Pogo effect correction system

Abstract

A pogo effect corrector system for a liquid propellant feed system of a rocket engine includes a liquid propellant feed pipe portion, and a hydraulic accumulator including a tank connected firstly to the feed pipe portion firstly via at least one take-off passage opening out into a take-off segment of the feed pipe portion, and secondly via at least one rejection passage opening out into the tank at an intermediate level lying between the at least one take-off passage and the top of the tank, wherein the feed pipe portion possesses a constriction segment where the flow section of the feed pipeline portion is less than the flow section of the take-off segment, and wherein at least one rejection passage opens out into the feed pipeline portion in the constriction segment.

Claims

1. A pogo effect corrector system for a liquid propellant feed system of a rocket engine, the corrector system comprising: a liquid propellant feed pipe portion connected to the rocket engine; a hydraulic accumulator comprising a tank provided with a gas feed and connected firstly to the feed pipe portion via at least one take-off passage opening out into a take-off segment of the feed pipe portion, and secondly via at least one rejection passage opening out into the tank at an intermediate level lying between said at least one take-off passage and the top of the tank; wherein the feed pipe portion possesses a constriction segment where the flow section of the feed pipe portion is less than the flow section of the take-off segment; and wherein said at least one rejection passage opens out into the feed pipe portion at the constriction segment.

2. A pogo effect corrector system according to claim 1, wherein the flow section at the constriction segment is at least 1% less than the flow section of the take-off segment.

3. A pogo effect corrector system according to claim 1, wherein the flow section of the feed pipe portion varies continuously.

4. A pogo effect corrector system according to claim 1, wherein the diameter of the feed pipe portion is reduced at the constriction segment.

5. A pogo effect corrector system according to claim 1, wherein the constriction segment possesses a cross-section that is elliptical of major axis that is of constant length.

6. A pogo effect corrector system according to claim 1, wherein the feed pipe portion presents a bend.

7. A pogo effect corrector system according to claim 6, wherein the width of the feed pipe portion his constant in the plane of the bend.

8. A pogo effect corrector system according to claim 1, wherein the rejection passage opens out into the feed pipe portion via at least two diametrically opposite rejection orifices.

9. A pogo effect corrector system according to claim 1, wherein the constriction segment possesses a cross-section that is elliptical and wherein the rejection passage opens out into the feed pipe portion via at least one rejection orifice situated on the minor axis of the ellipse formed by the cross-section of the constriction segment.

10. A pogo effect corrector system according to claim 1, wherein the rejection passage opens out into the feed pipe portion via a plurality of rejection orifices distributed all around the feed pipe portion.

11. A pogo effect corrector system according to claim 1, wherein the rejection passage is constituted by one or more orifices formed through the wall of the feed pipe portion.

12. A rocket engine, including a pogo effect corrector system according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying drawings are diagrammatic and seek above all to illustrate the principles of the invention.

(2) In the drawings, from one figure to another, elements (or portions of an element) that are identical are identified by the same reference signs. In addition, elements (or portions of an element) forming parts of embodiments that are different but having functions that are analogous are identified in the figures by numerical references incremented by 100, 200, etc.

(3) FIG. 1 is a diagram showing a space vehicle including a pogo effect corrector system in accordance with the disclosure.

(4) FIG. 2 is a diagrammatic section view of a first embodiment of a pogo effect corrector system.

(5) FIG. 3 is an axial section view of a second embodiment of a pogo effect corrector system.

(6) FIG. 4 is a view of the second embodiment of the pogo effect corrector system in section on plane IV of FIG. 3.

(7) FIG. 5 is a view of the second embodiment of the pogo effect corrector system in folded section on plane V of FIG. 3.

(8) FIG. 6 is an axial section view of a third embodiment of a pogo effect corrector system.

DETAILED DESCRIPTION OF EMBODIMENT(S)

(9) In order to make the invention more concrete, embodiments of pogo effect corrector systems are described in detail below with reference to the accompanying drawings. It should be recalled that the invention is not limited to these embodiments.

(10) FIG. 1 is a highly diagrammatic view of a space vehicle 1, such as a space launcher stage. The vehicle 1 includes a liquid propellant rocket engine 2. The rocket engine 2 has a propulsion chamber 3 comprising both a combustion chamber and a converging-diverging nozzle, in known manner.

(11) The propulsion chamber 3 is fed with two liquid propellants by two feed systems 4 and 6, each having a respective propellant feed pipe 5 or 7. The first feed system 4 is shown in part only.

(12) The second feed system 6 has a capacitive pogo corrector system 10, abbreviated below to PCS for convenience.

(13) Throughout the present disclosure below, the terms “upstream” and “downstream” should be understood relative to the PCS 10, following the flow direction of the liquid propellant towards the rocket engine 2.

(14) The PCS 10 comprises a hydraulic accumulator 11 and a portion 70 of a feed pipe. The feed pipe portion 70 is configured to be connected upstream to an upstream portion 7m of the feed pipe 7, and downstream to a downstream portion 7v of the feed pipe 7. The flow direction E of the liquid propellant is shown in the figures by an arrow. The upstream portion 7m and the downstream portion 7v are circular in section, for example.

(15) FIG. 2 is a diagram showing a first example of such a PCS 10. In this example, the pipe portion 70 has a bend. All along it possesses a section that is circular, but its diameter varies between its upstream end 70m and its downstream end 70v. More precisely, its upstream and downstream ends 70m and 70v have the same diameter d1 corresponding to the nominal diameter of the pipe portion 70; in contrast, the pipe portion 70 possesses an intermediate constriction portion 82 where the wall 71 of the pipe portion 70 narrows, forming a bottle neck 73, by reducing the diameter of the pipe portion 70. Consequently, the diameter d2 of the constriction segment 82 is less than the nominal diameter d1 of the pipe portion 70 such that the flow section through the pipe portion 70 is reduced in the constriction portion 82.

(16) Nevertheless, it should be observed that the wall 71 of the pipe portion 70 retains a profile that is continuous without any break of slope, even in the constriction segment 82.

(17) Furthermore, the hydraulic accumulator 11 comprises a tank 12 and a gas injector 13 provided in an upper portion 12s of the tank 12, preferably at the top of the tank 12. The lower portion 12i of the tank 12 is connected to the feed pipe portion 70 by at least one take-off passage 14 that, in this example, is in the form of take-off orifices through the wall 71 of the feed pipe portion 70 in a take-off segment 81 situated downstream from the constriction segment 82 and of diameter equal to the nominal diameter d1 of the pipe portion 70. Thus, by means of the take-off passage 14, propellant coming from the pipe portion 70 can penetrate into the lower portion 12i of the tank 12.

(18) In the present disclosure, the “upper” portion 12s of the tank 12 designates the portion of the tank 12 where the gas injected by the injector 13 tends to accumulate, given that its density is lower than the density of the liquid propellant flowing in the pipe 7, and because of the acceleration to which the PCS 10 is subjected while the rocket engine 2 is in operation. Conversely, the “lower” portion 12i of the tank 12 designates the portion of the tank 12 where liquid tends to accumulate because of its greater density, and because of the acceleration to which the PCS 10 is subjected while the rocket engine 2 is in operation.

(19) The hydraulic accumulator 11 also has a rejection passage 20 opening out firstly into the tank 12 at an intermediate level 15 between the upper and lower portions 12s and 12i of the tank 12, and secondly into the feed pipe portion 70 in its constriction segment 82.

(20) More precisely, in this example, the rejection passage 20 is in the form of a duct 21 running along the outside of the wall 71 of the pipe portion 70 and extending between an inlet 22 open in the intermediate portion 15 of the tank 12 and a manifold 23 surrounding the constriction portion 82 of the pipe portion 70, with rejection orifices 24 being formed through the wall 71 of the pipe portion 70 between the constriction segment 82 and the manifold 23, at regular intervals all around the constriction segment 82, where the diameter of the pipe portion 70 is at its minimum.

(21) In a typical example, the liquid propellant flowing in the feed pipe 7 and the feed pipe portion 70 is liquid oxygen (LOx), and the gas injected by the injector 13 is helium (He).

(22) While the rocket engine 2 is in operation, the injector 13 injects gas at a constant rate into the tank 12, thereby creating a volume of gas 31 that accumulates in the upper portion 12s of the tank 12, thus forming an interface 33 between the gas and the liquid propellant 32 present in the lower portion 12i of the tank 12.

(23) Furthermore, as a result of the Venturi effect, the decrease in the flow section of the pipe portion 70 in its constriction segment 82 leads to the liquid propellant accelerating locally and to its pressure decreasing locally. Consequently, the pressure that exists at the rejection orifices 24 is lower than the pressure that exists in the tank 12 at the inlet 22 to the rejection passage 20: suction is therefore generated in the rejection passage 20 so that the excess gas going past the intermediate level 15 of the tank 12 is sucked in and discharged into the pipe portion 70.

(24) The volume of gas 31 can thus be maintained substantially constant in the tank 12. Under such circumstances, it is possible to avoid pogo oscillations appearing by modifying the resonant frequencies of the feed pipe 70, as is well known.

(25) FIGS. 3, 4, and 5 show a second embodiment of a PCS 110. This second embodiment is analogous to the first embodiment in numerous points, and only features that are specific to the second embodiment are therefore described in detail. In this embodiment, the PCS 110 is made as a single piece by additive manufacturing. It comprises a bend pipe portion 170 and a hydraulic accumulator 111 extending over substantially 180° around the pipe portion 170, on the outside of the bend.

(26) In this second embodiment, and as can be seen more clearly in FIG. 4, the constriction section 182 is not formed by reducing the diameter of the pipe portion 170, but by making its wall 171 oval. More precisely, as in the first embodiment, the upstream and downstream ends 170m and 170v, each provided with a fastener flange 172, possess respective circular sections of diameter d1 corresponding to the nominal diameter of the pipe portion 170; in contrast, in the constriction segment 182, the pipe portion 170 possesses a cross-section that is elliptical. The major axis of the ellipse is aligned with the plane of the bend and it conserves a length that is constant and equal to the nominal diameter d1; in contrast, the minor axis b decreases continuously without any break of slope prior to reaching a minimum and then increases until returning once more to the nominal diameter d1 and thus to a cross-section that is circular.

(27) The tank 112, which is C-shaped, is than provided around the pipe portion 170 over about 180°. The upper portion 112s of the tank 112 is provided with a gas injector 113. The lower portion 112i of the tank 112 is connected to the feed pipe portion 170 via a plurality of take-off orifices 114 formed through the wall 171 of the feed pipe portion 170 in the take-off segment 181 situated downstream from the constriction segment 182 and of diameter equal to the nominal diameter d1 of the pipe portion 170.

(28) In this example, the hydraulic accumulator 111 has two diametrically opposite rejection passages 120 opening out firstly into the tank 112 at an intermediate level 115 between the upper and lower portions 112s and 112i of the tank 112, and secondly into the feed pipe portion 170 in its constriction section 182.

(29) More precisely, in this example, each rejection passage 120 is in the form of a duct 121 formed in the wall 171 of the pipe portion 170 and extending between an inlet 122 open at the intermediate level 115 of the tank 112, and a group comprising a plurality of rejection orifices 124, specifically three orifices in alignment, that open out into the constriction segment 182 at the level where the minor axis b of the ellipse is at a minimum.

(30) The operation of this second embodiment of a PCS 110 is analogous to that of the first embodiment.

(31) FIG. 6 shows a third embodiment of a PCS 210. This third embodiment is analogous to the first embodiment in numerous points and only the features specific to this third embodiment are therefore described in detail. In this embodiment, the pipe portion 270 of the PCS 210 is axisymmetric and the hydraulic accumulator 211 surrounds the pipe portion 270 completely over 360°, the tank 212 being separated from the pipe portion 270 by the wall 271 only.

(32) In this embodiment, and in analogous manner to the first embodiment, the flow section in the constriction segment 282 is reduced by narrowing the wall 271 so as to form a bottle neck 273 of nominal diameter d2 that is less than the nominal diameter d1 of the pipe portion 270.

(33) A specific feature of this third embodiment is that the rejection passage 220 is constituted by no more than rejection orifices 224 that are regularly distributed all around the constriction segment 282, passing right through the wall 271 in order to open out into the tank 212 at the intermediate level 215.

(34) Although the present invention is described with reference to specific embodiments, it is clear that modifications and changes may be undertaken on those embodiments without going beyond the general ambit of the invention as defined by the claims. In particular, individual characteristics of the various embodiments shown and/or mentioned may be combined in additional embodiments. Consequently, the description and the drawings should be considered in a sense that is illustrative rather than restrictive.

(35) It is also clear that all of the features described with reference to a method can be transposed, singly or in combination, to a device, and conversely that all of the features described with reference to a device can be transposed, singly or in combination, to a method.