Multipoint injection device for a combustion chamber of a turbine engine

1. A fuel injector device for an annular combustion chamber of a turbine engine, the device comprising:

a pilot circuit continuously feeding an injector leading into a first venturi;

a multipoint circuit intermittently feeding injection orifices formed in a downstream face of an annular ring mounted in an annular chamber formed at the upstream end of a second venturi coaxially surrounding the first venturi; and

thermal insulation means for insulating the downstream face of the annular ring, the thermal insulation means comprising an annular cavity formed around the injection orifices between the downstream face of the annular ring and a downstream wall of the annular chamber and configured to be filled in operation with air or with coked fuel, the downstream face of the annular ring and the downstream wall of the annular chamber extending at least partially in a radial direction.

2. A device according to claim 1 , further comprising a cooling circuit for cooling the annular ring by causing fuel of the pilot circuit to flow in an inner annular channel formed between inner cylindrical walls of the annular ring and of the annular chamber, and in an outer annular channel formed between outer cylindrical walls of the annular ring and of the annular chamber.

3. A device according to claim 2 , wherein one of the inner and outer channels communicates with the annular cavity, the other one of the inner and outer channels being isolated from the annular cavity.

4. A device according to claim 3 , wherein the radially inner or outer periphery of the downstream face of the annular ring includes an annular rim having a downstream edge that cooperates with the downstream wall of the annular chamber to define an annular passage for communication between the annular cavity and one of the inner and outer channels of the cooling circuit.

5. A device according to claim 2 , wherein the radially outer periphery of the downstream face of the annular ring bears radially against the outer cylindrical wall of the chamber to center the annular ring in the chamber.

6. A device according to claim 1 , wherein each injection orifice in the annular ring is formed in a stud projecting from the downstream face of the annular ring, each studs being inserted into abutment in respective cavities of corresponding projections formed on the downstream face of the annular chamber.

7. A device according to claim 6 , wherein each cavity in a projection leads to the outside of the annular chamber via a hole in alignment with the injection orifice of the corresponding stud, the hole having a diameter that is greater than the diameter of the injection orifice.

8. A device according to claim 1 , wherein the injection orifices are formed in cylindrical pins fastened in holes in the downstream face of the annular ring, the pins projecting beyond the downstream face and forming positioning and centering means in the annular chamber.

9. A device according to claim 8 , wherein the injection orifice in each pin has a downstream end of greater diameter.

10. A device according to claim 8 , wherein the radially inner end of the downstream face of the annular ring includes an annular rim for axial positioning in the annular chamber.

11. An annular combustion chamber for a turbine engine, the combustion chamber comprising at least one fuel injector device according to claim 1 .

12. A device according to claim 1 , wherein an upstream end of the annular ring abuts a radial shoulder of a duct.