System and method of controlling pressure oscillations of hydrodynamic origin for a solid propellant thruster
View Patent ↗The invention provides a system for passively controlling pressure oscillations of hydrodynamic origin in a solid propellant thruster comprising a body containing a charge of solid propellant, the system comprising at least one insert disposed in the thruster body transversely relative to the flow direction of the combustion gases of the solid propellant. The insert has an opening of non-axisymmetric shape so as to generate a three-dimensional effect on the flow and prevent axisymmetric turbulent modes from forming in the thruster. Thus, the control system of the invention serves to break the symmetry of the flow and thus prevents axisymmetric turbulence forming which is the source of instability that the present invention seeks to control. The present system is applicable to existing thrusters.
1. A system for passively controlling pressure oscillations of hydrodynamic origin in a solid propellant thruster comprising a body containing a charge of solid propellant, the system comprising at least one insert disposed in said thruster body transversely relative to a combustion gas flow channel formed in the solid propellant charge, said insert including a single opening of non-axisymmetric shape that is different from the shape of the gas flow channel so as to generate a three-dimensional effect on the flow in order to prevent axisymmetric turbulent modes from forming in the thruster.
2. A system according to claim 1 , wherein said non-axisymmetric opening of the insert is present in the flow channel throughout the duration of the combustion of the solid propellant charge.
3. A system according to claim 2 , wherein the insert is made of a “rigidimer” composite material.
4. A system according to claim 1 , wherein said non-axisymmetric opening of the insert appears in the flow channel from a predetermined instant of the combustion of the solid propellant charge.
5. A system according to claim 4 , wherein the insert has an opening of shape that varies from a shape that is axisymmetric at the beginning of combustion to a shape that is not axisymmetric as from a predetermined instant of combustion.
6. A system according to claim 5 , wherein the insert of varying shape comprises a first portion constituted by a first material and a second portion constituted by a second material and occupying part of the non-axisymmetric opening of the insert, said second material having a speed of ablation that is faster than that of the first material.
7. A system according to claim 6 , wherein said insert is made of an elastomer composite material or of a composite material comprising both elastomer and “rigidimer”.
8. A system according to claim 5 , wherein the insert of varying shape comprises a first portion and a second portion occupying part of the non-axisymmetric opening of the insert, said second portion being weaker than said first portion.
9. A system according to claim 4 , wherein a portion of the propellant charge placed upstream from the insert having a non-axisymmetric opening presents a flow channel with an initial diameter that is inscribed within the non-axisymmetric opening of said insert.
10. A system according to claim 1 , wherein the thruster body contains a single block of solid propellant, the insert with a non-axisymmetric opening being disposed within said block.
11. A system according to claim 1 , wherein the thruster body contains a propellant charge that is segmented into a plurality of blocks, and the insert having a non-axisymmetric opening is disposed in the inter-segment space that exists between two successive blocks.
12. A system according to claim 1 , wherein the thruster body contains a propellant charge that is segmented into a plurality of blocks, with at least one of the blocks being inhibited, the insert having a non-axisymmetric opening being disposed on the top face of the inhibited block.
13. A system according to claim 1 , wherein said opening of the insert is in the shape of a star.
14. A system according to claim 1 , wherein said opening is in the shape of crenellations.
15. A method of controlling pressure oscillations of hydrodynamic origin in a solid propellant thruster, wherein a three-dimensional effect is generated on the flow to prevent axisymmetric turbulent modes forming, by placing an insert in the thruster transversely relative to a combustion gas flow channel formed in the thruster, said insert having a single opening of non-axisymmetric shape that is different from the shape of the gas flow channel.
16. A method according to claim 15 , wherein the three-dimensional effect on the flow is generated throughout the duration of the combustion of the solid propellant charge.
17. A method according to claim 15 , wherein the three-dimensional effect on the flow is generated from a predetermined instant of the combustion of the solid propellant charge.
18. A method according to claim 17 , wherein the three-dimensional effect on the flow is generated from a predetermined instant by means of an insert having an opening of shape that varies from an axisymmetric shape at the beginning of combustion to a non-axisymmetric shape at a predetermined instant of combustion.
19. A method according to claim 18 , wherein the insert of varying shape comprises a first portion constituted by a first material and a second portion constituted by a second material and occupying part of the non-axisymmetric opening of the insert, said second material having a speed of ablation that is greater than that of the first material.
20. A method according to claim 18 , wherein the insert of varying shape comprises a first portion and a second portion occupying part of the non-axisymmetric opening of the insert, said second portion being weaker than said first portion.
21. A method according to claim 17 , wherein the three-dimensional effect on the flow is generated from a predetermined instant of the combustion by means of a portion of the propellant charge placed upstream from the insert having a non-axisymmetric opening and presenting a flow channel of an initial diameter that is inscribed in the non-axisymmetric opening of said insert.
22. A method according to claim 15 , wherein the thruster body contains a single block of solid propellant, the insert having a non-axisymmetric opening being disposed inside the block.
23. A method according to claim 15 , wherein the thruster body contains a propellant charge that is segmented into a plurality of blocks, the insert having a non-axisymmetric opening being disposed in the inter-segment space that exists between two successive blocks.
24. A method according to claim 15 , wherein the thruster body contains a propellant charge that is segmented into a plurality of blocks including at least one block that is inhibited, the inset having a non-axisymmetric opening being disposed on the top face of the inhibited block.
25. A method according to claim 15 , wherein said opening in the insert is in the shape of a star.
26. A method according to claim 15 , wherein said opening in the insert is in the form of crenellations.