CN112240564A - Method and apparatus for adjusting sensitivity of detector for monitoring flame in heater - Google Patents
Method and apparatus for adjusting sensitivity of detector for monitoring flame in heater Download PDFInfo
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- CN112240564A CN112240564A CN202010669660.4A CN202010669660A CN112240564A CN 112240564 A CN112240564 A CN 112240564A CN 202010669660 A CN202010669660 A CN 202010669660A CN 112240564 A CN112240564 A CN 112240564A
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- Prior art keywords
- alternating voltage
- voltage pulses
- flame
- length
- frequency
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N5/00—Systems for controlling combustion
- F23N5/02—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium
- F23N5/12—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using ionisation-sensitive elements, i.e. flame rods
- F23N5/123—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using ionisation-sensitive elements, i.e. flame rods using electronic means
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23M—CASINGS, LININGS, WALLS OR DOORS SPECIALLY ADAPTED FOR COMBUSTION CHAMBERS, e.g. FIREBRIDGES; DEVICES FOR DEFLECTING AIR, FLAMES OR COMBUSTION PRODUCTS IN COMBUSTION CHAMBERS; SAFETY ARRANGEMENTS SPECIALLY ADAPTED FOR COMBUSTION APPARATUS; DETAILS OF COMBUSTION CHAMBERS, NOT OTHERWISE PROVIDED FOR
- F23M11/00—Safety arrangements
- F23M11/04—Means for supervising combustion, e.g. windows
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N5/00—Systems for controlling combustion
- F23N5/20—Systems for controlling combustion with a time programme acting through electrical means, e.g. using time-delay relays
- F23N5/203—Systems for controlling combustion with a time programme acting through electrical means, e.g. using time-delay relays using electronic means
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N2223/00—Signal processing; Details thereof
- F23N2223/18—Chopper
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N2223/00—Signal processing; Details thereof
- F23N2223/42—Function generator
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N2229/00—Flame sensors
- F23N2229/12—Flame sensors with flame rectification current detecting means
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
- Control Of Combustion (AREA)
Abstract
The invention relates to a method and a device for adjusting the sensitivity of a detector (11) for monitoring a flame in a heater (1), wherein an alternating voltage source (12) generates individual alternating voltage pulses (13) of an alternating voltage frequency (F1) and of a predeterminable length (L) between an ionizing electrode (7) and a counter electrode (9) in a flame region (2), wherein a time interval (T) is located between the start of successive alternating voltage pulses (13), and wherein the length (L) and/or the interval (T) of the individual alternating voltage pulses (13) can be adjusted. The device in a heater (1) with an air supply (3) and a combustion gas supply (4) comprises an ionization electrode (7), a counter electrode (9), an alternating voltage source (11) and computing electronics (14) for determining an ionization signal in a flame region (2). The alternating voltage source (12) is designed to generate individual alternating voltage pulses (13) of an alternating voltage frequency (F1), in particular greater than 1kHz, and of a specifiable length (L) at time intervals (T), wherein the length (L) and/or the time intervals (T) of the individual alternating voltage pulses (13) can be set. By adjusting the effective amplitude of the AC voltage source (12) in this way, the sensitivity of the detector (11) can be adjusted.
Description
Technical Field
The present invention relates to the field of regulating or monitoring the combustion process in a heater, and in particular to a burner for providing hot water or heating of a building. The quality of combustion is dependent primarily on the ratio of air to combustion gas present during combustion (lambda value, also referred to as air-fuel ratio), and for measuring the quality of combustion, ionization measurements are carried out in particular in the flame region in many heating devices. Such a measurement should enable a stable adjustment over a long period of time.
Furthermore, flame monitoring is also commonly performed in heaters, the main purpose of which is to ensure that the supply of combustion gas is not performed when there is no flame after the heater is activated. Thereby preventing the generation of potentially explosive mixtures and the escape of unburned combustion gases. This can be achieved in a number of different ways. Optical, thermal and electronic systems exist. The electronic flame monitors that are commonly used use an ignition electrode that is present anyway (which is not otherwise required after ignition of the flame) to generate an ionization signal for monitoring the flame. The specially processed ionization signal not only enables a reliable detection of the presence of a flame or the extinction of a flame, but also enables, for example, an early measurement of the physical weakening of the burner flame due to an excessively high air supply. Thus, in the event of a flame instability, shutdown may occur early.
Background
According to the prior art, flame monitoring has hitherto generally been carried out during operation by applying an alternating voltage, which is constant or adjustable in amplitude, to an ignition or ionization electrode (hereinafter referred to as ionization electrode), wherein the flame region which is ionized in the presence of a flame has a rectifying action, so that the ionization current flows predominantly in each case only during a half-wave of the alternating current. The current or a voltage signal derived therefrom (hereinafter referred to as ionization signal) is measured and, if necessary after digitization, further processed in an analog/digital converter for flame monitoring. In particular, alternating voltage sources with high output resistance have hitherto been used, which first of all supply an alternating voltage without a direct voltage component to the ionizing electrode and the counter electrode (ground). When a flame occurs between the two, the voltage drops essentially only in the half-wave due to the rectifying action of the flame due to the high output resistance, so that an alternating voltage with a negative direct voltage component is applied to the computation electronics (amplifier and converter), which is processed in the computation electronics as an ionization signal and can be converted into a digital signal in the analog/digital converter. In known flame monitoring systems, for example, alternating voltages with a frequency of up to 200 hertz Hz and an amplitude of 50 to 200 volts V are used. In order to be able to adjust the monitoring sensitivity, a voltage regulation is desirable, but requires considerable circuit engineering and expenditure on equipment, in particular also a relatively large transformer.
Disclosure of Invention
The invention is intended to provide a remedy in order to be able to achieve a safe and reliable operation of a heater with qualitatively and/or quantitatively precise flame monitoring with low equipment expenditure and low costs.
The object is achieved by a method, an apparatus and a computer program product according to the independent claims. Advantageous embodiments and refinements of the invention are specified in the respective dependent claims. The specification describes the invention and presents other embodiments, particularly when considered in conjunction with the accompanying drawings.
The method according to the invention for adjusting or adapting the sensitivity of a detector for monitoring a flame in a heater is characterized in that an alternating voltage source generates a number of alternating voltage pulses of a predeterminable alternating voltage frequency and of a predeterminable length, the predeterminable length being located between an ionization electrode and a counter electrode in the flame region, wherein a time interval exists between the start of the number of alternating voltage pulses, and wherein the length and/or the interval of the individual alternating voltage pulses can be adjusted. In this way, it is possible to set the effective amplitude of the alternating voltage, which allows a simpler and in particular less expensive design than when using a conventional alternating voltage source that is adjustable in amplitude. It has been found that the accuracy of the flame monitoring desired does not depend on whether the ac voltage is sinusoidal and continuous or not. It is only important that the effective amplitude, i.e. the integral of the respective amplitude, is reproducibly adjustable over time and that the integral of the positive and negative half-wave is also substantially constant over time, i.e. the negative and positive half-wave occur approximately the same. The shape of the occurrence of the alternating voltage pulses is, on the other hand, not critical, so that the individual pulses can have, for example, a decreasing amplitude. The effective amplitude of the alternating voltage, which acts solely on the ionization signal, can be adjusted by adjusting the time interval of the alternating voltage pulses, while the shape and length of the individual alternating voltage pulses remain unchanged. Thus, the sensitivity of the measurement can be adjusted in operation.
Preferably, the alternating voltage frequency is higher than the repetition frequency generated by the time interval of the alternating voltage pulses, in particular greater than 1 kilohertz [ kHz ]. Smaller transformers can be utilized to generate frequencies in the kilohertz range than low frequencies, thereby enabling smaller circuits overall.
In a particular embodiment of the invention, the alternating voltage frequency is greater than 15 kHz. A pulse can thus be generated which contains several successive waves, possibly decaying in their amplitude, and which can be repeated at suitable time intervals.
Suitable spacings are obtained in particular at repetition frequencies of between 0.2 and 15 kHz. The effective amplitude (voltage) of the alternating voltage can be adjusted within a wide range using these values.
In a preferred embodiment of the invention the maximum amplitude of the alternating voltage pulse is between 50-300 volts V, preferably between 100 and 200V.
Preferably, each ac voltage pulse should be substantially free of dc voltage components so that the rectifying action of the flame can be easily measured and calculated. The small dc voltage component that may be present should be constant anyway, so that the dc voltage component can be compensated if necessary.
In a particular embodiment of the invention, each alternating voltage pulse has an amplitude which decreases during its length. To generate such pulses, it is possible, for example, to use the so-called "flyback converter" principle. With a simple microcontroller, a simple adjustment of the effective amplitude can be carried out by varying the time interval of the alternating voltage pulses.
An apparatus for adjusting sensitivity of a detector for monitoring a flame in a heater having an air supply portion and a combustion gas supply portion according to the present invention includes: an ionization electrode, a counter electrode, an alternating voltage source and computer electronics for determining an ionization signal in the flame region, wherein the alternating voltage source is designed to generate a number of alternating voltage pulses at time intervals, in particular an alternating voltage frequency of more than 1kHz and of a predeterminable length, and wherein the length and/or the spacing of the number of alternating voltage pulses is adjustable. The so-called duty cycle, which is derived from the pulse length and the time interval, is used to set the desired effective amplitude of the alternating voltage, as a result of which the sensitivity of the measurement can be adapted to the operating conditions.
Preferably, the alternating voltage source is designed for alternating voltage pulses of a frequency greater than 15kHz and of constant length when adjusting the time interval of the alternating voltage pulses.
In a preferred embodiment, the time interval between the start of two successive alternating voltage pulses can be adjusted between 0.005 and 5 milliseconds ms, preferably between 0.05 and 1 ms.
The invention also relates to a computer program product comprising instructions for causing a heater to perform said method with said device.
Drawings
The working principle of the method according to the invention and of the exemplary embodiments thereof, to which the invention is not limited, will now be explained in detail with the aid of the drawings. Wherein:
FIG. 1: a heater with a flame monitoring device is schematically shown.
FIG. 2: showing a schematic circuit for generating an ionization signal according to the invention, an
FIG. 3: a graph illustrating the change in the effective amplitude of an ac voltage by comparing the prior art with the present invention is shown.
Detailed Description
Fig. 1 schematically shows an embodiment of the device proposed herein. In the heater 1 for burning the combustion gas mixed with air, a flame region 2 is formed in operation. The air reaches the heater 1 through the air supply portion 3 and the blower 5. The combustion gas is mixed with air via the combustion gas supply portion 4 and the combustion gas valve 6. The ignition electrode 7 ignites the mixture at the start of the combustion process and is then used, for example, as part of a flame monitoring device 11. In the previously customary systems, the ionization electrode 8 is usually used to measure an ionization signal in the flame region 2, which is used to adjust the lambda value when the heater is in operation. The regulating unit 10 is then used to regulate the blower 5 and/or the combustion gas valve 6 accordingly. The flame monitoring device 11 according to the invention ensures that only combustion gas is supplied when a stable flame is detected. For this purpose, a further ionization electrode is used, for which mostly the ignition electrode 7 can be used, in order to generate a further ionization signal, the electronic processing of which is specifically designed for the purpose of flame monitoring. In particular the alternating voltage source 12 is designed for this purpose.
FIG. 2 schematically illustrates one embodiment of a circuit that can be used with the flame monitoring device. An ac voltage source 12 with a high output resistance 13 first supplies an ac voltage with substantially no dc voltage component to the ignition electrode 7 and the counter electrode 9 (ground). When a flame occurs between the two (shown here as an equivalent circuit diagram 16), the voltage drops only in half-waves due to the rectifying action of the flame (shown as a diode in the equivalent circuit diagram), so that an alternating voltage with a negative direct voltage component appears at the input of the computing electronics 14 (amplifier and converter), which alternating voltage becomes the desired ionization signal in the computing electronics 14 and is converted in an analog/digital converter (analog-digital converter) 15 and can then be further processed. This overall arrangement forms a detector for a flame monitoring device, which then provides an ionization signal only in the presence of a flame, wherein the ionization signal also has a typical course from which, for example, a physical weakening of the beginning of the flame at the gas outlet can be recognized, so that a shut-off can be carried out even if the beginning is unstable due to an excessively high gas velocity or an excessively high lambda value. However, the sensitivity of the detector depends on the amplitude of the alternating voltage used, so that in the prior art it is usual to adjust the amplitude of the alternating voltage, for example between 50V and 200V at a frequency of, for example, 200 Hz. According to the invention, an ac voltage source 12 with an ac voltage pulse generator 17, a microcontroller 18 and a regulator 19 is now used. This design results in a cost-effective and space-saving ac voltage source 12, in which the effective amplitude can be adjusted according to the desired detector sensitivity. The effective amplitude, although not in the form of a typical approximately sinusoidal alternating voltage, on further processing gives rise to the same ionization signal as a sinusoidal alternating voltage with this amplitude.
Figure 3 qualitatively illustrates what happens in the process of adjusting the effective amplitude according to the invention. In the upper part of fig. 3 it is shown how the sinusoidal alternating voltage of the amplitude U1 changes when the amplitude is reduced to the value U2. The voltage U is plotted against the time t in this diagram.
In the lower part of fig. 3 it is shown how the effective amplitude of the alternating voltage formed by the individual alternating voltage pulses 13 of length L can be adjusted by varying the intervals T between the individual alternating voltage pulses 13, such as T1 and T2. A greater effective amplitude is produced in interval T1 than in the larger interval T2. If the maximum amplitude Umax of the individual ac voltage pulses 13, and if appropriate also the frequency F1 of the ac voltage pulses, is selected appropriately, the effective amplitude can be adjusted in accordance with the sinusoidal ac voltage shown in the upper part of fig. 3. Furthermore, the alternating voltage frequency F1 is higher than the repetition frequency F2 resulting from the time interval T of the alternating voltage pulses 13.
The invention thus makes possible an alternative, cost-effective design for an adjustable ac voltage source in a detector for flame monitoring in a heater.
List of reference numerals
1 Heater
2 flame area
3 air supply part
4 combustion gas supply part
5 blower
6 combustion gas valve
7 ignition electrode
8 ionizing electrode
9 burner/counter electrode
10 adjusting unit
11 Detector/flame monitoring device
12 a.c. voltage source
13 output resistor
14 computing electronic device
15 analog/digital converter
Equivalent circuit diagram of 16 flames
17 ac voltage pulse generator
18 microcontroller
19 regulator
First amplitude of U1
Second amplitude of U2
Maximum amplitude of Umax
T1 first time interval
T2 second time interval
Claims (12)
1. A method for adjusting the sensitivity of a detector (11) for monitoring a flame in a heater (1), characterized in that an alternating voltage source (12) generates individual alternating voltage pulses (13) of an alternating voltage frequency (F1) and of a predeterminable length (L) between an ionizing electrode (7) and a counter electrode (9) in a flame region (2), wherein a time interval (T) is located between the start of successive alternating voltage pulses (13), and wherein the length (L) and/or the spacing (T) of the individual alternating voltage pulses (13) is adjustable.
2. Method according to claim 1, characterized in that the alternating voltage frequency (F1) is higher than the repetition frequency (F2) resulting from the time interval (T) of the alternating voltage pulses (13).
3. Method according to claim 1 or 2, characterized in that said alternating voltage frequency (F1) is greater than 1 kilohertz.
4. Method according to any one of the preceding claims, characterized in that said alternating voltage frequency (F1) is greater than 15 kilohertz.
5. Method according to any one of the preceding claims, characterized in that said repetition frequency (F2) is between 0.2 and 15 khz.
6. Method according to any of the preceding claims, characterized in that the maximum amplitude (Umax) of the alternating voltage pulses (13) lies between 50 and 300 volts.
7. Method according to any of the preceding claims, characterized in that each alternating voltage pulse (13) has substantially no direct voltage component.
8. Method according to any of the preceding claims, characterized in that each alternating voltage pulse (13) has a reduced amplitude (U) during its length (L).
9. A device for adjusting the sensitivity of a detector (11) for monitoring a flame in a heater (1) having an air supply (3) and a combustion gas supply (4), comprising an ionization electrode (7) in a flame region (2), a counter electrode (9), an alternating voltage source (11) and calculation electronics (14) for determining an ionization signal, characterized in that the alternating voltage source (11) is configured for effecting the generation of individual alternating voltage pulses (13) of an alternating voltage frequency (F1) and of a predeterminable length (L) at time intervals (T), and in that the length (L) and/or the time interval (T) of the individual alternating voltage pulses (13) are adjustable.
10. Device according to claim 9, characterized in that the alternating voltage source is designed for alternating voltage pulses (13) of a frequency (F1) of more than 15 kilohertz and of a constant predetermined length (L) with the possibility of adjusting the time interval (T) of the alternating voltage pulses (13).
11. A device according to claim 9 or 10, characterized in that the time interval (T) between the start of two successive alternating voltage pulses is adjustable between 0.005 ms and 5 ms.
12. A computer program product comprising instructions, characterized in that the instructions cause an apparatus according to any of claims 9 to 11 to perform a method according to any of claims 1 to 8.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE102019119206.4 | 2019-07-16 | ||
| DE102019119206.4A DE102019119206A1 (en) | 2019-07-16 | 2019-07-16 | Method and device for adapting the sensitivity of a detector for monitoring a flame in a heating device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN112240564A true CN112240564A (en) | 2021-01-19 |
Family
ID=71575151
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202010669660.4A Pending CN112240564A (en) | 2019-07-16 | 2020-07-13 | Method and apparatus for adjusting sensitivity of detector for monitoring flame in heater |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP3767175A1 (en) |
| CN (1) | CN112240564A (en) |
| DE (1) | DE102019119206A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113253031A (en) * | 2021-05-19 | 2021-08-13 | 广东电网有限责任公司 | Mountain fire trip test platform for power transmission line |
| DE102022111802A1 (en) * | 2022-05-11 | 2023-11-16 | Viessmann Climate Solutions Se | Method for operating a burner device |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5472336A (en) * | 1993-05-28 | 1995-12-05 | Honeywell Inc. | Flame rectification sensor employing pulsed excitation |
| NL1024388C2 (en) * | 2003-09-26 | 2005-03-31 | Betronic Design B V | Flame monitoring system. |
| US7800508B2 (en) * | 2005-05-12 | 2010-09-21 | Honeywell International Inc. | Dynamic DC biasing and leakage compensation |
| DE102007018122B4 (en) * | 2007-04-16 | 2013-10-17 | Viessmann Werke Gmbh & Co Kg | Flame monitoring device with a voltage generating and measuring arrangement and method for monitoring a burner by means of the flame monitoring device |
| DE102013009119A1 (en) * | 2013-05-29 | 2014-12-04 | Kübler Gmbh | Method for controlling a heating system with a plurality of dark radiator units and arrangement for carrying out the method |
-
2019
- 2019-07-16 DE DE102019119206.4A patent/DE102019119206A1/en active Pending
-
2020
- 2020-07-10 EP EP20185200.1A patent/EP3767175A1/en active Pending
- 2020-07-13 CN CN202010669660.4A patent/CN112240564A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| EP3767175A1 (en) | 2021-01-20 |
| DE102019119206A1 (en) | 2021-01-21 |
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