Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
  • F23D14/02—Premix gas burners, i.e. in which gaseous fuel is mixed with combustion air upstream of the combustion zone
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
  • F23D14/46—Details, e.g. noise reduction means
  • F23D14/70—Baffles or like flow-disturbing devices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23M—CASINGS, LININGS, WALLS OR DOORS SPECIALLY ADAPTED FOR COMBUSTION CHAMBERS, e.g. FIREBRIDGES; DEVICES FOR DEFLECTING AIR, FLAMES OR COMBUSTION PRODUCTS IN COMBUSTION CHAMBERS; SAFETY ARRANGEMENTS SPECIALLY ADAPTED FOR COMBUSTION APPARATUS; DETAILS OF COMBUSTION CHAMBERS, NOT OTHERWISE PROVIDED FOR
  • F23M20/00—Details of combustion chambers, not otherwise provided for, e.g. means for storing heat from flames
  • F23M20/005—Noise absorbing means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D2203/00—Gaseous fuel burners
  • F23D2203/10—Flame diffusing means
  • F23D2203/101—Flame diffusing means characterised by surface shape
  • F23D2203/1012—Flame diffusing means characterised by surface shape tubular
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D2203/00—Gaseous fuel burners
  • F23D2203/10—Flame diffusing means
  • F23D2203/102—Flame diffusing means using perforated plates
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D2203/00—Gaseous fuel burners
  • F23D2203/10—Flame diffusing means
  • F23D2203/102—Flame diffusing means using perforated plates
  • F23D2203/1023—Flame diffusing means using perforated plates with specific free passage areas
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D2210/00—Noise abatement

Definitions

• the invention relates to a cylindrical premix gas burner, and specifically to such burners with a perforated plate as cylindrical burner deck.
• the cylindrical premix gas burner has a specific inlet disc for the entry of premix of air and combustible gas into the cylindrical premix gas burner. The result is a reduction in thermo-acoustic instabilities of the burner.
• Such burners find use in boilers and in instantaneous water heaters.
• WO201 1/069839 and EP2037175A2 provide examples of such burners. These examples are provided without the use of a second cylindrical element in the burner that would act as distributor of premix gas inside the burner prior to the premix gas flowing through the cylindrical burner deck. The premix gas is burned at the outside of the cylindrical burner deck.
• the cylindrical burners of WO2009/065733 comprise an inlet disc with a multiple of perforations for the supply of premix gas into the chamber enclosed by the cylindrical burner.
• Such perforations can be made easily, with standard punching equipment, punching pellets out of metal plates thereby creating the perforations.
• the cylindrical burners of EP2037175A2 are provided with an inlet having a plurality of through openings or holes.
• the through openings or holes are obtained by partial cutting and folding of portions of the disc to form embossed tongues developing towards the inner part of the tubular body and are alternated to the same openings.
• the primary objective of the invention is to provide cylindrical premix gas burners with a perforated inlet disc and that show reduced thermo-acoustic instabilities than cylindrical premix gas burners that are known in the art.
• a cylindrical premix gas burner is provided.
• the burner can be a fully premixed burner.
• the cylindrical gas burner is comprising a cylindrical burner deck, in the form of a perforated metal plate.
• the perforations in the cylindrical burner deck can be of different shapes and sizes, e.g. circular perforations, slits or slot; which can be arranged according to a certain pattern, over the full cylindrical burner deck, or in different patterns in different sections of the cylindrical burner deck.
• the perforations in the cylindrical burner deck can also by arranged in a random way.
• the cylindrical premix gas burner is delimited by an end cap.
• an inlet disc is provided for the supply of a premix of combustible gas and air into the burner, premix gas which is to be burned on the outside of the cylindrical burner deck after the premix gas has flown through it.
• the inlet disc is comprising a plurality of perforations for premix gas supply into the burner. With perforation is meant that a through hole is present in the inlet disc whereby material is removed from the inlet disc thereby creating the through hole. Such perforations can be made by means of punching equipment, wherein pellets are punched out of the inlet disc, thereby forming the perforations.
• the inlet disc is having a centre point, which is where the (virtual) central axis of the cylindrical premix gas burner crosses the inlet disc.
• the inlet disc is not permeable to premix gas at least within a circle around the centre point with a diameter of at least 8 mm, and more preferably with a diameter of at least 10 mm, even more preferably with a diameter of 14 mm.
• thermo- acoustic instabilities can be avoided in boilers or instantaneous heaters that are equipped with burners according to the inventions, especially at low CO2 operating conditions of the burner.
• the burners of the inventions showed to generate less humming at low CO2 operating conditions.
• the burner will be used in blue flame mode (and not in red flame mode which is useful when heat is transferred via infrared radiation) whereby hot flue gas is generated that will transfer its energy via conductivity and via convection, e.g. to a fluid (e.g. water) in a heat exchanger (e.g. a cast heat exchanger or a plate heat exchanger or a spiral tube heat exchanger).
• a fluid e.g. water
• a heat exchanger e.g. a cast heat exchanger or a plate heat exchanger or a spiral tube heat exchanger.
• the inlet disc is not perforated at least within a circle around the centre point with a diameter of at least 8 mm, and more preferably with a diameter of at least 10 mm, even more preferably with a diameter of 14 mm.
• a disc is provided that can have perforations in the central zone as well, but a plate is fixed on one side, or plates are fixed on both sides of the disc in order to close off locally the perforations of the disc.
• an inlet disc (comprising the disc and the one or more plates) can be provided that is not perforated (and hence not permeable to premix gas) at least within a circle around the centre point with a diameter of at least 8 mm, and more preferably with a diameter of at least 10 mm, even more preferably with a diameter of 14 mm.
• the fixation between the disc and the one or more plates can e.g. be by means of welding.
• the cylindrical premix gas burner is devoid of a diffuser inside the cylindrical perforated burner deck; meaning that the cylindrical gas burner is devoid of a diffuser inside the chamber enclosed by the inlet disc, the cylindrical burner deck and the end cap. It means that gas premix is flowing through the inlet disc, and without no further physical obstacles it is flowing through the perforations of the cylindrical burner deck to be burned on the outside of the cylindrical burner deck.
• the perforated part of the inlet disc (which is the part of the inlet disc that is provided with perforation) is flat, which has as benefit that the perforations can be made more easily.
• the inlet disc is not permeable to premix gas around the centre point of the inlet disc over a zone that is centred at the centre point of the inlet disc.
• That zone has a regular shape.
• regular shape is meant that two lines can be defined on the inlet disc that cross in the centre point which - between the two lines - contain a part of that zone, that when repeating that part around the centre point a number of times (e.g. three times, e.g. four times, e.g. six times), the whole zone of the inlet disc that is not permeable to premix gas is covered and this is centred around the centre point.
• That zone can have a star shape.
• Such an embodiment has been shown to be particularly advantageous in the reduction of humming at low CO2 levels of the burner.
• that zone has a regular polygonal shape. More preferred is when that zone is having a regular hexagonal shape, as the perforations in the inlet disc - around the zone that is not perforated - can, from a manufacturing point of view - be made more easily.
• at least part of the perforations for premix gas supply in the inlet disc are of cylindrical shape, more preferably all perforations are of cylindrical shape.
• the inlet disc comprises at least fifteen perforations, and more preferably at least twenty perforations, and even more preferably at least thirty perforations, for premix gas supply into the burner, the higher number is preferred to reduce acoustic instabilities.
• the perforations of the inlet disc all have the same shape and/or same size and/or same surface area. This facilitates the production of the perforations of the inlet disc and the tooling required for it.
• the perforations of the inlet disc for supply of premix gas have different shapes and/or different sizes and/or different surface areas.
• the inlet disc comprises perforations of different size or different surface area, and when perforations of larger size (or of larger surface area) are located closer to the centre point than perforations of smaller size (or of smaller surface area).
• This embodiment has the benefit that lower NOX (nitrogen oxide) emissions are obtained when using the burner.
• Preferred is when the average distance from the centre point of a smaller perforation is at least 100% higher than the average distance from the centre point of a larger perforation.
• the inlet disc is comprising perforations of at least two different surface areas, with the surface area of a larger perforation at least 50% (and preferably more than 100%, but preferably less than 200%) larger than the surface area of a smaller perforation.
• burners according to this embodiment have shown to have reduced NOX levels, which is beneficial in view of more stringent legislation on emissions of burners.
• each of the perforations of the inlet disc are having a surface area of less than 30 mm 2 , and preferably less than 20 mm 2 , and more preferably less than 13 mm 2 and even more preferably less than 12 mm 2 .
• the cylindrical premix gas burner has along the length of the cylindrical burner deck, circumferential sections of different porosity (of preferably at least 25% of the length of the perforated zone of the cylindrical metallic burner membrane), with at least two sections which have an absolute difference in porosity of more than 3% (e.g. 15% in one zone, 7.5% in another section) and with an average porosity of the cylindrical burner deck of less than 1 1 %.
• porrosity of the burner deck is to be understood, in the light of this invention, as the ratio of the surface of the holes, slots or other perforations divided by the surface of the burner (or the section) over which the perforated part(s) is (are) located.
• thermo-acoustical instabilities could be further reduced, thanks to the synergy between the features of the inlet disc and the feature of the perforations on the cylindrical burner deck. More preferably, the section with higher porosity is located closer to the inlet disc than a section with lower porosity.
• the cylindrical burner deck has
• the burner according to this embodiment of the invention has shown to have even better results in terms of thermo-acoustic instabilities thanks to the synergy of the features of the inlet disc and the perforations on the burner deck.
• the burner deck has a third section, further away from the inlet disc than the perforated section with porosity less than 10%, wherein the third section is having a porosity higher than 12%, preferably between 14 and 16%.
• Such boilers and instantaneous water heaters have less acoustical instabilities compared to when using prior art cylindrical gas premix burners.
• Figure 1 shows an example of a cylindrical premix gas burner according to the invention.
• FIGS 2, 3 and 4 show examples of inlet discs that can advantageously be used in the invention.
• Figure 5 shows an example of a cylindrical premix gas burner according to the invention.
• Figure 6 shows an alternative way to provide an inlet disc that can be used in a cylindrical premix gas burner according to the invention.
• Figure 1 shows an example of a cylindrical premix gas burner 100
• the cylindrical gas burner 100 is comprising a cylindrical burner deck 1 10, in the form of a perforated metal plate.
• the cylindrical gas burner has an internal diameter of 69 mm, but other internal diameters are possible, preferably between 50 and 95 mm.
• the cylindrical premix gas burner 1 10 does not comprise a diffuser within the room enclosed by the cylindrical burner deck 1 10.
• the cylindrical premix gas burner 1 10 is delimited by an end cap 1 18.
• an inlet disc 130 is provided for the supply of a premix of combustible gas and air into the burner 100, premix gas which is to be burned on the outside of the cylindrical burner deck 1 10 after the premix gas has flown through it.
• the inlet disc 130 is comprising a plurality of perforations 140 for premix gas supply into the burner 100.
• all perforations 140 in the inlet disc for supply of premix gas are of the same size, e.g. circular with a diameter of 2.5 mm, or of 3.6 mm.
• perforations of other shape e.g. slits
• Such perforations can be made by punching the inlet disc with appropriate tooling thereby punching out pellets from the inlet disc and making the perforations.
• the inlet disc 130 can be provided with a flange 143 with holes 145 for the connection of the burner, e.g. in a boiler housing.
• the inlet disc 130 is having a centre point, which is where the (virtual) central axis 147 of the cylindrical premix gas burner crosses the inlet disc 130.
• the inlet disc is not permeable to premix gas within a circle 150 around the centre point with a diameter of e.g. 14 mm.
• FIG. 2 shows an example of an inlet disc 130 that can be used in the invention.
• the inlet disc is provided with perforations 141 , 142 of two different dimensions. Larger perforations 141 of e.g. 3.6 mm diameter are located more centrally on the inlet disc 130 compared to smaller perforations 142 of e.g. 2.5 mm diameter.
• the inlet disc 130 is impermeable to gas premix in a star shaped zone 152.
• the star shaped zone includes a circle of at least 8 mm diameter, e.g. of diameter 12 mm.
• the inlet disc 130 can be provided with a flange 143 with holes 145 for the connection of the burner, e.g. in a boiler housing.
• FIG. 3 shows an example of an alternative inlet disc 130 that can be used in the invention.
• the inlet disc is provided with perforations 141 , 142 of two different dimensions. Larger perforations 141 of e.g. 3.6 mm diameter are located more centrally on the inlet disc 130 compared to smaller perforations 142 of e.g. 2.5 mm diameter.
• the inlet disc 130 is impermeable to gas premix in an alternative star shaped zone 154.
• the star shaped zone includes a circle of at least 8 mm diameter, e.g. of diameter 12 mm.
• the inlet disc 130 can be provided with a flange 143 with holes 145 for the connection of the burner, e.g.
• FIG. 4 shows an example of an alternative inlet disc 130 that can be used in the invention.
• the inlet disc is provided with perforations 141 , 142 of two different dimensions. Larger perforations 141 of e.g. 3.6 mm diameter are located more centrally on the inlet disc 130 compared to smaller perforations 142 of e.g. 2.5 mm diameter.
• the inlet disc 130 is impermeable to gas premix in a regular hexagonal shaped zone 156.
• the star shaped zone includes a circle of at least 8 mm diameter, e.g. of diameter 10 mm.
• the inlet disc 130 can be provided with a flange 143 with holes 145 for the connection of the burner, e.g. in a boiler housing.
• FIG. 5 shows an example of a cylindrical premix gas burner 500 of the invention.
• the burner has a length of 92.6 mm and diameter of 70.4 mm.
• the burner deck 510 has a length of 92.6 mm and is perforated over a length of 73.2 mm.
• the perforations in the perforated plate that forms the burner deck 510 are a combination of slits and round holes.
• the thickness of the perforated plate is 0.6 mm, the slits are 4.0 * 0.5 mm, the holes have a diameter of 0.8 mm.
• the perforations are grouped in patterns: the first 1 1 .8 mm of the perforated burner deck length (meaning closest to the inlet disc 520) has a porosity of 15%, thereafter is a zone of 55.6 mm of the burner deck length with a porosity of 7.3% and the last zone with a length of 5.8 mm of the burner deck length having a porosity of 16.5%.
• This pattern is repeated over the burner deck on the circumference of the burner. This provides a burner deck which has an overall porosity of 9.8%.
• the burner does not contain a diffuser inside the cylindrical burner deck.
• the burner comprises an inlet disc 520 according to the invention, e.g. an inlet disc as shown in figures 1 , 2, 3 or 4.
• FIGS. 6A and 6B show an alternative way to provide an inlet disc that can be used in a cylindrical premix gas burner according to the invention.
• the inlet disc 630 is comprising a disc 635, which is comprising
• the disc 635 can have a flange 643 with through holes 645 for the fixation of the inlet disc 630 e.g. to a burner housing.
• An unperforated plate 660 is welded centrally on top of the first plate 635. The dimensions of the imperforated plate 660 are selected to create
• the imperforated plate can e.g. have a circular shape (e.g. of diameter 14 mm), or another shape, e.g. a star shape, or a regular polygonal shape (e.g. a regular hexagonal shape).
• Figure 6B shows the cross section of inlet disc 630 along line ⁇ - ⁇ .
• a first burner (burner not according to the invention) that was tested had an inlet disc with a multiple of perforations in the inlet disc, including perforations at the centre of the inlet disc.
• the burner had a humming sound, especially at low CO2 operating conditions.
• This burner was compared with a burner according to the invention with an inlet disc as shown in figure 4.
• the inlet disc was having small perforations (of 2.5 mm diameter) and bigger perforations (of 3.6 mm).
• perforations are absent around the central point of the inlet disc (seven of the "expected" perforations are missing).
• the burner according to the invention was not producing a humming sound, even not at low CO2 operating conditions.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Gas Burners (AREA)

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• 2013
  • 2013-02-04 EP EP13702475.8A patent/EP2815181A1/de not_active Withdrawn
  • 2013-02-04 WO PCT/EP2013/052122 patent/WO2013120716A1/en active Application Filing

Non-Patent Citations (1)

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