DE102023111435A1 - Method for preventing critical operating conditions of a heating device with pneumatic gas-air connection, heating device, computer program and computer-readable storage medium - Google Patents

Abstract

A method is proposed for preventing critical operating states of a heating device (1) with a pneumatic gas-air connection, wherein during operation of the heating device (1) a voltage signal (23, 24, 25, 26) of an ignition electrode (17) is recorded and compared with a limit voltage signal in order to determine a critical operating state. The method makes it possible in particular to prevent critical operating states due to low effective power of the heating device (1) with an at least partially blocked flow path when starting up low power of the modulation range. In addition, a heating device (1), a computer program and a computer-readable storage medium are proposed.

Description

The invention relates to a method for preventing critical operating states of a heating device with a pneumatic gas-air connection, a heating device, a computer program and a computer-readable storage medium.

Heating devices for the combustion of a fuel gas, such as natural gas or hydrogen, usually form a combustion mixture of fuel gas and combustion air with a predetermined combustion air ratio (also known as lambda or air ratio) and feed this to a burner for combustion. Such heating devices are also known as premix burners. Various methods are known for forming the combustion air ratio. Heating devices with a pneumatic gas-air connection record a reference pressure in the area of a throttle point in the combustion air supply, which allows a conclusion to be drawn about the supplied mass flow of combustion air. Using the reference pressure, the gas valve adds a mass flow of fuel gas corresponding to a predetermined combustion air ratio. Such a heating device is used, for example, in the EP 3 957 910 A1 described. The advantage of pneumatic mixture formation is that it does not require complex sensors and is therefore very robust in use and simple in construction.

In such heaters, the heating output is controlled or a modulation point is approached using the fan speed, which sets a mass flow of combustion air to be supplied. However, if the flow path is at least partially blocked, in particular an exhaust path is at least partially blocked, a significantly lower mass flow of combustion air can be conveyed than would normally correspond to the fan speed. This can lead to critical operating conditions, particularly in the low power range, as the heater may be operated with a mass flow of combustion air that is outside the modulation range. A flow sensor could provide a remedy. However, this has the disadvantage of increasing the complexity of the heater and requiring additional costs.

Based on this, the object of the invention is to propose a method for preventing critical operating states of a heating device with a pneumatic gas-air connection, a heating device and a computer program that at least partially overcome the problems of the prior art described. In particular, the occurrence of critical operating states should be prevented with a high degree of certainty.

In addition, the invention should at least not significantly increase the complexity of a heating device and require no or only minor structural changes to a heating device and enable easy integration into an existing production process.

These objects are achieved by the features of the independent patent claims. Further advantageous embodiments of the solution proposed here are specified in the independent patent claims. It is pointed out that the features listed in the dependent patent claims can be combined with one another in any technologically reasonable manner and define further embodiments of the invention. In addition, the features specified in the patent claims are specified and explained in more detail in the description, with further preferred embodiments of the invention being presented.

A method for preventing critical operating states of a heater with a pneumatic gas-air connection contributes to this. During operation of the heater, a voltage signal from an ignition electrode is recorded and compared with a limit voltage signal in order to determine a critical operating state. The voltage signal from the ignition electrode can be recorded directly or indirectly. Direct recording can be carried out in particular by measuring the electrical voltage. Indirect recording can be carried out by recording a voltage threshold using an integrated circuit.

The method can be carried out in particular continuously/permanently during operation of a heater with a pneumatic gas-air connection. The method can also be carried out only in a relevant power range (modulation range) of the heater, whereby a relevant power range can be a power range in which the occurrence of critical operating states, in particular due to an at least partially blocked flow path, is sufficiently likely. A relevant power range can be specified by a power threshold below which a critical power range is defined.

A critical operating state can in particular refer to the operation of the heater at a modulation point outside, in particular below, the intended modulation range of the heater. Thus, a critical operating state can also refer to the heater falling below a lower limit power, whereby the heater's power is limited to the The mass flow of combustion air supplied by the fan is used.

The heater can be a gas heater with a pneumatic gas-air connection. This can have a conveying device, in particular a fan, which can convey a mass flow (or volume flow) of combustion air. The combustion air can be supplied via a combustion air supply, with a control pressure (reference pressure) for the gas valve often being transmitted to the gas valve via a control line in an area between the fan and the throttle point. The gas valve can add a mass flow of fuel gas corresponding to the control pressure and a predetermined combustion air ratio. The heater can in particular be a wall-mounted heater and with condensing technology. Such a pneumatic gas-air connection advantageously enables a robust setting of a predetermined combustion air ratio, in particular since a mass flow of fuel gas occurs depending on the effectively flowing mass flow of combustion air. Starting up a low output by setting a predetermined speed of the conveyor device can, in the case of an at least partially blocked flow path, lead to an effective output of the heater that is below the output expected from the speed setting and the heater can therefore lead to potentially critical operating conditions, characterized by unstable flame formation with increased emissions of carbon monoxide.

The heater can comprise an ignition electrode which is designed to ignite combustion mixture emerging from the burner. For this purpose, an electrical ignition voltage can be applied to the ignition electrode, in particular between two pins of the ignition electrode, which leads to an ignition spark between the two pins. After an ignition process, the ignition voltage is usually switched off. One idea of the present invention is to record an electrical voltage signal from the ignition electrode and to derive an output of the heater from the voltage signal. An ignition electrode (or the evaluation electronics connected to it) is used in particular in heaters with a pneumatic gas-air connection and, unlike an ionization electrode, is not able to measure a combustion air ratio (also referred to as lambda, or excess air from combustion). For this purpose, an ionization electrode is usually longer than an ignition electrode and reaches closer to the burner surface than an ignition electrode. An idea or an advantage of the present invention can be seen in particular in the use of an ignition electrode to detect the output of the heater with a pneumatic gas-air connection and thus increase operational reliability. In particular, no structural changes to the heater with a pneumatic gas-air connection are necessary.

Due to the health risks associated with carbon monoxide, these must be minimized at all costs and this is often a legal approval requirement for heaters. The gas valve therefore usually has the option of setting an offset, i.e. a shift in the opening width corresponding to a control pressure over the entire opening range. To avoid carbon monoxide emissions, the offset is usually set to very low values, in the range of a minimum offset. This can disadvantageously result in a deterioration in combustion efficiency and unstable flame formation, particularly at low power levels. Setting the offset value of the gas valve therefore means weighing up flame stability and combustion efficiency with possible carbon monoxide emissions with increased flow resistance in the flow path of the heater.

Such a heater can adapt its heating output to a heat requirement, also known as modulation. This can be done within a modulation range specified for the heater. In order to avoid frequent switching on and off of the burner, which causes wear, modern heaters can be operated in a large modulation range, for example from 3.5 kW [kilowatts] to 18 kW.

The invention is based on the idea of recording a voltage signal from the ignition electrode during operation of the heater. This particularly applies to an operating phase after ignition and/or even (repeatedly or permanently) during the entire operation (i.e. combustion of fuel gas and air). The voltage signal is initiated by the flame and it has been determined that the voltage signal can be used to draw conclusions about the (current, effective) heating output of the heater, including a possible increased flow resistance of the heater's flow path. Critical operating states of the heater can therefore be determined using the voltage signal from the ignition electrode.

It is proposed to compare the voltage signal of the ignition electrode with a predetermined, possibly stored, limit voltage signal and, based on the result of the comparison, to determine at least one (predetermined/defined or characteristic) critical operating condition.

According to one embodiment, a critical operating state can be determined based on the heater falling below a lower limit power. The detected voltage signal of the ignition electrode can thus be compared with a predetermined limit voltage (of the ignition electrode) corresponding to the lower limit power and a critical operating state can be identified if the lower limit power is exceeded.

According to one embodiment, when it is determined that the lower limit power or the limit voltage signal is not being undershot, the heater can (automatically) adapt its modulation range in such a way that the lower limit power is not being undershot. In particular, the minimum fan speed to be started by the heater can be increased (directly) in such a way or (continuously) to such an extent that critical operating states, in particular insufficient effective heating power, are avoided.

According to one embodiment, when a critical operating state is detected, the heater can display information on this via a display device, make it available for retrieval via a network and/or send it as a message, put the heater into emergency mode and/or take the heater out of operation. Information can be provided and/or sent as a message in particular via the Internet. A user or a service company can thus advantageously be informed of the occurrence of a critical operating state. The service company could advantageously plan or carry out a timely appointment for inspection or repair. The emergency operation of the heater could limit operation to a particularly safe performance range.

According to a further aspect, a heating device is also proposed, comprising at least one fan for conveying a mass flow of combustion air, a venturi device, an ignition electrode and a gas valve. The heating device can form a pneumatic gas-air connection.

The heater can in particular have a control and regulating device, which can also be set up to carry out a method proposed here. For this purpose, the control and regulating device can be electrically connected at least to the ignition electrode and the fan. For this purpose, the control and regulating device can, for example, have a processor and/or have one. In this context, the processor can, for example, carry out the method stored in a memory (of the control and regulating device). In addition, data recorded or required as part of the implementation of a method proposed here can be stored in a memory of the control and regulating device, for example a limit voltage signal and/or a lower limit power.

According to a further aspect, a computer program is also proposed which is set up to (at least partially) carry out a method presented here on a heating device proposed here. In other words, this relates in particular to a computer program (product) comprising commands which, when the program is executed by a computer, cause the computer to carry out a method proposed here. The computer program can in particular be carried out on a control device of a heating device proposed here.

According to a further aspect, a computer-readable storage medium is also proposed on which a computer program proposed here is stored.

The details, features and advantageous embodiments discussed in connection with the method can also occur in the computer program, the heating device, the computer program and/or the computer-readable storage medium presented here and vice versa. In this respect, reference is made in full to the explanations there for a more detailed characterization of the features.

A method for preventing critical operating states of a heating device with a pneumatic gas-air connection, a heating device, a computer program and a computer-readable storage medium are therefore specified here, which at least partially solve the problems described with reference to the prior art. In particular, the method, the heating device and the computer program help to detect and prevent the occurrence of critical operating states of a heating device with a pneumatic gas-air connection.

In addition, the invention can be implemented without structural changes to a heater and is therefore also ideally suited for retrofitting existing heaters.

• 1: ein hier vorgeschlagenes Heizgerät, und
• 2 und 3: Parameterverläufe, die sich bei Durchführung eines hier vorgeschlagenen Verfahrens einstellen können.

The invention and the technical environment are explained in more detail below with reference to the accompanying figures. It should be noted that the invention is not intended to be limited by the exemplary embodiments given. In particular, Unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and to combine them with other components and findings from the present description. In particular, it should be noted that the figures and in particular the size relationships shown are only schematic. They show:

• 1 : a heater proposed here, and
• 2 and 3 : Parameter curves that can occur when carrying out a procedure proposed here.

1 shows, by way of example and schematically, a heating device 1 proposed here. This can have an air supply 4 for combustion air. A venturi device 15 can be arranged in the air supply 4. Viewed in a flow direction 16 of the heating device 1, a conveying device 2 designed as a fan can be arranged upstream of the venturi device 15, which can convey a mass flow of combustion air. A gas valve 5 can add a mass flow of fuel gas to the mass flow of combustion air conveyed by the conveying device 2 in the area of the venturi device 15, in particular in the venturi device 15. The mixture of fuel gas and combustion air can be fed to a burner 3 via a mixture channel 12 and burned there. A heat exchanger 13 can be arranged on the burner 3, which can transfer heat generated during combustion to a heating circuit 14 with a flow line 6 and a return line 9.

Downstream of the burner 3, an exhaust pipe 10 can feed combustion products to an exhaust system 11. A regulating and control device 7 of the heating device 1 can be electrically connected at least to the gas valve 5 and the conveying device 2.

An ignition electrode 17 can be arranged on the burner 3, designed to form an ignition spark in order to ignite the combustion mixture emerging from the burner 3.

According to a method proposed here, a voltage signal of the ignition electrode 17 can be detected during operation of the heater 1.

2 shows exemplary and schematic curves 19, 20, 21, 22 of the combustion air ratio based on the modulation range of the heater 1. A first curve 19 represents the combustion air ratio (lambda) set by the heater 1 with minimal offset of the gas valve 5 and without restriction of the flow through the heater 1 (without (partial) blockage of the flow path). A second curve 20 shows the combustion air ratio (lambda) set by the heater 1 with maximum offset of the gas valve 5 and without restriction of the flow through the heater 1 (without (partial) blockage of the flow path). A third curve 21 shows the combustion air ratio with a minimum offset of the gas valve corresponding to the first curve 19, but now with restricted flow through the heater 1, i.e. with an increased flow resistance of the flow path of the heater 1. A fourth curve 22 shows the combustion air ratio with a maximum offset of the gas valve 5 with restricted flow through the heater 1. It can be seen that the curve with a minimum offset of the gas valve 5 can enter a (physically determined) critical area 18, which is characterized by unstable flame formation with increased formation of carbon monoxide (and thus critical operating conditions). Entering the critical area 18 can lead to failure in a test of a blockage of the exhaust system (exhaust pipe 10 and/or exhaust system 11). Such tests are often an approval requirement for a heater 1.

3 shows curves 23, 24, 25, 26 of the voltage signal U _Z of the ignition electrode 17. A first curve 23 of the voltage signal U _Z represents the detected voltage of the ignition electrode 17 with minimal offset of the gas valve 5 and without restriction of the flow through the heater 1 (without (partial) blockage of the flow path). A second curve 24 shows the voltage signal at maximum offset of the gas valve 5 with restricted flow through the heater 1. A third curve 25 shows the voltage signal U _Z with minimal offset of the gas valve 5 without restricted flow through the heater 1 and a fourth curve 26 shows the voltage signal U _Z with minimal offset of the gas valve 5 and with restricted flow through the heater 1. It is clear that the fourth voltage curve U _Z 26 achieves a lower output as a result of the minimal offset of the gas valve 5 and the restricted flow through the heater 1. The curves 23, 24, 25, 26 thus allow a conclusion to be drawn about the effective performance of the heater 1.

When carrying out a method proposed here, the effective power Q of the heater 1 can be determined by detecting a voltage signal U _Z of the ignition electrode 17. By comparing the detected voltage signal U _Z with a limit voltage signal 8, the heater 1 can be prevented from entering a critical range 18.

As a precaution, it should be noted that the numerals used here ("first", "second", ...) primarily serve (only) to distinguish between several similar objects, sizes or processes, and in particular do not necessarily specify a dependency and/or sequence of these objects, sizes or processes. If a dependency and/or sequence is required, this is explicitly stated here or it is obvious to the person skilled in the art when studying the specifically described design. If a component can occur multiple times ("at least one"), the description of one of these components can apply equally to all or part of the majority of these components, but this is not mandatory.

list of reference symbols

1

heater

2

conveyor system

3

burner

4

air supply

5

gas valve

6

lead time

7

control unit

8

limit voltage signal

9

return

10

exhaust pipe

11

exhaust system

12

mixture channel

13

heat exchanger

14

heating circuit

15

Venturi device

16

flow direction

17

ignition electrode

18

critical area

19

first course of combustion air ratio

20

second course of combustion air ratio

21

third course combustion air ratio

22

fourth curve combustion air ratio

23

first course of the voltage signal

24

second voltage signal curve

25

third course voltage signal

26

fourth course voltage signal

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 accepts no liability for any errors or omissions.

Cited patent literature

• EP 3957910 A1 [0002]

Claims (7)

Method for preventing critical operating states of a heater (1) with a pneumatic gas-air connection, wherein during operation of the heater (1) a voltage signal (23, 24, 25, 26) of an ignition electrode (17) is detected and compared with a limit voltage signal in order to determine a critical operating state. procedure according to claim 1 , wherein a critical operating state is determined based on the detected voltage signal (23, 24, 25, 26) of the ignition electrode (17) of the heater (1) falling below a predetermined lower limit voltage signal 8). procedure according to claim 2 , wherein the heater (1), when it detects that the limit voltage (8) has been undershot, adapts its modulation range in such a way that the lower limit voltage (8) is not undershot. Method according to one of the preceding claims, wherein the heater (1), when a critical operating state is detected, displays information on this via a display device, makes it available for retrieval via a network or sends it as a message, puts the heater (1) into emergency operation and/or takes the heater (1) out of operation. Heating device (1), comprising a conveying device (2) for conveying a mass flow of combustion air, a Venturi device (15), an ignition electrode (17), a gas valve (5) and means adapted to carry out the steps of a method according to one of the Claims 1 until 4 carry out. Computer program comprising commands which cause a heating device (1) to claim 5 a procedure according to one of the Claims 1 until 4 executes. Computer-readable storage medium on which a computer program is claim 6 is stored.

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