Combustion chamber comprising additional injection devices opening up directly into corner recirculation zones, turbomachine comprising such a chamber and fuel supply method for such a chamber

Abstract

A combustion chamber for an aircraft turbomachine includes an annular chamber end wall and an annular row of injection systems mounted in the annular chamber end wall. Each injection system includes at least one air inlet swirler and a main fuel injection nozzle to output a fuel stream centered on an injection axis and including a central recirculation zone and a corner recirculation zone extending as an annulus around the central recirculation zone chamber. The combustion chamber also includes a plurality of additional fuel injection devices mounted in the chamber end wall to inject fuel directly into the corresponding corner recirculation zones produced by the corresponding injection systems at an operating speed less than or equal to the idling speed.

Claims

1. A combustion chamber for an aircraft turbomachine, comprising: an annular chamber end wall and two coaxial annular walls connected to each other by said annular chamber end wall and centred on a longitudinal axis of the combustion chamber; and an annular row of injection systems mounted in the annular chamber end wall, each injection system comprising at least one air inlet swirler and a main fuel injection nozzle configured to output a fuel stream centred on an injection axis and comprising a central recirculation zone and a corner recirculation zone extending as an annulus around the central recirculation zone; wherein: the combustion chamber also comprises a plurality of additional fuel injection devices mounted in the chamber end wall and configured to inject fuel directly into the corresponding corner recirculation zones produced by the injection systems; each additional injection device comprises at least one secondary fuel injection nozzle connected to a fuel supply source, and installed to pass through the chamber end wall at a spacing from the corresponding injection system; and said at least one secondary injection nozzle of each additional injection device is fitted with a valve configured to go into an open state when a fuel pressure corresponds to an operating speed of the turbomachine less than or equal to the idle speed, and to go into a closed state when a fuel pressure corresponds to an operating speed of the turbomachine greater than the idle speed.

2. The chamber according to claim 1, wherein said at least one secondary fuel injection nozzle of each additional injection device consists of a plurality of secondary fuel injection nozzles arranged symmetrically about a plane passing through the longitudinal axis of the combustion chamber and through the injection axis of the corresponding injection system.

3. The chamber according to claim 2, wherein said plurality of secondary fuel injection nozzles of each additional injection device comprises four secondary fuel injection nozzles.

4. The chamber according to claim 2, wherein each additional injection device comprises a fuel distribution circuit, connecting each secondary fuel injection nozzle of the additional injection device to said fuel supply source.

5. A turbomachine, comprising: the combustion chamber according to claim 1.

6. A method of supplying fuel to the combustion chamber according to claim 1, comprising: supplying fuel to the secondary fuel injection nozzles when the turbomachine is functioning at a speed less than or equal to the idle speed, such that the additional fuel injection devices then inject additional fuel directly into the corner recirculation zones produced by the corresponding injection systems of the combustion chamber, and stopping the fuel supply to the secondary fuel injection nozzles when the turbomachine is functioning at a speed greater than the idle speed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be better understood and other details, advantages and characteristics of it will become clear after reading the following description given as a non-limitative example with reference to the appended drawings in which:

(2) FIG. 1, already described, is a partial diagrammatic axial sectional view of a known type of a turbomachine;

(3) FIG. 2, already described, is a partial diagrammatic axial sectional view of a combustion chamber of the turbomachine in FIG. 1;

(4) FIG. 3, already described, is a partial diagrammatic axial sectional view of an injection system installed in the combustion chamber in FIG. 2;

(5) FIG. 4 is a view similar to FIG. 2, illustrating a combustion chamber according to a preferred embodiment of the invention.

(6) FIG. 5 is a partial diagrammatic view of the combustion chamber in FIG. 4, from the upstream side.

(7) In all these figures, identical references may denote identical or similar elements.

DETAILED PRESENTATION OF PREFERRED EMBODIMENTS

(8) FIGS. 4 and 5 illustrate a combustion chamber 18 of a turbomachine for example similar to the turbomachine in FIG. 1, except that the combustion chamber 18 also comprises a plurality of additional fuel injection devices 70 mounted in the chamber end wall 40 and configured to inject fuel 71 directly into the corresponding corner recirculation zones 64 of the injection systems 42.

(9) More precisely, each additional injection device comprises one or several secondary fuel injection nozzles 72 (shown very diagrammatically) installed through the chamber end wall 40. In the example illustrated, the secondary fuel injection nozzles 72 also pass through a chamber end wall deflector 73.

(10) These secondary fuel injection nozzles 72, for example four of them, are at a spacing from the corresponding injection system 42 as shown more clearly on FIG. 5, such that the secondary fuel injection nozzles 72 open up facing the corner recirculation zone 64 induced by the injection system 42.

(11) Note that only one additional fuel injection device 70 is visible on FIG. 5, since the two devices following it have been omitted to make the figure more easily understandable.

(12) These secondary fuel injection nozzles 72 are arranged to be symmetric about a plane P (FIG. 5) passing through the longitudinal axis 28 of the combustion chamber and through the injection axis 44 of the corresponding injection system 42 (FIG. 4).

(13) The secondary fuel injection nozzles 72 of each additional fuel injection device 70 are connected to a fuel supply source, that may for example be the injector 74 that supplies the corresponding injection system 42.

(14) If each additional fuel injection device 70 comprises several secondary injection nozzles 72, as in the illustrated example, these secondary injection nozzles 72 are preferably connected to a fuel distribution system 76 itself connected to the fuel supply source.

(15) In the illustrated example, the fuel distribution circuit is in the form of a conduit forming a closed loop around the injection system 42. A pipe 78 (only visible very diagrammatically on FIG. 4) connects this conduit to the injector 74.

(16) Therefore the fuel distribution circuits for each of the different additional fuel injection devices 70 are independent of each other.

(17) As a variant, the fuel distribution circuits for each of the different additional fuel injection devices 70 can be connected to each other.

(18) As another variant, the different secondary fuel injection nozzles 72 of each additional fuel injection device 70 can be connected to the fuel source independently of each other.

(19) As another variant, the fuel supply source may be not shared by the main 54 and secondary 52 fuel injection nozzles, and it can be a source dedicated only to the secondary fuel injection nozzles.

(20) Note that only the main fuel injection nozzles 54 are of the aerodynamic or aeromechanical type. The secondary fuel injection nozzles 72 do not have any air inlets and therefore are used only for spraying fuel.

(21) The additional fuel injection devices 70 may be used to implement a method for supplying fuel to the combustion chamber 18 described above.

(22) This method comprises firstly the fuel supply to the main injection nozzles 54, in a conventional manner.

(23) This method also comprises the fuel supply to the secondary injection nozzles 72 when the combustion chamber is operating at a speed less than or equal to the idle speed, and cutting off the fuel supply to these secondary injection nozzles 72 when the combustion chamber operates at a speed greater than the idle speed.

(24) Thus, when the combustion chamber is functioning at a speed less than or equal to the idle speed, the additional fuel injection devices 70 inject additional fuel directly into the corner recirculation zones 64 produced by each of the injection systems 42 of the combustion chamber 18.

(25) The method is implemented mechanically by means of valves fitted on the secondary injection nozzles 72 and configured to go into an open state when the fuel pressure corresponds to an operating speed less than or equal to the idle speed, and to go into a closed state when the fuel pressure corresponds to an operating speed greater than the idle speed.

(26) Therefore the invention is useful particularly to supply secondary fuel injection nozzles 72 with fuel during ignition of the combustion chamber. In particular, in the case of an in-flight restart, this provides the ability to reignite the chamber by adding combustion zones in corner recirculation zones 64, which is conducive to propagation of the energy core.

(27) The invention also stabilises the flame at low speeds and in particular, it lowers the combustion chamber flameout limit due to the fact that the corner recirculation zones 64 are the zones in which combustion stops first during a flameout in the combustion chamber.

(28) The invention also provides a means of improving the homogeneity of the combustion zone within the combustion chamber, which can improve the temperature profile at the outlet from the combustion chamber, and more generally reduce NOx emissions.