Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
  • G01N21/43—Refractivity; Phase-affecting properties, e.g. optical path length by measuring critical angle
  • G01N21/431—Dip refractometers, e.g. using optical fibres
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
  • G01F1/704—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow using marked regions or existing inhomogeneities within the fluid stream, e.g. statistically occurring variations in a fluid parameter
  • G01F1/708—Measuring the time taken to traverse a fixed distance
  • G01F1/7086—Measuring the time taken to traverse a fixed distance using optical detecting arrangements
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
  • G01F1/74—Devices for measuring flow of a fluid or flow of a fluent solid material in suspension in another fluid
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
  • G01F1/704—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow using marked regions or existing inhomogeneities within the fluid stream, e.g. statistically occurring variations in a fluid parameter
  • G01F1/708—Measuring the time taken to traverse a fixed distance
  • G01F1/712—Measuring the time taken to traverse a fixed distance using auto-correlation or cross-correlation detection means
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
  • G01N21/43—Refractivity; Phase-affecting properties, e.g. optical path length by measuring critical angle
  • G01N21/431—Dip refractometers, e.g. using optical fibres
  • G01N2021/432—Dip refractometers, e.g. using optical fibres comprising optical fibres
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/84—Systems specially adapted for particular applications
  • G01N21/85—Investigating moving fluids or granular solids
  • G01N21/8507—Probe photometers, i.e. with optical measuring part dipped into fluid sample
  • G01N2021/8528—Immerged light conductor
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2201/00—Features of devices classified in G01N21/00
  • G01N2201/02—Mechanical
  • G01N2201/021—Special mounting in general
  • G01N2201/0218—Submersible, submarine
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2201/00—Features of devices classified in G01N21/00
  • G01N2201/08—Optical fibres; light guides

Definitions

• the invention generally relates to systems for analyzing characteristic quantities of a biphasic flow and, more particularly, to an optical probe capable of providing signals making it possible to determine such quantities.
• the invention applies more particularly to a system capable of determining, among the characteristic quantities, at least the presence rate, the flow rate or the size of gas bubbles in a liquid phase or drops of a phase liquid in another liquid phase, (for example, drops of water in oil).
• a system capable of determining, among the characteristic quantities, at least the presence rate, the flow rate or the size of gas bubbles in a liquid phase or drops of a phase liquid in another liquid phase, (for example, drops of water in oil).
• the optical properties of the flowing medium are generally used to measure characteristic quantities of a biphasic flow.
• the corresponding devices generally comprise optical probes whose optical fibers are used as a light guide and which use the reflection and transmission properties through the interface between the two phases of the medium according to the value of their respective refractive indices.
• the probe ends with a conical tip intended for be arranged in the biphasic flow. When a bubble arrives on the end of the tip, the reflection conditions are changed due to the change in refractive index of the medium in contact with the tip.
• the index variation between a gas and a liquid is of the order of 30% (less for the liquid). As a result, in the presence of gas, a smaller amount of light emerges from the tip of the probe.
• the level of return light in the optical fiber is more important. Thanks to the conical shape, the luminous flux is concentrated at the end of the tip. It follows that a change of medium at the end of the tip results in a sudden change in the return light flux.
• a measuring device connected to the other end of the optical fiber makes it possible to detect this change and translate it into an electrical signal. The interpretation of this signal makes it possible to determine that the tip has passed through a bubble in the flow.
• FIG. 1 very schematically represents an example of a system using two probes 1 and 1 '.
• Each probe 1 comprises an optical fiber 11, 11 'of which a first end ⁇ is connected by an optical connector 12, 12' to a housing 2.
• This housing 2 comprises two light sources 21 and 21 'able to emit light from the two respective optical fibers 11 and 11 '.
• Two semi-transparent plates 22 and 22 ' are respectively associated with each light path so as to send back to photoreceptors 23 and 23' the flux reflected by each optical fiber.
• Each optical fiber 11, 11 ' receives at its end a tip 13, 13', for example glass, and sheaths 14 and 14 'generally surround the optical fibers 11 and 11 'leaving free spikes 13 and 13'.
• the tips 13 and 13 ' are intended to be placed in the biphasic flow to be measured.
• these tips are generally placed in a tube or duct 3 in which the fluid flows, the crossing of the wall of the duct being effected by the inter ⁇ mediates sealing elements 31 and 31 '.
• a processing device 4 for example of the microcomputer type provided with a central unit 41 and input / output peripherals (for example screen 42, keyboard 43, mouse 44, etc.).
• the two points 13 and 13 ' are placed on the same line of the flow whose direction is symbolized by an arrow F so that a gaseous bubble g reaching the first point 13' in the direction of flow has a high probability to then reach the second point 13.
• FIG. 2 illustrates, in the form of timing diagrams, an example of the appearance of electrical signals S 'and S provided by the photodetectors 23' and 23.
• a bubble g is "plugged" by the end of the tip 13 ', the only change in the light emerging from the tip is related to the change in the index of the medium between the liquid and the gas (the angle of attack of the light flux on the inside of the tip from the optical fiber remains unchanged) .
• the decrease in index between liquid form and gaseous form causes a sudden rise in the amount of light reflected and captured by the photodetector. This is reflected on the signal S 'by a slot of higher amplitude.
• the signals are processed by statistical autocorrelation algorithms to determine the velocity.
• the tips used are generally sapphire.
• Sapphire is preferred to glass tips bonded to the Extremists ⁇ moth optical fiber since it can be welded to the metal (and thus the sheath surrounding the optical fiber) while the glass tip which can only be bonded by a binder optics do not hold for high pressures and temperatures (over 80 ° C and over 0.5 MegaPascal).
• a sapphire tip is suitable for temperatures of several hundred degrees and pressures up to 15 to 20 megaPascals.
• optical probe capable of measuring the characteristic quantities of a biphasic flow and in particular the flow velocity, withstanding high pressures and high temperatures.
• an optical probe comprising an optical guide associated with a conical sapphire or diamond tip, circular base and having, between the base and the end, a annular groove with an O-ring bottom or at least one shoulder of revolution.
• the optical fiber is sheathed with a metal sheath to which the tip is held by welding.
• the width of said groove is between 20 and 50% of the height of the tip.
• the maximum depth of said groove is 10 and 50% of the diameter of the tip at this maximum depth.
• said groove is positioned approximately halfway up the tip.
• a cylindrical portion is present at the shoulder.
• the shoulder causes a section change of between 10 and 50% of the diameter at this shoulder.
• the optical guide is an optical fiber.
• the optical guide is an extension of the sapphire or diamond point.
• the tip is extended by a rigid cylindrical portion whose end is at one end of the optical fiber.
• a feature quantity determination method of slug flow exploiting a signal representative of a luminous flux reflected by an optical probe, comprising at least one step of deter mination ⁇ , to the appearance of a slot in this signal, the duration of a first step representative of the length of a section of the tip.
• said determination serves to obtain the flow velocity.
• knowledge of the speed and the total duration of the slot serves to determine the size of the bubble.
• a system for determining characteristic quantities of a biphasic flow comprising: at least one optical probe; at least one optical interface provided with means for emitting a luminous flux opposite the end of the optical guide opposite to the tip, and a photodetector of the luminous flux in return; and means for processing at least one signal provided by the photodetector.
• the system is applied to biphasic flows at high pressure or at high temperature.
• Figures 1 and 2 which have been described above are intended to expose the state of the art;
• Figure 3 is a schematic sectional view trans ⁇ versale of one embodiment of a tip of an optical probe;
• Figure 4 is a schematic representation of a measuring characteristic variables of a device flows ⁇ biphasic;
• Figs. 5A and 5B illustrate the operation of the device of Fig. 4;
• Fig. 6 is a cross-sectional view of another embodiment of a tip of an optical probe;
• FIG. 7 partially represents variant embodiments of a tip of an optical probe;
• Figure 8 shows another embodiment of a tip of an optical probe;
• FIG. 9 represents another embodiment of an optical probe in its functional environment; and
• Figure 10 shows a preferred embodiment of a tip of an optical probe.
• the same elements have been designated with the same refe ⁇ ences in the different drawings. detailed description
• FIG. 3 is a partial sectional view of an embodiment of a tip-side optical probe.
• FIG. 4 very schematically represents an embodiment of a system for determining characteristic quantities of a biphasic flow using a tip of the type of that illustrated in FIG.
• the probe comprises as previously an optical fiber 51 surrounded by a sheath 54 to an end ⁇ mité to which is reported a tip 53 intended to be in the presence of the biphasic flow to be measured.
• the other end (not shown in FIG. 3) of the optical fiber 51 is intended to be connected to an interface box 6 (FIG. 4).
• This housing comprises an optical source 63 placed opposite the departure of the optical fiber 51.
• a semireflective blade is placed on the path of the luminous flux.
• a focusing device (not shown) is interposed on the optical path.
• the return level of the light reflected by the semitransparent plate 62 is, if appropriate after the light has also been focused by a lens device (not shown), detected by a photo ⁇ receiver 61.
• This photoreceptor 61 is associated with a shaping circuit which delivers a signal S (for example a voltage) representing the characteristic phase variable of the ear ⁇ lement. This variable describes the biphasic flow and defines, at a given point and time, whether this point is in one phase or another.
• the signal S is used in the usual way by a digital processing system 4 (not shown in FIG. 4), for example a microcomputer.
• the tip 53 of the probe 5 has a particular shape in that it has, at a distance d1 from its free end 531, a shoulder 532 or a sectional change in its generally conical shape based on circular.
• This shoulder 532 separates an end or head portion 534 from the tip 53 of a portion or foot 536 whose circular base is attached to the end of the optical fiber 51.
• the angle OC of the cone is preferably the same. for the two sections 534 and 535 of the tip.
• the tip 53 is sapphire or diamond, which allows machining of the shoulder 532 of circular revolution. It benefits here to be able to machine sapphire or diamond despite the small diameter involved. Indeed, the diameter of the fiber 51 is a few hundred microns (for example between 200 and 800 microns).
• the probe 5 is placed in the biphasic flow (in the pipe 3) in the usual way by passing through a sealing element 31.
• the probe 5 is configured such that the axis 537 of the conical tip 53 is approxi ⁇ tively parallel to the direction (arrow F, Figure 4) of the flow, and that its free end 531 is oriented to face the direction of the flow.
• the fiber-tip interface is located inside the duct 3, and to withstand the high pressures and temperatures for which the optical probe is particularly intended, we take advantage of the possibility of welding the sapphire on a metal sheath 54 so that this sheath protrudes from the end of the optical fiber to surround the beginning of the base of the tip 53 and be welded peripherally thereto.
• the tip is held by an optical binder (e.g., an epoxy resin) between the end of the optical fiber and the base 536 of the sapphire.
• the gap between the free end 541 of the metal sheath and the shoulder 532 defines a second distance dO of the conical tip 53.
• This distance dO between the section change and the base of the tip (therefore the end of the optical fiber) or between this section change and the free end 541 of the sheath 54 does not influence the operation.
• the light is guided to the housing 6 by a sapphire or diamond extension of the tip.
• the optical guide is then in the form of a cylindrical sapphire or diamond rod whose end receives a connector of the housing (or an optical fiber) and the other end is shaped in tip.
• FIGS. 5A and 5B illustrate the operation of the tip of FIG. 3.
• FIG. 5A shows an example of the appearance of a voltage signal S supplied by the interface box 6 to the appearance of a gas bubble.
• Figure 5B schematically illustrates three successive positions of the gas bubble.
• the index change when the gas bubble is plugged (left situation of Figure 5B) by the end 531 of the end portion 534 of the tip 53, causes a sudden increase in the level of the signal S towards A first voltage V1.
• the shoulder 532 in the example, for a time T1
• the level remains approximately stable.
• the bubble g reaches the shoulder 532 (center position of FIG.
• the signal S then goes to a second higher level V2. As long as the tip remains in the bubble, the level of signal S remains approximately stable at level V2 (in the example, for a duration T2). As soon as the bubble g releases the end 531 of the tip (right situation of FIG. 5B), the level of the signal S becomes VO again.
• the level can only go back down to a level VO '(dashed in FIG. 5A) intermediate between the VO and Vl levels (closer to VO). However, this level will most often be assimilated to noise and filtered by the electronic measurement interpretation circuits, or even by the photodetector itself.
• the total duration T of the signal S slot represents the duration during which the tip is in the gas bubble.
• the first step Ml of the slot is present for a time T1 representative of the duration during which the bubble g is only plugged on the head 534 of the tip 53.
• the second step M2 is present for a duration T2 representing the duration during which the tip is in the gas bubble by its two sections.
• the difference in level h between the voltage levels V2 and Vl is a function of the importance e (FIG. 3) of the section change of the tip.
• the dimensions of the tip are chosen according to the average size of the bubbles expected in the flow. The tip must indeed be thin enough to "plug" the bubbles.
• a DC angle at the tip tip 53 between 10 and 30 ° (preferably between 15 and 20 °) is suitable for most applications.
• the angle CC does not need to be changed compared to the usual probes.
• a shoulder 532 causing a sectional change of between about 10 and 50% (preferably 20 to 40%) of the diameter of the conical tip at the shoulder allows correct interpretation in most cases. The lower this percentage, the more the signal S has a small difference in height h between steps Ml and M2, so may be polluted by noise.
• the exploitation of the total duration T of the slot in the voltage level S makes it possible to determine, by using the usual tools of statistical correlation and mathematical correction to pass from the measurement of a chord of a sphere to the determination of its diameter, the size of the gas bubbles.
• the distance d1 must be determined accurately and may, depending on the machining tolerances, require calibration. However, it is not a calibration in situation but a measurement of dimensions on the tip itself.
• the distance d0 does not matter. It is deduced from the distance dl, the diameter of the base of the tip, the angle at the apex of the conical shape and the depth of penetration of the point in the sheath 54.
• the distance dO will generally be more related to mechanical manufacturing constraints.
• An advantage of providing a shoulder of revolution (all around the tip) with respect to a single point notch is that it detects a bubble that is plugged by a rope near its periphery and that would risk otherwise not to cross the notch.
• a sapphire tip 53 may be made with the following dimensions: diameter of the base 536 corresponding to the diameter of the end of the optical fiber 51 of a few hundred micrometers, for example of the order of 400 micrometers; length d1 of the end section 534 of a few hundred micrometers (for example about 500 micrometers); distance e radius between the respective bases of the conical tip (width of the shoulder 532) of a few tens of micrometers (for example of the order of 20 microns); and Figure 6 partially shows another embodiment of a probe 5 'in which the tip 53' has, between its head 534 and 535 foot, a cylindrical portion 538 of constant diameter.
• Figure 7 partially shows a detail of a tip 53 'at the sectional change 532 to illustrate two variants.
• a first variant is at the shoulder 532 which, for machining reasons, can be non-abrupt but have a certain radius (for example from a few micrometers to a few tens of micrometers).
• a certain radius for example from a few micrometers to a few tens of micrometers.
• the free end 531 'of the section 534 is pointed rather than being rounded as in FIGS. 3 and 6.
• a rounded tip may be necessary for machining issues but an unbleached point 531' improves the resolution of the probe.
• the end radius 531 of the tip 53 of FIGS. 3 and 6 is a few tens of micrometers (for example, between 25 and 50 micrometers in size) with the dimensions given previously. .
• FIG. 8 shows another embodiment of a point 53 "having another change of section in its height, this second shoulder 532 'translating into another step in the signal S.
• a precise knowledge of the distance d2 between two shoulders 532 and 532 'and the measurement of the time between the two corresponding steps of the signal can replace the measurement from the end section 534. It is also possible to use the measurements related to the two sections (intermediate 534' and end 534). ), opening other routes inter ⁇ tation and the door to new applications and characteristic quantities measures.
• FIG. 9 represents another embodiment of an optical probe 5 'in its functional environment (line 3). For simplicity, the optical interface 6 and the processing system 4 have not been illustrated.
• the tip 53 is ⁇ bordered by a cylindrical portion 52 made of sapphire.
• a cylindrical sapphire solid rod is used, one end of which is machined in point form 53 (or one of its variants, for example 53 '53 "). cut to length sou ⁇ haempere and machined at one of its ends to form the tip 53.
• the 5 'probe thus comprises an optical fiber 51 at the end of which is inserted the cylindrical portion 52.
• the length of the cylindrical portion 52 Extending the tip is chosen so that the fiber-sapphire interface is outside the duct 3 in which the flow circulates.This makes it possible to deport the hot spot in the event of high temperatures.
• nde 5 can not be placed in a rectilinear section of the conduit 3. Either, as shown, we take advantage of a bend 33 of the conduit to introduce the probe. Either one of the end ports of the pipe is used. Note that, even with a probe of the other embodiments described, the base of the tip is directly reported to the Extremists ⁇ moth the optical fiber, the probe can be straight respecting the above conditions which allow the place approximately in the direction of flow.
• Sapphire is a preferred material over diamond because of its better transparency.
• the diamond can however be used but requires more energy to emit the light signal because it is slightly more opaque. It is now possible to measure characteristic quantities of a biphasic flow by means of a single single-fiber and monopoint probe by obtaining quantities of the type of flow velocity and bubble size. Another advantage is that the probe produced is compatible with high pressures and temperatures.
• Figure 10 shows a preferred embodiment of a sapphire or diamond tip 7 according to the present invention.
• the tip 7 of generally conical shape comprises, between its base 71 and its end 72, a groove 73 of revolution with an O-ring bottom 731.
• the base 71 of the tip 7 is attached to the end of the optical fiber 51 and is preferably sheathed at least at the level of the fiber-tip link.
• the optical guide consists of a cylindrical sapphire or diamond extension of the tip. This avoids the fiber-sapphire junction or postpones it out of the pipe 3. The hot spot is thus postponed.
• the groove is positioned approximately at mid-height of the tip, its width is between 20 and 50% of the length of the tip and its maximum depth is between 10 and 50% of the diameter of the tip at this maximum depth.
• the toric curved shape of the groove 73 improves the signal-to-noise ratio due to a better distribution of flux between the end 72 of the tip and the beginning 733 of the groove.
• the machining of such a ring groove is easier to achieve mechanically.
• the resting level of the interpretation signal S can be selected to match the majority phase (gas / liquid or liquid / liquid) and the direction of the created ⁇ Neaux can then be reversed.
• the choice of the dimensions of the tip depends not only on the type of biphasic medium which, as for the usual tips, conditions in particular the angle OC to obtain a usable signal, but also bubble sizes, and flow rate expected as well as circuits electro ⁇ niques used.
• the dimensional limits are Preci ⁇ cally related to machining constraints.
• the use of several probes can facilitate the statistical correlations performed to obtain the characteristic quantities of the flow.
• the biconical or grooved tip described can also be associated with conventional tips in a multi-point probe generally used to evaluate the turbulence of the flow. If several probes are used, the optical interface must of course be adapted or several interfaces must be used and the means of treatment must also be adapted to several signals. Such adaptations, however, do not pose any difficulty by drawing on the usual multisonde systems.

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• Life Sciences & Earth Sciences (AREA)
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• Analytical Chemistry (AREA)
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• General Health & Medical Sciences (AREA)
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• Measuring Volume Flow (AREA)

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• 2008
  • 2008-04-17 FR FR0852601A patent/FR2930342A1/fr not_active Withdrawn
• 2009
  • 2009-04-16 WO PCT/FR2009/050710 patent/WO2009138634A1/fr active Application Filing
  • 2009-04-16 EP EP09745953A patent/EP2271912A1/de not_active Withdrawn

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