Method for cleaning a gas jet ejected by a rocket engine

Abstract

The invention relates to a method for cleaning a gas jet (J) ejected by a rocket engine, comprising at least passing the gas jet successively through treatment zones (10; 20) positioned in series in which water is sprayed onto the gas jet, the flow rates of water feeding the nozzles (B1; B2) and the water ejection speed being calibrated.

Description

Description Title of the invention: METHOD FOR SANITIZING A GAS JET PROJECTED BY A ROCKET ENGINE Technical Field

[0001] This disclosure relates to a method for cleaning a gas jet projected by a rocket engine by spraying water so as to recover the species to be eliminated from the jet before its release into the ambient air. The invention applies to treating a gas jet from a rocket engine on a test bench or produced during the take-off of a space launcher. Prior art

[0002] Rocket engine thrusters generate a gas jet at the exhaust outlet that includes acidic compounds, such as hydrogen chloride (HCl), reducing gases, such as carbon monoxide (CO) or dihydrogen (H2), and dust such as alumina dust or other metal oxides. It is desirable to clean the gas jet by removing harmful or potentially harmful species, so as to avoid their release into the ambient air.

[0003] The state of the art proposes 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 methods require a limited velocity at the device inlet, generally less than about 10 m / s, which is incompatible with the high ejection velocities encountered at the propellant outlet which amount to at least about 100 m / s. In addition, these methods introduce significant pressure drops which disturb the flow of the gas jet upstream and therefore cannot be retained for this reason also.

[0004] It is therefore necessary to provide a solution suitable for the treatment of a gas jet from a rocket engine which allows at least the elimination of acid compounds and dust and which is in particular compatible with the high speed of the gas jet and does not disturb the upstream flow. Statement 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 slowing down zone and cooling having an inlet spaced from an ejection vein of the rocket engine, then through a second zone for recovering acid compounds and dust having an inlet in communication with an outlet of the first zone, a projection of water 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 of between 5D and 15D where D designates the outlet diameter of the ejection vein, a first water flow rate of between 8Dg / 3 and 16Dg / 3 supplying all of the first nozzles and being distributed between them, and a second water flow rate of between 4Dg / 3 and 8Dg / 3 supplying all of the second nozzles and being distributed between 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 vein expressed in kg / s,and the speed of ejection 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 clean the gas jet projected at high speed by first drastically lowering its temperature and speed in the first zone so as to allow the recovery of acid compounds and dust in the water projected in the second zone. The flow rate of water supplying the nozzles of each of the zones is specially adapted to the objective sought in each of the zones and is a function of the flow rate Dg of gas to be treated. Furthermore, the water is projected at a high speed to guarantee its presence in the heart of the jet and obtain effective treatment. The first and second zones have dimensions adapted to the characteristic dimensions of the gas jet while maintaining a relatively compact architecture.

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

[0008] The invention thus makes it possible to clean a gas jet from a rocket engine launched at high speed without disturbing the flow at the ejection vein, and in particular by allowing the capture of acid compounds and dust by the projected water. These elements are recovered in a collection volume, thus avoiding their release into the ambient air.

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

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

[0011] In an exemplary 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 an exemplary embodiment, the ejection speed 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 an exemplary embodiment, the water is projected onto the gas jet by the first and second nozzles in the form of droplets having a volumetric median diameter of 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 treatment efficiency.

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

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

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

[0020] Such a feature makes it possible to best adapt the treatment to the rocket engine considered by making it possible to adjust the length and possibly the position of the first and second zones.

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

[0022] Such a feature advantageously makes it possible to complete the gas treatment carried out by eliminating gases such as carbon monoxide (CO) or dihydrogen (H2).

[0023] In an exemplary embodiment, elimination of aerosols (for example water, acid, dust) carried by the gas jet is carried out in a mist eliminator downstream of the second zone.

[0024] In an exemplary 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 makes it possible to reduce water consumption and to be self-sufficient in water for the entire duration of the shot, which typically lasts a few minutes.

[0026] In one exemplary 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 [Fig. 1] Figure 1 represents, schematically and partially, the implementation of an example of a method for cleaning a gas jet according to the invention. [Fig. 2] Figure 2 represents, schematically and partially, a perspective view of the first and second zones implemented in the example of Figure 1. Description of the embodiments

[0028] The invention is now described by means of figures, present for descriptive purposes to illustrate certain embodiments of the invention and which should not be interpreted as limiting the latter.

[0029] Figure 1 represents an example of installation 1 adapted to the sanitation of a gaseous jet J projected by a rocket engine studied on a test bench. The jet J is projected through an ejection vein V of the rocket engine and is then treated by installation 1 which is located in the extension of vein V.

[0030] Installation 1 generally comprises different modules located in series, i.e. in the extension of each other. Jet J passes successively through these different modules. Installation 1 extends along a longitudinal axis X along which the different modules are positioned. The different modules can be located in the axis of vein V, or alternatively be offset from the vein.

[0031] The installation 1 is modular, that is to say that the different modules can be moved relative to each other and, for some, be extended or shortened. In particular, the first 10 and the second 20 zones are each formed of a plurality of juxtaposed segments 11, 21 removable from each other. It is thus possible to add one or more segments 11, 21 to lengthen the zone 10, 20 or to remove some to shorten it depending on the rocket engine considered. The segments 11, 21 are formed from a material capable of withstanding the conditions encountered during the passage of the jet J, and are for example made of concrete.

[0032] 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 framework of the invention aims at least to capture the acidic compounds present as well as any dust that may be present.

[0033] The installation 1 is located above a collection volume VC which makes it possible to recover the water projected into the first 10 and second 20 zones which is loaded with the compounds to be eliminated from the gas jet. More precisely in the example illustrated, the first 10 and second 20 zones are located above a collection ramp RC which is sloping so as to guide the recovered water towards a collection basin BC.

[0034] The following describes, in more detail, the different modules of the illustrated installation example 1, namely in this order from vein V: the post-combustion PC zone, the first zone 10, the second zone 20 and the DE mist eliminator.

[0035] In the following and unless otherwise stated, the terms “upstream” and “downstream” refer to the flow direction of jet J.

[0036] Post-combustion of reducing gases

[0037] The illustrated installation example 1 comprises a post-combustion zone PC located directly at the outlet of vein V. The zone PC comprises an ignition source which makes it possible to oxidize the reducing gases of jet J in the presence of oxygen from the ambient air. The ignition source corresponds to a device known per se, and it is possible, for example, to use: a combustible gas torch, for example liquefied petroleum gas (pilot flame burner), hot wires or a pyrotechnic device for projecting incandescent particles (referred to in English as "Hydrogen Burn Off Igniters"). The person skilled in the art will choose the appropriate ignition source depending on the speed of jet J, the concentration of reducing gases as well as the safety constraints specific to the intended application.

[0038] The PC zone is optional and may be omitted if the concentration of hydrogen and carbon monoxide in the J jet is lower than the lower explosive limit (LEL). In the latter case, the J jet may not undergo any treatment before entering the first zone 10 which will now be described.

[0039] First zone: slowing down and cooling the jet

[0040] An input 101 of the first zone 10 is in communication with the vein V, in this case with the zone PC in the illustrated example.

[0041] The role of the first zone 10 is to lower the speed and temperature of the jet J so as to allow effective treatment for recovering acid compounds and dust in the second zone 20 downstream. The slowing down is produced by the use of a high flow rate of projected water mainly ensuring slowing down by exchange of momentum. The water is thus projected by first nozzles B1 into the first zone 10. The water is projected by the first nozzles B1 transversely to the flow direction of the jet J.

[0042] It will be noted that the roles of the first 10 and second 20 zones are not exclusive, that is to say that it does not go beyond the scope of the invention if a slowing down and cooling of the jet J also occurs in the second zone 20, or if the water used in the first zone 10 becomes loaded with acid compounds and dust.

[0043] The entrance to 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 may 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.

[0044] The passage section of the first zone 10 may be at least equal to the passage section at the outlet of the vein V, and for example at most equal to nine times the passage section at the outlet of the vein V. The diameter DI1 of the first zone 10, corresponding to its largest transverse dimension measured perpendicular to the axis X, may be between D and 3D, for example between 1.5D and 2.5D.

[0045] By way of illustration, the jet J projected by the vein V has a speed of at least 100 m / s and may even have a supersonic speed. This speed can generally be between 100 m / s and 1000 m / s. Passing through the first zone 10 typically makes it possible to reduce the speed of the jet J to a value less than or equal to 30 m / s. The flow rate of the gas jet at the outlet of 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.

[0046] In view of the high flow rate and speed values ​​encountered for the treatment of jet J, it is necessary to calibrate the water flow rate supplying the first nozzles B1 as well as the speed of ejection of water through them at particular values ​​adapted to the kinetics and mass of gas to be treated per unit of time.

[0047] Thus, a first water flow rate of between 8Dg / 3 and 16Dg / 3, for example between 8Dg / 3 and 14Dg / 3, supplies all of the first nozzles B1 and is distributed between them when jet J passes. In the previous frame, the first flow rate is expressed in L / s and Dg denotes the flow rate of the gas jet at the outlet of vein V expressed in kg / s. The first flow rate can be distributed uniformly (equitly) between the first nozzles Bl.

[0048] The first nozzles Bl are distributed along the first zone 10. More specifically, the illustrated first zone 10 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 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 first zone 10, comprises several first nozzles Bl distributed circumferentially around the X axis.

[0049] The water ejection speed at the outlet of the first nozzles Bl is greater than or equal to 15 m / s, for example greater than or equal to 18 m / s. This speed 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.

[0050] The water projected by the first nozzles Bl may or may not be alkaline. The water projected by the first nozzles Bl may be in the form of droplets which may have a volumetric median diameter of between 200 pm and 400 pm, for example of between 250 pm and 400 pm or of between 250 pm and 350 pm.

[0051] The first zone 10 comprises an orifice 105 for the positioning of various sensors.

[0052] The slowed and cooled jet J having passed through the first zone 10 then enters the second zone 20 which will now be described.

[0053] Second zone: recovery of acid compounds and dust

[0054] An inlet 201 of the second zone 20 is in communication with an outlet 103 of the first zone 10. The second zone 20 is downstream of the first zone 10. The second zone 20 may be located in the axis of the first zone 10 and of the vein V, or be slightly offset.

[0055] The role of the second zone 20 is to capture acid compounds and dust in the projected water. The water is projected by second nozzles B2 in the second zone 20. The water is projected by the second nozzles B2 transversely to the flow direction of the jet J.

[0056] The second zone 20 has a length L20 of 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 identical to or different from the length L10. The passage section of the second zone 20 may, as illustrated, be greater than the passage section 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.

[0057] The flow rate of water supplying the second nozzles B2 as well as the speed of ejection of the water through them is calibrated to specific values ​​adapted to the kinetics and the mass of gas to be treated per unit of time.

[0058] Thus, a second water flow rate of between 4Dg / 3 and 8Dg / 3, for example between 4Dg / 3 and 7Dg / 3, feeds all of the second nozzles B2 and is distributed between them when jet J passes. As indicated above, the second flow rate is expressed in L / s and Dg denotes the flow rate of the gas jet at the outlet of vein V expressed in kg / s. The second flow rate can be distributed uniformly (equitly) between the second nozzles B2.

[0059] The second nozzles B2 are distributed along the second zone 20. More specifically, 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.

[0060] The water ejection speed 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 speed 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.

[0061] 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 the jet J. The water projected by the second nozzles B2 may be sodium water, i.e. water with added sodium hydroxide (NaOH). The addition of hydroxide ions (OH') to the water to obtain alkaline water may be carried out using known techniques, for example by the use of metering pumps or Venturi systems. The concentration of hydroxide ions will be adapted to the composition of the gas to be treated.

[0062] According to a 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.

[0063] The water projected by the second nozzles B2 may be in the form of droplets which may have a volumetric median diameter of between 200 pm and 400 pm, for example of between 250 pm and 400 pm or between 250 pm and 350 pm.

[0064] In the first 10 and second 20 zones, the water falls onto the ramp RC and is then directed by gravity towards the basin BC. The example illustrated shows a recirculation pump PC present in the basin BC which advantageously allows the water to circulate in a closed loop between the basin BC and the first B1 and second B2 nozzles (according to the circulation arrows CE). The feed flow rates of the first B1 and second B2 nozzles are controlled by a control unit (not shown).

[0065] The second zone 20 includes an orifice 205 for the positioning of various sensors.

[0066] Design of the first and second zones

[0067] The flow rate value Dg of the jet J to be treated makes it possible to deduce, using the formulas described above, the respective water flow rates with which the first B1 and second B2 nozzles must be supplied. The nozzles B1 and B2 are then chosen, based on the information provided by the supplier, so as to present the desired ejection speed criterion, and possibly the size of the projected drops.

[0068] The number of nozzles B1 or B2 to be used in a given zone 10 or 20 is then obtained, for the nozzles thus chosen, by dividing the feed water flow rate by the unit flow rate at the nozzle inlet which corresponds to information indicated by the supplier.

[0069] The nozzles B1 or B2 can then advantageously be distributed over the zone considered 10 or 20 so as to produce a substantially homogeneous flow of water.

[0070] Generally speaking, the first B1 and second B2 nozzles can be full cone nozzles. For example, nozzles marketed under the reference 491.146.1Y.AM or 491.006.1Y.AK by the company Lechler can be used.

[0071] According to a particular embodiment, the jet J can have a flow rate Dg at the outlet of vein V of between 50 kg / s and 150 kg / s with: - a first flow rate of water supplying the first nozzles B1 of between 100 L / s and 800 L / s, for example of between 135 L / s and 800 L / s, and a number of first nozzles B1 of between 20 and 100, and - a second water flow rate supplying the second nozzles B2 of between 50 L / s and 400 L / s, for example of between 70 L / s and 400 L / s, and a number of second nozzles B2 of between 20 and 100.

[0072] Mist eliminator

[0073] The illustrated installation 1 includes a DE mist eliminator, the presence of which is optional but remains preferential in order to limit aerosol emissions. The DE mist eliminator makes it possible to condense the residual water entrained by the gas jet leaving the second zone 20. It corresponds to a device known per se. For example, a mist eliminator marketed under the reference B-GON® by the company KIMRE can be used.

[0074] The demister DE may be spaced from the second zone 20 by a distance D2 of between 0.5D and 1.5D.

[0075] At the end of 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. Subsequent water treatment uses techniques that are known per se.

[0076] The example described concerns zones 10, 20 in the form of conduits or flues into which the 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 from each other.

[0077] The example described concerns 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 distributed horizontally. As indicated above, the invention can, according to a variant not illustrated, be used to clean a gas jet projected by a rocket engine of a space launcher during takeoff. In the latter case, the rocket engine and the first and second zones can be distributed vertically, with the collection volume below this assembly. The details described above remain applicable to this case.

[0078] The illustrated example includes three nozzle sections on each of the first 10 and second 20 zones but the skilled person will recognize that this number may vary depending on the application.

[0079] The expression "between ... and ..." must be understood as including the limits.

Claims

Claims

1. Method for cleaning a gas jet (J) projected by a rocket engine, comprising at least: - the passage of the gas jet successively through a first zone (10) for slowing down and cooling having an inlet (101) spaced from an ejection vein (V) of the rocket engine, then through a second zone (20) for recovering acid compounds and dust having an inlet (201) in communication with an outlet (103) of the first zone, a projection of water being carried out on the gas 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 denotes the outlet diameter of the ejection vein, a first water flow rate between 8Dg / 3 and 16Dg / 3 supplying all of the first nozzles and being distributed between them, and a second water flow rate between 4Dg / 3 and 8Dg / 3 supplying all of the second nozzles and being distributed between them, the first and second flow rates being expressed in L / s and Dg denoting the flow rate of the gas jet at the outlet of the ejection vein expressed in kg / s, and the ejection speed 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. Method according to claim 1, in which 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 section of the first zone is at most equal to nine times the passage 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) of between 8D and 12D.

4. Method according to any one of claims 1 to 3, in which the ejection speed of the water at the outlet of the first (B1) and second (B2) nozzles is at least 18 m / s.

5. Method according to any one of claims 1 to 4, in which the water is projected onto the gas jet (J) by the first (B1) and second (B2) nozzles in the form of droplets having a volumetric median diameter of between 200 pm and 400 pm.

6. Method according to any one of claims 1 to 5, in which the passage section of the second zone (20) is greater than the passage section of the first zone (10).

7. Method according to any one of claims 1 to 6, in which the first (10) and second (20) zones can be moved relative to each other and each have a modular structure formed from a plurality of segments (11; 21) juxtaposed and removable relative to each other.

8. A method according to any one of claims 1 to 7, wherein removal of reducing gases from the gas jet is carried out by post-combustion upstream of the first zone (10).

9. Method according to any one of claims 1 to 8, in which a removal of the aerosols entrained by the gas jet is carried out in a demister (DE) downstream of the second zone (20).

10. Method according to any one of claims 1 to 9, in which 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 gas jet (J).

11. 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.

12. 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 takeoff.

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