a preferred embodiment of the invention during an unsuccessfully ending ignition phase

[0090] Figure 3 shows a flowchart of an embodiment of the method according to the invention.

[0091] Figure 4 shows a flowchart of an embodiment of a method.

[0092] Figure 5A and Figure 5B show schematic sketches of exemplary embodiments of a heat generator with a burner. Only the Figure 5A a burner according to the invention.

[0093] Identical or similar elements in the figures may be designated by the same reference symbols, but sometimes also by different reference symbols.

[0094] It is emphasized that the present invention is in no way limited to the exemplary embodiments described below and their implementation features. The invention further encompasses modifications of the aforementioned exemplary embodiments, in particular those resulting from modifications and / or combinations of individual or multiple features of the described exemplary embodiments within the scope of the independent claims. Detailed character description

[0095] Fig. 1A and Fig. 1B show exemplary time courses of ignition phase-related variables and parameters of the method for controlling a burner according to a preferred embodiment of the invention during a successfully ending ignition phase.

[0096] A successfully completed ignition phase is understood to mean that at the end of the ignition phase there is a stable burner flame in a combustion chamber of the burner, whereby the burner flame is stable if it does not extinguish or break off as a result of deviations occurring within a specified tolerance range, for example in the form of component tolerances, or a fluctuating introduction of an air-fuel mixture.

[0097] The Fig. 1A and Fig. 1B The time courses shown refer to the same exemplary ignition phase and are presented in two separate figures for clarity. The ignition phase begins at time t = t 0 and ends after a fixed duration T.

[0098] Fig. 1Ashows a time course of an effective current of an electrode current IE measured at an ignition electrode of the burner (solid line), a time course of an effective current of an ionization current II determined on the basis of the electrode current IE (dashed line) and a time course of a detection parameter determined therefrom γ (dotted line) as the detection result of detecting the burner flame in the combustion chamber.

[0099] The description of electrical currents by specifying corresponding effective values ​​is known from the state of the art and serves to provide a frequency-independent description of a temporal current intensity curve, in particular when describing an alternating current.

[0100] It is pointed out at this point that the invention is in no way limited to a description of the electrode current IE via a current intensity or an effective current intensity, but can also be done by other quantities, such as an electrical power, an effective electrical power, an equivalent ohmic resistance or the like.

[0101] With the start of the ignition phase at time t=t 0, an air-fuel mixture is introduced into the combustion chamber, which must be successfully ignited during the ignition phase.

[0102] With regard to the desired ignition of the introduced air-fuel mixture, an ignition voltage is generated at an ignition electrode of the burner, preferably at the latest at the start of the ignition phase, in such a way that electrical ignition sparks are formed between the ignition electrode and its counterpart, e.g. a flame body of the burner or a ground electrode, preferably over the entire duration of the ignition phase, and thus an electrical current flowing in a plasma channel is formed between the ignition electrode and its counterpart.

[0103] This is measured as the electrode current IE at the ignition electrode of the burner, which is reflected in the initial increase in the effective current intensity of the electrode current IE from time t = t 0. The signal of the electrode current IE initially exhibits local, high-frequency fluctuations, which can be attributed, for example, to a transient transient response to reach a steady state or to disturbances in the burner at the beginning of the ignition phase.

[0104] If the air-fuel mixture is ignited and a burner flame is formed, this causes the ionization effect described above in combustion flames, as a result of which the burner flame acts as a rectifier and thus inhibits the current flow in the plasma channels between the ignition electrode and its counterpart. In other words, an oppositely directed ionization current II is formed, the effective current intensity of which is also Fig. 1Ais shown.

[0105] The ionization current II counteracts the current flow in the plasma channels, which leads to a drop in the electrode current IE measured at the ignition electrode, as can be seen for example in the time ranges around the times t=t 1 or t=t 3 in Fig. 1A can be observed.

[0106] In other words, the measured electrode current IE is essentially a superposition of the ionization current and a plasma channel current, from which the ionization current II is determined, which can be used to draw conclusions about the presence of a burner flame in the combustion chamber. The limiting case of a vanishing ionization current II describes the absence of a burner flame, whereas an increase in the ionization current II indicates the formation of a burner flame.

[0107] It should be noted that the time courses of the electrode current IE and the resulting ionization current II in Fig. 1A are presented only qualitatively and do not contain any quantitative information regarding the magnitude relationship between the two currents. Likewise, it is not necessarily necessary to explicitly determine the ionization current II to detect the burner flame. The aforementioned ionization effect can, of course, also be observed directly in the electrode current IE, from which conclusions can be drawn about the presence of the burner flame.

[0108] The determination of the ionization current II based on the measured electrode current IE advantageously includes other burner-specific variables such as voltage values ​​of the applied ignition voltage or the mixing ratio of the air-fuel mixture and preferably includes a step of numerical signal filtering, during which fluctuations in the measured electrode current IE caused by disturbances are filtered out in such a way that they are not taken into account when determining the ionization current II. In this way, a disturbance-free time signal is provided for the ionization current II, on the basis of which the detection parameter γ as a detection result to describe the presence of the burner flame in the combustion chamber.

[0109] The detection parameter γIn the embodiment shown, during the detection of the burner flame, the value can assume at least a first value or a second value. Thus, the detection parameter γ In this case, the value "0" is assigned if no burner flame is detected (negative detection result), and the value "1" if a burner flame is detected (positive detection result).

[0110] The value range of the detection parameter γ is by no means limited to the aforementioned discrete values, but can also be continuously distributed. Thus, the values ​​of the detection parameter γ For example, you can also describe a probability of the presence of the burner flame and assume any numerical value in an interval between 0 and 1 or between 0% and 100%.

[0111] The detection parameter γIn the exemplary embodiment shown, it is determined on the basis of the determined ionization current II, taking into account events occurring when a first ionization current limit value I 1 is exceeded or a second ionization current limit value I 2 is undershot.

[0112] When the first ionization current limit value I 1 is exceeded, the detection parameter γ set to "1", whereas when the second ionization current limit I 2 is undershot, the detection parameter γ is set to "0".

[0113] The different selection of the ionization current limit values ​​(I 1 > I 2 ) advantageously prevents minor fluctuations occurring after exceeding or falling below the respective limit value from immediately causing a switching of the detection parameter γ which creates a buffer area to stabilize the temporal course of the detection parameter γis implemented.

[0114] In the following, based on the above physical principles, the sequence of events during the Fig. 1A underlying ignition phase is described in more detail.

[0115] At time t = t 1 , the determined ionization current II exceeds the first ionization current limit value I 1 , as a result of which a burner flame or its presence is detected (y = 1).

[0116] As time t progresses, the electrode current IE increases again due to a drop in the ionization current II, which indicates a break or extinguishment of the burner flame in the combustion chamber, whereby when the second ionization current limit value I 2 is undershot at time t = t 2 the detection parameter γ is set to "0", meaning no burner flame is detected anymore.

[0117] At time t=t 3 , with a simultaneous drop in the electrode current IE, the determined ionization current II again exceeds the first ionization current limit value I 1 , as a result of which the burner flame or its presence is detected ( γ = 1).

[0118] In the further course, the ionization current II stabilizes above the second ionization current limit, which indicates a stable burner flame that persists until the end of the ignition phase at t=t 0 +T.

[0119] With the aim of a successfully ending ignition phase, the burner is controlled during the ignition phase by adjusting a mixture ratio α of the air-fuel mixture introduced into the combustion chamber, which describes a ratio of fuel quantity to air quantity, whereby this is dependent on the detection parameter determined on the basis of the ionization current II γ as the detection result of the burner flame detection from Fig. 1A occurs.

[0120] Fig. 1B shows again the already mentioned Fig. 1A shown temporal course of the detection parameter γ (dashed line), a time profile of the mixture ratio α adjusted as part of the burner control process (solid line), and the time profile of a valve parameter BV (dotted line), which indicates whether a fuel valve is open (BV=1) or closed (BV=0), i.e., whether an air-fuel mixture is introduced into the combustion chamber or only air. The fuel valve is merely a safety valve in addition to a control valve for adjusting the mixture ratio α.

[0121] The mixture ratio α is inversely related to the combustion air ratio commonly used in combustion technology (usually denoted by the symbol λ in the prior art). Starting from the stoichiometric fuel-air ratio, an excess of air is referred to as a "lean" mixture, and an excess of fuel is referred to as a "rich" mixture. In the case of the mixture ratio α, its increase is synonymous with a "richening" of the air-fuel mixture, i.e., an increase in the fuel content, which in turn leads to an increase in the ignitability of the air-fuel mixture.

[0122] According to the preferred embodiment, the mixing ratio α is adjusted depending on the detection parameter y, whereby in the case of a negative detection result (burner flame is not detected, detection parameter γ= 0) the mixing ratio α is adjusted according to a first adjustment rule and in case of a positive detection result (burner flame is detected, detection parameter γ = 1) the mixing ratio α is adjusted according to a second adjustment rule. The mixing ratio α records a continuous time signal with continuous-value transitions between time ranges with different adjustment rules.

[0123] In the Fig. 1B In the curve shown, starting from the leanest stage of the air-fuel mixture with an initial mixture ratio α=α 0 at the beginning of the ignition phase, the mixture ratio is increased linearly over time t according to the first adaptation rule until the time t=t 1 at which a burner flame is detected for the first time.

[0124] When a burner flame is detected or present, there is initially no need to further increase the mixing ratio α and thus the amount of fuel in the air-fuel mixture, which is why the mixing ratio α is kept constant at α=α 1 in the period from t=t 1 to t=t 2 according to the second adaptation rule.

[0125] With the break or extinguishment of the burner flame at time t=t 2 and a corresponding change in the value of the detection parameter γ the mixture ratio α is increased again linearly over time t starting from α=α 1 according to the first adaptation rule, which leads to an increasing enrichment of the air-fuel mixture in order to increase the ignitability of the same.

[0126] As a result, the burner flame is reignited, the presence of which is again detected at time t=t 3 and, as a result, the mixture ratio α is again kept constant at α=α 2 according to the second adaptation rule until the end of the ignition phase at t=t 0 +T.

[0127] Starting from the stable burner flame present at the end of the ignition phase, the mixture ratio can now be further adjusted in subsequent operating phases of the burner in order, for example, to provide a power corresponding to a power request to the burner.

[0128] By systematically enriching the air-fuel mixture according to the described embodiment depending on the detection parameter γ The ignition phase is particularly low in emissions.

[0129] On the one hand, the air-fuel mixture is preferably ignited in a lean state, which significantly reduces the formation of undesirable combustion products such as soot or carbon monoxide.

[0130] On the other hand, if the burner flame goes out during the ignition phase, the enrichment of the air-fuel mixture continues from the constant mixture ratio in order to successfully complete the ignition phase within the specified duration. If successful, this avoids having to repeat the entire ignition phase, which would result in comparatively higher emissions.

[0131] Fig. 2A and Fig. 2B show exemplary time courses of ignition phase-related variables and parameters of the method for controlling a burner according to a preferred embodiment of the second aspect of the invention during an unsuccessfully ending ignition phase, wherein the Fig. 1A and Fig. 1BThe statements made apply analogously.

[0132] In contrast to the successfully ending ignition phase from Fig. 1A and Fig. 1B After the time t=t 3, the burner flame breaks off or goes out again, represented by the switching of the detection parameter at the time t=t 4 γ to the value "0".

[0133] As a result, the mixing ratio α is increased linearly over time starting from α=α 2 from time t=t 4 according to the first adaptation rule, which, however, does not lead to the re-ignition of the burner flame until the end of the ignition phase at t=t 0 +T with a final value of the mixing ratio α=α 3 is reached, the detection parameter retains the value "0".

[0134] Thus ends the Fig. 2A and Fig. 2Bunderlying ignition phase is unsuccessful, whereupon the fuel valve is closed again (BV=0) and no more air-fuel mixture enters the combustion chamber.

[0135] For a second ignition phase following the first unsuccessful ignition phase, the value α 3 of the mixture ratio α present at the end of the first ignition phase at time t = t 0 +T is preferably used as the initial mixture ratio in order to increase the chances of successful ignition in the second ignition phase.

[0136] It should be noted that the said adaptation rules are by no means limited to the functions described here - linear or constant - but any other functional rules can be used, which refer either to the mixing ratio α itself or to a temporal rate of change thereof.

[0137] Fig. 3shows a flowchart of an embodiment of the method for controlling a burner according to the first aspect of the invention.

[0138] In step S1, an electrical ignition voltage is generated at an ignition electrode of the burner with the proviso that electrical ignition sparks are generated for igniting an air-fuel mixture that can be introduced into a combustion chamber.

[0139] In step S2, an air-fuel mixture is introduced into the combustion chamber of the burner with an initial mixture ratio that describes the initial ratio of a fuel quantity to an air quantity of the introduced air-fuel mixture and is preferably selected such that an initially lean air-fuel mixture is present.

[0140] In steps S3a and S3b, a burner flame is detected in the combustion chamber, comprising measuring an electrode current at the ignition electrode in step S3a and, based thereon, determining a value of a detection parameter based on the measured electrode current in step S3b, wherein the detection parameter assumes the value "0" if an ionization current determined on the basis of the measured electrode current lies in a first value range and no burner flame is detected, and the value "1" if the ionization current determined on the basis of the measured electrode current lies in a second value range and the burner flame is detected.

[0141] Depending on the value of the detection parameter from step S3b, either step S4a (if detection parameter=0) follows, in which the mixture ratio is increased to increase the ignitability of the air-fuel mixture, or step S4b (if detection parameter=1) follows, in which the mixture ratio is maintained or kept constant in order not to unnecessarily increase the emission rate of undesirable combustion products by unnecessarily enriching the already ignited air-fuel mixture.

[0142] The sequence of steps S3a to S4b is repeated as often as desired during the ignition phase of the burner, in particular continuously over the entire duration of the ignition phase.

[0143] Fig. 4 shows a flowchart of an embodiment of the method for controlling a burner according to the second aspect of the invention.

[0144] In step S1, an electrical ignition voltage is generated at an ignition electrode of the burner with the proviso that electrical ignition sparks are generated to ignite an air-fuel mixture that can be introduced into a combustion chamber.

[0145] In step S2, an electrical measuring voltage is generated at a separately designed ionization electrode, which is used to detect a burner flame in the combustion chamber.

[0146] In step S3, an air-fuel mixture is introduced into the combustion chamber of the burner with an initial mixture ratio that describes the initial ratio of a fuel quantity to an air quantity of the introduced air-fuel mixture and is preferably selected such that an initially lean air-fuel mixture is present.

[0147] In steps S4a and S4b, a burner flame is detected in the combustion chamber, comprising measuring an ionization current at the ionization electrode in step S4a and, based thereon, determining a value of a detection parameter based on the measured ionization current in step S4b, wherein the detection parameter assumes the value "0" if the measured ionization current lies in a first value range and no burner flame is detected, and the value "1" if the measured ionization current lies in a second value range and the burner flame is detected.

[0148] Depending on the value of the detection parameter from step S4b, either step S5a follows (if detection parameter=0), in which an adjustment of the mixture ratio takes place according to a first adjustment rule (with the aim of increasing the ignitability of the air-fuel mixture), or step S4b (if detection parameter=1), in which an adjustment of the mixture ratio takes place according to a second adjustment rule, which is specified in such a way that an emission rate of undesirable combustion products is at least not unnecessarily increased by an unnecessary enrichment of the already ignited air-fuel mixture.

[0149] The sequence of steps S4a to S5b is repeated as often as desired during the ignition phase of the burner, in particular continuously over the entire duration of the ignition phase.

[0150] Fig. 5Ashows a schematic sketch of an embodiment of a heat generator 100 with a burner 10a according to the third aspect of the invention.

[0151] The heat generator 100 comprises the burner 10a and a tube coil heat exchanger 20 with a spiral tube coil 21 (shown here in cross section), through which an energy transport medium to be heated by a burner flame of the burner 10a is passed.

[0152] The burner 10a comprises an introduction device 11 in which an air-fuel mixture of an air flow with volume flow QL and a fuel flow with volume flow QB is mixed in a mixing ratio α.

[0153] The mixed air-fuel mixture with volume flow Q LB is then introduced by the introduction device 11 via a flame body 12 with a perforated surface into a combustion chamber of the burner 10a.

[0154] To ignite the introduced air-fuel mixture, the burner 10a comprises an ignition electrode 13 connected to a voltage source 14, to which an ignition voltage is generated or applied.

[0155] The burner 10a further comprises a detection device for detecting a burner flame. The detection device comprises a measuring device 15 for measuring an electrode current IE at the ignition electrode 13 and a determination device 16 configured to determine, based on the measured electrode current IE, a value of a detection parameter that indicates whether or not a burner flame is detected. The value of the detection parameter is output to the control device 17 of the burner 10a, which is coupled to the determination device 16.

[0156] The control device 17 is further coupled to the introduction device 11 and, with a view to carrying out the method according to the first aspect of the invention, is designed to adapt the mixing ratio α of the introduced air-fuel mixture during an ignition phase for igniting the burner flame at the introduction device 11 as a function of the value of the detection parameter output as a detection result of the detection device.

[0157] Fig. 5B shows a schematic sketch of an embodiment of a heat generator 100 with a burner 10b not according to the invention.

[0158] The heat generator 100 comprises the burner 10b and a tube coil heat exchanger 20 with a spiral tube coil 21 (shown here in cross section), through which an energy transport medium to be heated by a burner flame of the burner 10b is passed.

[0159] The burner 10b comprises an introduction device 11 in which an air-fuel mixture of an air flow with volume flow QL and a fuel flow with volume flow QB is mixed in a mixing ratio α.

[0160] The mixed air-fuel mixture with volume flow Q LB is then introduced by the introduction device 11 via a flame body 12 with a perforated surface into a combustion chamber of the burner 10b.

[0161] To ignite the introduced air-fuel mixture, the burner 10b comprises an ignition electrode 13 connected to a voltage source 14, to which an ignition voltage is generated or applied.

[0162] The burner further comprises an ionization electrode 13b connected to a second voltage source 14b, to which a measuring voltage is generated or applied in order to enable an ionization current II caused by an existing burner flame.

[0163] The burner 10b further comprises a detection device for detecting a burner flame. The detection device comprises a measuring device 15b for measuring an ionization current II at the ionization electrode 13b and a determination device 16 configured to determine, based on the measured ionization current II, a value of a detection parameter that indicates whether or not a burner flame is detected and can assume at least a first or a second value for this purpose. The value of the detection parameter is output to the control device 17 of the burner 10b, which is coupled to the determination device 16.

[0164] The control device 17 is further coupled to the introduction device 11 and, with a view to carrying out the method according to the second aspect of the invention, is designed to adapt the mixture ratio α of the introduced air-fuel mixture during an ignition phase for igniting the burner flame at the introduction device 11 as a function of the value of the detection parameter output as a detection result of the detection device in such a way that the mixture ratio α is adapted according to a first adaptation rule in time ranges of the ignition phase in which no burner flame is detected (detection parameter has a first value), and that the mixture ratio α is adapted according to a second adaptation rule in time ranges of the ignition phase in which the burner flame is detected (detection parameter has a second value).

[0165] Embodiments of the present invention and their advantages have been described in detail above with reference to the accompanying figures.

[0166] It is emphasized again that the present invention is in no way limited to the above-described embodiments and their features. The invention further encompasses modifications of the aforementioned embodiments, in particular those resulting from modifications and / or combinations of individual or multiple features of the described embodiments within the scope of the independent claims. List of reference symbols

[0167] 10a, 10bBurner 11Introduction device 12Flame body 13Ignition electrode 13bIonization electrode 14Voltage source for ignition voltage 14bVoltage source for measuring voltage 15, 15bMeasuring device 16Determination device 17Control device 20Tubular coil heat exchanger 21Tubular coil 100Heat generator BVValve parameters IE Electrode current II Ionization current I 1 First ionization current limit value I 2 Second ionization current limit value QL Air flow rate QB Fuel flow rate Q LB Air-fuel mixture flow rate γDetection parameter αMixing ratio

Claims

1. Method for controlling a burner (10a) of a heat generator (100), in particular for use in a heating system, during an ignition phase for igniting a burner flame, wherein the burner (10a) comprises an ignition electrode (13) which is configured to ignite an air-fuel mixture which can be introduced into a combustion chamber of the burner (10a), and the method has the following steps: generating an electrical ignition voltage at the ignition electrode (13); introducing an air-fuel mixture into the combustion chamber of the burner (10a); detecting a burner flame in the combustion chamber; and controlling the burner (10a) during the ignition phase by adjusting a mixing ratio (α), which describes a ratio of fuel quantity to air quantity, of the air-fuel mixture which is introduced into the combustion chamber depending on a detection result, characterized in that the detection of the burner flame in the combustion chamber in turn comprises: - measuring an electrode current (IE) which is present at the ignition electrode; - determining an ionization current (II) on the basis of the electrode current (IE) which is measured at the ignition electrode; - determining a value of a detection parameter (γ) on the basis of the determined ionization current (II), wherein the detection parameter (γ) can assume at least a first value or a second value, wherein the first value indicates that no burner flame is detected in the combustion chamber, and the second value indicates that the burner flame is detected in the combustion chamber; wherein a changeover of the value of the detection parameter (γ) from the first value to the second value if the determined ionization current (II) exceeds a first ionization current limit value (I1), and wherein a changeover of the value of the detection parameter (γ) from the second value to the first value if the determined ionization current (II) falls below a second ionization current limit value (I2), wherein the first ionization current limit value (I1) is greater than the second ionization current limit value (I2); and - outputting the determined value of the detection parameter (γ) as a detection result.

2. Method according to Claim 1, characterized in that the detection of the burner flame in the combustion chamber, in particular the measurement of the electrode current (IE) which is present at the ignition electrode (13), takes place during the generation of the electrical ignition voltage at the ignition electrode (13).

3. Method according to Claim 1 or 2, characterized in that during the adjustment of the mixing ratio (α) for controlling the burner (10a) during the ignition phase, a temporal rate of change of the mixing ratio (α) in time ranges of the ignition phase in which no burner flame is detected is greater than a temporal rate of change of the mixing ratio (α) in time ranges of the ignition phase in which the burner flame is detected.

4. Method according to one of the preceding claims, characterized in that the adjustment of the mixing ratio (α) of the air-fuel mixture which is introduced into the combustion chamber for controlling the burner (10a) takes place during the ignition phase in such a way that the mixing ratio (α) in time ranges of the ignition phase in which no burner flame is detected is adjusted according to a first adjustment rule, and the mixing ratio (α) in time ranges of the ignition phase in which the burner flame is detected is adjusted according to a second adjustment rule.

5. Method according to Claim 4, characterized in that according to the first adjustment rule, the mixing ratio (α) is increased over time (t) in a monotonically increasing manner, in particular in a strictly monotonically increasing manner, and according to the second adjustment rule, the mixing ratio (α) is kept constant over time (t).

6. Burner (10a) for use in a heat generator (100), in particular in a heat generator of a heating system, comprising: an introduction device (11) which is configured to mix an air-fuel mixture from air and fuel according to a mixing ratio (α) which describes a ratio of fuel quantity to air quantity in the air-fuel mixture and to introduce this into a combustion chamber of the burner (10a); an ignition electrode (13) which is configured to ignite the air-fuel mixture which is introduced into the combustion chamber of the burner (10a); a voltage generator (14) which is configured to generate an electrical ignition voltage at the ignition electrode (13); a detection device which comprises a measuring device (15) which is configured to measure an electrode current (IE) which is present at the ignition electrode (13), wherein the detection device is configured to detect a burner flame in the combustion chamber on the basis of an electrode current (IE) which is measured by the measuring device; a control device (17) for controlling the burner, which control device is coupled to the introduction device (11) and the detection device and is configured: to determine an ionization current (II) on the basis of the electrode current (IE) which is measured at the ignition electrode; to determine a value of a detection parameter (γ) on the basis of the determined ionization current (II), wherein the detection parameter (γ) can assume at least a first value or a second value, wherein the first value indicates that no burner flame is detected in the combustion chamber, and the second value indicates that the burner flame is detected in the combustion chamber; to change over the value of the detection parameter (γ) from the first value to the second value if the determined ionization current (II) exceeds a first ionization current limit value (I1); to change over the value of the detection parameter (γ) from the second value to the first value if the determined ionization current (II) falls below a second ionization current limit value (I2), wherein the first ionization current limit value (I1) is greater than the second ionization current limit value (I2); to output the determined value of the detection parameter (γ) as a detection result; and to adjust the mixing ratio (α) of the introduced air-fuel mixture during an ignition phase for igniting the burner flame at the introduction device (11) depending on the detection result of the detection device.

7. Heat generator (100) for transferring thermal energy to an energy transport medium, in particular for use in a heating system, at least comprising: a burner (10a; 10b) according to Claim 6; a heat exchanger (20) which is coupled to the burner and which is configured to transfer thermal energy which is generated by the burner to the energy transport medium.

8. Heating system which comprises at least one heat generator (100) according to Claim 7.

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