EP3889505A1 - Method and device for setting a control setpoint for the fuel / air mix during operation of a burner - Google Patents

Abstract

The invention relates to a method and a device for setting the ratio of air to fuel (lambda value) in a burner (1) fired with a fuel gas and / or a liquid fuel, with a housing (6) of the burner (1) or its electronic control (7) an interface (8) is present, which is connected to the electronic control via a data link (11) and a change in the ratio of air to fuel within a correction range (K ), whereby a tolerance range for the ratio of air to fuel (lambda) and the correction range (K) for possible changes are limited in such a way that even maximum incorrect changes within the correction range (K) do not lead to the ratio from air to fuel (lambda) leaves the tolerance range. The interface (8) allows the maintenance personnel to make a fine adjustment of the air-to-fuel ratio, adapted to special conditions on site during operation, without the risk of tolerance limits being exceeded.

Description

The invention relates to a method and a device for setting the control setpoint for the ratio of fuel to air (also called air number or lambda value in relation to a stoichiometric ratio).

According to the state of the art, modern systems for heating and / or generating warm heating water or service water by burning liquid or gaseous fuels are equipped with a complex control system. This makes it possible to keep the lambda value in a desired (operationally safe and environmentally friendly) range, the so-called tolerance range, during ignition and operation under different load conditions. It is important to set the tolerance range as broad as possible, but in such a way that stable combustion and compliance with limit values for the emission of pollutants, in particular for carbon monoxide and nitrogen oxides, are guaranteed even with somewhat changeable ambient conditions, temperatures and fuel qualities. Systems that can do this are approved or certified according to certain standards (which may differ from country to country). For good reason, it is therefore not easily possible for the operator of such a system to change the regulation. This is reserved for special specialists with the appropriate equipment and can e.g. B. with the help of an update of the control software or by changing calibration data.

On the other hand, such systems are often serviced on site by personnel who can measure and recognize whether the system is optimally or as desired for the respective local conditions. In older systems there was usually at least one setting option ("setting screw", such as an adjusting screw on a gas valve) for changing the lambda value, which allowed the maintenance staff to optimize for local peculiarities. This is often not the case with newer electronically controlled systems, so that the maintenance staff on site can determine that a system complies with limit values, but could be set even better, but there is no way to do this on site without special equipment.

From the EP 0 488 969 A2 a regulation of the lambda value is known in which there is a simple electronic regulation with a small number of sensors, while many basic settings can or must be made manually via an interface. With this type of regulation and setting, unfavorable settings can also be selected, with which today's exhaust gas regulations are not reliably complied with, so that such systems could no longer be approved in many countries.

The object of the present invention is to at least partially solve the problems mentioned with reference to the state of the art, and in particular to provide a simple way of changing the lambda value, which, however, cannot lead to such interventions in a safe and approvable control, that the approved tolerance ranges are exceeded.

A method and a device according to the independent claims serve to solve this problem. Advantageous refinements and developments of the invention are specified in the respective dependent claims. The description, in particular in connection with the drawing, illustrates the invention and specifies further exemplary embodiments.

For the method for setting the air-to-fuel ratio in a burner fired with a fuel gas and / or a liquid fuel, an interface connected to the electronic control via a data connection (device for the interaction of Man and machine) are used, with an input option on the interface causing a change in the ratio of air to fuel within a correction range that can be specified by the electronic control in the electronic control. A tolerance range for the ratio of air to fuel and the correction range for possible changes in the electronic control are specified and limited in such a way that even maximum incorrect changes within the correction range under all operating conditions do not result in the ratio of air to fuel exceeding the tolerance range leaves. This means in particular that an approval or certification that applies to the entire tolerance range is retained in the event of changes within the correction range and that the system still complies with all the limit values for safety and environmental compatibility under all corrections.

The “insertion” of the interface includes, in particular, that the electronic control can be intervened (temporarily and / or partially) by means of the interface. It is possible that the interface is connected to the housing or the control (or control unit), for example via a suitable holder or a suitable data connector. It is possible that the data connection also acts on the regulation by radio, telephone, a cloud or the like, with suitable, possibly at least one mobile, radio units being provided for this purpose. The "input option" can z. B. over a Keyboard, a controller, a sensor and / or a computer unit can be set up. In particular, it is provided that the electronic control and / or the interface includes a restriction that limits the setting of the lambda value, namely in a predetermined correction range, which is usually limited by a predefined or calculated upper limit and a predefined or calculated lower limit. The specified correction range can be stored in a memory and made available for the setting. It is possible that the electronic control blocks or denies settings outside the correction range. The “setting” of the air-to-fuel ratio consequently includes, in particular, fine adjustment, calibration, readjustment or the like.

A technician on site therefore has the option of making changes within the correction area that allow an adaptation to current conditions. This allows, for example, an optimization of an exhaust gas parameter or of noise from a fan or the like.

In a particular embodiment, the ratio of air to fuel is changed for one or more different burner outputs, it being possible to use different correction factors for different outputs.

The regulation preferably stores the changes made and uses the stored values for future operation for regulation until the system is reset to its original values or new correction factors are entered.

According to a further aspect, a device for setting or fine adjustment of the ratio of air to fuel (lambda) in a burner fired with a fuel gas and / or a liquid fuel is proposed, which has an interface on a housing of the burner or its electronic control, which is connected to the electronic control via a data link and allows the ratio of air to fuel to be changed within a correction range specified by the control. A technician can thus intervene on site which, within certain limits, corresponds to an "adjusting screw" on older devices and allows fine adjustment. A tolerance range for the air-to-fuel ratio and the correction range for possible changes in the electronic control are specified and limited in such a way that even maximum incorrect changes within the correction range under all operating conditions do not result in the air-to-fuel ratio falling below the tolerance range leaves.

For this purpose, the interface has at least one input option for changes. This can be achieved in many ways, for example by using individual buttons for plus and minus or a rotary knob.

The interface preferably has a display of the current ratio of air to fuel or a variable derived therefrom. A representation in the form of a diagram is also possible. A so-called “touchscreen” (touch-sensitive display) can particularly preferably be used at the same time as a display and for setting a correction.

The interface is generally set up for changing data and storing it in the electronic control so that changes made remain effective in the future.

In a preferred embodiment, the interface is set up for changing and storing the air-to-fuel ratio for different burner outputs, with different correction factors also being able to be entered and saved, in particular for different outputs. It may well be that a different correction is useful or desired in a lower power range than in a higher power range. The control electronics can be set up in such a way that an interpolation takes place between the individual correction factors in power ranges.

The procedure proposed here can be carried out or controlled at least partially with specific means for data processing. Therefore, in particular a control unit or electronic control for setting the lambda value in a burner is proposed, which is equipped with an interface and with means which are suitable and / or set up to carry out the steps of the method. A computer program is also proposed, comprising commands which cause the proposed device to carry out the method steps. This is also recorded by a computer-readable medium on which this computer program is stored.

Fig. 1:

eine Vorrichtung zur Feinjustierung des Lambda-Wertes, und

Fig. 2:

ein Diagramm zur Veranschaulichung der Wirkung der Feinjustierung.

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

Fig. 1:

a device for fine adjustment of the lambda value, and

Fig. 2:

a diagram to illustrate the effect of fine adjustment.

Figure 1 shows schematically a device which is suitable and set up to implement the procedure proposed here. A burner 1 with a burner housing 6 is supplied with combustion air from an air inlet 2 via a fan 3. At a fuel inlet 4, liquid or gaseous fuel is added to the combustion air, this process being controlled or regulated by a fuel valve 5. An electronic control 7 regulates the entire operation of the burner 1, which is why it is connected via signal lines 12 to the fan 3, the fuel valve 5 and other sensors and actuators (not shown).

There is also an interface 8 with a display 9 and an input option 10, which is accessible at a suitable location on the outside of a burner housing 6 or on the outside of the electronic control 7. It is connected to the electronic control 7 by means of a data connection 11 (which can in principle also take place via radio) and is set up to enter a correction factor at different load levels (outputs of the burner 1) and to store it in the electronic control 7. In the illustrated embodiment, a correction factor is entered by means of a rotary knob, the pressing of which leads to the storage of the set value.

Fig. 2 illustrates in a schematic and not to scale representation the function of the procedure proposed here on the basis of a diagram. The power L of the burner 1 is plotted as an example on the X-axis, with it in the example about a burner 1 with outputs between 5 and 20 kW [kilowatts]. A target value S is plotted on the Y eighth, which is physically related to the ratio of combustion air to fuel that is set in each case. Curve A shows the course of the setpoint S as a function of the power L with the factory setting. Typically, curve A is located approximately in the middle of a tolerance range, not shown, of which it has been proven that setpoint values within this tolerance range bring about operationally safe conditions and comply with all regulations. The distance between curve A and the limits of the tolerance range is so great that a change in the setpoint values within a correction range K between an upper correction limit O and a lower correction limit U, regardless of the operating conditions, cannot lead to limit values being exceeded. The fine adjustment according to the invention makes use of this and allows the setpoint S to be changed in the correction range K. Curve B shows how a corrected course of the setpoint S can look as a function of the power L of the burner 1.

The present invention allows maintenance personnel to intervene on site in modern burner systems with electronic control, so that adaptation to local features (e.g. humidity, temperature, fan noise etc.) is possible to a certain extent, without endangering an operating license or certification.

List of reference symbols

1

burner

2

Air inlet

3

fan

4th

Fuel inlet

5

Fuel valve

6th

Burner housing

7th

Electronic regulation

8th

interface

9

advertisement

10

Input option

11

Data Connection

12th

Signal lines

L.

Power of the burner

S.

Setpoint for lambda value

K

Correction area

O

Upper correction limit

U

Lower correction limit

A.

uncorrected setpoints

B.

corrected setpoints

Claims (10)

Method for setting the ratio of air to fuel (lambda) in a burner (1) fired with a fuel gas and / or a liquid fuel, with a housing (6) of the burner (1) or its electronic control (7) having a the electronic control (7) via a data connection (11) connected interface (8), and with an input option (10) on the interface (8) a change in the ratio of air to fuel (lambda) within a through the electronic control (7) predeterminable correction range (K) is effected in the electronic control (7), with a tolerance range for the ratio of air to fuel (lambda) and the correction range (K) for possible changes being limited so that even maximum incorrect changes within of the correction range (K) do not lead to the ratio of air to fuel (lambda) leaving the tolerance range under all operating conditions. Method according to Claim 1, in which the ratio of air to fuel is changed for one or more different outputs of the burner (1). Method according to Claim 1 or 2, the control system storing the changes made and using the stored values for control in a future operation. Device for setting the air to fuel ratio (lambda) in a burner (1) fired with a fuel gas and / or a liquid fuel, with an interface on a housing (6) of the burner (1) or its electronic control (7) (8) is available, which is connected to the electronic control (7) via a data link (11) and allows the air to fuel ratio (lambda) to be changed within a correction range (K) specified by the electronic control (7), A tolerance range for the ratio of air to fuel (lambda) and the correction range (K) for possible changes are limited in such a way that even maximum incorrect changes within the correction range (K) do not lead to the ratio of air to Fuel (lambda) leaves the tolerance range. Device according to Claim 4, the interface (8) having at least one input option (10) for changes. Apparatus according to Claim 5, the interface (8) having a display (9) of the current ratio of air to fuel or a variable derived therefrom. Device according to one of Claims 4 to 6, the interface (8) being set up for changing data and storing them in the electronic control (7). Device according to one of Claims 4 to 7, the interface (8) being set up for changing and storing the ratio of air to fuel for different outputs of the burner (1). Control unit for setting the lambda value in a burner (1) with an interface (8) and means which are suitable and / or designed to carry out the steps of the method according to one of Claims 1 to 3. Computer program, comprising instructions which cause the device according to one of Claims 5 to 8 to carry out the method steps according to one of Claims 1 to 3.

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