EP4145047A1 - Method and assembly for detecting the ignition of flames in a combustion chamber of a heating device, computer program product and use - Google Patents

Abstract

The invention relates to a method and an arrangement for observing or monitoring the ignition of flames (16) in a combustion chamber (15) of a heating device (1), with a speed (n) of a fan (2) for supplying an air-fuel gas mixture to the combustion chamber (15) is observed and from a characteristic course of the speed (n) an ignition of flames (16) in the combustion chamber (15) is concluded. In particular, an increase in the speed by at least 0.1% in less than 0.1 s is interpreted by evaluation electronics (11) as an indication that flames (16) have ignited in the combustion chamber (15). The invention makes it possible, without additional sensors, to check the function of a conventional flame monitor when a combustion process is ignited, or to provide a redundant measuring system in order to ensure that the ignition process runs reliably.

Description

The invention relates to a method and an arrangement for detecting the ignition of flames in a combustion chamber of a heating device, in particular one that can be operated with hydrogen and/or a fuel gas containing hydrogen. It is not only a question of large systems, but also of wall-mounted units for heating water and, in general, heaters for heating buildings and/or providing hot water. The invention also relates to a related computer program product and use.

In heaters, simple and robust sensors for temperature, light or heat radiation, pressure, volumetric flow and the like are generally used to control the heater and ensure its safe operation. An important task is to determine the presence of stable flames (a so-called flame monitor), another is the setting of a ratio of combustion air to fuel gas (lambda value) that is suitable for stable and environmentally friendly combustion.

If flames ignite properly, this is detected by at least one sensor in or on the combustion chamber, as is an (unexpected) extinguishing of the flames. Ionization measuring devices, temperature sensors or optical sensors, e.g. B. for UV radiation, for the application. Through the function of a Flame monitor can be used to ensure that combustion always takes place when fuel gas is supplied or that the device is switched off if the flames do not ignite or go out.

For cost reasons and in order to keep the complexity of a heating device low, such flame monitors are very reliable, but usually only exist once, so that a check of their function or a redundancy of measuring systems is not always possible.

On the other hand, heaters in which a fan is provided for supplying air and fuel gas are generally controlled by controlling the number of revolutions of the fan and adjusting a fuel gas valve. The speed of the fan is therefore continuously measured and kept at a desired value. When a heater is started, the fan is brought to a predetermined speed and maintained at this speed, while the combustion gas valve is opened and an ignition sequence is initiated by an ignition controller.

The object of the present invention is to at least partially alleviate the problems described with reference to the prior art and, in particular, to determine the ignition of flames and/or the time of ignition in the heaters described without additional instrumentation independently of sensors present in or on the combustion chamber to be able to

A method and an arrangement as well as a computer program product and a use according to the independent claims serve to solve this task. Advantageous refinements and developments of the invention are in the respective dependent claims. The description, in particular in connection with the drawing, illustrates the invention and specifies further exemplary embodiments.

A method for observing or monitoring the ignition of flames in a combustion chamber of a heater contributes to solving the problem, with the speed of a fan for supplying an air-fuel gas mixture to the combustion chamber being observed and from a (chronological, in particular characteristic) course the engine speed indicates that flames are igniting in the combustion chamber.

Measurements have shown that the fan speed is briefly and characteristically influenced by a type of pressure surge that occurs in the combustion chamber when the flames ignite. This can be easily recognized because the speed is constantly monitored and regulated anyway. Although the control tries to quickly bring the speed back to a desired target value, there is always a clearly identifiable, characteristic course of the speed during the ignition for this process.

It is possible for a “characteristic” course to be determined or ascertained beforehand and then, if necessary, to be able to be defined on the basis of specific course parameters (gradient, amplitude, speed limit values, speed characteristics map, etc.). The information for such a course can be stored and thus serve as a reference for a comparison with current measurements or series of measurements during operation. From this it can be determined whether the current curve (approximately) has the properties of a “characteristic curve”, which can then lead to the “ignition” decision. For example, the curve may be characterized as follows: a rapid rise, on the order of 1% [percent], of an output speed followed by a rapid fall below the output speed and beyond Adjustment back to the initial speed, with the whole process taking place within about 1 s [second].

An increase in the rotational speed by at least 0.1% in less than 0.1 s is preferably interpreted by evaluation electronics as an indication that flames have ignited in the combustion chamber. Such rapid speed changes, in particular such characteristic curves of the speed, typically do not occur in other situations, since the drives of fans are not designed for such rapid changes.

The evaluation electronics particularly preferably evaluates the course of the rotational speed determined to check the function of a flame monitor or as a redundant measured value for another sensor for flame monitoring. This offers the possibility of checking the function of a flame monitor and even checking or calibrating its response time. A considerable gain in safety can be achieved here without additional instrumentation, because the proper functioning of a flame detector can be checked at least when the flames ignite, from which it can be concluded that the flame detector can also fulfill its function when the flames go out. Due to the quick and clear response of the fan speed to an ignition, this signal can also be used in parallel or as an alternative to that of a flame monitor to ensure that the fuel supply is switched off at an early stage if the ignition fails, which also means an increase in safety.

An arrangement for observing or monitoring the ignition of flames in a combustion chamber of a heater also contributes to solving the problem, the heater having a speed-controlled fan with which an air-fuel gas mixture is conveyed to the combustion chamber, with an ignition device for igniting the air-fuel gas mixture and with evaluation electronics being provided which are set up to recognize a characteristic course of a speed of the fan and from this to an ignition of flames and/or their time to close.

The evaluation unit is preferably set up to detect an increase in the speed of the fan by at least 0.1% over time in less than 0.1 s and to interpret it as an indication of ignition. The engine speed and/or its time derivation show a very characteristic curve that only occurs when there is an ignition.

A further aspect also relates to a computer program product comprising instructions which cause the arrangement described to carry out the method described. The transmitter requires a program and data to perform the ignition flame monitor function, both of which must be updated from time to time.

The explanations for the method can be used for a more detailed characterization of the arrangement, and vice versa. The arrangement can also be set up in such a way that the method is carried out with it.

Furthermore, the use of a speed or a speed profile of a fan for (reliable) identification of a flame ignition in a heating device is proposed. For further characterization of the use, the explanations for the method or the arrangement can be fully accessed.

Fig. 1:

ein Heizgerät mit Gebläse und Steuer- und Regeleinheit und

Fig. 2:

ein Diagramm zur Veranschaulichung des Effektes, den ein Zünden der Flammen auf das Gebläse hat.

A schematic embodiment of the invention, to which it is not limited, and the way the method works will now be explained in more detail with reference to the drawing. They represent:

Figure 1:

a heater with fan and control and regulation unit and

Figure 2:

a diagram illustrating the effect that ignition of the flames has on the fan.

1 1 shows a schematic of a heating device 1 designed in particular for operation with hydrogen as the fuel gas or with hydrogen-containing fuel gas. However, it can also be used for other fuel gases. The heater 1 has a fan 2 which supplies a burner 3 with air from an air supply 4 . A fuel gas from a fuel gas supply 6 is added to the air via a fuel gas valve 5 . A control and regulation unit 7 is connected to the fan 2 and the fuel gas valve 5 via data lines 13, so that a mixture suitable for ignition and/or continuous operation is generated and the settings made for this (e.g. speed of the fan 2 and Opening of the fuel gas valve 5) can be reported back.

During the combustion of this mixture in a combustion chamber 15, flames 16 are produced, the effect of which (and thus their presence) is observed using at least one sensor 10 at a measuring point 19. The sensor 10 serves as a flame detector and can be used to regulate the air/fuel ratio. An ionization measuring device, a UV sensor, a temperature sensor or another measuring system can be used, depending on the requirements of the respective heating device 1. The sensor 10 is also connected to the control and regulation unit 7 via a data line 13 tied together. The combustion chamber 15 is surrounded by a housing 8 in which heat exchanger surfaces are only indicated here. Combustion gases produced are discharged to the environment via an exhaust system 9 . To ignite the combustion, there is an ignition electrode 17 which is connected to an ignition controller 12 by means of an ignition line 14 . A display 18 (which can also be at a different location during remote maintenance) provides information about the status of the heater 1. In the present invention, evaluation electronics 11 (which can be integrated into the control and regulation unit 7) evaluate the course of the speed of the Blower or a parameter correlating therewith in order to recognize a characteristic behavior during the ignition of the combustion process.

It has been shown as in 2 it is illustrated that this speed n shows a significant behavior when flames 16 are ignited, namely a rapid increase in an easily measurable order of approx. 1% of the speed and a subsequent drop even below the initial speed before ignition. This effect is even greater with hydrogen fuel than with other fuel gases (while other types of flame safeguards may be less sensitive with hydrogen fuel gas), its progression can be easily seen, and ignition timing can be very precisely estimated from the beginning of the rise close. It is thus possible to implement the function of a flame monitor at least during ignition, as a result of which the function of sensor 10 can be checked and redundant measurement during ignition is made possible. The diagram shows the course of the speed n (left Y-axis in revolutions per minute) of the fan 2 at a constant speed before ignition (e.g. up to the 9th second after the start) as a function of the time t (x-axis). , a steep rise at ignition (from 9 seconds) with a maximum about 1% above an initial speed and a steep fall below the initial speed (up to 9.5 seconds), from where the speed of the Control and regulating unit 7 is regulated back to its target value (output speed). The speed of the reaction of the blower 2 to an ignition depends on the distance to the combustion chamber, but because of the high propagation speed of pressure surges in the mixture path, it is similar to that of other measuring systems. This can be seen by comparing the curve of the signal i (right Y-axis, ionization current in μA [microamps]) of an ionization measuring device (as sensor 10), which responds even somewhat later in the present exemplary embodiment.

The present invention makes it possible to check the function of a conventional flame monitor when a combustion process is ignited, or to provide a redundant measuring system in order to ensure that the ignition process runs reliably.

Reference List

1

heater

2

fan

3

burner

4

air supply

5

fuel gas valve

6

fuel gas supply

7

control and regulation unit

8th

Housing

9

exhaust system

10

sensor

11

evaluation electronics

12

ignition control

13

data lines

14

ignition wire

15

combustion chamber

16

Flames

17

ignition electrode

18

Advertisement

19

measuring point

n

Fan 2 speed [rpm]

i

ionization current [µA]

t

time [s]

Claims (9)

Method for observing or monitoring an ignition of flames (16) in a combustion chamber (15) of a heater (1), wherein a speed (n) of a fan (2) for supplying air-fuel gas mixture to the combustion chamber (15) is observed and from a course of the speed (n) an ignition of flames (16) in the combustion chamber (15) is concluded. Method according to Claim 1, in which an ignition of flames (16) in the combustion chamber (15) is inferred from a characteristic curve over time of the speed (n). Method according to Claim 1 or 2, in which an increase in the speed of at least 0.1% in less than 0.1 s is interpreted by evaluation electronics (11) as an indication of ignition of flames (16) in the combustion chamber (15). Method according to one of the preceding claims, in which the evaluation electronics (11) evaluate the characteristic progression of the speed (n) in order to check the function of a flame monitor. Method according to one of the preceding claims, in which the evaluation electronics (11) evaluate the characteristic course of the speed (n) as a redundant measured value for another sensor (10) for flame monitoring. Arrangement for observing or monitoring ignition of flames (16) in a combustion chamber (15) of a heater (1), the heater having a speed-controlled fan (2) with which an air-fuel gas mixture is conveyed to the combustion chamber (15). with an ignition device (12, 14, 17) for igniting the air/fuel gas mixture and with evaluation electronics (11) being provided which are set up to record a characteristic curve of a speed (n) of the fan (2). recognize and from this to conclude that flames (16) have ignited and/or their point in time. Arrangement according to Claim 6, in which the evaluation electronics (11) are set up to detect a time-related increase in the speed (n) of the fan (2) by at least 0.1% in less than 0.1 s and to interpret this as an indication of ignition. A computer program product comprising instructions which cause the arrangement according to any one of claims 6 or 7 to carry out the method according to any one of claims 1 to 5. Use of a speed or a speed profile of a blower (2) to identify a flame ignition in a heater (1).

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