EP2466204A1 - Regulating device for a burner assembly - Google Patents

Abstract

The control device has actuator that adjusts supply of air and fuel to a burner. An ionization electrode (2) is arranged in flame region. A flame amplifier (3) is arranged to provide ionization signal (4) to adjusting device (5) to control actuators (6,7) in normal operation. The actuators are controlled by adjusting device such that the air supply ratio is set to predefined stoichiometric value.

Description

The invention relates to a control device for a burner system according to the preamble of claim 1.

In order to be able to correct external disturbances such as changes in fuel quality, temperature or pressure fluctuations on the combustion quality, the ratio of air to fuel, the so-called air ratio λ, can be adjusted. An appropriate structure is also referred to as a fuel-air composite. A particularly inexpensive sensor for detecting the air ratio is the ionization electrode. With an applied alternating voltage, an ionization current flows through the electrode and the flame and is regulated to a setpoint value which is predetermined in dependence on the respective output of the burner. With such an arrangement, the air ratio can be controlled, since the ionization current of the air ratio at each power point is dependent.

A control device of the type mentioned is, for example, in EP-B1-0'770'824 described. There, the air ratio is adjusted so that it is above the stoichiometric value of λ = 1, for example, at λ = 1.3. For calibration of the control setpoint, the maximum of the ionization current is determined at λ = 1 and, starting from the maximum, the next setpoint is calculated. During the calculation, the difference between the current ionization current value and the measured maximum is maintained. A good reproducibility of the actuator line is not absolutely necessary in this method, but occurs when driving over λ = 1 briefly a significant CO emission.

EP-B1-0'697'637 shows a method for monitoring the operation of a control system which regularly interrupts normal operation. An error signal is output if test values of the system sensor exceed a predetermined deviation from reference values, with deviation and reference values being determined in a reference cycle. It is also suggested that in this reference cycle, disturbance variables such as air temperature, air pressure and humidity be varied in order to limit the useful operating conditions of the system and to determine from this the maximum deviations as reference values. However, the function monitoring takes into account non-creeping changes in the system within the operating range specified by the reference values. Even a deviation from the operating range defined above the reference values due to faults that falsify the test result itself is not revealed. An automatic correction of the control setpoint is not suggested.

In EP-B1-1'293'727 a calibration in the control mode is described. Starting from a fixed burner output, an actuator which influences the supply quantity of fuel or air as a function of an actuating signal is adjusted in the direction λ = 1 by setting the nominal value of the ionization signal. However, λ = 1 is not passed over. The behavior of the actuator is observed and compared with stored values. This process is carried out one or more times and it is then evaluated whether the burner operation should be switched off, continued unchanged or continued with a corrected Ionisationssollwertkurve. However, the known method requires that the actuator characteristic of the observed actuator accurately must be reproducible and within a narrow tolerance range.

Also from the WO-A1-2009 / 110 '015 a method during a control operation for monitoring a flame is known with which occurring parasitic elements can be detected and compensated. For this purpose, an alternating voltage source is controlled such that it delivers an alternating voltage signal with a greatly differing duty ratio between positive and negative amplitude with different amplitude values, which is applied to the ionization electrode. The document shows that the accuracy of a gas-air composite control can be impaired by a drift of the ionization current signal as a result of deposits on the ionization electrode or the burner or by bending or displacement of the ionization.

The invention has for its object to propose a control device for a burner system, with which a drift of the ionization is corrected easily and reliably, without exceeding predetermined limits of the combustion values.

The object is solved by the features of claim 1.

Accurate modeling based on experimental observations has shown that a test with a targeted change in the air ratio in a region above the stoichiometric value of λ = 1 and with measurement of the ionization signal makes it possible to approximate the set point in a good approximation, even if the air number change is small in itself. This is also the basis of the insight that so in comparison to the large Luftzahlreduzierungen EP-B1-0'770'824 hardly a temperature pulse and hardly contamination of the burner and the ionization by pollutant emissions occurs. Under certain circumstances, these would significantly increase bending or fouling, which in turn would lead to drift. This insight helps to ensure that the accuracy of the test result is unexpectedly high. After a drift of the ionization signal, the setpoint reliably converges to the desired target value when repeating the test, which represents the original, correct air ratio.

In a preferred embodiment of the invention, the air ratio is changed to a value of λ> 1.05, preferably reduced by a value of Δλ <-0.06. It has been shown that in this air range, on the one hand, with little drift, the ionization signal measurement beyond the signal noise is also sufficient to precisely calculate the setpoint. On the other hand, the air range lower limit can be reliably maintained even with much drift, since a drift occurs only creeping and the test is repeated regularly, preferably at the latest after 3000 burner operating hours.

In a preferred embodiment of the invention, in the performance of the test, the position of an actuator, preferably that for the fuel supply, maintained and changed the other of the actuator. The fact that the position of one of the actuators is maintained, the test result is no longer dependent on its manufacturing tolerances.

In a further preferred embodiment, the stored nominal value characteristic curve for the ionization signal is subsequently replaced on the basis of the calculated nominal value and stored data. Optionally, in case of extreme change, the Setpoint characteristic triggered a warning or a lockout and in particular the actuator for the supply of fuel to be closed.

• Figur 1 schematisch eine Brenneranlage mit einer erfindungsgemäßen Regeleinrichtung, welche mit Hilfe eines Ionisationssignals geregelt wird,
• Figur 2 ein elektrisches Schaltbild des Flammenverstärkers in der Regeleinrichtung nach Figur 1 für eine Ionisationsstrommessung,
• Figur 3 ein aus dem Schaltbild nach Figur 2 abgeleitetes elektrisches Gleichstrom-Ersatzschaltbild für eine Ionisationsstrommessung,
• Figur 4 simulierte Ionisationsstromwerte am Ausgang vom Flammenverstärker in der Regeleinrichtung nach Figur 1 als Funktion der Gebläsedrehzahl n und der Luftzahl λ ohne Fehlerwiderstand,
• Figur 5 simulierte Ionisationsstromwerte am Ausgang vom Flammenverstärker in der Regeleinrichtung nach Figur 1 als Funktion der Gebläsedrehzahl n und der Luftzahl λ mit einem Fehlerwiderstand und
• Figur 6 simulierte Ionisationsstromwerte am Ausgang vom Flammenverstärker in der Regeleinrichtung nach Figur 1 als Funktion der Gebläsedrehzahl n und der Luftzahl λ mit einem Fehlerwiderstand aber nach Durchlauf einer Korrekturschleife.

Hereinafter, an embodiment of the invention will be described with reference to the figures. Show it:

• FIG. 1 1 schematically shows a burner system with a control device according to the invention, which is regulated by means of an ionization signal,
• FIG. 2 an electrical circuit diagram of the flame amplifier in the control device according to FIG. 1 for an ionization current measurement,
• FIG. 3 one from the schematic after FIG. 2 derived DC electrical equivalent circuit diagram for ionization current measurement,
• FIG. 4 simulated ionization current values at the output of the flame amplifier in the control device according to FIG. 1 as a function of the fan speed n and the air ratio λ without error resistance,
• FIG. 5 simulated ionization current values at the output of the flame amplifier in the control device according to FIG. 1 as a function of the fan speed n and the air ratio λ with a fault resistance and
• FIG. 6 simulated ionization current values at the output of the flame amplifier in the control device according to FIG. 1 as a function of the fan speed n and the air ratio λ with a fault resistance but after passing through a correction loop.

FIG. 1 schematically shows a burner system with a control device according to the invention, which operates in normal operation as a fuel-air-composite control. An ionization current through a flame (1) generated by a burner is detected by an ionization electrode (2) from a flame amplifier (3). The circuit is closed by the connection of the flame amplifier (3) to the burner mass. The ionization signal (4) processed by the flame amplifier (3) is forwarded to an adjusting device (5), which uses the ionization signal (4) as the input signal for a control in the normal mode. The ionization signal (4) is designed as an analog electrical signal, but can alternatively be implemented as a digital signal or variable of two software module units.

The adjusting device (5) receives an external request signal (11), with which the heat output is specified. In addition, with the request signal (11), the control can be switched on and off. For example, a heat request is generated by a higher-level, not shown here, temperature control loop. Of course, such a performance specification can be generated by another external consumer or can also be specified directly by hand, for example via a potentiometer.

As usual, the request signal (11) is mapped onto one of the two actuators (6, 7) with the aid of data stored in the setting device (5). Preferably, the request signal (11) is mapped to speed setpoints for a fan as the first actuator (6). The speed command values are compared with a speed signal (9) returned by a fan (6). With an integrated in the actuator (5) speed controller is the Fan (6) via a first control signal (8) to the desired delivery rate of the air (12) for the predetermined request signal (11) controlled. Of course, alternatively, the request signal (11) can be mapped directly to the first control signal (8) of the blower (6). Conversely, the mapping of the request signal (11) to a fuel valve as a first, power-carrying actuator (6) is possible.

With the second actuator (7), preferably a fuel valve, the air ratio is tracked via the supply of the fuel (13). This is done by the predetermined request signal (11) is mapped by a function in an ionization setpoint in the control device (5). This setpoint is compared with the ionization signal (4). With the control difference, via a in the adjusting device (5) realized control unit, the air ratio tracking fuel valve (7) regulated. Thus, a change of the ionization signal (4) via a second control signal (10) causes a change in the position of the fuel valve (7) and thus the flow of the amount of fuel (13). The control loop is closed by a change in the amount of fuel causes a change in the ionization by flame (1) and ionization (2) and thus a change in the Ionisationssignals (4) until its actual value is equal to the predetermined setpoint again for the given amount of air.

FIG. 2 shows an electrical diagram of the flame amplifier (3) for a Ionisationsstrommessung. It is appropriate FIG. 3A in EP-A1-2'154'430. In this case, an alternating voltage is applied to the ionization electrode. Due to the rectifying effect of the flame, an ionization current flows in only one direction through the Flame. The size of the ionization current is dependent on the flame resistance of the flame (1) and forms a measure of the air ratio.

The circuit is composed of an AC voltage source (14), a limiting resistor (15), the electrical equivalent for the flame (1) and the ionization electrode (2), shown as a flame substitute circuit (16), and a linear amplifier (17) whose output (18) the ionization signal (4) is output. The output (18) directly supplies the ionization signal (4). Alternatively, it is also possible to connect circuit parts for galvanic decoupling between the output (18) and the adjusting device (5). The AC voltage source (14) is realized in this circuit example by a transformer to which an input AC voltage is applied.

The amplifier (17) measures the ionization current through the flame substitute circuit (16), the connection to the AC voltage source (14) being virtually grounded. The amplifier (17) averages the ionization current and decouples the output (18) from the actual ionization circuit. The average ionization current can be calculated directly from the voltage at the output (18) and the negative feedback resistance of the amplifier (17). The average ionization current corresponds to a quasi-stationary DC value. Quasi-stationary here means that timers in the circuit and by the AC voltage source (14) caused pure AC signals at the output (18) play no role. The signal at the output (18) therefore follows only the much slower changes in the resistance in the flame replacement circuit (16). For the averaged ionization current can thus a simpler abstract Substitute circuit diagram to be obtained in FIG. 3 is shown.

A DC voltage source (19) generates by its DC voltage (U) a DC current (22) through the limiting resistor (15), a flame resistor (20) and a fault resistance (21).

The resistance in the electrical equivalent of the flame substitute circuit (16) can be seen as the resulting resistance of two resistors connected in series, the actual flame resistor (20) under normal operating conditions and a fault resistance (21), which depends on the above deposits on the ionization electrode (2) or the burner is caused. The deposits are formed by deposits on the ionization electrode or the burner, caused in particular by oxidation processes, soot formation in case of unclean oil combustion or by the introduction of dusts via the air supply. In this case, highly insulating coatings can be produced which change the magnitude of the quasi-stationary direct current (22) via an increase in the fault resistance (21).

Described below is a model that has been shown to allow small airflow changes to be sufficient for the test, and even provide better results to reliably recalculate and correct the setpoints. This allows the air ratio to be kept at its target value.

A bending, or displacement, of the ionization electrode (2) is also largely due to the fault resistance (21) in the equivalent circuit of FIG. 3 taken into account, whereby the fault resistance (21) could then also receive a negative value.

Furthermore, non-illustrated parasitic conductive paths in the region of the flame (1) parallel to the actual flame replacement circuit (16) can be included. In the case of permanent presence of such a path, it can be included in the flame resistance (20); in the case of a time-varying parasitic path, it can be included in the error resistance (21) or its effect taken into account.

The DC voltage (U) of the DC voltage source (19) results from the time duration, with which a current caused by the AC voltage source (14) in FIG. 2 Effectively by the flame (1), that is by the flame replacement circuit (16) flows. It is calculated as the mean value from the average voltage over the conducting half-wave and the voltage value equal to 0 over the blocked half-wave. In the sinusoidal AC voltage of the AC voltage source (14) having an amplitude (U ₁ ) is the DC voltage of the DC voltage source (19) U = U1 / π.

The DC current (22) can be determined directly from the voltage at the output (18) and the negative feedback resistance of the amplifier (17). It is available as an ionization signal (4) at the input of the downstream control device (5).

The abstract equivalent circuit diagram in FIG. 3 Of course this is not just for the circuit in FIG. 2 applicable. The equivalent circuit can basically be applied to many systems for flame signal detection, whose output signal for the actuator (5) can be assigned to a quasi-stationary direct current (22), which is caused by the change in the flame resistance.

In this case, a direct current is generated in the electrical circuit for flame signal detection, in the quasi-stationary direct current (22) of the circuit according to FIG. 3 can be displayed. The real flame resistance is reflected in the flame resistance (20) of the equivalent circuit diagram FIG. 3 in which also other circuit elements, for example measuring resistors, are included in the value of the flame resistance (20). Similarly, the fault resistance (21), the limiting resistor (15) and the DC voltage source (19) can be understood as a result of mapping from another circuit.

FIG. 4 shows in a three-dimensional image simulated ionization current values (I) at the output (18) from the flame amplifier (3) as a function of the fan speed (n) and the air ratio (λ). In a defined by the fan speed and the air space (F1) a curve (I1) of the ionization is shown. A stored nominal value characteristic curve (S1) allows the ionization current to be regulated to the specified nominal value for each fan speed (n). Then, assuming a constant air ratio and variable fan speed (n) corresponding to the air number curve (L1) in the n / λ plane over the burner-specific surface (F1), the course of the ionization current curve (I1) in the surface (F1) is obtained the setpoint characteristic (S1) in the n / I plane.

In the FIG. 4 The conditions shown apply under the condition that no drift of the ionization current and thus no fault resistance (21) occurs. In this case, the sum of the limiting resistor (15) and the flame resistor (20) from the known DC voltage (U) can be determined with the aid of a well-qualified reference measuring section DC voltage source (19) and the value of the measured or determined direct current (22) are calculated.

If a drift of the ionization current and consequently a fault resistance (21) occurs, then the in FIG. 5 shown ratios, wherein the area (F2) opposite to in FIG. 4 shown surface (F1) is offset in the example shown approximately the same shape down.

Due to the drift, a different ionization current curve (I2) and thus another air-fuel ratio curve (L2) in the n / λ-plane, according to which the air ratio at different fan speeds and thus at different burner outputs, are obtained for the same setpoint characteristic curve (S1) for the ionization current setpoint values no longer holds its desired, constant value.

A test procedure is used to detect drift. For this purpose, the fuel-air composite control is set to a preferably fixed starting point (A). For this, the fan speed (s) and the resulting air volume flow go to the stored value of the starting point (A). The second control signal (10) to the fuel valve (7) and thus the fuel flow are tracked in the closed loop. The air ratio ends again at its value specified in the setpoint characteristic (S1) and corresponds to the desired value if there is no drift. Preferably, the position of the fuel valve is determined by averaging in a time window.

As a second step in the test, from the controlled, stable state from the starting point (A), the movement to the test point (B) is effected by reducing the speed (n) of the air blower by a stored value, the position of the Fuel valve (7) is kept constant. In this case, the air ratio is reduced by a more or less constant change in air flow rate (Δλ). Now the ionization current is measured by averaging within a time window.

In the third test step explained below, the setpoint value for the ionization current at a comparison point (C) is recalculated with the aid of the measured value at the test point (B).

In an alternative, a transition from test point (B) to comparison point (C) takes place at the previous setpoint, in which the fan speed of the air blower remains unchanged, but the fuel valve is readjusted to the predetermined air ratio according to the ionization flow curve (I1). Preferably, before the release of the control, the fuel valve is controlled to a stored value that already corresponds to the expected position. The air number change (Δλ) between points (B) and (C) is as in FIGS FIGS. 4 and 5 shown, without and with fault resistance (21) almost the same size. However, with the previous setpoint, the ionization current lift (H2) would be in FIG. 5 due to the fault resistance (21) significantly lower than the corresponding Ionisationsstromhub (H1) in FIG. 4 , The Ionisationsstromhub (H2) in response to the Luftzahländerung (Δλ) thus reveals a regulation on a changed air ratio. With the measured Ionisationsstromhub (H2), an improved setpoint can be calculated and the air ratio corrected.

Finally, the drift test ends, in which the normal operation is restored with regulation according to the request signal (11).

The drift test can be performed on one or more test points. If there are several test points, a possible dependence of the fault resistance (21) on the burner output can be recognized and correspondingly taken into account in a correction.

In a setting method for the burner type concerned, the test point (B) is preferably selected such that the ionization current value is stable there, with a large difference between the slopes at test point (B) and comparison point (C) on a function I = f (λ ) at the selected fan speed (s). This achieves a large signal-to-noise ratio. The test point (B) can be selected under these boundary conditions in a wide range along the function I = f (λ). Form and course of the function remain unknown. It is only assumed that the function is monotonically increasing or decreasing in the measuring range of test point (B). Thanks to the calculation methodology for setpoint correction described below, it has been shown that these conditions are typically given when the air ratio changes to λ> 1.05. Advantageously, the air ratio is reduced by at least Δλ <-0.06 from its controlled state. For a specific type of burner in which the air ratio was set at λ = 1.3, an optimum change in the air number of Δλ = -0.15 was found. Alternatively, the air ratio is increased by at least Δλ = +0.08. The choice of this alternative is useful in burners with a correspondingly different gradient at the point B to point C also with a very good convergence and a small number of iteration steps. If the change in the air number is too great, for example by Δλ> +0.5, there is a risk of combustion due to the lower flame temperature Pollutant emissions, or even that the flame (1) goes out.

The in FIG. 4 shown starting point (A) results directly from the set test point (B) by the air ratio is changed by the amount of air by Δλ.

The fan speeds (n) of points (A) and (B) were stored as default values prior to normal operation in the controller. The ionization current value at test point (B) on a system without fault resistance (21) was preferably averaged over several measurements and stored in the setting device (5) for calculating the correction values.

The comparison point (C) results from the choice of the test point (B) with the fan speed of test point (B) on the Ionisationsstromkurve (I1).

For the calculation of the new setpoint value for the purpose of drift correction in the third test step, the fact is used that, independently of the fault resistance (21), the blower speed is changed so that the air ratio changes by a nearly constant Δλ. Due to the small change in the ionization current in the region of the test point (B), the flame resistance (20) can be assumed to be constant in a first approximation. Assuming the same fault resistances (21) at the test point (B) and at the comparison point (C), a corrected target value can be calculated by using the ionization current value determined without fault resistance (21). In addition, the fault resistance (21) can be determined.

By iterative execution of the above-mentioned test with recalculation of the setpoint at the comparison point (C) one quickly converges to a setpoint at the comparison point (C), which no longer changes without changing the fault resistance (21) in further iterations.

FIG. 6 shows the lines obtained after a first test (S2, I3, L3), wherein the fault resistance (21) at the test point (B) and at the comparison point (C) has been assumed to be the same. A corrected setpoint characteristic curve (S2) can be calculated using the fault resistance (21) known from the above-mentioned calculations and a stored nominal value characteristic curve (S1). In the area (F2) of FIG. 6 the ionization current curve (I3) is shown. The air-number curve (L3) in the n / λ-plane after the first test is already relatively close to the in FIG. 4 shown Luftzahlkurve (L1). The ionization current lift (H3) increases to a constant value not equal to (H1). After one or two iterations there is practically no deviation from (L3) to (L1).

If the fault resistances (21) at the comparison point (C) and test point (B) differ significantly, then this must also be taken into account in the correction calculation of the setpoint. This can be done in the form of a correction factor K, which expresses the relationship between fault resistance (21) at the comparison point (C) and test point (B). The correction factor K as the ratio of the fault resistance (21) at the comparison point (C) to the fault resistance (21) at the test point (B) depends on the composition of the coating layer and is generally between 1 and 2.

The fault resistors (21) at the comparison point (C) are then determined from the fault resistance (21) at the test point (B) and the correction factor K and the new setpoint characteristic curve (S2) can be obtained from the setpoint characteristic (S1) at each point as follows.

At test point (B), the fault resistance (21) is calculated from the measured ionization current and its stored value from a same burner system without fault resistance. Using the given setpoint characteristic (S1), the new setpoint is calculated at the comparison point (C) and every other point in the new setpoint characteristic (S2). At several test points (B), at each test point the new setpoint at the comparison point (C) is calculated and the other setpoint characteristic points are determined from the given setpoint characteristic (S1) and the mean value of the two correction values weighted above the fan speed distance. Of course, other calculation methods can be used.

Normally, with an extremely large reduction of a corrected nominal value characteristic (S2) compared to the initial nominal value characteristic (S1), the system shuts off in normal operation, because then the flame resistance (20) can no longer be sufficiently resolved with respect to the fault resistance (21) and positive feedback takes place. Optionally, even with such a large deviation of these nominal value characteristic curves, a warning or a fault shutdown can be generated per se.

The ionization current values at points (B) and (C) were determined for such a burner system without fault resistance (21) in advance in a setting procedure. With the aid of sensors with which the air ratio can be measured directly or indirectly, a nominal value characteristic curve (S1) with the given air ratio for a prototype was created. Thus, the setpoint I _CO for the ionization current for the comparison point (C) is known. In addition, the prototype was the Test point (B) set and the associated ionization current I _BO measured. I _BO and the values of the setpoint characteristic curve (S1) including I _CO were stored in the setting device (5) during operation for later further processing.

In operation, during the successive tests, the ionization current value I _B1 , later I _B2 ... I _{Bn, is} detected at the test point (B), which possibly deviates from I _BO due to a now occurring drift. The detected ionization current values can be averaged over several tests to reduce scattering. The correction of I _BO then takes place with the aid of the averaged measured values.

If a fault resistance (21) now occurs during normal operation, whereby it can assume not only positive values but in principle also negative values, then the measured ionization current value I _{B1 changes} both due to the changed air value and due to the fault resistance (21), this causes a projection of the surface (F1) to the surface (F2), as shown in the

FIGS. 4 and 5 is shown.

berechnet werden, wenn man die Fehlerwiderstände (21) am Testpunkt (B) und Vergleichspunkt (C) als gleich annimmt. Im Test berechnet die Stelleinrichtung (5) gemäß dieser Formel neue Sollwerte. Vorteilhalt ist sie dazu fest in einem Programmablauf auf einem Mikroprozessor vorgegeben. Für die nächste Iteration der Korrektur liegt der Testpunkt (B) schon näher am Zielwert, so dass der Flammenwiderstand (20) mit und ohne Fehlerwiderstand (21) noch besser angenähert ist und sich der Sollwert zu $$\frac{1}{I_{C2}}=\frac{1}{I_{B2}}-\frac{1}{I_{B0}}+\frac{1}{I_{C0}}$$

ergibt. Bei gleich bleibendem Fehlerwiderstand mit der k-ten Iteration konvertiert der neue Sollwertstrom über $$\frac{1}{I_{\mathit{Ck}}}=\frac{1}{I_{\mathit{Bk}}}-\frac{1}{I_{B0}}+\frac{1}{I_{C0}}$$

auf einen konstanten Wert.Due to the smaller slope of the function I = f (λ) at the test point (B) compared to the slope at the comparison point (C), the flame resistance (20) at the test point (B) changes less than that at the comparison point (C). Therefore, in a first approximation, the flame resistance (20) at test point (B) with and without error resistance can be assumed to be the same. According to the equivalent circuit diagram FIG. 3 the corrected ionization current setpoint at the comparison point (C), which in normal operation after the test equals the local ionization current (I _C1 ), too $$\frac{1}{I_{C1}}=\frac{1}{I_{B1}}-\frac{1}{I_{B0}}+\frac{1}{I_{C0}}$$

calculated by taking the error resistances (21) at the test point (B) and the comparison point (C) as equal. In the test, the setting device (5) calculates new setpoints according to this formula. Advantageous, it is fixed in a program sequence on a microprocessor. For the next iteration of the correction, the test point (B) is already closer to the target value, so that the flame resistance (20) with and without error resistance (21) is even closer and the setpoint value increases $$\frac{1}{I_{C2}}=\frac{1}{I_{B2}}-\frac{1}{I_{B0}}+\frac{1}{I_{C0}}$$

results. If the fault resistance remains the same with the kth iteration, the new setpoint current is converted $$\frac{1}{I_{\mathit{ck}}}=\frac{1}{I_{\mathit{Bk}}}-\frac{1}{I_{B0}}+\frac{1}{I_{C0}}$$

to a constant value.

This can be done equivalently for each point of the set point characteristic (S1) by replacing the current value I _CO by the current I _no = f (n) of the setpoint characteristic (S1) and obtaining the value I _nk after the kth iteration $$\frac{1}{I_{\mathit{nk}}}=\frac{1}{I_{\mathit{Bk}}}-\frac{1}{I_{B0}}+\frac{1}{I_{n0}}\mathrm{,}$$

The values of I _nk give the values of the setpoint characteristic (S2) after the kth iteration. Corresponding FIG. 6 After the first test, you get quite good correction values for the setpoint characteristic curve (S2). After the first and second iteration, the final value is practically reached.

If the fault resistance (21) at points (B) and (C) can not be considered equal due to the nature of the lining, the formulas shown above can be adjusted by a factor K between the fault resistances $$\frac{1}{I_{\mathit{nk}}}=K\cdot \left(\frac{1}{I_{\mathit{Bk}}}-\frac{1}{I_{B0}}\right)+\frac{1}{I_{n0}}\mathrm{,}$$

The factor K depends on the nature of the coating and can be determined experimentally in the adjustment process.

If the test is performed at two or more points, for example at high power and low power, the various values of the fault resistances (21) may be weighted in proportion to the fan speed or other existing power value to determine the corrected set point characteristic (S2).

LIST OF REFERENCE NUMBERS

1

flame

2

ionisation

3

flame amplifier

4

ionization

5

setting device

6

First actor

7

Second actor

8th

First control signal

9

Speed signal

10

Second actuating signal

11

request signal

12

air

13

fuel

14

AC voltage source

15

limiting resistor

16

Flame equivalent circuit

17

amplifier

18

output

19

DC voltage source

20

flame resistance

21

fault resistance

22

direct current

U

DC

n

rotation speed

λ

air ratio

I

Ionisationsstromwert

A

starting point

B

test point

C

reference point

F1

area

S1

Setpoint characteristic

I1

Ionisationsstromkurve

L1

Air ratio curve

Δλ

Air speed change

H1

Ionisationsstromhub

F2

area

S2

Setpoint characteristic

I2

Ionisationsstromkurve

L2

Air ratio curve

H2

Ionisationsstromhub

I3

Ionisationsstromkurve

L3

Air ratio curve

H3

Ionisationsstromhub

Claims (10)

Control device for a burner system with at least one burner, actuators with which the supply of fuel and air is set to the burner, and an ionization electrode arranged in the flame region,
wherein the control device is equipped at least with a flame amplifier on the ionization electrode to generate an ionization signal and an adjusting device which provides a first actuator in the control mode and controls a second actuator by means of a corresponding setpoint for the ionization signal,
and wherein the adjusting device carries out a regulating operation in a first test step, controls the actuators in a second test step to a changed feed ratio and thereby detects the ionization signal, and calculates a setpoint value therefrom and from stored data in a third test step,
characterized in that
in the second test step, the adjusting device (5) controls the actuators (6, 7) to a feed ratio that corresponds to an air ratio above the stoichiometric value of λ = 1. Control device according to claim 1, wherein
in the second test step, the adjusting device (5) changes the air ratio to a value of λ> 1.05. Control device according to one of the preceding claims, wherein
in the second test step, the adjusting device (5) reduces the air ratio by a value of Δλ <-0.06 to λ> 1.05. Control device according to one of the preceding claims, wherein
the adjusting device (5) repeats the test after 3000 operating hours at the latest. Control device according to one of the preceding claims, wherein
in the second test step, the adjusting device (5) maintains the position of an actuator (7) and changes the position of the other actuator (6). Control device according to one of the preceding claims, wherein
in the second test step, the adjusting device (5) maintains the position of the second actuator (7) for the supply of fuel (13) and that of the first actuator (6) for the supply of air (12) changed. Control device according to one of the preceding claims, wherein
the adjusting device (5) repeats the first, second and third test steps with different supply of air or fuel. Control device according to one of the preceding claims, wherein
in a fourth test step, the setting device (5) on the basis of at least one calculated setpoint value (I _C11 , I _C21 , ... I _Cn1 ) and stored data replaces the stored setpoint characteristic _curve (S1) for the ionization _signal . Control device according to one of the preceding claims, wherein in a fourth test step, the setting device (5) causes a lockout due to at least one calculated setpoint value (I _C11 , I _{C21 ,} ... I _Cn1 ) and stored data, and in particular the second actuator (7) for the supply of fuel (13). closes. Control device according to one of claims 8 and 9, wherein the stored data at least partially include the detected in a setting process setpoint characteristic for the ionization signal.

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