Device for injecting a mono-propellant with a large amount of flow rate modulation

1. A device for injecting a liquid mono-propellant with a large amount of flow rate modulation, the device being disposed at the upstream end of a wall of a combustion chamber of a rocket engine and including a channel for feeding it with a mono-propellant from a tank,

wherein the device has a single annular speed-up channel connected to the feed channel and having its outlet opening out via an annular injection section, the speed-up channel and the annular injection section being defined firstly by a first wall forming a stationary surface of revolution situated level with said upstream end, and secondly by a second wall forming a surface of revolution on a part that is movable in translation relative to said first wall forming a stationary surface of revolution and presenting beside the combustion chamber a free end that constitutes a fine edge, and

wherein the movable part has a pilot section that is subjected to the effects of the fluid flow rate in the feed channel and that acts against the action of a resilient mechanical element dimensioned to enable the movable part to move into an open position when a predetermined force is exerted on the pilot section.

2. A device according to claim 1 , having a third wall forming a stationary surface of revolution situated facing the annular injection section to receive a jet of the liquid mono-propellant projected through the annular injection section.

3. A device according to claim 2 , wherein the third wall constituting a stationary surface of revolution is formed on a central endpiece connected to the upstream end of the wall of the combustion chamber.

4. A device according to claim 2 , wherein the third wall constituting a stationary surface of revolution is formed on a peripheral ring connected to the upstream end of the wall of the combustion chamber.

5. A device according to claim 1 , wherein the resilient element is constituted by a calibrated spring or by a set of spring washers.

6. A device according to claim 1 , wherein the first wall constituting a stationary surface of revolution and the second wall constituting a surface of revolution on the movable part are frustoconical with their small bases facing towards the third wall constituting a stationary surface of revolution, which third wall is formed on a central endpiece connected to the upstream end of the wall of the combustion chamber.

7. A device according to claim 1 , wherein the first wall constituting a stationary surface of revolution and the second wall forming a surface of revolution on the movable part are frustoconical with their large bases facing towards the third wall constituting a stationary surface of revolution, which third wall is formed on a peripheral ring connected to the upstream end of the wall of the combustion chamber.

8. A device according to claim 2 , wherein the third wall constituting a stationary surface of revolution is frustoconical.

9. A device according to claim 1 , wherein the mono-propellant feed holes are defined by a bell-shaped body having: a bearing flange fastened by bolts to the upstream end of the combustion chamber wall; and a guide surface for the movable part; and also a sealing surface against which a gasket slides.

10. A device according to claim 9 , including a central part secured to a central column that defines the first wall constituting a stationary surface of revolution and that further includes a front wall with a portion situated facing the third wall constituting a stationary surface of revolution, which portion forms a reflector for the jet of liquid mono-propellant projected against the third wall constituting a stationary surface of revolution, which third wall is formed on a peripheral ring connected to the upstream end of the wall of the combustion chamber.

11. A device according to claim 1 , wherein the resilient element is constituted by a spring against which a bearing ring bears, having a position that is adjusted by screws for adjusting in translation the tension of the spring that determines the opening condition for the injector.

12. A device according to claim 1 , further comprising a sensor for sensing movement in translation of the movable part that serves to determine by simple geometrical calculation the flow section through the speed-up channel.

13. A device according to claim 1 , wherein the part that is movable in translation is coupled to an actuator.

14. A device according to claim 10 , wherein the external diameter of the movable part is substantially equal to the maximum external diameter of said stationary central part at the level of said fine edge.