WO2013009241A1 - Procédé de détection inédit et détecteur associé - Google Patents

Procédé de détection inédit et détecteur associé Download PDF

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Publication number
WO2013009241A1
WO2013009241A1 PCT/SE2012/050768 SE2012050768W WO2013009241A1 WO 2013009241 A1 WO2013009241 A1 WO 2013009241A1 SE 2012050768 W SE2012050768 W SE 2012050768W WO 2013009241 A1 WO2013009241 A1 WO 2013009241A1
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WO
WIPO (PCT)
Prior art keywords
electrode
crystal
mass
particles
frequency
Prior art date
Application number
PCT/SE2012/050768
Other languages
English (en)
Inventor
Vasile-Mihai MECEA
Original Assignee
G&M Norden Ab
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by G&M Norden Ab filed Critical G&M Norden Ab
Publication of WO2013009241A1 publication Critical patent/WO2013009241A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/02—Analysing fluids
    • G01N29/022—Fluid sensors based on microsensors, e.g. quartz crystal-microbalance [QCM], surface acoustic wave [SAW] devices, tuning forks, cantilevers, flexural plate wave [FPW] devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/02—Analysing fluids
    • G01N29/036—Analysing fluids by measuring frequency or resonance of acoustic waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/024—Mixtures
    • G01N2291/02408—Solids in gases, e.g. particle suspensions
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/04—Wave modes and trajectories
    • G01N2291/042—Wave modes
    • G01N2291/0426—Bulk waves, e.g. quartz crystal microbalance, torsional waves

Definitions

  • the present invention is related to an airborne device that can reveal the presence of a volcanic ash cloud or sandstorm.
  • Quartz Crystal Microbalance (QCM) technique it detects the erosion produced by the kinetic energy of the hard particles of the volcanic ash or sand.
  • QCM Quartz Crystal Microbalance
  • Quartz Crystal Microbalance is a very sensitive mass measuring device.
  • the very high mass sensitivity of 10 "9 g to 10 "12 g is explained by the very high intensity of the harmonic inertial field, developed at the surface of the quartz resonator during its vibration. This result was developed in the article whereIs quartz crystal microbalance really a mass sensor?”, published in ordinSensors and Actuators A, 128 (2006) 270-277".
  • QCM As a real-time mass sensing device, QCM was largely used as a particle detector.
  • US Pat. Nr. 4041768 describes a particle detector based o the QCM technique, where the deposition of the particles, contained in the ambient air, is produced using electrostatic precipitation.
  • US Pat. Nr. 5892141 describes a detector for particles contained in the exhaust of the vehicle engines. Here, particles, mainly soot, are deposited on the surface of a catalyst coated quartz crystal resonator. The deposition is performed using electrostatic precipitation. The analysis of the particles is performed by heating the crystal in an oxidizing atmosphere to oxidize the deposited particles.
  • US Pat. Nr. 4041768 describes a particle detector based o the QCM technique, where the deposition of the particles, contained in the ambient air, is produced using electrostatic precipitation.
  • US Pat. Nr. 5892141 describes a detector for particles contained in the exhaust of the vehicle engines. Here, particles, mainly soot, are deposited on the surface of a catalyst coated quartz crystal resonator. The deposition is performed using electrostatic precipitation. The analysis of the particles is
  • 6510727 B2 describes a particle detector, based on the QCM technique, where the deposition of the particle is performed by impaction and a movable aperture is used to distribute the particles evenly on the sensitive area of the quartz resonator.
  • US Pat. Nr. 4294105 describes a particle detector, based on the QCM technique, where the particles are entrapped by a mat-like deposition on the quartz surface.
  • US Pat. No. 3715911 describes a particle detector, based on the QCM technique, where the particles are captured by the sensing quartz crystal coated with a sticky material.
  • US Pat. Nr. 7168292 B2 describes a miniaturized system for particle exposure measurement. It is based on the QCM technique and thermophoresis is used for the particle deposition on the surface of the quartz resonator.
  • the conventional quartz crystal microbalance collect the particulate matter on the surface of the quartz resonator using electrostatic precipitation, thermophoresis, or jet-to plate impaction, either simple, or in combination with a sticky layer.
  • electrostatic precipitation thermophoresis
  • jet-to plate impaction either simple, or in combination with a sticky layer.
  • the quartz crystal requires frequent crystal cleaning and surface restoration. Such requirements for cleaning and resurfacing are impractical for the use in the field. It is therefore apparent that there is need for improvements for determination levels of air borne particles with the QCM technologies and adaptations to the specific needs of direct, real time measurements of potentially harmful levels of particles appearing in airstreams.
  • the present invention generally employs the QCM technique in a reversed mode. Instead of the deposition of the particulate matter on the quartz resonator surface, the erosion effect of the hard particles, for example contained in volcanic ash and sand, is employed. Hard particles are represented by silicon dioxide and aluminium oxide particles. These particles represent about 70% of the total particles contained in the volcanic ashes.
  • the invention relates to a real-time method of detecting airborne solid, hard particles. As a first the step, the method provides at least one Quartz Crystal
  • Microbalance (QCM) arrangement including at least one oscillating quartz crystal with attached electrodes.
  • the method further includes subjecting the QCM arrangement to an airstream including solid particles, while kinetically energized particles are admitted to eroding at least one electrode.
  • the eroded electrode mass is assessed and thereby directly or indirectly it can be determined if the electrode mass loss relates to a particle density harmful to a part of an airborne vehicle.
  • the method so described also provides for a determination of the particle density in an airstream containing solid hard particle with a general capacity of eroding solid materials.
  • the described QCM arrangement comprises a first operating oscillating quartz crystal with attached electrodes adapted to be impacted by the particle carrying airstream and a second reference oscillating quartz crystal with attached electrodes adapted to be shielded from exposure of the particle carrying airstream.
  • QCM arrangements described useful herein are based on oscillating quartz crystals, however the person skilled in this field would realize that the term “quartz crystal” be held equivalent with crystals of other materials such as langasite, langatite, gallium phosphate, lithium niobate and the similar.
  • methods and equipments to bring QCM arrangements into a suitable oscillation described with the present invention are also well known by the skilled person.
  • the present invention includes measuring the frequency of the operating crystal and the reference crystal and such measured value serve as a general basis for calculating and optionally displaying a real erosion mass loss value or the decrease in electrode thickness; and calculating and optionally displaying any of the rate of electrode mass decrease or the rate of electrode thickness decrease.
  • the inventive method comprises separately calculating the electrode mass loss of the operating crystal and the apparent mass change of the reference crystal, as a result of the temperature change, and calculating the erosion mass value.
  • the inventive method comprises measuring the difference of the frequencies and computing a reconstructed frequency value for calculating a real erosion mass value.
  • the inventive method comprises measuring the difference of the frequencies, converting the frequency difference to a voltage, comparing obtained voltage values to predetermined operating electrode mass loss values and calculating the decrease in electrode thickness and the rate of the electrode thickness .
  • the method can further comprise a step of increasing the velocity of the particle carrying airstream to obtain sufficiently kinetically energized particles.
  • the electrode material is adapted to the kinetic energy of the particles to become determined and it is conceivable within the inventive context to construe different eroding electrodes adapted to the nature of the particles to determine. It is also conceivable within all contexts of the present invention to obtain the electrode erosion with an erosion layer on the electrode which, not necessarily needs to be conductive, but is designed to generate a detectable mass loss when subjected to the hard energized particles. As an example, such an erosion layer may be coated on an electrode surface intended to face the airstream to be assessed.
  • the present invention relates to a detector capable of detecting the presence of airborne solid, hard particles.
  • the detector is generally suitable for performing any of the earlier described methods.
  • the detector includes a sensor generally comprising a first operating oscillating quartz crystal with attached electrodes adapted to be impacted by the particle carrying airstream and a second reference oscillating quartz crystal with attached electrodes adapted to be shielded from exposure of the particle carrying airstream.
  • the electrode of the first operating crystal erodes by the impact of the particle and the detector is capable of determining the loss of mass resulting from the electrode erosion.
  • the first and second crystal have matched frequency to temperature characteristics.
  • the senor has an aperture directing a particle carrying airstream to an electrode of the first operating crystal.
  • the senor has an air pumping mechanism for accelerating ambient air to a particle carrying airstream with so the particles become sufficiently kinetically energized
  • the erodible electrode of the first oscillating crystal preferably is made from a conductive material capable of being eroded when subjected to kinetically energized particles having a size range about 1 to 200 microns and comprising silicon dioxide, or other hard particles.
  • the erodible electrode is made of a conductive material having an erosion layer adapted to be impacted by the particle containing airstream to be assessed.
  • the skilled person can envisage a number of designs and materials for electrodes.
  • the erodible electrode comprises gold and the airstream comprises particles from volcanic ash or sand having a velocity exceeding 200 km/h
  • the presently invented detector is useful on an aircraft or an airborne vehicle for detecting the level of particularly harmful particles arriving from volcanic ash or sand which may have an immediately damaging impact on such vehicles.
  • Skilled artisans may readily cutline other advantageous applications of the invention as it conveniently in real-time give an accurate readout of solid airborne particles.
  • Fig. l is a schematic view of the airborne detector for volcanic ash and sand.
  • Fig.2. is a schematic view of the first alternative (A) for the measurement of the volcanic ash and sand.
  • Fig.3. is a schematic view of the second alternative (B) for the measurement of the volcanic ash and sand.
  • Fig.4. is a schematic view of the third alternative (C) for the measurement of the volcanic ash and sand.
  • Fig.5. is schematic view of the test system used to reveal the functionality of the airborne detector for volcanic ash and sand.
  • Fig.6. is a graph illustrating the experimental eroded mass produced by the impact of the volcanic ash collected from Eyjafjallajokull in Island during April-May 2010.
  • Fig.7. is a graph illustrating the response of the quartz sensor during an experiment performed in the wind tunnel.
  • the metallic electrode used with the examples of the present invention has a good adhesion to the quartz surface and can be several tens of microns in thickness, which is significantly larger than conventionally used electrodes. With the present studies a gold-based electrode is used, but many other materials are conceivable for the present applications. This provides a long life of the quartz sensor and a large total accumulated response
  • the mass of the electrode eroded by the impact of the hard particles can be calculated from the frequency change of the exposed quartz resonator using various approximative equations. As the mass removed by erosion is quite large, it is preferably calculated using the equation derived from the Energy Transfer Model, presented in the article "Loaded vibrating quartz sensors” published in “Sensors and Actuators A, 40 (1994) 1-27", hereby incorporated as a reference, in order to obtain a preferred accuracy that is not limited by the thickness of the quartz electrode.
  • f q is the frequency of the quartz resonator before erosion
  • f c is the frequency of the quartz resonator after erosion
  • rrif is the mass of the electrode eroded by the hard particles
  • m q is the mass of the quartz resonator.
  • This arrangement consists of a measuring crystal exposed to the erosion of the volcanic ash or sand and a reference crystal that is not exposed to erosion, but is subjected to the same temperature changes.
  • the detector consists of a sensing head 1 and a housing 4. Inside the sensing head 1 are located the measuring crystal 2 and the reference crystal 3. They are close in frequency and have matched frequency to temperature characteristics. An aperture in front of the measuring crystal electrode allows for the impact of the volcanic ash particles or sand during the flight.
  • the housing 4 contains the electronic circuitry 5.
  • Fig.2. is a schematic view of an alternative A for the measurement of the volcanic ash and sand.
  • the measuring crystal and the reference crystal are maintained in vibration using appropriate oscillators.
  • the frequency of the measuring crystal F M and the frequency of the reference crystal F R are measured independently with appropriate frequency counters.
  • the frequency of the measuring crystal will change as a result of the electrode erosion and temperature change.
  • the frequency of the reference crystal will change only as a result of the temperature change, with the same amount the temperature has influenced the frequency of the measuring crystal.
  • a total mass response M t can be calculated using the Energy Transfer Model.
  • the total mass response comprises the real mass response M r , due to erosion, and the apparent mass response M a , due to the temperature change.
  • the reference crystal will measure only the apparent mass M a , due to the temperature change. Out of the real mass M r is calculated the decrease of the electrode thickness by erosion. Finally, the rate of both real mass decrease and the thickness decrease are calculated in order to indicate the particle density of the volcanic ash cloud or sand.
  • Fig.3. is a schematic view of an alternative B for the measurement of the volcanic ash and sand.
  • the frequencies F M and F R from the two crystals are mixed together and the difference AF is obtained.
  • the frequency difference is measured by a single frequency counter. It is not dependent on the temperature when the two crystals have similar frequency to temperature characteristics. However, the frequency difference will change as a result of the electrode erosion.
  • the mass loss caused by erosion it is necessary to reconstruct the actual value of the measuring frequency. This can be accomplished by adding the current value of the frequency difference AF to the known initial value of the reference frequency F R . From the current value of the reconstructed measuring frequency FMR it is possible to calculate the real eroded mass M r , using the equation based on the Energy Transfer Model.
  • Fig.4. is a schematic view of an alternative C of the volcanic ash and sand detector.
  • the difference in frequency between the two crystals is converted into a voltage, using a frequency-to- voltage converter.
  • the resulting voltage is related to the mass eroded from the measuring crystal electrode.
  • This mass is further converted into a decrease of the electrode thickness.
  • the rate of erosion and the rate of the electrode thickness decrease is obtained using a derivative system. This alternative is appropriate for an analog output signal.
  • Fig.5. is a schematic illustration of the test system used to reveal the functionality of the airborne detector for volcanic ash and sand.
  • the ambient air is sucked through a funnel.
  • An air duct allow the introduction of short pulses of air containing volcanic ash, sand or other types of hard particles, like aluminium oxide.
  • a vacuum pump is used to suck air from the ambient.
  • the funnel is directing the air jet, with a certain velocity, towards the sensing crystal.
  • Fig.6 The result of a typical test is illustrated in Fig.6.
  • Fig.7. is an illustration of an experiment in the wind tunnel where the silver electrode of the quartz sensor was eroded by aluminium oxide particles with a size of 9 micron at an air speed of 590 km/h. The concentration of these particles was 1.12 mg/m 3 , lower than the
  • concentration range of the volcanic ash of 2 mg/m 3 to 4 mg/m 3 admitted, with restrictions, for the flight of the airplanes.

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)

Abstract

La présente invention concerne un détecteur et un procédé en temps réel permettant la détection de particules dures en suspension dans l'air sur la base de la technique microbalance à cristal de quartz (QCM). Selon l'invention, on utilise la capacité des particules à éroder une partie utilisable d'un agencement QCM pour les détecter.
PCT/SE2012/050768 2011-07-13 2012-07-03 Procédé de détection inédit et détecteur associé WO2013009241A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US201161507246P 2011-07-13 2011-07-13
SE1150667-2 2011-07-13
US61/507,246 2011-07-13
SE1150667 2011-07-13

Publications (1)

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WO2013009241A1 true WO2013009241A1 (fr) 2013-01-17

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3653253A (en) * 1970-01-05 1972-04-04 Thermo Systems Inc Aerosol mass concentration spectrometer
WO2000046584A2 (fr) * 1999-02-02 2000-08-10 Rupprecht & Patashnick Company, Inc. Dispositif de controle differentiel de masse particulaire avec systeme de correction intrinseque pour les pertes par volatilisation
US6189367B1 (en) * 1997-12-02 2001-02-20 Allan L. Smith Apparatus and method for simultaneous measurement of mass and heat flow changes
US20020103605A1 (en) * 2001-01-26 2002-08-01 General Electric Company Devices and methods for high throughput screening of abrasion resistance of coatings
EP2431957A1 (fr) * 2010-09-16 2012-03-21 The Boeing Company Systèmes et procédés de détection précoce d'approche aérienne d'un fumée volcanique

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3653253A (en) * 1970-01-05 1972-04-04 Thermo Systems Inc Aerosol mass concentration spectrometer
US6189367B1 (en) * 1997-12-02 2001-02-20 Allan L. Smith Apparatus and method for simultaneous measurement of mass and heat flow changes
WO2000046584A2 (fr) * 1999-02-02 2000-08-10 Rupprecht & Patashnick Company, Inc. Dispositif de controle differentiel de masse particulaire avec systeme de correction intrinseque pour les pertes par volatilisation
US20020103605A1 (en) * 2001-01-26 2002-08-01 General Electric Company Devices and methods for high throughput screening of abrasion resistance of coatings
EP2431957A1 (fr) * 2010-09-16 2012-03-21 The Boeing Company Systèmes et procédés de détection précoce d'approche aérienne d'un fumée volcanique

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