Method and burner device

Abstract

The invention relates to a method for calibrating a flame monitoring device (10) for a burner device that can be operated at a predetermined power output, in which fuel is supplied to the burner device (12) to generate a flame (14) by means of a measuring signal (56) and in which an ambient air flow (16) is supplied to the burner device (12) to generate a fuel-oxygen mixture, wherein in at least one calibration step (38, 40) a combustion maximum (20) of the flame (14) is exceeded, in which a rich fuel-oxygen mixture is generated at least in the calibration step (38, 40). It is proposed that, as the flame monitoring device (10) ages, the evaluation method changes from a double peak to a switching peak.The invention also relates to a burner device (12) which is at least configured to calibrate the flame monitoring device (10) by means of the method.

Description

State of the art

[0001] A method for calibrating a flame monitoring device has already been proposed, in which a fuel is supplied to a burner device to generate a flame and in which an ambient air stream is supplied to the burner device to generate a fuel-oxygen mixture, whereby a combustion maximum of the flame is exceeded in at least one calibration step. Disclosure of the invention

[0002] The invention relates to a method for calibrating a flame monitoring device for a burner device that can be operated at a predetermined power by means of a measuring signal, in which fuel is supplied to the burner device to generate a flame and in which an ambient air stream is supplied to the burner device to generate a fuel-oxygen mixture, wherein in at least one calibration step a combustion maximum of the flame is exceeded, in which at least in the calibration step a rich fuel-oxygen mixture is generated.

[0003] The method is characterized by the fact that, as the flame monitoring device ages, the evaluation changes from a double peak to an alternating peak.

[0004] The inventive design of the method advantageously addresses aging. As the components of the flame monitoring device age, the internal resistance of the system generally increases. This can render the measurement signal originally used for calibration unusable. The original measurement signal is typically a double peak, which clearly indicates when the rich region has passed through. According to the invention, if the double peak is absent or no longer clearly evaluable, the system switches to an alternating peak. This can then be used to precisely determine the calibration position. The alternating peak may develop automatically depending on the age of the system. However, parameters such as bias voltage, gain, and / or a preselected current density can also be adjusted so that the system switches to the alternating peak.

[0005] The alternating peak can initially decrease from a base measurement level, and then, over time, rise above the base measurement level.

[0006] The alternating peak can initially rise from a base measurement level, and then, over time, fall below the base measurement level.

[0007] A baseline measurement level is understood to be a value of a parameter to be measured, as measured in normal use or before calibration. The parameter can be, in particular, a voltage, a current, a resistance, a capacitance, an inductance, or the like.

[0008] The measurement becomes accurate or unambiguous if a first drop or exceedance is at least so large that the measurement signal (56) deviates noticeably from a current level (67), in particular by at least 10%, preferably by 15% compared to the current level (67).

[0009] A discernible deviation is understood to mean that the measurement signal, which is usually superimposed with noise, at least emerges from the noise signal range and can be determined, or that a shape of the measurement signal can be determined.

[0010] A rich fuel-oxygen mixture can be easily generated if the ambient airflow is reduced for the calibration step.

[0011] A rich fuel-oxygen mixture can be easily produced if the fuel supply is increased in at least one calibration step (38).

[0012] The calibration procedure can be carried out quickly if a rich fuel-oxygen mixture is generated in at least one calibration step for a predetermined pulse duration.

[0013] A duration is understood to mean that the step or process is limited in time. It refers to a specific period of time during operation, particularly continuous operation of the burner device, within which the defined duration lies. The duration has a start time and a subsequent end time. Continuous operation is understood to mean operation during which the burner device operates under normal conditions. This can occur at a constant power output or at an output adapted to normal use.

[0014] Preferably, the flame monitoring device comprises at least one ionization sensor. Alternatively or additionally, the flame monitoring device could also comprise at least one lambda probe or a temperature sensor and / or a comparable direct and / or indirect measuring method for measuring combustion quality. Preferably, the burner device is designed as an instantaneous water heater and / or boiler. In particular, the burner device heats water. Preferably, thermal energy is supplied to the water by the burner device, in particular by a burner of the burner device. Preferably, the thermal energy is generated by the flame. Preferably, the fuel is designed as a fuel fluid, in particular as a fuel gas. For example, the flame could be generated by the oxidation of fuel, in particular natural gas and / or hydrogen and / or methane.Preferably, the fuel is introduced into the burner of the burner device. Preferably, the fuel is injected into the burner under pressure, for example, by a pump. Preferably, the ambient air stream contains at least oxygen. Preferably, the ambient air stream is generated by drawing in ambient air with a blower. Preferably, the ambient air stream is introduced into the burner of the burner device. Preferably, the blower generates a pressure in the burner that is greater than the ambient pressure. Preferably, the fuel, particularly in the burner, is mixed with the ambient air stream. Preferably, a fuel-oxygen mixture is generated. The fuel-oxygen mixture has a specific mixing ratio. This mixing ratio is defined as the ratio of fuel to oxygen.Preferably, the fuel is oxidized / combusted with at least the oxygen from the ambient air stream, for example, in the burner. A "rich fuel-oxygen mixture" is understood to mean, in particular, a mixture ratio that contains less oxygen than is required for complete combustion / oxidation of the fuel. An "ionization sensor" is understood to mean, in particular, at least one measuring sensor, for example, an ionization electrode, which is configured to measure an ionization current. Specifically, an electrical voltage is applied to the flame, for example, between the housing and the ionization sensor, from which the ionization current is generated, particularly when a flame is present. Preferably, the ionization current depends at least on a certain flame intensity. Preferably, the ionization current increases with the flame intensity.Preferably, the ionization current is at least substantially maximal at the combustion maximum. Preferably, the ionization current decreases as the flame intensity decreases when the combustion maximum is exceeded, which occurs particularly with a rich fuel-oxygen mixture. For example, a combustion maximum could be reached at least substantially at a stoichiometric mixture ratio. For example, the flame intensity is lower with a leaner and / or a richer fuel-oxygen mixture than at the combustion maximum with stoichiometric combustion. "Stoichiometric" here refers in particular to a fuel-oxygen mixture that contains exactly the same amount of oxygen as is theoretically required for the oxidation of the fuel contained in the fuel-oxygen mixture.

[0015] Preferably, the fuel-oxygen mixture is enriched until the combustion maximum of the flame is exceeded. Preferably, the ion formation rate in the flame is at least substantially maximal at the combustion maximum. Preferably, the fuel-oxygen mixture is burned stoichiometrically at the combustion maximum. In particular, the combustion temperature is maximal at least substantially at the combustion maximum. In particular, the combustion maximum must be exceeded in order to identify it. Preferably, the rich fuel-oxygen mixture is burned, especially along an increasing mixture ratio, in which at least one calibration step occurs at least substantially above the combustion maximum.

[0016] Preferably, the calibration step comprises at least one pulse step and one evaluation step. Preferably, in the pulse step, the mixture ratio of the fuel-oxygen mixture is increased over a pulse duration, particularly of less than 5 s, preferably less than 1 s, and preferably less than 0.5 s. Preferably, in the evaluation step, following the pulse step, at least one pulse response is measured and evaluated over an evaluation period. Preferably, the evaluation period is at least substantially the same length as the pulse duration. Preferably, the total duration of the calibration step is less than 20 s, more preferably less than 10 s. In particular, the total duration of the calibration step is at least twice the pulse duration.In this context, "combustion maximum" is understood to mean, in particular, the oxidation of a fuel-oxygen mixture at a mixing ratio that results in a maximum measurement signal from the ionization sensor and / or a maximum combustion temperature. "At least substantially" in this context is understood to mean, in particular, that the deviation from a predetermined value is less than 25%, preferably less than 10%, and most preferably less than 5% of the predetermined value.

[0017] It is proposed that the changing of the peak shape to be evaluated and its evaluation be carried out using software that controls or regulates the burner device.

[0018] Furthermore, it is proposed that changing the peak shape to be evaluated and its evaluation is part of a software module that controls or regulates the calibration.

[0019] A preferred embodiment is a burner device comprising at least one flame monitoring device with at least one blower configured to supply an ambient airflow to the burner, at least one fuel supply valve configured to adjust the fuel quantity, and at least one control and / or regulating unit configured to calibrate the flame monitoring device using the method according to the invention. Advantageously, a high level of user comfort can be provided, as temperature fluctuations can be reduced / limited, particularly during the calibration step. Advantageously, a cost-effective design can be provided, as no additional components are required to implement the method. Preferably, the flame monitoring device includes at least one ionization sensor.

[0020] In a simple process, the ambient airflow is advantageously reduced in at least one calibration step for generating the rich fuel-oxygen mixture. A high level of comfort can be advantageously provided, as temperature fluctuations can be reduced / limited, in particular, by reducing the ambient airflow. Preferably, the rich fuel-oxygen mixture is generated by reducing the oxygen content of the fuel-oxygen mixture. Specifically, the rich fuel-oxygen mixture is generated by increasing the mixing ratio. Preferably, the ambient airflow is reduced by supplying less ambient air to the burner with the same amount of fuel. For example, the ambient airflow could be reduced by decreasing the cross-sectional area of ​​an ambient air duct in the burner assembly. Alternatively, a bypass valve could be opened.

[0021] Furthermore, it is advantageous to generate the rich fuel-oxygen mixture by reducing the blower speed. A cost-effective design can be provided, as no additional components are required, particularly for calibration. Preferably, the blower speed is reduced by specifying at least one reduced blower speed and a duration for that reduced speed. It is conceivable that a duration, particularly a maximum duration, is specified for the reduction of the blower speed. Specifically, the blower speed is not reduced below a minimum during at least one calibration step. For example, the difference between the initial speed and the reduced speed could be defined as a pulse height.For example, the time between the start time of the reduction of the fan speed and reaching the reduced fan speed could be designed as a holding time.

[0022] The calibration method and the burner device according to the invention are not to be limited to the application and embodiment described above. In particular, the calibration method and the burner device according to the invention may, to achieve a functionality described herein, comprise a different number of individual elements, components, units, and process steps than those specified herein. Furthermore, values ​​within the specified limits of the value ranges stated in this disclosure are also to be considered disclosed and freely usable. drawing

[0023] Further advantages will become apparent from the following description of the drawing. The drawing illustrates an embodiment of the invention. The drawing, the description, and the claims contain numerous features in combination. A person skilled in the art will expediently consider the features individually and combine them into meaningful further combinations.

[0024] They show: Fig. 1 a burner device with a flame monitoring device, Fig. 2 a schematic flow diagram of a method for calibrating the flame monitoring device, Fig. 3 a schematic calibration diagram and Fig. 4 an alternating pulse. Description of the exemplary embodiment

[0025] The Figure 1 Figure 1 shows a burner device 12. The burner device 12 is designed to heat water in an instantaneous water heater or boiler or the like.

[0026] The burner device 12 includes a flame monitoring device 10. The flame monitoring device 10 includes an ionization sensor 52. The ionization sensor 52 is configured to generate a measurement signal 56, see figure. Fig. 3 The measurement signal is in the form of an ionization current.

[0027] The burner assembly 12 includes a blower 26. The burner assembly 12 includes a burner 28. The blower 26 is configured to supply an ambient air flow 16 to the burner 28. The burner 28 and the blower 26 are fluidically connected to each other via an ambient air duct 24.

[0028] The burner device 12 has a fuel supply valve 30. The fuel supply valve 30 is configured to supply fuel to the burner 28. The fuel is in the form of a fuel gas. The fuel gas could be natural gas, methane, hydrogen, or the like. The fuel supply valve 30 is configured to adjust a fuel supply 34.

[0029] The burner 28 has a fuel-oxygen mixture. The fuel-oxygen mixture has a mixing ratio of 54, see [reference]. Fig. 3 The mixture ratio 54 is defined as the ratio of fuel to oxygen. The burner 28 is designed to burn the fuel-oxygen mixture. The burner 28 is designed to produce a flame 14.

[0030] The burner device 12 includes a control and / or regulating unit 32. The control and / or regulating unit 32 is configured to calibrate the flame monitoring device 10 using the method described. The burner device 12 includes a fuel tank 18. The fuel tank 18 is designed as a gas cylinder. However, the fuel tank 18 could also be designed as a public fuel network or the like.

[0031] The Figure 2 shows a schematic flowchart of a procedure for calibrating the flame monitoring device 10.

[0032] In at least one preparatory step 36, an operating parameter is determined. The operating parameter is retrieved / read by the control unit 32. The operating parameter is configured as a fan speed. Alternatively or additionally, the operating parameter could be configured as a pressure in a combustion chamber 22 of the burner device 12 and / or in the ambient air duct 24 of the burner device 12. Alternatively or additionally, the operating parameter could also be configured as a mixture ratio 54 of the fuel-oxygen mixture during normal operation of the burner device 12. The operating parameter has a limit value. Based on the limit value, a decision is made as to whether a further calibration step 38 or a further calibration step 40 is performed.

[0033] In at least one further calibration step 38, a calibration pulse 60 is generated, cf. Fig. 3The calibration pulse 60 is generated by setting a rich fuel-oxygen mixture ratio 54. In the exemplary embodiment according to Figure 3A rich fuel-oxygen mixture is generated for a pulse duration 44 of 0.1 s. Alternatively, the pulse duration 44 could also be greater than 0.1 s. The rich fuel-oxygen mixture is set based on a pulse height 58 of the calibration pulse 60. The fuel-oxygen mixture is enriched from a normal operating state. In the exemplary embodiment, the ambient airflow is reduced to generate the rich fuel-oxygen mixture. The ambient airflow is reduced by decreasing the blower speed. The ambient airflow is reduced to enrich the fuel-oxygen mixture when the operating parameter is at least at the limit value. After the pulse duration 44 of 0.1 s, the ambient airflow is reset to the value of the normal operating state. In at least one calibration step 38, the fuel supply 34 is kept constant.

[0034] In at least one further calibration step 40, if the limit value is undershot, the rich fuel-oxygen mixture is produced by increasing the fuel supply 34, cf. Fig. 1 In at least one further calibration step 40, it is ensured that the mixing ratio 54 can be increased sufficiently in each calibration state to achieve a combustion maximum 20 of the flame 14. In at least one further calibration step 40, the blower speed is kept constant. In at least one further calibration step 40, the ambient airflow 16 is kept constant.

[0035] In at least one evaluation step 42, the combustion maximum 20 of the flame 14 is detected. The detected measurement signal 56 is evaluated by the control unit 32. The combustion maximum 20 of the flame 14 is reached after the pulse duration 44 has elapsed. The combustion maximum 20 is generated with a time offset from the calibration pulse 60. Alternatively, it is conceivable that the combustion maximum 20 of the flame 14, for example with a long pulse duration 44, is reached during the calibration pulse 60.

[0036] The Figure 3Figure 1 shows a schematic calibration diagram. The schematic calibration diagram shows a schematic curve of the measurement signal 56 from the ionization sensor 52. Furthermore, the schematic calibration diagram shows a schematic curve of a mixture ratio 54 of the fuel-oxygen mixture over a calibration period 50. The schematic calibration diagram has an ordinate 46. The measurement signal 56 of the ionization sensor 52 is plotted on the ordinate 46. The measurement signal 56 is represented as the ionization current detected by the ionization sensor 52. Furthermore, the mixture ratio 54 of the fuel-oxygen mixture is plotted on the ordinate 46. The schematic calibration diagram has an abscissa 48. Time is plotted on the abscissa 48. The calibration pulse 60 has a pulse height 58 of the mixture ratio 54. The pulse duration 44 of the calibration pulse 60 is 0.1 s.It is conceivable that the pulse duration 44 is more or less than 0.1 s. The pulse duration 44 can have different values. Once preselected, it is fixed. It can be preselected depending on various influences and parameters. Such influences and parameters include, for example, the fuel-oxygen mixture ratio 54 during normal operation or the current power output. The pulse duration 44 is less than 2 s in every calibration state.

[0037] Alternatively, the pulse duration 44 is less than 5 s in each calibration state. The combustion maximum 20 of the flame 14 occurs at a time offset from the pulse duration 44. The measurement signal 56 of the ionization sensor 52 is generated after the pulse duration 44. The total calibration duration 50 is 1 s. The total calibration duration 50 is less than 10 s in each calibration process. The total calibration duration 50 is at least twice the pulse duration 44 in each calibration process. 60' and 58' denote the next calibration process.

[0038] In a modern burner device 12, the calibration process is carried out such that, with a constant valve position of the fuel supply valve 30, the blower speed of the blower 26 is reduced. This has the advantage that the output of the burner device is not changed or only changed very slightly.

[0039] A rich mixture can also be created by slightly opening the fuel supply valve 30 and thus supplying more fuel than is necessary for the current combustion.

[0040] Particularly with such a calibration, the combustion maximum 20 of the flame 14 can no longer be reliably detected as the device ages. Figure 3 A measurement signal 56 of a new or not yet significantly aged burner device 12 or flame monitoring device 10 is shown.

[0041] This measurement signal 56 can change over time with increasing aging. It can then take on a signal shape such as that shown in Figure 4 This is shown. Such a signal shape can no longer be clearly assigned to the original signal shape. This makes optimal calibration difficult, if not impossible.

[0042] In Figure 4The abscissa is a timeline, over which the measurement signal 56 is plotted on the ordinate. Typical units are milliseconds for the timeline and microamperes for the ordinate.

[0043] The invention assumes that with increasing aging of the flame monitoring device 10, the evaluation of a double peak 62, as exemplified in Figure 3 The text then switches to an evaluation of a switching peak 64, as exemplified in Figure 4 The exact shape of the process depends in each individual case on the precise design of the burner device 12 and the aging conditions.

[0044] Depending on the current burner setting, a double peak 62 may still be present and the combustion maximum 20 may or may not be detected. Especially at low outputs, the double peak 62 may no longer be present in the measurement signal.

[0045] In the exemplary embodiment, the control unit 32 detects that the combustion maximum 20 can no longer be uniquely determined. This can occur because, despite the calibration process having been started, no combustion maximum 20 appears within a foreseeable time. This process can be carried out multiple times to ensure that the combustion maximum 20 cannot be determined.

[0046] If it is detected that the combustion maximum 20 is not reached, the control unit 32 switches from an evaluation of a double peak 62 to an evaluation of an alternating peak 64.

[0047] Such a switch or change can also be initiated externally. This can be done, for example, via the internet.

[0048] The calibration process is started. To evaluate the switching peak 64, an initial deviation 66 of the measurement signal 56 from the ionization sensor 52 is monitored, starting from a level 67 that characterizes the current power for a given mixture. If the initial deviation 66 reaches a target value, it is monitored whether a first switching 68 of the measurement signal 56 can be observed. Further monitoring should reveal a second deviation 70, which is observable in contrast to the first deviation 66. A further monitoring should then reveal a second switching 72 with a third deviation 74. If such deviations 66, 70, 74 and switching 68, 72 are observable, a complete switching peak is concluded, and calibration can be performed.

[0049] Calibration can then be performed using either the first change 68 or the second change 72. It is also conceivable to use both changes 68 and 72 for calibration.

[0050] Typically, a switching peak 64 will develop such that the first deviation 66 shows a decrease in the measurement signal 56 starting from level 67. The first change 68 then represents a local minimum. The second deviation 70 represents a rise in the measurement signal 56. The measurement signal 56 rises above the original level 67 until the second change 72, which represents a local maximum. Via the subsequent falling third deviation 74, the measurement signal 56 moves back towards the original level 67. This level 67, which characterizes the original power with the set mixture, is reached either approximately asymptotically or with an overshoot and undershoot curve.

[0051] A switching peak of 64 can also occur in this way (not explicitly shown, but corresponds to a sealing of the Figure 4 (on the abscissa), that the first deviation shows an increase in the measurement signal 56. The first change then represents a local maximum. The second deviation 70 represents a decrease in the measurement signal 56. The measurement signal 56 falls below the original level 67 until the second change, which represents a local minimum. Via the then increasing third deviation, the measurement signal 56 moves again towards the original level 67. This level 67, which characterizes the original power with the set mixture, is reached either approximately asymptotically or with an overshoot and undershoot curve.

[0052] In the exemplary embodiment according to Figure 4A clear drop in the measurement signal 56 from the original level 67 is noticeable. Such a signal can be clearly evaluated. A signal deviation of at least 10% is desirable to enable clear detection of a calibration process and unambiguous evaluation of the measurement signal 56. Preferably, the flame monitoring device 10 should be configured to achieve a deviation of 15%. Adjustable parameters for this include, among others, the magnitude of the applied measurement voltage, signal amplification, and noise reduction.

[0053] In the exemplary embodiment, in a first variant, the ambient airflow 16 is reduced to generate the rich fuel-oxygen mixture. The valve position of the fuel supply valve 30 is kept at least approximately constant. This is a very elegant method that can be achieved by simply reducing the blower speed. The output of the burner device remains almost constant.

[0054] In another variant, the fuel supply valve 30 is opened slightly further to generate the rich fuel-oxygen mixture. The blower speed is kept approximately constant. This enriches the mixture, meaning it is supplied with excess fuel for combustion. It also slightly increases the power output. This method is used when the burner is operating at a lower power output and the measurement signal 56 might be difficult to evaluate.

[0055] Both process variants can also be combined. They can be applied sequentially. This increases the likelihood of obtaining a usable signal. The process variants can also be applied together. The aim is to ensure that at least a reduction in the supplied ambient airflow 16 predominates, or that an increase in the fuel supply 34 predominates.

[0056] In the exemplary embodiment, the method is carried out such that the fuel-oxygen mixture ratio 54 is enriched only for a short pulse duration. Due to the mixture transit time within the system, the system reacts with a slight delay, which in Figure 3 As indicated, the double peak 62 or the alternating peak 64 arrive late.

[0057] The pulse duration 60 is predetermined in the exemplary embodiment. However, it can also depend on actual conditions, such as power, signal strength or the age of the burner device 12.

[0058] In a process not shown, the mixture is continuously enriched over a period of time, so that the measurement signal is quasi-continuously tracked.

[0059] The method is stored in the control unit 32. In the exemplary embodiment, it is executed in the form of software. The software accesses memory, processors, and other components of the control unit 32. The control unit 32 is configured accordingly. It has the components necessary, for example, to correctly evaluate the measurement signal 56 or to perform process steps such as initiating calibration and checking whether an evaluable double pulse can be detected or whether it is necessary to switch to evaluating an alternating pulse.

[0060] In this exemplary embodiment, the software is stored as individual modules in the control unit 32. This has the advantage that individual modules, such as those responsible for the fuel enrichment of the burner device 12, need to be replaced due to aging. This creates a combinatorial effect that directly influences the method according to the invention, which is particularly relevant in an aging system.

Claims

1. Method for calibrating a flame monitoring device (10) for a burner device operable at a predetermined power output by means of a measuring signal (56), in which fuel is supplied to the burner device (12) to generate a flame (14) and in which an ambient air flow (16) is supplied to the burner device (12) to generate a fuel-oxygen mixture, wherein in at least one calibration step (38, 40) a combustion maximum (20) or a combustion minimum of the flame (14) is exceeded or fallen below, in which at least in the calibration step (38, 40) a rich fuel-oxygen mixture is generated, characterized by the fact As the flame monitoring device (10) ages, the evaluation changes from a double peak (62) to a single alternating peak (64).

2. Method according to claim 1, characterized by the fact thatThe alternating peak shows, in temporal sequence, first a drop below a base measurement level and then an exceedance of the base measurement level.

3. Method according to claim 1, characterized by the fact that The alternating peak shows, in temporal sequence, first an exceedance of a base measurement level and then a drop below the base measurement level.

4. Method according to any one of the preceding claims, characterized by the fact that a first drop or the first exceedance is at least so large that the measurement signal (56) deviates noticeably from a current level (67), in particular by at least 10%, preferably by 15% compared to the current level (67).

5. Method according to any one of the preceding claims, characterized by the fact that in which at least one calibration step (38) to generate the rich fuel-oxygen mixture reduces the ambient airflow (16).

6. Method according to any one of the preceding claims, characterized by the fact thatin which at least one calibration step (38) to generate the rich fuel-oxygen mixture increases the fuel supply.

7. Method according to any of the preceding claims, characterized by the fact that in which at least one calibration step (38) generates a rich fuel-oxygen mixture over a predetermined pulse duration (44).

8. Method according to any one of the preceding claims, characterized by the fact that The evaluation is carried out using software that controls or regulates the burner device.

9. Method according to any one of the preceding claims, characterized by the fact that The evaluation is part of a software module that controls or regulates the calibration.

10. Burner device (12) with at least one flame monitoring device (10) with at least one blower (26) which is configured to supply an ambient air flow (16) to a burner (28), with at least one fuel supply valve (30) which is configured to adjust a fuel quantity, and with at least one control and / or regulating unit (32) which is configured at least to calibrate the flame monitoring device (10) by means of the method according to one of claims 1-8.

Images