EP2594848A1 - Method for controlling a firing device and firing device - Google Patents

Abstract

The firing equipment has means for determining a value dependent on a measured temperature produced by the equipment and also means for regulating the generated temperature by using a characteristic line representing a value range corresponding to the ideal temperature in dependence on a first parameter corresponding to the burner power. A second parameter corresponding to a ratio of air volume to quantity of burner medium in a mixture of air and burner medium to be supplied to the burner is constant in the characteristic line so that a first parameter is produced corresponding to a specific burner power. The firing equipment has a device in the region of the burner flame (13) to measure the temperature produced by the firing equipment.

Description

The disclosure comprises a method for controlling a firing device, in particular a gas burner, in which a value is determined that depends on a measured temperature generated by the firing device. In addition, the disclosure includes a firing device, in particular a gas burner, comprising means for measuring a value that depends on a temperature generated by the firing device. The invention relates to a method for controlling a firing device, in particular a gas burner, and a firing device, in particular a gas burner, which comprises a gas valve for adjusting the fuel supply to the firing device.

In the household gas burners, for example, as a water heater, for the preparation of hot water in a boiler, to provide heating and the like. Ä. Used. In the respective operating conditions, different requirements are placed on the device. This concerns in particular the output of the burner.

The power output is essentially determined by the setting of the supply of Fuel gas and air and determined by the set mixing ratio between gas and air. The temperature generated by the flame is also a function of the mixing ratio between gas and air. The mixing ratio can be specified, for example, as the ratio of the mass flows or the volume flows of the air and the gas. However, other parameters, such as the fuel composition, have an influence on the sizes mentioned.

In addition, for any given air mass flow or gas mass flow, a mixing ratio can be determined which maximizes the effectiveness of the combustion, i. where the fuel burns as completely and clean as possible.

For this reason, it has proven to be useful to regulate the mass flows of gas and air and always set so that in each case an optimal combustion is achieved under changing requirements and boundary conditions. A regulation can take place continuously or at regular intervals. In particular, a control in a change of the operating state, but for example also due to changes in the fuel composition in continuous operation is required.

To provide the air / gas mixture through which the burner flame is fed, known gas burners are usually equipped with a radial fan, which sucks the mixture of air and gas during operation. The adjustment of the mass flows of air and gas can be done for example by changing the speed and thus the suction of the impeller of the radial fan. In addition, valves can be provided in the gas and / or air supply line, which can be actuated to set the individual mass flows or their ratio. To measure individual parameters, various sensors can be arranged at suitable locations. Thus, appropriate measuring devices can be provided for measuring the mass flow and / or the volume flow of the gas and / or the air and / or the mixture. Likewise, state variables such as the temperature of the air, pressures, etc., can be measured at appropriate locations, evaluated and used for the control.

The regulation of the mixing ratio is done today by default, especially for gas burners used in the household, by pneumatic control of a gas valve in dependence on the volume flow of the supplied air quantity (principle of pneumatic composite). In pneumatic control, pressures or pressure differences on orifices, in constrictions, or in venturi nozzles are used as control variables for a pneumatic gas control valve that adjusts the gas supply to the airflow. A disadvantage of the pneumatic control, however, is in particular that mechanical components must be used which are subject to hysteresis effects due to the friction. Especially at low working pressures, inaccuracies in the control occur, so that the blower must always produce a certain minimum pressure in order to achieve a sufficiently precise control, which in turn leads to an over-dimensioning of the blower for maximum performance. In addition, the expense of manufacturing the diaphragm-equipped pneumatic gas control valves is remarkable because of the high precision requirements. In addition, in the pneumatic network it is not possible to respond flexibly to changes in the gas type and quality. To be able to make desired adjustments to the gas supply nevertheless, additional equipment, such as actuators, must be prepared and adjusted, which means considerable additional expense in the installation or maintenance of a gas heater.

For these reasons, one goes to equip gas burner with an electronic composite. With electronic control easily controllable valves, such as pulse width modulated coils or stepper motors, can be used. The electronic composite operates by detecting at least one combustion characterizing signal which is fed back to a feedback control loop.

However, the use of the electronic interconnect also presents situations that can not be adequately addressed, such as a change in sensitivity of the sensors due to contamination. In addition, there is a risk that changes in the load or the operating state or immediately after the start of operation of the gas burner that the scheme due to the inertia of the sensors is delayed, resulting in imperfect combustion and in extreme cases to extinguish the burner flame.

The DE 100 45 270 C2 discloses a firing device and method for controlling the firing device with fluctuating fuel quality. In particular, when the gas quality changes, the fuel-air ratio becomes corresponding changed. In this case, the mixture composition is adjusted for each suitable type of fuel until the desired flame core temperature is reached. In addition, maps are used for different fuels, from which a new, suitable fuel-air ratio is read out whenever the performance requirements change.

In the GB 2 270 748 A a control system for a gas burner is shown. The regulation takes place here using a temperature measured at the burner surface. Since the surface temperature depends on the flow rate of the air-gas mixture, falling below a certain temperature, the speed of the fan motor is lowered, whereby the air flow and thus the air-gas ratio is lowered.

From the AT 411 189 B a method for controlling a gas burner is known in which the CO concentration in the exhaust gases of the burner flame is detected with an exhaust gas sensor. A certain CO value corresponds to a certain gas-air ratio. Starting from a known, for example experimentally determined, gas-air ratio at a certain CO value, a desired gas-air ratio can be set.

The EP 770 824 B1 shows a control of the gas-air ratio in the fuel-air mixture by measuring a Ionisationsstroms, which depends on the excess air in the exhaust gases of the burner flame. In stoichiometric combustion, a maximum of the ionization current is known to be measured. Depending on this value, the mixture composition can be optimized.

A disadvantage of the last-mentioned method, however, is that the feedback signal can only be detected when the flame is burning and fed back to the control loop. In addition, the inertia of the sensors limits accurate readjustment. In addition, the sensors used are subject to contamination, so that the combustion is suboptimal regulated over time and thus increase the pollutant levels. In particular, during the starting process, in which there is still no combustion signal, or load changes in which significant changes in the operating parameters are required in a short time, it can cause difficulties and in extreme cases to extinguish the flame. Frequently, for these reasons, resort to pneumatic regulators, but an increase in the complexity of Investment and costs.

Based on this, it is an object of the present invention to reliably ensure a gas-type independent fuel supply, even with fast load changes and in the starting phase without time delays.

These objects are achieved by a method according to claim 1 and a firing device according to claim 8.

The method for controlling a firing device, in particular a gas burner, comprises the steps of: determining a value which depends on a measured temperature generated by the firing device; Specification of a first parameter that corresponds to a certain burner load; and regulating the value of the temperature generated by the firing device by using a characteristic curve representing a value range corresponding to a target temperature as a function of the first parameter corresponding to a burner load, wherein in the representation of the characteristic a second parameter, preferably the air ratio (λ ), defined as the ratio of the actual amount of air supplied to the amount of air theoretically required for optimal stoichiometric combustion, is constant.

The disclosure is based on the finding that a characteristic curve for controlling the value dependent on a temperature produced by the firing device does not depend on one of the types of gas used. The method of regulation is thus gas-independent.

The temperature generated by the firing device is generally measured by a sensor arranged in the flame core or at the burner itself, for example at the burner surface. However, it can also be measured at the base of the flame, at the tip of the flame, or at some distance within the working range of the flame. The measured temperatures, depending on where the temperature sensor is mounted, and depending on the load and the air-fuel ratio, about values between 100 ° C and 1000 ° C at.

The characteristic curve shown for a constant second parameter can be determined both empirically and mathematically. The second parameter value is the value predetermined, with which the optimal combustion takes place with the existing burner. For example, as the second parameter value, the air ratio λ can be used, which should desirably be λ = 1.3. The air ratio λ is defined as the ratio of the actual amount of air supplied to the amount of air theoretically required for optimal stoichiometric combustion.

Among other things, the method is particularly simple and reliable in that the control can be carried out independently of the quality of the fuel and thus without analysis of the fuel. Thus, continuous or periodic corrections of the characteristic or a preselection of a characteristic field for different fuels / gases accounts.

The first parameter corresponds in particular to one of the firing devices per unit of time to be supplied air quantity. This means the representation of a value corresponding to the setpoint temperature at a constant second parameter value as a function of the amount of air supplied to the burner flame per unit of time. A constant second parameter, conversely, means that with the change in the amount of air, the amount of fuel supplied is changed accordingly to maintain the optimal stoichiometric ratio between air and fuel gas for combustion.

The first parameter preferably corresponds to a mass flow or volume flow of the air to be supplied to the firing device. The mass flow of the air can be determined for example by a mass flow sensor in the supply channel for the air supplied to the burner. With a change in the load, corresponding to a change in the air mass flow, the mass flow or volumetric flow of the fuel changes at constant second parameters in the same way, which can also be measured by a suitably located mass flow sensor.

The burner load is at a constant air ratio substantially proportional to the amount of air supplied to the firing device per unit time. For the characteristic curve used, it is thus irrelevant whether the first parameter expresses an air or gas mass flow or a load, for example.

The method preferably comprises a comparison of the measured value dependent on the temperature with a desired value determined from the characteristic curve. As in In most control processes, a deviation of the actual temperature from the temperature setpoint causes a setting of the operating parameters that reduces this deviation to be made so long or until the deviation between the actual value and the setpoint value has been compensated. For example, at a measured temperature below the setpoint temperature by gradually increasing the amount of fuel supplied, the mixture can be enriched until the deviation of the actual value from the desired value no longer exists. In the same way, the mixture can be emaciated accordingly at too high actual temperature.

The value corresponding to the setpoint temperature is preferably determined as a function of the first parameter from the characteristic curve. If, for example, the mass flow of the air is selected as the first parameter, then the mass flow of the air is predetermined and the desired temperature corresponding to this mass flow is read from the characteristic curve. The regulation takes place until the value of the actual temperature corresponds to the setpoint temperature value.

The measured value and / or the value range of the characteristic corresponds in particular to a temperature difference. For temperature measurement, for example, thermocouples can be used. In a particular embodiment, the temperature difference is a temperature difference between a temperature generated in the region of the burner flame and a reference temperature.

The reference temperature may correspond to the temperature of the air or air-fuel mixture prior to entering the region of the burner flame. If the temperature of the reference junction is known, the absolute temperature can also be determined. Alternatively, for example, the ambient temperature of the burner can serve as a reference.

The control may include an increase or decrease in the amount of gas supplied per unit time. In this embodiment, therefore, the temperature is controlled by enriching or leaning the mixture with fuel until the measured value, which is dependent on the actual temperature, coincides with the desired value.

The increase or decrease in the amount of gas supplied per unit time is carried out in particular by actuation of a valve. For example, a stepper motor actuate an actuator of a valve, or modulated a pulse width or an electrical variable in an electrically controlled coil can be changed.

The firing device, in particular a gas burner, comprises: means for measuring a value which depends on a temperature generated by the firing device; Means for controlling the temperature generated by the firing device with specification of a first parameter corresponding to a certain burner load, and using a characteristic curve representing a value range corresponding to a target temperature as a function of the first parameter corresponding to the burner load, wherein in the representation of the characteristic curve a second parameter corresponding to a ratio of an amount of air to an amount of combustion medium in a mixture of air and combustion medium to be supplied to the firing device is constant.

The device for measuring the temperature-dependent value can be arranged in particular in the flame kernel, at the burner surface, at the base of the flame or at the tip of the flame. The inertia of the temperature sensor depends essentially on the distance to the flame and on the inert masses of the sensor and its attachment.

The first parameter may correspond to one of the firing devices per unit of time to be supplied air, in particular a mass flow or volume flow of the air.

The firing device preferably has a measuring device for measuring the amount of air and / or fuel medium supplied to the firing device per unit time and / or of a mixture of air and fuel medium, in particular for measuring a mass flow or volume flow. The sensors are to be arranged in the device such that the most reliable possible conclusion can be drawn on the mass flows flowing through them. This can for example be the case in a bypass. The burner load at a constant air ratio is generally substantially proportional to the amount of air supplied to the gas burner per unit time.

The firing device may comprise means for comparing the value corresponding to the measured temperature with a desired value determined from the characteristic curve.

The means for measuring a value dependent on the generated temperature may be adapted to measure a value corresponding to a temperature difference. From this temperature difference, the absolute temperature can be determined at a known reference temperature.

In particular, the value corresponds to a temperature difference between a temperature generated in the region of the burner flame and a reference temperature, wherein the reference temperature corresponds in particular to the temperature of the air or of the air-combustion medium mixture before it enters the region of the burner flame.

The device for measuring a temperature value preferably comprises a part which is arranged at least partially in the region of the reaction zone of the burner flame.

For the measurement of the reference temperature, a part of the device for measuring the temperature value outside of the reaction zone of the flame, in particular in the region of an inlet zone for the air supplied to the firing device and / or for the air / combustion medium mixture supplied to the firing device can be arranged.

The means for measuring a temperature value preferably comprises a thermocouple. In this case, a contact point of the different legs of the thermocouple in the region of the reaction zone of the burner flame is arranged, the reference point outside this reaction zone to detect a temperature difference between the flame and a thermally decoupled therefrom area, for example, an ambient region of the gas burner.

The value measured by the means for measuring a temperature value is preferably a thermoelectric voltage.

The means for controlling may be adapted to increase and / or decrease the amount of combustion medium supplied to the firing device per unit time.

In particular, the firing device comprises a valve which can be actuated to increase or reduce the amount of gas supplied per unit of time.

In the method according to the invention for controlling a firing device, in particular a gas burner, when the first parameter corresponding to the burner load changes from a starting value to a target value, the fuel supply to the firing device is changed by changing the opening of a gas valve from a first to a second opening value and by setting a target value that depends on the first parameter adjusted, wherein the second opening value between an upper and lower limit, and wherein during the transition of the opening of the gas valve from the first to the second opening value, no control of the fuel supply performed and only after Achieving the target value of the first parameter, which corresponds to the burner load, a control of operating parameters of the firing device is performed.

With the help of this method, stable conditions can be achieved with fast load changes, but especially during the starting process. A readjustment of the gas valve, which takes a great deal of time with large fluctuations in the operating parameters and is imperfect due to the inertia of the sensors, can thus be dispensed with. The controller is replaced by a controller which specifies a setpoint value for a new setting as a function of the target value of the first parameter. Only in the following step is readjusted using real measured variables. With the method, regardless of the inertia of the sensors used for the control, a fast and reliable adjustment of the gas valve can be found. The real opening of the gas valve is between an upper and a lower limit. For rapid setpoint changes, the actuators, such as the fan or a gas control valve, after a certain period of time, which depends on the inertia of the sensors, be readjusted. It thus takes place in the execution of the method according to the invention, a transition from a pure control to a control.

The parameter corresponding to the burner load may be the amount of air to be supplied to the firing device per unit time, in particular a mass flow or volume flow of the air to be supplied to the firing device. The opening values of the gas valve can therefore be represented in this embodiment as a function of the mass or volume flow of the air. The characteristic of this characteristic is determined inter alia by the properties of the gas valve.

The burner load is substantially proportional to the amount of air supplied to the gas burner per unit time. Thus, it is clear that the representation of the opening of the gas valve as a function of mass flow of the air is equivalent to a representation of the opening of the gas valve in response to a load on the burner.

The change of the opening of the gas valve may be performed by the modulation of a pulse width, by the variation of a voltage or a current of a valve spool, or by the operation of a stepping motor of a valve. Exceeding the upper or lower limit of the opening of the gas valve can be detected in the process. While after the control process, the opening of the gas valve is between the upper and lower limit, after the control step, the gas opening may be above or below the upper or lower limit. This can occur, in particular, if the setpoint values for the opening of the gas valve that are defined when the characteristic curve is generated deviate greatly from the optimally adjusted values. This can be due to changes in the fuel composition, changes in the measurement characteristics of the sensors or the settings of the system parameters.

The characteristic resulting from the opening values of the gas valve as a function of the parameter corresponding to the burner load can be recalibrated on the basis of the operating parameters set by the control unit of the firing device. If, after regulation, the value of the opening of the gas valve falls outside the range bounded by the upper and lower limit values, a recalibration of the characteristic curve can be carried out. For example, during this recalibration, the setpoints may be shifted so that the new setpoint line passes through the adjusted value for the opening of the gas valve. In the same way, the upper and lower limits can be shifted, so that the new setpoint curve is surrounded by a tolerance corridor, as in the previously valid characteristic curve.

Exceeding the upper or falling below the lower limit can, in particular after the expiry of a predetermined period of time, lead to switching off the firing device. This measure can be based on both safety concerns and economic considerations. A control in a range outside the desired range indicated by the limits can, for example indicate an undesirable change in the default settings of the gas burner, so that it may operate in an unsafe or ineffective operating range. The device would have to be checked and maintained below.

A firing device according to the invention, in particular a gas burner, comprises: a gas valve for adjusting the fuel supply to the firing device; a memory for storing set values that depend on a parameter corresponding to the burner load and upper and lower limits; a device for controlling the opening of the gas valve, which, in the event of a change of the parameter corresponding to the burner load from a starting value to a target value, adapts the opening of the gas valve from a first to a second opening value according to a stored nominal value, the second opening value between a stored upper and a lower limit, and wherein during the transition of the opening of the gas valve from the first to the second opening value, no control of the fuel supply is performed; and means for controlling, after reaching the target value of the parameter corresponding to the burner load, operating parameters of the firing device. The control after the control step can be done, for example, as in the control method described above.

The gas valve may comprise an actuator, in particular a stepper motor, a pulse width modulated or an electrical size controlled coil.

The firing device preferably has at least one mass flow sensor and / or volume flow sensor for measuring the amount of air supplied to the firing device per unit time and / or the amount of fuel medium supplied per unit time and / or the amount of the mixture of air and fuel medium supplied.

In particular, the firing device in the region of the burner flame may have a device for measuring a temperature generated by the firing device.

The temperature sensor may be arranged, for example, in the region of the flame, but also on the burner in the vicinity of the flame. For example, a can also Thermocouple can be used as a temperature sensor.

Fig. 1

eine Feuerungseinrichtung;

Fig. 2

eine Kennlinie, die bei der Durchführung des Regelungsverfahrens verwendet wird;

Fig. 3

eine Kennlinie, wie sie zur Durchführung des erfindungsgemäßen Verfahrens verwendet wird; und

Fig.4

eine schematische Darstellung eines Aufbaus einer Regelung zur Durchführung eines Verfahrens.

Further features and advantages of the subject of the invention will become apparent from the following description of specific embodiments. Show it:

Fig. 1

a firing device;

Fig. 2

a characteristic used in the implementation of the regulatory procedure;

Fig. 3

a characteristic curve, as used for carrying out the method according to the invention; and

Figure 4

a schematic representation of a structure of a scheme for performing a method.

FIG. 1 shows a gas burner in which a mixture of air L and gas G is premixed and burned.

The gas burner has an air supply section 1, is sucked through the combustion air L. A mass flow sensor 2 measures the mass flow of the air L sucked in by a blower 9. The mass flow sensor 2 is arranged so that as laminar a flow as possible is generated in its surroundings in order to avoid measurement errors. In particular, the mass flow sensor could be arranged in a bypass (not shown) and using a laminar element.

In the air supply section 1, a valve 3 may be arranged for the combustion air. However, however, usually a regulated fan with air mass flow sensor will be used, so that the valve can be omitted.

For the gas supply, a gas supply section 4 is provided, which is connected to a gas supply line. The gas flows through the section 4, during operation of the gas burner. Through a valve 6, which may be an electronically controlled valve, the gas flows through a conduit 7 into the mixing region 8. In the mixing region 8, a mixing of the gas G with the air L takes place. The fan of the fan 9 is driven at an adjustable speed to suck in both the air L and the gas G.

The valve 6 is adjusted so that, taking into account the other operating parameters, such as the speed of the fan, a predetermined air-gas ratio enters the mixing area 8. The air-gas ratio should be chosen so that the most clean and effective combustion takes place.

Via a line 10, the air-gas mixture flows from the blower 9 to the burner part 11. There it exits and feeds the burner flame 13, which is to deliver a predetermined heat output. On the burner part 11, a temperature sensor 12, for example a thermocouple, is arranged. With the aid of this thermocouple an actual temperature is measured, which is used in carrying out the method described below for controlling or controlling the gas burner. In the present example, the temperature sensor 12 is arranged on a surface of the burner part 11. However, it is also conceivable to arrange the sensor elsewhere in the area of action of the flame 13. The reference temperature of the thermocouple is measured at a position outside the effective range of the flame 13, for example in the air supply line 1.

A device, not shown, for controlling or regulating the air and / or gas flow receives input data from the temperature sensor 12 and the mass flow sensor 2 and outputs control signals to the valve 6 and to the drive of the blower 9. The opening of the valve 6 and the speed of the fan of the fan 9 are adjusted so that the desired air and gas supply results.

The control is carried out by performing the method described below. In particular, the control device has a memory for storing characteristic curves or nominal values as well as a corresponding data processing unit which is set up to carry out the corresponding methods.

The first method is based on the FIG. 2 described. In FIG. 2 a characteristic curve is shown, in which the target temperature T _soll is plotted as a function of a mass flow m _{L of} the combustion air to be supplied to a gas burner. How out FIG. 2 it can be seen, while the mass flow of the combustion air at a constant air ratio is given a temperature. For other values of the air ratio λ, another dependence of the setpoint temperature T _soll on the air mass flow m _{L would} result. The method is based on the observation that the belonging to a certain value of the mass flow of the combustion air for a given air ratio Target temperature T _should not depend on the type of gas. The method thus works independently of gas types. The air ratio λ is chosen so that the most hygienic and efficient combustion is achieved. For example, a value λ = 1.3 can be specified. In carrying out the method with the specified air ratio λ thus effective control is achieved regardless of the gas type and quality.

To illustrate the method, a change starting from an operating state 1 to an operating state 2 is assumed. The change of the operating state requires a load change, for example, a changed heat request. The operating state 1 corresponds to an air mass flow m _L1 , the operating state 2 is an air mass flow m _L2 . The burner load is at a constant air ratio λ substantially proportional to the mass flow of both the air and the fuel.

In carrying out the method, first of all the new air mass flow m _L2 , starting from a burner _load Q _soll2 desired in operating state 2, is set. The air mass flow m _L can be measured on a mass flow sensor 2.

The corresponding opening of the gas valve is adjusted by means of the desired characteristic gas valve opening via mass flow

Instead of the mass flows and volume flows by means of a diaphragm with a pressure gauge or other parameters, such as the speed of the fan of the fan 9, could be detected.

After the adjustment of the air mass flow m _L2 and the gas valve, the actual temperature T measured at the temperature sensor 12 in the area of the burner flame 13 _is setpoint temperature T _Soll2 corresponding to the newly set air mass flow m _L2 according to the characteristic curve FIG. 2 compared.

If there is a deviation between the actual value and the setpoint, readjustment takes place. The readjustment is carried out by a leaning or enrichment of the air-gas mixture by actuation of the gas valve 6. The gas valve 6 is adjusted so long until the control process is completed, that is, until one of the _Target temperature T _soll2 corresponding actual temperature T _has set.

Instead of absolute actual and desired temperatures, temperature differences .DELTA.T can _be, .DELTA.T _{is intended} as, for example, measured by a thermocouple may be used. Instead of the set temperature T _set can _be plotted as a function of air mass flow m _L corresponding to a thermal voltage U. The reference temperature of the thermocouple 12 may be measured, for example, in the air supply section 1, in a burner area outside the effective range of the burner flame 13 in the vicinity of the burner.

In the FIG. 2 The characteristic curve shown can be represented empirically or mathematically. For fast control, the use of a low thermal inertia sensor 12 located close to the flame 13 would be advantageous. Sheathed thermocouples with a mantle of materials suitable for high temperature oxidation processes have proven particularly effective and stable. To increase the life of the temperature sensor 12 and to protect against overloading, it is advisable to install the sensor in a region which has a certain distance from the flame 13. The measured temperatures T _is moving, depending on the mounting location, burner load Q and _to air ratio λ between 100 and 1000 ° C.

For gas heaters with low degrees of modulation, errors due to variations in ambient temperature and pressure as well as gas pressure, resulting in varying ratios between mass air flow and gas mass flow, can be neglected in the practice of the method. Here, in comparison to the mass flow measurement of the combustion air usually more cost-effective volume flow measurement can be applied.

Based on FIG. 3 another method is explained.

In FIG. 3 is a function of the opening w of the gas valve 6, which determines the fuel supply as a function of the mass flow m _L of the air supplied to the burner. In this case, the mean curve K3 corresponds to a desired value curve which indicates the predetermined opening values w _{soll of} a gas valve 6 as a function of a corresponding air mass flow m _L.

When the prescribed burner load Q changes, for example when the operating state changes or when the system is started, the air mass flow m _{L is changed} from an initial value m _L1 to a second value m _L2 and adapted to the new load Q ₂ .

Since a control of the gas supply would be greatly delayed in time at the relatively short transition from m _L1 to m _L2 due to the inertia of the sensors, the control is switched off and the opening value w of the gas valve from previously set value w _{1 changed} to a new target opening value w ₂ , The value w ₂ lies on the desired opening curve K3.

The adjusting opening of the gas valve is in any case between an upper limit curve K1 and a lower limit curve K2, which indicate a tolerance range for the opening of the gas valve. The upper limit curve K1 corresponds to a maximum allowable opening of the gas valve, the lower limit curve K2 a minimum allowable opening of the gas valve. 6

This is followed by a control process. In the control process, the operating parameters of the firing device, in particular the setting of the valve 6 and the speed of the fan of the fan 9 are adjusted so that the combustion process is optimized. The scheme can be done in any way. In the present example it is done by measuring a generated by the burner flame 13 in its sphere of temperature T _is 12 by a temperature sensor The control can for example take place as in the method described above.

It is useful to use pulse width modulated valves, electronically controlled valves or valves with a stepper motor actuated actuator. The control signal for adjusting the opening of the gas valve can accordingly trigger, for example, the operation of a stepping motor, or change the pulse width, the voltage or the current of a coil. The air mass flows m _L and gas mass flows m _G are measured by mass flow sensors 2 and 5.

If, in one phase of the method, a valve opening w is set before or after the control process has been carried out, which is above the upper limit curve K1 or below the lower limit curve K2, then corresponding consequences can ensue to be pulled. For example, leaving the tolerance range between K1 and K2 can lead to a calibration process. During calibration, the conditions set after the control could be stored in a memory of the controller and used for the next start. The setpoint curve K3, like the limit curves K1 and K2, can be shifted so that a uniform tolerance corridor for the opening of the gas valve 6 around the setpoint curve K3 also results in the new curve.

Alternatively, exceeding the limit curves K1 or K2 upwards or downwards after a certain period of time or when repeatedly exceeding or falling below may cause the device to be switched off. It may happen that certain gas burner settings change over time or certain boundary conditions have changed so that a safety hazard occurs or the gas burner operates in a non-effective operating state. A deviation of the opening of the gas valve from the permitted corridor can be triggered for example by a deviation of the gas pressure from the permissible inlet pressure range or by a malfunction of the sensors. The shutdown can thus be interpreted as an indication that a review and maintenance of the device is required.

By means of the method described, it can be ensured that, until an effective control of the gas supply can start, a plausible opening w _{2 of} the gas valve is set by the control, be it during a load change of the gas burner or in the starting phase. In this way it can be prevented that, for example, the flame goes out during the load change.

By the method is ensured at the start of the burner, that in a wide range, adapted to the predetermined burner load, can be ignited. During load changes, a quick adjustment of the gas supply to the new load takes place before the fine adjustment is found by a subsequent control.

In FIG. 4 schematically and exemplarily a control device for performing one of the methods according to the invention is shown.

The measured air mass flow m _L and the temperature measured in the region of the burner flame actual temperature _T of the control device serve as input signals. As can be seen from the representation of the characteristic curve in diagram A, the air mass flow is m _L directly proportional to the load of the burner Q. According to the characteristic curve shown in diagram B, the speed n of the fan, which is proportional to the heat output, is read from the determined load and set accordingly.

(The upper right optional function only serves to fool an existing firing automaton an input speed.) This part of the graph should be deleted as it only adds to the confusion.)

On the other hand, is shown with load changes from the input air mass flow m _L, as shown in diagram C, the nominal temperature T _nom determined the burner flame. For a certain air mass flow, a setpoint temperature is specified. In a node D, this target temperature T _{soll is} compared with the measured actual temperature T _ist . If a temperature difference .DELTA.T results, then a control process begins, which is continued until the actual temperature T _ist corresponds to the setpoint temperature T _soll . An approximation of the actual temperature T _is to the target temperature T _soll , as shown schematically by the diagram E, by actuating the stepping motor of a gas valve, which determines the fuel supply m _G , changed. This results in enriching or leaning of the fuel-air mixture, which leads to an increase or decrease in the temperature generated by the burner.

The diagram F shows the opening of the gas valve in the form of the step setting of the stepping motor of the gas valve as a function of the air mass flow m _L. The curves (1) and (2) indicate an upper or lower limit curve. For a given mass air flow m _L , the opening of the gas valve must always be in the target corridor defined by curves (1) and (2), during and after the control operations. In the case of deviations upwards or downwards, a corresponding measure can be initiated. For example, the gas burner can be shut down to eliminate safety risks or ineffective operation. It can also be just a warning or recalibration of certain characteristics are performed.

Claims (11)

Method for controlling a firing device, in particular a gas burner, characterized in that
changing a parameter (m _L , V _L ) corresponding to the burner load (Q) from a starting value (Q ₁ ) to a target value (Q ₂ ), the fuel supply to the firing device by changing the opening of a gas valve (6) a first (w ₁ ) to a second opening value (w ₂ ) under specification of a desired value, which depends on the parameter (m _L , V _L ) is adjusted, wherein the second opening value (w ₂ ) between an upper and a lower limit and wherein during the transition of the opening of the gas valve from the first (w ₁ ) to the second opening value (w ₂ ) no control of the fuel supply performed and after reaching the target value of the parameter (m _L , V _L ) corresponding to the burner load (Q) , a control of operating parameters of the firing device is performed. A method according to claim 1, characterized in that the parameter corresponding to the burner load (Q), the firing device per unit time to be supplied air quantity, in particular a mass flow (m _L ) or volume flow (V _L ) of the firing device to be supplied air. A method according to claim 1 or 2, characterized in that the burner load (Q) is substantially proportional to the gas burner supplied amount of air per unit time (m _L , V _L ). Method according to one of the preceding claims 1 to 3, characterized in that the change of the opening of the gas valve by the modulation of a pulse width, by the variation of a voltage or current of a valve coil, or by operating a stepping motor of a valve is performed. Method according to one of the preceding claims 1 to 4, characterized in that an exceeding of the upper or the lower limit of the opening is detected. Method according to one of the preceding claims 1 to 5, characterized in that a characteristic which results from the nominal values for the opening (w) of the gas valve as a function of the parameter (m _L , V _L ), that of the burner load (Q) is recalibrated based on the operating parameters of the firing device set by the control. Method according to one of the preceding claims 1 to 6, characterized in that an exceeding of the upper or falls below the lower limit, in particular after the expiration of a predetermined period of time, leads to switching off the firing device. Firing device, in particular gas burner, comprising: a gas valve (6) for adjusting the fuel supply to the firing device; a memory for storing set values depending on a parameter (m _L , V _L ) corresponding to the burner load (Q) and upper and lower limits; means for controlling the opening of the gas valve which, when the parameter (m _L , V _L ) corresponding to the burner load (Q) changes from a starting value to a target value, the opening of the gas valve from a first (w ₁ ) to a second opening value (w ₂₎ adjusts under specification of a stored desired value, wherein the second opening value (w ₂₎ between a stored upper and a lower limit value, and wherein (during the transition of the opening of the gas valve from the first (W ₁₎ to the second opening value w ₂ ) no control of the fuel supply is carried out; and Control means which, after reaching the target value of the parameter corresponding to the burner load (Q), regulate operating parameters of the firing device. Firing device according to claim 8, characterized in that the gas valve (6) comprises an actuator, in particular a stepper motor, a pulse width modulated or controlled by an electrical size coil. Firing device according to one of claims 8 or 9, characterized in that the firing device at least one mass flow sensor (2, 5) and / or volume flow sensor for measuring the firing device per unit time supplied amount of air (m _L , V _L ) and / or supplied per unit time Amount of fuel medium (m _G , V _G ) and / or the amount of the supplied mixture (m _M , V _M ) from air and fuel medium. Firing device according to one of claims 8 to 10, characterized in that the firing device in the region of the burner flame (13) comprises means (12) for measuring a temperature (T _ist ) generated by the firing device.

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