Method for cleaning a gas jet projected by a rocket engine

Abstract

Method for cleaning a gas jet projected by a rocket engine. The invention relates to a method for cleaning a gas jet (J) projected by a rocket engine, comprising at least the passage of the gas jet successively through treatment zones (10; 20) positioned in series in which water is projected onto the gas jet with calibrated nozzle (B1; B2) supply flow rates and water ejection velocity. Figure for the abstract: Fig. 1.

Description

Title of the invention: Method for cleaning a gas jet projected by a rocket engine. Technical field

[0001] The present description relates to a method for purifying a gas jet ejected by a rocket engine by spraying water in order to recover the substances to be eliminated from the jet before its release into the ambient air. The invention is applicable to treating a gas jet emitted from a rocket engine on a test bench or produced during the launch of a space launcher. Previous technique

[0002] Rocket engine propellants generate a gas jet exiting the exhaust stream that includes acidic compounds, such as hydrogen chloride (HCl), reducing gases, such as carbon monoxide (CO) or dihydrogen (H2), as well as dust such as alumina dust or other metal oxides. It is desirable to purify the gas jet by removing harmful, or potentially harmful, species in order to prevent their release into the ambient air.

[0003] The prior art offers methods for capturing hydrogen chloride, for example, which are based on the use of filters with the addition of basic compounds, or packed scrubbing columns. However, these processes require a limited inlet velocity, generally less than about 10 m / s, which is incompatible with the high ejection velocities encountered at the propellant outlet, which are at least about 100 m / s. Furthermore, these processes introduce significant pressure losses that disrupt the upstream gas jet flow and therefore cannot be used for this reason as well.

[0004] It is therefore necessary to provide a suitable solution for the treatment of a gas jet from a rocket engine which at least allows the elimination of acidic compounds and dust and which is in particular compatible with the high speed of the gas jet and does not disturb the upstream flow. Description of the invention

[0005] The present invention relates to a method for cleaning a gas jet projected by a rocket engine, comprising at least: - the passage of the gas jet successively through a first deceleration and cooling zone having an inlet spaced apart from an ejection vent of the rocket engine, then through a second zone for the recovery of acidic compounds and dust having an inlet connected to an outlet of the first zone, a water spray being carried out on the gas jet from first nozzles in the first zone and from second nozzles in the second zone, each of the first and second zones extending over a length between 5D and 15D where D designates the outlet diameter of the ejection stream, a first water flow of between 8Dg / 3 and 16Dg / 3 supplying all the first nozzles and being distributed among them, and a second water flow of between 4Dg / 3 and 8Dg / 3 supplying all the second nozzles and being distributed among them, the first and second flow rates being expressed in L / s and Dg designating the flow rate of the gas jet at the outlet of the ejection stream expressed in kg / s, and the ejection velocity of the water at the outlet of the first and second nozzles being at least 15 m / s, the water projected onto the gas jet being recovered in a collection volume located below the first and second zones.

[0006] The invention makes it possible to purify the high-velocity projected gas jet by first drastically reducing its temperature and velocity in the first zone so as to allow the recovery of acidic compounds and dust in the water projected into the second zone. The water flow rate supplying the nozzles of each zone is specifically adapted to the objective sought in each zone and is a function of the gas flow rate Dg to be treated. Furthermore, the water is projected at a high velocity to ensure its presence at the core of the jet and to obtain effective treatment. The first and second zones have dimensions adapted to the characteristic dimensions of the gas jet while maintaining a relatively compact design.

[0007] Furthermore, the technique according to the invention does not lead to pressure losses disrupting the upstream flow because the water spraying is carried out at a distance from the ejection stream. This spacing also allows ambient air to be drawn in by the jet, thus also contributing to its cooling and slowing down.

[0008] The invention thus makes it possible to purify a gas jet from a rocket engine projected at high speed without disturbing the flow at the level of the ejection stream, and in particular by enabling the capture of acidic compounds and dust by the projected water. These elements are collected in a collection volume, thus preventing their release into the ambient air.

[0009] In one embodiment, the inlet of the first zone is spaced from the ejection vein by a distance between D / 4 and 2D, and the passage cross-section of the first zone is at most equal to nine times the passage cross-section at the outlet of the ejection vein.

[0010] Such a configuration further reduces the risk of an impact on the upstream flow while allowing the admission of a controlled amount of surrounding air which helps to cool the gas jet while ensuring effective treatment.

[0011] In one embodiment, the first and second zones each have a length between 8D and 12D.

[0012] Such a feature further improves the compromise between treatment efficiency and installation compactness.

[0013] In one embodiment, the ejection velocity of the water at the outlet of the first and second nozzles is at least 18 m / s.

[0014] Such a feature helps to further improve the effectiveness of the treatment.

[0015] In one embodiment, water is projected onto the gas jet by the first and second nozzles in the form of droplets having a volumetric median diameter between 200 pm and 400 pm.

[0016] Such a feature optimizes the microscopic exchange surface between the water and the jet, and further improves the efficiency of the treatment.

[0017] In one embodiment, the passage section of the second zone is greater than the passage section of the first zone.

[0018] Such a feature makes it possible to further reduce the speed of the gas jet at the entrance of the second zone, thus further improving the efficiency of the treatment.

[0019] In one embodiment, the first and second zones can be moved relative to each other and each have a modular structure formed of a plurality of juxtaposed segments that are removable relative to each other.

[0020] Such a feature makes it possible to adapt the treatment to the rocket engine in question by allowing adjustment of the length and possibly the position of the first and second zones.

[0021] In one embodiment, the elimination of reducing gases from the gas jet is carried out by post-combustion upstream of the first zone.

[0022] Such a characteristic advantageously allows the gas treatment to be completed by removing gases such as carbon monoxide (CO) or dihydrogen (H2).

[0023] In one embodiment, the removal of aerosols (e.g. water, acid, dust) carried by the gas jet is carried out in a demister downstream of the second zone.

[0024] In one embodiment, the water circulates in a closed loop between the collection volume and the first and second nozzles during the passage of the gas jet.

[0025] Such a feature advantageously reduces water consumption and allows for water autonomy throughout the duration of the shot, which typically lasts a few minutes.

[0026] In one embodiment, the gas jet is projected by a rocket engine on a test bench.

[0027] Alternatively, the gas jet is projected by a rocket engine of a space launcher during takeoff. Brief description of the drawings

[0028] [Fig.1] Fig.1 represents, schematically and partially, the implementation of an example of a gas jet sanitation process according to the invention.

[0029] [Fig.2] Fig.2 represents, schematically and partially, a perspective view of the first and second zones implemented in the example of [Fig.1]. Description of the implementation methods

[0030] The invention is now described by means of figures, which are present for descriptive purposes to illustrate certain embodiments of the invention and which should not be interpreted as limiting the latter.

[0031] Figure 1 shows an example of an installation 1 adapted for the treatment of a gaseous jet J projected by a rocket engine studied on a test bench. The jet J is projected through an ejection stream V from the rocket engine and is then treated by the installation 1, which is located in the extension of the stream V.

[0032] Installation 1 generally comprises several modules arranged in series, that is, in line with one another. The jet J passes successively through these modules. Installation 1 extends along a longitudinal axis X, along which the modules are positioned. The modules may be located on the axis of the stream V, or alternatively, offset from the stream.

[0033] Installation 1 is modular, meaning that the different modules can be moved relative to one another and, for some, lengthened or shortened. In particular, the first 10 and the second 20 zones are each formed of a plurality of juxtaposed segments 11, 21 that are removable relative to one another. It is thus possible to add one or more segments 11, 21 to lengthen zone 10, 20 or to remove some to shorten it, depending on the rocket engine in question. The segments 11, 21 are made of a material suitable for withstanding the conditions encountered during the passage of the J jet, and are, for example, made of concrete.

[0034] The J jet comprises acidic compounds, such as hydrogen chloride (HCl), at least one reducing gas, such as carbon monoxide (CO), dihydrogen (H2), or a mixture of these two compounds, and dust, such as alumina dust or other metal oxides. The nature of the dust present depends on the rocket engine. The treatment proposed within the scope of the invention aims, at a minimum, to capture the acidic compounds present as well as any dust that may be present.

[0035] Installation 1 is located above a collection volume VC which recovers the water projected into the first 10 and second 20 zones, which is laden with the compounds to be removed from the gas jet. More specifically, in the illustrated example, the first 10 and second 20 zones are located above a collection ramp RC which is sloped to guide the recovered water towards a collection basin BC.

[0036] The following section describes, in more detail, the different modules of the illustrated installation example 1, namely in this order from vein V: the PC afterburner zone, the first zone 10, the second zone 20 and the DE devesiculator.

[0037] In the following and unless otherwise stated, the terms "upstream" and "downstream" are understood in relation to the flow direction of jet J.

[0038] Post-combustion of reducing gases

[0039] The illustrated installation example 1 includes an afterburner PC zone located directly at the outlet of jet V. The PC zone includes an ignition source that oxidizes the reducing gases of jet J in the presence of ambient oxygen. The ignition source is a device known per se, and one can, for example, use: a combustible gas torch, for example, liquefied petroleum gas (pilot flame burner), hot wires, or a pyrotechnic device for projecting incandescent particles (known in English as "Hydrogen Bum Off Igniters"). A person skilled in the art will choose the appropriate ignition source based on the velocity of jet J, the concentration of reducing gases, and the safety constraints specific to the intended application.

[0040] The PC zone is optional and may be omitted if the concentration of dihydrogen and carbon monoxide in the jet J is lower than the lower explosive limit (LEL). In this latter case, the jet J may not undergo any treatment before entering the first zone 10, which will now be described.

[0041] First zone: slowing and cooling of the jet

[0042] An input 101 of the first zone 10 is in communication with the vein V, in this case with the PC zone in the illustrated example.

[0043] The role of the first zone 10 is to lower the speed and temperature of the jet J so as to allow for effective recovery of acidic compounds and dust in the second zone 20 downstream. This slowing is achieved by using a high flow rate of projected water, primarily through momentum exchange. The water is thus projected from first nozzles B1 into the first zone 10. The water is projected from the first nozzles B1 transversely to the flow direction of the jet J.

[0044] It should be noted that the roles of the first 10 and second 20 zones are not mutually exclusive, that is to say, one does not depart from the scope of the invention if a slowdown and a J jet cooling also occurs in the second zone 20, or if the water used in the first zone 10 becomes loaded with acidic compounds and dust.

[0045] The entrance of the first zone 10 is spaced from the vein V by a non-zero distance DI, for example, between D / 4 and 2D. The distance DI can be between D / 2 and 2D, for example, between D and 2D. The first zone 10 has a length L10 between 5D and 15D, for example, between 5D and 12D or between 8D and 15D or between 8D and 12D.

[0046] The cross-section of the first zone 10 can be at least equal to the cross-section at the exit of the vein V, and for example at most equal to nine times the cross-section at the exit of the vein V. The diameter DU of the first zone 10, corresponding to its largest transverse dimension measured perpendicular to the axis X, can be between D and 3D, for example between 1.5D and 2.5D.

[0047] By way of illustration, the jet J projected by the vein V has a velocity of at least 100 m / s, possibly even reaching supersonic speed. This velocity can generally range from 100 m / s to 1000 m / s. Passing through the first zone 10 typically reduces the velocity of the jet J to a value less than or equal to 30 m / s. The flow rate of the gas jet exiting the vein V is also very high, typically at least 100 kg / s. The jet J arrives in the first zone 10 at a temperature greater than or equal to 200°C, for example, greater than or equal to 800°C. After passing through the first zone 10, the temperature of the jet J can be lowered to a value less than or equal to 200°C.

[0048] In view of the high flow rate and velocity values ​​encountered for the treatment of the J jet, it is necessary to calibrate the flow rate of water supplying the first nozzles B1 as well as the ejection velocity of the water through them to particular values ​​adapted to the kinetics and the mass of gas to be treated per unit of time.

[0049] Thus, an initial water flow rate between 8Dg / 3 and 16Dg / 3, for example between 8Dg / 3 and 14Dg / 3, supplies all the first nozzles B1 and is distributed among them during the passage of jet J. In the preceding diagram, the initial flow rate is expressed in L / s and Dg denotes the flow rate of the gas jet exiting the vein V, expressed in kg / s. The initial flow rate can be distributed uniformly (equally) among the first nozzles Bl.

[0050] The first nozzles Bl are distributed along the first zone 10. More precisely, the first zone 10 shown comprises several sets of first nozzles Bl, each located at different positions X1B1, X2B1, and X3B1 along the first zone 10 (or the X-axis). The positions X1B1, X2B1, and X3B1 can be regularly spaced along the X-axis as shown, or alternatively, the spacing between two consecutive positions can be variable. Each set, located at a given position along the first zone 10, includes several first nozzles B1 distributed circumferentially around the X axis.

[0051] The ejection velocity of the water at the outlet of the first nozzles B1 is greater than or equal to 15 m / s, for example greater than or equal to 18 m / s. This velocity can be between 15 m / s and 25 m / s or between 15 m / s and 22 m / s or between 18 m / s and 25 m / s or between 18 m / s and 22 m / s.

[0052] The water projected by the first nozzles B1 may or may not be alkaline. The water projected by the first nozzles B1 may be in the form of droplets having a volumetric median diameter between 200 pm and 400 pm, for example between 250 pm and 400 pm or between 250 pm and 350 pm.

[0053] The first zone 10 includes an orifice 105 for the positioning of various sensors.

[0054] The slowed and cooled jet J, having passed through the first zone 10, then enters the second zone 20, which will now be described.

[0055] Second zone: recovery of acidic compounds and dust

[0056] An input 201 of the second zone 20 is in communication with an output 103 of the first zone 10. The second zone 20 is downstream of the first zone 10. The second zone 20 can be located in the axis of the first zone 10 and of the vein V, or be slightly off-axis.

[0057] The role of the second zone 20 is to capture acidic compounds and dust in the projected water. The water is projected by second nozzles B2 into the second zone 20. The water is projected by the second nozzles B2 transversely to the flow direction of jet J.

[0058] The second zone 20 has a length L20 between 5D and 15D, for example between 5D and 12D or between 8D and 15D or between 8D and 12D. The length L20 may be the same as or different from the length L10. The cross-sectional area of ​​the second zone 20 may, as illustrated, be larger than the cross-sectional area of ​​the first zone 10. The diameter DI2 of the second zone 20, corresponding to its largest transverse dimension measured perpendicular to the X-axis, may be between 2D and 4D, for example between 2.5D and 3.5D.

[0059] The water flow rate supplying the second nozzles B2 and the ejection speed of the water through them is calibrated to particular values ​​adapted to the kinetics and the mass of gas to be treated per unit of time.

[0060] Thus, a second water flow rate between 4Dg / 3 and 8Dg / 3, for example between 4Dg / 3 and 7Dg / 3, supplies all the second nozzles B2 and is distributed among them during the passage of jet J. As indicated above, the second flow rate is expressed in L / s and Dg designates the flow rate of the gas jet exiting vein V expressed in kg / s. The second flow rate can be distributed evenly (equitably) between the second B2 nozzles.

[0061] The second nozzles B2 are distributed along the second zone 20. More precisely, the illustrated second zone 20 comprises several sets of second nozzles B2, each located at different positions X1B2, X2B2, and X3B2 along the second zone 20 (or the X-axis). The positions X1B2, X2B2, and X3B2 may be regularly spaced along the X-axis as illustrated, or alternatively, the spacing between two consecutive positions may be variable. Each set, located at a given position along the second zone 20, comprises several second nozzles B2 distributed circumferentially around the X-axis.

[0062] The ejection velocity of the water at the outlet of the second nozzles B2 is greater than or equal to 15 m / s, for example greater than or equal to 18 m / s. This velocity can be between 15 m / s and 25 m / s or between 15 m / s and 22 m / s or between 18 m / s and 25 m / s or between 18 m / s and 22 m / s.

[0063] The water projected by the second nozzles B2 is advantageously alkaline, i.e., having a pH greater than 7, so as to neutralize the acidic compounds recovered from jet J. The water projected by the second nozzles B2 can be sodium hydroxide water, i.e., water to which sodium hydroxide (NaOH) has been added. The addition of hydroxide ions (OH⁻) to the water to obtain alkaline water can be carried out using known techniques, for example, by employing metering pumps or Venturi systems. The concentration of hydroxide ions will be adapted to the composition of the gas to be treated.

[0064] According to one variant, the water projected by the second nozzles B2 is not alkaline and basic treatment can be carried out at the end of the process, in the collection basin BC for example.

[0065] The water projected by the second nozzles B2 can be in the form of droplets having a median volumetric diameter between 200 pm and 400 pm, for example between 250 pm and 400 pm or between 250 pm and 350 pm.

[0066] In the first 10 and second 20 zones, the water falls onto the RC ramp and is then directed by gravity towards the BC basin. The illustrated example shows a PC recirculation pump located in the BC basin, which advantageously allows the water to circulate in a closed loop between the BC basin and the first B1 and second B2 nozzles (according to the circulation arrows CE). The supply flow rates to the first B1 and second B2 nozzles are controlled by a control unit (not shown).

[0067] The second zone 20 includes an orifice 205 for the positioning of various sensors.

[0068] Design of the first and second zones

[0069] The flow rate value Dg of the jet J to be treated allows the respective water flow rates with which the first B1 and second nozzles B2 must be supplied to be deduced using the formulas described above. The nozzles B1 and B2 are then selected, based on the information provided by the supplier, so as to meet the desired ejection velocity criterion, and possibly the size of the projected droplets.

[0070] The number of B1 or B2 nozzles to be used in a given area 10 or 20 is then obtained, for the nozzles thus chosen, by dividing the supply water flow rate by the unit flow rate at the nozzle inlet which corresponds to information indicated by the supplier.

[0071] The nozzles B1 or B2 can then advantageously be distributed over the area considered 10 or 20 so as to produce a substantially homogeneous flow of water.

[0072] Generally, the first B1 and second B2 nozzles can be solid cone nozzles. For example, nozzles marketed under reference 491.146.1Y. AM or 491.006.1Y. AK by Lechler can be used.

[0073] According to a particular embodiment, the jet J can have a flow rate Dg at the outlet of vein V between 50 kg / s and 150 kg / s with: - an initial water flow rate supplying the first B1 nozzles of between 100 L / s and 800 L / s, for example between 135 L / s and 800 L / s, and a number of first B1 nozzles of between 20 and 100, and - a second water flow supplying the second B2 nozzles between 50 L / s and 400 L / s, for example between 70 L / s and 400 L / s, and a number of second B2 nozzles between 20 and 100.

[0074] Devesiculator

[0075] The illustrated installation 1 includes a DE demister, the presence of which is optional but preferable for limiting aerosol emissions. The DE demister condenses the residual water carried by the gas jet exiting the second zone 20. It corresponds to a device known per se. For example, a demister marketed under the reference B-GON® by the company KIMRE can be used.

[0076] The devesiculator DE can be spaced from the second zone 20 by a distance D2 between 0.5D and 1.5D.

[0077] Following the process, the collected water can be treated directly at the BC basin and may include pH adjustment (addition of hydrochloric acid or sodium hydroxide) and dust filtration. Further water treatment employs techniques that are known per se.

[0078] The example described relates to zones 10, 20 in the form of conduits or ducts into which water is projected. The installation may have a more open structure, each zone 10, 20 being for example formed by a succession of water injection tori spaced apart from each other.

[0079] The example described relates to the case of cleaning a gas jet projected by a rocket engine on a test bench. In this case, the rocket engine and zones 10 and 20 can, as illustrated, be arranged horizontally. As mentioned above, the invention can, according to a variant not illustrated, be used to clean a gas jet projected by a space launcher rocket engine during the liftoff phase. In this latter case, the rocket engine and the first and second zones can be arranged vertically, with the collection volume below this assembly. The details described above remain applicable to this case.

[0080] The illustrated example includes three nozzle sections on each of the first 10 and second 20 zones, but a person skilled in the art will recognize that this number may vary depending on the application.

[0081] The expression "between ... and ..." should be understood as including the bounds.

Claims

Demands

1. A method for cleaning a gaseous jet (J) projected by a rocket engine, comprising at least: - the passage of the gaseous jet successively through a first slowing and cooling zone (10) having an inlet (101) separated from an ejection stream (V) of the rocket engine, then through a second zone (20) for recovering acidic compounds and dust having an inlet (201) in communication with an outlet (103) of the first zone, a water projection being carried out on the gaseous jet from first nozzles (B1) in the first zone and from second nozzles (B2) in the second zone, each of the first and second zones extending over a length (L10;L20) between 5D and 15D where D designates the outlet diameter of the ejection stream, a first water flow rate between 8Dg / 3 and 16Dg / 3 supplying all the first nozzles and being distributed among them, and a second water flow rate between 4Dg / 3 and 8Dg / 3 supplying all the second nozzles and being distributed among them, the first and second flow rates being expressed in L / s and Dg designating the flow rate of the gas jet at the outlet of the ejection stream expressed in kg / s, and the ejection velocity of the water at the outlet of the first and second nozzles being at least 15 m / s, the water projected onto the gas jet being recovered in a collection volume (VC) located below the first and second zones.;

2. A method according to claim 1, wherein the inlet (101) of the first zone (10) is spaced from the ejection vein (V) by a distance (Dl) between D / 4 and 2D, and the passage cross-section of the first zone is at most equal to nine times the passage cross-section at the outlet of the ejection vein.

3. A method according to claim 1 or 2, wherein the first (10) and second (20) zones each have a length (L10; L20) between 8D and 12D.

4. A method according to any one of claims 1 to 3, wherein the ejection velocity of the water exiting the first (B1) and second (B2) nozzles is at least 18 m / s.

5. A method according to any one of claims 1 to 4, wherein water is projected onto the gaseous jet (J) by the first (Bl)

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12. and second (B2) nozzles in the form of droplets having a volumetric median diameter between 200 µm and 400 µm. Method according to any one of claims 1 to 5, wherein the passage area of ​​the second zone (20) is greater than the passage area of ​​the first zone (10). A method according to any one of claims 1 to 6, wherein the first (10) and second (20) zones can be moved relative to each other and each have a modular structure formed of a plurality of segments (11; 21) juxtaposed and removable relative to each other. A method according to any one of claims 1 to 7, wherein the removal of reducing gases from the gas jet is carried out by post-combustion upstream of the first zone (10). A method according to any one of claims 1 to 8, wherein the removal of aerosols carried by the gas jet is carried out in a demister (DE) downstream of the second zone (20). Method according to any one of claims 1 to 9, wherein the water circulates in a closed loop between the collection volume (VC) and the first (B1) and second (B2) nozzles during the passage of the gaseous jet (J). A method according to any one of claims 1 to 10, wherein the gas jet is projected by a rocket engine on a test bench. A method according to any one of claims 1 to 10, wherein the gas jet is projected by a rocket engine of a space launcher during the takeoff phase.

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