WO2001063255A2 - Mesure de la concentration de la masse d'un aerosol et du taux de distribution de la masse - Google Patents

Mesure de la concentration de la masse d'un aerosol et du taux de distribution de la masse Download PDF

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Publication number
WO2001063255A2
WO2001063255A2 PCT/US2001/005948 US0105948W WO0163255A2 WO 2001063255 A2 WO2001063255 A2 WO 2001063255A2 US 0105948 W US0105948 W US 0105948W WO 0163255 A2 WO0163255 A2 WO 0163255A2
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WIPO (PCT)
Prior art keywords
sensor
particles
mass concentration
sampling
volume
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PCT/US2001/005948
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English (en)
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WO2001063255A3 (fr
Inventor
Frederick M. Shofner
F. Michael Ii Shofner
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Shofner Engineering Associates, Inc.
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Application filed by Shofner Engineering Associates, Inc. filed Critical Shofner Engineering Associates, Inc.
Priority to AU2001245329A priority Critical patent/AU2001245329A1/en
Priority to AU2001278131A priority patent/AU2001278131A1/en
Priority to PCT/US2001/024183 priority patent/WO2002009574A2/fr
Priority to US10/499,473 priority patent/US20050066968A1/en
Publication of WO2001063255A2 publication Critical patent/WO2001063255A2/fr
Publication of WO2001063255A3 publication Critical patent/WO2001063255A3/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
    • G01N15/02—Investigating particle size or size distribution
    • G01N15/0205—Investigating particle size or size distribution by optical 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
    • G01N21/47—Scattering, i.e. diffuse reflection
    • G01N21/49—Scattering, i.e. diffuse reflection within a body or fluid
    • G01N21/53—Scattering, i.e. diffuse reflection within a body or fluid within a flowing fluid, e.g. smoke
    • G01N21/534—Scattering, i.e. diffuse reflection within a body or fluid within a flowing fluid, e.g. smoke by measuring transmission alone, i.e. determining opacity
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
    • G01N2015/0042—Investigating dispersion of solids
    • G01N2015/0046—Investigating dispersion of solids in gas, e.g. smoke

Definitions

  • the invention relates to electro-optically measuring the mass concentrations and controlling the mass deliveries of aerosolized powders transported in conduits by gas flows .
  • Aerosol photometers are available which respond to low aerosol concentrations, typically in the range of 20 to 200 mg/m 3 , as with the Handheld Aerosol Monitor, HAM, manufactured by ppm, Inc, Knoxville, Tennessee, USA. Such photometers are not available for the 5 to 50 fold higher concentrations required for certain pharmaceutical manufacturing applications.
  • electro-optical devices could be constructed, as either light scattering mode or light extinction mode sensors, and could have certain advantages of simplicity and large sampling volumes. Unfortunately, the readings of such devices would be fundamentally and heavily dependent upon the characteristics of the aerosols being measured, notably particle size distribution. It follows that photometer readings alone are not and cannot be generally useful for mass concentration measurements as applied to production processes.
  • Embodiments of the invention enable the accurate and precise measurement of the mass concentrations of relatively fine (mean diameter approximately one to ten microns) aerosolized powders at relatively high concentrations (approximately 1 to 10 grams/m 3 (mg/L) , or higher) . Further, as a practical matter, embodiments of the invention enable such measurements in view of real world variabilities in mean particle size, concentration and nonuniformities across the transport cross section within transport conduits.
  • a method for measuring mass concentration of aerosols being transported in a gas flow stream.
  • the method includes employing a first sensor responsive to particles within a relatively larger sampling volume within the gas flow stream to develop an uncompensated output signal representative of mass concentration but uncompensated for particle size distribution.
  • the relatively larger sampling volume has the capacity to contain a plurality of particles.
  • the method also includes employing a second sensor responsive to particles within a relatively smaller sampling volume within the gas flow stream to develop a compensating signal representative of particle size distribution, the relatively smaller sampling volume being sized so as to contain only one particle larger than a predetermined minimum size.
  • the method further includes the step of determining mass concentration by applying the compensating signal to compensate the uncompensated output signal for particle size distribution.
  • a corresponding system for measuring mass concentration of aerosols being transported in a gas flow stream.
  • the system comprises a first sensor responsive to particles within a relatively larger sampling volume within the gas flow stream to develop an uncompensated output signal representative of mass concentration but uncompensated for particle size distribution.
  • the relatively larger sampling volume has the capacity to contain a plurality of particles.
  • the system additionally includes a second sensor responsive to particles within a relatively smaller sampling volume within the gas flow stream to develop a compensating signal representative of particle size distribution.
  • the relatively smaller sampling volume is sized so as to contain only one particle larger than a predetermined minimum size.
  • the system additionally includes an analysis device operable to determine mass concentration by applying the compensating signal to compensate the uncompensated output signal for particle size distribution.
  • a method for measuring mass concentration and particle size distribution of aerosols transported in a conduit, based on light scattering from multiple scattering volumes.
  • the method includes the step of transporting aerosols to a measurement position in the conduit.
  • the method further includes the step of employing illumination, optical collectors and detectors to define a plurality of sampling volumes at the measurement position, such that the scattered light response for each of the sampling volumes is maximal inside and minimal outside the particular volume, and with the largest sampling volume being generally concentric with and enclosing the smallest sampling volume, and with the smallest sampling volume size based on the expected range of mass concentrations and particle size distributions to be measured.
  • the sampling volume sizing determination is to choose the smallest volume so that individual responses are produced for minimum particle diameters in the lower end of the relatively larger particle diameter range expected.
  • the method additionally includes the steps of producing light scattering signal responses in proportion to collected scattered light from individual relatively larger particles within the sampling volumes, and producing light scattering signal responses in proportion to collective scattered light from a plurality of relatively smaller particles within the sampling volumes.
  • the method further includes the steps of analyzing the signal responses from each of the multiple and generally- concentric sampling volumes and determining by ratio and time coincidence criteria whether the individual responses from the multiple sampling volumes are valid, and processing the valid individual particle signals to produce mass concentration contribution and particle size distribution measurements for those particles larger than the minimum diameter; analyzing the signal responses from each of the multiple and generally concentric sampling volumes and determining the mass concentration contributions from the plurality of relatively smaller particles below the minimum diameter; combining the relatively larger particle and relatively smaller particle contributions; and computing and presenting measurement results of total mass concentrations in particle size distributions in relation to calibration results on similar aerosols .
  • a corresponding system for measuring mass concentration and particle size distribution of transported aerosols based on light scattering from multiple scattering volumes includes a conduit within which aerosols are transported to a measurement position.
  • the system additionally includes illumination, optical collectors and detectors defining a plurality of sampling volumes at the measurement position, such that the scattered light response for each of the sampling volumes is maximal inside and minimal outside the particular volume, and with the largest sampling volume being generally concentric with and enclosing the smallest sampling volume, and with the sampling volume size based on the expected range of mass concentrations and particle size distributions to be measured.
  • the sampling volume sizing determination is to choose the smallest volume so that individual responses are produced for minimum diameter particles in the lower end of the relatively larger particle diameter range expected.
  • the detectors produce light scattering signal responses in proportion to collected scattered light from individual, relatively larger particles within the sampling volumes, and the detectors produce light scattering signal responses in proportion to collected scattered light from a plurality of relatively smaller particles within the sampling volumes .
  • the system additionally includes an analysis system operable to analyze the signal responses from each of the multiple and generally concentric sampling volumes and determine by ratio and time coincidence criteria whether the individual responses from the multiple scattering volumes are valid, and to process the individual particle signals to produce mass concentration contribution and particle size distribution measurements for those particles larger than the minimum diameter; analyze the signal responses from each of the multiple and generally concentric sampling volumes and determine the mass concentration contributions from the plurality of relatively smaller particles below the minimum diameter; combine the relatively larger particle and the relatively smaller particle contributions; and compute and present measurement results of total mass concentrations and particle size distributions in relation to calibration results on similar aerosols.
  • a method for measuring mass delivery rate of aerosols being transported in a gas flow stream.
  • the method includes the steps of measuring volumetric flow rate within the gas flow stream, measuring mass concentration, and multiplying the measured volumetric flow rate by the determined mass concentration to determine mass delivery rate.
  • the step of measuring mass concentration includes employing a first sensor responsive to particles within a relatively larger sampling volume within the gas flow stream to develop an uncompensated output signal representative of mass concentration but uncompensated for particle size distribution.
  • the relatively larger sampling volume has the capacity to contain a plurality of particles.
  • the step of measuring mass concentration further includes employing a second sensor responsive to particles within a relatively smaller sampling volume within the gas flow stream to develop a compensating signal representative of particle size distribution.
  • the relatively smaller sampling volume is sized so as to contain only one particle larger than a predetermined minimum size at a time.
  • the step of measuring mass concentration further includes determining mass concentration by applying the compensating signal to compensate the uncompensated output signal for particle size distribution.
  • the step of measuring mass concentration includes employing a sensor responsive to a plurality of small particles and to individual, relatively larger particles within a sampling volume within the gas flow stream to develop compensated signals representative of particle size distribution and total aerosol concentration.
  • a corresponding system for measuring mass delivery rate of aerosols being transported in a gas flow stream includes a flow rate sensor for measuring volumetric flow rate within the gas flow stream, a mass concentration measurement system, and a device for multiplying the measured volumetric flow rate by the determined mass concentration to determine mass delivery rate.
  • the mass concentration measurement system includes a first sensor responsive to particles within a relatively larger sampling volume within the gas flow stream to develop an uncompensated output signal representative of mass concentration but uncompensated for particle size distribution.
  • the relatively larger sampling volume has the capacity to contain a plurality of particles.
  • the mass concentration measurement system additionally includes a second sensor responsive to particles within a relatively smaller sampling volume within the gas flow stream to develop a compensating signal representative of particle size distribution.
  • the relatively smaller sampling volume is sized so as to contain only one particle larger than a predetermined minimum size at a time.
  • the mass concentration measurement system additionally includes an analysis device operable to determine mass concentration by applying the compensating signal to compensate the uncompensated output signal for particle size distribution.
  • the mass concentration measurement system includes a sensor responsive to a plurality of small particles and to individual, relatively larger particles within a sampling volume within the gas flow stream to develop compensated signals representative of particle size distribution and total aerosol concentration.
  • FIG. 1 is a schematic representation, generally corresponding to a top plan view but partly sectioned, of an electro-optical mass concentration and mass delivery rate particle measurement embodiment of the invention
  • FIG. 2 is a side elevational view, taken on line 1-1 of FIG. 1;
  • FIG. 3 is an enlargement of the sampling volume of the embodiment of FIGS . 1 and 2 ;
  • FIG. 4 is a plot depicting extinction mode detector response to particles of various sizes within a sampling volume;
  • FIG. 5 is a top view of another electro-optical measurement embodiment of the invention, employing two scattering-mode sensors;
  • FIG. 6 is an elevational view of the embodiment of FIG. 5;
  • FIG. 7 is a top view of another electro-optical measurement embodiment of the invention, employing scattering-mode and extinction mode sensors;
  • FIG. 8 is a side elevational view taken on line 8-8 of FIG. 7;
  • FIG. 9 is an end view taken generally on line 9-9 of FIG. 7, detailing generally concentric but unequal light scattering volumes
  • FIG. 10 is an enlarged view to better show overlapping sensing volumes
  • FIG. 11 shows plots of detector responses for particles moving on an trajectory through a point near the center of the small ellipsoid volume of FIG. 10;
  • FIG. 12 shows plots of detector responses for particles moving on a trajectory through a l/e boundary point of the small ellipsoid volume of FIG. 10;
  • FIG. 13 shows plots of detector responses for particles moving on a trajectory outside the large ellipsoid volume of FIG. 10. Best Modes for Carrying Out the Invention
  • dM/dt 15 total mass flow rate, dM/dt in grams/second. Summation or integration over time yields mass delivery M in grams in time T. Significantly, dM/dt so measured is dependent only on aerosol properties, including their spatial and vector velocity distributions, as well as on conduit size, but not
  • anerosol is a generic term which refers to finely divided liquid and dry powder materials, such as “atomized” sprays and “fluidized and dispersed” powders, respectively.
  • atomized sprays
  • fluidized and dispersed powders, respectively.
  • To “aerosolize” a bulk liquid or powder generally means to break up the bulk material into small particles and to disperse them into a fluid medium, usually gaseous, for transport.
  • Aerosolization is a key component of the aerosol generation and transport aspects of the embodiments disclosed in WO 00/58016.
  • respirable therapeutic aerosols are preferably of the order of a few ⁇ m, or smaller than about 10 ⁇ m, in order to reach the deep, alveolar recesses of the lungs.
  • the therapeutic aerosol size range is between 10 ⁇ m and 100 ⁇ m for collection by or deposition within the bronchia. The size range is greater than 100 ⁇ m for nasal collection.
  • Aerosols are transported across a transport plane within a conduit by gas having a volumetric flow rate of Q in m 3 /second. According to the above assumptions, the aerosol mass delivery rate across the transport plane obeys, in the simple scalar but useful approximation :
  • FIGS. 1 and 2 represent a basic electro-optical sensor 200 for mass concentration and particle size distribution measurements employing light scattering.
  • the sensor 200 effects mass concentration and particle size distribution measurements of aerosol particles 208 transported through inlet and outlet conduits 10 and 12 in a gas flow stream Q s 15. Except for the extinction mode sensor elements consisting of detector 230 and signal processing electronics, symbolized by output V e ⁇ t 232, near forward light scatter mode sensors constructed and operated according to such designs are standard products manufactured by ppm, Inc. of Knoxville, Tennessee, USA. The addition of extinction mode sensor evolved from our discoveries and investigations into the measurement and control of mass deliveries, as disclosed herein. A series of standard ppm scatter mode sensors, known as "TX Sensors,” was originally developed for airborne concentration and particle size distribution (PSD) measurements in the field of human and animal exposures to toxic aerosols.
  • PSD concentration and particle size distribution
  • Mass fractions are a form of particle size distribution results wherein the cumulative fractions of mass larger than a given particle diameter are reported.
  • FIGS. 1-3 described next below with reference to FIGS. 1-3 is the operation of a single scatter mode sensor in the measurement of mass concentration and particle size distribution, as applied to mass delivery measurement and control.
  • a light source 202 such as a light emitting diode or a laser diode, directs a beam of light through beam-forming optics 204 to a beam focal volume 206 (as distinguished from a focal point) .
  • the beam focal volume 206 is defined by its minimum transverse width or waist 206, seen more clearly in the FIG. 3 enlargement.
  • This optical configuration is known as a near forward light scattering system, or scatter mode sensor, and is used in embodiments of the invention to provide mass concentration C information about the aerosols transported in conduit 10, across transport plane 34, and as represented by the light scattering or sensing volume 50.
  • the fraction of the transport plane 34 covered by the projection of the sensing volume 50 onto it is very small, approximately 1%, which, for purposes of embodiments of the invention, is atypical of other light scattering instruments.
  • projection of the sensing volume onto the transport plane we mean that maximum area of the scattering volume 50 projected onto the transport plane 34 in projection directions that are normal to the transport plane 34 or parallel to the local flow velocity vector associated with transport flow 15.
  • this very small projected "proxy point" area as a fraction of the total transport plane 34 area, is satisfactory, in other applications, especially for measuring mass deliveries, the small proxy point representation yields insufficient representation of the rest of the particle transport across transport plane 34, and solutions to this nonrepresentative sampling are enabled by embodiments of the invention disclosed herein.
  • volumetric flow rate sensor 250 seen in FIG. 2 operates within the transport conduit 10 and must be representative of the total flow Q s 15 which transports the aerosol across transport cross section 34.
  • Volumetric gas flow rate Q sensor 250 is preferably physically near the transport plane 34.
  • the volumetric gas flow sensors 250 is a venturi flow sensor operating as follows : sensor 255 senses differential pressure developed between throat tap 252 and wall tap 258 of venturi section 253, which taps are connected to differential pressure sensor 250 by tubes 254 and 256. This differential pressure reading is related to the volumetric flow rate Q s flowing into venturi inlet 251.
  • C and Q are measured simultaneously and at the same thermodynamic and fluidynamic conditions.
  • volumetric flow rate Q can be measured elsewhere in the system, the readings are always adjusted to correspond to provide actual volumetric flow at the thermodynamic and fluidynamic conditions at the location of the mass concentration C sensors.
  • CCM 400 Control and Communications Module 400, shown in FIG. 1.
  • Volumetric flow sensor 250 output 261 and scatter mode sensor output 213, along with other inputs, are received by CCM 400, which may a microcontroller, such as HC 11 manufactured by Motorola.
  • Output results of mass concentration, particle size distribution, or mass delivery rates are produced. (Extinction mode sensor output V e ⁇ ⁇ - 232 and its use are discussed below.)
  • CCM 400 also controls the system via output ports 263.
  • CCM has further I/O interfaces with one or more process computers 402.
  • the wavelengths are in the visible or near infrared range, from 400 to 1200 nanometers, with 800 to 1000 being typical, as provided with LEDs or diode lasers.
  • electro-optical components such as illumination, optical elements, detectors, and the like are almost ideally suited for aerosols that are "micron-sized" or about 1000 nanometers in volume mean diameter.
  • Light scattered 209 from aerosol particles 208 within beam focal volume 206 is collected by collection optics 210 and focused or imaged onto an optical detector 212.
  • the detector 212 is behind an aperture 214.
  • the aperture 214 typically is a few tens to a few hundreds of micrometers in diameter.
  • the size of the aperture 214 controls the optical collection volume 216 or waist 216.
  • the detector 212 is typically slightly larger than the limiting aperture 214.
  • a beam dump 218 in the form of a solid disc in front of the collection optics 210.
  • the collection optics 210, optical detector 212, aperture 214 and beam dump 218 together comprise a collection optical system 219.
  • a sampling volume V s 50 is defined by the intersection of the beam focal volume 206 and optical collection volume 216, near the waists for both.
  • sampling volume V s 50 Significant scattered light 209 can only originate within the sampling volume V s 50. Axial response is limited by the absence of particles 208, assured by purge air Q p 17, or by the axial response of the collection optical system 219.
  • Sampling volume V s 50 is shown as a cross-hatched area in FIG. 3 and is sometimes referred to as the "response ellipsoid.”
  • the size of the sampling volume V s 50 is a critical design parameter, as explained more fully below.
  • the scattered light 209 optical detector 212 does not actually respond to mass concentration C, the desired data product. Rather, the light scattering signals V sca 213 output by the detector 212 have to be manipulated.
  • the response of the scattered light 109 optical detector 212 follows d 2 . Accordingly, the detector 212 response "underweighs" particles relative to the ideal particle volume response d 3 , and large particle compensation is employed to make the response better approximate the ideal .
  • One such compensation 147 is to use the incremental scattering signal V sca 213 raised to the 3/2 power, that is, A 3 ' 2 .
  • A is the maximum incremental voltage response, above a background B, for relatively large single particles passing through scattering volume V s 50.
  • the background is the collective response to a plurality of relatively small particles in the scattering volume V s 50. If the particle concentration is low, such that single particles move though the sampling volume V s 50, then distinguishable impulsive signals V SGa 213 are produced over and above the background. From such pulse height distributions the mass of each such single particle can be calculated using the A 3 ' 2 procedure, or other functional forms.
  • the particle concentration is high, such that more than one relatively small particle is within the sampling volume V s 50 at one time, then single relatively large particles can still be detected above the small particle background.
  • the particle size distribution or what is equivalent, the mass fractions, for only the relatively large particles, may be calculated.
  • PSD particle size distribution
  • the collection optical system 219 defines the optical collection volume 216 which is similar to the beam focal volume 206. That is, if a uniformly illuminated test particle 208 is moved around in the "field of view" of collection optical system 219, the scattered light 209 falling on the optical detector 212 (FIGS. 1 and 2) is largest at an axial distance corresponding to the waist of the optical collection volume 216 and decreases both transversely and axially.
  • the converging-diverging lines represent contours of constant beam profile, such as the transverse l/e points of intensity in beam 220 or l/e points of response 222 of the collection optical system 219.
  • the optical collection volume 216 shares a common central point with the beam focal volume 206.
  • beam focal volume 206 is smaller than the optical collection volume 216, but this is not a requirement. Indeed, in some cases, particularly those with very high concentrations of small particles, a very thin "ribbon beam" is desirable.
  • the sampling volume V s 50 can be so large, in the limit of very low concentrations, as with conventional single particle counters, that its projection 34 (in effect a cross section) onto the transporting gas flow stream Q s 15 is larger than the transporting conduits 10 and 12.
  • an extinction mode sensor is formed when another optical detector 230 is placed in front of beam dump 218.
  • the extinction mode detector 230 is responsive to the extinction of light by the multiplicity of all aerosols in the beam, producing an extinction mode signal V e ⁇ t 232.
  • the extinction mode detector 230 can operate independently of and in parallel with scatter mode sensors 212 outputting light scattering signals V sca 213.
  • the extinction mode sensor volume V e 51 jointly defined by the beam and the presence of particles, is shown in FIGS. 1 and 2 with vertical hatch lines.
  • FIG. 4 is a plot 146 depicting extinction mode detector 230 response V e ⁇ t 230 to particles of various sizes, ranging from a volume mean size of 0.1 microns to 100 microns, within a sampling volume V s .
  • mass concentration is accurately measured independently of particle size, which would correspond to a horizontal line 148 through unity on the ordinate .
  • the extinction response V e ⁇ t 232 is within 50% of ideal. Near particle size of 1 micron, response is nearly ideal. Maximum response occurs when mean particle size is approximately equal to the wavelength of the illuminating light.
  • unity response corresponds to calibration with aerosols having volume mean diameter near maximum response .
  • a significant feature of embodiments of the invention is the combination of a relatively small sampling volume sensor (typically a scattering mode sensor) with a relatively larger sampling volume sensor (which conveniently may be either an extinction mode sensor or a large V s scattering mode sensor) .
  • a relatively small sampling volume sensor typically a scattering mode sensor
  • a relatively larger sampling volume sensor which conveniently may be either an extinction mode sensor or a large V s scattering mode sensor
  • the sampling volume V s can be made smaller.
  • the wavelength of the incident light beam can be made shorter, such as by employing a blue LED or a near ultraviolet laser. Such response is indicated by the plot 149.
  • V s 50 a problem with very small sampling volume V s 50 is that relatively little of the particle transport or flow is measured. Thus, a relatively smaller portion of the cross section of the bore of the conduit 10 transporting the powder is sampled. Accordingly, the results are statistically less representative, and factors such as non-uniform transport velocities across the cross section can become a problem.
  • a single particle 10 microns in diameter can produce the same detector voltage output as 100 particles one micron in diameter within the same sample volume V s . It follows that there is some minimum large particle diameter for which single particle pulses are usable.
  • scattered light detection from two separate sampling volumes is implemented, one relatively larger and one relatively smaller.
  • the relatively larger sampling volume by way of example and not limitation, 0.5 mm 3
  • the relatively smaller sampling volume by way of example and not limitation, 0.005 mm 3 , sized so that single events occur whereby large particle compensation 147 (FIG. 4) can be achieved.
  • FOG. 4 large particle compensation 147
  • concentrations of 10 g/m 3 , d 1 ⁇ m, unit density, volumes of approximately 10 -5 mm 3 are appropriate. Volume shape can be used advantageously in design. Volumes much smaller than this can be achieved with good optical components and mounts .
  • the relatively smaller sampling volume is within the relatively larger sampling volume and generally concentric therewith. This can be achieved by having two light beams orthogonal to each other. Light of the same or different wavelengths can be employed within the two sampling volumes.
  • illumination is preferably with a single ribbon beam.
  • FIG. 5 is a top view and FIG. 6 is an elevational view of an embodiment of the invention using two scatter mode sensors.
  • a conduit 150 transports aerosolized powder particles.
  • Optical elements 152 and 154 define a relatively larger sampling volume V s 156 within which a statistically significant quantity of particles are measured.
  • Optical elements 158 and 160 define a relatively smaller sampling volume V s 162 for which large particle compensation is implemented.
  • the optical elements are contained within sealed mounting tubes 170, 172, 174 and 176. Although shown separated in FIG. 6, and with different illumination wavelengths ⁇ and ⁇ 2 , the two optical sub-systems and thus the two sampling volumes 156 and 162 can be co-planar. They can even be coaxial, as illustrated in FIGS. 1 and 2.
  • FIGS. 5 and 6 disclose combination of large and small scattering volumes 156 and 162 for the improved measurement of mass concentrations and size distributions for mass delivery applications
  • FIGS. 7 and 8 show top and front views of a combined extinction and scattering apparatus 201. It may be appreciated that the large scattering volume 156 of FIGS. 5 and 6 is replaced with the typically larger and more uniformly responsive volume 157 associated with the extinction mode sensor design of FIGS. 7 and 8.
  • Mass concentration C may be reported in ⁇ g/liter and mass fraction (MF) in % mass associated with particles larger than size given by an effective or optical equivalent diameter in ⁇ m.
  • Aerosols 8 whose delivery rates through transport cross section 34, in ⁇ g/second, are controlled based on the C and MF readings of apparatus 201, are transported by sample gas flow Q s 15, and are confined to inlet conduit 10 and outlet conduit 12 by the conduits 10 and 12 and by sheath/purge gas flow Q P v.
  • Representative design parameters for the major elements in FIGS . 7 and 8 are :
  • Aerosol mass delivery control apparatus as disclosed in WO 00/58016 introduces aerosols 8 into transport flow Q s . Downstream deposition and other apparatus collects, measures and disposes of uncollected aerosols and are therein described.
  • the electro-optical apparatus and methods described herein represent further improvements .
  • multiple light detectors and amplifiers 20, 21 or equivalent charge coupled devices, following cylindrical lens 30 and neutral density filter 32, enable monitoring the uniformity of the aerosol mass concentration C across the cross section 34 via the multiple extinction mode signal responses V e ⁇ t 23.
  • Multiple, time and space-resolving signals V ext 23 from detectors/amplifiers 20,21 are received by high speed multiplexing switch 22, then analog to digital converter 24, then by microcontroller 26, and finally by system PC 28 or other general process control output device.
  • the primary data product is average or mean extinction mode signal V em .
  • V em is accurately and precisely proportional to mean aerosol mass concentration C m across cross section 34.
  • This V em data product is realized by the weighted combination, usually but not necessarily linear, of all extinction mode signals 23 and their subsequent processing.
  • V em is proportional to mean mass concentration C m only if the particle size distribution PSD is constant, i.e., the mass fractions (MFs) are constant. It is similarly known that V em depends on aerosol composition and shape. We have found that variances in particle size distribution PSD or Mass Fractions MF are generally more serious than composition and shape, which can usually be more tightly controlled by the aerosol feed stock manufacturer.
  • aerosol concentration measurement system 201 of FIGS. 7, 8 and 9 when aerosol concentration measurement system 201 of FIGS. 7, 8 and 9 is used for controlling aerosol delivery rate, it is the "as-aerosolized" feed stock that must be measured in cross section 34.
  • PSDs or MFs can notoriously be modified by the aerosol generation, transport and, especially, the deposition steps, all of which are size selective. Accordingly, we now disclose how our methods and apparatus correct for variations in PSD or MF. For simplicity, the explanation is for those aerosols 8 having optical equivalent diameters OED > 1 ⁇ m, in which case we have found that the extinction mode signals V e follow a 1/d law, to first order, as seen in FIG. 4.
  • d m and d mc it is only necessary to estimate d m and d mc .
  • methods embodied in the above-described TX sensor and system, manufactured by ppm, Knoxville, Tennessee are entirely adequate for many applications.
  • a single extinction mode channel and a single TX, scatter mode channel are satisfactory and enable a robust, simple system 200, as disclosed in FIGS. 1 and 2.
  • Such extinction mode and scatter mode channels may use a common ribbon beam 3 , or the illuminations for them may be separate.
  • the extinction mode channel 20 and the single scatter mode channels 4, 6 may be at different points in system 201.
  • the scatter mode channels 4 and 6 are essentially at a 90° scattering angle with respect to the thin ribbon beam 3. They are not coplanar with the ribbon beam 3, as seen best in FIG. 9, but are typically about 10° above the ribbon 3 plane, in its thin direction. These choices of orientation of 90° and 10° are made for clarity of disclosure. Other orientations may be employed.
  • FIGS. 7, 9 and 10 solid lines are used to illustrate limiting rays for the larger sampling or "view" volume V s 56 associated with scattering channel 6.
  • Dashed lines illustrate limiting rays for the smaller volume V s 54 associated with scattering channel 4.
  • Aperture 44 preceding detector 45 in the smaller V s 54 channel is smaller than the aperture 47 preceding detector 46 in the larger V s 56 channel 6.
  • These apertures define larger and smaller scattering volumes within the ribbon beam 3. (It is assumed for simplicity that the thin dimension of the ribbon beam is much larger than the essentially vertical dimensions of the scattering volumes V s . This, too, can be relaxed with a more general design. Indeed, very thin "ribbon beams," wherein the beam waist 206 is smaller than the collection optics waist 216, as in FIGS.
  • FIG. 10 is an enlargement emphasizing the overlapping scattering volumes V s 50 seen first in the top view of FIG. 7, and seen also in FIGS. 9 and 10. (A general call-out, 50, with an arrow is used in these figures because of scale. FIG. 10 clarifies this use.)
  • Both scattering channels collect light from a region of space that we call the joint response ellipsoid. That is, for each scattering channel, near 90° scattering is realized for those aerosol particles which are jointly in incident beam 3, such that radiation can fall on them, and within the principal response region or collection volumes of each of the collection optics 4 and 6. Since the scattering volume "vertical" dimensions are smaller than the thin dimension of the ribbon beam, which is assumed for simplicity, it follows that the incident intensity falling on the aerosols within each of the scattering volumes is roughly constant .
  • FIG. 10 is a top planar view of the l/e boundaries for the two joint response ellipsoid volumes.
  • FIGS. 11, 12 and 13 show detector response waveforms for a test particle of diameter d moving vertically along trajectories through points a, b and c in the plane of FIG. 10. We can also refer to the trajectories as a, b and c.
  • This planar view implies the general three-dimensional character of these ellipsoid volumes, the smaller one 54 dashed and the larger one 56 solid.
  • a single particle of size d produces significant detector response in the small Vs channel 4 only while it is within its ellipsoid volume 5 . If it produces a response V4 it follows that it must produce a response V6 from the larger scattering volume 56. But when this particle moves on a trajectory b which is near a boundary of the small channel ellipsoid volume 54, the detector response for the large channel is only slightly reduced. Thus only particles which are within the small ellipsoid volume 54 are accepted for sizing by the larger ellipsoid volume 56.
  • the single detector response from single particles is non-peaking: one cannot say whether a given response is due to a small particle in the center or the ellipsoid or a large one at a boundary.
  • the response to monodisperse aerosols, particles of a given size is a range of values, not a single, unique value.
  • Typical dimensions for the ribbon beam 3 are 0.1 mm thickness by 10 mm width; for the smaller ellipsoid volume 54, 0.1 mm length by 0.05 mm diameter; and for the larger ellipsoid volume 56, 0.2 mm length by 0.1 mm diameter.
  • the ellipsoid lengths and diameters are uniquely related to the aperture sizes 44,46 and magnifications of the lenses 53,55.
  • FIGS. 11, 12 and 13 show the detector response waveforms as a function of time for particles moving through the overlapping or generally concentric volumes 54, 56 on three different vertical trajectories.
  • FIG. 11 shows the detector responses to particles on trajectory a 57, near the center of the small ellipsoid volume 54.
  • FIG. 12 shows the detector responses to particles on trajectory b 58, at a l/e boundary point of the small ellipsoid volume 54.
  • FIG. 13 shows the detector responses to particles on trajectory c 59, outside the large ellipsoid volume 56.
  • Acceptable ratios V4/V6 l/e are but one choice.
  • Signals V4 and V6 have small particle coincidence, that is, there are a plurality of relatively smaller particles within each of the large and small sampling volumes. Such plurality or multiple particle responses occur which occurs when the aerosol concentration is high. Background levels 63 are higher for the large scattering channel 6 than the background levels 65 for the smaller volume channel 4. Note that the sensitivity in both channels 4,6 is set to produce the same signal for trajectory a 57 for the sake of simplicity in explanation but without loss of generality. Note further that the same particle of diameter d produces incremental voltage pulse A, with the peak amplitude occurring at the same instant in time in both the large 56 and small 54 volumes, for trajectory a 57. Background suppression methods are well known to deal with such coincidence, as are procedures for setting the small and large scattering volumes, 54,56, in view of the design center concentrations C and aerosol volume mean diameter d.
  • the scatter mode responses V4 or V6 are actually quite complex in character, including regions of nonmonotonic responses, sometime referred to as the "Mie Oscillations.” Of more practical importance, there are sometimes ranges of particle sizes d for which the underweighing does not follow l/d. Especially near the region of the maximum response of either V sca or V e ⁇ t per unit mass, shown as unity in FIG. 4, and which maximum response occurs for those particles whose OED is about equal to the wavelength of illumination, the large particle compensation does not follow a simple V6 3 ' 2 form.
  • the V4 and V6 signals in embodiments of our invention represent the passage of a particle of size d having various trajectories through the overlapping scattering volumes .
  • PSD is related to the large channel 6 peak voltage response V6, for those particles for which V4/V6 exceeds a preset ratio and occurs at the same time.
  • This peak voltage is determined by known peak sample and hold or by employing digital signal processing (DSP) .
  • DSP digital signal processing
  • DSP digital signal processing

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Abstract

L'invention concerne des procédés et des systèmes mettant en oeuvre des volumes multiples de détection (50) destinés à la mesure électro-optique de la concentration de la masse et à la distribution commandée d'aérosols. Ces derniers sont transportés dans un courant gazeux (15). Un capteur réagissant à des particules comprises dans un volume d'échantillonnage relativement plus important (156) dans le courant gazeux est combiné avec un autre capteur réagissant à des particules comprises dans un volume d'échantillonnage relativement plus petit (162) dans le courant gazeux.
PCT/US2001/005948 2000-02-22 2001-02-22 Mesure de la concentration de la masse d'un aerosol et du taux de distribution de la masse WO2001063255A2 (fr)

Priority Applications (4)

Application Number Priority Date Filing Date Title
AU2001245329A AU2001245329A1 (en) 2000-02-22 2001-02-22 Measurement of aerosol mass concentration and mass delivery rate
AU2001278131A AU2001278131A1 (en) 2000-08-01 2001-08-01 Generation, delivery, measurement and control of aerosol boli for diagnostics and treatments of the respiratory/pulmonary tract of a patient
PCT/US2001/024183 WO2002009574A2 (fr) 2000-08-01 2001-08-01 Generation, administration, mesure et reglage de doses d'aerosol pour diagnostiquer et traiter les voies respiratoires/pulmonaires d'un patient
US10/499,473 US20050066968A1 (en) 2000-08-01 2001-08-01 Generation, delivery, measurement and control of aerosol boli for diagnostics and treatments of the respiratory/pulmonary tract of a patient

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WO2007066113A1 (fr) * 2005-12-07 2007-06-14 Loughborough University Enterprises Limited Verification de la delivrance de particules fines
CN108426806A (zh) * 2017-02-15 2018-08-21 帕拉贡股份公司 颗粒物测量设备及其操作方法
CN108426807A (zh) * 2017-02-15 2018-08-21 帕拉贡股份公司 颗粒物传感器
CN115524449A (zh) * 2022-09-15 2022-12-27 山东大学 一种机电产品服役过程清单数据动态收集方法及系统

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007066113A1 (fr) * 2005-12-07 2007-06-14 Loughborough University Enterprises Limited Verification de la delivrance de particules fines
CN108426806A (zh) * 2017-02-15 2018-08-21 帕拉贡股份公司 颗粒物测量设备及其操作方法
CN108426807A (zh) * 2017-02-15 2018-08-21 帕拉贡股份公司 颗粒物传感器
CN115524449A (zh) * 2022-09-15 2022-12-27 山东大学 一种机电产品服役过程清单数据动态收集方法及系统

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