Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D17/00—Burners for combustion conjointly or alternatively of gaseous or liquid or pulverulent fuel
  • F23D17/002—Burners for combustion conjointly or alternatively of gaseous or liquid or pulverulent fuel gaseous or liquid fuel
• • 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 
  • F23C7/00—Combustion apparatus characterised by arrangements for air supply
  • F23C7/002—Combustion apparatus characterised by arrangements for air supply the air being submitted to a rotary or spinning motion
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23R—GENERATING COMBUSTION PRODUCTS OF HIGH PRESSURE OR HIGH VELOCITY, e.g. GAS-TURBINE COMBUSTION CHAMBERS
  • F23R3/00—Continuous combustion chambers using liquid or gaseous fuel
  • F23R3/28—Continuous combustion chambers using liquid or gaseous fuel characterised by the fuel supply
  • F23R3/286—Continuous combustion chambers using liquid or gaseous fuel characterised by the fuel supply having fuel-air premixing devices

Definitions

• the present invention relates to a device and a method for injecting a liquid fuel into an air flow making it possible to produce a homogeneous fuel / air mixture in a combustion chamber.
• the invention finds a use in particular in the field of terrestrial gas turbines, by promoting, during the operation of said turbine, obtaining a high energy yield associated with a low production of pollutants.
• the pollutants generally produced by gas turbines during the combustion of hydrocarbons are, as previously mentioned, nitrogen oxides but also carbon monoxide and unburnt hydrocarbons. It is also well known that the oxidation of molecular nitrogen to thermal NO x within the combustion chambers of turbines strongly depends on the maximum temperature of the hot gases in the reactive zone.
• nitrogen oxides can thus be represented by an increasing exponential function of the temperature. It therefore follows from the above that it is possible to limit the formation of nitrogen oxides by avoiding the temperature peaks of the gases within the combustion chamber.
• Another solution consists in practicing staged combustion, with a rich stage and a lean stage, the transition from one to the other taking place very quickly.
• the temperature peaks, which generate nitrogen oxides NOx are reduced, and the rich zone is also used to limit their formation, but this solution leads to a significant production of unburnt hydrocarbons.
• a third solution for jointly controlling the temperature and the emission of pollutants consists, before combustion, of mixing the air and the fuel in the form of a lean mixture, in order to obtain a fuel / air richness of between 0.3 and 1, preferably between 0.5 and 0.8.
• the mass of air present in excess in the reaction zone thus absorbs part of the heat generated by the oxidation reaction of the fuel and reduces the temperature to which the products of the reaction are subjected.
• the need for cooling air to adjust the temperature at the inlet of the expansion turbine is much less. This process thus effectively limits the production of nitrogen oxides without significantly increasing the emission level of other pollutants (hydrocarbons, carbon monoxide, etc.).
• the main problem posed by a lean mixture operation is that the premix must be sufficiently homogeneous and uniform to achieve the low levels of pollutant emissions sought.
• the premix must be sufficiently homogeneous and uniform to achieve the low levels of pollutant emissions sought.
• US patent 6,094,916 proposes for example a device in which the air / fuel mixture is carried out under pressure thanks to the presence of a fixed device with radial blades generating a rotational movement of the flow of fluids. Between each blade of the device is axially disposed a fuel injection tube. Fuel injection is performed through orifices made in the tubes with an opening angle of 60 ° relative to a radial direction of said device.
• the subject of the present invention is a device making it possible to obtain a homogeneous lean mixture of fuel and air before combustion.
• a device for injecting a liquid fuel into a pressurized air flow comprising a hollow cylindrical body of longitudinal axis delimiting a central volume of substantially cylindrical shape, veins substantially radial with respect to the longitudinal axis of the body and arranged at the periphery of said body for the passage of said flow, and axial fuel injection tubes, disposed inside said veins and connected to at least one fuel inlet by at least one feed point, is characterized in that said tubes are pierced with openings open on the central volume of said body and oriented substantially in the direction of flow flow in the fluid veins.
• the median axis of the veins can form an angle between 20 ° and 60 ° with the radius of the cylindrical body.
• the fluid streams can have a three-dimensional shape calculated to minimize the pressure losses caused during the crossing of the fluid streams by the flow of air under pressure.
• the orifices can be distributed linearly in the axial direction of the fuel injection tubes.
• the fuel injection tubes can have a variable internal cross section as a function of the distance from the fuel supply point of said tube.
• the device may further comprise axial tubes for injecting a gaseous fuel, said tubes being pierced with openings open on said central cylindrical volume and oriented substantially perpendicular to the direction of flow flow in the veins fluids.
• the gaseous fuel injection tubes can be placed, relative to the direction of movement of the pressurized air flow in the fluid streams, upstream of the liquid fuel injection tubes.
• a method of injecting a liquid fuel into a pressurized air flow is characterized in that the following steps are carried out: - pressurized air is brought into a volume upstream d '' at least one combustion zone, a swirling movement of air is generated in said volume by passing the pressurized air flow through a plurality of passages arranged at the periphery of said volume,
• air can be injected into said volume so that its speed varies from approximately 10 m / s to approximately 200 m / s.
• a gaseous fuel can be injected, as a substitute, substantially perpendicularly to the direction of flow of the pressurized air flow.
• Water can be injected in liquid form or in vapor form to replace the fuel.
• FIG. 1 shows a partial sectional view of an injection device according to the invention
• FIG. 2 is a cross-sectional view along line 2-2 of Figure 1;
• FIG. 3A is a local view on a larger scale showing a detail of the device according to the invention.
• FIG. 3B is a sectional view along line 3-3 of Figure 3A;
• - Figure 4 shows a longitudinal sectional view of a possible embodiment of the liquid fuel injection tubes
• upstream and downstream must be associated with the reading of this description in the sense of air circulation in the present device.
• FIG. 1 shows a cross section of a fuel injection and air introduction device 1 and leading to a combustion chamber 2 of a pilot stage or of a main stage of a gas turbine, for example.
• This device with a longitudinal axis YY ′, comprises a liquid fuel inlet tube 3 bringing said fuel to a distribution pipe or manifold 4 of substantially annular shape.
• the hollow body 10 delimits a central zone 11 whose cross section is illustrated in FIG. 2.
• a swirling movement of the air caused by its passage between the vanes 6 allows better stabilization of the combustion by promoting the recirculation of the combustion gases in the space 11 and in the combustion chamber 2.
• the tubes 5 have, over their entire length, orifices 9 open substantially in the direction of air flow in veins 12 and allowing the injection of the liquid fuel in a substantially radial manner between the said blades as well as the mixing of this fuel with the air 7 which arrives, for example, under pressure from the compressor of the turbine (not shown).
• the hollow body 10 is made integral with a fixed part 8 of the device by a known technique.
• Figure 2 shows schematically a cross section of the cylindrical body 10 shown in Figure 1.
• the pressurized air passes through the hollow cylindrical body 10 by the fluid veins 12 delimited by the blades 6.
• the median axis XX 'of the veins 12 forms a angle ⁇ with the radius R between the center of the body 10 and the center of the tube 5.
• the angle ⁇ will be chosen by a person skilled in the art so that the vortex movement in the central zone 11 optimizes the recirculation of the gases of combustion.
• the angle ⁇ will thus generally be between 20 and 60 °.
• a liquid fuel injection tube 5 is placed in each vein 12.
• twelve fluid veins 12 for the passage of air under pressure 7 delimited by twelve blades 6 between which are inserted twelve fuel injection tubes 5.
• FIGS. 3A and 3B respectively show a transverse and longitudinal section of a fluid stream 12 and of the tube 5 present within it.
• the pressurized air 7 passes through the fluid streams 12 along the arrows 17 and is mixed within them with the fuel arriving from an injection point 16 and leaving the orifices 9 in a direction illustrated by the arrows 18.
• the arrows 17 and 18 are collinear in FIGS. 3A and 3B, that is to say that said tubes 5 are pierced with openings open on the central volume of the hollow cylindrical body substantially in the direction of flow of the in the fluid veins.
• This configuration has the advantage in the context of a liquid injection of limiting the formation of coke on the walls 19 of the blades and improving in the fluid streams 12, on the one hand, the mixture between the air and the fuel. and, on the other hand, spraying said fuel downstream of the tubes 5 according to the principles previously described.
• the turbulence zone in the wake of the tube 5 generated by the flow of air 7 at high speed strongly promotes the atomization of the liquid fuel and contributes to improving the homogeneity of the air mixture. / fuel in said area.
• the air flow speed should be of the order of a few tens of m / s, preferably of the order of about 100 m / s while the speed of the fuel had to be as low as possible (of the order of 0.1 m / s to 10 m / s and preferably between about 0.5 m / s and 2 m / s) to promote said spraying and said mixture.
• the cross section of the fluid veins illustrated by the arrows 14 and 15, has a significant narrowing from upstream to downstream so as to increase the speed of the air in it and therefore the turbulence of the 'flow.
• This arrangement advantageously makes it possible to further improve the air / fuel mixture and the atomization of the fuel in the fluid streams 12.
• the cross section of the streams 12 may be rectangular or of another form known to those skilled in the art. so as to optimize the pressure drop caused by crossing the device.
• it can be fitted with a shutter system to adjust the air flow of the floor combustion depending on the load of the turbine, which facilitates operations in reduced steps.
• the swirling movement of the fluids in the central space 11 generated by the passage of the veins 12 of the body 10 also allows recirculation of the hot combustion products also favorable to stabilization of said combustion whatever the operating speed of the combustion chamber.
• FIG. 4 illustrates a possible embodiment of a tube 5 for injecting liquid fuel according to the invention.
• This tube has an evolving section 401 which is a function of the distance to the injection point 16 of the fuel in said tube.
• the tube thus comprises two separate parts: a hollow part 403 ensuring the passage of the fuel to the injection orifices 9 and a solid part 404 produced according to any technique known to those skilled in the art so that it limits gradually the fuel passage section in said tube from the vicinity of its injection point 16 to its free end.
• This arrangement makes it possible to maintain, in a simple and economical manner, a substantially identical flow of fuel for each of the orifices 9.
• FIGS. 5A and 5B respectively represent a cross section and a longitudinal section of a fluid stream 12 and of an injection tube 505 of gaseous fuel present within it.
• the injection orifices 509 are oriented perpendicular to the mean direction of the flow of air in the fluid veins.
• the speed of the mixing will be, in this embodiment, all the more effective the higher the ratio between the speeds of the gaseous fuel and the air.
• FIGS. 3A, 3B and 5A, 5B can be combined to allow a supply and a mode of operation in liquid-gas dual-fueling of the combustion chamber.
• the supply of gaseous fuel to the gaseous fuel injection tubes may be carried out by a second distribution pipe of substantially annular shape substantially identical to that shown in relation to FIG. 1.
• Figure 6 shows schematically a cross section of a cylindrical body 600, identical to that described in connection with Figure 2 and associated with an injection device allowing operation in liquid-gas bicarburation.
• This dual-fueling is carried out by combining, in the same device, tubes for injecting liquid fuel and tubes for injecting gaseous fuel as described above in relation to FIGS. 3A, 3B and 5A, 5B.
• tubes 5 are dedicated to the injection of liquid fuel and tubes 505 allow the injection of a gaseous fuel.
• the tubes 505 are placed in the fluid veins upstream from the tubes 5.
• the present device and / or the present method although it has an obvious application therein, is not limited to the sole domain of gas turbines but may also be envisaged in any combustion device or method requiring the introduction a fuel in liquid form and a homogeneous mixture between said liquid fuel and the air prior to said combustion.

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

Applications Claiming Priority (3)

Publications (1)

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• 2001
  • 2001-05-10 FR FR0106218A patent/FR2824625B1/fr not_active Expired - Lifetime
• 2002
  • 2002-04-22 WO PCT/FR2002/001381 patent/WO2002090831A1/fr active Application Filing
  • 2002-04-22 EP EP02735482A patent/EP1387986A1/de not_active Withdrawn
  • 2002-04-22 AU AU2002310718A patent/AU2002310718A1/en not_active Abandoned
  • 2002-04-22 US US10/477,127 patent/US7249721B2/en not_active Expired - Fee Related
  • 2002-04-22 JP JP2002587855A patent/JP4368112B2/ja not_active Expired - Fee Related

Non-Patent Citations (2)

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