EP2534421B1 - Gas forced air burner having modulatable burner power and method for operating a gas forced air burner - Google Patents

Description

The invention relates to a gas blower burner with modulable burner power for a gas heater according to the preamble of claim 1, a method of operating a gas blower burner according to the preambles of claim 8 and a gas heater according to claim 11.

Gas fan burners with modulable burner performance (firing capacity) are well known. They are usually used to heat a heating fluid such as heating water or drinking water in a gas heater. In this case, combustion air is supplied to the burner via an air path and fuel gas via a gas path. The amount of air required for heating a Heizfluidstroms is conveyed in accordance with the predetermined burner capacity or the predetermined Heizfluidtemperatur means of a variable speed air blower in the air. The amount of gas corresponding to this amount of air is metered in the gas path with the aid of a gas valve. Air and fuel gas mix to a fuel gas-air mixture. For complete and low-emission combustion of the fuel gas, among other factors, a specific target composition of the fuel gas-air mixture is necessary. The aim is an excess of air (air ratio) λ _SOLL ≈ 1.3 compared to the stoichiometric minimum air requirement required for complete oxidation of the fuel. A so-called pneumatic gas air composite causes this mixture composition. An air flow meter arranged in the air measures the amount of the delivered amount of combustion air and gives an actuating signal to the gas valve, which releases a fuel gas amount corresponding to the desired composition of the fuel gas-air mixture.

Combustion air and fuel gas mix in a mixture formation section (mixing chamber), and a distribution space serves to approximately evenly distribute the fuel gas / air mixture quantity over the outlet cross section. The fuel gas-air mixture passes through a burner surface, which has the function of a flame holder in a combustion chamber, is ignited here by means of an igniter and burns with the release of heat. The heat of combustion is transferred in a heat exchanger to the heating fluid and this supplied to the use.

For the air flow measurement in the pneumatic gas air network, a Venturi nozzle is usually used because of the low pressure loss. The pressure difference between the inlet cross-section and the narrowest nozzle cross-section of the Venturi nozzle, which is proportional to the air volume flow, is measured, which acts as a control signal on a pneumatic gas control valve. There is a quadratic relationship between the flow rate variation and the differential pressure signal. Known devices for mixing fuel gas and air of the aforementioned type are capable of realizing throughput variations in a range of about 1: 5 (corresponding to a pressure variation of about 1:25), since the available pressure range on the one hand by the blower and on the other hand is limited by the required minimum response pressure of the pneumatic control valve. The limitation of the range variation range is accompanied by a similar limitation of the burner power range of a burner and the Heizleistungsmodulationsbereichs a gas heater.

Modern gas heaters with correspondingly modern gas jet burners have a comparatively low air ratio of λ ≈ 1.3 compared to previously customary burners. For example, the WO2006019279 A1 A gas blower burner according to the preamble of claim 1. The Wasserdampftaupunkttemperatur an exhaust gas depends on the air ratio of the combustion: With decreasing air ratio increases the dew point temperature. This results in a potential problem in the operation of modern gas heaters, namely the condensation of moisture contained in the exhaust gas to the cool combustion chamber walls and the cool surfaces of heat exchanger and exhaust pipe. This condensation is only allowed (and desirable) on condensing boilers since the components are designed accordingly. For conventional calorifiers, condensation must be avoided, otherwise moisture affected components could corrode and fail. A tendency to condensation is also favored by the device heating power or temperature. On surfaces of high temperature (high heat output) either no moisture precipitates or it can dry quickly. At low surface temperatures (low heat output), the dew point temperature tends to fall below and there is precipitation of moisture.

Another potential problem in heater operation are so-called thermoacoustic resonances, which can lead to excessive noise pollution and, due to the accompanying mechanical vibrations, also to component failure. Often, the resonance phenomena occur especially at low relative burner powers and low combustion chamber pressures.

In summary, it can be stated that an increase in the heating power range of a gas heater or an increase in the burner output range of a burner is desirable in order to be able to serve very different heating requirements, such as, for example, a domestic hot water tap for washing hands, a tapping process for inserting a bath or caused by heating an apartment. Nevertheless, even at the various possible operating points, the steam condensation from the exhaust gas and thermoacoustic resonance phenomena must be avoided. The invention is therefore based on the object to provide a gas blower burner with an extended burner power range as well as a method for its operation, which help avoid the water vapor condensation on Abgasberühren components and thermoacoustic resonance phenomena. The burner should have a simple and compact design.

This is achieved by the objects with the features of claims 1 and 8 according to the invention. Advantageous developments can be found in the dependent claims.

The gas blower burner according to the invention with modulable burner power for a gas heater with at least one air path for fan-assisted supply of combustion air, at least one gas path for supplying a fuel gas, a gas valve for quantity control of the fuel gas, at least one burner surface as a flame holder and at least one upstream of the burner surface arranged distribution space in the the combustion air and the fuel gas or a fuel gas-air mixture open, wherein the burner surface and the distribution chamber are divided into at least two areas, wherein a first burner surface area is associated with a first distribution space and a second burner surface area is associated with a second distribution space area, and wherein the gas path at a branch downstream of the gas valve and upstream of the distribution space is divided into at least two partial gas paths, each with an associated region of the distribution space in Verbin standing. In this case, the distribution space is structured by means of one or more at least partially permeable partition walls in at least two areas. With this design, the burner now has a burner surface which is split twice or several times and which can be supplied with fuel gas via the at least two partial gas paths and the at least two distribution chamber regions by means of a single gas valve. An overflow of combustion air or fuel gas-air mixture from a distribution area in an adjacent distribution area is possible. This permeability may be given in only one flow direction while a return flow is blocked, or the permeability may be given in both directions.

A suitable embodiment is characterized in that the branch in the gas path is dominated by a switchable two-way valve or multi-way valve. Thus, the fuel gas supply of the burner surface areas can be changed by means of a switching operation. For example, each burner surface area can be controlled individually and supplied with fuel gas, or several burner surface areas can be supplied simultaneously.

A further embodiment is characterized in that at least a first partial gas path is in direct communication with an associated first region of the distribution space, and that at least one second partial gas path is in indirect communication with an associated second region of the distribution chamber, this second partial gas path being in one with the Distribution room connected airway opens.

A suitable embodiment is characterized in that the partial gas paths each have separately predeterminable flow resistances. This can be e.g. reach through different path lengths, line diameter and fixed or adjustable throttle cross-sections. This ensures that with the help of a single gas control valve and despite the same control signal ranges from the air flow meter on the different partial gas paths different sized amounts of fuel gas can be metered.

An embodiment is characterized in that a fan is arranged in the air path, wherein the air path opens downstream into at least one region of the distribution space.

The burner surface may be formed as a perforated surface, for example as a perforated plate or wire mesh. The perforation can be the same or at least partially different over the different areas of the burner surface. By changing hole sizes, hole shapes, hole spacings, mesh pore sizes, mesh densities, etc. in the burner surface, different flow resistances can be realized.

A suitable embodiment is characterized in that at least one perforated distributor plate is arranged upstream of the burner surface in the distribution space divided according to the structure of the distribution space in at least two areas, and that the perforations of the areas of the distributor plate are at least partially formed differently. The distributor plate improves in a known manner the uniform distribution of a combustion air flow or a fuel gas-air mixture flow on the burner surface or the burner surface areas. Due to the different perforations of the distributor plate areas, different flow resistances can be realized.

• teilweise durch die dem zweiten Bereich des Verteilraums zugeordnete Brennerfläche in den Brennraum ausströmt, wobei dieser Teil der Verbrennungsluft als Sekundärluft im Wesentlichen nicht an der Verbrennung teilnimmt, und
• teilweise durch durchlässige Zwischenwände, die den Verteilraum in Bereiche untergliedern, in einen ersten Bereich des Verteilraums überströmt, sich hier als Primärluft mit dem Brenngas mischt, als Brenngas-Luft-Gemisch durch die dem ersten Bereich des Verteilraums zugeordnete Brennerfläche in den Brennraum ausströmt und der Verbrennung zugeführt wird.

The inventive method for operating a gas blower burner with modulable burner power, wherein a fuel gas when operating in a first burner power range, for example, a low burner power range, flows directly to a first region of a functioning as a flame burner surface, here mixed with combustion air to a fuel gas-air mixture and then the combustion is supplied, and when operating in a second burner power range, such as a high burner power range, the fuel gas flows through an air-carrying air path to a mixture formation path (mixing space), from where it continues as a fuel gas-air mixture to a second region of the Burner surface flows and then the combustion is supplied, is characterized in that for operating a gas blower burner in the range of low burner power, the sucked by the fan combustion air conveyed into a second region of the distribution space will and from there

• partially flows through the second area of the distribution chamber associated burner surface into the combustion chamber, said part of the combustion air as secondary air substantially does not participate in the combustion, and
• partially through permeable partition walls, which subdivide the distribution space into areas, flows into a first region of the distribution space, mixes here as primary air with the fuel gas, as fuel gas-air mixture through the first area of the distribution space associated burner surface flows into the combustion chamber and the Combustion is supplied.

With this invention, the fuel gas can be supplied to two different burner surface areas and thus cover a low and a high burner power range.

The fuel gas-air mixture in the first distribution area is such that an air ratio of λ ≈ 1.3 results. This guarantees complete and low-emission combustion at the first burner surface area. Secondary air flows through the second burner surface area, which mixes with the exhaust gas from the combustion and the resulting air ratio in the exhaust gas raises to, for example, λ = 1.5. This lowers the dew point temperature and reduces the tendency to condensation. The surfaces of the combustion chamber, heat exchanger and exhaust system remain dry, thus avoiding corrosion damage. The inflowing secondary air also increases the back pressure in the combustion chamber, which greatly reduces the susceptibility of the system to thermo-acoustic resonance phenomena.

• teilweise durch die dem zweiten Bereich des Verteilraums zugeordnete Brennerfläche in den Brennraum aus und
• teilweise durch durchlässige Zwischenwände, die den Verteilraum in Bereiche untergliedern, in den ersten Bereich des Verteilraums über und strömt durch die dem ersten Bereich des Verteilraums zugeordnete Brennerfläche in den Brennraum aus.

In a specific embodiment of the method for operating a gas fan burner in the range of high burner power, the fuel gas-air mixture, which has formed in the air and a mixture formation path (mixing chamber) of fuel gas and combustion air, promoted in a second region of the distribution space and flows from there

• partially through the second area of the distribution chamber associated burner surface in the combustion chamber and
• partly through permeable partition walls, which divide the distribution space into areas, in the first region of the distribution space and flows through the burner surface assigned to the first region of the distribution space in the combustion chamber.

In the combustion chamber both partial mixture streams are ignited and burned.

A suitable embodiment of the method for operating a gas blower burner with modulable burner power is defined in claim 10.

For example, the low burner power range covers the range between 4% and 20% of the rated burner output, while the high burner power range covers the range between 20% and 100% of the rated burner output. The procedure for mixture formation is different for these two burner power ranges. When operating in the first power range, the fuel gas flows through a first partial gas path directly and unmixed to a first distribution space area, at the same time the combustion space also flows combustion air. In the first distribution area, fuel gas and combustion air mix to form a fuel gas-air mixture. This exits through the burner area assigned to the first distribution area, is ignited and burnt. When operating in the second power range, the fuel gas flows through a second Teilgasweg to the airway and mixes with combustion air to a fuel gas-air mixture. The mixture is supplied to the distribution space, exits through the burner surface, is ignited and burned.

The inventive method allows a burner operation with extended modulation range and reduced tendency to water vapor condensation and thermoacoustic resonance phenomena. The burner according to the invention offers a simple and compact structure with which the method can be implemented.

Figur 1

einen Gasgebläsebrenner in Betrieb im hohen Brennerleistungsbereich und

Figur 2

einen Gasgebläsebrenner in Betrieb im niedrigen Brennerleistungsbereich.

The drawing schematically illustrates an embodiment of the invention and shows in the figures:

FIG. 1

a gas blower burner in operation in the high burner power range and

FIG. 2

a gas blower burner in operation in the low burner power range.

FIG. 1 shows a Gasgebläsebrenner invention for a gas heater with a combustion air inlet 1, an airway 2, an air flow meter 3, a fan 4, a fuel gas inlet 5, a gas path 6, a gas valve 7, a mixture forming section (mixing chamber) 8, a distribution chamber 9 and a burner surface 10th , To emphasize over known gas jet burners is the subdivision of the distribution space 9 and burner surface 10 in each case two areas 9-1 and 9-2 and 10-1 and 10-2, which are assigned to each other accordingly (9-1 / 10-1 and 9-2 / 10-2), wherein the distribution space 9 is divided into two by means of a permeable intermediate wall 11. Upstream of the burner surface 10 in the distribution space 9, a distributor plate 12 is provided. Also to emphasize is the branching of the gas path 6 in two partial gas paths 6-1 and 6-2. Partial gas path 6-1 communicates with the distribution area 9-1 and the burner area 10-1. Partial gas path 6-2 communicates via the air path 2 and the mixture formation section 8 with the distribution space region 9-2 and the burner surface region 10-2. Is shown in FIG. 1 an operation in the high burner power range, the combustion air, fuel gas and mixed streams are illustrated by arrows. At the junction of the gas path 6, a schematically illustrated switchable two-way valve 13 is arranged. This releases the fuel gas flow in the direction of the partial gas path 6-2, the other path 6-1 is blocked. The fuel gas flows into the airway 2, is sucked together with the combustion air from the fan 4, mixes with the combustion air in the airway 2, in the fan 4 and in the mixture formation section 8 to a fuel gas-air mixture. The mixture enters the second area 9-2 of the distribution space 9 and flows partly through the permeable partition 11 into the first distribution area 9-1. The permeable distributor plate 12 smoothes the mixture flow and distributes it to the two permeable burner surface regions 10-1 and 10-2. The fuel gas-air mixture is ignited by means of an igniter, not shown, forms flames 14 and burns with heat. The heat is arranged in a downstream of the burner, not shown here heat exchanger transferred to a heating fluid and fed to the use.

In FIG. 2 1, an operation of the gas blower burner is shown in the low burner power range, wherein the combustion air, fuel gas and mixed streams are again illustrated by arrows. The two-way valve 13 releases the fuel gas flow in the direction of the partial gas path 6-1, the other path 6-2 is blocked. The fuel gas flows through the partial gas path 6-1 in the distribution area 9-1. In this case, a fuel gas distributor 6-3 serves the uniform distribution of the fuel gas in the distribution area 9-1. Combustion air is sucked in by the blower 4 via the air inlet 1 and the air path 2. The air enters the second region 9-2 of the distribution chamber 9 and flows partly through a second region 12-2 of the distributor plate 12 and through the second burner surface region 10-2 into the combustion chamber. Another part of the combustion air flows through the permeable partition wall 11 further into the first distribution area 9-1. Here mixed the air with the fuel gas to a fuel gas-air mixture, wherein the fuel gas distribution device 6-3 is lapped with air, and flows through a first Verteilerplattenbereich 12-1 and through the first burner surface area 10-1 in the combustion chamber. Here, the fuel gas-air mixture is ignited again, forming flames 14 and burns with heat. The heat is arranged in a downstream of the burner, not shown here heat exchanger transferred to a heating fluid and fed to the use.

The gas blower burner can modulate (vary) burner output in both burner power ranges. For example, the low burner power range covers the range between 4% and 20% of the rated burner output, while the high burner power range covers the range between 20% and 100% of the rated burner output. Although the burner thus has a modulation ratio of 1:25, the fan 4 and the gas control valve 7 have to modulate but only in the ratio 1: 5. This is possible because the fuel gas flow on the two partial gas passages 6-1 and 6-2, if appropriate also in the distributor plate regions 12-1 and 12-2 and / or in the burner surface regions 10-1 and 10-2, has different flow resistances. The flow resistance in the partial gas path 6-1 is greater than that in the partial gas path 6-2. These flow resistances are fixed or variable during burner operation. With the same valve opening, the gas valve 7 is on the Teilgasweg 6-1 a smaller amount of fuel gas than via the Teilgasweg 6-2. Thus, operating the forced draft gas burner in a low and high burner power range is possible with only a conventional gas control valve 7 and a conventional blower 4. The gas control valve 7 works together with the air flow meter 3, for example in a pneumatic composite gas air circulation. The delivered air volume is used in the high burner power range completely as combustion air for the fuel gas-air mixture formation. In the low burner power range only a part of the air serves as combustion air for the fuel gas-air mixture formation; another part is unmixed with fuel gas from the burner surface and does not participate in the combustion.

Claims (11)

1. Gas blower burner with modulatable burner power for a gas heating appliance, having:

   • at least one air path (2) for the blower-assisted supply of combustion air,

   • at least one gas path (6) for the supply of a combustion gas,

   • a gas valve (7) for flow rate regulation of the combustion gas,

   • at least one burner surface (10) as flame holder, and

   • at least one distributor chamber (9) which is arranged upstream of the burner surface and into which the combustion air and the combustion gas or a combustion gas-air mixture issue,

   wherein

   • the burner surface (10) and the distributor chamber (9) are divided into at least two regions, wherein a first burner surface region (10-1) has associated therewith a first distributor chamber region (9-1), and a second burner surface region (10-2) has associated therewith a second distributor chamber region (9-2), and wherein

   • the gas path (6) splits, at a branch downstream of the gas valve (7) and upstream of the distributor chamber (9), into at least two partial gas paths (6-1, 6-2) which are each connected to an associated region (9-1, 9-2) of the distributor chamber (9), characterized

   
   in that the distributor chamber (9) is divided into the at least two regions (9-1, 9-2) by means of one or more at least partially permeable intermediate walls (11).
2. Gas blower burner according to Claim 1, characterized in that the branch in the gas path (6) is controlled by a switchable two-way valve (13) or multi-way valve (13).
3. Gas blower burner according to Claim 1 or 2, characterized

   • in that at least one first partial gas path (6-1) is directly connected to an associated first region (9-1) of the distributor chamber (9), and

   • in that at least one second partial gas path (6-2) is indirectly connected to an associated second region (9-2) of the distributor chamber (9), wherein said second partial gas path (6-2) issues into an air path (2) which is connected to the distributor chamber (9).
4. Gas blower burner according to one of Claims 1 to 3,
   characterized in that the partial gas paths (6-1, 6-2) each have separately predefinable flow resistances.
5. Gas blower burner according to one of Claims 1 to 4,
   characterized in that a blower (4) is arranged in the air path (2), wherein, downstream, the air path (2) issues into at least one region of the distributor chamber (9).
6. Gas blower burner according to one of Claims 1 to 5,
   characterized in that the burner surface (10) is perforated and in that the perforations of the at least two regions (10-1, 10-2) of the burner surface (10) are designed so as to at least partially differ.
7. Gas blower burner according to one of Claims 1 to 6,
   characterized in that, upstream of the burner surface (10) in the distributor chamber (9), there is arranged at least one perforated distributor plate (12) which, corresponding to the division of the distributor chamber (9), is divided into at least two regions (12-1, 12-2), and in that the perforations of the regions (12-1, 12-2) of the distributor plate (12) are designed so as to at least partially differ.
8. Method for operating a gas blower burner with modulatable burner power according to Claim 1, wherein a combustion gas,

   • during operation in a first burner power range, flows directly to at least one first region (10-1) of a burner surface (10) which functions as flame holder and said combustion gas is mixed here with combustion air to form a combustion gas-air mixture, and

   • during operation in a second burner power range, flows as a combustion gas-air mixture via an air-conducting air path (2) and a mixture formation path (8) to at least one second region (10-2) of the burner surface (10), and

   is then supplied for combustion,
   characterized in that, during operation in a range of low burner power, the combustion air is delivered into a second region (9-2), associated with the second burner surface region (10-2), of a distributor chamber (9) and, from there,

   • flows out partially through the second burner surface region (10-2) and

   • flows partially through intermediate walls (11), which divide the distributor chamber (9) into regions and which are at least partially permeable, into a first region (9-1), associated with the first burner surface region (10-1), of the distributor chamber (9), mixes here with the combustion gas, flows out as combustion gas-air mixture through the first burner surface region (10-1), and is supplied for combustion.
9. Method for operating a gas blower burner with modulatable burner power according to Claim 8, characterized in that, during operation in a range of high burner power, the combustion gas-air mixture is delivered into a second region (9-2) of the distributor chamber (9) and, from there,

   • flows out partially through the second burner surface region (10-2) and

   • flows partially through intermediate walls (11), which divide the distributor chamber (9) into regions and which are at least partially permeable, into a first region (9-1) of the distributor chamber (9) and flows out through the first burner surface region (10-1),

   and is supplied for combustion.
10. Method for operating a gas blower burner with modulatable burner power according to Claim 8 or 9, characterized

    • in that a blower (4) arranged in the air path (2) delivers an air flow rate, associated with a predefinable burner power, into at least one region (9-2) of a distributor chamber (9) which is divided into at least two regions,

    • in that a gas valve (7) regulates a combustion gas flow rate associated with the predefinable burner power, and

    • in that a two-way valve (13) or multi-way valve (13) arranged downstream of the gas valve (7) and upstream of the distributor chamber (9) determines the flow direction of the combustion gas as a function of the predefinable burner power,

    • wherein, during operation of the gas blower burner in a range of low burner power, the combustion gas flows directly to at least one first region (9-1) of the distributor chamber, mixes with combustion air in said region (9-1) of the distributor chamber, and is supplied for combustion, and

    • wherein, during operation of the gas blower burner in a range of high burner power, the combustion gas flows to the air path (2) which is connected to at least one second region (9-2) of the distributor chamber (9), mixes with combustion air in the air path (2) to form a combustion gas-air mixture, and is supplied to the distributor chamber (9) and for combustion.
11. Gas heating appliance having a gas blower burner with modulatable burner power according to one of Claims 1 to 7.

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