Method for monitoring the operation of a heating device, heating device, computer program and computer-readable medium

Description

[0001] The present invention relates to a method for monitoring the operation of a heating device, a correspondingly configured heating device, a computer program, and a computer-readable medium.

[0002] The invention lies particularly in the field of controlling a fuel gas-air mixture for a combustion process in a heating device, in particular for hot water preparation or heating a building. To measure the quality of combustion, which depends primarily on the ratio of air to fuel gas during combustion (lambda (λ) value, also known as the air ratio), an ionization measurement is carried out in a flame region, particularly in many heating devices. Such measurements are intended to enable stable control over long periods of time. If the control fails, in most cases the heating device must be switched off, which of course should occur as rarely as possible.

[0003] Flame monitoring can also be carried out in heaters. The main task of this is to ensure that no fuel gas is supplied after the heater has been started if there is no flame. This prevents the formation of a potentially explosive mixture and the escape of unburned fuel gas. This can be achieved in many different ways. There are optical, thermal and electronic systems. A frequently used electronic flame monitor uses an existing ignition electrode, which is otherwise not required after the flame has been ignited, to generate an ionization signal. In the prior art, this signal is not used to control the flame, but rather to monitor it. The specially processed ionization signal can not only indicate the presence of a flame orNot only can they reliably detect extinction, but they can also measure, for example, the physical lifting of the flame from the burner due to excessive combustion air supply at an early stage. This allows for early shutdown in the event of flame instability.

[0004] According to the state of the art, control during operation is often carried out using a separate ionization electrode. Regardless of the type of electrode, the respective actual ionization value in the flame region is determined, which is proportional to the currently existing λ value, so that this can be derived from the ionization measurement. An alternating voltage is applied to the ionization electrode, whereby the flame region, which is ionized in the presence of flames, has a rectifying effect so that an ionization current flows mainly only during one half-wave of the alternating current. This electrical current or a proportional voltage signal derived from it, hereinafter referred to as the ionization signal, is measured and, if necessary, processed as an ionization signal after digitization in an analog / digital converter. In this way, the λ value can be measured and regulated to a setpoint using a control loop.The supply of air and / or fuel gas is varied by suitable actuators until the desired setpoint for λ is reached. Generally, a λ value > 1.0 (1.0 corresponds to a stoichiometric ratio) is aimed for, e.g., a value of λ = 1.3, to ensure that enough air is supplied for clean combustion with essentially no carbon monoxide production. However, λ must remain small enough to ensure stable combustion. Control can be achieved, in particular, via a valve for the supply of fuel gas and / or a fan for the supply of combustion air.

[0005] With such combustion control using a measured ionization signal, it is occasionally or at specified intervals necessary to check the plausibility and / or calibrate the control. For example, EP 3690318 A2 specifies a method whereby the ionization signal can be checked by means of targeted operation or targeted adjustment of the fan and / or fuel gas valve. The method disclosed therein is particularly suitable for switching to a so-called emergency operation control system in the event of undesirable operating conditions. In the event of a malfunction in the primary control system, the system does not have to be shut down, but rather simply switches to the emergency operation system. The method disclosed therein has already proven very successful, but there is still a need for improvement.

[0006] It is possible that the ionization signal has a complex profile, for example, it is not constant or linear over a specific operating or control parameter of the heater. In particular, this signal profile can be designed with locally limited minima, plateaus, or rising and / or falling edges. Especially with such complex signal profiles, there is a risk that sudden events will cause the operating point on this signal profile to jump from one point to another without the control system being able to easily detect this. This is particularly the case if the complex signal profile indicates the same ionization current within the operating range of the control parameter or at different points.A sudden event could be considered, for example, a spontaneous blockage of the combustion air supply, for example, due to a leaf being placed on the intake point, causing the control parameter to jump from one local point in the signal curve to another (possibly distant) point in the signal curve, which may go unnoticed if the ionization current is approximately the same there. Therefore, it is necessary to reliably detect such a jump so that control is always maintained within the correct range.

[0007] Furthermore, especially considering greater control modulation, for example, because the heater is also to be used to provide shower water, very quick, short-term procedures are required to check the current control situation. The current methods, which involve changing the combustion air supply and / or operating the gas valve, may not be fast enough for this or may cause excessive temperature fluctuations in the shower water, thus making it impossible to ensure water comfort for the shower user.

[0008] Furthermore, there is a need to carry out such a verification option with the existing electronics or conventional heating devices (including their control system), so that, for example, the costs of intensive retrofitting can be avoided.

[0009] It is also desirable for the system to automatically detect when a (risky) control situation currently exists, so that it can switch to an emergency run or even an emergency stop without, for example, requiring the intervention of service personnel.

[0010] Based on this, the object of the present invention is to at least partially solve the problems described with reference to the prior art. In particular, a method for monitoring the operation of a heating device is to be provided with which undesirable or risky control situations can be reliably and quickly detected and, if necessary, even eliminated. Furthermore, appropriately configured heating devices are to be provided that operate reliably and can be expanded without requiring significant technical effort.

[0011] These objects are achieved with a method for monitoring the operation of a heating device according to the features and steps of patent claim 1. Further advantageous embodiments and aspects of the invention are specified in the dependent claims. It should be noted that the features and steps listed individually in the claims can be combined with one another in any technologically expedient manner and lead to improvements and embodiments of the invention. The description, particularly in conjunction with the figures, explains the invention and provides additional embodiments.

[0012] A method for monitoring the operation of a heater contributes to this, as explained below. Monitoring is carried out using a measured signal assigned (or assignable) to a flame area of ​​the heater operated with combustion air and fuel gas, with a predeterminable signal profile on which an operating point of the heater can be mapped. Furthermore, the predeterminable signal profile itself is adjustable. This provides for a different signal profile to be set at a predeterminable time, resulting in an evaluation position of the operating point.

[0013] The method is used in particular to monitor or check the control of the operation of the heater. The monitoring method is carried out in particular at a time when flames are actually present in the flame region, i.e. when the provided combustion air and fuel gas have been ignited. The heater can comprise a measuring system, wherein a combustion parameter is recorded in the flame region, the recording of which results in an (electrical) signal with a predeterminable signal curve. This signal is therefore characteristic of the flame region, in particular the combustion occurring there. The measured signal can have a predeterminable signal curve, wherein the currently determined value of the signal is characteristic of the operating point of the combustion or of the heater. The predeterminable signal curve can be determined, for example, using the measuring system orthe measuring arrangement can be adjusted circuit-specifically so that, in particular, a signal curve characteristic of the combustion and / or the heater can be specified. For example, it is possible for the signal curve to cover the operating range via a specifiable operating parameter, such as the λ value, a fan speed, etc. The signal curve can be characterized by edges, plateaus, local minima and / or local maxima. If the operating parameter is varied across this operating range, the operating point moves along this signal curve so that, based on a specifiable flame signal, a current operating parameter of the heater can be deduced. This signal curve is (electronically) adaptable, in particular by shifting the curve, compressing it, or expanding it. For regular operation of the heater, a specifically predefined signal curve is therefore usually predetermined for the control.

[0014] It is now proposed that this electronically preset signal curve is modified or changed at a predetermined point in time or at a point in time automatically initiated due to other events, so that the deviating signal curve is no longer identical to the normally set, predeterminable signal curve. This results in the (ordinary) operating point of the heater now being mapped onto a different, deviating signal curve, with this changed position representing an evaluation position of the operating point. The evaluation position is therefore not a (non-real) operating point of the heater, but rather a position which essentially serves exclusively to check the position of the operating point with the ordinary, predeterminable signal curve. The alienation or change in the signal curve causes, for example, this operating point to move into other regions of the displayed flame signal, with this change orchanged situation then allows conclusions to be drawn about the plausibility or status of the regulation.

[0015] The signal is preferably an ionization signal that can be adjusted via operating parameters of an ionization electrode, and wherein the setting of the deviating signal curve is initiated by a change in the operating parameters. Accordingly, an ionization signal or an ionization current is determined in the flame region and used as the basis for controlling the combustion of the heater. The operating parameters of the ionization electrode are, for example, the type of alternating voltage, the current intensity, the frequency, the amplitude, etc. In other words, this means in particular that in order to (briefly) modify the signal curve, one or at least one of these operating parameters is readjusted, thereby achieving the deviating signal curve at the predetermined time. In this context, it is particularly preferred that at least one operating parameter is an electrical variable of the ionization electrode.

[0016] It is possible to maintain the deviating signal curve for an evaluation period of a maximum of 2.0 seconds and then reset to the preset signal curve. It is particularly preferable to select an even shorter evaluation period, for example, a maximum of 1.0 seconds or even just 0.5 seconds. The timing of the evaluation period must be adapted in particular to the control sensitivity or measurement sensitivity of the heater or measurement system. This means that the operation or control can be checked very quickly and briefly, and that normal control can be resumed quickly. In this respect, the current situation can also be checked relatively frequently without adversely affecting the proper operation of the heater's combustion system.

[0017] Particularly preferably, the supply of combustion air and fuel gas is maintained (constant or unchanged) during the presence of the deviating signal curve. In other words, this means, in particular, that a check of the operation or control can be carried out without changing the (mechanical) control elements, such as the gas valve and / or the fan. Instead, it is possible to identify a (stable) combustion process or a corresponding combustion situation and then briefly maintain the combustion unchanged, whereby the measured value analysis is modified (only electronically).

[0018] In particular, it is possible for an instruction for the continued operation of the heater to be generated or stored from the second evaluation position. This means, for example, that the newly set, deviating signal curve has a contour such that the operating point, based on its position on the (ordinarily) specified signal curve, is brought into an evaluation position that allows a clear evaluation of the current combustion or current operation of the heater. In this respect, a clear command or status report or a similar instruction can be provided based on this clear, electronically generated evaluation position. This instruction can be (tacitly) saved, but it is also possible for corresponding instructions to be transmitted to other systems and / or even provided to the user of the heater.

[0019] It is particularly preferred that the operation of the heater be stopped if the generated evaluation position lies outside a predetermined operating zone. In particular, it is possible for the setting of the deviating signal profile to create imaginary operating zones that signal particularly risky operating states of the heater. If an operating point lies within such a risky range, the shift of the actual operating point toward the imaginary evaluation position leads to a shift of an operating zone that is identified as critical. Therefore, depending on the location of the generated evaluation position, emergency operation and / or an emergency stop can be automatically initiated.

[0020] According to a further aspect, a heating device is proposed, comprising at least one ionization electrode and means configured to carry out the steps of the method proposed here. These means comprise a microcontroller capable of adjusting and / or evaluating the signals or signal waveforms. In particular, means are provided that allow adjustment of the operating parameters of an electrical variable of the ionization electrode.

[0021] According to a further aspect, a computer program is provided which comprises instructions that cause a heating device, at least having an ionization electrode and means suitable for carrying out the steps of the method proposed here, to carry out the steps of the proposed method. According to a further aspect, such a computer program can be stored on a computer-readable medium, for example, a computer.

[0022] The invention and the technical environment are explained in more detail below with reference to the figures. It should be noted that the figures are schematic in nature and are not intended to limit the invention. The elements and features illustrated in the figures may be combined with one another as desired and / or supplemented by facts from the general description, unless explicitly excluded here. They show: Fig. 1: schematically shows a heater with a flame monitor, Fig. 2: a schematic circuit for generating an ionization signal, Fig. 3: a visualization of the process sequence, and Fig. 4: a diagram with exemplary signal curves.

[0023] Fig. 1 shows a schematic illustration of an embodiment of a device having a heater 1. During operation, a flame region 2 forms in the heater 1 for combusting a fuel gas with air. The combustion air 3 enters the heater 1 via an air supply and a fan 22. Fuel gas 4 is mixed with the combustion air 3 via a fuel gas valve 23. An ignition electrode 20 ignites the mixture at the start of the combustion process and is then used, for example, as part of a flame monitor 19. It is possible to use an ionization electrode 9 to measure an ionization signal in the flame region 2, which can be used to regulate the lambda (λ) value during operation of the heater 1. A control unit 18 is then used for this purpose, which controls the fan 22 and / or the fuel gas valve 23 accordingly. A flame monitor 19 ensures that fuel gas 4 is only supplied when a stable flame is detected.For this purpose, an additional ionization electrode 9 (usually the ignition electrode 20) is used to generate another ionization signal, the electronic processing of which is specifically designed for the task of flame monitoring 19. In particular, an AC voltage source 14 is specifically designed for this purpose.

[0024] Fig. 2 shows a schematic of an exemplary circuit such as can be used for flame monitoring 19. An alternating voltage source 14 with a high output resistance 27 initially supplies an alternating voltage with essentially no direct voltage component to the ignition electrode 20 and the counter electrode (burner 21, ground). When a flame appears between the two (shown here as equivalent circuit 28), the voltage between the rectifying effect of the flame (shown as a diode in the equivalent circuit) drops in only one half-wave, so that an alternating voltage with a negative direct voltage component is present at the input of the evaluation electronics 29. This voltage is converted into the desired ionization signal in the evaluation electronics 29 and can be converted in an analog / digital converter 30 and then further processed.This entire arrangement forms a preferred detector for flame monitoring 19, which then delivers an ionization signal when a flame is present, wherein the ionization signal also has a typical curve from which, for example, the incipient physical lifting of the flames from gas outlet openings can be recognized, so that shutdown can also occur in the event of instability due to excessively high gas velocities and / or excessively high λ values.

[0025] An AC voltage source is used, which comprises an AC voltage pulse generator 24, a microcontroller 25, and an adjuster 26. This design creates a cost-effective and space-saving AC voltage source 14, in which an effective amplitude can be adjusted according to the desired sensitivity of the detector. Although an effective amplitude does not have the form of a typical, approximately sinusoidal AC voltage, it leads to the same ionization signals during further processing as a sinusoidal AC voltage with this amplitude. The provision of such an AC voltage source also allows (briefly) the generation and provision of deviating signal waveforms 7 for this ionization signal.

[0026] Fig. 3 schematically illustrates a possible embodiment of the method, wherein here the usual control of the operation of the heater 1 is initially illustrated on the left. At a predetermined point in time (marked there with t 1), for example, the setting on the alternating voltage source 14 can be changed such that a test measurement 15 is carried out. While previously the operation of the heater 1 was monitored by means of the flame monitor 19 and a signal measured in the flame region 2 (in particular an ionization signal) with a predetermined, ordinary signal curve 5, a different signal curve 7 is now set at this point in time. This different signal curve 7 is maintained during the test measurement 15 until a further point in time (marked here with t 2) the alternating voltage source 14 is readjusted again, namely in such a way that it again reaches the predetermined, ordinary signal curve 5.During this verification measurement 15, the settings for the fan 22 and the fuel gas valve 23 were not changed. The (imaginary) image with the evaluation position 8 of the operating point 6 thus generated for the deviating signal curve 7 can be subjected to an evaluation process 16. Based on this evaluation or assessment, it is then possible to determine, as a result of this verification routine 13, whether to return (to the left) to ordinary, regular operation of the heater or (alternatively) to set an emergency operation situation on the right, in which, for example, a decision is made via a stop 17 regarding the operation of the heater 1.

[0027] Fig. 4 illustrates, by way of example, a signal curve during ordinary operation of the heater 1, i.e. the predeterminable signal curve 5, with the real operating point 6 of the heater 1, based on which the control takes place (shown here as a solid line). The ordinate can, for example, represent the signal 11, in particular the ionization signal. The abscissa can represent a relevant operating variable 12 of the heater 1, for example a fan speed, a λ value, etc. The predeterminable signal curve 5 characterizes or spans the usual operating range of this operating variable 12. In the present case, it is characterized from left to right by an initially steeply falling edge, a local minimum, a somewhat longer intermediate plateau, a local minimum, and a steeply rising edge. As an example, the real operating point 6 could lie in the area of ​​the right-hand local minimum (cf. position 6.2).However, it is possible, for example, that a short-term malfunction or a brief interruption of the combustion air supply could suddenly cause the operating point to jump to the other side, namely to a flank of the local minimum (see section 6.1). If the system fails to detect this sudden change, it will regulate in the wrong range, which can lead to significant problems.

[0028] It is therefore now proposed to set a deviating signal curve 7 at a predetermined point in time (shown here in dashed lines). In the present case, this involves a substantially symmetrical compression of the predetermined or predeterminable signal curve 5, which can be achieved, for example, by changing the operating parameters of the ionization electrode 9 or the AC voltage source. This then leads to the operating point 6 jumping from the predeterminable signal curve 5 to an evaluation position 8 of the deviating signal curve 7. For the two operating points 6.1 and 6.2, this is shown here via arrows and the evaluation positions 8.1 and 8.2. From the deviation between the two positions and / or the final position of the evaluation position 8, it is possible to draw a conclusion as to whether the control is actually taking place in the correct range or in a risky range.It is also shown here that a predetermined operating zone 10 is established with respect to the deviating signal curve 7, which is specified, for example, up to a maximum signal value. If, by transforming the signal curve from the predeterminable signal curve 5 to the deviating signal curve 7 and the associated shift of the operating point 6 to the evaluation position 8, it is recognized that the evaluation position 8 lies outside of this operating zone 10, this can be used, for example, to automatically set an emergency stop or emergency operation.

[0029] The Fig. 4The characteristic curve shown or the signal curve 5.7 selected there with the two local minima adjacent to the steep edges in the edge region can, on the one hand, result in a (rare) misinterpretation of a specific signal value. Nevertheless, the brief application of an interference signal or a signal modification offers simple possibilities for implementing a software-driven evaluation of the control situation. In particular, it is possible to change the ionization current, which is kept constant by the electronic circuit via a voltage variably applied to the electrode, so that the deviating signal curve 7 is established. The parameters are preferably selected so that a similar behavior is achieved, particularly with regard to the signal curve 5.7.

[0030] In this way, the problems described with reference to the prior art could be at least partially solved. In particular, a method for monitoring the operation of a heating device 1 was specified, with which undesirable or risky control situations can be reliably and quickly detected and, if necessary, even eliminated. Furthermore, appropriately configured heating devices 1 were specified that operate reliably and can be expanded without requiring significant technical effort. List of reference symbols

[0031] 1 Heater 2 Flame area 3 Combustion air 4 Fuel gas 5 Predeterminable signal curve 6 Operating point 7 Deviating signal curve 8 Evaluation position 9 Ionization electrode 10 Operating zone 11 Signal 12 Operating variable 13 Check routine 14 AC voltage source 15 Check measurement 16 Evaluation process 17 Stop 18 Control unit 19 Flame monitoring 20 Ignition electrode 21 Burner 22 Fan 23 Fuel gas valve 24 AC pulse generator 25 Microcontroller 26 Adjuster 27 Output resistance 28 Flame equivalent circuit 29 Evaluation electronics 30 Analog / digital converter

Claims

1. Method for monitoring the operation of a heater (1) by means of a measured signal associated with a flame region (2) of the heater (1) operated with combustion air (3) and combustion gas (4) and having a predeterminable signal curve (5), on which an operating point (6) of the heater (1) can be mapped, the predeterminable signal curve (5) being adjustable, characterized in that a deviating signal curve (7) is set at a predeterminable point in time, an evaluation position (8) of the operating point (6) being obtained.

2. Method according to claim 1, characterized in that the signal is an ionization signal which can be set via operating parameters of an ionization electrode (9) and the setting of the deviating signal curve (7) is caused by a change in the operating parameters.

3. Method according to claim 2, characterized in that the at least one operating parameter is an electrical variable of the ionization electrode (9).

4. Method according to one of the preceding claims, characterized in that a deviating signal curve (7) is maintained over an evaluation period of a maximum of two seconds and then the predeterminable signal curve (5) is set again.

5. Method according to one of the preceding claims, characterized in that the supply of combustion air (3) and combustion gas (4) is maintained during the presence of the deviating signal curve (7).

6. Method according to one of the preceding claims, characterized in that an instruction for further operation of the heater (1) is generated or stored from the generated evaluation position (8).

7. Method according to the preceding claim, characterized in that the operation of the heater (1) is stopped when the generated evaluation position (8) is outside a predetermined operating zone (10).

8. A heater (1) comprising at least an ionization electrode (8) and a micro-controller (25) arranged to carry out the steps of the method according to claim 1.

9. A computer program comprising instructions that cause a heater (1) comprising at least an ionization electrode (8) and a micro-controller (25) adapted to perform the steps of the method according to claim 1 to perform the steps of the method according to claim 1.

10. A computer-readable medium on which the computer program according to claim 9 is stored.