Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
  • G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
  • G01K11/20—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using thermoluminescent materials

Definitions

• the present invention relates to a laser source optical method and device for the non-intrusive measurement of the temperature in a flowing liquid.
• Laser source measuring devices are already used, for example that of application EP 345188, based on the observation of interference fringes created inside a fluid flowing in a pipe, at the outlet of two optical fibers transporting light from an external laser source
• patent application FR 2 579 320 describes a measurement method by ultrasonic wave intended for the thermal monitoring of nuclear reactors. This technique only allows knowledge of only one parameter of the fluid, namely its temperature
• the inventors turned to optical methods, and in particular to a laser-induced fluorescence method already studied in the laboratory by the inventors to determine the concentration of a fluid and the principle of which is recalled below.
• Fluorescence physical phenomenon known for many years, is the consequence of deactivation of an excited state of a fluorescent species to a ground state by spontaneous emission
• the excited state can be induced by a laser radiation having a wavelength coincides with the absorption spectrum of the fluorescent species
• the time between absorption and emission of a photon is of the order of a few nanoseconds, which makes the technique applicable to the study of rapidly variable phenomena. temporal resolution can reach a few tens of kHz
• the intensity of fluorescence can be expressed by the relation
• I fluo K-opt K sp ec CV c I 0 e "/ where K op V c , I 0 , C, are respectively, the coefficient characterizing the optical chain, the volume of collection of fluorescence photons, the laser intensity incident, the molecular concentration of the fluorescent tracer K spec and? are constants depending only on the characteristics of the molecule used as fluorescent tracer The application of this principle makes it possible to obtain the temperature in simple situations where the volume, the concentration and the laser intensity are well controlled or remain constant
• the concentrations of each of the two tracers must be controlled
• the emission spectra of the two tracers must be sufficiently separated, in order to be able to separate the fluorescent emissions from each of the tracers using a set of interference filters which is difficult to achieve in practice
• the two-color fluorescence method according to the invention uses ultra-fast photophysical principles in relation to phenomena of electronic transition and collisional deactivation and not the kinetics of a chemical reaction induced by irradiation
• the response time of the technique is considerably improved
• French patent application FR 2 484 639 is also known.
• the method described in this document is an intrusive method since it requires the presence of sensors at various measurement locations, while the method according to the invention is a non-intrusive method.
• the fluorescent material used is a solid state material (page 8 lines 2-3) while the tracer according to the invention is a tracer in molecular solution in the liquid whose temperature is measured
• the Patent Abstract of Japan is also known from the summary provided, the method consists of seeding in fluorescent particles and not in a tracer in molecular solution, and uses irradiation in UV light and not laser radiation.
• the invention consists of an optical method for the non-intrusive measurement of the temperature of a flowing liquid, characterized by the use of fluorescence induced by laser radiation in a measurement volume of the liquid, and characterized in that it consists in using a single fluorescent tracer sensitive to temperature and at least two separate spectral detection windows on this same tracer, after molecular dilution of said tracer in said liquid medium
• the method preferably comprises the following steps reception of the optical signal and elimination of any diffusion or reflection of the excitatory laser component, separation of the optical signal into several light signals, creation of a detection window on each light signal obtained after the previous separation, amplification of said light signals collected in the detection windows and transformation of these into as many electrical signals, acquisition, processing and display of the previous electrical signals
• the invention also consists of a device for the non-intrusive measurement of the temperature of a flowing liquid by using fluorescence induced by laser radiation in a liquid measurement volume, characterized in that it is designed for setting up opens the method according to the invention and in that it mainly comprises a single reception channel with
• a holographic band rejection filter a set of separation of the optical signal into two light signals on each optical measurement channel "a filter to create a measurement window
• an amplifier device to amplify and transform light signals into electrical signals
• laser radiation is chosen from the whole (single laser beam, double laser beam, laser sheet)
• the filter creating the measurement window can be chosen from the set (interference filter, bandpass, high pass filter, low pass filter)
• an interferential band pass filter of bandwidth ⁇ L, crossed by the first signal, centered on a wavelength ⁇ ⁇ has been chosen and, for a second measurement channel, a pass filter high crossed by the second signal allowing the optical intensity to pass from a threshold wavelength ⁇
• Rhodamine B (C 28 H 31 CN 2 O 3 ) It is reputed to be particularly sensitive to temperature In addition, the temperature sensitivity of this tracer is different depending on the spectral band of the fluorescence spectrum considered
• the invention proposes according to a first example of use a single plotter and two separate spectral detection windows on the same plotter
• the resulting sensitivity of the method as used in the invention is of the order of 2% variation in the fluorescence signal per ° C, which, taking into account the signal-to-noise ratio observed, leads to precision on the temperature below 1 ° C
• the detection is therefore done on two pre-defined spectral windows and not on the study of complete spectra, which does not require the use of spectrometer, but only simple photodetectors (photodiodes , photomultipliers, CCD cameras)
• the inventors have produced a device (1) based on the fluorescence induced by laser radiation (2) in a measurement volume (3) of a flowing liquid and allowing the separation of the signals and their detection
• the laser radiation can be in the form of one or two laser beams, or even a laser sheet.
• the use of two laser beams intersecting a point defining the measurement volume allows a joint measurement of the speed at using a commercial bicycle chain
• the device mainly but not limited to
• a holographic filter (6) rejecting a band making it possible to eliminate any scattering or reflection of the exciting laser component (12) * A set of separation (4) of the optical signal (5) into at least two light signals, equal or not ( 5a, 5b) for example two, by means of two neutral separators (4a, 4b) to be defined according to the desired power on each "On each optical measurement channel:
• a filter which can be a band pass interference filter, a high pass or low pass filter to create a measurement window suitable for the tracer used
• HERE Rhodamine B in solution in ethanol
• An interference filter (7) pass band crossed by the signal (5a) and allowing to obtain the first measurement window (10) visible on the graph of the figure (2)
• the filter (7) is centered on a wavelength K ⁇ ⁇ ⁇ i, preferably 530 n ⁇ 5nm -
• a high pass filter (8), crossed by the second signal (5b) and letting the optical intensity pass from a wavelength ⁇ 2 threshold, preferably ⁇ 590 nm approximately -
• the essential criterion for choosing wavelengths is to have different temperature sensitivities
• the windows and wavelengths are chosen according to the temperature response curve of the tracer , or of the tracer-solvent mixture Cost criteria may also be involved in the choice of filters.
• the term "window" is understood in its general sense, a window being able to be composed of one or more interven wavelength ranges, bounded or not, the same term
• “Distinct” does not exclude any partial overlapping or the inclusion of windows and the expressions “measurement window” or “detection window” have equivalent meaning •: • An amplifying device (9a, 9b) for amplifying and transforming the light signals (5a, 5b) into electrical signals for example a photomultiphcator, a photodiode, a CCD sensor These amplifying devices ensure the precise measurement, with a short response time, of the fluorescence intensities "A computer system (11), with software It receives the electrical signals by an acquisition system, not shown, processes them and displays the results on a screen
• K is a constant depending only on the optical chain used and on the spectroscopic properties of the molecule used as a fluorescent tracer This ratio has the advantage of being independent of the concentration of fluorescent tracer, of the exciting laser intensity, and of the excited fluorescent volume
• the device constant (K) is determined by a simple initial calibration point at a known temperature T 0
• the equation (E,) is thus transformed
• the concentration of the liquid or the measurement volume can be obtained simultaneously (3)

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)
• Measuring Temperature Or Quantity Of Heat (AREA)

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• 2000
  • 2000-03-09 FR FR0003005A patent/FR2806159B1/fr not_active Expired - Fee Related
• 2001
  • 2001-03-12 US US10/239,683 patent/US7059766B2/en not_active Expired - Fee Related
  • 2001-03-12 EP EP01913981A patent/EP1269132A1/de not_active Withdrawn
  • 2001-03-12 WO PCT/FR2001/000723 patent/WO2002073145A1/fr active Search and Examination

Non-Patent Citations (1)

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