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
  • F23D14/46—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
  • 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
  • F23D14/48—Nozzles
  • F23D14/58—Nozzles characterised by the shape or arrangement of the outlet or outlets from the nozzle, e.g. of annular configuration
• • 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
  • F23D2210/00—Noise abatement
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D2900/00—Special features of, or arrangements for burners using fluid fuels or solid fuels suspended in a carrier gas
  • F23D2900/00003—Fuel or fuel-air mixtures flow distribution devices upstream of the outlet

Definitions

• the present invention relates to a gas burner for premixed combustion, in accordance with the introduction to the main claim.
• such a gas burner for a boiler
• This burner receives a gas-air mixture, obtained externally to it in known manner and fed internally to one end of it through known pipes; this mixture is activated by an ignition electrode located in a suitable position relative to the burner such as to generate a flame on the outside of the burner, or on the other end from that at which said mixture arrives.
• the burner is usually positioned in a combustion chamber from which the flue gases generated within it are removed through an appropriate exit and directed to discharge.
• Such a premixed combustion burner is known to comprise a first component known commonly as a "distributor" and a second component defining the (outer) shell of the burner.
• the distributor receives the air-gas mixture and presents a perforated distribution surface through which this mixture passes.
• the distributor is positioned in proximity to the burner shell formed by a perforated "burning" surface from which the air-gas mixture emerges and on which the flame is generated by activation of the ignition electrode. If the burner is of cylindrical form, for example, these components are cylindrical and coaxial, the distributor being contained within the burner shell and receiving said mixture internally thereto.
• the burning surface is known to consist of a perforated surface (with holes or slits of known dimensions), for example of steel or of a steel fibre mesh or other suitable material.
• the distribution surface consists normally of a surface, for example of steel, suitably perforated such as to adequately distribute the mixture over the entire burning surface and generate the flame over its total area so as to equally distribute the burner thermal load uniformly over this latter (W/cm 2 of burning surface).
• a solution is also known in which the burning surface indeed generates a thermal load distributed over its entire area (with the flame present on the entire surface), although in a particular point or zone of this latter this load varies relative to the average load (normally that zone within the interior of the flame sensing electrode); the reason for this is to obtain in these points or zones a higher flame signal which enables better flame sensing and/or better combustion control compared with known solutions.
• this solution limits the working power range and does not allow optimal burner control as the flame signal by which this control is carried out varies substantially, for example on varying the family gas type used in the burner.
• a substantial noise can be generated (in the form of a "bang") during ignition.
• a substantial noise can be generated (in the form of a "bang") during ignition.
• correlation between the flame signal and combustion on the basis of the power range in which the burner operates is not optimal.
• noises can also be generated during combustion under normal working conditions and/or as climatic conditions vary.
• An object of the present invention is o provide an improved burner by which the drawbacks of known burners are overcome.
• a particular object of the invention is to provide a burner the thermal load of which is "tuned" on the basis of the form and volumes of the combustion chamber.
• Another object is to provide a burner of the stated type the surface temperatures of which are on the average more homogeneous.
• a further object is to provide a burner with lower CO and nitrogen oxide (NOx) emissions than known solutions.
• Another object is to provide a burner which is of low noise (when in application, i.e. during use) in comparison with known burners, and a burner which enables better combustion control.
• Figure 1 is an exploded perspective view of a burner according to the invention
• Figure 2 is a side view of the burner of Figure 1 ;
• Figure 3 is a section on the line 3-3 of Figure 2;
• Figure 4 is a section on the line 4-4 of Figure 2;
• Figure 5 is a section on the line 5-5 of Figure 2.
• Figure 6 is a schematic cross-section through a burner of the invention within a boiler combustion chamber.
• a burner according to the invention is indicated overall by 100 and comprises a first component defined by a distributor 1 for a gas-air mixture (obtained before being fed through a known conduit, not shown, to the distributor), and a second component (close to but separated from the first 1 ) defined by the burner outer shell 2.
• This distributor 1 and shell 2 are of tubular cylindrical form in the example shown in the figures, but could also be of flat or other form.
• the distributor 1 is internal and coaxial to the shell 2. End closure members 17, of which one is flanged, close the ends of the burner 100.
• the distributor 1 presents a distribution surface 3 which is partially perforated, i.e. in which zones 4 (central in the figures) and 4a (lateral in the figures) are included provided with through holes 5 plus zones 6 which are completely smooth and solid, i.e. not perforated.
• the holes 5 connect a space or interspace 7 present between the distributor 1 and the shell 2 and facing an external or outer side 10 of the distributor to an internal part 1 1 of this latter (i.e. to a compartment facing the inner side 13 of the distributor opposing the outer side 10).
• the mixture which reaches the inner part 11 can be transferred to the interspace 7 through the holes 5. Because of the disuniform position of these holes in the surface 3, this transfer takes place in differential manner within the interspace 7, with different mixture quantities reaching the burner shell 2.
• This latter comprises a burning surface 15 having an inner side 16 facing the interspace 7 and an outer side 18 on which the flame forms (obtained by "igniting" the mixture by means of a known ignition electrode, not shown).
• the burning surface 15 presents a plurality of through slits and holes 20 which connect the interspace 7 to the outer side 18 of the shell 2 and enable the mixture to pass onto this latter to form the flame.
• These slits and holes 20 define a flame generation zone 21 which is localized in the burning surface 15 and is only partially superimposed on the zone 4 of the distributor 1.
• This burning surface 20 lies to the side of and/or alternates (as in the figures) with zones 22 without holes and by which no flame is generated.
• the burner 100 enables a deliberately nonuniform thermal load to be generated in which there is a disuniform outflow of mixture onto the burning surface 15 and hence disuniform flame generation on it.
• the burner thermal load is greater where the zones 4 and 4a of the distributor face each other in each flame generation zone 21 , whereas it is less (than the overall average load) where these zones are not mutually superimposed and/or involve a mixture quantity distributed only by zones (such as the lateral zones 4a of the example of the figures) of the distributor 3 facing the zones 22 of the burner shell 2.
• the thermal load modification and disuniformity can be further highlighted and achieved, not only by eliminating holes from each surface portion of the distributor, but also by modifying the diameter and pitch between the distributor holes 5 and/or the position and size of the slits and holes in the burning surface 20 or the mutual arrangement between the distributor holes 5 and the holes of the burner shell 2, hence in this manner modifying the distribution of the mixture quantity leaving the surfaces 3 and 15.
• the thermal load within a usual combustion chamber 50 in which the burner 100 is positioned can be modified by disposing this latter in an eccentric position contrary to that usually done where the burner 100, as in Figure 6, is positioned along the longitudinal central axis of that chamber.
• the thermal load of the burner 100 can be adapted on the basis of its own geometry, on that of the combustion chamber 50 and on the evacuation path for the off-gases from it (via a discharge 60). This enables various advantages to be obtained.
• a more uniformly distributed cooling of the burner 100 throughout the burning surface 15 can be achieved by increasing the thermal load in the normally cooler zones (for equal working power) and decreasing it in the normally hotter zones, again for equal conditions.
• This enables surface temperatures to be achieved which are on the average more homogeneous independently of the fact that a particular surface portion is grazed by greater heat flows than other portions which are adjacent or positioned in front of the off-gas discharge.
• the noise can be improved (by decreasing it) during burner ignition and flame propagation.
• zones of the burner shell 2 exist generating variable thermal loads, it is possible to locate a usual flame sensing electrode (or equivalent element) in a suitable zone of the burner (for example positioned such as to pass through zones of different thermal load) in a zone such as to improve correlation between the sensed flame signal and combustion at different working powers and with varying family gas type, for example in changing from 2nd family gas (methane) to 3rd family gas (LPG).
• a flame signal is obtained which is a function of the power and combustion, this signal normally having different dynamics between the two families.
• these signals for the two gas families approach each other to such a point that, even if there is a setting error for the gas type used (for example, the burner is set to operate on methane, but is fed with LPG) it remains in an environment or range of safe operation.
• This enables burners with relative control systems to be constructed which can operate with gases of different families, without having to proceed to modify internal components of the application (for example the boiler).
• By developing specific functions in the control algorithm for these systems it also enables identification of the gas family with which the burner is fed, so enabling the working parameters of this latter to be semi-automatically or automatically adapted to the gas family sensed at the burner entry.
• One of these functions can be for example that of verifying, in particular stages of operation, the dynamics of the flame signal (substantially different from one gas family to another) as the working parameter varies, for example as the gas flow varies for fixed air flow or, vice versa, as the air volume varies for fixed gas flow.
• the correlation between the flame signal and the working lambda coefficient i.e. the coefficient which defines the ratio between the air and gas, means that if the gas family changes, the invention is able to maintain CO values below the legal limits and CO2 values close to the optimal working value, so guaranteeing operational safety of the application.

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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)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Family Cites Families (12)

• 2011
  • 2011-03-11 IT IT000390A patent/ITMI20110390A1/it unknown
• 2012
  • 2012-03-06 EP EP12711227.4A patent/EP2683985A1/en not_active Withdrawn
  • 2012-03-06 WO PCT/IB2012/000469 patent/WO2012123805A1/en active Application Filing
  • 2012-03-06 US US14/004,325 patent/US20140011142A1/en not_active Abandoned
  • 2012-03-06 CN CN201280012119XA patent/CN103443544A/zh active Pending

Non-Patent Citations (1)

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