METHOD FOR OPERATING A BURNER DEVICE

Description

[0001] The invention relates to a method for operating a burner device according to the preamble of patent claim 1.

[0002] A method of the type mentioned above is known from document DE 10 2011 079 325 B4. In this method, an ignition spark is generated using an ignition electrode assigned to a burner, which is subjected to ignition voltage. In addition, an electrical voltage is measured with the ignition electrode. This solution, in which the ignition electrode for detecting the electrical voltage is separated from the means for generating the ignition voltage, serves to regulate the air ratio of the burner device. The said electrical voltage between the ignition electrode and the burner is temperature-dependent and is therefore also referred to as the flame temperature. The conductivity of the plasma channel that forms in the area of the ignition spark increases with the current flow from the voltage source used to measure the so-called thermoelectric effect.Methods according to the preamble of the method claimed here are also known from publications EP 2 886 959 A1 and EP 3 369 994 A1.

[0003] The invention is based on the object of improving a method of the type mentioned above. In particular, a method for assessing the quality of the ignition spark is to be created.

[0004] This object is achieved by a method of the type mentioned at the outset by the features listed in the characterising part of patent claim 1.

[0005] According to the invention, it is therefore provided that in a period from before the ignition spark until before a possible flame formation at the burner with the ignition electrode, a resulting change in the electrical voltage is measured and an error message is generated if the amount of this change is smaller than a predetermined minimum value.

[0006] In other words, the solution according to the invention is characterized by the fact that the so-called flame temperature is used to assess the quality of the ignition spark, based on the knowledge that this temperature must reach a minimum value in order to assume a high-quality ignition spark, i.e., one well-suited for ignition. If, for example, the ignition electrode is bent or covered with a drop of condensate, it becomes apparent that such a minimum value is not reached. Experiments underlying the invention have shown that this knowledge can be used to conclude that the ignition spark quality is poor.

[0007] As described, the measurement in question preferably begins when no ignition voltage is yet applied to the ignition electrode. Depending on the design, an electrical potential between the ignition electrode and the burner may (but does not have to) already be measurable in the burner's standby mode. This is not problematic, however, since no current flows and therefore no power is consumed.

[0008] During this measurement, a short circuit is created, causing the current flow through the voltage source to increase. The resulting current is measured using a measuring resistor; the ultimately measured voltage increases with the current flow. The more intense the ignition spark, the more conductive the plasma. Thus, an intense ignition spark causes a strong short circuit in the voltage source, meaning that as the current increases, the measured value of the so-called flame temperature rises.

[0009] Finally, as described, the measurement ends preferably shortly before a flame is formed on the burner at the latest, whereby it can ultimately also be provided that the measurement is carried out independently of an actual start of the burner, i.e. a start of the burner itself is not necessary to determine the ignition spark quality.

[0010] Other advantageous developments of the method according to the invention emerge from the dependent patent claims.

[0011] For the sake of completeness, reference is also made to the following documents: Document DE 10 2013 226 468 A1 discloses a diagnostic device that directly measures current and voltage (high voltage in the range of 8 to 15 kV) to evaluate the ignition spark. It is assumed that the higher the current and voltage, the greater the energy of the ignition spark. In contrast, the solution according to the invention only measures and evaluates a voltage change or a voltage drop in the measuring voltage (in the range of 5 V).

[0012] From the document WO 2011 / 117810 A2 a method for controlling a burner is known in which the electrical voltage of the fan motor is monitored.

[0013] The method according to the invention, including its advantageous developments according to the dependent patent claims, is explained in more detail below with reference to the drawing of a preferred embodiment.

[0014] It shows schematically Figure 1 shows a burner device with a burner, an ignition electrode and a counter electrode; and Figure 2 shows a diagram illustrating three different ignition spark qualities.

[0015] In Figure 1 a burner device is shown schematically and in perspective, in which an ignition spark is generated by an ignition electrode 2 which is assigned to a burner 1 and is subjected to ignition voltage, wherein it is particularly preferably provided that the ignition spark is generated between the ignition electrode 2 and a counter electrode 3, that is to say a fuel-air mixture flowing out of the surface of the burner 1 is ignited by the ignition spark located between the ignition electrode 2 and the counter electrode 3.

[0016] Furthermore, as already explained, it is provided that an electrical voltage is measured with the ignition electrode 2, wherein it is further particularly preferably provided that for measuring the electrical voltage the Figure 1 The measuring device 4 shown (a voltmeter) is used. Furthermore, in a conventional manner, both the burner 1 and the counter electrode 3 are connected to the electrical ground ("GND" - see: https: / / de.wikipedia.org / w / index.php?title=Masse_(Elektronik)&oldid=192430333) of the burner device.

[0017] What is essential for the method according to the invention is that in a period from before the ignition spark until before a possible flame formation on the burner 1 with the ignition electrode 2, a resulting change in the electrical voltage (which ultimately corresponds to a current flow through the aforementioned plasma channel of the ignition spark) is measured and an error message is generated if the amount of this change is smaller than a predetermined minimum value U min. It goes without saying that the method can also be used if the burner itself is not intended to be ignited at that moment. It should also be noted that the actual level of the minimum value U min ultimately depends on the specific measuring circuit used and that there is therefore no need to specify a specific numerical value here, although this can easily be determined and set by a specialist.

[0018] Regarding the measurement - looking at it in more detail - it is particularly preferred that the period for measuring the electrical voltage begins when a fan of the burner 1 has reached its starting speed, whereby this scenario is typically preceded by the heating control system determining a heat requirement and giving a corresponding request to ignite the burner 1.

[0019] Furthermore, it is particularly preferred that after reaching the starting speed, but before generating an ignition spark, a voltage reference value (between ignition electrode 2 and burner 1 or counter electrode 3) is first measured. This can be 0 volts; however, there are also burner devices in which, as already described above, an electrical potential is present at burner 1 or counter electrode 3 even in standby mode. However, this is unproblematic with regard to the power consumption of the burner device, since no current flows.

[0020] Furthermore, it is particularly preferred that after generating an ignition spark, a transient phase of preferably 1 to 3 seconds is waited for, and then a resulting voltage ignition value is measured. Flame formation is prevented in particular by not supplying fuel to the burner 1 during the measurement of the voltage ignition value.

[0021] In combination with the above-mentioned requirements, it is then further particularly preferably provided that the change in the electrical voltage (between the ignition electrode 2 and the burner 1 or the counter electrode 3) occurring in a period from before the ignition spark until before a possible flame formation at the burner 1 is determined from a difference between the aforementioned voltage ignition value and the aforementioned voltage reference value.

[0022] On the basis of the measurements described above, it is particularly preferred that a start-up of burner 1 is aborted if the resulting change is smaller in magnitude than a predetermined minimum value U mini, which is smaller in magnitude than the predetermined minimum value U min. Here, too, the actual level of the minimum value U mini depends on the specific measuring circuit used and, therefore, the specification of a specific numerical value, which can easily be determined and set by a specialist, is unnecessary at this point.

[0023] In Figure 2a) shows the voltage curve for a high-quality ignition spark, b) the voltage curve for a poorer, but still acceptable ignition spark, and c) the voltage curve for an ignition spark that is no longer acceptable. The voltage reference value, which may not be zero, has already been taken into account in the diagram. The largest value of the respective curve (i.e., where the gradient is zero) is used as the relevant value for the comparison.

[0024] The behavior according to b) occurs, for example, if the distance between the ignition electrode 2 and the counter electrode 3 has changed. In this case, a possible start would not be aborted, but a corresponding error message would be generated.

[0025] The process described in c) occurs, for example, if a water droplet has formed due to condensation between the ignition electrode 2 and the counter electrode 3. In this case, a possible start would be completely aborted or prevented with a corresponding warning. List of reference symbols

[0026] 1Burner 2Ignition electrode 3Counter electrode 4Measuring device U mind minimum value U mini minimum value

Claims

1. A method for operating a burner device, wherein an ignition spark is generated with an ignition electrode (2) assigned to a burner (1) and to which an ignition voltage is applied and wherein an electrical voltage is measured with the ignition electrode (2), characterised in that, in a period from before the ignition spark up to before a possible flame formation on the burner (1) a resultant change in the electrical voltage is measured with the ignition electrode (2) and an error report is generated if this change is less in absolute value than a predefined minimum value (Umind).

2. The method according to claim 1, characterised in that the period for the measurement of the electrical voltage starts when a ventilator of the burner (1) has reached its starting rate of rotation.

3. The method according to claim 2, characterised in that, after reaching the starting rate of rotation, but before generation of ignition spark, a voltage reference value is first measured.

4. The method according to claim 3, characterised in that, after generation of an ignition spark for preferably 1 to 3 seconds, a transient phase is awaited and a resultant voltage ignition value is then measured.

5. The method according to claim 4, characterised in that the change in the electrical voltage ensuing in the period from before the ignition spark up to before a possible flame formation on the burner (1) is determined from a difference between the voltage ignition value and the voltage reference value.

6. The method according to any one of claims 1 to 5, characterised in that a start of the burner (1) that has begun is discontinued when the resultant change is less in absolute value than a predefined minimum value (Umini), wherein the latter is less in absolute value than the predefined minimum value (Umind).

7. The method according to any one of claims 1 to 6, characterised in that the ignition spark is generated between the ignition electrode (2) and a counter electrode (3).

8. The method according to claim 7, characterised in that both the burner (1) and the counter electrode (3) are constituted connected to the electrical earthing of the burner device.