Device for injecting mono-propellant at a flow rate that can be modulated with an injection speed that is stable

The injector device for injecting a liquid mono-propellant with a large degree of flow rate modulation and an injection speed that is stable, and that is closable for extinction and re-ignition purposes, is disposed at an upstream end of the wall of a combustion chamber of a rocket engine. The device includes at least one feed channel for feeding mono-propellant from a tank, and first and second concentric annular speed-up channels connected to the feed channels and having outlets opening out respectively via first and second annular injection sections situated in a plane that is substantially perpendicular to the axis of the chamber. The first and second concentric annular channels are oriented to converge on each other with a resultant that lies substantially along the axis of the chamber, forming an angle that is predefined in such a manner as to output two sheets of injected liquid mono-propellant that mutually in an atomization ring at a predetermined distance from the upstream end forming the end wall of the combustion chamber and in the vicinity of the axis of the combustion chamber.

FIELD OF THE INVENTION

The present invention relates to a device for injecting a liquid mono-propellant with a high degree of flow rate modulation and with an injection speed that is stable, the device being shuttable for extinction and re-ignition purposes, being disposed at an upstream end of the wall of a combustion chamber of a rocket engine, and including a feed channel for feeding mono-propellant from a tank.

PRIOR ART

Various liquid propellant injector devices for rocket engines are already known.

By way of example,FIG. 2shows a “pintle” type device that makes it possible, for bi-propellant injection, to modulate the flow rate to a large extent as a result of the injection sections being varied by a movable part34.

In the system ofFIG. 2, an oxidizer is injected into the combustion chamber30through an annular orifice32between a movable part34and a stationary part36coaxially located therein. A fuel is also injected through an annular orifice38around the movable part34, between the movable part and a portion of the wall of the combustion chamber30. The fuel and the oxidizer diverge away from their respective outlet orifices and form jets that meet and mix in an annular combustion zone designated by reference40.

Nevertheless, implementing two independent feed systems for a fuel and for an oxidizer makes fabrication rather complex and the device cannot be compact, in particular when it incorporates a shutter rod.

In prior art devices, the resultant of the two sheets is oriented so as to be directed towards the wall of the chamber.

In known injector devices of that type, mixing and combustion therefore tend to take place very close to the wall of the combustion chamber, thereby reducing its lifetime, or else giving rise to large chamber diameters, and it may also favor trickling along the wall. Furthermore, the large portion projecting into the chamber constitutes an element of weakness.

DEFINITION AND OBJECT OF THE INVENTION

The present invention seeks to remedy the above-mentioned drawbacks and to enable an injector device to be provided that is compact and suitable for injecting a mono-propellant that can be extinguished and re-ignited, the device presenting a design that is simplified and enabling the rate of injection to be modulated and also shut off, while increasing the lifetime of the combustion chamber, and reducing any risk of trickling on its wall.

In accordance with the invention, these objects are achieved by a device for injecting a liquid mono-propellant with a high degree of flow rate modulation and an injection speed that is stable, the device being closable for extinction and re-ignition purposes, being disposed at an upstream end of the wall of a combustion chamber of a rocket engine, and including at least one feed channel for feeding mono-propellant from a tank, wherein:

the device includes first and second concentric annular speed-up channels connected to the feed channels and having outlets opening out respectively via first and second annular injection sections that are situated in a plane that is substantially perpendicular to the axis of the chamber, the first and second concentric annular channels being oriented to converge towards each other with a resultant that lies substantially along the axis of the chamber, forming a predefined angle so as to output two sheets of injected liquid mono-propellant that impact against each other in an atomization ring at a predetermined distance from the upstream end forming the end wall of the combustion chamber and in the vicinity of the axis of the combustion chamber;

the first annular speed-up channel and the first annular injection section are 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 secured to a part that is movable in translation relative to said first wall forming a stationary surface of revolution;

the second annular speed-up channel and the second annular injection section are defined firstly by a third wall forming a stationary surface of revolution situated at the level of said upstream end and secondly by a fourth wall forming a surface of revolution secured to said part that is movable in translation relative to said first and third walls forming stationary surfaces of revolution; and

the part that is movable in translation relative to the first and third walls forming stationary surfaces of revolution has a plurality of radial orifices to enable the second speed-up channel to be fed from a common feed channel that feeds the first speed-up channel directly.

The movable part includes a pilot section subjected to the effects of the fluid flow rate of the mono-propellant in the feed channel and acting against the action of a resilient element dimensioned to move the movable part into an open position when a predetermined force is exerted on the pilot section.

The resilient element may be constituted by a calibrated spring or by a set of spring washers.

The present invention relies on technology based on associating a system for modulating the flow rate of a mono-propellant with the mono-propellant being atomized by impact between two sheets having a resultant stemming from the orientations of the injection channels, which resultant lies substantially along the axis of the chamber, without any large projections being formed in the combustion chamber.

In a particular embodiment, the first and second walls form surfaces of revolution that are frustoconical with their small bases directed towards the combustion chamber.

Similarly, the third and fourth walls may form surfaces of revolution that are frustoconical with their large bases directed towards the combustion chamber.

In an advantageous embodiment, the mono-propellant feed holes are defined by a bell-shaped body having a bearing flange fastened by bolts on the upstream end of the combustion chamber wall, and a plurality of coaxial cylindrical guide walls for: guiding the movable part; positioning a central part for centering the third wall constituting a stationary surface of revolution; and providing sealing between said body and the movable part.

The device is designed in such a manner as to obtain regular injection sections over the entire perimeter and shutting that is almost perfect.

In a particular embodiment, the first wall constituting a stationary surface of revolution is defined by a portion in the form of a lip projecting from the upstream end of the combustion chamber wall, and the third wall constituting a stationary surface of revolution is defined by a portion in the form of a lip projecting from a stationary part fitted to said upstream end of the wall of the combustion chamber.

In general, for a mono-propellant, the invention enables the injection flow rate to be modulated using a small flow rate on ignition and subsequently a large amount of variation by having an injection section that is variable while enabling the speed of injection to be relatively stable.

Injection may be closed off completely in the injection plane when the mono-propellant flow rate is zero, thereby avoiding any combustion in the cavities of the injector, any combustion residues, or indeed any explosions, given the nature of certain propellants.

The system is mechanically simple and very compact, having only a single propellant feed channel.

The end wall of the combustion chamber is little exposed to significant recirculation because of the “axial” orientation, it does not have a projecting injector, which is particularly useful when a shutter rod is incorporated therewith.

Atomization takes place by the propellant being projected, with the resultant of the propellant injection axes being oriented close to the axis of the chamber, thereby avoiding potential trickling on the wall of the combustion chamber and rapid damage thereto as a result of combustion.

Furthermore, the injector device is easily adaptable and a central part for defining an injection section may easily be interchanged. In addition, an empty space at the center of the injector device makes it possible to incorporate a throat shutter or an ignitor, for example.

The device of the invention is applicable to any rocket engine with a high degree of thrust modulation and it also relates to such a rocket engine fitted with an injector device of the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

With reference toFIG. 1, there can be seen a diagrammatic longitudinal section view of a mono-propellant injector device of the invention.

FIG. 1shows part of a combustion chamber9defined by a wall90having an upstream end identified by reference91.

A bell-shaped body1has a base in the form of a flange that is fastened to the end wall91by fastener elements92such as bolts. The body1defines liquid propellant feed holes that are in communication with a tank via a space defined by a second body11fastened by screws or bolts12to the bell-shaped body1and possibly comprising a plurality of parallel channels distributed around an annular zone of the body1and opening out into an annular space at the level of the end wall91.

The chamber end wall91presents a projecting portion93in the form of a skirt or lip that is circularly symmetrical and defines a stationary surface of revolution94on the face looking towards the speed-up channel41. The stationary surface of revolution94advantageously presents a shape that is frustoconical with its small base facing towards the inside of the combustion chamber9.

The bell-shaped body1presents a central cavity in which a stationary central part7is inserted that may for example present a tubular portion71having a thread enabling it to be secured to the body1. The central portion7may present a shoulder75that comes into abutment against the body1to position the central portion7accurately with its portion facing towards the chamber9having a projecting portion72in the form of a skirt or lip that is circularly symmetrical and that defines a stationary surface of revolution73on the base facing towards the speed-up channel41. The stationary surface of revolution73advantageously presents a frustoconical shape with its large base directed towards the inside of the combustion chamber9.

The inner and outer stationary projecting portions72and93form respective points at their free terminal ends that lie in a plane that is substantially perpendicular to the axis of the chamber.

A movable part5of annular shape is coaxial with the stationary central part7and with cylindrical tubular portions of the body1.

The movable part5that is placed in an annular housing of the body1between two tubular portions of said body is guided to move in translation along the axis of the chamber9.

Sealing gaskets51and52are disposed between firstly the movable part5and secondly the cylindrical walls of the tubular portions of the body1.

The propellant feed holes6or the various parallel channels are formed through the outer tubular portion of the body1.

Radial orifices61are formed in the movable part5to enable the mono-propellant to flow on both sides of the downstream portion of the movable part5.

One face53of the movable part5defines a pilot section that is subjected to the variations in the flow rate of the propellant flowing in the annular portion of the feed channel6, these flow rate variations varying substantially with pressure.

The rear face of the movable part5is subjected to the action of a resilient element such as a spring8that is interposed between the stationary body1and the movable part5. A channel15serves to exhaust unwanted fluids to the outside during the upward movement of the movable part5.

The front terminal portion of the movable part5facing towards the combustion chamber9presents two surfaces of revolution54and55that are advantageously frustoconical in shape.

The surface of revolution54constitutes an outer frustoconical surface with its small base directed towards the combustion chamber9, while the surface of revolution55constitutes an inner frustoconical structure with its large base directed towards the combustion chamber9and it is situated, like the small base of the frustoconical structure54, in a plane that is substantially perpendicular to the axis of the combustion chamber.

A first annular speed-up channel41connected directly to the feed channels6and having its outlet opening via a first annular injection section31is defined by the stationary surface of revolution94and by the movable surface of revolution54.

In similar manner, a second annular speed-up channel42connected to the feed channels6via the orifices61and having its outlet opening out via a second annular injection section32is defined by the stationary surface of revolution73and by the movable surface of revolution55.

The spring8is dimensioned so as to urge the movable part5into the position for closing the propellant injection sections31and32in the outlet plane of the injector when the flow rate of the mono-propellant is zero, and for causing the propellant injection sections31and32to open when the flow rate of the propellant acting on the pilot section53produces a predetermined effect on the spring8.

The central part7, which can be dismantled, confers modularity that enables the shape and the angle of inclination of the stationary inner surface of revolution73to be adapted.

At the outlets from the concentric speed-up channels41and42that are oriented in converging directions at a predefined angle, the mono-propellant ejected via the concentric outlet sections31and32is in the form of two sheets that impact against each other in an atomization ring that is at a predetermined distance from the upstream end91forming the end wall of the combustion chamber and that is in the vicinity of the axis of the combustion chamber.

Variation in flow rate, which itself varies substantially in proportion to pressure, has the effect on the pilot section53of controlling the movement in translation of the movable part5, thereby giving rise to variation in the first and second annular injection sections31and32.

The fluid flowing in the feed channel6feeds the first speed-up channel41and, via the orifices61, the second speed-up channel42, the first and second speed-up channels41and42forming a predefined angle so as to define two annular sheets of injected liquid propellant with high-quality impact between these two injected sheets giving rise to atomization at the impact.

The resultant of the first and second speed-up channels41and42is directed parallel to the axis of the combustion chamber9or even slightly towards the center of said chamber.

The two sheets impact in a ring at a distance from the end wall91of the chamber, with a resultant along the axis of the chamber and recirculation is limited.

The bell-shaped body1is machined in a single stage, in particular to confer thereon a central tubular portion that serves to position the centering central part7and to guide the part5that is movable in translation parallel to the axis of the chamber9.

Given the statically-indeterminate nature of the system, good concentricity is guaranteed to ensure the following simultaneously:guidance of the movable part5;sealing with the outer surface of the movable part5;long centering of the part7for centering the inner lip72that contributes to defining the inner speed-up channel42, in co-operation with the movable part5; andshort centering of the body1and plane bearing of the base flange of said body1on the end plate of the chamber91that, by means of its projecting portion93, contributes to defining the outer speed-up channel41, in co-operation with the movable part5.

The facts of minimizing the number of parts that are stacked one on another and of machining long cylinders in a single stage serve to guarantee good operation.

Furthermore, the fact that the free end of the movable part5is relatively fine serves to minimize the effects of pressure in the chamber9on the spring8, or on some equivalent resilient element such as a stack of spring washers.

FIG. 1shows a central rod13that is axially movable under drive from a spring14and that can serve for example to control selective shutting of the throat of the combustion chamber9. Under such circumstances, the centering part7that is inserted in the body1and that is secured thereto includes a portion74that provides first short guidance for the movable central rod13relative to the stationary body1. Additional short guidance is provided in the combustion chamber so that long guidance is established in combination with the first short guidance.

At the center of the injector, instead of the shutter rod, it is possible to install an ignitor.

Naturally, various modifications and additions may be applied without going beyond the ambit of the present invention.

Thus, for example, the chamber end wall91and the side wall90of the chamber9may include a protective covering (not shown inFIG. 1).

The device is also suitable for being adapted to be controlled in force. Under such circumstances, the pilot section53and the spring8are omitted and the movable part5is coupled to an actuator, e.g. of mechanical, hydraulic, or electrical type, via a plurality of rods that pass through the body1, in the bottom of a groove via a plurality of holes.

In the present description, and in conventional manner, a member is said to be for “short centering” when it defines a zone of contact that can be modelled as a sphere-cylinder contact.

If the length of the contact zone is L and if the diameter of the short centering member is D, then a relationship of the following type applies:
L≦0.8D

Preferably, it is possible to choose the value for the length L of the contact zone to lie within the following range of values:
0.1D≦L≦0.5D

In more preferred manner, it is possible to select the value for the length L of the contact zone to lie in the following range of values:
0.1D≦L≦0.3D

Furthermore, likewise in conventional manner, a member is said to be for “long centering” when it defines a contact zone that can be modelled as a pivoting-sliding contact.

If the length of the contact zone is L and if the diameter for the member for long centering is D, then a relationship of the following type applies:
D≦L

Preferably, a value may be selected for the length L of the contact zone that lies in the following range of values:
1.5D≦L