DE102019100467A1 - Process for controlling the combustion air ratio on the burner of a heater - Google Patents

Abstract

The invention relates to a method for regulating the combustion air ratio on a burner (7) for a heater for generating heat with an ionization sensor. In the case of implausible parameters, the blower (2) is operated in a previously defined target air mass flow parameter and the gas valve (1) with a previously defined valve position, which together with the target air mass flow parameter results in a defined target combustion air ratio greater than 1 under previously defined general conditions . An air mass flow parameter is then reduced while simultaneously measuring the ionization signal until a maximum of the ionization signal is recognized. The air mass flow parameter at which the maximum of the ionization signal was recognized is determined and stored. The air mass flow characteristic is then multiplied by a factor previously designed so that a desired combustion air ratio is achieved, and the air mass flow characteristic thus calculated is set.

Description

The invention relates to a method for regulating the combustion air ratio on the burner of a heater.

In the patent DE19539568C1 will describe a method for controlling a gas fan burner. An ionization electrode detects an electrical variable derived from the combustion temperature or the lambda value. A control circuit compares this variable with a selected electrical setpoint and sets the gas-air ratio (lambda value) to a corresponding setpoint. In order to compensate for the influence of a condition-related change in the proportionality between the lambda value and the electrical measured variable derived therefrom on the control system in such a way that the desired lambda setpoint value is maintained, a calibration cycle is carried out after a certain operating time. In this the lambda value is reduced starting from a value> 1. The maximum value resulting from Lambda = 1 is saved. The electrical setpoint is adjusted with this maximum value.

A generic method is from the patent EP1002997B1 known. In the case of a fully or partially premixing gas burner provided with a fan and a gas control valve, an ionization signal is measured in the flame area with the aid of an ionization electrode. The fan speed is also recorded. A signal representative of the current air ratio is then derived from the ionization signal and the fan speed and compared with a predetermined value. Depending on this comparison, a control signal for the gas control valve is determined. In order to be able to operate the gas burner safely in the optimal air ratio range over a long period of time, the gas-air ratio of the gas burner is checked at regular intervals or depending on specific events. For this purpose, a signal representative of the current air ratio and the current power is derived from the ionization signal and this is compared with a predetermined value. Information about the operating status of the gas burner can be derived from this comparison.

If a faulty operating state is detected, the gas burner is switched off. This leads to a loss of comfort.

It is therefore an object of the invention to provide a method in which safe operation of the gas burner is ensured even in the event of a faulty operating state.

This object is achieved according to the invention by a method according to the features of claim 1.

Advantageous refinements result from the features of the dependent claims.

The invention will now be explained in detail with reference to the figure.

1 shows a device for performing the method according to the invention. The essential components for the combustion process of a heater, not shown here, are shown. Via an air supply 5 air becomes a blower 2nd fed. This is done using a gas supply 6 and a gas valve 1 a fuel gas is supplied to the air and through the fan 2nd mixed and promoted. The air-gas mixture is then the burner 7 fed and burned on its surface. A the burner 7 enclosing primary heat exchanger, not shown, enables the transfer of the heat generated by the combustion to a heat transfer medium, which can then supply the heat to a heat sink.

An ionization electrode provided in the area of the flames 3rd enables a through a voltage source, not shown, which creates a voltage between the burner 7 and ionization electrode 3rd creates current flow caused by the flames between the burner 7 and the ionization current 3rd .

An ionization sensor measures that through the ionization electrode 3rd flowing current and provides an ionization signal that represents the current. A control unit 4th detects the ionization signal and controls the drive of the blower 2nd on. The control unit is for a simplified representation 4th directly with the ionization electrode 3rd connected. The voltage source, the circuit and the ionization sensor are not shown. The ionization sensor can be part of the voltage source. The ionization signal is an indicator of the quality of combustion.

Furthermore, a connection of the control unit 4th the degree of opening of the gas valve 1 certainly. This can be done, for example, by a stepper motor that is controlled by the controller 4th is controlled.

After the gas-air mixture has been successfully ignited, the fan moves 2nd to a target speed and the degree of opening of the gas valve 1 with the help of a stored control characteristic at this speed suitable opening.

The speed of the fan 2nd is now with the opening wheel of the gas valve kept constant reduced until the ionization signal reaches the maximum and falls again. An air mass flow parameter, preferably the fan speed, which is set when the maximum ionization current is reached, is stored and also the electrical fan power required for this speed and the target speed for the operating point of the system are calculated via a designed factor. This speed is then determined by the blower 2nd started. The degree of opening of the gas valve 1 remains unchanged. The blower output, which is set at the point of the maximum ionization signal, is used via other designed factors in order to calculate a minimum and a maximum value of the blower output at the operating point of the system. If the target speed and target speed are different for the operating point, a correction factor that is not equal to 1 is calculated. After a predetermined period of time t_idle, the next calibration of the system takes place by using the correction factor to determine the amount of gas via the degree of opening of the gas valve 1 is adjusted and to this current gas quantity, with the degree of opening kept constant, the fan is lowered until the ionization signal of the electrode 3rd a maximum is reached, speed and fan power are saved and the target speed for the new operating point is reached via the factor designed. This is done cyclically. The predetermined period of time can range from several minutes to several hours or days. But it can also be determined by the number of ignition processes and can range from one to up to 20 Ignition processes are.

In the event of a sensor error in the main electronic system, the comfort assurance mode takes over the safe operation and also ensures a basic supply for heating and hot water operation. Until the main system is corrected, the user receives limited hot water comfort.

The system uses the physical effect that the measured ionization current reaches a maximum at an air ratio of approx. 1. However, this physical information is not used to control the combustion quality, but to control the system from this point (air ratio approx. 1) in an area where the heat load is kept constant and the device continues to run with an acceptable level of efficiency if that Main system has failed. Exceeding or falling below the limits of the blower output for the respective working point indicate unsafe operation. If one of these limits is exceeded due to the fan output rising or falling too much, a new calibration is initiated. If the blower output limits are violated again at the set operating point, the device goes into a locking state.

At the desired operating point of the system, the combustion quality is not regulated by the ionization current, in which the gas valve position or fan speed track the signal, but the system runs in control mode. The ionization signal measured at the operating point only serves as an indicator of an error in the event of a violation of minimum or maximum absolute values in order to bring the device into a locking state in this case.

Reference list

1

Gas valve

2nd

fan

3rd

Ionization electrode

4th

control

5

Air supply

6

Gas supply

7

burner

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 19539568 C1 [0002]
• EP 1002997 B1 [0003]

Claims (5)

Method for regulating the combustion air ratio on a burner (7) for a heater for generating heat, with an ionization sensor, which has an ionization electrode (3) provided between the burner (7) and in the area of the flames of the burner (7) due to an applied Ionization signal representing voltage-flowing current provides, with a blower for conveying the air-fuel gas mixture, with a gas valve (1) for supplying fuel gas and with a controller (4) for carrying out the method, with the cyclical method steps a) determining the current one heating requirements to be covered by the heater, b) determining and outputting an air mass flow parameter belonging to the determined heat requirement, c) determining a target ionization signal belonging to the defined air mass flow parameter and the desired target combustion air ratio on the basis of previously designed and stored parameters, d) continuous or quasi-continuous Ches control of the gas valve (1) in such a way that the actual ionization signal corresponds to the target ionization signal, and with the process steps carried out at periodic intervals e) repeating steps a) to d) for a defined period of time and after the period of time has elapsed the combustion air ratio with simultaneous detection of the ionization signal until the ionization signal reaches a maximum, f) determination, plausibility check and correction of the stored parameters and continuation of the method with step a) with a simultaneous restart of the time period, characterized in that in the case that in Step f) implausible parameters were determined, instead of process steps a) to f) cyclically process steps g) operating the blower (2) in a previously defined target air mass flow characteristic and actuating the gas valve (1) with a previously defined valve position, all of which together with the target Luftmassenstr om parameter under a previously defined framework conditions results in a defined target combustion air ratio greater than 1 h) reducing the air mass flow parameter while simultaneously measuring the ionization signal until a maximum of the ionization signal is detected, i) determining and storing the air mass flow parameter at which the maximum of the ionization signal was detected, k) Multiplication of the air mass flow parameter by a factor previously designed so that a desired combustion air ratio is achieved. I) Setting the air mass flow parameter calculated under k) is carried out. Procedure according to Claim 1 , characterized in that the air mass flow parameter is the fan speed of the fan. Procedure according to Claim 1 , characterized in that the air mass flow characteristic is the electrical power of the fan. Procedure according to one of the Claims 1 to 3rd , characterized in that the voltage applied between the burner (7) and the ionization electrode (3) is an AC voltage. Method according to one of the preceding claims, characterized in that in steps h) to I) the air ratio is changed instead of by reducing or increasing the air mass flow parameter by increasing or reducing the gas supply by actuating the gas valve (1), wherein instead of Air mass flow parameter, the valve position of the gas valve (1) is used.

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