CN110573800B

CN110573800B - Method for controlling a gas-operated heating device

Info

Publication number: CN110573800B
Application number: CN201880027650.1A
Authority: CN
Inventors: E·J·罗力克; J·丹纳曼; H·亨里奇; J·赫尔曼; H-J·克林克; S·沃尔德
Original assignee: Ebm Pirtranzhut GmbH
Current assignee: Ebm Pirtranzhut GmbH
Priority date: 2017-11-08
Filing date: 2018-08-09
Publication date: 2021-06-15
Anticipated expiration: 2038-08-09
Also published as: CN110573800A; EP3596391A1; DE102017126137A1; WO2019091612A1; EP3596391B1

Abstract

The invention relates to a method for controlling a gas-operated heating device by using an electrical rating-power characteristic curve, wherein the method comprises a feasibility check and a mixture calibration.

Description

Method for controlling a gas-operated heating device

Technical Field

The invention relates to a method for controlling a gas-operated heating device.

Background

Such methods are known from the prior art, for example from the disclosure according to document WO 2006/000366a 1. The expert is also aware of combustion control according to the so-called SCOT method, in which the amount of air introduced into the burners of the heating installation is controlled as a function of the burner power. In this case, the flame signal is measured by means of an ion sensor, and the gas-air mixture is adjusted to a nominal ion measurement value stored in a characteristic curve. However, the disadvantage of the SCOT method is that, with low burner performance, the flame signal is greatly reduced, and the regulation is therefore not reliable. Furthermore, the adaptation effort, in particular in order to comply with the burner geometry, is high, and the burner power can only be determined inaccurately by the number of fan revolutions of the fan device which provide the air volume flow rate for the gas-air mixture.

Furthermore, the problem with the regulation method is that different gas types, for example natural gas or liquefied gas, and gas qualities are used for combustion. The parameters of the control method must be adjusted for the type of gas or the quality of the gas, since otherwise the combustion cannot be carried out cleanly.

For a control method of the present type, it is suitable that the speed λ in the present technique is determined by the ratio between air and gas, wherein, for example, the air ratio λ is 1.3, i.e. 30% air excess. The air demand L required for a particular fuel gas depends on the fuel gas composition, where for an example value of propane: about 30 for natural gas in group H; about 10, natural gas in group L; l is about 8. In practice, the air factor is advantageously different at different burner power points and for different gas families (e.g. natural gas or liquefied gas). Typically, this correlation is stored in the control device in the form of a power-dependent characteristic curve. In order to automatically select the correct characteristic curve, an automated gas type recognition system is required. The air volume flow vL required for a given gas-air mixture is calculated from the gas volume flow vG multiplied by the air demand L multiplied by the air factor: vL vG λ.

The combustion values of the different gases are approximately equal to the value of the air demand L. This correlation is used to precondition the modulating combustion air fan to the desired burner power. Since all gases change their volume at different temperatures and pressures, the above-mentioned conditions only apply under the same pressure and temperature conditions. For the adjustment of the combustion process, however, in the case of actual differences between air and gas, it is necessary either to base the respective mass flow or to base the respectively corrected volume flow (for example: in the case of a 30K temperature rise, the air expands by 10%, but not more air molecules participate in the combustion process, so that without correction the air factor decreases by 10%).

Disclosure of Invention

The object underlying the invention is to provide a method for controlling a gas-operated heating device that is independent of the type of gas. Furthermore, in a development, the method can be used to determine the gas type, and its regulating parameters can be adjusted according to the specific gas type.

This object is achieved by the combination of features according to claim 1.

According to the invention, a method is proposed for controlling a heating system operated with gas by using an ionization setpoint power characteristic curve, wherein a gas volume flow provided by a gas introduction device and an air volume flow provided by a fan are mixed to form a gas-air mixture and introduced into a burner of the heating system with an air factor λ based on a desired burner power. The air factor lambda is monitored by means of an ion measurement method of the burner flame of the burner. Furthermore, a plausibility check is carried out, in which the ion measurement signals of the ion measurement method are evaluated and a mixture calibration of the gas-air mixture is carried out in the event of a deviation from the ion measurement signal setpoint value. The mixture calibration is carried out by means of an ion flow regulation in which the air factor lambda of the gas-air mixture is adjusted to a value lambda_ion-maxWherein a maximum ion measurement signal is reached at an ionizing electrode of the particle measurement device within the burner flame. Calculating an ion measurement target value at a calibration point for the air factor lambda from the maximum ion measurement signal, and then calculating the air factor lambda_ion-maxAdjusted to the rated-air coefficient lambda_sollUntil the ion measurement signal equals the calculated ion signal nominal value.

In principle, the burner power is regulated as a function of the requirements for the various heat requirements of the heating device. The air quantity required for this purpose is changed by the control device as a function of the blower with adjustable speed. The fan speed is substantially equal to the air volume flow. The introduced gas volume flow is varied by an electrically controlled gas control element or gas valve and is measured by a gas mass flow sensor. The control of the gas volume flow is likewise carried out by the control unit. The fan is preferably designed as a premixing fan for mixing gas and air, so that it supplies a mixture volume flow to the burner. The gas-air mixture regulation is based on the continuous detection of the air volume flow by means of the detection of the number of revolutions of the fan and the subsequent regulation of the gas quantity by means of the control unit, wherein the target value of the gas quantity is extracted from the stored characteristic curve.

By means of a feasibility check, it can be ascertained with the method according to the invention whether parameters which influence the optimum combustion, such as the type of gas, the quality of the gas, the exhaust system, the components of the heating device, such as check valves or heat exchangers, operate in the desired manner. Each change in these parameters affects the gas-to-air ratio and therefore the ion measurement signal. This in turn can be detected.

The mixture calibration according to the invention makes it possible to adjust the air ratio lambda and to shift the heating device into an optimum combustion while taking into account the parameters influencing the combustion.

Preferably, the method can be used to determine the nominal air factor lambda_sollThe air demand value L is calculated and the type of gas is determined from this air demand value L, since L ═ vL/(vG ×) results from the formula vL ═ vG ×.λ. The value of the air demand value L is known for each gas as described above. Thus, the gas type detection can be automatically identified by the mixture calibration and saved in the controller of the heating device. Furthermore, the control unit can then use the predefined control characteristic for the respective gas type, in particular the respective ion setpoint value/power characteristic curve, for further control by experimental techniques.

Since the adjustment of the heating device is carried out along the ion setpoint value/power characteristic curve, an advantageous embodiment of the method provides that the ion setpoint value/power characteristic curve is adjusted over the entire power range of the heating device by means of the mixture calibration if the ion measurement signal deviates above a specified threshold value from the ion measurement signal setpoint value. At the same time, the ion setpoint value/power characteristic curve is adjusted over its entire course around the ratio identified at the calibration point of the mixture calibration. The new ion rating-power characteristic is then saved. After the mixture calibration, the gas air quantity is adjusted along the stored characteristic curve with the air ratio, which is accordingly power-dependent, and the newly specified air demand value L.

In the case of the mixture-calibrated regulation of the ion current, the air factor λ is adjusted by changing the gas volume flow or the gas mass flow until the ion measurement signal is equal to the calculated ion signal setpoint value. This can be done in a simple and very precise manner by controlling the gas control element. Furthermore, the actual gas mass flow can be corrected directly by the gas mass flow sensor.

The mixture calibration can be performed in both long and short versions. In both variants, first of all, the mixture volume flow is generated at a defined fan speed and the associated air volume flow is detected. In the short version, the maximum value of the ion signal is calculated directly, from which a new ion nominal value is calculated and calibrated for the known maximum value. From the gas air quantity calibrated at this operating point, the air requirement is determined and used for the subsequent mixture regulation.

In the long version, the associated ion signal setpoint value is calculated from the ion setpoint value/power characteristic curve following the detection of the air volume flow. The ion current signal is measured by the controller and compared to a currently stored characteristic curve value. The ion current regulation step is then performed, and the ion nominal value-power characteristic curve is adjusted and stored as described above. In this case, the ion signal maximum must be calculated only in special cases.

The mixture calibration is preferably carried out at a power point of the heating device which is equal to 50 to 70% of its maximum power or the burner power.

In principle, in the present control method for determining the air volume flow to be supplied by the fan for the required or demanded burner power, the desired air factor is calculated from an air factor/power characteristic curve, whereby the air volume flow to be supplied by the fan is calculated by the formula vL P λ.

In a further development of the method, it is provided that a runtime measurement is included for checking the correct operation of the gas quality sensor. During the operating time measurement, the amount of the introduced gas volume flow is actively changed by controlling the gas control element or the gas valve, and the operating time between the control and the detection of the gas volume change at the gas mass sensor is compared with a predefined operating time setpoint value. The gas valve state can be changed by increasing or decreasing the impulse, vibration or jump in the actual value. The operating time setpoint value is determined in advance by experimental techniques. If the operating time is above a limit value, a gas sensor failure occurs and the heating device is set to emergency operation, for example including a limited modulation.

In addition, the method comprises, in one embodiment variant, a running time measurement for determining the volumetric flow of the gas/air mixture. The amount of the introduced gas volume flow is actively changed, and the time of operation between the control and the change of the ion measurement signal and optionally also the value and the manner of the change of the ion measurement signal are identified. The measured operating time is then compared with an operating time-volume flow characteristic curve predetermined by experimental techniques. If the influence of the change in the gas volume flow on the ion measurement signal is too small or if the ion measurement signal changes in the wrong direction, the heating device is switched to emergency operation. If the influence is within the tolerance range, the mixture volume flow is determined from the run-time comparison via a table of values derived from experimental techniques.

It is also advantageous if the running-time measurement is repeated at predetermined time intervals. In this way, a sufficient air volume flow capability test is continuously carried out over the entire power range. Therefore, the fan revolution number is verified to be feasible by a safety technique. This time measurement can be used as a further stage of development in order to carry out the combustion air calculation at different power points depending on the statically recognized values. The internal stored characteristic curve can thus be dynamically corrected for combustion air calculation.

Furthermore, the method provides that the actual air volume flow is calculated from the difference between the adjusted air volume flow and the mixture volume flow determined by the operating-time measurement and optionally also from the measured temperature of the air volume flow.

As a further feature, the method provides for the number of revolutions of the fan and the resulting setpoint air volume flow to be continuously corrected with the actual air volume flow. In the event that the revolutions differ too much during operation, for example because the heat exchanger is blocked, despite the same air volume flow, the control switches off the heating device and issues an alarm.

As another aspect, the method includes integrating the mixture calibration into a start-up procedure for a cold start of the heating device. At the same time, an ignition test of the gas-air mixture was performed until a burner flame was detected by the ion measurement. The gas mass flow occurring at the ignition time remains constant and is stored in the control unit. Calculating a start-air demand from a ratio of a gas volume flow to an air volume flow extracted from the fan characteristic curve and corresponding to the ignition speedL_startThereby determining the gas type as described above. Determining a starting point for the next burner start from the stored gas mass flow and the ignition range.

As long as the term "volume flow" is used here, the mass flow can likewise be used.

Drawings

Further advantageous developments of the invention are characterized in the dependent claims or are explained in more detail below in conjunction with the description of preferred embodiments of the invention with reference to the drawings. Wherein:

FIG. 1 is a schematic structural view of the heating apparatus;

FIG. 2 is a short version of the mixture calibration process;

figure 3 is a long version of the mixture calibration process.

Detailed Description

In fig. 1, a schematic block diagram of a heating device 100 for carrying out a conditioning process with a modulating premixing fan 5 which takes in ambient air a and mixes it with fuel gas is shown. The gas is conducted into the premixing fan 5 via a gas line, in which a gas safety valve 1, a gas valve 2, which is controllable, for example, by means of an electric motor M, and a gas quality sensor 3 are arranged. The gas feed pressure d is adjusted to the gas regulating pressure c. After mixing with ambient air, the mixture has a mixture pressure b. On the blower outlet, in the embodiment shown, an optional non-return valve 6 is provided. The mixture then has a burner pressure e. The burner 28 is then connected to an ion electrode 7 arranged in the burner flame and to a siphon 10 connected to the burner housing. Around the burner 28, the heat exchanger 18 is arranged. Continuing immediately in the flow direction is the exhaust system comprising the exhaust valve 8. There is an exhaust pressure f in the exhaust system. The regulation of the gas quantity and of the fan revolutions, and thus of the air ratio, takes place by means of the control unit 9, in which the regulating characteristic is stored.

FIG. 2 showsA partial flow of a short version of the mixture calibration of the conditioning procedure is shown. First, in step 601, the fan rotational speed n of the premixing fan 5 is controlled to a fixed value by the controller 9 and the actual air volume flow vL-ist is calculated in step 300 by means of the above-described operating time measurement. Next, below step 612, the ion current is regulated at a defined air volume flow vL-ist by increasing the gas flow until a maximum ion measurement signal (Io-max) is reached. From the maximum ion measurement signal, the ion signal setpoint value (Io-soll, Io-neu) is calculated for the desired air factor λ, and then, in step 615, the gas quantity is regulated until the ion measurement signal is equal to the calculated ion signal setpoint value Io-soll. The Gas mass flow Gas _ ist determined at the new operating point is used in order to include the air factor λ in step 617 by using the air factor/power characteristic curve_sollThe air volume flow vL and the current burner power result in the air demand L ═ vL/(vG ×) λ_soll) And the gas type is determined by the air demand value L. In short versions, the ion calibration is performed at each mixture calibration.

Fig. 3 shows a partial flow of a long version of the mixture calibration of the conditioning procedure. First, in

steps

601 and 300, the blower speed n of the premixing blower 5 is controlled to a fixed value by the controller 9, and the actual air volume flow rate vL-ist is calculated. Next, in step 605, the ion signal nominal value Io-soll is calculated by using the ion nominal value-power characteristic curve and the burner power P. According to step 607, in the ion measuring method, the ion current at the ion electrode 7 is measured by the controller 9 and compared with the characteristic curve value. When the values agree, the measured ion current is used for further mixture calibration. If the deviation of the comparison value is greater than a predefined threshold value, the ion setpoint value/power characteristic curve is calibrated by providing a specified air volume flow vL-ist in step 612The gas quantity is increased until the maximum ion measurement signal Io-max is reached. From the maximum ion measurement signal, the ion signal nominal value 624(Io-soll) is calculated for the desired air factor λ (in step 625). According to step 613, the original ion rating-power characteristic curve Io-alt is corrected over its entire power range to the new ion rating-power characteristic curve Io-neu around the ratio identified at the calibration point for the mixture calibration. The new ion rating-power characteristic curve Io-neu is stored in the memory of the controller 9. In step 615, the gas quantity is adjusted until the ion measurement signal is equal to the calculated ion signal nominal value Io _ soll. The Gas mass flow Gas _ ist determined at the new operating point is used in order to utilize the target air factor λ in step 617_sollCalculating the air demand value L ═ vL/(vG ^ lambda)_soll) And the gas type is determined by the air demand value L. In the long plate, ion calibration is performed only in special cases.

Claims

1. Method for controlling a heating device (100) operated by a gas by using an ion setpoint-power characteristic curve, along which the control of the heating device (100) is carried out, wherein,

a. the gas volume flow provided by the gas introduction device and the air volume flow provided by the fan are mixed to form a gas-air mixture and introduced into a burner (28) of the heating device with an air coefficient lambda based on the desired burner power;

b. -monitoring the air factor λ by means of an ion measurement method of a burner flame of the burner (28);

c. performing a plausibility check in which the ion measurement signals of the ion measurement method are evaluated and a mixture calibration of the gas-air mixture is performed in the event of a deviation from the ion measurement signal setpoint value; and wherein the one or more of the one,

d. the mixture calibration is carried out by means of ion current regulation, wherein the gas/air mixture is adjusted to the value of the ion measurement signal at which the maximum ion measurement signal is reached, from which the ion signal setpoint value is calculated for the setpoint air factor λ soll at the calibration point, wherein, in the mixture-calibrated ion current regulation, the air factor λ is adjusted by varying the gas volume flow until the ion measurement signal equals the calculated ion signal setpoint value.

2. The method according to claim 1, characterized in that an air demand value L is calculated from the setpoint air factor λ soll and the gas type of the gas is determined from the air demand value.

3. Method according to claim 1 or 2, characterized in that the ion setpoint value/power characteristic curve is adjusted over the entire power range of the heating device by means of the mixture calibration if the ion measurement signal deviates above a specified threshold value from an ion measurement signal setpoint value.

4. Method according to claim 1 or 2, characterized in that in the mixture calibration, a volume flow is first produced and measured at a defined fan speed, and the associated ion signal setpoint value is calculated from the ion setpoint value/power characteristic curve.

5. Method according to claim 1 or 2, characterized in that, in order to determine the air volume flow to be supplied by the fan for the required burner power, a desired air factor is calculated from an air factor-power characteristic curve and the air volume flow to be supplied by the fan is calculated therefrom.

6. Method according to claim 1 or 2, characterized in that it comprises an operating time measurement for checking a gas quality sensor, in which the quantity of introduced gas volume flow is actively changed by controlling a gas valve (2), the operating time between said controlling and the recognition of the gas volume change on the gas quality sensor (3) being compared with a predefined operating time setpoint value.

7. Method according to claim 1 or 2, characterized in that it comprises a running time measurement for determining the gas-air mixture volume flow, in which the introduced gas volume flow quantity is actively changed by controlling a gas valve (2), the running time between the control and the ion measurement signal change is identified, and in which the measured running time is compared with a running time-volume flow-characteristic curve predetermined by experimental techniques, whereby the mixture volume flow is determined.

8. The method of claim 7, wherein the magnitude and manner of change in the ion measurement signal is additionally identified.

9. The method according to claim 7, characterized in that the actual air volume flow is calculated from the difference between the adjusted air volume flow and the measured mixture volume flow measured by the run-time measurement.

10. Method according to claim 9, characterized in that the actual air volume flow is calculated from the measured temperature of the air volume flow.

11. The method of claim 7, wherein the run-time measurements are repeated at predetermined time intervals.

12. Method according to claim 9, characterized in that the actual air volume flow is continuously used to correct the fan revolutions of the fan (5) and the resulting nominal air volume flow.

13. Method according to claim 1 or 2, characterized in that the mixture calibration is carried out at a power point of the heating device equal to a range of 50 to 70% of its maximum power.

14. Method according to claim 1 or 2, characterized in that the mixture calibration is integrated into a start-up procedure for a cold start of a heating device.