Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
  • F23C9/00—Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber
  • F23C9/006—Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber the recirculation taking place in the combustion chamber
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D11/00—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space
  • F23D11/36—Details, e.g. burner cooling means, noise reduction means
  • F23D11/40—Mixing tubes or chambers; Burner heads
  • F23D11/402—Mixing chambers downstream of the nozzle
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D11/00—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space
  • F23D11/36—Details, e.g. burner cooling means, noise reduction means
  • F23D11/40—Mixing tubes or chambers; Burner heads
  • F23D11/404—Flame tubes

Definitions

• the invention relates to a burner with fuel gas recirculation for flowable fuels (heating oil, gas) according to the preamble of claim 1.
• the mixing tube is a cylindrical tube, the diameter of which is considerably smaller than the diameter of the flame tube, which results in a wide annular gap.
• the openings for the transfer of fuel gases into the mixing tube are at a distance from the end of the mixing tube facing the air supply tube
• the spray cone angle of the fuel nozzle must be relatively small if wetting of the wall of the cylindrical mixing tube is to be avoided. They fly at a small spray cone angle
• Fuel droplets in a direction that is only a small angle with the direction of the incoming combustion air are not optimal. If a larger pointed cone angle is selected, the fuel nozzle must be arranged at a relatively large distance from the end of the mixing tube on the combustion air side in order to obtain extensive mixing with the combustion air before the fuel enters the Mixing zone, ie in the area of the mixing tube in the flow direction behind the fuel gas supply openings. This in turn means that the core of the fuel steel cannot reach far into the mixing zone.
• the invention has for its object to provide a burner of the generic type with which an improved
• the mixing tube is adapted to the shape of the spray cone of the fuel due to its design as an expanding funnel, so that practically no wall wetting can occur even when a large spray cone angle is selected.
• the fuel droplets fly in the peripheral zone of the spray cone in a direction which includes a relatively large angle with the direction in which the combustion air flows into the mixing tube, so that a very intensive mixing with the combustion air takes place.
• This also enables the fuel nozzle to be arranged near the end of the mixing tube on the combustion air side, so that the injection jet extends far into the
• Flame tube the inlet cross-section of the annular space flowed through by the returned fuel gases, despite its relatively small width, is large enough to be able to recycle a sufficient amount of fuel gas.
• FIG. 1 shows a longitudinal section of a recirculation burner according to a first exemplary embodiment
• Fig. 2 shows a cross section of the mixing tube of Fig. 1 in the
• Fig. 3 is a longitudinal section of a recirculation burner according to a second embodiment
• Fig. 4 shows a longitudinal section of a recirculation burner according to a third embodiment.
• the burner according to FIG. 1 has a feed pipe 1 for the combustion air connected to a blower, not shown, in which an air funnel 2 narrowing in the flow direction is arranged, which is provided with a central holder 4 for a fuel nozzle 5.
• a funnel-shaped mixing tube 6 a Connected to the air funnel 2 is a funnel-shaped mixing tube 6 a, which projects into a flame tube 7, which is inserted with its left end in the drawing in a slotted end section 8 of the air supply pipe 1 with the interposition of a seal 9 and by tightening one the end section 8 together - The screw 10 is held tight.
• the inside wall of the burner according to FIG. 1 has a feed pipe 1 for the combustion air connected to a blower, not shown, in which an air funnel 2 narrowing in the flow direction is arranged, which is provided with a central holder 4 for a fuel nozzle 5.
• Flame tube 7 runs in the area of the mixing tube 6 parallel to the wall of the mixing tube 6 and at a short distance from it, whereby a relatively narrow conical annular gap 11 is formed, which is connected to the interior thereof by bores 12 in the wall of the mixing rod 6.
• the annular space 11 is open to the interior of the flame tube 7, so that fuel gases from the flame tube 7 can pass through the bores 12 into the mixing tube 6.
• This return of the hot fuel gases is achieved by the injector effect of the combustion air flowing into the mixing tube 6 at high speed.
• the bores 12 as can be seen in FIG.
• the returned fuel gases flow through the narrow annular space 11 and along the wall at a relatively high speed of the mixing tube 6, whereby this is heated up strongly.
• this heating is so strong that the mixing tube 6 becomes red-hot even in the case of a ceramic version, as a result of which a very intensive preparation of the mixture of recirculated fuel gases, combustion air and fuel flowing through the mixing chamber takes place.
• the cone angle of the funnel-shaped mixing tube 6 preferably corresponds to the angle of spray of the fuel nozzle 5, so that wetting of the wall of the mixing chamber 6, which could lead to soot formation, is avoided.
• the flame tube 7, like the mixing tube 6, is made of a highly heat-resistant material, preferably ceramic. Radial or inclined ribs 6a can be provided for centering the mixing tube 6 in the flame tube 7.
• FIG. 3 differs from this embodiment essentially only in that the mixing tube 6 is at a short distance from End of the air funnel 2 or from the end wall 13 of the flame tube 7 'is arranged, whereby an annular gap 14 is formed through which the hot fuel gases can flow from the annular space 11' into the mixing tube 6 '.
• the provision of the annular gap 10 instead of the bores 12 of FIG. 1 simplifies the production, since no drilling of holes is required, and the inlet cross section for the fuel gases to be returned is increased.
• FIG. 4 in which again the same or similar parts are designated with the same reference numerals as in FIG.
• the air funnel 2 from FIGS. 1 and 2 is omitted.
• the combustion air enters directly from the air supply pipe 1 "through a central opening 15 in the end wall 13" of the flame pipe 7 "into the mixing pipe 6", and the mixing pipe 6 "is at a distance from the end wall as in the exemplary embodiment according to FIG. 2 13 ", so that an annular gap 14" is again formed, through which the returned fuel gases can flow from the annular space 11 "into the mixing tube 6".
• the mixing tube 6 is provided with a cylindrical extension 16, the outside diameter of which is slight is smaller than the inner diameter of the flame tube 7 ", so that the fuel gases can flow through the annular gap 17 formed in this way into the annular space 11".
• the mixing tube 6 " is connected to the flame tube 7" and centered in the flame tube 7 "by means of several, for example three, radially extending pins 18, which are distributed evenly over the circumference and extend through corresponding holes 19 in the cylindrical extension 16. This considerably facilitates the attachment of the mixing tube 6 "in the flame tube 7".
• the cylindrical surface 16 increases the heating surface for the mixture flowing through the mixing tube 6 ".
• the fuel gases are removed from the flame tube 7" from a zone of higher pressure than in the previous examples, as a result of which the pressure gradient to the overflow gap 14 " is increased, which in turn means a higher flow rate and thus a greater heat transfer to the wall of the mixing tube 6 " and an increase in the amount of fuel gases returned.
• the burners shown are attached in the usual way to the boiler, not shown, so that the flame tube protrudes into the combustion chamber of the boiler. It is known that the return of flue gas can reduce the formation of nitrogen oxides.
• a flue gas recirculation can also be implemented in a simple manner in the burners according to the invention by providing, as shown in FIG. 4, the wall of the flame tube 7 "with openings 20 through which the smoke gas can enter the flame tube 7". These openings 20 are at such an axial distance from the end of the
• the openings can be arranged obliquely in the flow direction of the fuel gases in the flame tube 7 ′′, so that the flue gases flow away from the annular space 11 ′′ or the annular gap 17 due to this arrangement of the openings 20.
• breakthroughs 20 can also according to the exemplary embodiments. 1 and 2 are provided.
• the flame tube 7 forms a unit with the mixing tube 6, which is connected to the air supply tube 1 by clamping by means of the clamping screw 10. This makes maintenance of the burner extremely simple, since, for example, it is only necessary to replace the fuel nozzle 5 the screw 10 needs to be loosened, whereupon the unit consisting of the flame tube 7 and the mixing tube 6 can be removed and the fuel nozzle 5 is exposed.

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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)

Family

ID=6387915

Family Applications (1)

Country Status (3)

Families Citing this family (7)

Family Cites Families (12)

• 1989
  • 1989-08-25 DE DE3928214A patent/DE3928214A1/de active Granted
• 1990
  • 1990-02-23 EP EP90904336A patent/EP0515365A1/de not_active Withdrawn
  • 1990-02-23 WO PCT/EP1990/000313 patent/WO1991013291A1/de not_active Application Discontinuation

Non-Patent Citations (1)

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