ES3031119T3 - Method for monitoring the operation of a heating apparatus, heating apparatus and computer program and computer readable medium - Google Patents

Abstract

The invention relates to a method for monitoring the operation of a heater (1) by means of a measured signal assigned to a flame zone (2) of the heater (1) operating with combustion air (3) and fuel gas (4). Said signal has a predeterminable signal profile (5) in which an operating point (6) of the heater (1) can be mapped, said predeterminable signal profile (5) being adjustable. It is characterized in that a deviated signal profile (7) is set at a predeterminable time, resulting in an evaluation position (8) of the operating point (6). In particular, the signal is an ionization signal that can be set by the operating parameters of an ionization electrode (9), where the setting of the deviated signal profile (7) is initiated by a change in the operating parameters. (Automatic translation with Google Translate, no legal value)

Description

DESCRIPTION

Method for monitoring the operation of a heater, heater, as well as computer program and computer-readable medium

The present invention relates to a method for monitoring the operation of a heater, a correspondingly configured heater, a computer program and a computer-readable medium.

The invention is particularly relevant to the control of a fuel gas-air mixture for a combustion process in a heater, particularly for hot water production or heating a building. To measure the combustion quality, which primarily depends on the ratio of air to fuel gas (lambda value (A), also known as air ratio) during combustion, an ionization measurement is performed in a flame zone, particularly in many heating devices. These measurements should enable stable control over long periods of time. If the control system fails, in most cases the heater must be shut down, which, of course, should occur as rarely as possible.

Furthermore, flame monitoring can also be implemented in heaters, the main task of which is to ensure that fuel gas is not supplied after the heater is ignited 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 detector uses an existing ignition electrode, which would otherwise not be required after a flame has been ignited, to generate an ionization signal. In the prior art, this is not used to control, but rather to monitor the flame. The specially processed ionization signal can not only reliably detect the presence of a flame or its extinction, but can also measure, for example, the physical rise of the burner flame due to excessive combustion air supply at an early stage. This enables early shutdown in the event of flame instability.

According to the prior art, control during operation is often performed using a separate ionization electrode. Regardless of the electrode type, the actual ionization value in the flame zone is determined, which is proportional to the currently existing A value, so that the latter can be derived from the ionization measurement. An alternating voltage is applied to the ionization electrode, whereby the ionized flame zone in the presence of flames has a rectifying effect, such that an ionization current flows primarily only during a half-wave of the alternating current. This electric 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-to-digital converter. The A value can be measured and regulated to a set point via a control loop. The supply of air and/or fuel gas is modified by suitable actuators until the desired setpoint for A is reached. In general, a value of A > 1.0 is sought (1.0 corresponds to a stoichiometric ratio), for example, a value of A = 1.3 is used to ensure that sufficient air is supplied for clean combustion without carbon monoxide production. However, A must remain small enough to ensure stable combustion. Control can be achieved, in particular, via a valve for the fuel gas supply and/or a blower for the combustion air supply.

When controlling combustion using a measured ionization signal, it is occasionally or at specific intervals necessary to verify plausibility and/or calibrate the control. For example, EP 3690318 A2 specifies a method by which an ionization signal check can be performed using a specific operation or a specific setting of the blower and/or fuel gas valve. The method described there is also particularly suitable for switching to so-called emergency operating control in the event of undesired operating conditions, so that in the event of a failure in the primary control system, it is not necessary to shut down, but only to switch to the emergency operating system. The method disclosed there has already proven to be very effective, but there is still room for improvement.

It is possible for the ionization signal to have a complex curve, for example, one that is not constant or linear over a given operating parameter or heater control parameter. In particular, this signal curve can be designed with locally limited lows, plateaus, or rising and/or falling edges. Especially with such complex signal curves, there is a risk that, due to sudden events, the operating point on this signal curve may jump from one point to another without the control being able to easily detect this. This is particularly the case when the complex signal curve shows the same ionization current throughout the operating range of the control parameter or at different points. A sudden event can be considered, for example, a spontaneous blockage of the combustion air supply, e.g., by placing a leaf on the intake point, whereby the control parameter jumps from a local point on the signal curve to another (possibly distant) point on the signal curve, which may go unnoticed if the ionization current is approximately the same there. Therefore, it is necessary to reliably detect this jump so that regulation is always carried out within the correct range.

Furthermore, especially if a more intense modulation of the control system is considered—for example, because the heater will be used to provide water for the shower—very rapid and short-term methods are required to verify the current control situation. The methods commonly used to date, which involve switching the combustion air supply and/or operating the gas valve, may not be rapid enough for this purpose or may cause excessive temperature fluctuations in the shower water, meaning that water comfort for the shower user cannot be guaranteed.

Furthermore, this verification must be carried out with existing electronics or conventional heating devices (including their control systems) so that, for example, the costs of intensive retrofitting can be avoided.

It is also desirable for the system to automatically detect when a control (risk) situation currently exists, so that it can transition to emergency operation or even an emergency stop without requiring, for example, intervention by service personnel.

Based on this, the objective 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 heater must be specified, with which undesired or dangerous control situations can be reliably and quickly detected and, if necessary, even eliminated. Furthermore, appropriately equipped heating devices must be specified that operate reliably and can be expanded without requiring significant technical effort.

These objects are achieved by a method for monitoring the operation of a heater according to the features and steps of patent claim 1. Further embodiment variants and advantageous aspects of the invention are specified in the dependent claims. It should be noted that the features or steps listed individually in the patent claims can be combined with one another in any technologically reasonable manner and give rise to improvements and exemplary embodiments of the invention. The description, particularly in conjunction with the figures, explains the invention and provides further exemplary embodiments.

A method for monitoring the operation of a heater contributes to this, as explained below. Monitoring is performed using a measurement signal assigned (or assignable) to a flame zone of the heater operated with combustion air and fuel gas, with a predetermined signal curve on which a heater operating point can be mapped. Furthermore, the predetermined signal curve can be adjusted. The goal is to establish a deviated signal curve at a predefined time, resulting in an evaluation position of the operating point.

The method is used in particular to monitor or check the control of the heater's operation. The control method is carried out in particular at the time when there are actually flames in the flame zone, i.e., when the supplied combustion air and fuel gas have been ignited. The heater may include a measuring system in which a combustion parameter is detected in the flame zone, the detection of which results in an (electrical) signal with a predeterminable signal curve. This signal is therefore characteristic of the flame zone, in particular of the combustion occurring there. The measured signal can be located on a predeterminable signal curve, with the currently determined signal value being characteristic of the operating point of the combustion or the heater. The predeterminable signal curve can be set circuit-specifically, for example, by the measuring system or the measuring device, so that a signal curve characteristic of the combustion and/or the heater can be specifically specified. For example, the signal curve may cover the operating range across a predefined operating parameter, such as the A value, the speed of a blower, etc. The signal curve can be characterized by edges, plateaus, local minima, and/or local maxima. If the operating parameter varies within this operating range, the operating point moves along this signal curve, so that a current operating parameter of the heater can be determined based on a predetermined flame signal. This signal curve can be adjusted (electronically), in particular by shifting, compressing, or expanding the curve. For normal heater operation, a specific signal curve is usually predetermined for control.

It is now proposed that this electronically preset signal curve be modified or shifted at a predetermined point in time or at a point in time automatically initiated by other events, such that the shifted signal curve is not identical to the normally set, predeterminable signal curve. This results in the (normal) operating point of the heater now being represented on a shifted signal curve, with this modified position being an evaluation position of the operating point. The evaluation position is therefore not a (non-real) operating point of the heater, but a position that essentially serves exclusively to check the position of the operating point against the ordinary, predeterminable signal curve. The shift or change of the signal curve causes, for example, this operating point to move to other regions of the displayed flame signal, whereby conclusions about the plausibility or status of the control can be drawn from this shift or modified position.

Preferably, the signal is an ionization signal that can be adjusted via operating parameters of an ionization electrode, with the adjustment of the deviated signal curve being initiated by a change in the operating parameters. In this way, an ionization signal or an ionization current is determined in the flame region, which is used as a basis for controlling the combustion of the heater. The operating parameters of the ionization electrode are, for example, the type of alternating voltage, current, frequency, amplitude, etc. In other words, this means in particular that to (briefly) change the signal curve, one or at least one of these operating parameters is readjusted, and thus the deviated signal curve is reached at the specified time. In this context, it is particularly preferred that at least one operating parameter is an electrical variable of the ionization electrode.

It is possible to maintain the deviated signal curve for a maximum evaluation period of 2.0 seconds and then restore the preset signal curve. It is particularly preferable to choose 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 should be tailored specifically to the control or measurement sensitivity of the heater or measuring system. This allows the operation or control to be checked very quickly and in a short time, and the system can quickly return to normal operation. This allows relatively frequent checking of the current situation without adversely affecting the proper combustion function of the heater.

Particularly preferably, the supply of combustion air and fuel gas is maintained (constant or unchanged) as long as the deviated signal curve exists. In other words, this means that a functional or control check can be performed without changing (mechanical) control elements, such as the gas valve and/or blower. Instead, a (stable) combustion process or a corresponding combustion situation can be identified and combustion can then be kept unchanged for a short period, thereby modifying the analysis of the measured value (electronically only).

In particular, it is possible for an instruction for subsequent operation of the heater to be generated or stored from the second evaluation position. This means, for example, that the newly adjusted and deviated signal curve has a contour such that the operating point, depending on its position on the specified (normal) signal curve, is brought to an evaluation position that allows a clear assessment of the current combustion or the current operation of the heater. In this regard, a clear command, status report, or similar instruction can also be provided based on this clear, electronically generated evaluation position. This instruction can be (tacitly) saved, but it is also possible for corresponding commands to be transmitted to other systems and/or even made available to the heater user.

It is particularly preferred that heater operation be stopped when the generated evaluation position lies outside a predetermined operating zone. In particular, by adjusting the deviated signal curve, imaginary operating zones can be created that signal particularly dangerous operating states of the heater. If an operating point is located in a risk zone, shifting the actual operating point to the imaginary evaluation position causes a shift in an operating zone identified as critical. In this regard, depending on the position of the generated evaluation position, an emergency operation and/or an emergency stop can be initiated automatically.

According to a further aspect, a heater is proposed, comprising at least one ionization electrode and means configured to carry out the steps of the method proposed herein. These means include a microcontroller capable of configuring and/or evaluating the signals or signal curves. In particular, means are provided for adjusting the operating parameters of an electrical quantity of the ionization electrode.

According to a further aspect, a computer program is provided comprising commands that cause a heater, comprising at least one ionization electrode and means suitable for carrying out the steps of the method proposed herein, to carry out the steps of the proposed method. According to a further aspect, said computer program may be stored on a computer-readable medium, e.g., a computer.

The invention and the technical context 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 with facts from the general description, unless this is explicitly excluded herein. The following are shown in the following:

Fig. 1: Schematic of a heater with flame monitor,

Fig. 2: A schematic circuit for generating an ionization signal,

Fig. 3: A visualization of the process flow, and

Fig. 4: A diagram with example signal curves.

Fig. 1 schematically shows an exemplary embodiment of a device with a heater 1. For the combustion of a fuel gas with air, a flame zone 2 is formed in the heater 1 during operation. The combustion air 3 enters the heater 1 via an air supply and a blower 22. The fuel gas 4 is added to the combustion air 3 via a fuel gas valve 23. An ignition electrode 20 ignites the mixture at the beginning of the combustion process and is used, for example, as part of a flame monitor 19. It is possible to measure an ionization signal in the flame zone 2 by means of an ionization electrode 9, which makes it possible to monitor the lambda value (A) during operation of the heater 1. For this purpose, a control unit 18 is used, which controls the blower 22 or the fuel gas valve 23 as appropriate. A flame monitor 19 ensures that the fuel gas 4 is only supplied when a stable flame is detected. For this purpose, an additional ionization electrode 9, typically the ignition electrode 20, is used to generate another ionization signal, the electronic processing of which is specifically designed for flame monitoring 19. In particular, an alternating voltage source 14 has been designed for this purpose.

Fig. 2 shows a schematic illustration of an embodiment of a circuit for flame monitoring 19. An alternating voltage source 14 with a high output resistance 27 initially supplies an alternating voltage without a direct voltage component to the ignition electrode 20 and the counter electrode (burner 21, ground). When a flame is generated between the two (shown here as equivalent circuit 28), the voltage across the flame rectifying effect (shown as a diode in the equivalent circuit) drops by only a half-wave, so that an alternating voltage with a negative direct voltage component is present at the input of the evaluation electronics 29, which is converted into the desired ionization signal in the evaluation electronics 29 and can be converted in an analog-to-digital converter 30 and further processed. This whole assembly forms a preferable detector for flame monitoring 19, which then provides an ionization signal when there is a flame, the ionization signal also presenting a typical curve from which one can recognize, for example, an incipient physical rise of the flames from the gas outlet openings, so that extinguishing can also occur in the case of an incipient instability due to excessively high gas velocities and/or excessively high A values.

An alternating voltage source is used having an alternating voltage pulse generator 24, a microcontroller 25 and an adjuster 26. This design creates a cost-effective and compact alternating 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 shape of a typical, approximately sinusoidal alternating voltage, it leads to the same ionization signals during post-processing as a sinusoidal alternating voltage with this amplitude. The provision of such an alternating voltage source also makes it possible (briefly) to generate and provide deflected signal curves 7 for this ionization signal.

Fig. 3 schematically illustrates a possible embodiment of the method, with the usual control of the operation of the heater 1 being illustrated on the left. At a given time (designated here as t1), for example, the setting of the alternating voltage source 14 can be changed such that a verification measurement 15 is carried out. Whereas until now the operation of the heater 1 was monitored by means of the flame monitor 19 and a signal measured in the flame zone 2 (in particular the ionization signal) with a predetermined, ordinary signal curve 5, now at this time a deviated signal curve 7 is established. This deviated signal curve 7 is maintained during the verification measurement 15 until a later time (designated here as t2) at which the alternating voltage source 14 is readjusted again, i.e. in such a way that it again reaches the predetermined ordinary signal curve 5. During this verification measurement 15, the settings of the blower 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 deviated signal curve 7 can be subjected to an evaluation process 16, in which, based on this evaluation or assessment, it is then possible to determine as a result of this check routine 13 whether to return (on the left) to normal, regular operation of the heater or whether (alternatively) to an emergency operating situation is to be established on the right in which, for example, a shutdown 17 is decided with respect to the operation of the heater 1.

Fig. 4 illustrates an example of a signal curve in normal operation of heater 1, i.e., the predeterminable signal curve 5, with the actual operating point 6 of heater 1, on the basis of which control is performed (shown here as a solid line). The ordinate may represent, for example, signal 11, in particular the ionization signal. On the abscissa, a relevant operating variable 12 of heater 1 may be shown, for example, the blower speed, an A value, etc. The predeterminable signal curve 5 characterizes or spans the usual operating range of this operating variable 12. In this case, it is characterized, from left to right, by a sharp initial falling edge, a local minimum, a somewhat longer intermediate plateau, a local minimum, and a sharp rising edge. As an example, the actual operating point 6 could be in the area of the right local minimum (see position 6.2). However, it is possible, for example, that due to a short-term malfunction or a short-term interruption of combustion air, the operating point may suddenly jump to the other side, to the left, i.e., to an edge of the local minimum (see section 6.1). If the system does not detect this sudden change, it will regulate in the wrong zone, which can lead to considerable problems.

It is therefore now proposed to establish a deviated signal curve 7 at a given 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 alternating voltage source. This now causes the operating point 6 to jump from the predeterminable signal curve 5 to an evaluation position 8 of the deviated signal curve 7. For the two operating points 6.1 and 6.2, this is shown here by arrows, and the evaluation positions 8.1 and 8.2. From the deviation of the two positions and/or the end position of the evaluation position 8, it is possible to conclude whether the regulation is in a correct or a risky range. It is also shown here that a predetermined operating range 10 is established with respect to the diverted signal curve 7, which is specified, for example, up to a maximum signal value. If, as a result of the transformation of the signal curve from the predeterminable signal curve 5 to the diverted 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 this operating range 10, this can be used, for example, to automatically establish an emergency stop or emergency operation.

The characteristic curve shown in Fig. 4 or the signal curve 5, 7 selected there with the two local minima adjacent to the pronounced edges in the edge area may, on the one hand, lead to a (rare) misinterpretation of a specific signal value, but the short-term application of an interference signal or a signal modification offers simple possibilities for performing a software-based evaluation of the control situation. In particular, it is possible to modify the ionization current, which is kept constant by the electronic circuit through a variably applied voltage to the electrode, so that the deviated signal curve 7 is established. The parameters are preferably chosen in such a way that a similar behavior is achieved, especially with respect to the signal curve 5, 7.

In this way, the problems described with reference to the prior art could be at least partially resolved. In particular, a method for monitoring the operation of a heater 1 has been specified, with which undesired or risky control situations can be reliably and quickly detected and, if necessary, even eliminated. Furthermore, appropriately equipped heaters 1 have been specified, which operate reliably and can be expanded without requiring significant technical effort.

List of reference signs

1 Heater

2 Flame Zone

3 Combustion air

4 Fuel gas

5 Preset signal curve

6 Operating point

7 Deviated signal curve

8 Evaluation position

9 Ionization electrode

10 Operating area

11 Sign

12 Operating variable

13 Check routine

14 Alternating voltage source

15 Verification measurement

16 Evaluation process

17 Stop

18 Control unit

19 Flame Monitor

20 Ignition electrode

21 Burner

22 Blower

23 Fuel gas valve

24 Alternating voltage pulse generator

25 Microcontroller

26 Adjuster

27 Output resistance

28 Equivalent circuit of a flame

29 Evaluation Electronics

30 Analog/Digital Converter

Claims (10)

1. Method for monitoring the operation of a heater (1) by means of a measured signal associated with a flame zone (2) of the heater (1) operating with combustion air (3) and fuel gas (4) with a predeterminable signal curve (5), in which an operating point (6) of the heater (1) can be represented, the predeterminable signal curve (5) being adjustable, characterized in that at a predeterminable time a deviated signal curve (7) is fixed, obtaining an evaluation position (8) of the operating point (6). 2. Method according to claim 1, characterized in that the signal is an ionization signal that can be configured through operating parameters of an ionization electrode (9) and the adjustment of the deviated 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 deviated signal curve (7) is maintained for an evaluation period of a maximum of two seconds and then the predeterminable signal curve (5) is established again. 5. Method according to one of the preceding claims, characterized in that the supply of combustion air (3) and fuel gas (4) is maintained during the presence of the deviated signal curve (7). 6. Method according to one of the preceding claims, characterized in that from the generated evaluation position (8) an instruction for the subsequent operation of the heater (1) is generated or stored. 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. Heater (1) comprising at least one ionization electrode (8) and a microcontroller (25) which are designed to carry out the steps of the method according to claim 1. 9. Computer program comprising commands that cause a heater (1) comprising at least one ionization electrode (8) and a microcontroller (25) adapted to perform the steps of the method according to claim 1 to execute the steps of the method according to claim 1. 10. Computer-readable medium on which the computer program according to claim 9 is stored.