FR2974151A1 - Injection element for injecting cryogenic liquid propellant mixture into e.g. single-element combustion chamber of rocket engine, has annular pipe injecting propellant into chamber and enclosing central body having mixture ignition device - Google Patents

Abstract

The element (201) has first and second annular pipes (206, 207) injecting two cryogenic liquid propellants (E1, E2) into combustion chambers, respectively, where the second annular pipe is arranged coaxial to and outwardly adjacent to the first annular pipe. The first annular pipe encloses a central body (205). The central body comprises a direct propellant mixture ignition device formed with a cavity (209) that communicates with a hot fluid source and with an external surface (210) of the central body through an oblique opening (211) to inject hot fluid e.g. hot gas, in the chambers. The hot fluid source is a pyrotechnic device or a torch. An independent claim is also included for a method for igniting propellant mixture in a combustion chamber.

Description

The present invention relates to an injection element of a mixture of two propellants in a combustion chamber, more particularly designed for a rocket engine with at least one combustion chamber of the type comprising an injector grouping one or a plurality of such elements. 'injection. The invention relates more particularly to an improvement made to such an injection element, in its downstream part where the mixing of the two propellants is carried out, in order to facilitate the ignition of this mixture. Patent document FR 2,712,030 A1 describes an injector of two propellants in a rocket engine combustion chamber comprising a feed structure where the two propellants feed a plurality of injection elements arranged parallel to each other, in an axisymmetric configuration on the surface of a so-called "injection plate" circular structure forming part of the injector. Such an injection plate can thus be associated with a large number of injection elements, for example up to a hundred or more, combining their unit rate to provide the overall flow of the engine. In this injector of the state of the art, each injection element comprises a first conduit for the injection of the first propellant, and a second conduit for the injection of the second propellant, the second duct being annular, coaxial and externally adjacent. at the first conduit. In the present context, the term "annular duct" means a duct whose radial section shows an annular flow section, while "tubular duct" means a duct to the solid section. In addition, the terms "upstream" and "downstream" are defined according to the flow direction of the propellants. Thus, since the propellants are injected into the combustion chamber through coaxial ducts of the injection elements of the FR injector, the turbulences caused in the boundary layers between the concentric and adjacent flows can ensure homogeneous mixing. two propellants by shear in their flow. However, from this basic concept, in which the first conduit is tubular, there are difficulties in changing the geometric parameters to increase the individual power of said

injection element without degrading the quality of injection and combustion. In addition, to initiate the reaction between the two propellants, it is normally necessary to integrate an ignition device in the combustion chamber. For this, it has been proposed to integrate the ignition device in the injection plate, for example centrally or in replacement of one of the injection elements, or laterally in the combustion chamber. In both cases, the size of the ignition device represents a disadvantage for the dimensioning of the combustion chamber. The present invention aims to remedy these two drawbacks. In addition, the present invention also aims at reducing the distance between, on the one hand, the propellant mixing zone and, on the other hand, the energy deposition zone allowing ignition, in order to ensure a regular, reproducible ignition and reliable. These objects are achieved by virtue of the fact that, in an injection element according to at least one embodiment, the first conduit is also annular, surrounding a central body of the injection element, said central body comprising a device ignition of the mixture.

Thanks to these arrangements, it is possible to reduce the passage section of the first propellant flowing in the first duct by varying the diameter of the central body. Therefore, even if the passage sections of all the ducts are increased in order to increase the power of such an injection element, it is possible to make the speed of the propellant circulating in the first duct, annular, do not diminish, all things being equal. The quality of the injection and combustion can thus be maintained independently to the dimensioning of the injection element. In addition, the integration of the ignition device in the central body facilitates its integration into the injector, without additional space, and with flexibility in its positioning related to the distribution of the injection elements on the surface of the plate. 'injection. In particular, said ignition device may comprise a cavity in the central body, adapted to be placed in communication with a source of hot fluid, and opening onto an orifice on an outer surface of the central body for injecting the hot fluid into the chamber of combustion.

Thus, the energy required to trigger the ignition of the propellant mixture can be provided to the mixture by this jet of hot fluid. The source of hot fluid may be, for example, a pyrotechnic device, that is to say, comprising a solid propellant charge, or a torch. Torch means, in this context, a device configured to heat a fluid at a very high temperature. In particular, the fluid can be heated in the torch by chemical reaction, in particular by catalytic decomposition, acoustic resonance, or by electromagnetic means. The hot fluid thus generated by the torch can take the form of a hot gas or a plasma. Alternatively, however, the ignition device may be configured to directly supply ignition energy to the propellant mixture, for example by an electric discharge and / or a focused laser. In order to further improve the mixing of the two propellants downstream, an injection element according to at least one embodiment further comprises a third duct, configured to also inject the first propellant, said third duct being annular and coaxial with the first and second duct and externally adjacent to the second duct. Thus, a double shear of the flow of the second propellant between an internal flow and an external flow rate of the first propellant may result in even better homogenization of the mixture. The invention also relates to an injector comprising one or more injection elements as described above, a combustion chamber comprising such an injector, and a rocket engine comprising such a combustion chamber. By "combustion chamber" is meant, in the present context, not only a single-element main combustion chamber of a rocket engine, but also, inter alia, one or more elements of a multi-element combustion chamber, a prechamber staged combustion engine, or a gas generator for, for example, the actuation of a propellant supply turbopump. The invention relates loosely to a process for igniting a mixture of at least one first propellant and a second propellant in a combustion chamber, wherein said first and second propellants are separately injected into the combustion chamber by a propellant element. injection comprising at least a first and a second annular ducts

coaxial, the first propellant being injected through the first conduit, and the second propellant being injected through the second conduit, externally adjacent to the first conduit, said first and second propellant mixing by turbulence between the two propellants downstream of said first and second ducts; and wherein the mixture is ignited by an igniter incorporated in a central body of the injection member, said central body being surrounded by the first conduit. In particular, in at least one embodiment of such a method, the ignition device ignites the mixture by injection, into the combustion chamber, of a hot fluid from a source of hot fluid, through a cavity in the central body which opens onto an orifice on an external surface of the central body. Alternatively, however, the ignition device can ignite the mixture by direct supply of energy, for example in the form of electric or laser discharge. In at least one embodiment, the first propellant is also injected by a third annular duct and coaxial with the first and second ducts and externally adjacent to the second duct.

The invention will be better understood and its advantages will appear better, on reading the detailed description which follows, of two embodiments shown by way of non-limiting examples. The description refers to the accompanying drawings, in which: FIG. 1 is a schematic view of a liquid propellant rocket engine; FIG. 2 is a longitudinal section of an injection element according to a first embodiment; Figure 3 is a longitudinal section of an injection element according to a second embodiment; Figure 4 is a longitudinal section of an injection element according to a third embodiment; and FIG. 5 is a longitudinal section of an injection element according to a fourth embodiment. A rocket engine 1 with liquid propellants, in particular with cryogenic liquid propellants, is illustrated schematically in FIG. 1. This rocket engine 1 comprises a reservoir 2 for the first propellant, a reservoir 3 for the second propellant, a gas generator 4 fed by the first and second propellants, a turbopump 5 actuated by the combustion gases from the gas generator 4, a main combustion chamber 6 fed with propellants by the turbopump 5, and a convergent-divergent nozzle 7 for the propulsive ejection combustion gases generated in the main combustion chamber 6. In order to obtain an efficient combustion both in the gas generator 4 and in the main combustion chamber 6, these components comprise propellant injection members making it possible to obtain homogeneous mixing and distribution of the propellants. Typically, these injection members take the form of injectors comprising an injection plate in which are distributed several injection elements of the two propellants in an axi-symmetrical configuration. FIG. 2 shows the end portion of an injection element 201 with a tri-coaxial structure for injecting and mixing two propellants E1, E2. The injection element 201 has an axis of symmetry X, which is also the main axis of flow propellants El, E2. The way in which the different constituent parts of this injection element are arranged relative to each other and maintained in their respective positions while being connected to the two propellant supply circuits El, E2, is not shown. The injection element 201 comprises, in its end portion, three concentric tubular walls 202, 203, 204 around a central body 205 so as to form a first, a second and a third annular and coaxial ducts 206,207,208. A shrinkage RE is defined between the end of the outer shell, i.e., the outermost tubular wall 204 and the intermediate walls 202, 203. The outer wall 204 may be part of the injection plate itself, and the intermediate walls 202, 203 may be integrated into a single plain body upstream. The first and third ducts 206, 208 are configured for the injection of the first ergol El, while the second duct 207, located radially adjacent to the outside of the first duct 206 and inside the third duct 208, is configured for the injection of the second propellant 35 E2. The first and second propellants El, E2 being injected at different speeds during operation of the injection element 201, the

shearing inside and outside the annular flow of the second propellant E2 in the RE recess, produce turbulence in the flows of the two propellants E1, E2 ensuring a homogeneous mixture of the two propellants E1, E2. In addition, since the three ducts 206, 207 and 208 are annular, the dimensioning of the injection element 201 can easily be adapted to the total flow rate of propellants required. The central body 205 comprises an ignition device comprising an internal cavity 209 in communication with the outer surface 210 of the central body 205 through an oblique orifice 211. Internal cavity 209 is also connected to a source of hot fluid (not shown). This source of hot fluid may be a pyrotechnic device with a solid propellant charge, or a torch supplied with fluid. The torch supply fluid may be at least one propellant, and in particular at least one of the propellants E1 and E2, the heating thus being effected by a chemical reaction, such as, for example, a catalytic decomposition of a propellant in the torch. The supply fluid may however also be an inert fluid, such as for example helium, and be heated in the torch by acoustic or electromagnetic means. In particular in this second case, this fluid could even be heated to the plasma state. Thus, to trigger the operation of a combustion chamber comprising an injector with a plurality of injection elements including at least one injection element 201 such as that illustrated in FIG. 2, firstly, injection is started first and second propellants El, E2 in the combustion chamber, the first propellant El being injected through first and third ducts 206, 208, and the second propellant E2 being injected through the second duct 207. In the recess RE, in downstream of conduits 206,207 and 208, said first and second propellant mix by turbulence between the two propellants El, E2. To ignite this mixture, the source of hot fluid connected to the ignition device in the central body 205 is activated, and thus the hot fluid, in particular hot gas or plasma, flowing through the internal cavity 209 and the orifice 211 is injected into the combustion chamber obliquely to the propellant mixture E1, E2, energizing this mixture and causing its ignition.

Although the first embodiment relates to an injection element with a hot fluid injection ignition device, the same concept can also be applied with ignition devices by direct supply of energy to the propellant mixture. Thus, in a second embodiment illustrated in FIG. 3, the central body 205 comprises a device for direct ignition of the mixture, in the form of an electrode 212 connected to an electrical source B. An opposite pole of the electrical source B is connected to the outer wall 204 so as to generate an electric discharge S through the propellant mixture E1, E2 to directly provide ignition energy to the mixture and cause its ignition. The remaining elements of the injection element 201 illustrated have substantially the same characteristics and functions as those of the first embodiment and accordingly receive the same reference numerals in the drawing.

In a third embodiment illustrated in FIG. 4, the central body 205 also comprises a device for direct ignition of the mixture, in the form, in this case, of a transparent window 213 between the external surface 210 and an internal cavity 209. of the central body, and a laser source (not shown), located in this central body and arranged to emit, through this window 213, a focused laser beam L to directly supply the ignition energy to the El propellant mixture. , E2 and cause its ignition. The remaining elements of the injection member 201 illustrated also have substantially the same characteristics and functions as those of the first embodiment and accordingly receive the same reference numbers in the drawing. Although the above embodiments relate to tri-coaxial injection elements, the same concept can also be applied to simple coaxial injection elements. Thus, in a fourth embodiment illustrated in FIG. 5, the injection element 201 comprises, in its end part, two concentric tubular walls 202, 204 around a central body 205 so as to form a first and an second ducts 206,207 annular and coaxial. A shrinkage RE is defined between the end of the outer shell, that is to say the outer tubular wall 204 and the intermediate wall 202. The wall 204 may be integrated into the injection plate itself.

The first conduit 206 is configured for the injection of the first ergol El, while the second conduit 207, located radially adjacent to the outside of the first conduit 206, is configured for the injection of the second propellant E2. The first and the second propellants E1, E2 being injected at different speeds during the operation of the injection element 201, the shear between the annular flows of the two propellants El, E2 in the RE shrinkage produce turbulence ensuring a homogeneous mixture two propellants El, E2. In addition, since the two ducts 206, 207 are annular, the dimensioning of the injection element 201 can easily be adapted to the total flow rate of propellants required. As in the first embodiment, the central body 205 includes an ignition device comprising an internal cavity 209 in communication with the outer surface 210 of the central body 205 through an oblique orifice 211. Internal cavity 209 is also connected to a source of hot fluid (not shown). Thus, to trigger the operation of a combustion chamber comprising an injector with a plurality of injection elements including at least one injection element 201 according to this second embodiment, first we start to inject said first and second ergol El, E2 in the combustion chamber, the first ergol El being injected through first and third conduits 206, 208, and the second propellant E2 being injected through the second conduit 207. In the withdrawal RE, downstream of conduits 206,207 and 208, said first and second propellant are mixed by turbulence between the two propellants El, E2. To ignite this mixture, the source of hot fluid connected to the ignition device in the central body 205 is activated, and thus the hot fluid flowing through the internal cavity 209 and the orifice 211 is injected into the combustion chamber obliquely at mixture of propellants E1, E2, energizing this mixture and causing its ignition.

Although the present invention has been described with reference to specific exemplary embodiments, it is evident that various modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various illustrated embodiments can be combined in additional embodiments. For example, direct energy ignition devices, such as those of the second and third embodiments, may also be used in simple coaxial injection elements such as that illustrated by the fourth embodiment. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Claims (8)

REVENDICATIONS1. Injection element (201) of a mixture of at least one CLAIMS1. Injection element (201) of a mixture of at least one first propellant (El) and a second propellant (E2) in a combustion chamber (4,6), comprising a first conduit (206) for injection of the first propellant (El), and a second duct (207) for the injection of the second propellant (E2), the second duct (207) being annular, coaxial and externally adjacent to the first duct (206), the element of injection (201) being characterized in that the first conduit (206) is also annular, surrounding a central body (205) of the injection element (201), said central body (205) comprising an ignition device of the mixed. The injection element (201) according to claim 1, wherein said ignition device comprises a cavity (209) in the central body (205), adapted to be placed in communication with a source of hot fluid, and communicating with an outer surface (210) of the central body (205) through an orifice (211) for injecting the hot fluid into the combustion chamber (4,6). Injection element (201) according to claim 2, wherein the source of hot fluid is a pyrotechnic device or a torch. Injection element (201) according to claim 1, wherein said ignition device is configured to directly supply ignition energy to the propellant mixture (E1, E2), for example by an electric discharge (S ) and / or a focused laser beam (L). An injection element (201) according to any one of claims 1 to 4, further comprising a third conduit (208) configured to also inject the first propellant (El), said third conduit (208) being annular and coaxial with the first and second conduits (206,207) and externally adjacent to the second conduit (207). Injector comprising one or more injection elements (201) according to any one of claims 1 to 5. 7. Combustion chamber (4,6) comprising at least one injector according to claim 6. Rocket engine (1) comprising at least one combustion chamber (4,6) according to claim 7. 8. A method of igniting a mixture of at least one first propellant and a second propellant (E2) in a combustion chamber (4,6) wherein said first and second propellants (E1, E2) are separately injected into the combustion chamber (4,6) by an injection element (201) comprising at least a first and a second annular coaxial ducts (206,207), the first propellant (El) being injected through the first duct (206), and the second propellant (E2) being injected by the second duct (207), externally adjacent to the first duct (206), said first and second propellant (E1, E2) being mixed by turbulence between the two propellants (E1, E2) downstream of said first and second conduits (206, 207) and the mixture is ignited by an ignition device incorporated in a central body (205) of the injection element (201), said central body (205) being surrounded by by the first conduit (206) 10. The ignition method according to claim 9, wherein the ignition device ignites the mixture by injection into the combustion chamber (4,6) of a hot fluid from a source of hot fluid through a cavity (209) in the central body (205) which opens onto an orifice (211) on an outer surface (210) of the central body (205). 11. Ignition method according to claim 9, wherein the ignition device ignites the mixture by direct supply of energy, for example in the form of electric or laser discharge. 12. The ignition method according to any one of claims 9 to 11, wherein the first propellant (El) is also injected by a third duct (208) annular and coaxial with the first and second ducts (206,207) and externally adjacent to the second conduit (207).