EP2957831A1 - Burner and method for operating same - Google Patents

Abstract

The invention relates to a burner and a method for controlling the burner, the burner comprising a fuel metering device and a burner tube, the fuel metering device comprising a pulsation device, the pulsation device being configured to control a fuel flow between a first predefined lower threshold value and a second predefined upper threshold value to vary during a burning process.

Description

The invention relates to a burner according to claim 1 and a method for operating such a burner according to claim 10.

State of the art

Burners are known which have a flute-like structure to heat water in hot water stations in a heat exchanger. In this case, the burner has an inlet side and an outlet side, wherein a flame is present on the outlet side during a combustion process. On the inlet side, a gas nozzle is arranged, which continuously provides fuel with the same amount. Further, the fuel stream sucks in an air flow, with which it is mixed to be burned on the exhaust side in a flame.

It is an object of the invention to provide an improved burner, as well as an improved method of operating such a burner.

Disclosure of the invention

This object is achieved by means of a burner according to claim 1. Advantageous embodiments are given in the dependent claims.

According to the invention, it has been recognized that an improved burner can be provided in that the burner has a fuel metering device and a burner tube. Furthermore, the metering device comprises a pulsation device. The Pulsiereinrichtung is formed, the fuel flow between a first predefined lower threshold and a second predefined upper threshold during firing.

This ensures that a vortex is formed inside the burner tube, which ensures improved mixing of the fuel with a reactant of the fuel, so that possible harmful exhaust gases are reduced. In particular, while NO _{x are} reduced.

It has proven to be advantageous if the burner tube has an inlet side and an outlet side. Additionally or alternatively, the fuel metering device can be connected to a fuel reservoir and connected to the burner tube and configured to meter a predefined fuel flow of a fuel from the fuel reservoir into the burner tube.

In particular, it is advantageous if the burner tube is designed to guide the fuel introduced into the burner tube together with a reactant introduced into the burner tube of the fuel to the outlet side and to mix with each other to at least the fuel at the outlet side during a combustion process with the reactants partly to burn.

In this case, it is particularly advantageous if the fuel flow of the second threshold value is at least 10 percent greater, preferably 15 percent, in particular at least 30 percent greater than the first threshold value.

A particularly simple control of the burner can be ensured that at the first threshold value of the fuel flow is substantially interrupted.

A particularly stable vortex forms within the burner when the thresholds alternate at a frequency of 10 to 20 Hz and / or 20 to 30 Hz.

In a further embodiment, the pulsation device is designed to continuously or discontinuously change the fuel flow between the first and the second threshold value. The continuous transition has the advantage that a break in the flame and thus a termination of the burning process is avoided. The discontinuous fuel flow has the advantage that the turbulence in the interior of the burner tube is forced and thus improved mixing of the fuel can be ensured with its reactants.

In a further embodiment, a buffer section is provided between the inlet side and the outlet side of the burner tube. The pulsation device conveys a predefined volume of the fuel into the burner tube within a variation portion of the fuel flow from the first threshold to the second threshold and from the second threshold to the first threshold. The buffer section is configured to receive at least the volume of the fuel guided within the variation section into the burner tube and the volume of the reactant conveyed for the combustion during the variation section. This avoids pressure fluctuations or fluctuations in a flame height on the outlet side.

In a further embodiment, the fuel metering device comprises a control unit and the pulsation device comprises a control valve, wherein the control valve is connected to the control unit, wherein the control unit is designed to adjust a valve position of the control valve between an open position and a closed position.

Furthermore, it is advantageous if the control device comprises an input device, wherein the control device is designed to determine the valve position for the first threshold value and the second threshold value on the basis of a predefined parameter. In this case, the input device may be, for example, another control device of a heater, but also, of course, an input device for determining the burner output.

However, the object is also achieved by a method for controlling a burner according to claim 10.

It has been recognized in accordance with the present invention that an improved method of controlling a burner as described above may be provided by varying a fuel flow between a first predefined lower threshold and a second predefined upper threshold during a firing operation.

It is advantageous if in the burner tube of the fuel and the reactant of the fuel are fed into the burner tube and mixed together to at least partially burn the fuel with the reactant on the outlet side during the firing process with the reactants.

• Figur 1 eine schematische Darstellung eines Brenners gemäß einer ersten Ausführungsform;
• Figur 2 ein Diagramm eines Brennstoffstroms des in Figur 1 gezeigten Brenners aufgetragen über einer Zeit;
• Figur 3 ein Diagramm eines Brennstoffstroms des in Figur 1 gezeigten Brenners aufgetragen über einer Zeit;
• Figur 4 eine schematische Darstellung eines Brenners gemäß einer zweiten Ausführungsform;
• Figur 5 ein Diagramm eines Brennstoffstroms des in Figur 4 gezeigten Brenners aufgetragen über einer Zeit;
• Figur 6 eine schematische Darstellung eines Brenners gemäß einer dritten Ausführungsform; und
• Figur 7 eine schematische Darstellung eines Brenners gemäß einer vierten Ausführungsform.

The invention will be explained in more detail with reference to figures. Showing:

• FIG. 1 a schematic representation of a burner according to a first embodiment;
• FIG. 2 a diagram of a fuel flow of the in FIG. 1 shown burner applied over a time;
• FIG. 3 a diagram of a fuel flow of the in FIG. 1 shown burner applied over a time;
• FIG. 4 a schematic representation of a burner according to a second embodiment;
• FIG. 5 a diagram of a fuel flow of the in FIG. 4 shown burner applied over a time;
• FIG. 6 a schematic representation of a burner according to a third embodiment; and
• FIG. 7 a schematic representation of a burner according to a fourth embodiment.

FIG. 1 shows a schematic representation of a burner 10 according to a first embodiment. The burner 10 includes a fuel metering device 15 and a burner tube 20. The burner tube 20 has an inlet side 25 and an outlet side 30. During operation of the burner 10, an air stream 35 used as a reaction partner is removed from an environment 40 on the inlet side 25 and guided into an interior 45 of the burner tube 20. Further, a gas nozzle 46 of the Brennstoffdosiereinrichtung 15 is arranged on the inlet side 25, through which a fuel flow 50 is guided in the operation of the burner 10 in the inlet side 25. In the interior 45, a fuel of the fuel stream 50 is mixed together with the air flow 35 and guided to the outlet side 30. On the outlet side 30, in the embodiment, by way of example, a plurality of openings 55 are provided, through which the air-fuel mixture exits and burns above the outlet side 30 in a flame 56 during a firing process. In this case, a combustion process is understood to mean that the flame 56 is continuously present on the outlet side 30 during the firing process and is not extinguished. With the extinction of the flame 56 and a reignition of the flame 56 begins in the context of the application, a new, separate further burning process.

In the embodiment, the burner 10 is designed for hot water stations. Of course, it is also conceivable that the burner 10 is used in other thermal systems, in particular for heating buildings, in order to heat a heat transfer medium by means of a heat exchanger 150 arranged above the outlet side 30.

The metering device 15 has a control unit 60 and a pulsation device 65. The pulsation device 65 has a control valve 90 and an actuator 95 connected to the control valve 90. The actuator 95 is connected to the control valve 90 and adapted to move the control valve 90 between an open position and a closed position. The actuator 95 is connected to the controller 60 via a first connection 70. Furthermore, that is Control valve 90 via a first line 75 with a fuel reservoir 80, which may be, for example, a gas tank connected. Via a second line 85, the control valve is connected to the gas nozzle 46.

In the open position, the control valve 90 connects the first line 75 to the second line 85 so that a gas 100 arranged in the fuel reservoir 80 can flow from the fuel reservoir 80 via the first line 75 and the control valve 90 into the second line 85. From the second conduit 85, the gas flows toward the gas nozzle 46 and exits the gas nozzle 46 at an outlet opening 105 of the gas nozzle 46 and flows via the inlet side 25 as fuel stream 50 into the burner tube 20.

In the embodiment, for example, the actuator 95 may have a piezoelectric element that performs a predefined stroke when an electrical voltage is applied. By means of the stroke, the control valve 90 can be moved between the open position and the closed position. Of course, it is also conceivable that the pulsation device 65 is designed as a pressure valve. It is also conceivable that the actuator 95 is designed differently. For example, it is conceivable that the control valve 90 has a control disk with an opening, wherein the actuator 95 rotates the control disk, so that the control valve 90 is alternately opened and closed.

The control unit 60 has a control device 110, a memory 115 and an interface 120. The interface 120 is connected to the control device 110 via a second connection 125. The memory 115 is connected to the control device 110 via a third connection 130. In the memory 115, a first and a second parameter are stored. The first and / or second parameter developed characteristic filed. Of course, it is also conceivable that the parameter is a mathematical function, a map or a tabular assignment.

The interface 120 is connected to an input device 140 via a fourth connection 135. The interface 120 is formed in the embodiment as a mechanical connection of the controller 60 to the fourth connection 135. Of course, it is also conceivable that the interface 120 has its own logic and is designed, for example, as an analog-to-digital converter.

The input device 140 is designed as a further control device of a thermal system (not shown). The input device 140 provides a default signal with information about a requested by the burner 10 heating power. The default signal is transmitted via the fourth connection 135 to the interface 120. The interface 120 provides the default signal over the second connection 125 to the controller 110. The control device 110 detects the default signal. On the basis of the first parameter stored in the memory 115, the control device 110 determines the fuel flow 50 to be provided by the fuel metering device 15.

FIG. 2 shows a diagram of in FIG. 1 Fuel flow F flowing in the burner tube 20 is plotted over a time T. In this case, the fuel flow F fluctuates between a first lower threshold value S ₁ and a second upper threshold value S ₂ , which is different from the lower threshold value S ₁ . At the first lower threshold S ₁ , the control valve 90 is in the closed position, so that the fuel flow 50 is interrupted by the gas nozzle 46 in a first time interval T ₁ . In a second time interval T ₂ , the control valve 90 is in the open position, so that the fuel flow 50 flows constantly through the outlet opening 105 of the gas nozzle 46. The two time intervals T ₁ and T ₂ alternate with each other, so that the fuel stream 50 emerges in pulses from the gas nozzle 46. The two time intervals together form a variation section V. In this case, the fuel flow 50 is understood as the variation section V over the two time intervals T ₁ T ₂ , that is, from the first threshold value S ₁ to the second threshold value S ₂ and back in time.

After determining the fuel flow 50 corresponding to a predefined heat output, the control device 110 determines the two threshold values S ₁ , S ₂ and the two time intervals T ₁ , T ₂ on the basis of the second parameter stored in the memory 115. In this case, if the control valve 90th is moved exclusively between the open position and the closed position, by means of a length of the time intervals T ₁ , T ₂ fuel flow 50 varies.

For example, to reduce the fuel flow 50, it is conceivable to extend the length of the first time interval T ₁ compared to the second time interval T ₂ . If the fuel stream 50 provided via the gas nozzle 46 is integrated over the time T, a mean fuel flow 51 (in FIG FIG. 2 shown in dashed lines), which is reduced in amplitude from the second threshold S ₂

It is particularly advantageous if the threshold values S ₁ , S _{2 are} alternately driven by the control valve 90 at a frequency of 10 to 20 Hz and / or from 20 to 30 Hz. This ensures an increase in turbulence within the burner tube 20, so that the air flow 35 is better mixed with the fuel stream 50. In particular, a toroidally extending vortex is thereby generated in the interior 45 of the burner tube 20, which further promotes air-fuel mixing. This has the consequence that a particularly homogeneously mixed lean air-fuel mixture is provided on the outlet side 30, which leads to a reduction of nitrogen oxides in the exhaust gas of the burner 10.

FIG. 3 shows the fuel flow 50 plotted against time at a sinusoidal control of the control valve 90. The two time intervals T ₁ , T _{2 are} identical. It should be noted that the fuel flow 50 can also be varied by means of a function other than that shown between the two threshold values S ₁ , S ₂ . To the in FIG. 3 Based on the second parameter, the control device 110 additionally determines the different valve positions of the control valve 90 in order to achieve the fuel flow 50 and takes these into account in the control of the control valve 90.

Further, the fuel flow 50 may be either by changing the frequency of the change between the first threshold S ₁ and the second threshold S ₂ and / or changing the values of the first threshold S ₁ and / or the second threshold S ₂ . there the change between the two threshold values S ₁ , S _{2 takes place} continuously, so that the fuel flow 50, which flows through the outlet opening 105 into the interior 45 of the burner tube 20, is not interrupted. At the same time, the variation between the two threshold values S ₁ , S ₂ further improves the vortex formation and the forcing of the mixing of the fuel in the interior 45 of the burner tube 20 with the air.

It has proved to be particularly advantageous if the second threshold value S _{2 is} at least 10 percent greater, preferably 15 percent, in particular at least 30 percent, particularly advantageously greater than 50 percent greater than the first threshold value S ₁ .

If, over time, the fuel flow 50 is integrated, the average fuel flow 51 is obtained. The second threshold value S ₂ is 15 to 30 percent, advantageously 18 to 25 percent higher than the average fuel flow 50. This applies in particular if the change between the fuel stream 50 first threshold value S ₁ and the second threshold value S ₂ with a frequency of 10 Hz. At higher frequencies, for example in a frequency range from 20 to 30 Hz, it is advantageous if the second threshold S _{2 is} 10 to 20 percent, in particular 15 percent higher than the average fuel flow 50.

FIG. 4 shows a schematic representation of a burner 200 according to a second embodiment. The burner 200 is substantially identical to that in FIG FIG. 1 shown burner 10 is formed. Deviating from this, the metering device 15 has a plurality of gas nozzles 205, 210, 215, 220. Of course, a different number of gas nozzles 205, 210, 215, 220 is conceivable. In this case, a first gas nozzle 205 is connected via a second line 225 to a first pulsation device 230. A second pulsing device 235 is connected to the second gas nozzle 210 via a third line 240. A third pulsing device 245 is connected via a fourth line 250 to the third gas nozzle 215. A fourth pulsing device 255 is connected via a fifth line 260 to the fourth gas nozzle 220. The pulsing devices 230, 235, 240, 255 are each connected via a line 265 to the control unit 60.

In FIG. 5 is shown by a solid line of the inflowing over the inlet side 25 fuel flow 50 as the total fuel flow. Fuel line 50, which emerges from in each case one of the four gas nozzles 205, 210, 215, 220, is shown by means of a dashed line. The mean fuel flow 51 is also obtained by integrating the fuel streams 50 flowing out of the various gas nozzles 205, 210, 215, 220. The average fuel flow 51 is in amplitude with respect to the second threshold S ₂ as in FIG FIG. 3 described reduced.

Depending on the second parameter, the control unit 60 alternately controls the pulsing devices 230, 235, 245, 255 in such a way that the pulsation devices 230, 235, 245, 255 each form a fuel flow 50 through the associated gas nozzle 205, 210, 215, 220. which has seen approximately over time a trapezoidal course.

In the embodiment, the control valve 90 of the first pulsation device 230 is first opened while the other control valves 90 of the further pulsation devices 235, 245, 255 are closed. While the control valve 90 of the first pulsation device 230 is closed, the control valve 90 of the second pulsation device 235 is then already opened during the closing process. Also, the opening and closing operation of the control valves 90 of the second, third and fourth pulsation means 235, 245, 255 is continued, and upon closing the control valve 90 of the fourth pulsation means 255, the opening of the control valve 90 of the first pulsation means 230 is started again an overlap of the individual fuel streams 50, exiting from the respective gas nozzles 205, 210, 215, 220, achieved, so that the total fuel flow is continuous and pulsating over time T. This ensures that the position of the gas flow is also temporally changed. Of course, it is also conceivable that two control valves 90 and two pulsation devices 230, 235, 245, 255 are opened and closed in parallel.

Also by the different arrangement of the gas nozzles 205, 210, 215, 220 in combination with the alternating opening and closing of the control valves 90 of the pulsing means 230, 235, 245, 255, a vortex formation in the interior 45 of the burner tube 20 improves, with which the fuel is mixed faster with the air flow 35.

FIG. 6 shows a schematic representation of a burner 300 according to a third embodiment. The burner 300 is substantially identical to the one in FIG FIG. 4 formed burner 200 is formed. Deviating from this, a fifth gas nozzle 305 is additionally provided on the inlet side 25 of the burner tube 20, which is connected to a fifth pulsing device 310 via a sixth line 315. On the representation of in FIG. 4 shown pulsing devices 230, 235, 245, 255 has been omitted for clarity. On the inlet side 25 a plurality of stages 320, 325, 330 are provided. In this case, the fifth gas nozzle 305 opens in the first stage 320. The second gas nozzle 220 and the third gas nozzle 215 open in a second stage 325, while the first gas nozzle 205 and the fourth gas nozzle 220 open in a third stage 330. The various stages 320, 325, 330 have a different length extension, so that the first stage 320 terminates in the second stage 325 and the second stage 325 terminates in the third stage 330. The steps 320, 325, 330 all end in the interior 45 of the burner tube 20.

Will, as in FIG. 4 and 5 described, alternately via the gas nozzles 205, 210, 215, 220, 305 promoted fuel in the burner 300, so takes place on the steps 320, 325, 330 laterally of the gas nozzles 205, 210, 215, 220 as well as a suction of the air stream 35, which is then already mixed in the respective stage 320, 325, 330 with the fuel stream 50 exiting via the gas nozzle 205, 210, 215, 220, 305. The blended air-fuel mixture is then mixed again in the further stages 325, 330 with the air-fuel stream flowing therefrom. As a result, a particularly good mixing in the interior of the burner 300 can take place.

FIG. 7 shows a schematic representation of a burner 400 according to a fourth embodiment. The burner 400 is substantially identical to the one in FIG FIG. 4 embodiment 200 shown formed. In addition, on the output side, a buffer section 405 is provided in the interior 45 of the burner tube 20. The buffer section 405 takes at least that within the variation section V (see FIG. Figures 2 . 3 . 5 ) guided in the burner tube 20 Volume of the fuel and necessary for the combustion of the subsidized during the Variation section fuel volume necessary for the fuel flow of air. The buffer section 405 is preferably delimited from the further interior 45 of the burner tube 20 by means of a delimiting device 410 (shown in dashed lines) and arranged on the output side of the burner tube 20 or upstream of the outlet side 30.

It should be understood that the above-described features of the various burners 10, 200, 300, 400 may of course be combined. It should also be noted that the gas nozzles 46, 205, 210, 215, 220, 305 may be arranged differently to each other. It is essential, however, that the gas stream leaving the gas nozzles 46, 205, 210, 215, 220, 305 is varied during a firing process, that is to say when a flame 56 continuously prevails on the outlet side 30, and the flame 56 is not extinguished.

Claims (10)

Burner (10; 200; 300; 400) having a fuel metering device (15) and a burner tube (20), - characterized in that the fuel metering device (15) comprises a pulsation device (65; 230, 235, 245, 255, 310), - wherein the pulsation means (65; 230, 235, 245, 255, 310) is adapted to vary a fuel flow (50) between a first predefined lower threshold (S ₁ ) and a second predefined upper threshold (S ₂ ) during a firing operation , Burner (10; 200; 300; 400) according to claim 1, characterized in that the burner tube (20) has at least one inlet side (25) and one outlet side (30), - and / or wherein the Brennstoffdosiereinrichtung (15) connected to a fuel reservoir and connected to the burner tube (20) and is adapted to meter a predefined fuel flow (50) of a fuel from the fuel reservoir into the burner tube (20), - And / or wherein the burner tube (20) is formed, in the burner tube (20) introduced fuel flow (50) together with a via the inlet side (25) into the burner tube (20) initiated reactant of the fuel stream (50) to the outlet side (30) and to mix with each other to at least partially burn the fuel at the outlet side (30) during a combustion process with the reactant. Burner (10; 200; 300; 400) according to claim 1 or 2, characterized in that - The fuel flow (50) of the second threshold value (S ₂ ) is at least 10 percent greater, preferably 15 percent greater, in particular at least 30 percent greater than the first threshold value (S ₁ ). Burner (10; 200; 300; 400) according to claim 3, characterized in that at the first threshold value (S ₁ ) the fuel flow (50) is substantially interrupted. Burner (10; 200; 300; 400) according to one of claims 1 to 4, characterized in that the threshold values (S1) alternate with a frequency of 10 to 20 Hz and / or from 20 to 30 Hz. A burner (10; 200; 300; 400) according to any one of claims 1 to 5, characterized in that the pulsation means (65; 230, 235, 245, 255, 310) is adapted to direct the flow of fuel (50) between the first and the second second threshold (S ₁ , S ₂ ) continuously changing or discontinuous change. Burner (10; 200; 300; 400) according to one of claims 2 to 6, characterized in that - between the inlet side (25) and the outlet side (30) of the burner tube (20), the burner tube (20) has a buffer portion (405), wherein the pulsation device (65; 230, 235, 245, 255, 310) within a variation section (T ₁ , T ₂ ) of the fuel flow (50) from the first threshold (S ₁ ) to the second threshold (S1) and the second threshold ( S ₂ ) to the first threshold (S ₁ ) promotes a predefined volume of the fuel in the burner tube (20), - Wherein the buffer portion (405) is formed, at least within the variation portion (T ₁ , T ₂ ) in the burner tube (20) guided volume of the fuel and for the combustion of during the variation section (T ₁ , T ₂ ) funded fuel necessary volume of the reactant. Burner (10; 200; 300; 400) according to one of claims 1 to 7, characterized in that the fuel metering device (15) comprises a control device (60) and the pulsation device (65; 230, 235, 245, 255, 310) comprises a control valve (60), - wherein the control valve (90) is connected to the control unit (60), - wherein the control device (60) is adapted to adjust a valve position of the control valve (90) between an open position and a closed position. A burner (10; 200; 300; 400) according to claim 8, characterized in that the control device (60; 230, 235, 245, 255, 310) is connectable to an input device (140), wherein the control device is designed, a default signal the input device (140) to detect and determine based on a predefined parameter, the valve position for the first threshold (S ₁ ) and the second threshold (S ₂ ) in response to the default signal. A method of controlling a burner (10; 200; 300; 400) according to any one of claims 1 to 9, wherein a fuel flow (50) between a first predefined lower threshold (S ₁ ) and a second predefined upper threshold (S ₂ ) during a Burning process is varied.

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