EP2456562A1 - Aerodynamic chopper for gas flow pulsing - Google Patents

Aerodynamic chopper for gas flow pulsing

Info

Publication number
EP2456562A1
EP2456562A1 EP10752083A EP10752083A EP2456562A1 EP 2456562 A1 EP2456562 A1 EP 2456562A1 EP 10752083 A EP10752083 A EP 10752083A EP 10752083 A EP10752083 A EP 10752083A EP 2456562 A1 EP2456562 A1 EP 2456562A1
Authority
EP
European Patent Office
Prior art keywords
flow
disk
chopper
pulsed
flow device
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP10752083A
Other languages
German (de)
French (fr)
Other versions
EP2456562B1 (en
Inventor
Bertrand Rowe
Sebastien Morales
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Universite de Rennes 1
Original Assignee
Universite de Rennes 1
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Application filed by Universite de Rennes 1 filed Critical Universite de Rennes 1
Publication of EP2456562A1 publication Critical patent/EP2456562A1/en
Application granted granted Critical
Publication of EP2456562B1 publication Critical patent/EP2456562B1/en
Not-in-force legal-status Critical Current
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Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B12/00—Arrangements for controlling delivery; Arrangements for controlling the spray area
    • B05B12/02—Arrangements for controlling delivery; Arrangements for controlling the spray area for controlling time, or sequence, of delivery
    • B05B12/06—Arrangements for controlling delivery; Arrangements for controlling the spray area for controlling time, or sequence, of delivery for effecting pulsating flow
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B1/00—Nozzles, spray heads or other outlets, with or without auxiliary devices such as valves, heating means
    • B05B1/005—Nozzles or other outlets specially adapted for discharging one or more gases
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B1/00—Nozzles, spray heads or other outlets, with or without auxiliary devices such as valves, heating means
    • B05B1/02—Nozzles, spray heads or other outlets, with or without auxiliary devices such as valves, heating means designed to produce a jet, spray, or other discharge of particular shape or nature, e.g. in single drops, or having an outlet of particular shape
    • B05B1/08—Nozzles, spray heads or other outlets, with or without auxiliary devices such as valves, heating means designed to produce a jet, spray, or other discharge of particular shape or nature, e.g. in single drops, or having an outlet of particular shape of pulsating nature, e.g. delivering liquid in successive separate quantities ; Fluidic oscillators
    • B05B1/083—Nozzles, spray heads or other outlets, with or without auxiliary devices such as valves, heating means designed to produce a jet, spray, or other discharge of particular shape or nature, e.g. in single drops, or having an outlet of particular shape of pulsating nature, e.g. delivering liquid in successive separate quantities ; Fluidic oscillators the pulsating mechanism comprising movable parts
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/206—Flow affected by fluid contact, energy field or coanda effect [e.g., pure fluid device or system]
    • Y10T137/218—Means to regulate or vary operation of device
    • Y10T137/2185—To vary frequency of pulses or oscillations

Definitions

  • the present invention relates to a pulsed flow device. More particularly, the invention relates to a device for the flow of a supersonic flow.
  • the said invention proposes to provide a technical solution in the many areas where the flow of a gas or a liquid must be drawn for the purposes of the process or to limit the consumption and size of the pumping means.
  • flows obtained by a Laval nozzle it is possible to generate a uniform supersonic jet at very low temperature (currently up to 20K) and stable over hydrodynamic times between 150 and 1000 microseconds.
  • the purpose of this invention is to solve problems related to the use of aerodynamic tools in research and development and industrial processes.
  • the present invention has its origin in the evolution of an experimental device dedicated to the study of reactional and collisional processes and to low temperature spectroscopy called CRESU [I] (Kinetics of Reaction in Uniform Supersonic Flow).
  • CRESU [I] Kinetics of Reaction in Uniform Supersonic Flow.
  • This technique developed in the mid-1980s by BR Rowe, is based on the generation of a continuous, supersonic and uniform gas flow that constitutes a real ultracold chemical reactor without a wall. It consists of the use of a Laval nozzle (ie an axisymmetric profile composed of a convergent and a divergent) associated with large pumping capacities (33 000 m 3 / h) which generate, by an isentropic expansion, a uniform supersonic jet allowing to reach very low temperatures while remaining in gaseous phase.
  • Laval nozzle ie an axisymmetric profile composed of a convergent and a divergent
  • large pumping capacities 33 000 m 3 /
  • Accessible temperatures are presently in the range 15-300 K for typical densities ranging from 10 16 to 10 17 cm- 3 .
  • An essential aspect of the CRESU technique is that it allows to work in equilibrium conditions local thermodynamics (in particular for rotational and spin-orbit states) and is the only one to study neutral-neutral reactions at very low temperatures [2]. Nevertheless, this technique, like all processes using supersonic flows, faces major drawbacks arising from the requirement to work with high flow rates, typically of the order of 50 Standard Liter / min, in order to maintain a stable isentropic core. long enough. Therefore, a large pumping capacity is essential to maintain a low pressure in the decompression chamber. This large pumping results in a high gas consumption which makes it difficult to study expensive or synthetic chemical species.
  • the first system to reproduce the CRESU technique in a pulsed version was developed by DB Atkinson and M. A Smith [9] and resides in a periodic filling of the tank via commercial pulsed valves.
  • Five other means of testing this principle have been developed at the international level (Smith, Arlington, USA, S. Leone, Berkeley University, USA, J. Troe, University of Goettingen, Germany, M. Pilling, University of Leeds, GB or high pressure M. Costes, University of Bordeaux). These test facilities remain nevertheless limited in temperature and are generally operational only above 50 K.
  • the solution is to reduce the size of the nozzle. tanks ( ⁇ 1 cm 3 ).
  • Such a solution requires preparation in advance of the gas mixtures to be injected and their conditioning in a pre-tank in limited quantities.
  • this solution induces flow disturbances, the generator conditions of the reservoir being no longer clearly defined because of the high speed gradients in the small reservoir.
  • the cylinder system of Kenny and Woudenberg [4] has a geometry that is difficult to transpose in most applications.
  • the device according to the invention aims to maintain stable pressure and reservoir flow conditions while producing a uniform flow and without limiting the size of the tank.
  • the device according to the invention also has the objective of not having to prepare and condition in advance in pre-reservoirs the gas mixtures to be injected.
  • the invention therefore relates to a pulsed flow device comprising a continuous injection into the device fed by a reservoir, a means of obstruction of the flow, the obstruction means being combined with a dynamic sealing system of sealing manner around the flow, characterized in that the blocking means opens and closes the flow at high frequencies.
  • the device according to the invention proposes to draw the supersonic flows by a mechanical shutter of the chopper type on a flow section without resorting to pulsed injection into the reservoir which allows, at sufficiently high shutter frequency, obtain a pseudo stationary regime for all flow rate settings.
  • the general operating principle is to draw the flow by closing the passage section of the gas or liquid via an obstruction means, for example a perforated rigid disk rotating at high speed.
  • an obstruction means for example a perforated rigid disk rotating at high speed.
  • the system is installed on the divergent, the exact position depending on the geometry of the nozzle.
  • the rotation frequency is such that the reservoir conditions remain unchanged (P 0 , T 0 ) when the system reaches a pseudo-stationary regime.
  • the device according to the invention can greatly reduce the average flow rate to be injected into the tank and thus reduce in the same proportions the pumping capacity necessary to maintain a low pressure in the expansion chamber.
  • the device according to the invention is not subject to flow disturbances such as those present in the state of the art.
  • the obstruction means is a rotary or reciprocating mechanical disk for opening and closing the flow.
  • the axis of rotation of the disk does not pass through an axis of flow flow, the disk having a hole, a rotation of the disk alternately bringing a full part of the disk and said hole opposite the flow.
  • the disk further includes a cut in an edge of said disk, said edge being opposite to the hole relative to the center of the disk.
  • the hole is preferably of oblong shape in this improvement.
  • the dynamic sealing system comprises a main seal, a secondary seal, an upstream ring and a seal compensating the movement variations of the chopper ensuring contact conditions between the chopper and the mechanical components profiling the flow.
  • One embodiment provides that the geometries of the dynamic sealing system and the obstruction means are adapted to the Laval nozzles, allowing in particular the retention of flow uniformity properties.
  • Another embodiment provides that the geometries of the dynamic sealing system and the obstruction means are adapted to planar and axisymmetric nozzle shapes.
  • the obstruction means is a plane plate in reciprocating motion.
  • the invention also relates to a use of a pulsed gas flow device according to the invention as aerodynamic windows or to protect optical passage elements of the optical window type.
  • a particular mode of use of the invention provides for the use of the device according to the invention in order to generate flows at very low temperatures.
  • FIG. 1 represents a schematic perspective view comprising a portion in transparency of a device according to the invention
  • FIG. 2 represents a cross-sectional view of a device according to the invention
  • FIG. 3 represents a comparison of the various techniques used to characterize, in temperature, the pulsed jet obtained using the aerodynamic chopper;
  • FIG. 4 shows a rovibronic spectrum of the CN radical obtained by LIF (Laser Induced Fluorescence) and used to determine the rotational temperature of the flow.
  • FIG. 1 represents a schematic perspective view comprising a portion in transparency of a device according to the invention
  • the device comprises a portion 22 said main portion 22, a system 21 hashing and a reservoir 23 at the origin of the injection of gas into the flow device.
  • the hash system 21 is supported by the main portion 22 and includes a chopper 3, or disk or other means of alternative opening obstruction. Said main portion 22 is fixed on a reservoir 23, said reservoir being at the origin of the injection in the gas flow device or any other element to be pulsed.
  • This main portion 22 consists of two main supports 1 and 2 rigid circular shape having for example a diameter of 340 mm and a thickness of 20 mm. These supports 1 and 2 are facing each other. In the case of a Laval nozzle, the respective centers of the main supports 1 and 2 are drilled to receive bases 12 and 19 containing the convergent and divergent profiles of the nozzles 13 and 18.
  • a bore 24 with a stop is machined to receive the bearings used for the rotation of the chopper axis 3.
  • two holes are drilled, intended to receive Socket bearings 4 in which will be positioned two major axes 5 mounted on the reservoir 23.
  • the main part 22 is mounted on the gas tank 23 via the two axes 5. More particularly, the main portion 22 is mounted by sliding on these axes 5 to be connected to the reservoir 23.
  • the sliding assembly allows a displacement of the main portion 22 along these axes 5 and a facilitated clearance of said part pri ncipale 22 of the reservoir 23 and an easy change of said main portion 22 and / or the nozzle 13 and / or 18 depending on the needs of use. .
  • the adjustment of the guide 6 is performed by micrometric screws fixed on the supports 1 and 2 which push the bearing mounts, the return against being provided by springs.
  • the two supports 1 and 2 are mounted face to face thanks to three positioning columns 7) of 20 mm in diameter, said columns 7 being for example nested in the faces 25 of the main supports 1 and 2 respectively vis-a-vis the one of the other.
  • This arrangement allows parallelism and alignment between the two supports 1 and 2.
  • the distance between the two supports 1 and 2 is minimized to optimize the accuracy of settings.
  • the main support 2 dedicated to the divergent portion of the nozzle 18 receives the fasteners of the motor 8 driving the chopper 3.
  • the chopper 3 is in the form of a disc 3.
  • the diameter of the chopper 3 is 240 mm, for a thickness of 1 to 2 mm.
  • An oblong hole 26 of variable arc length and diameter 12 mm is arranged at 90 mm from the center of the chopper 3.
  • a cut is made on an edge 27 opposite the oblong hole 26 relative to the center of the chopper 3. This cutout allows to balance the disk 3 despite the presence of the oblong hole 26. This maintenance of the balance avoids the unbalance and vibration of the disc 3 at high rotation speed.
  • all the ribs provided are only indicative and obviously depend on the sizing of the installation and the desired performance.
  • the chopper 3 is such that the axis of rotation of said chopper is parallel to the flow and does not pass through said flow.
  • the chopper hole 26 is located at a distance from the center equal to a distance separating the chopper center 3 from the gas flow. This distance is in fact adapted to ensure an alternative look of the hole with the axis of the flow. Edge cutting said chopper 3 is performed to balance the rotation of the chopper. The cutout is arranged opposite the hole relative to the center of the chopper 3.
  • FIG. 2 represents a cross-sectional view of a device according to the invention.
  • the chopper 3 rotates between the convergent (12, 13) and divergent portion (18, 19) of the nozzle. .
  • the chopper 3 is preferably thin and perfectly flat.
  • the chopper 3 can be monobloc, glass or ceramic.
  • Another solution is to use a disc 3 composed of a metal part (stainless steel, aluminum, ...) coated with a pure or filled Teflon deposit, PFA or a composite material, the properties of which are a compromise between good coefficient of friction and a high wear resistance.
  • the solution of a collage of several layers is remember because it allows to cumulate the properties of the constituents and to avoid the deformations due to the deposition process.
  • the chopper 3 On the main part 22, the chopper 3 is held between two cylindrical fastening parts 9 and 10. The two fasteners 9 and 10 are bored at their center. A transmission shaft 1 1 cooperating with the chopper 3 is inserted into these bores 9 and 10. The bores 9 and 10 and the shaft 1 1 are finely adjusted to allow the translation with a reduced clearance of the whole chopper 3 and allow the positioning between the convergent (12,13) and the divergent (18,19) of the nozzle, and easy disassembly of the system 21 hashing.
  • a first element called a convergent base 12
  • the converging base 12 comprises a complementary housing the upstream portion 13 of the nozzle, said housing is adapted to receive said upstream portion 13 of the nozzle. This mechanism is useful when changing the nozzle because it is then easy to replace a profile without disassembling the entire system.
  • the convergent base 12 is inserted into the main support 1 by the central bore and is fixed by screwing.
  • the nozzle 13 which under the effect of the upstream pressure and compression springs, abuts on the convergent base 12 ensuring the seal between the reservoir 22 and the expansion chamber through at one or two joints 14 on the smaller diameter of the upstream portion of the nozzle 13. It is within the upstream portion of the nozzle 13 that is embedded in the heart of the sealing system of the device.
  • a sealing system can be as described below or any type known to those skilled in the art. This sealing system ensures a seal in the device despite the presence of the chopper 3 and thus ensures that the pressure and flow conditions are not disturbed by a leakage.
  • the basic principle used to ensure a good seal is based on seals 15, 16 and 20 in dynamic regime with friction, that is to say in contact with the chopper 3 rotating while ensuring a good seal.
  • the technical solution consists in using mobile joints 15, 16 and 20 positioned abutting on the disc 3. To do this, an impression is made on the upstream part of the nozzle 13 as close as possible to the profile, intended to receive a bronze ring 17 on which will be mounted the main seal 15.
  • This ring 17 carries the main chopper seal 15 in contact with the disc 3.
  • the secondary chopper seal 16 is added on its inner axis the secondary chopper seal 16.
  • the contact force which conditions the seal and the braking torque applied to the disc 3 , is regulated by a set of springs of different rigidities.
  • a seal is provided in the divergent portion of the nozzle in a manner quite similar to the seal described above: it integrates the divergent portion of the nozzle 18 and its base 19 for fixing on the main support 2, according to the same principle as previously.
  • the nozzle 18 is not movable, it is simply fixed in abutment on the divergent base 19 by screwing. In this part downstream of the disc, the sealing needs no longer exist.
  • the pressure difference between the tank and the chamber leads to the application of a force on the chopper which can then be veiled.
  • the same type of mobile joint 20 as on the upstream part of the nozzle is used.
  • An orifice is pierced on the chopper 3 opposite the optoelectronic sensor in a corresponding position at the beginning of the opening of the nozzle.
  • the collected signal is used to calculate the rotational speed of the disk 3.
  • this signal is used as a control driving any other type of synchronized system to the aerodynamic chopper, such as, for example, the triggering of laser shots .
  • the reservoir 23 comprises a gas under pressure at a certain temperature.
  • This reservoir 23 feeds the main part 22, and more particularly the upstream nozzle 13 with a certain flow rate.
  • Chopper 3 undergoes a high frequency rotation.
  • This high frequency rotation of the chopper 3 alternately releases and obstructs, at said high frequency, the flow according to whether the oblong hole 26 is respectively or opposite the flow.
  • the examples below give examples of values and measurements of operation or obtainable by the device according to the invention.
  • the first tests were carried out using the profile of a Laval nozzle operating in continuous mode with the following characteristics: an average flow temperature of 24K over a uniformity distance of 33 cm (196 ⁇ s), an instantaneous flow rate of 100 Standard liters / min, a tank pressure of 336 mbar and a chamber pressure of 0.63 mbar.
  • the tests carried out using the aerodynamic chopper allowed to generate a pulsed flow, stable over a distance of 45 cm (266 ⁇ s) at the temperature of 22K, with a pulse frequency of up to 20 Hz for pulses d a duration of 8 ms.
  • FIG. 3 represents a comparison of different techniques used to characterize, in temperature, the pulsed jet obtained using the device according to the invention:
  • Curve (a) illustrates the results from a numerical simulation of the time resolution type of Navier Stokes equations in 2-D for this nozzle profile.
  • Curve (b) shows the results from the Pitot tube impact pressure measurement at different positions in the nozzle axis. The peculiarity of these pitot measurements arises from the fact that each point of the impact pressure curve is obtained by taking an average value of the maximum on the plateau of curves representing the pulse of impact pressure as a function of time, identical to those of Figures (e) and (f).
  • the points (c) represent rotational temperature measurements obtained by spectroscopy of the CN radical (study of the population distribution of the R branch of the spectrum) as a function of the position of the nozzle.
  • the points (d) represent rotational temperature measurements obtained by spectroscopy of the radical CN (study of the population distribution of the branch P of the spectrum) as a function of the position of the nozzle.
  • Figure 4 shows a rovibronic spectrum of the CN radical obtained by LIF (Laser Induced Fluorescence) and used to determine the rotational temperature of the flow.
  • the quality of the flows obtained by this device is excellent because well established over times ranging from a hundred microsecond to millisecond. It can even be superior to the stationary case by reducing turbulence in the tank.
  • Various modifications can be made to the aerodynamic chopper, with a view to adapting it to a geometry different from that of a Laval nozzle or to reducing the size of the system.
  • the description given constitutes a basis for the technical solution and a non-limiting example with respect to the ribs of the system and the materials used.
  • the invention is an independent and compact apparatus that attaches to the tank of a global installation, which makes it easily transportable and adaptable.

Abstract

The present invention relates to a supersonic pulse flow device. Said invention is intended to provide a technical solution in a number of fields where the injection of a flow must be pulsed as required by the process or in order to limit the power consumption and size of the pumping means. In the event of flows obtained through a de Laval nozzle (13, 18), it is possible to generate a uniform supersonic jet having a very low temperature (currently up to 20 K) that is stable over hydrodynamic periods of time between 150 and 1000 microseconds. The aim of said invention is to resolve problems related to the use of aerodynamic tools in research and development and in industrial processes.

Description

Hacheur aérodynamique pour la pulsation d'écoulement de gaz  Aerodynamic chopper for gas flow pulsation
La présente invention concerne un dispositif d'écoulement puisé. Plus particulièrement l'invention concerne un dispositif d'écoulement d'un flux supersonique. La dite invention se propose de fournir une solution technique dans les nombreux domaines où l'écoulement d'un gaz, ou d'un liquide, doit être puisé pour les besoins du processus ou pour limiter la consommation et la taille des moyens de pompage. Dans le cas d'écoulements obtenus par une tuyère de Laval, il est possible de générer un jet supersonique uniforme à très basse température (actuellement jusqu'à 20K) et stable sur des temps hydrodynamiques compris entre 150 et 1000 microsecondes. Cette invention a pour but de résoudre des problèmes liés à l'utilisation d'outils aérodynamiques en recherche et développement et procédés industriels. La présente invention trouve son origine dans l'évolution d'un dispositif expérimental dédié à l'étude des processus réactionnels et collisionnels et à la spectroscopie à basse température appelé CRESU[I ](Cinétique de Réaction en Ecoulement Supersonique Uniforme). Cette technique développée au milieu des années 80 par B. R. Rowe est basée sur la génération d'un écoulement de gaz continu, supersonique et uniforme qui constitue un véritable réacteur chimique ultrafroid sans paroi. Elle consiste en l'utilisation d'une tuyère de Laval (c.-à-d. un profil axisymétrique composé d'un convergent et d'un divergent) associée à de grandes capacités de pompage (33 000 m3/h) qui génèrent, par une détente isentropique, un jet supersonique uniforme permettant d'atteindre des températures très basses tout en restant en phase gazeuse. Les températures accessibles sont comprises, actuellement, dans la gamme 15-300 K pour des densités typiques allant de 1016 à 1017 cm"3. Un aspect essentiel de la technique CRESU est qu'elle permet de travailler dans des conditions d'équilibre thermodynamique local (en particulier pour les états de rotation et de spin-orbite). Elle est aussi la seule permettant d'étudier les réactions neutre-neutre à très basses températures[2]. Néanmoins, cette technique comme tous les procédés utilisant des écoulements supersoniques, est confrontée à des inconvénients majeurs provenant de l'exigence de travailler avec des débits importants, typiquement de l'ordre de 50 Standard Litre/min, afin de conserver un cœur isentropique stable suffisamment longtemps. De ce fait, une grande capacité de pompage est indispensable pour maintenir une faible pression dans la chambre de détente. Ce pompage important entraîne une forte consommation de gaz qui rend difficile l'étude d'espèces chimiques coûteuses ou issues d'une synthèse. Pour répondre à cette problématique, la perspective de puiser l'écoulement s'avère être une des meilleurs solutions. Amirav et al [3] ont décrit un appareillage en fente puisée capable de générer un jet libre planaire puisé dédié à l'étude spectroscopique. Un jet libre se caractérise par la détente d'un gaz par un simple orifice dans un environnement à basse pression sans être confiné par les parois d'une tuyère. Ce type de jet est simple à mettre en place car il ne nécessite pas la mise au point de tuyères au profil sophistiqué. Suite à ces travaux, Kenny et Woundenberg ont déposé un brevet[4] N° 4 834 288 pour un appareil fonctionnant avec une fréquence de répétition de 12 Hz et une durée de pulsation de 120 microsecondes, basée sur la rotation de deux cylindres concentriques percés d'une fente de 0,2 mm de largeur et de 35 mm de longueur. Ce système a la possibilité d'être chauffé jusqu'à une température de 200 °C. Cet appareillage a été utilisé pour des études de spectroscopie en absorption et/ou en LIF (Laser Induced Fluorescence) sur des molécules organiques de grande taille[5]. L'utilisation de jet supersonique pour la spectroscopie est une méthode très répandue car elle permet de décongestionner les spectres par la relaxation des différents degrés de liberté des molécules. En effet, la mise en mouvement des molécules transforme l'énergie thermique en énergie cinétique dirigée ce qui entraine un abaissement de la température translationnelle et un resserrement de la distribution en vitesse des molécules. On assiste à une thermalisation par collision des états rotationnels et vibrationnels par transfert d'énergie vers la translation. Ces transfert d'énergie sont extrêmement rapides et permettent aux différents degrés de liberté, dans la première phase de la détente où les chocs sont nombreux, de s'équilibrer se traduisant par la thermalisation des différents états. La grande simplification spectrale induite dans les écoulements supersoniques, surtout dans le cas de spectre de molécules polyatomiques complexes, en ont fait un outil très populaire chez les spectroscopistes. Un autre brevet N° 5 295 509, déposé par Suto et al [6] décrit un système de tuyère puisée adapté à l'étude des réactions à basses températures et à l'utilisation de fort débit sans réduction des vitesses de pulsation. Ce système utilise deux membranes percées de multiples fentes où deux actionneurs piézoélectriques alimentés par un générateur de pulsation permettent de déplacer l'une des membranes. Ceci conduit au passage ou non du gaz dans la tuyère lors de l'alignement des fentes. The present invention relates to a pulsed flow device. More particularly, the invention relates to a device for the flow of a supersonic flow. The said invention proposes to provide a technical solution in the many areas where the flow of a gas or a liquid must be drawn for the purposes of the process or to limit the consumption and size of the pumping means. In the case of flows obtained by a Laval nozzle, it is possible to generate a uniform supersonic jet at very low temperature (currently up to 20K) and stable over hydrodynamic times between 150 and 1000 microseconds. The purpose of this invention is to solve problems related to the use of aerodynamic tools in research and development and industrial processes. The present invention has its origin in the evolution of an experimental device dedicated to the study of reactional and collisional processes and to low temperature spectroscopy called CRESU [I] (Kinetics of Reaction in Uniform Supersonic Flow). This technique, developed in the mid-1980s by BR Rowe, is based on the generation of a continuous, supersonic and uniform gas flow that constitutes a real ultracold chemical reactor without a wall. It consists of the use of a Laval nozzle (ie an axisymmetric profile composed of a convergent and a divergent) associated with large pumping capacities (33 000 m 3 / h) which generate, by an isentropic expansion, a uniform supersonic jet allowing to reach very low temperatures while remaining in gaseous phase. Accessible temperatures are presently in the range 15-300 K for typical densities ranging from 10 16 to 10 17 cm- 3 . An essential aspect of the CRESU technique is that it allows to work in equilibrium conditions local thermodynamics (in particular for rotational and spin-orbit states) and is the only one to study neutral-neutral reactions at very low temperatures [2]. Nevertheless, this technique, like all processes using supersonic flows, faces major drawbacks arising from the requirement to work with high flow rates, typically of the order of 50 Standard Liter / min, in order to maintain a stable isentropic core. long enough. Therefore, a large pumping capacity is essential to maintain a low pressure in the decompression chamber. This large pumping results in a high gas consumption which makes it difficult to study expensive or synthetic chemical species. To answer this problem, the prospect of drawing the flow turns out to be one of the best solutions. Amirav et al [3] have described a pulsed slot apparatus capable of generating a pulsed planar free jet dedicated to spectroscopic study. A free jet is characterized by the expansion of a gas by a single orifice in a low pressure environment without being confined by the walls of a nozzle. This type of jet is simple to put in place because it does not require the development of sophisticated profile nozzles. Following this work, Kenny and Woundenberg filed a patent [4] No. 4,834,288 for an apparatus operating with a repetition frequency of 12 Hz and a pulse duration of 120 microseconds, based on the rotation of two concentric cylinders pierced a slot 0.2 mm wide and 35 mm long. This system has the possibility of being heated up to a temperature of 200 ° C. This apparatus has been used for absorption and / or LIF (Laser Induced Fluorescence) spectroscopy studies on large organic molecules [5]. The use of supersonic jet for spectroscopy is a very common method because it allows decongesting the spectra by the relaxation of the different degrees of freedom of the molecules. Indeed, the setting in movement of the molecules transforms the thermal energy into directed kinetic energy which leads to a lowering of the translational temperature and a tightening of the velocity distribution of the molecules. We observe a thermalization by collision of the rotational and vibrational states by transfer of energy towards the translation. These energy transfers are extremely fast and allow the different degrees of freedom, in the first phase of the relaxation where the shocks are numerous, to equilibrate resulting in the thermalization of different states. The great spectral simplification induced in supersonic flows, especially in the case of complex polyatomic particle spectra, has made it a very popular tool among spectroscopists. Another patent No. 5,295,509, filed by Suto et al [6] describes a pulsed nozzle system adapted to the study of reactions at low temperatures and the use of high flow without reducing pulsation rates. This system uses two diaphragms pierced with multiple slots where two piezoelectric actuators powered by a pulse generator can move one of the membranes. This leads to the passage or no gas in the nozzle during the alignment of the slots.
Okada et Takeuchi [7] ont développé un jet supersonique planaire puisé utilisant un dispositif d'arbre à cames pour puiser l'injection de gaz dans le réservoir de la tuyère. Avec une épaisseur au col de 3 mm et une longueur de 500 mm pour une durée de puise minimum de 25 ms, ce type d'instrument a été utilisé lors d'études spectroscopiques, le caractère planaire permettant d'augmenter le trajet optique et donc le nombre de molécules absorbantes. Le CEA a également proposé un type de système puisé (brevet N° 7 093 774 B2) par l'invention de Martin [8] dans le but de permettre l'injection de matière dans une installation d'étude des plasmas de fusion thermonucléaire sur un principe de fermeture par un piston mise en mouvement par compression. Les données techniques ont montré que ce système autorisait une ouverture de soupape d'une durée de 2 ms à une fréquence de fonctionnement de 10 Hz. Okada and Takeuchi [7] developed a pulsed planar supersonic jet using a camshaft device to draw gas into the nozzle tank. With a neck thickness of 3 mm and a length of 500 mm for a minimum pulse duration of 25 ms, this type of instrument has been used in spectroscopic studies, the planar character making it possible to increase the optical path and therefore the number of absorbing molecules. The CEA has also proposed a type of pulsed system (patent No. 7,093,774 B2) by the invention of Martin [8] in order to allow the injection of material into a facility for studying thermonuclear fusion plasmas on a principle of closure by a piston set in motion by compression. The technical data showed that this system allowed a valve opening with a duration of 2 ms at an operating frequency of 10 Hz.
Le premier système visant à reproduire la technique CRESU dans une version puisée a été développé par D. B. Atkinson et M. A Smith [9] et réside en un remplissage périodique du réservoir via des vannes puisées commerciales. Cinq autres moyens d'essais sur ce principe ont été développés au niveau international (M. Smith, Tucson, USA; S. Leone, Université de Berkeley, USA; J. Troe, Université de Goettingen, Allemagne; M. Pilling, Université de Leeds, GB ou à haute pression M. Costes, Université de Bordeaux). Ces moyens d'essais restent néanmoins limités en température et ne sont en général opérationnels qu'au dessus de 50 K. The first system to reproduce the CRESU technique in a pulsed version was developed by DB Atkinson and M. A Smith [9] and resides in a periodic filling of the tank via commercial pulsed valves. Five other means of testing this principle have been developed at the international level (Smith, Tucson, USA, S. Leone, Berkeley University, USA, J. Troe, University of Goettingen, Germany, M. Pilling, University of Leeds, GB or high pressure M. Costes, University of Bordeaux). These test facilities remain nevertheless limited in temperature and are generally operational only above 50 K.
Depuis son invention dans les années 80, la technique CRESU ainsi que ses versions puisées ont apporté une forte contribution dans le domaine de la réactivité en phase gaz des milieux extrêmes[10-12]. Elles se sont également inscrites comme des outils aérodynamiques remarquables et au fort potentiel dans de nombreux domaines réclamant le recours à des écoulements à importants flux de gaz à haute vitesse. Malgré cela, aucune réelle adaptation complète du système CRESU n'a vu le jour pour permettre une forte démocratisation de la technique et sa transposition vers d'autres champs d'application. Since its invention in the 1980s, the CRESU technique and its pulsed versions have made a strong contribution in the field of reactivity in the gas phase of extreme environments [10-12]. They have also established themselves as outstanding aerodynamic tools with high potential in many areas requiring the use of flows with large gas flows at high speeds. Despite this, no real complete adaptation of the CRESU system has emerged to allow a strong democratization of the technique and its transposition to other fields of application.
Toutes les inventions précédemment citées ont en commun une difficulté fondamentale d'établir des conditions non stationnaires strictement identiques à celles de l'écoulement stationnaire en raison du temps de remplissage du réservoir. Typiquement, les dispositifs cités ci-dessus ne permettent pas d'obtenir un écoulement uniforme avec des conditions de pression et de débit d'alimentation de la tuyère stables sans consommation excessive de gaz ; le réservoir devant être régulièrement rempli, il ne peut alimenter l'écoulement en conservant des conditions d'injection dans le dispositif stables. All the inventions mentioned above have in common a fundamental difficulty in establishing non-stationary conditions strictly identical to those of stationary flow because of the filling time of the tank. Typically, the devices mentioned above do not provide a uniform flow with stable pressure and feed rate conditions of the nozzle without excessive gas consumption; the reservoir must be regularly filled, it can not feed the flow by maintaining stable injection conditions in the device.
Pour atteindre le point de fonctionnement de la tuyère (c.-à-d. les conditions de pression et de débit stable conduisant un écoulement uniforme) dans un temps raisonnable, actuellement entre 5 et 10 ms, la solution consiste à réduire la taille de réservoirs (~1 cm3). Une telle solution impose une préparation à l'avance des mélanges de gaz à injecter ainsi que leur conditionnement dans un pré-réservoir dans des quantités limitées. De plus cette solution induit des perturbations d'écoulement, les conditions génératrices du réservoir n'étant plus clairement définis du fait des forts gradients de vitesse dans le petit réservoir. Le système à cylindres de Kenny et Woudenberg [4] présente une géométrie difficilement transposable dans la plupart des applications. Le dispositif selon l'invention a pour but de conserver des conditions de pression et de débit du réservoir stables tout en produisant un écoulement uniforme et ce sans limiter la taille du réservoir. Le dispositif selon l'invention a en outre pour objectif de ne pas avoir à préparer et conditionner à l'avance dans des pré- réservoirs les mélanges de gaz à injecter. To reach the point of operation of the nozzle (ie pressure and steady flow conditions leading to uniform flow) in a reasonable time, currently between 5 and 10 ms, the solution is to reduce the size of the nozzle. tanks (~ 1 cm 3 ). Such a solution requires preparation in advance of the gas mixtures to be injected and their conditioning in a pre-tank in limited quantities. In addition this solution induces flow disturbances, the generator conditions of the reservoir being no longer clearly defined because of the high speed gradients in the small reservoir. The cylinder system of Kenny and Woudenberg [4] has a geometry that is difficult to transpose in most applications. The device according to the invention aims to maintain stable pressure and reservoir flow conditions while producing a uniform flow and without limiting the size of the tank. The device according to the invention also has the objective of not having to prepare and condition in advance in pre-reservoirs the gas mixtures to be injected.
L'invention a donc pour objet un dispositif d'écoulement puisé comportant une injection continue dans le dispositif alimentée par un réservoir, un moyen d'obstruction de l'écoulement, le moyen d'obstruction étant combiné à un système d'étanchéité dynamique de manière étanche autour de l'écoulement, caractérisé en ce que le moyen d'obstruction ouvre et ferme par obstruction l'écoulement à des fréquences élevées. The invention therefore relates to a pulsed flow device comprising a continuous injection into the device fed by a reservoir, a means of obstruction of the flow, the obstruction means being combined with a dynamic sealing system of sealing manner around the flow, characterized in that the blocking means opens and closes the flow at high frequencies.
Le dispositif selon l'invention se propose de puiser les écoulements supersoniques par un obturateur mécanique de type hacheur sur une section d'écoulement sans avoir recours à l'injection puisée dans le réservoir ce qui permet, à fréquence d'obturation suffisamment élevée, d'obtenir un régime pseudo stationnaire pour tous les réglages de débits. Le principe de fonctionnement général consiste à puiser l'écoulement par l'obturation de la section de passage du gaz ou du liquide via un moyen d'obstruction, par exemple un disque rigide perforé tournant à grande vitesse. Dans le cas d'une tuyère de Laval, le système est installé sur le divergent, la position exacte dépendant de la géométrie de la tuyère. La fréquence de rotation est telle que les conditions de réservoir restent inchangées (P0, T0) quand le système atteint un régime pseudo-stationnaire. Ce dispositif permet de réduire fortement le débit moyen à injecter dans le réservoir et ainsi de réduire dans les mêmes proportions les capacités de pompage nécessaires pour conserver une basse pression dans la chambre de détente. De plus, le dispositif selon l'invention n'est pas sujet à des perturbations d'écoulement telles que celles présentes dans l'état de la technique. Dans une variante de l'invention le moyen d'obstruction est un disque mécanique rotatif ou à mouvement alternatif permettant d'ouvrir et de fermer l'écoulement. The device according to the invention proposes to draw the supersonic flows by a mechanical shutter of the chopper type on a flow section without resorting to pulsed injection into the reservoir which allows, at sufficiently high shutter frequency, obtain a pseudo stationary regime for all flow rate settings. The general operating principle is to draw the flow by closing the passage section of the gas or liquid via an obstruction means, for example a perforated rigid disk rotating at high speed. In the case of a Laval nozzle, the system is installed on the divergent, the exact position depending on the geometry of the nozzle. The rotation frequency is such that the reservoir conditions remain unchanged (P 0 , T 0 ) when the system reaches a pseudo-stationary regime. This device can greatly reduce the average flow rate to be injected into the tank and thus reduce in the same proportions the pumping capacity necessary to maintain a low pressure in the expansion chamber. In addition, the device according to the invention is not subject to flow disturbances such as those present in the state of the art. In a variant of the invention, the obstruction means is a rotary or reciprocating mechanical disk for opening and closing the flow.
Avantageusement, dans un perfectionnement, l'axe de rotation du disque ne passe pas par un axe d'écoulement du flux, le disque comportant un trou, une rotation du disque amenant alternativement une partie pleine du disque et ledit trou en regard de l'écoulement. Le disque comporte en outre une coupe dans un bord dudit disque, ledit bord étant opposé au trou par rapport au centre du disque. Le trou est préférentiellement de forme oblongue dans ce perfectionnement. Advantageously, in an improvement, the axis of rotation of the disk does not pass through an axis of flow flow, the disk having a hole, a rotation of the disk alternately bringing a full part of the disk and said hole opposite the flow. The disk further includes a cut in an edge of said disk, said edge being opposite to the hole relative to the center of the disk. The hole is preferably of oblong shape in this improvement.
Avantageusement, le système d'étanchéité dynamique comporte un joint principal, un joint secondaire, une bague amont et un joint compensant les variations de mouvement du hacheur garantissant les conditions de contact entre le hacheur et les composants mécaniques profilant l'écoulement. Advantageously, the dynamic sealing system comprises a main seal, a secondary seal, an upstream ring and a seal compensating the movement variations of the chopper ensuring contact conditions between the chopper and the mechanical components profiling the flow.
Un mode de réalisation prévoit que les géométries du système d'étanchéité dynamique et du moyen d'obstruction sont adaptées aux tuyères de Laval, permettant en particulier la conservation des propriétés d'uniformité des écoulements. One embodiment provides that the geometries of the dynamic sealing system and the obstruction means are adapted to the Laval nozzles, allowing in particular the retention of flow uniformity properties.
Un autre mode de réalisation prévoit que les géométries du système d'étanchéité dynamique et du moyen d'obstruction sont adaptées aux tuyères de formes planaires et axisymétriques. Another embodiment provides that the geometries of the dynamic sealing system and the obstruction means are adapted to planar and axisymmetric nozzle shapes.
Dans une variante, le moyen d'obstruction est une plaque plane en mouvement alternatif. In a variant, the obstruction means is a plane plate in reciprocating motion.
L'invention a aussi pour objet une utilisation d'un dispositif d'écoulement puisé de gaz selon l'invention comme fenêtres aérodynamiques ou pour protéger des éléments de passage optiques du type fenêtre optique. Un mode d'utilisation particulier de l'invention prévoit l'utilisation du dispositif selon l'invention afin de générer des écoulements à très basses températures. The invention also relates to a use of a pulsed gas flow device according to the invention as aerodynamic windows or to protect optical passage elements of the optical window type. A particular mode of use of the invention provides for the use of the device according to the invention in order to generate flows at very low temperatures.
La présente invention est maintenant décrite à l'aide d'exemples uniquement illustratifs et nullement limitatifs de la portée de l'invention, et à partir des illustrations ci-jointes, dans lesquelles : The present invention is now described with the aid of examples which are only illustrative and in no way limit the scope of the invention, and from the attached illustrations, in which:
- La figure 1 représente une vue en perspective schématique comportant une partie en transparence d'un dispositif selon l'invention ;  FIG. 1 represents a schematic perspective view comprising a portion in transparency of a device according to the invention;
- La figure 2 représente une vue en coupe transversale d'un dispositif selon l'invention ;  FIG. 2 represents a cross-sectional view of a device according to the invention;
- La figure 3 représente une comparaison des différentes techniques utilisées pour caractériser, en température, le jet puisé obtenu à l'aide du hacheur aérodynamique ;  FIG. 3 represents a comparison of the various techniques used to characterize, in temperature, the pulsed jet obtained using the aerodynamic chopper;
- La figure 4 montre un spectre rovibronique du radical CN obtenu par LIF « (Laser Induced Fluorescence » en anglais) et utilisé pour déterminer la température rotationnelle de l'écoulement.  FIG. 4 shows a rovibronic spectrum of the CN radical obtained by LIF (Laser Induced Fluorescence) and used to determine the rotational temperature of the flow.
La figure 1 représente une vue en perspective schématique comportant une partie en transparence d'un dispositif selon l'invention FIG. 1 represents a schematic perspective view comprising a portion in transparency of a device according to the invention
Les dimensions données ci après le sont à titre d'exemple et ne sont nullement limitatives de la portée de l'invention, pouvant être adaptées par l'homme de l'art en fonction des applications. L'exemple donné ci-dessous est donné pour un écoulement puisé de gaz, mais l'invention s'applique de manière identique à un écoulement d'un autre type qu'un écoulement puisé de gaz, par exemple un écoulement de liquide. The dimensions given below are by way of example and are in no way limitative of the scope of the invention, which can be adapted by those skilled in the art depending on the applications. The example given below is given for a pulsed flow of gas, but the invention applies identically to a flow of another type than a pulsed flow of gas, for example a flow of liquid.
Le dispositif comprend une partie 22 dite partie principale 22, un système 21 de hachage et un réservoir 23 à l'origine de l'injection de gaz dans le dispositif d'écoulement. The device comprises a portion 22 said main portion 22, a system 21 hashing and a reservoir 23 at the origin of the injection of gas into the flow device.
Le système 21 de hachage est supporté par la partie principale 22 et comprend un hacheur 3, ou disque ou tout autre moyen d'obstruction à ouverture alternative. Ladite partie principale 22 est fixée sur un réservoir 23, ledit réservoir étant à l'origine de l'injection dans le dispositif d'écoulement de gaz ou tout autre élément devant être puisé. Cette partie principale 22 est constituée de deux supports principaux 1 et 2 rigides de forme circulaire ayant par exemple un diamètre 340 mm et une épaisseur 20 mm. Ces supports 1 et 2 sont en regard l'un de l'autre. Dans le cas d'une tuyère de Laval, les centres respectifs des supports principaux 1 et 2 sont percés pour accueillir des socles 12 et 19 contenant les profils convergents et divergents des tuyères 13 et 18. A une distance de 90 mm des centres des supports principaux 1 et 2, un alésage 24 avec butée est usiné afin de recevoir les roulements utilisés pour la rotation de l'axe du hacheur 3. A 140 mm des centres des supports principaux 1 et 2, deux trous sont percés, destinés à recevoir des roulements à douille 4 dans lesquelles viendront se positionner deux grands axes 5 montés sur le réservoir 23. La partie principale 22 est montée sur le réservoir 23 de gaz par l'intermédiaire des deux axes 5. Plus particulièrement, la partie principale 22 est montée par coulissement sur ces axes 5 afin d'être raccordée au réservoir 23. Le montage par coulissement permet un déplacement de la partie principale 22 le long de ces axes 5 et un dégagement facilité de ladite partie principale 22 du réservoir 23 ainsi qu'un changement aisé de ladite partie principale 22 et/ou de la tuyère 13 et/ou 18 en fonction des besoins d'utilisation. . Sur chacun des supports principaux 1 et 2, se trouvent également, à 85 mm du centre desdits supports principaux 1 et 2, deux empreintes consacrées au logement d'un système de guidage 6 à roulement du hacheur 3. Ce système de guidage 6 évite toute déviation du hacheur 3 lorsque ce dernier est en rotation. Le réglage du guidage 6 est effectué par des vis micrométriques fixées sur les supports 1 et2 qui viennent pousser les montures des roulements, le contre rappel étant assuré par des ressorts. The hash system 21 is supported by the main portion 22 and includes a chopper 3, or disk or other means of alternative opening obstruction. Said main portion 22 is fixed on a reservoir 23, said reservoir being at the origin of the injection in the gas flow device or any other element to be pulsed. This main portion 22 consists of two main supports 1 and 2 rigid circular shape having for example a diameter of 340 mm and a thickness of 20 mm. These supports 1 and 2 are facing each other. In the case of a Laval nozzle, the respective centers of the main supports 1 and 2 are drilled to receive bases 12 and 19 containing the convergent and divergent profiles of the nozzles 13 and 18. At a distance of 90 mm from the centers of the supports 1 and 2, a bore 24 with a stop is machined to receive the bearings used for the rotation of the chopper axis 3. At 140 mm centers of the main supports 1 and 2, two holes are drilled, intended to receive Socket bearings 4 in which will be positioned two major axes 5 mounted on the reservoir 23. The main part 22 is mounted on the gas tank 23 via the two axes 5. More particularly, the main portion 22 is mounted by sliding on these axes 5 to be connected to the reservoir 23. The sliding assembly allows a displacement of the main portion 22 along these axes 5 and a facilitated clearance of said part pri ncipale 22 of the reservoir 23 and an easy change of said main portion 22 and / or the nozzle 13 and / or 18 depending on the needs of use. . On each of the main supports 1 and 2, are also, 85 mm from the center of said main supports 1 and 2, two cavities dedicated to the housing of a guide system 6 to roll the chopper 3. This guide system 6 avoids any deviation of the chopper 3 when the latter is rotating. The adjustment of the guide 6 is performed by micrometric screws fixed on the supports 1 and 2 which push the bearing mounts, the return against being provided by springs.
Les deux supports 1 et 2 sont montés face à face grâce à trois colonnes de positionnement 7)de 20mm de diamètre, lesdites colonnes 7 étant par exemple emboîtées dans les faces 25 des supports principaux respectivement 1 et 2 en vis- à-vis l'une de l'autre. Cet agencement permet le parallélisme et l'alignement entre les deux supports 1 et 2. La distance entre les deux supports 1 et 2 est minimisée pour optimiser la précision des réglages. Enfin, le support principal 2 dédié à la partie divergente de la tuyère 18 reçoit les fixations du moteur 8 entraînant le hacheur 3. Le hacheur 3 se présente sous la forme d'un disque 3. Le diamètre du hacheur 3 est de 240 mm, pour une épaisseur de 1 à 2 mm. Un trou oblong 26 de longueur d'arc variable et de diamètre 12 mm est agencé à 90 mm du centre du hacheur 3. Une découpe est réalisée sur un bord 27 opposé au trou oblong 26 par rapport au centre du hacheur 3. Cette découpe permet d'équilibrer le disque 3 malgré la présence du trou oblong 26. Ce maintien de l'équilibre évite le balourd et les vibrations du disque 3 à haute vitesse de rotation. Il est à préciser que toutes les côtes fournies ne sont qu'indicatives et dépendent évidemment du dimensionnement de l'installation et des performances désirées. Typiquement, le hacheur 3 est tel que l'axe de rotation dudit hacheur est parallèle à l'écoulement et ne passe pas par ledit écoulement. Le trou 26 du hacheur est situé à une distance du centre égale à une distance séparant le centre du hacheur 3 de l'écoulement du gaz. Cette distance est en effet adaptée pour assurer une mise en regard alternative du trou avec l'axe de l'écoulement. La découpe en bord dudit hacheur 3 est réalisée afin d'équilibrer la rotation du hacheur. La découpe est agencée à l'opposé du trou par rapport au centre du hacheur 3. The two supports 1 and 2 are mounted face to face thanks to three positioning columns 7) of 20 mm in diameter, said columns 7 being for example nested in the faces 25 of the main supports 1 and 2 respectively vis-a-vis the one of the other. This arrangement allows parallelism and alignment between the two supports 1 and 2. The distance between the two supports 1 and 2 is minimized to optimize the accuracy of settings. Finally, the main support 2 dedicated to the divergent portion of the nozzle 18 receives the fasteners of the motor 8 driving the chopper 3. The chopper 3 is in the form of a disc 3. The diameter of the chopper 3 is 240 mm, for a thickness of 1 to 2 mm. An oblong hole 26 of variable arc length and diameter 12 mm is arranged at 90 mm from the center of the chopper 3. A cut is made on an edge 27 opposite the oblong hole 26 relative to the center of the chopper 3. This cutout allows to balance the disk 3 despite the presence of the oblong hole 26. This maintenance of the balance avoids the unbalance and vibration of the disc 3 at high rotation speed. It should be noted that all the ribs provided are only indicative and obviously depend on the sizing of the installation and the desired performance. Typically, the chopper 3 is such that the axis of rotation of said chopper is parallel to the flow and does not pass through said flow. The chopper hole 26 is located at a distance from the center equal to a distance separating the chopper center 3 from the gas flow. This distance is in fact adapted to ensure an alternative look of the hole with the axis of the flow. Edge cutting said chopper 3 is performed to balance the rotation of the chopper. The cutout is arranged opposite the hole relative to the center of the chopper 3.
La figure 2 représente une vue en coupe transversale d'un dispositif selon l'invention Suivant le principe de fonctionnement rappelé ci-après, le hacheur 3 tourne entre la partie convergente (12,13) et divergente (18,19) de la tuyère. Pour éviter la rupture de profil qui conduirait à détruire les caractéristiques de l'écoulement, le hacheur 3 est de préférence mince et parfaitement plan. Le hacheur 3 peut être monobloc, en verre ou en céramique. Une autre solution est d'utiliser un disque 3 composés d'une partie métallique (Inox, Aluminium, ...) recouverte d'un dépôt de Téflon pur ou chargé, de PFA ou d'une matière composite, dont les propriétés sont un compromis entre bon coefficient de frottement et une importante tenue à l'usure. Dans certains cas, la solution d'un collage de plusieurs couches est à retenir car elle permet de cumuler les propriétés des constituants et d'éviter les déformations dues au procédé de dépôt. FIG. 2 represents a cross-sectional view of a device according to the invention. In accordance with the operating principle recalled below, the chopper 3 rotates between the convergent (12, 13) and divergent portion (18, 19) of the nozzle. . In order to avoid the profile breaking which would lead to destroying the characteristics of the flow, the chopper 3 is preferably thin and perfectly flat. The chopper 3 can be monobloc, glass or ceramic. Another solution is to use a disc 3 composed of a metal part (stainless steel, aluminum, ...) coated with a pure or filled Teflon deposit, PFA or a composite material, the properties of which are a compromise between good coefficient of friction and a high wear resistance. In some cases, the solution of a collage of several layers is remember because it allows to cumulate the properties of the constituents and to avoid the deformations due to the deposition process.
Sur la partie principale 22, le hacheur 3 est maintenu entre deux pièces cylindriques de fixation 9 et 10. Les deux pièces de fixation 9 et 10 sont alésées en leur centre. Un axe de transmission 1 1 coopérant avec le hacheur 3 est inséré dans ces alésages 9 et 10. Les alésages 9 et 10 et l'arbre 1 1 sont ajustés finement pour permettre la translation avec un jeu réduit de tout le hacheur 3 et autoriser le positionnement entre le convergent (12,13) et le divergent (18,19) de la tuyère, ainsi qu'un démontage facilité du système 21 de hachage. On the main part 22, the chopper 3 is held between two cylindrical fastening parts 9 and 10. The two fasteners 9 and 10 are bored at their center. A transmission shaft 1 1 cooperating with the chopper 3 is inserted into these bores 9 and 10. The bores 9 and 10 and the shaft 1 1 are finely adjusted to allow the translation with a reduced clearance of the whole chopper 3 and allow the positioning between the convergent (12,13) and the divergent (18,19) of the nozzle, and easy disassembly of the system 21 hashing.
Un premier élément, nommé socle convergent 12, comporte des griffes de serrage 28. Ces griffes de serrage 28 coopèrent avec le réservoir 23 afin d'assurer le montage de la partie principale 22 sur le réservoir 23. Le socle convergeant 12 comporte un logement complémentaire de la partie amont 13 de la tuyère, ledit logement est apte à recevoir ladite partie amont 13 de la tuyère. Ce mécanisme trouve son utilité lors du changement de tuyère car il est alors aisé de remplacer un profil sans démonter tout le système. Le socle convergent 12 s'insère dans le support principal 1 par l'alésage central et est fixé par vissage. Dans ce socle 12, on vient positionner la tuyère 13 qui sous l'effet de la pression amont et de ressorts de compression, vient se mettre en butée sur le socle convergent 12 assurant l'étanchéité entre le réservoir 22 et la chambre de détente grâce à un où deux joints 14 sur le plus petit diamètre de la partie amont de la tuyère 13. C'est au sein de la partie amont de la tuyère 13 qu'est embarqué le cœur du système d'étanchéité du dispositif. Un tel système d'étanchéité peut être comme décrit ci-après ou de n'importe quel type connu de l'homme du métier. Ce système d'étanchéité permet d'assurer une étanchéité dans le dispositif malgré la présence du hacheur 3 et assure ainsi que les conditions de pression et de débit ne soient pas perturbées par un défaut d'étanchéité. Le principe de base utilisé pour assurer une bonne étanchéité repose sur des joints 15, 16 et 20 en régime dynamique avec frottement, c'est-à-dire en contact avec le hacheur 3 en rotation tout en assurant une bonne étanchéité. La solution technique consiste à utiliser des joints mobiles 15, 16 et 20 se positionnant en butée sur le disque 3. Pour ce faire, on réalise, sur la partie amont de la tuyère 13 au plus près du profil, une empreinte destinée à recevoir une bague en bronze 17 sur laquelle sera monté le joint d'étanchéité principal 15.A first element, called a convergent base 12, has gripping claws 28. These clamping claws 28 cooperate with the reservoir 23 to ensure the mounting of the main portion 22 on the reservoir 23. The converging base 12 comprises a complementary housing the upstream portion 13 of the nozzle, said housing is adapted to receive said upstream portion 13 of the nozzle. This mechanism is useful when changing the nozzle because it is then easy to replace a profile without disassembling the entire system. The convergent base 12 is inserted into the main support 1 by the central bore and is fixed by screwing. In this base 12, it is positioned the nozzle 13 which under the effect of the upstream pressure and compression springs, abuts on the convergent base 12 ensuring the seal between the reservoir 22 and the expansion chamber through at one or two joints 14 on the smaller diameter of the upstream portion of the nozzle 13. It is within the upstream portion of the nozzle 13 that is embedded in the heart of the sealing system of the device. Such a sealing system can be as described below or any type known to those skilled in the art. This sealing system ensures a seal in the device despite the presence of the chopper 3 and thus ensures that the pressure and flow conditions are not disturbed by a leakage. The basic principle used to ensure a good seal is based on seals 15, 16 and 20 in dynamic regime with friction, that is to say in contact with the chopper 3 rotating while ensuring a good seal. The technical solution consists in using mobile joints 15, 16 and 20 positioned abutting on the disc 3. To do this, an impression is made on the upstream part of the nozzle 13 as close as possible to the profile, intended to receive a bronze ring 17 on which will be mounted the main seal 15.
Cette bague 17 porte le joint hacheur principal 15 en contact avec le disque 3.This ring 17 carries the main chopper seal 15 in contact with the disc 3.
Aussi, pour réduire les fuites indirectes par l'intérieur du logement de la bague 17, on adjoint sur son axe intérieur le joint hacheur secondaire 16. La force de contact, qui conditionne l'étanchéité et le moment de freinage appliqué sur le disque 3, est réglée par un jeu de ressorts de différentes rigidités. Also, to reduce indirect leakage from the inside of the housing of the ring 17, is added on its inner axis the secondary chopper seal 16. The contact force, which conditions the seal and the braking torque applied to the disc 3 , is regulated by a set of springs of different rigidities.
Une étanchéité est assurée dans la partie divergente de la tuyère de manière assez similaire à l'étanchéité décrite ci-dessus : elle intègre la partie divergente de la tuyère 18 et son socle 19 de fixation sur le support principal 2, suivant le même principe que précédemment. Dans ce cas, la tuyère 18 n'est pas mobile, elle est simplement fixée en butée sur le socle divergent 19 par vissage. Dans cette partie en aval du disque, les besoins d'étanchéité n'existent plus. Cependant, en position fermée, la différence de pression entre le réservoir et la chambre, conduit à l'application d'une force sur le hacheur qui peut alors se voiler. Le même type de joint mobile 20 que sur la partie amont de la tuyère est donc utilisé. A seal is provided in the divergent portion of the nozzle in a manner quite similar to the seal described above: it integrates the divergent portion of the nozzle 18 and its base 19 for fixing on the main support 2, according to the same principle as previously. In this case, the nozzle 18 is not movable, it is simply fixed in abutment on the divergent base 19 by screwing. In this part downstream of the disc, the sealing needs no longer exist. However, in the closed position, the pressure difference between the tank and the chamber, leads to the application of a force on the chopper which can then be veiled. The same type of mobile joint 20 as on the upstream part of the nozzle is used.
De plus, il est à noter l'installation sur la tranche du support principal 2 en face du hacheur 3, d'une pièce destinée à recevoir une fourche optique constituée d'un émetteur et récepteur infrarouge. Un orifice est percé sur le hacheur 3 face au capteur optoélectronique dans une position correspondante au début de l'ouverture de la tuyère. En fonctionnement, le signal recueilli est utilisé pour calculer la vitesse de rotation du disque 3. De manière générale, ce signal est exploité en tant que commande pilotant tout autre type de système synchronisé au Hacheur aérodynamique comme, par exemple, le déclenchement de tirs lasers. In addition, it should be noted the installation on the edge of the main support 2 opposite the chopper 3, a part for receiving an optical fork consisting of an infrared transmitter and receiver. An orifice is pierced on the chopper 3 opposite the optoelectronic sensor in a corresponding position at the beginning of the opening of the nozzle. In operation, the collected signal is used to calculate the rotational speed of the disk 3. In general, this signal is used as a control driving any other type of synchronized system to the aerodynamic chopper, such as, for example, the triggering of laser shots .
En fonctionnement, le réservoir 23 comporte un gaz sous pression à une certaine température. Ce réservoir 23 alimente la partie principale 22, et plus particulièrement la tuyère amont 13 avec un certain débit. Le hacheur 3 subit une rotation à haute fréquence. Cette rotation à haute fréquence du hacheur 3 alternativement libère et obstrue, à ladite haute fréquence, l'écoulement selon que le trou oblong 26 respectivement est ou n'est pas en vis-à-vis de l'écoulement. Cette obstruction à haute fréquence de l'écoulement par le hacheur 3, par exemple sur une plage de fréquences allant de 10 à 100Hz, permet d'obtenir un écoulement puisé tout en conservant les conditions de pression et de température du réservoir 23, le réservoir 23 n'ayant pas à avoir une taille réduite ni à être rempli en cours d'utilisation. Les exemples ci après donnent des exemples de valeurs et mesures de fonctionnement ou pouvant être obtenues par le dispositif selon l'invention. In operation, the reservoir 23 comprises a gas under pressure at a certain temperature. This reservoir 23 feeds the main part 22, and more particularly the upstream nozzle 13 with a certain flow rate. Chopper 3 undergoes a high frequency rotation. This high frequency rotation of the chopper 3 alternately releases and obstructs, at said high frequency, the flow according to whether the oblong hole 26 is respectively or opposite the flow. This high frequency obstruction of the flow by the chopper 3, for example over a frequency range from 10 to 100 Hz, makes it possible to obtain a pulsed flow while maintaining the pressure and temperature conditions of the reservoir 23, the reservoir 23 does not have to be small in size or filled during use. The examples below give examples of values and measurements of operation or obtainable by the device according to the invention.
Les premiers tests ont été réalisés en utilisant le profil d'une tuyère de Laval fonctionnant en mode continu avec les caractéristiques suivantes : une température moyenne d'écoulement de 24K sur une distance d'uniformité de 33 cm (196 μs), un débit instantané de 100 Standard litres/min, une pression de réservoir de 336 mbar et une pression de chambre de 0.63 mbar. Les essais réalisés à l'aide du hacheur aérodynamique ont permis de générer un écoulement puisé, stable sur une distance de 45 cm (266 μs) à la température de 22K, à une fréquence de pulsation allant jusqu'à 20 Hz pour des impulsions d'une durée de 8 ms. On peut constater que le passage au mode puisé (disque tournant à 10 Hz) a permis une réduction en débit de gaz d'un facteur 8 (de 100 S. I. m"1 en continu à 12 S. I. m"1 en puisé). Il est dorénavant possible de faire fonctionner cette tuyère avec une capacité de pompage de ~ 1300m3/h alors qu'elle nécessitait ~ 10 400 m3/h en CRESU continu. The first tests were carried out using the profile of a Laval nozzle operating in continuous mode with the following characteristics: an average flow temperature of 24K over a uniformity distance of 33 cm (196 μs), an instantaneous flow rate of 100 Standard liters / min, a tank pressure of 336 mbar and a chamber pressure of 0.63 mbar. The tests carried out using the aerodynamic chopper allowed to generate a pulsed flow, stable over a distance of 45 cm (266 μs) at the temperature of 22K, with a pulse frequency of up to 20 Hz for pulses d a duration of 8 ms. It can be seen that the switch to the pulsed mode (rotating disk at 10 Hz) allowed a reduction in gas flow by a factor of 8 (100 SI m- 1 continuous at 12 SI m- 1 in pulsed). It is now possible to operate this nozzle with a pumping capacity of ~ 1300m 3 / h whereas it required ~ 10 400 m 3 / h in continuous CRESU.
La figure 3 représente une comparaison de différentes techniques utilisées pour caractériser, en température, le jet puisé obtenu à l'aide du dispositif selon l'invention: FIG. 3 represents a comparison of different techniques used to characterize, in temperature, the pulsed jet obtained using the device according to the invention:
(Sur la figure 3, le zéro de l'axe des abscisses correspond à la sortie de la tuyère de Laval)  (In FIG. 3, the zero of the abscissa corresponds to the exit of the Laval nozzle)
• La courbe (a) illustre les résultats issus d'une simulation numérique de type résolution en temps des équations de Navier Stokes en 2-D pour ce profil de tuyère. • La courbe (b) expose les résultats issus de mesure de pression d'impact en tube de Pitot à différentes positions dans l'axe de la tuyère. La particularité de ces mesures Pitot émane du fait que chaque point de la courbe de pression d'impact est obtenu en prenant une valeur moyenne du maximum sur le plateau de courbes représentant l'impulsion de pression d'impact en fonction du temps, identique à celles des figures (e) et (f). • Curve (a) illustrates the results from a numerical simulation of the time resolution type of Navier Stokes equations in 2-D for this nozzle profile. • Curve (b) shows the results from the Pitot tube impact pressure measurement at different positions in the nozzle axis. The peculiarity of these pitot measurements arises from the fact that each point of the impact pressure curve is obtained by taking an average value of the maximum on the plateau of curves representing the pulse of impact pressure as a function of time, identical to those of Figures (e) and (f).
• Les points (c) représentent des mesures de température rotationnelle obtenues par spectroscopie du radical CN (étude de la distribution de population de la branche R du spectre) en fonction de la position de la tuyère.  • The points (c) represent rotational temperature measurements obtained by spectroscopy of the CN radical (study of the population distribution of the R branch of the spectrum) as a function of the position of the nozzle.
• Les points (d) représentent des mesures de température rotationnelle obtenues par spectroscopie du radical CN (étude de la distribution de population de la branche P du spectre) en fonction de la position de la tuyère.  • The points (d) represent rotational temperature measurements obtained by spectroscopy of the radical CN (study of the population distribution of the branch P of the spectrum) as a function of the position of the nozzle.
- Les graphiques (e) et (f) montrent des impulsions de pression d'impact à différentes positions (le temps en milliseconde est représenté en abscisse).  - Charts (e) and (f) show impulse pressure pulses at different positions (millisecond time is plotted on the abscissa).
La figure 4 montre un spectre rovibronique du radical CN obtenu par LIF (Laser Induced Fluorescence) et utilisé pour déterminer la température rotationnelle de l'écoulement. Figure 4 shows a rovibronic spectrum of the CN radical obtained by LIF (Laser Induced Fluorescence) and used to determine the rotational temperature of the flow.
Les résultats exposés démontrent un excellent accord entre le jet obtenu en mode puisé à partir du hacheur aérodynamique comparé à celui issu d'un écoulement CRESU classique. The results shown demonstrate an excellent agreement between the jet obtained in pulsed mode from the aerodynamic chopper compared to that from a conventional CRESU flow.
La qualité des écoulements obtenus par ce dispositif est excellente car bien établis sur des temps allant de la centaine de microseconde à la milliseconde. Elle peut même être supérieure au cas stationnaire par réduction des turbulences dans le réservoir. Diverses modifications peuvent être apportées au hacheur aérodynamique, en vue de son adaptation à une géométrie différente de celle d'une tuyère de Laval ou à des besoins de réduction en taille du système. La description donnée constitue une base à la solution technique et un exemple non limitatif par rapport aux côtes du système et aux matériaux utilisés. L'invention est un appareillage indépendant et compact qui se fixe sur le réservoir d'une installation globale, ce qui la rend facilement transportable et adaptable. The quality of the flows obtained by this device is excellent because well established over times ranging from a hundred microsecond to millisecond. It can even be superior to the stationary case by reducing turbulence in the tank. Various modifications can be made to the aerodynamic chopper, with a view to adapting it to a geometry different from that of a Laval nozzle or to reducing the size of the system. The description given constitutes a basis for the technical solution and a non-limiting example with respect to the ribs of the system and the materials used. The invention is an independent and compact apparatus that attaches to the tank of a global installation, which makes it easily transportable and adaptable.
Références : References :
[I ] Dupeyrat, G., J. B. Marquette, and B. R. Rowe, Design and testing of axisymmetric nozzles for ion molécule reaction studies between 20 K and 160 K. The Physics of fluids, 1985. 28: p. 1273-1279. [I] Dupeyrat, G., J. B. Marquette, and B. R. Rowe, Design and testing of axisymmetric nozzles for molecule reaction studies between 20 K and 160 K. The Physics of fluids, 1985. 28: p. 1273-1279.
[2] Smith, I.W.M. and B. R. Rowe, Reaction kinetics at very low températures: Laboratory studies and interstellar chemistry. Ace. Chem. Res., 2000. 33(5): p. [2] Smith, I.W.M. R. Rowe, Reaction kinetics at very low temperatures: Laboratory studies and interstellar chemistry. Ace. Chem. Res., 2000, 33 (5): p.
261 -268. 261-268.
[3] Amirav, A., U. Even, and J. Jortner, Absorption-Spectroscopy of Ultracold [3] Amirav, A., U. Even, and J. Jortner, Absorption-Spectroscopy of Ultracold
Large Molécules in Planar Supersonic Expansions. Chemical Physics Letters,Large Molecules in Planar Supersonic Expansions. Chemical Physics Letters,
1981. 83(1 ): p. 1 -4. 1981. 83 (1): p. 1 -4.
[4] J. E. KENNY, T.W., PULSED SLIT NOZZLE FOR GENERATION OF PLANAR[4] J. E. KENNY, T.W., PULSED SLIT NOZZLE FOR GENERATION OF PLANAR
SUPERSONIC JETS. US Patent, 1989. N° 4 834 288. SUPERSONIC JETS. US Patent, 1989. No. 4,834,288.
[5] Amirav, A., U. Even, and J. Jortner, Spectroscopy of the Fluorene Molécule in [5] Amirav, A., U. Even, and J. Jortner, Spectroscopy of the Fluorene Molecule in
Planar Supersonic Expansions. Chemical Physics, 1982. 67(1 ): p. 1 -6. Planar Supersonic Expansions. Chemical Physics, 1982. 67 (1): p. 1 -6.
[6] SUTO, PULSE NOZZLE. US Patent, 1994. N° 5 295 509  [6] SUTO, PULSE NOZZLE. US Patent, 1994. No. 5,295,509
[7] Okada, Y., et al., Cam-driven pulsed Laval nozzle with a large optical path length of 50 cm. Review of Scientific Instruments, 1996. 67(9): p. 3070-3072. [7] Okada, Y., et al., Cam-driven pulsed Laval nozzle with a large optical path length of 50 cm. Review of Scientific Instruments, 1996. 67 (9): p. 3070-3072.
[8] MARTIN, G., DEVICE FOR INJECTING A PULSED SUPERSONIC GAS [8] MARTIN, G., DEVICE FOR INJECTING AT PULSED SUPERSONIC GAS
STREAM. US Patent, 2006. N° 7 093 774 B2. STREAM. US Patent, 2006. No. 7,093,774 B2.
[9] Atkinson, D. B. and M. A. Smith, Design and Characterization of Pulsed Uniform Supersonic Expansions for Chemical Applications. Review of Scientific [9] Atkinson, D. B. and M. A. Smith, Design and Characterization of Pulsed Uniform Supersonic Expansions for Chemical Applications. Review of Scientific
Instruments, 1995. 66(9): p. 4434-4446. Instruments, 1995. 66 (9): p. 4434-4446.
[10] Berteloite, C, et al., Low température (39 K - 298 K) kinetics study of the reactions of C4H radical with various hydrocarbons observed in Titan's atmosphère.  [10] Berteloite, C, et al., Low temperature (39 K - 298 K) kinetics study of the reactions of C4H radical with various hydrocarbons observed in Titan's atmosphere.
Icarus, 194, (2), 746-757. (2008). Icarus, 2008. 194(2): p. 746-757.  Icarus, 194, (2), 746-757. (2008). Icarus, 2008. 194 (2): p. 746-757.
[I I ] Sims, I. R., et al., Ultra-low température kinetics of neutral-neutral reactions : The technique, and results for the reactions CN + O2 down to 13 K and CN + NH3 down to 25 K. J. Chem. Phys, 1994. 100(6): p. 4229-4241. [12] Chastaing, D., et al., Rate coefficients for the reactions of C(P-3(J)) atoms with C2H2, C2H4, CH3C=CHand H2C=C=CH2 at températures down to 15 K. Astron. Astrophys., 2001. 365(2): p. 241 -247. [II] Sims, IR, et al., Ultra-low temperature kinetics of neutral-neutral reactions: The technique, and results for the CN + O 2 reactions to 13 K and CN + NH 3 down to 25 KJ Chem. Phys, 1994. 100 (6): p. 4229-4241. [12] Chastaing, D., et al., Rate coefficients for the reactions of C (P-3 (J)) with C2H2, C2H4, CH3C = CHand H2C = C = CH2 and temperatures down to 15 K. Astron. Astrophys., 2001. 365 (2): p. 241 -247.

Claims

REVENDICATIONS
1. Dispositif d'écoulement puisé comportant 1. A pulsed flow device comprising
- Une injection continue de gaz dans le dispositif alimentée par un réservoir (23),  A continuous injection of gas into the device fed by a reservoir (23),
- un moyen d'obstruction (3) de l'écoulement,  a means for obstructing (3) the flow,
- le moyen d'obstruction étant combiné à un système d'étanchéité dynamique de manière étanche autour de l'écoulement,  the obstruction means being combined with a dynamic sealing system in a sealed manner around the flow,
caractérisé en ce que le moyen d'obstruction ouvre et ferme par obstruction l'écoulement à des fréquences élevées. characterized in that the blocking means opens and closes the flow at high frequencies.
2. Dispositif d'écoulement puisé selon la revendication 1 caractérisé en ce que le moyen d'obstruction est un disque mécanique rotatif ou à mouvement alternatif permettant d'ouvrir et de fermer l'écoulement. 2. A pulsed flow device according to claim 1 characterized in that the obstruction means is a rotating mechanical disk or reciprocating to open and close the flow.
3. Dispositif d'écoulement puisé de gaz selon la revendication 2 caractérisé en ce qu'un axe de rotation du disque ne passe pas par un axe découlement du flux, le disque comportant 3. A pulsed gas flow device according to claim 2 characterized in that an axis of rotation of the disk does not pass through a flow axis of the flow, the disk comprising
- un trou situé sur le disque à une distance du centre du disque égale à une distance séparant le centre du disque de l'axe d'écoulement,  a hole located on the disk at a distance from the center of the disk equal to a distance separating the center of the disk from the axis of flow,
- une coupe dans un bord dudit disque, ledit bord étant opposé au trou par rapport au centre du disque.  a cut in an edge of said disk, said edge being opposite to the hole relative to the center of the disk.
4. Dispositif d'écoulement selon la revendication 3 caractérisé en ce que le trou est de forme oblongue. 4. Flow device according to claim 3 characterized in that the hole is oblong.
5. Dispositif d'écoulement selon l'une des revendications précédentes caractérisé en ce que le système d'étanchéité dynamique comporte un joint principal, un joint secondaire, une bague amont et un joint compensant les variations de mouvement du hacheur garantissant les conditions de contact entre le hacheur et les composant mécanique profilant l'écoulement 5. Flow device according to one of the preceding claims characterized in that the dynamic sealing system comprises a main seal, a secondary seal, an upstream ring and a seal compensating the chopper movement variations guaranteeing contact conditions between the chopper and the mechanical components profiling the flow
6. Dispositif d'écoulement selon l'une des revendication précédentes caractérisé en ce que les géométries du système d'étanchéité dynamique et du moyen d'obstruction sont adaptées aux tuyères de Laval. 6. Flow device according to one of the preceding claim characterized in that the geometries of the dynamic sealing system and the obstruction means are adapted to Laval nozzles.
7. Dispositif d'écoulement selon l'une des revendications précédentes caractérisé en ce que les géométries du système d'étanchéité dynamique et du moyen d'obstruction sont adaptées aux tuyères de formes planaires et axisymétriques. 7. Flow device according to one of the preceding claims characterized in that the geometries of the dynamic sealing system and the obstruction means are adapted to the planar and axisymmetric nozzle shapes.
8. Dispositif d'écoulement selon la revendication 1 caractérisé en ce que le moyen d'obstruction est une plaque plane en mouvement alternatif. 8. Flow device according to claim 1 characterized in that the obstruction means is a flat plate reciprocating.
9. Utilisation d'un dispositif d"écoulement puisé de gaz selon l'une des revendication 1 à 8 pour protéger des fenêtres optiques. 9. Use of a pulsed gas flow device according to one of claims 1 to 8 for protecting optical windows.
10. Utilisation d'un dispositif d'écoulement puisée de gaz selon l'une des revendications 1 à 8 pour générer des écoulements à très basses températures. 10. Use of a pulsed gas flow device according to one of claims 1 to 8 for generating flows at very low temperatures.
EP10752083.5A 2009-07-24 2010-07-22 Aerodynamic chopper for pulsating a gas flow Not-in-force EP2456562B1 (en)

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FR0903663A FR2948302B1 (en) 2009-07-24 2009-07-24 AERODYNAMIC HOPPER FOR GAS FLOW PULSATION
PCT/FR2010/051557 WO2011018571A1 (en) 2009-07-24 2010-07-22 Aerodynamic chopper for gas flow pulsing

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