DE102022111802A1 - Method for operating a burner device - Google Patents

Abstract

The invention relates to a method for operating a burner device, in which air is conveyed into a combustion chamber (1), in which ignition sparks are generated with an ignition device (2) arranged in the combustion chamber (1) flooded with air, in which the Ignition spark, a fuel gas is mixed into the air and in which electrical voltage values present at the ignition device (2) are measured in the period from before the ignition spark is generated until after the fuel gas is added. According to the invention, it is provided that the voltage values measured during the said period of time and forming a voltage curve are evaluated to detect flame formation beginning with combustion of the fuel gas-air mixture containing at least 20% by volume of hydrogen.

Description

The invention relates to a method for operating a burner device according to the preamble of patent claim 1.

A procedure of the type mentioned at the beginning is from the document DE 10 2020 107 735 A1 known. In this process, air is pumped into a combustion chamber. Furthermore, ignition sparks are generated with an ignition device arranged in the combustion chamber flooded with air. In addition, a fuel gas is mixed into the air while the ignition spark is being generated. Finally, electrical voltage values present at the ignition device are measured in the period from before the ignition spark is generated until after the fuel gas has been added. With this solution, however, the voltage measurement is not only carried out during the presence of the ignition spark, but beforehand, in order to be able to determine from the voltage change that occurs during the measurement that this has a minimum value, and therefore that the ignition spark has a minimum quality. Or again in other words: This procedure is used to assess the quality of the ignition spark.

The invention is based on the object of improving a method of the type mentioned at the beginning. In particular, a method is to be created with which (if necessary in addition to the aforementioned method) the simplest possible adjustment of the fuel gas-air mixture can be achieved, even when using a fuel gas containing hydrogen.

This task is solved with a method of the type mentioned at the beginning by the features listed in the characterizing part of patent claim 1.

According to the invention, it is therefore provided that the voltage values measured in the said period of time and forming a voltage curve are evaluated to detect flame formation beginning with the combustion of the fuel gas-air mixture containing at least 20% by volume of hydrogen.

In other words, the method according to the invention is characterized in that the phase of admixing the fuel gas when starting the burner device is precisely observed with regard to the electrical voltage that occurs. This method serves in particular to detect the quality of the fuel gas and a control of the burner device based on or derived from it.

Other advantageous developments of the method according to the invention result from the dependent patent claims.

The method according to the invention, including its advantageous developments according to the dependent claims, is explained in more detail below using the graphic representation of a preferred exemplary embodiment.

• 1 schematisch die Brennereinrichtung zur Durchführung des erfindungsgemäßen Verfahrens;
• 2 einen Spannungsverlauf während der Flammenbildung mit einem kleinen Wasserstoffanteil im Brenngas; und
• 3 einen Spannungsverlauf während der Flammenbildung mit einem großen Wasserstoffanteil im Brenngas.

It shows

• 1 schematically the burner device for carrying out the method according to the invention;
• 2 a voltage curve during flame formation with a small hydrogen content in the fuel gas; and
• 3 a voltage curve during flame formation with a large hydrogen content in the fuel gas.

In 1 A burner device is shown schematically with which the method according to the invention can be carried out. In this method, air is first conveyed into a combustion chamber 1 in a known manner, in particular, as shown, via the line 1.1 and the burner 1.2. Furthermore, ignition sparks are generated with an ignition device 2 (in particular electrical) which is arranged in the combustion chamber 1 flooded with air and preferably has two ignition electrodes 2.2. Furthermore, while the ignition spark is being generated, a fuel gas is mixed into the air, again via line 1.1 and burner 1.2. In the period from before the ignition spark is generated until after the fuel gas has been added, electrical voltage values present at the ignition device 2 (in the physical unit “volt”) are also measured. Looking at it a little more closely, the electrical voltage in particular is measured between the aforementioned ignition electrodes 2.2. This is used in 1 voltmeter shown schematically 2.3.

What is essential for the method according to the invention is that the voltage values measured in the said period of time and forming a voltage curve are evaluated to detect flame formation beginning with the combustion of the fuel gas-air mixture containing at least 20% by volume of hydrogen. It is particularly preferred that the fuel gas contains at least 90% by volume of hydrogen.

Particularly preferably, it is further provided that in order to detect the formation of flames, the voltage curve is arranged on a voltage curve arranged between the two electrodes 2.2 of the ignition device 2 Capacitor 2.1 is measured. Preferably, the voltage curve is recorded analogue, but is digitized for evaluation (in a corresponding electronic unit).

Looking at it a little more closely, it is particularly preferred that a change in the voltage curve on the capacitor 2.1 in the said period of time is evaluated as a sign of the formation of flames. Depending on the ignition transformer used, the change in question can optionally result in a drop (as in the 2 and 3 shown) or also an increase (not shown separately) in the voltage curve.

It is further particularly preferably provided that a comparatively large gradient on the voltage curve of the capacitor 2.1 is taken as a sign of a comparatively large and a comparatively small gradient on the voltage curve of the capacitor 2.1 is taken as a sign of a comparatively small hydrogen content in the fuel gas. As can be seen, shows 2 the small and 3 the large gradient.

Again with reference to the two figures, it is also preferably provided that a comparatively large difference (see 2 ) between the voltage value on capacitor 2.1 before and after flame formation as a sign of a comparatively small and a comparatively small difference (see 3 ) between the voltage value on capacitor 2.1 before and after flame formation is taken as a sign of a comparatively large hydrogen content in the fuel gas.

Expressed again in other words: Using the detection according to the invention, it is ultimately even possible to recognize how much hydrogen is contained in the fuel gas, because this proportion influences - as shown - on the one hand the steepness and on the other hand the final level of the curve.

With regard to the aforementioned setting of the fuel gas-air mixture, it is also, as is known per se, preferably provided that a volume flow of supplied fuel gas is continuously increased starting from zero during the said period of time. In addition, it is particularly preferred according to the invention that the volume flow of fuel gas supplied is kept constant from the moment flame formation is detected, i.e. H. The ratio of fuel gas and air is ideally fixed at exactly the ratio at which the flame was created (optimal combustion).

• Der Brennerstart erfolgt, indem dem Verbrennungssystem ein konstanter Luftvolumenstrom zugeführt wird. Anschließend wird die Zündung eingeschaltet, wodurch sich Hochspannungsentladungen zwischen den Zündelektroden 2.1 ausbilden. Innerhalb weniger Millisekunden wird durch das entstehende Plasma der ionisierten Luft die maximale Durchbruchspannung erreicht. Durch den Zündfunken wirkt eine Spannung auf dem Kondensator 2.1, welche als Messsignal dient und im (nicht extra dargestellten) Feuerungsautomaten digitalisiert wird. Der Kondensator 2.1 hat beim Einschalten der Zündung ein kondensatortypisches Ladeverhalten. Zur Unterdrückung elektromagnetischer Effekte wird das digitalisierte Signal softwareseitig gefiltert. Sofern eine „sichere“ Zündung festgestellt worden ist (vergleiche wiederum das Dokument DE 10 2020 107 735 A1 ), wird das Gassicherheitsventil geöffnet und das Gasregelventil gemäß Kennlinie (Gasrampe) verfahren. Nachdem das Brenngas-Luft-Gemisch den Brennraum bzw. die Elektroden erreicht hat, setzen unverzüglich thermochemische, vorwiegend exotherme Reaktionen ein, die zu einer selbst erhaltenden Flammenausbreitung führen. Die Exothermie der Flamme selbst führt zu einer Veränderung der Leitfähigkeit an den Zündelektroden 2.1, wodurch die Durchbruchsspannung sinkt. Dadurch kommt es zum Entladen des Kondensators, und zwar trotz eingeschalteter Zündung. Das digitalisierte Signal erfährt entsprechend der gewählten Filtereinstellungen ebenfalls eine Veränderung. Mittels schwellwert-(niveaubasierter) oder gradientenbasierter Auswertung des Signals können, wie oben genauer beschrieben, verschiedene Vorgänge des Startablaufs wie Flammenerkennung oder Stopp der Gasrampe gesteuert werden. Rückschlüsse auf die Zusammensetzung des Brenngas-Luftgemisches können beispielsweise durch Bewertung von Zündzeit und dem Gradienten des Signals gezogen werden.

Expressed again in other words, the method according to the invention is characterized in particular as follows:

• The burner is started by supplying a constant air volume flow to the combustion system. The ignition is then switched on, causing high-voltage discharges to form between the ignition electrodes 2.1. Within a few milliseconds, the resulting plasma of ionized air reaches the maximum breakdown voltage. The ignition spark creates a voltage on the capacitor 2.1, which serves as a measurement signal and is digitized in the automatic burner (not shown). The capacitor 2.1 has a capacitor-typical charging behavior when the ignition is switched on. To suppress electromagnetic effects, the digitized signal is filtered in software. If a “safe” ignition has been determined (again compare the document DE 10 2020 107 735 A1 ), the gas safety valve is opened and the gas control valve is moved according to the characteristic curve (gas ramp). After the fuel gas-air mixture has reached the combustion chamber or the electrodes, thermochemical, predominantly exothermic reactions begin immediately, which lead to self-sustaining flame spread. The exothermicity of the flame itself leads to a change in the conductivity of the ignition electrodes 2.1, which reduces the breakdown voltage. This causes the capacitor to discharge, even though the ignition is switched on. The digitized signal also undergoes a change depending on the selected filter settings. As described in more detail above, various processes in the starting process such as flame detection or stopping the gas ramp can be controlled using threshold value (level-based) or gradient-based evaluation of the signal. Conclusions about the composition of the fuel gas-air mixture can be drawn, for example, by evaluating the ignition time and the gradient of the signal.

Reference symbol list

1

combustion chamber

1.1

Line

1.2

burner

2

Ignition device

2.1

capacitor

2.2

ignition electrode

2.3

Voltmeter

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102020107735 A1 [0002, 0018]

Claims (9)

Method for operating a burner device, in which air is conveyed into a combustion chamber (1), in which ignition sparks are generated with an ignition device (2) arranged in the combustion chamber (1) flooded with air, in which a fuel gas is generated while the ignition sparks are being generated Air is mixed in and in which electrical voltage values present at the ignition device (2) are measured in the period from before the ignition spark is generated until after the fuel gas has been added, characterized in that the voltage values measured in said period and forming a voltage curve are used to detect a combustion of the A fuel gas-air mixture containing at least 20% by volume of hydrogen can be evaluated for flame formation. Procedure according to Claim 1 , characterized in that to detect the formation of flames, the voltage curve is measured on a capacitor (2.1) arranged between two electrodes of the ignition device (2). Procedure according to Claim 2 , characterized in that a change in the voltage curve on the capacitor (2.1) during the said period is interpreted as a sign of flame formation. Procedure according to Claim 2 or 3 , characterized in that a comparatively large gradient on the voltage curve of the capacitor (2.1) is taken as a sign of a comparatively large and a comparatively small gradient on the voltage curve of the capacitor (2.1) as a sign of a comparatively small hydrogen content in the fuel gas. Procedure according to one of the Claims 2 until 4 , characterized in that a comparatively large difference between the voltage value on the capacitor (2.1) before and after the flame formation is a sign of a comparatively small and a comparatively small difference between the voltage value on the capacitor (2.1) before and after the flame formation is a sign of a comparatively large proportion of hydrogen in the fuel gas. Procedure according to one of the Claims 1 until 5 , characterized in that a volume flow of supplied fuel gas is continuously increased starting from zero during the said period. Procedure according to Claim 6 , characterized in that the volume flow of fuel gas supplied is kept constant from the moment flame formation is detected. Procedure according to one of the Claims 1 until 7 , characterized in that the fuel gas contains at least 90% by volume of hydrogen. Procedure according to one of the Claims 1 until 8th , characterized in that the voltage curve is recorded analogue, but is digitized for evaluation.

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