Method and arrangement for detecting the ignition of flames in a combustion chamber of a heating device, and computer program product

Description

[0001] The invention relates to a method and a system 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 hydrogen-containing fuel gas. This applies not only to large systems, but also to wall-mounted water heating devices and, in general, to heating devices for heating buildings and / or providing hot water. Furthermore, the invention also relates to a related computer program product and a use.

[0002] In heating devices, simple and robust sensors for temperature, light or heat radiation, pressure, volume flow and the like are generally used to control the heaters and ensure their safe operation. One important task is to determine the presence of stable flames (a so-called flame monitor), another is to set a ratio of combustion air to fuel gas (lambda value) that is suitable for stable and environmentally friendly combustion.

[0003] If flames ignite properly, this is detected by at least one sensor in or near the combustion chamber, as is any (unexpected) extinction of the flames. Ionization measuring devices, temperature sensors, or optical sensors, e.g., for UV radiation, are used as sensors. The function of a flame detector can ensure that combustion always occurs when fuel gas is supplied, or shut down if the flames do not ignite or are extinguished.

[0004] EP 3 581 850 A1 discloses a method wherein, upon burner start-up, a faulty ignition is detected by the control device, optionally if an unexpected signal curve from the fan, the ignition electrode, and / or the ionization electrode is present. If certain deviations of the signal curve from the norm occur, the control device detects a faulty ignition. For example, if the expected constant fan speed drops, a fault is inferred.

[0005] The subsequently published EP 3 919 817 A1 also discloses methods and devices for detecting errors during the ignition of a burner for combustion of a mixture of air and fuel. A fan with a predeterminable target speed generates an air flow that is fed to the burner, and fuel is added to the air flow via a fuel valve with a predeterminable target position. During the ignition process by triggering ignition sparks, the speed of the fan and / or the position of the fuel valve are monitored by means of an ignition monitoring system. Characteristic changes are detected and stored or further processed as ignition errors.

[0006] For cost reasons and to keep the complexity of a heating device to a minimum, such flame detectors are very reliable, but are usually only present once, so that checking their function or redundancy of measuring systems is not always feasible.

[0007] On the other hand, heaters that use a fan to supply air and fuel gas are generally controlled by adjusting the fan speed and a fuel gas valve. The fan speed is therefore continuously measured and maintained at a desired value. When a heater is started, the fan is brought to a preset speed and maintained at that speed while the fuel gas valve is opened and an ignition sequence is initiated by an ignition control system.

[0008] 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 be able to determine the ignition of flames and / or the time of ignition in the described heating devices without additional instrumentation, independently of sensors present in or on the combustion chamber.

[0009] To achieve this object, a method and an arrangement, as well as a computer program product and a use according to the independent claims, serve. Advantageous embodiments and further developments of the invention are specified in the respective dependent claims. The description, particularly in conjunction with the drawings, illustrates the invention and provides further exemplary embodiments.

[0010] A method for observing or monitoring an ignition of flames in a combustion chamber of a heater designed with hydrogen as fuel gas or with hydrogen-containing fuel gas contributes to the solution of the problem, wherein a speed of a fan for supplying an air-fuel gas mixture to the combustion chamber is observed and an ignition of flames in the combustion chamber is inferred from a (temporal, in particular characteristic) profile of the speed, wherein an ignition of flames in the combustion chamber is inferred from a temporal, characteristic profile of the speed (n), wherein an increase in the speed of at least 0.1% in less than 0.1 s is interpreted by an evaluation electronics as an indication of an ignition of flames in the combustion chamber.

[0011] Measurements have shown that the fan speed is briefly influenced in a characteristic way by a type of pressure surge that occurs in the combustion chamber when the flames are ignited. This is easily detected because the speed is constantly monitored and controlled anyway. Although the control system attempts to quickly return the speed to a desired setpoint, a clearly identifiable, characteristic speed curve during ignition is always present.

[0012] It is possible for a "characteristic" curve to be determined or ascertained in advance and then, if necessary, defined based on specific curve parameters (gradient, amplitude, speed limits, speed map, etc.). The information for such a curve can be saved and thus serve as a reference for comparison with current measurements or measurement series during operation. From this, it can be determined whether the current curve (approximately) exhibits the properties of a "characteristic curve," which can then lead to the "ignition" decision. For example, the curve can be characterized as follows: a rapid increase in the order of 1% of an output speed, followed by a rapid drop below the output speed and subsequent adjustment back to the output speed, with the entire process taking place within approximately 1 second.

[0013] An increase in speed of at least 0.1% in less than 0.1 seconds is interpreted by evaluation electronics as an indication of flame ignition in the combustion chamber. Such rapid speed changes, especially such characteristic speed curves, do not typically occur in other situations, as fan drives are not designed for such rapid changes.

[0014] Particularly preferred is the evaluation electronics evaluating the determined speed curve to monitor the function of a flame detector or as a redundant measured value for another flame monitoring sensor. This offers the possibility of monitoring the function of a flame detector and even testing or calibrating its response time. A significant safety gain can be achieved without additional instrumentation because the proper function of a flame detector can be monitored at least during flame ignition, which allows the conclusion that the flame detector can still fulfill its function even when the flames are extinguished.Due to the fast and clear response of the fan speed to an ignition, this signal can also be used in parallel or alternatively to that of a flame detector to ensure that the fuel supply is shut off early in the event of a failure to ignite, which also means an increase in safety.

[0015] An arrangement for observing or monitoring an ignition of flames in a combustion chamber of a heater also contributes to the solution of the problem, wherein the heater has a speed-controlled fan with which an air-fuel gas mixture is conveyed to the combustion chamber, wherein an ignition device is provided for igniting the air-fuel gas mixture and wherein evaluation electronics are provided which are designed to recognize a characteristic profile of a speed of the fan and to deduce therefrom an ignition of flames and / or their time.

[0016] The evaluation unit is configured to detect a temporal increase in the fan speed of at least 0.1% in less than 0.1 s and interpret this as an indication of ignition. The speed and / or its temporal derivative exhibit a very characteristic curve that only occurs during ignition.

[0017] A further aspect also relates to a computer program product comprising instructions that cause the described arrangement to execute the described method. The evaluation electronics requires a program and data to perform the flame detector function during ignition, both of which must be updated occasionally.

[0018] The explanations of the procedure can be used to further characterize the arrangement, and vice versa. The arrangement can also be designed to carry out the procedure.

[0019] A schematic embodiment of the invention, to which it is not limited, and the functioning of the method will now be explained in more detail with reference to the drawing. They show: Fig. 1: a heater with fan and control and regulation unit and Fig. 2: a diagram illustrating the effect that ignition of the flames has on the fan.

[0020] Fig. 1 shows a schematic of a heater 1 designed specifically for operation with hydrogen as fuel gas or with hydrogen-containing fuel gas. However, it is also applicable 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 mixed with the air via a fuel gas valve 5. A control and regulating 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 purpose (e.g. speed of the fan 2 and opening of the fuel gas valve 5) can be reported back.

[0021] When this mixture is burned in a combustion chamber 15, flames 16 are created, the effect of which (and thus their presence) is monitored by at least one sensor 10 at a measuring point 19. The sensor 10 serves as a flame monitor 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 heater 1. The sensor 10 is also connected to the control and regulation unit 7 via a data line 13. The combustion chamber 15 is surrounded by a housing 8, in which heat exchanger surfaces (only indicated here) are located. The resulting combustion gases are discharged to the environment via an exhaust system 9. To ignite the combustion, an ignition electrode 17 is provided, which is connected to an ignition control 12 via an ignition line 14.A display 18 (which may also be located elsewhere in the case of remote maintenance) provides information about the status of the heater 1. In the present invention, an evaluation electronics 11 (which may be integrated into the control and regulation unit 7) evaluates the course of the speed of the fan or a parameter correlating therewith in order to detect a characteristic behavior during the ignition of the combustion process.

[0022] It has been shown how in Fig. 2It is illustrated that this rotational speed n exhibits significant behavior upon ignition of flames 16, namely a rapid increase in an easily measurable order of approximately 1% of the rotational speed and a subsequent decrease even below the initial rotational speed before ignition. This effect is even greater when hydrogen is used as the fuel gas than with other fuel gases (while other types of flame detectors may be less sensitive when hydrogen is used as the fuel gas), its course can be easily recognized, and the ignition time can be deduced very precisely from the start of the increase. This makes it possible to implement the function of a flame detector at least during ignition, whereby the function of the sensor 10 can be monitored and a redundant measurement during ignition is enabled.The diagram shows the curve of the speed n (left Y-axis in revolutions per minute) of the fan 2 as a function of time t (x-axis). It has a constant speed before ignition (e.g., up to second 9 after start), a steep rise during ignition (from second 9) with a maximum approximately 1% above an initial speed, and a steep drop below the initial speed (up to second 9.5), from where the speed is adjusted back to its setpoint (initial speed) by the control and regulation unit 7. The speed of the fan 2's response to ignition depends on the distance to the combustion chamber, but is similarly fast to other measuring systems due to the high propagation speed of pressure surges in the mixture path. This can be seen by comparing it with the curve of the signal i (right Y-axis, ionization current in µA [microamperes]) of an ionization measuring device (as sensor 10), which in the present exemplary embodiment even responds somewhat later.

[0023] The present invention makes it possible to check the function of a conventional flame detector during the ignition of a combustion process or to provide a redundant measuring system in order to ensure a safe ignition process. List of reference symbols

[0024] 1Heater 2Blower 3Burner 4Air supply 5Fuel gas valve 6Fuel gas supply 7Control and regulation unit 8Housing 9Exhaust system 10Sensor 11Evaluation electronics 12Ignition control 13Data lines 14Ignition line 15Combustion chamber 16Flames 17Ignition electrode 18Display 19Measuring point nSpeed of fan 2 [rpm] iIonization current [µA] tTime [s]

Claims

1. Method for observing or monitoring an ignition of flames (16) in a combustion chamber (15) of a heating appliance (1) with hydrogen as fuel gas or with hydrogen-containing fuel gas, wherein a rotational speed (n) of a fan (2) for supplying air-fuel gas mixture to the combustion chamber (15) is observed and an ignition of flames (16) in the combustion chamber (15) is inferred from a profile of the rotational speed (n) , wherein an ignition of flames (16) in the combustion chamber (15) is inferred from a characteristic progression of the rotational speed (n) over time, wherein an increase in the rotational speed by at least 0.1% in less than 0.1 s is interpreted by an electronic evaluation system (11) as an indication of an ignition of flames (16) in the combustion chamber (15) .

2. Method according to the preceding claim, wherein a faster speed change is detected than that for which a drive of the fan (2) is designed.

3. Method according to one of the preceding claims, wherein the characteristic curve of the rotational speed n comprises the following ranges: constant initial rotational speed before ignition, a rise in the order of about 1% of the rotational speed and a subsequent drop below the initial rotational speed, wherein the rise and drop last for about 0.5 seconds, and wherein the rotational speed is then regulated back to the setpoint value (initial rotational speed) .

4. Method according to one of the preceding claims, wherein the evaluation electronics (11) evaluates the characteristic curve of the rotational speed (n) for checking the function of a flame monitor.

5. Method according to claim 4, wherein the evaluation electronics (11) controls the function of the flame detector and checks or calibrates its response time.

6. Method according to one of the preceding claims, wherein the evaluation electronics (11) evaluates the characteristic curve of the rotational speed (n) as a redundant measured value to another sensor (10) for flame monitoring.

7. Arrangement for observing or monitoring an ignition of flames (16) in a combustion chamber (15) of a heating appliance (1) designed for operation with hydrogen as fuel gas or with hydrogen-containing fuel gas, wherein the heating appliance has a speed-controlled fan (2) with which an air-fuel gas mixture is conveyed to the combustion chamber (15), wherein an ignition device (12, 14, 17) for igniting the air-fuel gas mixture is present and wherein evaluation electronics (11) are present, which is set up to recognise a characteristic course of a rotational speed (n) of the fan (2) and to infer therefrom an ignition of flames (16) and / or their time and to recognise a temporal increase in the rotational speed (n) of the fan (2) by at least 0.1% in less than 0.1 s and to interpret it as an indication of an ignition, the arrangement being set up to carry out a method according to one of the preceding claims.

8. A computer program product comprising instructions which cause the arrangement according to claim 7 to perform the method according to any one of claims 1 to 6.