FR2484020A1 - FUEL INJECTION ASSEMBLY FOR TURBOREACTOR CHAMBER - Google Patents

Abstract

FUEL INJECTION KIT FOR A TURBOREACTOR COMBUSTION CHAMBER. THE ASSEMBLY INCLUDES A HOLLOW CYLINDRICAL BODY 1 WHOSE TRUNCONIC BOTTOM 6 RECEIVES THE FUEL SUPPLY 7. THE CAP 8 INCLUDES A CONICAL CENTRAL PART 10 CONNECTED BY A LARGE RADIUS ROUND 11 TO A FLAT ANNULAR PERIPHERAL PORTION 12. THIS PART PROJECTED INJECTION HOLES 5. THE CYLINDRICAL BODY IS EXTENDED BY A SINGLE CENTRIPETE 2 BLADE DELIMING A CYLINDRICAL VOLUME 3 EXTENDED BY A TUBULAR DUCT ENDED BY A CONICAL BOWL 4. A FLANGE FIXED TO THE EDGE OF THE BOWL ALLOWS ITS FIXING ON THE BURNING CHAMBER. THE INJECTION HOLES 5 ARE ARRANGED ON A CIRCLE CONCENTRIC TO THE AXIS OF THE ASSEMBLY WHOSE DIAMETER IS BETWEEN 0.7 AND 0.9 TIMES THE DIAMETER OF THE CIRCLE DETERMINED BY THE LEAKING EDGES 9 OF THE BLADES.

Description

FUEL INJECTION ASSEMBLY

FOR TURBOREACTOR CHAMBER

  The invention relates to a fuel injection assembly for a turbojet combustion chamber, comprising a swirl vane for combustion air and

a fuel injector.

  Fuel injection devices in jet engine combustion chambers are generally designed

  in such a way that they produce an energetic shear

  on the flow of fuel. This shear effect

  is the result of the combined action of airflow, not-

  two swirling vanes, between which

we introduce the fuel.

  The supply of fuel is made in different ways.

  Thus, in French Patent 2,235,274, the

  jector is in the form of an annular nozzle, surrounded by a conduit for the passage of a first air flow, the central portion of which channels a second air flow. The two flows and the fuel pass into swirling vanes and interpenetrate at their exit to form a fuel air mixture in

  which is finely divided.

  In French patent 2,206,796, the fuel is sent into channels opening tangentially into an annular space whose opening delivers a fuel ring.

  sprayed between two swirling air streams.

  In U.S. Patent 3,703,259, fuel is introduced through radial or axial openings in a first whirling air stream. This flow meets a second flow of air swirling in the opposite direction and causes, in the meeting zone, a flow

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  of turbulent air that finely divides the droplets of

  transported by the first flow.

  It appears from the documents analyzed and from the general opinion

  generally accepted by motorists, that the obtaining of a good spray and a good mixture of the fuel in the combustion air necessarily pass through the use of injection assemblies comprising at least two swirling vanes by which passes the combustion air, the fuel being injected directly between the two flows or

being carried by one of the flows.

  The advantages of these aerodynamic injection techniques

  are widely known, but the application of this type of

  jector to small machines becomes imper-

  because of the dimensional constraints of the

  realization and the need to reduce congestion.

  The injection assembly according to the invention always uses

  the shearing of the fuel by a sample of

  air, but uses a simplified device.

  The fuel injection assembly according to the invention for a turbojet combustion chamber in which the fuel droplets are fractionated by a swirling air flow is remarkable in that it comprises

  a unique swirling auliage, for rotating

  air flow, consisting of cylindrical centripetal blading

  whose vanishing edges of the vanes delimit a volume / rac-

  downstream to a cylindro-conical bowl through which the whole

  ble is attached to the combustion chamber and upstream to the

  positive injection of fuel droplets.

  The device for injecting the fuel droplets is

  consisting of a hollow body whose bottom comprises a

  of fuel and the cap of the injection ports

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  projection for the passage of fuel.

  The explanations and figures given below as examples

  ple will understand how the invention can be realized.

  Figure 1 is a perspective view, partially broken away

  of an injection assembly according to the invention.

  Figure 2 shows a section of the assembly according to Figure 1.

  FIGS. 3A and 3B are a view along III-III of FIG.

  2 showing two embodiments of the orifices

injection.

  Figure 1 shows a perspective view and partially

  torn from an injection assembly according to the invention.

  The injection assembly is fixed on the bottom of a chamber

  of combustion and is bathed in a flow of air

compressors.

  The assembly comprises an injection device 1 of drip

  fuel strips, on which is fixed a centripetal swelling or "swirler" 2 defining in its center a cylindrical volume extended by a tubular conduit 3. The duct

  tubular is connected downstream to a conical bowl 4.

  The air coming from the compressors (arrows in full line) passes in the vane 2 and takes a swirling motion

  as a result of the inclination of the blades. The change of direction

  penetrating air flow through the blading is facilitated

  by the shape of the cap 5 of the injection device 1) made

  protruding into the cylindrical volume.

  249 4o023 Li fuel, (-find a broken line) pulverized by

  the nozzles or injection ports 5 in a direction sen-

  parallel to the axis of the device, cuts the

  swirling airflow. The droplets, finely pulverized

  rised by the meeting of air and fuel flows,

  intimately mix with the combustion air and form a

homogeneous mixture.

  The injection device 1 consists of a cylindrical body

  hollow jig presenting, according to the embodiment example, a frustoconical bottom 6 in the center of which is fixed the tube 7 of fuel supply. The cap 8 of the cylindrical body drills aproimaivement,

  has an approximate / conical shape and is close to its

  injection ports 5 distributed according to at least

  a concentric circle. The orifices are arranged

  to be between the trailing edges 9 of the blades of

  swirling. Preferably, the cap 8 of the cymbal body

  lindrique (Fig. 2) has a conical central portion 10

  which is connected by a large-radius rounding 11 to a por-

  planar annular peripheral device 12 on which are

  5. The cap 8, which closes the upstream end of the cylindrical volume 3, is not likely to present carbon deposits because they are swept by the air of the centripetal wiping, and can not s'. warm up because it is cooled by fuel entering the body *

  cylindrical. In order to facilitate the centering of the body of in-

  According to a preferred embodiment, the injection orifices are distributed on a circle concentric with the axis of the axle whose diameter is between 0.7 and 0. , 9 times the diameter of the circle determined by the trailing edges 9

swirl blades 2.

  Injection ports 5 protrude from the surface of cap B. According to embodiments, the

248 4023

  openings lead to the top of cobblestones welded on the

  skin (Fig. 3A), or at the extremity of parallel distal tubes to the axis of the assembly (Fig. 3B). The distance of the orifices

  injection 5 of the surface of the cap 8 has two

  Advantages: avoid fuel runoff on the hatch, obtain a perpendicular fuel flow

  the flow of air at the level of the injection allowing the

  a homogeneous mixture of fine droplets.

  The number of injection ports (5) may be different from the number of gaps between the vanes, however it must be at least equal to the integer nearest one-third of the diameter expressed in mm of the circle on which are located

the orifices.

  The cylindrical volume 3 is extended by a frustoconical bowl 4 which carries on its downstream edge a flange 13. This flange

  cooperates with a fixing device provided on the chamber

  and including means to enable the

  flange both in the axial direction and in the direction

  radial. A cylindrical skirt 14 coaxial to the tax of the

  seems to be fixed near the edge with flange 13. The

  14 facilitates the airflow from

  pressers to the injection assembly and forces it to

  by one or more rows of holes 15 in the bowl 4 where it mixes with the fuel air flow and allows

  better combustion at low speeds.

  The operating mode of the assembly is conventional in the type of aerodynamic injection. The air set in rotation creates a central depression in the axis of the injector which favors a return current in the upstream part

  of the combustion chamber, and the conditions of a good

Combustion is thus brought together.

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  This embodiment adapted to small machines with the technological simplification obtained presents a

  great reliability and an interesting cost.

  The described embodiment provides a set of performance in terms of ignition, stability, holding

thermal and pollution.

248402O

Claims (9)

R E V E N D I C A T IO N S   1. Fuel injection assembly for a turbojet combustion chamber in which the droplets   fuel are fractionated by a turbulent air flow.   lonnant, characterized in that it comprises a swirling vane (2) unique, for the rotation of the air flow, consisting of a centripetal opening vanes   in a cylindrical volume (3) disposed downstream of the device   injection of the fuel droplets, said volume   being extended by a tubular duct connected in a- val to a conical bowl (4).   2. Injection assembly according to claim 1, characterized   in that the device for injecting the fuel droplets is formed of a hollow cylindrical body whose bottom (6) comprises a fuel inlet (7) and the cap (8) of the injection orifices (5). protrusion for the passage of fuel.   3. Injection assembly according to claim 2, characterized   in that the injection ports (5) are made   by tubes parallel to the axis of the injection assembly.   4. Injection assembly according to one of the preceding claims   cedeentes, characterized in that the cap (8) of the cymbal body   hollow lindrique has in the center an approximate form-   cone (10) whose convexity is turned towards the combustion chamber and which is connected by a rounded   radius (11) to a planar annular peripheral portion (12).   Injection assembly according to one of the preceding claims   cedeentes, characterized in that each injection port (5) is located between the trailing edges (9) of two neighboring blades. - T7; = e4g 244-.023   6. Injection assembly according to claim 5, characterized in that   in that lei; Injection ports are located on a concentric circlip at the ltax of the set whose diameter   sl, between 0.7 and 0.9 times the diameter of the circle de-   terminated by the trailing edges (9) of the swirl vanes.   7. Injection assembly according to claim 6, characterized   in that the minimum number of injection ports (5)   is equal to the integer nearest one-third of the outer diameter   awarded in mm from the circle on which the holes are located.   Injection assembly according to one of the preceding claims   cedeentes, characterized in that the conical bowl (4) carries,   near its edge, holes (15) arranged in one or more sieurs rangées.   9. Injection assembly according to claim 8, characterized   in that the conical bowl (4) carries a cylindrical skirt   that (14) coaxial with the axis of the assembly, fixed on the edge of the conical bowl (4) so as to channel the flow of air to the holes (15).