DE102017204001A1 - Method for setting and controlling a fuel-air ratio in a heating system, and a control unit and a heating system - Google Patents

Abstract

The invention relates to a method (54) for setting and regulating a fuel-air ratio (56) in a heating system (46). It is proposed that the method (54) comprises the following steps: generating (58) a temporary, temporal fluid supply change (60) of a fluid supply parameter (62), • determining (80) a signal maximum (82) one with the temporal fluid supply change ( 60) correlated temporal change of at least one combustion parameter (84), • determining (102) a first burner performance parameter (104), • determining (116) a nominal combustion parameter (130) based on the signal maximum (82) and the first burner performance parameter (104), • controlling the heating system (46) based on the nominal combustion parameter (130), and that the fluid supply change (60) is selected so that a combustion parameter maximum (98) is assumed at least twice during the time change of the at least one combustion parameter (62) in that the temporal change of the at least one combustion parameter (84) is at least one double peak structure (94) having at least a first peak (88), a first valley (90) and a second peak (92). The invention also relates to a control unit (18) which is designed to carry out the method (54) according to the invention and to a heating system (46) with the control unit (18) according to the invention.

Description

The invention relates to a method for adjusting and regulating a fuel-air ratio in a heating system. The invention also relates to a control unit which is designed to carry out the method according to the invention and to a heating system with the control unit according to the invention.

State of the art

In order to ensure optimum combustion, it is necessary in the operation of gas burners to ensure the correct fuel-air ratio. For this purpose, the gas burner is regulated on the basis of a combustion characteristic measured by a sensor, in which this combustion parameter is adjusted to a nominal combustion characteristic. The correct functioning of the sensors used to determine the combustion characteristics must be ensured. Gas burners are known from the prior art, which perform procedures for calibrating the corresponding sensors. As a rule, the nominal combustion parameter is adapted to changing internal and / or external conditions. In such calibration methods, the gas burner is driven largely over its entire power range. This has the disadvantage that pollutants can be expelled intensified during such a calibration. The duration of such a calibration ranges from several seconds to minutes. This has the additional disadvantage that during this time the gas burner is not available for normal operation.

Disclosure of the invention

advantages

• • Erzeugen einer vorübergehenden, zeitlichen Fluidzufuhränderung einer Fluidzufuhrkenngröße,
• • Ermitteln eines Signalmaximums einer mit der zeitlichen Fluidzufuhränderung korrelierten zeitlichen Änderung von mindestens einer Verbrennungskenngröße,
• • Ermitteln eines ersten Brennerleistungsparameters,
• • Ermitteln einer Sollverbrennungskenngröße auf Basis des Signalmaximums und des ersten Brennerleistungsparameters,
• • Regeln des Heizsystems auf Basis der Sollverbrennungskenngröße,

und ist dadurch gekennzeichnet, dass die Fluidzufuhränderung so gewählt ist, dass bei der zeitlichen Änderung von der mindestens einen Verbrennungskenngröße ein Verbrennungskenngrößenmaximum mindestens zwei Mal angenommen wird bzw. dass die zeitlichen Änderung von der mindestens einer Verbrennungskenngröße zumindest eine Doppelpeakstruktur aufweist, welche zumindest einen ersten Peak, eine erste Senke und einen zweiten Peak aufweist.The present invention provides a method for adjusting and controlling a fuel-air ratio in a heating system. The method comprises the following steps:

• Generating a temporary, temporal fluid supply change of a fluid supply parameter,
• Determining a signal maximum of a temporal change of at least one combustion parameter correlated with the temporal change in fluid supply,
• Determining a first burner performance parameter,
• Determining a target combustion parameter based on the signal maximum and the first burner performance parameter,
• • control of the heating system based on the nominal combustion parameter,

and is characterized in that the fluid supply change is selected such that when the time change of the at least one combustion parameter, a combustion parameter maximum is assumed at least twice or that the temporal change of the at least one combustion parameter has at least one double peak structure, which at least one first peak , a first drain and a second peak.

With the aid of the method, the nominal combustion characteristic can be determined during ongoing, regular operation of the heating system. The method is only a brief intervention in the control of the heating system, in which only small fluid supply changes are made compared to possible total fluid supply changes in the operation of the heating system. In this way, the heating system is always operated with a planned, optimized fuel-air ratio. The fuel-air ratio is also referred to as lambda value. Thus, an intended performance of the heating system is generated with a minimum pollutant emissions. In addition, eliminating the need to drive special calibration cycles for setting the target combustion characteristic. This has the advantage that no further emissions occur and the heating system can always operate in a regular mode, so that it is always available in its entirety.

Due to the fact that the change in the fluid supply is chosen so that the combustion parameter maximum is assumed to be at least twice during the temporal change of the at least one combustion parameter or the temporal change of at least one combustion parameter has at least one double peak structure, the signal maximum is detected particularly reliably. This allows a particularly precise determination of the nominal combustion characteristic.

Here, "heating system" means at least one device for generating heat energy, in particular a heater or heating burner, in particular for use in a building heating and / or hot water generation, preferably by the combustion of a gaseous or liquid fuel. A heating system can also consist of several such devices for generating heat energy and other, the heating operation supporting devices, such as hot water and fuel storage.

A "fluid supply parameter" is to be understood in particular to mean a scalar parameter which is in particular provided with at least one fluid, in particular one, in particular a burner unit of the heating system Combustion air flow, a fuel flow and / or a mixture flow, in particular from a combustion air and a fuel is correlated. Advantageously, in particular by a control and / or regulating unit of the heating system, at least on the basis of the fluid supply characteristic to a volume flow and / or a mass flow of the at least one fluid are closed and / or the flow rate and / or the mass flow of the at least one fluid can be determined. An example of a fluid supply parameter is the indication of an opening width of a fuel valve. A "temporary, temporal fluid supply change" is intended to mean a time-limited variation of the fluid supply parameter, so that it deviates from the value of the fluid supply parameter before the start of the fluid supply change. Preferably, the fluid supply parameter is increased or decreased over the period of fluid supply change. Preferably, the fluid supply parameter is first monotonously increased and then monotonically reduced, or first monotonously reduced and then increased monotonously. The duration of the fluid supply change is preferably pulse-like and / or short compared to the time variations of the fluid supply characteristic provided in the normal operation of the heating system.

In this case, a "pulse", a "pulse-like change" or a "pulse-shaped signal" is understood to be a time profile of a parameter which is brought from a first value within a limited time period to at least one second value different from the first value. A "pulse" is sometimes referred to as "pulse", especially in electrical engineering.

A "combustion characteristic" should be understood in particular to be a scalar parameter, which is correlated in particular with the combustion, in particular of the mixture, in particular of the combustion air and the fuel. An example of a combustion characteristic is an ionization current which is measured at a flame of the heating system. Advantageously, in particular by the control and / or regulating unit of the heating system, at least on the basis of the combustion characteristic to a presence and / or quality of the combustion are concluded and / or the presence and / or the quality of the combustion can be determined. Advantageously, on the basis of the combustion parameter, at least in partial intervals and at least in certain operating states of the heating system, a measure of the quality of the combustion can be unambiguously assigned. An example of a measure of the quality of the combustion is the fuel-air ratio. Advantageously, the combustion parameter corresponds to at least one or exactly one measured value representing the combustion, such as a combustion signal, in particular a light intensity, a pollutant emission, a temperature and / or advantageously an ionization signal, or the combustion parameter can be clearly assigned to such a measured value ,

A "maximum signal" is to be understood as meaning the maximum amplitude of the combustion parameter in a time period correlated with the temporal change of the fluid supply parameter. A signal maximum may in particular be the maximum amplitude of a pulse of the combustion characteristic. A "combustion parameter maximum" is intended to mean a maximum possible value of the combustion parameter with a constant burner performance parameter in at least certain operating states of the heating system. Advantageously, the combustion parameter maximum can be clearly assigned to a well-determined value of the fuel-air ratio. A combustion parameter maximum is a maximum possible value of the combustion parameter with a constant burner performance parameter.

The term "double peak structure" is understood to mean a chronological progression of the combustion parameter in a time period correlated with the time change of the fluid supply parameter, which has at least two maxima, optionally with substantially the same amplitude. The first two maxima of the double peak structure are referred to as "first peak" and "second peak", the intermediate minimum as "first valley". If the temporal change of the at least one combustion parameter has a double peak structure, this is an indication that the signal maximum corresponds to the combustion parameter maximum.

By "determining" a signal maximum of a temporal change of at least one combustion parameter correlated with the temporal fluid change, a method step is to be understood in which a signal maximum of a temporal change correlated with the temporal fluid change is measured or determined by at least one combustion parameter. In this case, methods of data processing or data evaluation can also be provided. Depending on the result or value of the signal maximum, optionally different subsequent steps can be selected in the further course of the method, if necessary and / or desired.

The term "burner performance parameter", a "first burner performance parameter" or a "second burner performance parameter" should in particular be understood to mean a parameter which is correlated with the power, in particular a heating power, of the heating system. Advantageously, in particular by the control and / or regulating unit of the heating system, the power, in particular heating power, of the heating system can be determined at least on the basis of the burner power parameter. Advantageously, the burner performance parameter corresponds to at least one or precisely one measured value which reflects the power or can be unambiguously assigned to such a measured value. Such a measured value may be, for example, a temperature, an air flow rate, a blower control signal or a blower speed or be derived from these measured parameters. The first burner output parameter preferably depends on another measured value which reflects the output than the second burner output parameter or the first burner output parameter is determined using a different method than the second burner output parameter.

By "determining" a first burner performance parameter, a method step is to be understood in which a variable correlated directly or indirectly with a performance is measured or ascertained. In this case, methods of data processing or data evaluation can also be provided. Depending on the result or value of the first burner power parameter, it is optionally possible to select different subsequent steps in the further course of the method if this is necessary and / or desired.

By "nominal combustion parameter" is meant in particular a scalar parameter which describes the desired size of the combustion parameter. If the combustion parameter assumes the value of the nominal combustion parameter, the combustion has the intended properties, in particular with regard to a pollutant emission. Thus, by "rules of the heating system based on the nominal combustion parameter" an operation of the heating system is meant, in which the operating parameters are adjusted so that the combustion parameter largely assumes the value of the nominal combustion parameter.

The term "determination" of a nominal combustion parameter is intended to be understood as a method step in which the desired combustion variable is determined or ascertained as a function of the signal maximum, of the first burner output parameter and optionally of further parameters, in particular operating parameters of the heating system. In particular, methods of data processing or data evaluation may also be provided, in particular using a computing unit.

By "rules of the heating system" is meant the single or repeated, in particular periodic, setting of operating parameters of the heating system, so that the heating system can always fulfill the specified and / or requested performance to the full extent, in particular under changing internal and external conditions, in particular Wear processes and changing boundary and environmental conditions. In this case, "operating parameters" are to be understood as parameters which are used by the control of the heating system for controlling and monitoring processes taking place in the heating system. Examples of "operating parameters" are the fan speed or the fan speed characteristic, a flame ionization characteristic or an opening width of a fuel control valve.

The features listed in the dependent claims advantageous refinements of the method according to the main claim are possible.

If the signal maximum is determined from the first peak and the second peak, this has the advantage that a particularly accurate and reliable determination of the signal maximum is possible. If, for example, the signal maximum is determined as an average value from the first peak and the second peak, temperature-dependent effects on a measuring device of the combustion parameter can be taken into account in this way, for example a temperature-dependent conductivity of an oxidation layer on an ionization probe.

In a further embodiment of the invention, a correction value for correcting the signal maximum, which depends on the first burner power parameter and optionally a second burner power parameter, is taken into account. This has the advantage that the determination of the nominal combustion characteristic is particularly precise. In particular, a power dependency of the nominal combustion characteristic from the signal maximum can be taken into account.

If the nominal combustion parameter is determined by a product formation from the signal maximum with a calibration factor, a particularly simple and reliable method for determining the nominal combustion parameter is realized. In addition, in this way all relevant influences on the combustion are automatically taken into account in the selection of the nominal combustion parameter, which have an influence on the combustion parameter maximum. This saves the need for additional sensors to take account of these influences.

If the calibration factor is determined as a function of the first burner performance parameter and / or of the or a second burner performance parameter, a power dependency of the nominal combustion parameter from the signal maximum can be taken into account.

If the temporal change in fluid supply largely also has the form of a ramp and / or a largely history, it can be ensured with particular reliability that the temporal change of the at least one combustion parameter adopts a combustion parameter maximum at least twice, or if the change in time of the at least one combustion parameter Double peak structure has. In this case, "largely the shape of a ramp" is to be understood as a time profile of the fluid supply parameter, in which the fluid supply parameter initially has a normal value. Subsequently, the fluid supply parameter is increased linearly. Upon reaching a maximum supply value, the fluid supply parameter is rapidly reduced to normal, in particular as quickly as possible. In the case of a "substantially triangular shape", the fluid supply parameter is linearly increased, as in the case of the ramp shape. When the maximum supply value is reached, the fluid supply parameter is reduced linearly until the normal value is reached. In this case, the linear increase of the fluid supply characteristic variable can take place with a substantially same or different speed as the linear reduction of the fluid supply parameter.

If, in an additional step, a temporary temporal additional fluid supply change is produced, this additional fluid supply change being opposite to the fluid supply change, this has the advantage that the additional heating power and the additional emissions caused by the fluid supply change are compensated. In the time average over the fluid supply change and the additional fluid supply change, the fluid supply parameter has the value provided in the control mode.

If the fluid supply parameter corresponds to a control signal for metering a fuel and / or the combustion air and / or a mixture of a fuel and combustion air, in this way no measurement of the fuel and / or the combustion air and / or a mixture of a fuel and combustion air or a flow of these fluids needed. This simplifies the procedure and makes it robust against malfunctions.

If the at least one combustion parameter is determined by an ionization current measurement on a flame of the heating system, this is particularly advantageous because there is a functional relationship between the ionization current at a flame and the fuel-air ratio, which can be evaluated particularly favorably. In particular, the ionization stream has a combustion characteristic maximum, which is at a fuel-air ratio of 1.

In a further embodiment of the invention, the first burner performance parameter is determined from a first time difference between the generation of the fluid supply change and the determination of the temporal change correlated with the fluid supply change from the at least one combustion parameter. The first time difference is a measure of a transit time or a transport speed of a combustion air and / or a mixture of a fuel and combustion air. This embodiment has the advantage that the first time difference can be determined in a particularly simple and cost-effective manner.

If the first burner performance parameter is determined from the double peak structure, in particular from a second time difference between the first peak and the first drain and / or from a third time difference between the first peak and the second peak, this has the advantage that a reliable estimate of a current burner output is possible. The second time difference and the third time difference are shorter in preferred embodiments than the first time difference.

The method is further improved when the second burner performance parameter is or depends on a fan speed. The fan speed can be easily and reliably determined and provides a good estimate of burner performance. In addition, a second burner performance parameter determined in this way allows a check of the first burner performance parameter if it was determined by a different method, for example via a transit time measurement or an analysis of the double peak structure.

If the fluid supply change is selected as a function of the first and / or the second burner performance parameter, this enables the required change of the fluid supply parameter to be precisely adapted so that the combustion parameter can adopt the combustion parameter maximum at least twice or has a double peak structure. In this way, the required fluid supply change can be minimized, so that a quantity of fluid, in particular fuel, is saved and thus the emissions are reduced.

The use of a control unit for a heating system, wherein the control unit is adapted to carry out the method according to the invention for controlling and regulating a fuel-air ratio in a heating system, has the advantage that by operating the heating system with the correct setting of the fuel Air ratio, the durability of the heating system is increased, malfunctions are avoided and thus increased safety.

A heating system with a control unit according to the invention, with a metering device for a fuel and / or combustion air and / or a mixture of a fuel and combustion air, as well as with an ionization probe on a flame and with a blower with variable fan speed has the advantage that in Operation of the heating system is a wrong adjustment of the fuel-air ratio is largely prevented. In this way, unforeseen, heavy loads on the heating system are avoided by, for example, too high burner temperatures and / or excessive fan speeds and / or excessive soot emissions and / or excessive vibration. This allows a cost-effective production of the heating system. In addition, fuel consumption is reduced and the life of the heating system is increased or the time interval between the required inspection intervals is reduced.

If the heating system has at least one metering device for a fuel and / or for combustion air and / or for a mixture of a fuel and combustion air, a temporal change of a fluid supply parameter is thus particularly easy to produce.

In this case, a "dosing device" should be understood as meaning in particular one, in particular electrical and / or electronic, unit, in particular actuator unit, advantageous setting unit, which is provided for the at least one fluid, in particular the combustion air flow, the fuel flow and / or the mixture flow, in particular from the combustion air and the fuel to influence. In particular, the at least one metering device is provided for adjusting, regulating and / or conveying a volume flow and / or a mass flow, in particular the combustion air and / or the fuel. The dosing device for combustion air can advantageously be designed as a fan, in particular having a variable speed, and / or preferably as a fan, in particular a variable-speed fan. The fuel metering device can advantageously be designed as a fuel pump, in particular variable in flow rate, and / or preferably as a fuel valve, in particular variable in flow rate. In particular, the combustion air metering device and / or the fuel metering device are intended to modulate a heating power of the heater device.

If the heating system has an ionization probe on the flame of the heater, this realizes a particularly favorable and reliable sensor for measuring a combustion parameter. Ionization detectors are commonly used in heaters for flame detection.

If the heating system has a blower with variable blower speed, a simple and robust means for setting and determining a heater output can be achieved in this way.

drawings

In the drawings, exemplary embodiments of the method for adjusting and regulating a fuel-air ratio in a heating system according to the present invention, the control unit according to the present invention and the heating system according to the present invention are illustrated and explained in more detail in the following description. Show it

1 a schematic representation of the heating system with the control unit,

2 the method of controlling the heating system,

3 a schematic representation of a fluid supply change and a time change of a combustion parameter,

4 a schematic representation of a dependence of the ionization current on the fuel-air ratio,

5 a schematic representation of a time-burner power function and

6 a schematic representation of a Flammenionisationskennlinie.

description

In the various embodiments, the same parts or steps receive the same reference numbers.

In 1 is a heater 10 shown schematically, in the embodiment on a memory 12 is arranged. The heater 10 has a housing 14 depending on the degree of equipment different components.

The essential components are a heat cell 16 , a control unit 18 , one or more pumps 20 as well as piping 22 , Cables or bus lines 24 and holding means 26 in the heater 10 , The number and complexity of the individual components also depends on the equipment level of the heater 10 from.

The heat cell 16 has a burner 28 , a heat exchanger 30 , a fan 32 , a doser 34 and a Zuluftsystem 36 , an exhaust system 38 and, if the heat cell 16 is in operation, a flame 40 on. In the flame 40 protrudes an ionization probe 42 , The doser 34 is as a fuel valve 44 educated. A blower speed 96 of the blower 32 is variably adjustable. The heater 10 and the memory 12 together form a heating system 46 , The control unit 18 has a data store 48 , a computing unit 50 and a communication interface 52 on. Via the communication interface 52 are the components of the heating system 46 controllable. The communication interface 52 enables data exchange with external devices. External devices are, for example, control devices, thermostats and / or devices with computer functionality, for example smartphones.

1 shows a heating system 46 with a control unit 18 , In alternative embodiments, the control unit is located 18 outside the case 14 of the heater 10 , The external control unit 18 is in special variants as a room controller for the heating system 46 executed. In preferred embodiments, the control unit is 18 mobile. The external control unit 18 has a communication link to the heater 10 and / or other components of the heating system 46 on. The communication connection can be wired and / or wireless, preferably a radio connection, particularly preferably via WLAN, Z-Wave, Bluetooth and / or ZigBee. The control unit 18 may consist of several components in other variants, in particular not physically connected components. In particular variants, at least one or more components of the control unit 18 partially or wholly in the form of software that is executed on internal or external devices, in particular on mobile computing units, such as smartphones and tablets, or servers, in particular a cloud. The communication connections are then corresponding software interfaces.

In 2 is the inventive method 54 to control and regulate a fuel-air ratio 56 in the heating system 46 displayed. In the embodiment is in one step 58 a temporal fluid supply change 60 a fluid supply parameter 62 generated. In the exemplary embodiment, the fluid supply characteristic is 62 a planned opening width 64 of the doser 34 (please refer 3 ). The opening width 64 is a percentage, with an opening width 64 0% of a completely closed fuel valve 44 corresponds and an opening width 64 100% of a fully opened fuel valve 44 describes. In the control unit 18 is a relationship between the opening width 64 and deposited a necessary control signal. The intended opening width 64 is determined by a selection of the control signal and transmission of this control signal to the fuel valve 44 through the control unit 18 realized. The opening width 64 describes a request to the fuel valve 44 is transmitted.

The fluid supply change 60 in the embodiment is in 3 displayed. The first axis of abscissa 66 represents a time. On the first ordinate axis 68 are the fluid supply parameter 62 and an ionization current 86 shown. The fluid supply change 60 runs in a largely ramped pulse. First, the control signal 64 a largely constant normal value 70 , At a first time 72 becomes the control signal 64 increased linearly with a largely constant slope. Once the control signal 64 a maximum feed value 74 reached, the control signal 64 will return to normal as soon as possible 70 lowered. An in 3 shown pulse height 76 is 30%. An in 3 imaged pulse width 78 is 1 s.

In the embodiment, the fluid supply change 60 in step 58 depending on a second burner performance parameter 95 selected. The second burner performance parameter 95 is from the blower speed 96 determined (see 2 ). The blower speed 96 is one of the control unit 18 certain characteristic which determines a blower control signal. The blower control signal is received from the control unit 18 to the blower 32 sent and determines a speed of the blower 32 , In the control unit 18 a blower speed characteristic is stored, which is a fan speed 96 a corresponding second burner performance parameter 95 assigns. The pulse height 76 in the embodiment depends on the fan speed 96 selected. The pulse height 76 increases linearly with the fan speed 96 at. The pulse height 76 in the exemplary embodiment depends on the normal value 70 selected. The pulse height decreases between a minimum fan speed and a maximum fan speed 76 Values in an interval between 5% and 90%. In regular operation of the heating system 46 takes the pulse height 76 Values between 20% and 60%, preferably between 35% and 45%. The pulse width 78 in the embodiment depends on the fan speed 96 selected. The pulse width 78 increases linearly with the fan speed 96 at. Between a minimum fan speed and a maximum fan speed, the pulse width decreases 78 Values in an interval between 10 ms and 5000 ms. In regular operation of the heating system 46 takes the pulse width 78 Values between 50 ms and 2000 ms, preferably between 250 ms and 1000 ms.

In a following step 80 (please refer 2 ) becomes a signal maximum 82 one with the temporal fluid supply change 60 correlated temporal change of a combustion parameter 84 determined. The combustion characteristic 84 is the ionization in the embodiment 86 (please refer 3 ). Of the ionisation 86 is from the ionization probe 42 at the flame 40 determined and to the control unit 18 transmitted. After the fluid supply change 60 indicates the time course of the ionization current 86 a first peak 88 , a first sink 90 and a second peak 92 on. These two local maxima represent a double peak structure 94 represents.

The reason of the double peak structure 94 is the embodiment of the fluid supply change 60 and a relationship between the ionization current 86 and the fuel-air ratio 56 , The fuel-air ratio 56 calculated from an amount of air divided by a quantity of fuel in a mixture of the fuel and the combustion air, which the burner 28 is supplied. 4 illustrates the relationship between the ionization current 86 and the fuel-air ratio 56 at a constant fan speed 96 , On the first ordinate axis 68 is the ionization current 86 applied. On a second axis of abscissa 97 is the fuel-air ratio 56 shown. The course of the ionization current 86 has a combustion characteristics maximum 98 at a fuel-to-air ratio 56 from 1 up. When increasing or decreasing the fuel-air ratio 56 starting from the combustion parameter maximum 98 takes the ionization current 86 from. The heating system is preferred 46 operated with an excess of air, so with a fuel-air ratio 56 greater than 1. Particularly preferred is the heating system 46 with a fuel-to-air ratio 56 between 1.2 and 1.4, preferably 1.3 operated. The procedure 54 Make sure the heating system 46 with a given fuel-air ratio 56 is operated.

Due to the fluid supply change 60 will briefly the fuel-air ratio 56 lowered. Is the fuel-air ratio 56 greater than 1, the fuel-air ratio becomes 56 by increasing the Fluidzufuhrkenngröße 62 to the maximum intake value 74 lowered to a value less than 1. The subsequent lowering of the fluid supply parameter 62 to normal 70 causes an increase in the fuel-air ratio 56 to the original value greater than 1. This way, due to the fluid supply change 60 the fuel-air ratio 56 twice the value 1. The ionization current 86 takes twice the combustion characteristics maximum 98 at. The ionization current 88 points in 3 two local maxima on what the double peak structure 94 represents.

In the in 3 illustrated double peak structure 94 have the first peak 88 and the second peak 92 a different ionization current value. In general, the at least two local maxima of the double peak structure 94 be equal or different in size or have different ionization current values. A reason for different values of the maxima of the double peak structure 94 is the dependence of the combustion parameter maximum 98 of operating parameters and / or further, internal and / or external parameters which occur in the time interval between the occurrence of the first peak 88 and the second peak 92 can change. Examples of operating parameters are, in particular, a flame temperature, fuel quality or fuel burn value. Examples of further, internal and / or external parameters are a flame height or flame geometry, in particular a contact surface between the flame 40 and the ionization probe 42 , Air pressure, or outside temperature. In particular, some of these operating parameters or other parameters may also be indirectly or directly affected by the fluid supply change 60 be changeable, for example, the flame geometry. Another reason for generally different values of the maxima of the double peak structure 94 is that the in 4 illustrated idealized relationship between the fuel-air ratio 56 and the ionization current 86 generally has a hysteresis. Under a hysteresis is to be understood that the ionization current is dependent on a history, so that a current value of the ionization 86 not alone from an actual value of the fuel-air ratio 56 but also from a preceding time course of the value of the fuel-air ratio 56 , This is for example due to temperature-dependent interaction processes between the ionization probe 42 and the flame 40 due. On the ionization probe 42 For example, an oxidation layer may be present which has a temperature-dependent ohmic resistance. In the in 3 illustrated double peak structure 94 becomes the combustion parameter maximum 98 assumed twice, it has in each case a different value of the ionization current.

In step 80 In the embodiment, the double peak structure 94 determined. The control unit 18 Check that by the ionization probe 42 detected and stored ionization current 86 stronger than a signal noise via an ionization current normal value 100 (please refer 3 ) increases. The ionization current standard value 100 is determined in the embodiment, in which the over the duration of the pulse width 78 measured, average ionization current 86 is determined. The control unit 18 checked to determine a double peak structure 94 Whether the stored time history of the change of the combustion parameter 84 due to the fluid supply change 60 has at least two local maxima, which stand out significantly from the signal noise. The value of the ionization current 86 of the two first appearing maxima becomes the first peak 88 or second peak 92 detected. The signal maximum 82 results itself from the arithmetic mean of the first peak 88 and second peak 92 , In alternative embodiments, the signal maximum 82 the first peak 88 and / or the second peak 92 and / or the smaller or larger maximum of the double peak structure 94 correspond. In this way, a characteristic or technical characteristics of a for the detection of the combustion characteristic 84 provided device are taken into account. It is also conceivable that the signal maximum 82 using a function or rule from the first peak 88 and / or the second peak 90 and / or other characteristic points of the double peak structure 94 , for example, the first sink 90 , and / or points one with the temporal fluid supply change 60 correlated temporal change of the combustion parameter 84 is determined. For example, the signal maximum 82 from a weighted arithmetic mean from the first peak 88 and second peak 92 be determined.

In the embodiment, the occurrence of a double peak structure 94 or the reduction of the fuel-air ratio 56 to a value less than 1, in which for every second burner performance parameter 95 through laboratory tests a sufficiently large fluid supply change 60 is selected so that as a result of this fluid supply change 60 In all operating conditions and under largely all environmental conditions always the fuel-air ratios 56 is lowered below 1, in particular at a present fuel-air ratio 56 greater than 1, especially at a present fuel-air ratio 56 greater 1.3. The relationships between the required pulse height 76 or the required pulse width 78 are dependent on the fan speed 96 in the control unit 18 saved.

It is conceivable that the fluid supply change 60 is selected in alternative embodiments depending on at least one operating parameter and / or a measured value, in particular one of the performance of the heating system 46 descriptive parameters. In such embodiments, the relationships established in laboratory tests are between the required fluid delivery change 60 , for example characterized by the pulse height 76 and / or the pulse width 78 as a function of the at least one operating parameter and / or measured value in the control unit 18 saved.

Is a double peak structure 94 can not be determined within a determination time, no signal maximum 82 be determined. The investigation time has the length of one in the control unit 18 deposited, predetermined time threshold. The determination time begins with the fluid supply change 60 or at the first time 72 , In alternative embodiments, the determination time begins with the end of the fluid supply change 60 or with the end of a time delay after the fluid supply change 60 , The size of the investigation time is previously determined in laboratory tests and takes into account a flow time of the fluid from the metering device 34 to the burner 28 , It is conceivable that the investigation time depending on a the performance of the heating system 46 descriptive parameter is determined or selected. Can not signal maximum 82 are determined in the embodiment, the heating system 46 with the help of a flame ionization characteristic 124 regulated (see explanations below and 6 ). It is conceivable that in variants of the procedure 54 the fluid supply change 60 is increased in the next iteration step, if no signal maximum 82 or no double peak structure 94 could be determined.

In one step 102 (please refer 2 ) becomes a first burner performance parameter 104 determined. The control unit 18 determines a second time 106 at which the ionization current 86 the first peak 88 assumes (see 3 ). In the embodiment stores the control unit 18 a time course of the ionization current 86 , A first time difference 108 between the first time 72 and the second time 106 is determined. The thus determined first time difference 108 describes a time interval between generating the fluid supply change 60 and determining the resulting temporal change of the combustion characteristic. The first time difference 108 is a measure of a flow rate of the burner 28 flowing fuel-air mixture. Due to the known and largely constant dimensions of the fuel-air mixture transporting piping 22 is the first time difference 108 a measure of a volume flow of the fuel-air mixture. This is the first time difference 108 a the performance of the heating system 46 descriptive parameter. In the control unit 18 is a time burner power function 110 saved, which is the first time difference 108 the first burner performance parameter 104 assigns. In the exemplary embodiment, the time-burner power function 110 a rational functional rule, based on which the control unit 18 the first burner performance parameter 104 from the first time difference 108 calculated. The time burner power function 110 is determined by laboratory tests. In the exemplary embodiment, the time-burner power function 110 chosen so that the values of the first burner performance parameter 104 in the value range of the second burner parameter 95 lie and correspond to each other. In this way, the first burner performance parameter 104 and the second burner performance parameter 95 In each case one of the burner performance parameters can be used to control or check the other burner performance parameter. 5 shows the time burner power function 110 , A third abscissa 112 represents the first burner performance parameter 104 on a second ordinate axis 114 is the first time difference 108 shown. The first burner performance parameter 104 is the larger, the smaller the first time difference 108 is.

In alternative variants is the time-burner power function 110 as a value table in the control unit 18 saved. Here is a range of values for the first time difference 108 at least divided into intervals and the value table assigns a first burner performance parameter to each of these intervals 104 to. Advantageously, the value range for the first time difference 108 all a largely complete performance range of the heating system 46 depicting first time differences 108 on. In other embodiments, the first time difference becomes 108 between the first time 72 and a third time 118 to which the ionization current 86 the first valley 90 or a fourth time 120 at which the ionization current 86 the second peak 92 or at a time when it is first determined that the ionization current 86 stronger than a signal noise from the normalization ionization value 100 differs. It is also conceivable that the generation of the fluid supply change 60 is described at a time at which the fluid supply parameter 62 the maximum feed value 74 reaches or returns to normal 70 accepts.

In a further step 116 becomes a nominal combustion characteristic 130 based on the signal maximum 82 and on the first burner performance parameter 104 determined (see 2 ). In the embodiment, this is the first in the step 80 that from the double peak structure 94 determined signal maximum 82 corrected. From the first burner performance parameter 104 will be in conjunction with the second burner performance parameter 95 a correction value 122 determined. 6 shows the in the control unit 18 deposited flame ionization characteristic 124 , The flame ionization characteristic 124 describes the relationship between the second burner performance parameter 95 and the ionization current 86 at a given fuel-air ratio 56 , A fourth axis of abscissa 126 shows the second burner performance parameter 95 or the first burner performance parameter 104 , On the first ordinate axis 68 is the ionization current 86 displayed. 6 shows a flame ionization characteristic 124 for a fuel-to-air ratio 56 of 1. The flame ionization characteristic 124 is determined empirically and is in the control unit 18 stored. In the control unit 18 are several flame ionization characteristics 124 for different fuel-air ratios 56 saved. In the exemplary embodiment, the flame ionization characteristics 124 rational functional rules. In the embodiment, the flame ionization characteristics become 124 through the process 54 updated if necessary (see step 134 ).

In step 116 will be a performance difference 128 between the second burner performance parameter 95 and the first burner performance parameter 104 determined. The control unit 18 maps the performance difference 128 the correction value 122 to. This is done using the flame ionization curve 124 for a fuel-to-air ratio 56 1 at the position of the current second burner power parameter 95 the difference in performance 128 a difference in the ionization current 86 associated with the correction value 122 represents. Alternatively, the current second burner performance parameter 95 using the flame ionization characteristic 124 for a fuel-to-air ratio 56 1, a first ionization value and the first burner performance parameter 104 a second Ionisationswert be assigned. The correction value 122 is determined from the difference between the first ionization value and the second ionization value. The signal maximum 82 is corrected by adding the correction value to its value 122 is added. The correction value 122 and / or the power difference may each assume positive or negative values or the value zero. An advantage of the correction value 122 will be explained below.

In the embodiment, the target combustion characteristic 130 as the product of the corrected signal maximum 84 and a calibration factor 132 determined. The calibration factor 132 is one in the control unit 18 stored value between 0 and 1. In the exemplary embodiment, the calibration factor 132 is 0.75. In alternative variants, the calibration factor decreases 132 Values between 0.6 and 0.9. In the exemplary embodiment, the calibration factor 132 an empirically determined constant. The nominal combustion parameter 130 is in the data store 48 the control unit 18 saved.

In a further step 134 becomes the heating system 46 based on in step 116 Determined nominal combustion characteristic 130 regulated. In the embodiment, the heating system 46 using the in the control unit 18 deposited flame ionization characteristic 124 regulated. It becomes a flame ionization characteristic 124 for a fuel-to-air ratio 56 used by 1.3. If necessary, the flame ionization characteristic becomes 124 for a fuel-to-air ratio of 56 1.3 by the in step 116 Determined nominal combustion characteristic 130 updated. For this, the current fan speed 96 using the flame ionization characteristic 124 for a fuel-to-air ratio 56 from 1.3 a value of the ionization current 86 assigned and with the in step 116 Determined nominal combustion characteristic 130 compared. If the relative deviation exceeds a predetermined tolerance, becomes the flame ionization characteristic 124 updated by changing the associated rational function rule. In the exemplary embodiment, this rational functional rule is changed in such a way that the second burner performance parameter 95 associated updated values of the ionization current 86 be multiplied by a correction factor. The correction factor is equal to the target combustion parameter 130 divided by the corresponding value of the ionization current 86 before the update.

In the exemplary embodiment, the fan speed 96 changed and is for this changed second burner performance parameters 95 none in one step 116 Determined nominal combustion characteristic 130 before, then the nominal combustion characteristic becomes 130 from the flame ionization characteristic 124 for a fuel-to-air ratio 56 used by 1.3. Changes the desired fuel-air ratio 56 and is not in one step for this changed operating parameter 116 Determined nominal combustion characteristic 130 before, then the nominal combustion characteristic becomes 130 from the in the control unit 18 stored flame ionization characteristic 124 for the appropriate fuel-air ratio 56 used. In alternative embodiments, regardless of the currently available second burner performance parameter 95 and / or operating parameters last in one step 116 Determined nominal combustion characteristic 130 for the regulation of the heating system 46 used.

In the embodiment, the heating system 46 based on a nominal combustion parameter 130 which is dependent on the second burner performance parameter 95 and the appropriate flame ionization characteristic 124 is determined if a nominal combustion parameter 130 in step 116 can not be determined, for example because in step 80 no signal maximum 82 can be determined.

In step 134 In the exemplary embodiment, the normal value 70 the control signal 64 through the control unit 18 so chosen or to the fuel valve 44 communicates that the ionization current 86 the value of the nominal combustion parameter 130 accepts. For this purpose, a closed loop is used in the embodiment, wherein the ionization current 86 a controlled variable, the control signal 64 a manipulated variable and the nominal combustion characteristic 130 is a leader.

The procedure 54 is repeated in the embodiment. A time interval between the iterations of the procedure 54 depends on the operating status of the heating system 46 and chosen by external conditions. In the exemplary embodiment, the time interval between 2 seconds is 240 seconds, preferably between 10 seconds and 120 seconds, particularly preferably 30 seconds. In variants of the embodiment, the method 54 largely periodically executed. A time interval between the iterations of the procedure 54 is largely constant. In further embodiments, the embodiment of the method 54 triggered by an event, in particular as a function of an operating parameter of the heating system 46 , For example, the method 54 in case of incorrect measurement of the combustion parameter 84 and / or when restarting the heating system 46 and / or in the case of unusual changes of recorded measured values, in particular of combustion-dependent measured values. In preferred variants, the method 54 at least largely once in 24 hours.

In the embodiment, the steps 80 and 102 run as parallel as possible. These can also be executed consecutively in any order. For the procedure 54 plays the order of steps 80 and 102 not matter. In the embodiment is in step 102 the first burner performance parameter 104 depending on the fluid supply change 60 determined. In alternative embodiments, the first burner performance parameter 104 regardless of the Fluidzufuhrkenngröße 60 be determined, for example, by a temperature measurement at the flame 40 and / or by measuring a fuel flow through a mass flow sensor. In these embodiments, the step 102 at any position before the step 116 be executed, in particular before the step 58 ,

It is conceivable that in variants of the embodiment, the flame ionization characteristic 124 (please refer 6 ) the relationship between the first burner performance parameter 95 and the ionization current 86 describes. In these variants, the control of the heating system or the process 54 the performance of the heating system 46 by determining the first burner performance parameter sufficiently frequently 95 certainly. The second burner performance parameter 95 is used for correction, for example about the power difference 128 ,

Furthermore, it is conceivable that in further variants of the embodiment in step 116 to correct the signal maximum 82 the correction value 122 from the performance difference 128 and one in the control unit 18 deposited flame ionization characteristic 124 for a fuel-to-air ratio 56 from 1.3 or for a desired value of the fuel-air ratio 56 is determined. In other embodiments, the correction value is 122 a stored in the control unit, empirically determined constant.

In the embodiment is in step 116 the nominal combustion parameter 130 by a product formation from the signal maximum 82 with the calibration factor 132 determined. In alternative embodiments, the target combustion parameter becomes 130 through the control unit 18 using a functional rule, in particular a rational functional rule, from the signal maximum 82 determined. It is conceivable that this functional specification depends on further operating parameters.

In the exemplary embodiment, the calibration factor 132 one in the control unit 18 stored constant. In alternative embodiments, the calibration factor becomes 132 depending on the first burner performance parameter 104 and / or at the second burner performance parameter 95 determined. In this way, it can be considered that generally the desired fuel-air ratio 56 corresponding ionization current 86 by a power-dependent factor from the signal maximum 82 of the ionization current 86 different. This circumstance is in the exemplary embodiment by the consideration of the correction value 122 considered. In particular variants of these alternative embodiments, the correction value is 122 a constant, especially with the value zero.

In the embodiment, the fluid supply change 60 largely the shape of a ramp. In alternative embodiments, the fluid supply change 60 largely a triangular shape. This has the advantage that the second peak 92 the double peak structure 94 is particularly clear. In other embodiments, the fluid delivery change 60 a substantially rectangular shape and / or largely the shape of a sine and / or largely the shape of a Gaussian curve. These fluid delivery changes 60 are especially suitable for short pulses.

In alternative embodiments, an additional fluid supply change is generated in an additional step. The additional fluid supply change is the fluid supply change 60 largely opposite. In this way, the average fluid supply characteristic corresponds 62 over a period of time which changes the fluid supply 60 and the additional fluid supply change is largely normal 70 , In preferred embodiments, the graph of the time course of the fluid supply parameter is similar 62 the fluid supply change 126 largely at normal value 70 mirrored and temporally shifted graph of the time course of the fluid supply characteristic 62 the fluid supply change 60 , For example, the fluid supply change 60 by a largely ramped pulse with a certain positive pulse height 76 and a specific pulse width 78 realized, the additional fluid supply change by a substantially ramp-shaped pulse with a substantially same pulse width 78 and an additional pulse height selected by the amount of pulse height 76 the first largely ramped pulse of fluid supply change 60 largely corresponds and is negative. This additional step may be at any point in the process 54 In preferred embodiments, the additional step is positioned so that the additional fluid delivery change is that associated with the fluid delivery change 60 correlated change in the combustion characteristic 84 unaffected. The additional step after the step is preferred 58 executed, more preferably after the step 80 ,

In the exemplary embodiment, the fluid supply characteristic is 62 a control signal 64 to the fuel valve 44 , In alternative embodiments, the fluid delivery parameter is 62 one from the control signal 64 derivable scalar value. In further variants, the fluid supply characteristic corresponds 62 a control signal 64 for metering a combustion air and / or a mixture of a fuel and a combustion air. At the same time it contains that through the control unit 18 sent control signal 64 from at least one control command to at least one doser 34 together. The at least one doser 34 is at least one fuel valve 44 and / or at least one fan 32 , In alternative embodiments, a dosage value of the doser becomes 34 measured and as Fluidzufuhrkenngröße 62 used. The term "dosing value" is understood to mean a characteristic value which determines the state of the dosing device 34 describes and the conclusions about through the doser 34 supplied and / or transmitted amount of substance allowed. An example of a dosing value is a measured opening width of the fuel valve 44 and / or a measured fuel flow.

In the exemplary embodiment, the combustion parameter 84 an ionization current 86 , The ionization current 86 is by an ionization current measurement on a flame 40 of the heating system 46 certainly. The ionization current 86 is through the ionization probe 42 determined and to the control unit 18 transmitted. In further embodiments, the combustion characteristic is 84 a light intensity, a spectrum, a lambda value, a pollutant emission and / or a temperature. The light intensity and / or the spectrum at the flame is thereby 40 determined by at least one photodiode. The lambda value is measured with a lambda probe in an exhaust gas. The exhaust system 38 has the lambda probe on. The pollutant emission is determined by a sensor device which is located at the flame 40 and / or in the exhaust system 38 located. The temperature is determined by a contact thermometer and / or a non-contact thermometer, in particular a pyrometer. In this case, the thermometer in the exhaust system 38 located and / or the flame 40 measured.

In the exemplary embodiment, the first burner performance parameter 104 from the first time difference 108 between the first time 72 and the second time 106 determined. In alternative embodiments, the first burner performance parameter becomes 104 from a second time difference 136 between the second time 106 and the third time 118 and / or a third time difference 138 between the second time 106 and the fourth time 120 determined (see 3 ). The second time difference 136 and the third time difference 138 are a measure of a temporal width of the double peak structure 94 , The temporal width of the double peak structure 94 is a measure of a flow rate of the burner 28 flowing fuel-air mixture. This describes the second time difference 136 and the third time difference 138 like the first time difference 108 , the performance of the heating system 46 , It may be the first time difference 108 , the second time difference 136 or the third time difference 138 arbitrarily combined to determine the first burner performance parameter 104 be used. In particular, measurement inaccuracies in the determination of the first time difference can be achieved in this way 108 and / or the second time difference 136 and / or the third time difference 138 be taken into account.

In the exemplary embodiment, the second burner power parameter 95 a blower speed 96 , In alternative embodiments, the second burner performance parameter 95 and / or the first burner performance parameter 104 a measured blower speed and / or a temperature and / or an air flow rate and / or a flow rate of the air-fuel mixture and / or a power of the blower. In this case, the air flow rate or the flow rate of the air-fuel mixture can be determined as a volume flow or as a mass flow. These parameters can also be used in combination. The temperature can be in the exhaust system 38 and / or from the flame 40 be determined. The first burner performance parameter 104 and the second burner performance parameter 95 are each determined by different methods.

In the embodiment, the fluid supply change 60 depending on the second burner performance parameter 95 selected. The pulse height 76 and pulse width 78 each depend linearly on the fan speed 96 from. This will ensure that the heating system 46 by the fluid supply change 60 not too disturbed in its normal operation. In alternative embodiments, the fluid supply change 60 a functional relationship to the second burner performance parameter 95 on. The functional relationship is chosen so that a good detection of the signal maximum 82 taking into account the technical characteristics of the heating system 46 is possible. For example, at certain blower speeds 96 Resonances on which the signal noise of the ionization current 86 zoom in, so is at these blower speeds 96 the fluid supply change 60 elevated. In further embodiments, the fluid supply change is dependent on the second burner performance parameter 95 and / or first burner performance parameters 104 selected. In this way, the fluid supply change 60 more precisely an actual performance of the heating system 46 customized. Optionally, for example, if the step 102 not yet performed, a first burner performance parameter 104 from a previous iteration of the method 54 be used.

Claims (15)

Procedure ( 54 ) for adjusting and regulating a fuel-air ratio ( 56 ) in a heating system ( 46 ), which comprises the following steps: 58 ) a temporary, temporal fluid supply change ( 60 ) a fluid supply parameter ( 62 ), • Determine ( 80 ) of a signal maximum ( 82 ) one with the temporal fluid supply change ( 60 ) correlated temporal change of at least one combustion parameter ( 84 ), • Determine ( 102 ) of a first burner performance parameter ( 104 ), • Determine ( 116 ) a nominal combustion parameter ( 130 ) based on the signal maximum ( 82 ) and the first burner performance parameter ( 104 ), • rules of the heating system ( 46 ) based on the nominal combustion parameter ( 130 ), characterized in that the fluid supply change ( 60 ) is selected so that when the time is changed from the at least one combustion parameter ( 62 ) a combustion parameter maximum ( 98 ) is adopted at least twice or that the change over time of the at least one combustion parameter ( 84 ) at least one double peak structure ( 94 ) which has at least one first peak ( 88 ), a first sink ( 90 ) and a second peak ( 92 ) having. Procedure ( 54 ) according to claim 1, characterized in that the signal maximum ( 82 ) from the first peak ( 88 ) and the second peak ( 92 ) is determined. Procedure ( 54 ) according to one of the preceding claims, characterized in that a correction value ( 122 ) for correcting the signal maximum ( 82 ), which of the first Burner performance parameters ( 104 ) and optionally a second burner performance parameter ( 95 ) depends. Procedure ( 54 ) according to one of the preceding claims, characterized in that the nominal combustion parameter ( 130 ) by product formation from the signal maximum ( 82 ) with a calibration factor ( 132 ) is determined. Procedure ( 54 ) according to claim 4, characterized in that the calibration factor ( 132 ) depending on the first burner performance parameter ( 104 ) and / or from the or a second burner performance parameter ( 95 ) is determined. Procedure ( 54 ) According to one of the preceding claims, characterized in that the temporal change in the fluid supply ( 60 ) has substantially the shape of a ramp and / or largely a triangular shape. Procedure ( 54 ) according to any one of the preceding claims, characterized in that in an additional step, a temporary temporal additional fluid supply change is generated, this additional fluid supply change the fluid supply change ( 60 ) is largely opposite. Procedure ( 54 ) according to one of the preceding claims, characterized in that the fluid supply parameter ( 62 ) a control signal ( 64 ) for metering a fuel and / or the combustion air and / or a mixture of a fuel and combustion air. Procedure ( 54 ) according to one of the preceding claims, characterized in that the at least one combustion parameter ( 84 ) by ionization current measurement on a flame ( 40 ) of the heating system ( 46 ) is determined. Procedure ( 54 ) according to one of the preceding claims, characterized in that the first burner performance parameter ( 104 ) from a first time difference ( 108 ) between generating the fluid supply change ( 60 ) and determining with the fluid supply change ( 60 ) correlated temporal change of the at least one combustion parameter ( 84 ) is determined. Procedure ( 54 ) according to one of the preceding claims, characterized in that the first burner performance parameter ( 104 ) from the double peak structure ( 94 ), in particular from a second time difference ( 136 ) between the first peak ( 88 ) and the first sink ( 90 ) and / or a third time difference ( 138 ) between the first peak ( 88 ) and the second peak ( 92 ). Procedure ( 54 ) according to one of the preceding claims, characterized in that one or the second burner performance parameters ( 95 ) a blower speed ( 96 ) or depends on it. Procedure ( 54 ) according to one of the preceding claims, characterized in that the fluid supply change ( 60 ) depending on the first burner performance parameter ( 104 ) and / or the second burner performance parameter (s) ( 95 ) is selected. Control unit ( 18 ) for a heating system ( 46 ), the control unit ( 18 ) is set up so that a procedure ( 54 ) is executable according to one of the preceding claims. Heating system ( 46 ) with a control unit ( 18 ) according to claim 14, with a doser ( 34 ) for a fuel and / or combustion air and / or for a mixture of a fuel and combustion air, and with an ionization probe ( 42 ) on a flame ( 40 ) and with a blower ( 32 ) with variable blower speed ( 96 ).

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