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
  • F23D14/70—Baffles or like flow-disturbing devices
• • 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
  • F23D2203/105—Porous plates
  • F23D2203/1055—Porous plates with a specific void range

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 an inlet disc for the entry of premix of air and combustible gas into the cylindrical premix gas 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.
• EP2037175A2 are provided with an inlet disc with a multiple of
• the primary objective of the invention is to provide a cylindrical premix gas burner that results in lower emission values, especially of NOX (nitrogen oxides) than the cylindrical premix gas burners that are known in the art.
• NOX nitrogen oxides
• the invention discloses a cylindrical premix gas burner which is
• the cylindrical burner deck is comprising a perforated metal plate.
• the cylindrical burner deck is a perforated metal plate, without any other layer on either side of the perforated metal plate.
• the cylindrical premix gas burner is delimited by an end cap. At the opposite side of the end cap, an inlet disc with perforations is provided for the supply of a premix of combustible gas and air into the burner. The premix gas will be burnt on the outside of the cylindrical burner deck after the premix gas has flown through it.
• the inlet disc is comprising
• the central zone is the zone on the inlet disc around the centre point of the inlet disc.
• the centre point is where the central axis of the cylindrical premix gas burner crosses the inlet disc.
• the porosity of the inlet disc is higher in the central zone than in the peripheral zone.
• the average surface area of the perforations in the central zone of the inlet disc is less than 20 mm 2 , and preferably less than 13 mm 2 , and more preferably less than 10 mm 2 .
• the cylindrical burner of the invention e.g. has an internal diameter of more than 50 mm.
• the porosity in the central zone is between 25 and 50% of the surface area of the central zone, more preferably between 30 and 40%.
• the porosity in the peripheral zone is 15 to 30%, more preferred between 17 and 25% of the surface area of the peripheral zone.
• the average porosity of the inlet disc (calculated for the full inner diameter of the cylindrical premix gas burner) is between 20% and 50%, more preferably between 25% and 40%.
• the cylindrical premix gas burner is devoid of a diffuser inside the cylindrical perforated burner deck. It means that premix gas 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 burnt on the outside of the cylindrical burner deck.
• the section of the inlet disc that is covered by the cylindrical burner deck is flat, which makes that perforations in the inlet disc for the supply of premix gas are easy and cheap to produce.
• the porosity of the inlet disc is higher in the central zone with a diameter of 20% of the inner diameter of the cylindrical premix gas burner, compared to the porosity in a peripheral zone between 35% and 75% of the inner diameter of the cylindrical gas burner.
• the central zone with a diameter of 20% of the inner diameter of the cylindrical premix gas burner is meant the zone within a circle around the centre point of the inlet disc that is having a diameter of 20% of the inner diameter of the cylindrical premix gas burner.
• the preferred porosity in that central zone is between 25 and 50% of the surface area of that central zone, more preferably between 30 and 40%.
• the porosity in that peripheral zone is 15 to 30%, more preferred between 17 and 25% of its surface area.
• the central zone comprises at least seven perforations.
• the inlet disc is not permeable to premix gas in the zone between 80% and 100% of the inner diameter of the cylindrical premix gas burner.
• the circles with these diameters are considered around the centre point of the inlet disc.
• the benefit of this embodiment is that further reduced NOX values are obtained in burners according to this embodiment.
• central zone with a diameter of 20% of the inner diameter of the cylindrical premix gas burner is in absolute terms at least 8 % higher (and preferably at least 10 %, more preferably at least 15 % higher) than the porosity of the inlet disc in the zone between 35% and 75% of the inner diameter of the cylindrical premix gas.
• each of the perforations in the zone between 40% and 75% of the inner diameter of the cylindrical gas burner are of the same size.
• each of the perforations in the central zone with a diameter of 20% of the inner diameter of the cylindrical premix gas burner have a surface area of less than 20 mm 2 , and preferably less than 13 mm 2 and more preferably less than 10 mm 2 .
• perforations in the central zone is between 1 .22 and 9 times, more preferably between 1 .22 and 2.5 times the average surface area of the perforations in the peripheral zone.
• Preferred are circular perforations.
• the perforations (for premix gas supply) in the central zone with a diameter of 20% of the inner diameter of the cylindrical premix gas burner are all of the same shape and size.
• the perforations in the inlet disc are all of the same size; and the density of the perforations in the central zone with a diameter of 20% of the inner diameter of the cylindrical premix gas burner is on average higher (and preferably at least 10% in relative terms, more preferably at least 50 higher in relative terms) than the average density of the perforations in the zone between 20% and 75% of the inner diameter of the cylindrical premix gas burner.
• the density of the perforations is meant the number of perforations relative to the surface area.
• the average porosity of the cylindrical burner deck of less than 1 1 %.
• the cylindrical burner deck can have circumferential zones of different porosity (of preferably at least 25% of the length of the perforated zone of the cylindrical metallic burner membrane), with an absolute difference in porosity of more than 3%.
• circumferential zone is meant a cylindrical part of the cylindrical burner deck; and the porosity of the circumferential zone is the total perforated area of that zone relative to the total area of the circumferential zone.
• the cylindrical burner deck has
• a zone with perforations, the porosity of the zone is less than 10%, preferably between 7 and 8.5%.
• the average porosity of the cylindrical burner deck is less than 1 1 %.
• Burners according to such embodiments of the invention have shown to have even better results in NOX (lower NOX) thanks to the synergy between the features of the inlet disc and the features of the metallic burner membrane. Surprisingly, such burners showed to generate less noise, even than the burners of WO201 1/069839, due to the synergetic effect of the perforations in the inlet disk and the perforations in 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%.
• a burner according to these embodiment of the invention has shown to have even better results in NOX (lower NOX) thanks to the synergy between the features of the inlet disc and the features of the metallic burner membrane. Surprisingly, such burners showed to generate less noise, even than the burners of
• the cylindrical premix gas burner according to the invention can be any cylindrical premix gas burner according to the invention.
• Figure 1 shows an example of a cylindrical premix gas burner according to the invention.
• FIG. 1 shows a section of an example of a cylindrical premix gas burner 100 according to the invention.
• the burner 100 has a perforated plate that forms the cylindrical burner deck 1 10 (perforations in the cylindrical burner deck 1 10 are only partly shown in the figure), with inner diameter 69.2 mm.
• the burner 100 is delimited by an end cap 1 15.
• an inlet disc 120 is present, that can have a flange 125 with holes 127 for connection of the burner e.g. in a burner housing.
• the inlet disc 120 can be connected to the cylindrical burner deck 1 10 by means of welding.
• the inlet disc 120 has perforations 130, 140 in order for premix gas to enter the burner 100. The premix gas, once flown through the perforations 130, 140 of the inlet disc 120, will flow through the
• the inlet disc 120 is having large perforations 130 in the central zone (e.g. of diameter 3.60 mm) and small perforations 140 outside the central zone (e.g. of diameter 2.50 mm).
• the distance between the center points of adjacent perforations is constant, e.g. 5 mm.
• a total of 37 large perforations 130 (of 3.6 mm diameter) are located in the central zone; and a total of 72 small perforations 140 (of 2.5 mm diameter) around the central zone.
• a zone 150 is present without any perforations, which is the zone outside a diameter of 52.5 mm (which is in this example outside 76 % of the internal diameter of the cylindrical premix gas burner 1 10).
• the burner of the example has a length of 92.6 mm.
• the cylindrical burner deck 1 10 has a length of 92.6 mm and the length L over which it is perforated is 73.2 mm.
• the perforation pattern in the perforated plate that forms the burner deck 1 10 is a combination of slits and round holes.
• the thickness of the perforated plate is 0.6 mm, the slits being 4.0 * 0.5 mm, the holes having a diameter of 0.8 mm.
• the first 1 1 .8 mm of the perforated burner deck length 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 with an overall porosity of 9.8%.

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

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Citations (4)

• 2013
  • 2013-02-04 EP EP13702067.3A patent/EP2815179A1/fr not_active Withdrawn
  • 2013-02-04 WO PCT/EP2013/052121 patent/WO2013120715A1/fr not_active Ceased

Patent Citations (4)

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