FR3007138A1 - DEVICE FOR ANALYZING A FLOW - Google Patents

Abstract

The invention relates to a device (1) for analyzing a flow (2) of liquid particles emitted by an injector (9) into an enclosure (3), comprising a device (5, 6, 18) for capturing an image of the stream. The invention is suitable for a test bench of a fuel injector. The device (1) for analysis comprises in particular a lighting member (7) generating a beam (8) for illuminating a space in the enclosure including the flux (2) of particles, the member (7) the illumination beam (8) is emitted to the image-capturing member (5, 6, 18) through the particle stream (2) and is attenuated by the particles and so that the captured image is representative of a spatial distribution of particles in the stream (2).

Description

The technical field of the present invention is that of the analysis devices used in the field of fluid mechanics and in particular the test benches for injectors.

GB-1411165 teaches a system for visualizing a gas flow by means of liquid bubbles dispersed and floating in the gas stream. This system is however not suitable for controlling a jet of droplets in a gaseous medium.

The patent application WO-03/019200 describes a method of visualizing a stream of liquid particles injected into a chamber delimited by a transparent cylinder and a transparent piston. This method is however particularly complex in its implementation as well as in its use. The present invention aims to overcome the disadvantages of the prior art by providing a flow analysis device whose implementation and use can be simplified. This objective is achieved by means of a device for analyzing a flow of liquid particles emitted by an injector into an enclosure, comprising at least one member for capturing at least one image of the flow, characterized in that it comprises at least one lighting member generating a lighting beam 25 of a space in the enclosure including the stream of particles at least in part, the lighting member being arranged so that said lighting beam is emitted to the image capturing member through the particle stream and is attenuated by the particles and so that said captured image is representative of a spatial distribution of the particles in the stream. According to another feature of the invention, said lighting member is disposed vis-à-vis said image capture member. According to another feature of the invention, said image-capturing member is arranged so that its central viewing axis is oriented perpendicularly to the central diffusion axis of the injector. According to another feature of the invention, the enclosure comprises a first transparent wall through which said image is captured and a second transparent wall through which is emitted said light beam. According to another feature of the invention, the field of vision of said image pickup member is inscribed entirely in said illumination beam. According to another feature of the invention, said image capture member covers the entire width of the stream, said captured image being representative of the overall shape of the stream. According to another feature of the invention, said image capturing member and said lighting member are controlled so as to capture a plurality of successive images representative of a mean spatial distribution in the steady-state flow. According to another feature of the invention, the captured successive images are in the form of digital files making it possible to establish for each point of captured images, an average value representative of the average spatial distribution characterized by at least one internal cone and an outer cone when the particle stream is in the form of a hollow conical spray. According to another feature of the invention, said captured image covers an area of sufficiently small diameter and depth to allow visualization of the shapes of several particles in the stream. According to another feature of the invention, said image capturing member and said lighting member are controlled so as to capture two successive images representative of the speed of the particles in the stream. According to another particularity of the invention, said image-capture member is fixed on a mobile carriage with respect to the enclosure, so as to move, in the flow, the zone where said captured image is in focus. According to another particularity of the invention, the analysis device is adapted for a test bench for analyzing the injection of fuel by said injector. According to another feature of the invention, the analysis device comprises a member generating, in the chamber, a flow of air flowing in the direction of the flow of liquid particles. A first advantage is that the flow analysis device can be implemented easily.

Another advantage of the flow analysis device lies in the fact that it can be used in collaboration with computer image processing systems. Yet another advantage of the flow analysis device is that it also makes it possible to carry out sufficiently accurate measurements for the validation of the fuel injectors and in particular the jet injectors for reactors. The validation of the fuel injectors in the reactors indeed requires sufficiently precise measurements to deduce spatial characteristics of the spray produced by the injectors including particle size and particle velocities in a hollow conical spray. Yet another advantage of the flow analysis device lies in the fact that the precision of the measurements made and the low cost of its use allow significant developments on the injectors in order to model the combustion phenomena in the chambers in a thorough manner. and to control the performance of these injectors. This is done for the purpose of increased control of the combustion quality, especially in aircraft engines. One can thus face many economic and ecological constraints met in the field of the development of the injectors. Other features, advantages and details of the invention will be better understood on reading the additional description which will follow of embodiments given by way of example in relation to drawings in which: FIG. diagram in section, in front view, of the analysis device; FIG. 2 represents a sectional diagram, with a view to the above of the analysis device of FIG. 1; FIG. 3 represents an image captured using a lens with a wide field of view; FIG. 4 represents controls of the lighting and image capture elements for capturing several successive images; - Figure 5 schematically shows a treatment of several successive images for the calculation of the average occupation of space by the particles in the stream; FIG. 6 shows the average representation of the occupation of space by the particles in the flow; FIG. 7 represents an image captured using a lens whose field of view is narrow; FIG. 8 shows controls of the lighting and image capture members 10 for capturing two successive images; FIG. 9 schematically represents a treatment of two successive images for calculating the velocities of the particles in a determined space of the flow; FIG. 10 shows the velocities of the particles in a determined space of the flow. The invention will now be described in more detail. The same references are used to designate the same elements. The analysis device 1 shown in FIG. 1 corresponds to a test bench of a fuel injector 9. The injector 9 tested may be an injector of the type used in a turbine. The stream 2 of liquid particles emitted in the chamber 3 is analyzed during a period when the overall shape of the flow is stable at steady state. Some analyzes can also be performed on an unstable flow or during its establishment. The enclosure 3 comprises lateral walls 12, an upper wall 10 and a lower wall 11. The injector 9 of 30 liquid particles is fixed to its control box 14 secured to the upper wall 10. The upper wall 10 is perforated to allow the generation of a stream of air in the chamber 3 flowing in the same direction as the direction of the particles of the stream 2. The air stream symbolized by double arrows is generated by a fan 16 rotated by A control unit 17. A management module 15 transmits, via a communication interface and a communication line, a command C17 for starting or stopping the fan, to its control box 17. The air flow allows in particular to approach the air circulation conditions in the combustion chamber. The bottom wall 11 is also perforated and is disposed above a member 13 for discharging the liquid particles. The fog, in the bottom of the chamber 3, resulting from a stream 2 of particles can thus be evacuated, while the air flow makes it possible to keep it in the bottom of the enclosure 3. It is of course expected safety systems suitable for fuel experiments such as accidental leak detectors. The injector 9 is controlled by its control unit 14, itself controlled by the management module 15. The management module 15 transmits, via a communication interface and a communication line, a control C14 of the injector relating in particular to the injection duration, the injection temperature and the injection pressure. D14 data representative of the injection parameters, including in particular the actual pressure, the flow rate and the injection temperature, are transmitted back to the management module 15. The liquid particles of the stream 2 are injected in the form of a cone centered around a central axis A37 of the injector 9. Transparent walls 4 are provided at the side walls 12 of the enclosure 3. A homogeneous illumination beam 8 is emitted through one of the walls 4 transparent while images are captured through the other transparent wall. For this purpose a lighting member 7 is disposed outside the enclosure in front of a transparent wall 4 to illuminate the flow inside the enclosure. Image capturing members are also disposed outside the enclosure 3 in front of a transparent wall 4 to visualize the flow inside the enclosure 3. A calibration step prior to the Use can be made during which the image capturing member views the light beam in the absence of liquid particle streams. In FIG. 1, the analysis device 1 comprises two image-capturing members each associated with a lighting member: an image capture member with a large field of view Z33 associated with a lighting member 7 to diodes and an image capture member Z30 narrow field of view associated with a lighting member 39 comprising a laser source. The wide-field image capture member is one in the form of a camera 5 equipped with a wide-field lens Z33 directed towards a mirror 38 deviating its field of vision Z33 to the stream 2 to inside the enclosure 3. The lighting member 7 associated with the wide-field image capture member Z33 comprises illumination elements such as diodes associated with a diffuser. The illumination elements are distributed over an extended surface in which the wide field of view Z33 is entirely projected. The wide field of view Z33 is thus inscribed in the lighting beam generated by the associated lighting member 7. The narrow-field image-capturing member is in the form of a camera 6 equipped with an objective lens 22 with a narrow field of view Z30 directed towards a mirror 18 deviating its field of vision Z30 towards the stream 2 to 1. The illumination member 39 associated with the narrow field image capturing member Z30 comprises illumination elements such as a laser source associated with a diffuser. The illumination elements are distributed over a restricted surface and generate a narrow luminous paintbrush 8 in which the narrow field of view Z30 entirely fits.

The mirrors can be controlled according to different positions including an active position where the field of vision is in the associated light beam and an inactive position where the camera is disabled for security. The two simultaneously controlled mirrors disable one of the image capturing members while the other is active. The image capture members are oriented towards the inside of the enclosure. The central axis A35 of capture of the wide-field camera Z33 is perpendicular to the central axis A37 of the injector 9. The wide-field camera 5 can capture an image covering a structured part L29 of the spray showing its overall shape. cone. Part L29 structured spray is for example between 5cm and 15cm, for example 10cm.

The central axis A36 of the capture of the narrow-field camera Z30 is perpendicular to the central axis A37 of the injector 9. The image-acquisition axes A35 and A36 are moreover directed towards the transparent wall 4 by which the light beams are emitted. The image capturing members 10 are arranged vis-à-vis the lighting member. The lighting member 7 or 39 projects its illuminating beam 8 towards one of the image-capturing members, through the stream 2 of particles. One of the beams picked up during an image capture by one or other of the cameras is thus attenuated by the particles. The captured images are also each representative of a spatial distribution of particles in the stream 2. The liquid particles of the stream can also be seen with the naked eye through the transparent walls. The management module 15 transmits, via a communication interface and a communication line, an image capture command C 50 to the wide-field camera 5, which returns data D 51 representative of a captured image. The management module 15 similarly transmits, via a communication interface and a communication line, an image capture command C60 to the narrow-field camera 6, which returns data D61 representative of a captured image. . The management module 15 transmits, via a communication interface and a communication line, a lighting control command C20, this command being transmitted to a control box 20 of the diodes or of the laser source. The cameras are fixed relative to the speaker 3 at times when one or more images are captured. The cameras 5 and 6 are for example fixed on a support 23 integral with the enclosure 3. The narrow-field camera 6 covers a zone Z30 of restricted diameter but also of restricted depth.

The sharpness field is indeed set for a restricted depth of field, for example of the order of 0.5mm to 1.5mm, and for example of lmm. To move this image capture zone Z30 in a movement L28 parallel to its image-capturing axis A35, the camera 6 is displaced along its axis of vision, by means of a carriage 26 movable in translation relative to the support 23. A linear displacement of the camera 6 makes it possible, for example, to linearly move the capture zone Z30 and to produce sectional views in the stream 2.

The management module 15 transmits, via a communication interface and a communication line, a command C27 for moving or stopping the carriage 26. After a position adjustment of the carriage, the management module 15 controls a type of illumination C20 simultaneously with C60 and C50 image capture commands. The images can be captured continuously, the lighting member being controlled to produce flashes to freeze the movement of the drops on the captured images. The management module 15 comprises a communication bus 20 in connection with its communication interfaces and also connected to a processing component 25 and a storage component 19. The management module is furthermore connected by a communication interface and a communication link, with a display screen 34. The management module 25 includes in particular high-speed control and acquisition interfaces and a high-speed storage memory 19. In FIG. 2, it can be seen that the wide field of view Z33 encompasses the flux over its entire width for the diameters referenced 31 and 32. The diameter referenced 32 corresponds to the image capture edge by the wide-field camera 5. The diameter referenced 31 corresponds to the diameter of the flow at the central capture axis A36 of the narrow-field camera 6. The narrow light beam 8 such as a laser brush completely encompasses the reduced area Z30 of image capture by the narrow-field camera 6. The brush has for example a diameter of a few millimeters, such as 5mm. The reduced area Z30, captured by the narrow-field camera 6, is arranged in the center of the stream. This zone Z30 can be moved in particular to the border of stream 2 or to its central axis A37. FIG. 3 represents an image captured by the large field camera Z33 with vision. Drops appear darker than others in less dense areas or in open areas of the enclosure. The emitted flash makes it possible to freeze the drops on the captured image D51. The spray is substantially cone-shaped. The drops at the outlet of the injector, at the top of the image, are arranged more densely than in the part of the spray opposite the injector, at the bottom of the image. Figure 4 shows a synchronized control of the lighting member and the camera 5 with a large field of view. In FIG. 4, the activation of the flashes corresponds to the high state of the slots C20. In addition, the image captures correspond to the high state of the C50 slots. As can be seen in FIG. 4, the illumination times cover each image capture time. A flash has a duration between 100ns and lps. The flashes have for example each a duration of 500ns. Several image captures are made successively. These commands are generated by the management module, when executing a large-field processing program 70 stored in memory 19, as shown in FIG. 5. The received images are stored successively in memory in the form of D51, D52 and D5N files. The number N of captured images can be set as needed. After storing the captured images, the wide-field processing program 70 performs a calculation of the average intensity for each point of the captured images. A file 71 representative of a new image is thus generated in memory. This new image can be displayed on a screen, as shown in FIG. 6, but it will advantageously be used to realize different measurements of the characteristics of the stream, by different image processing. As seen in Figure 6, the flow fits into a cone. The boundary between the outside part of the cone and the blackened cone can easily be determined by image processing. This image, which allows external vision of the spray in its deployed and stabilized part, allows, thanks to an image processing, the determination of the spray angles and the overall speed field. In addition, a thinning task appears in the cone. This thinning task can be delimited by an image processing taking into account, in particular, the intensity gradients. Thus the internal cone, almost unoccupied by the injected particles, can be determined, that is to say that the internal angle of the spray can be determined. A calculation program according to the inversion of Abel is for example used. Advantageously, for the generated average image 71, the data obtained are statistically reliable. Figure 7 shows an image captured using the narrow-field camera 6. The field of view is for example of diameter between 1 mm and 15 mm, for example 5 mm, the average diameter of a droplet being for example between 5pm and 100pm, and for example 50pm. The droplets in the sharpness field are apparent while the other droplets in front of or behind the Z30 sharpness area are blurred and do not appear on the captured D61 image. Thus thanks in addition to the reduced diameter, the contours of the droplets are apparent. The shapes and dimensions of the droplets can be advantageously analyzed. The spaces between particles also make it possible to determine a local spatial distribution of the spray. Figure 8 shows the controls of the narrow-field camera 6 in synchronization with the lighting member. Two C60 commands for capturing images approximated in time are controlled at the same time as two flashes to freeze the drops in their movement at the moments of the image taking. The activation of the flashes corresponds to the high state of the slots C20. Furthermore, the image captures 35 correspond to the high state of the slots C60. As can be seen in FIG. 8, the illumination times cover each image capture time. A flash has a duration between 10ns and 100ns. The flashes have for example each a duration of 5Ons.

These commands are generated by a stored narrow-field processing program 72, as shown in FIG. 9. The two captured images D61 and D62 are stored successively in memory 19. After the storage of these two images, the processing program 72 Narrow field performs a processing of the stored data to generate a file 73 including vectors for moving the droplets from one image to another. The shapes of each droplet are in particular recognized from one image to another and each displacement vector is calculated and recorded in memory. Displacement vectors appear as white lines on the image 73 shown in FIG. 10. This image can be viewed on a screen but the data of the motion vectors can also be used for further processing. The measurement of displacements makes it possible in particular to determine the speeds, thanks in particular to a memorized time separating the two image captures. Even if the droplet motions are disturbed by random components, the computation of the velocities remains just from a static point of view when the capture time between two images is sufficiently short. In addition, the time between two narrow-field image captures must be long enough to observe a droplet movement. To further increase reliability, the speed calculation data can also be averaged over several observations each including the storage of a pair of successive images. The maximum capture time between two images depends in particular on the injection pressure and the arrangement of the injector. Various tests make it possible in particular to calibrate the program 72 for localized calculation of speeds. The comparison of two successive large-field images makes it possible, in the narrow field, to determine velocity fields but only at the periphery of the spray, by means of a particle image velocimetry program, also designated in FIG. English by PIV (Picture Image Velocity), this program does not perform a shape recognition of the droplets. We can therefore determine a distribution according to the sizes and speeds of the droplets. It should be obvious to those skilled in the art that the present invention allows other embodiments. Therefore, the present embodiments should be considered as illustrating the invention.

Claims (13)

REVENDICATIONS1. Device (1) for analyzing a flow (2) of liquid particles emitted by an injector (9) in an enclosure (3), comprising at least one member (5, 6, 18) for capturing at least one image of the flux, characterized in that it comprises at least one lighting member (7) generating a beam (8) for illuminating a space in the enclosure enclosing the flux (2) of particles at least in part the illumination member (7) being arranged so that said illumination beam (8) is emitted to the image-capturing member (5, 6, 18) through the flow (2) of particles and is attenuated by the particles and so that said captured image is representative of a spatial distribution of particles in the stream (2). 2. Device (1) for analysis according to claim 1, characterized in that said lighting member (7) is disposed vis-à-vis said member (5, 6, 18) of image capture. 3. Device (1) for analysis according to one of the preceding claims, characterized in that said member (5, 6, 18) of image capture is arranged so that its central axis (A35, A36) for viewing is oriented perpendicularly to the central axis (A37) of diffusion of the injector (9). 4. Device (1) for analysis according to one of the preceding claims, characterized in that the enclosure (3) comprises a first transparent wall (4) through which said image is captured and a second wall (4) transparent through which is emitted said beam (8) lighting. 5. Device (1) for analysis according to one of the preceding claims, characterized in that the field of view of said image capture member is inscribed entirely in said lighting beam. 6. Device (1) for analysis according to one of the preceding claims, characterized in that said member (5) for image capture covers the entire width of the stream (2), said captured image (D51) being representative of the overall shape of the flow (2). 7. Device (1) for analysis according to the preceding claim, characterized in that said member (5) for image capture and said member (7) lighting are controlled to capture several successive images (D51, D52 , D5N) representative of a mean spatial distribution in steady-state flow (2). 8. Device (1) for analysis according to the preceding claim, characterized in that the successive images captured (D51, D52, D5N) are in the form of digital files for establishing for each point captured images (D51, D52, D5N), an average value representative of the mean spatial distribution characterized by at least one inner cone and one outer cone when the particle stream is in the form of a hollow conical spray. 9. Device (1) for analysis according to one of claims 1 to 5, characterized in that said captured image (D61) covers an area of diameter and depth restricted enough to allow viewing of the shapes of several particles in the flow (2). 10. Device (1) for analysis according to the preceding claim, characterized in that said member (5) for image capture and said member (7) lighting are controlled so as to capture two successive images (D61, D62 ) representative of the particle velocity in the flow. 11. Device (1) for analysis according to claim 8 or 9, characterized in that said member (5) for image capture is fixed on a movable carriage (26) relative to the enclosure (3), to move in the stream (2) the area (Z30) where said captured image (D61) is focused. 12. Device (1) for analysis according to one of the preceding claims, characterized in that it is suitable for a test bench for analyzing the fuel injection by said injector (9). 13. Device (1) for analysis according to one of the preceding claims, characterized in that it comprises a member (16, 17) generating, in the chamber, a flow of air flowing in the direction of flow ( 2) liquid particles.