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
  • G01N21/47—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
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N1/00—Sampling; Preparing specimens for investigation
  • G01N1/02—Devices for withdrawing samples
  • G01N1/22—Devices for withdrawing samples in the gaseous state
  • G01N1/2202—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling
  • G01N1/2208—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling with impactors
• • 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
  • G01N15/06—Investigating concentration of particle suspensions
• • 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
  • G01N15/06—Investigating concentration of particle suspensions
  • G01N15/075—Investigating concentration of particle suspensions by optical means
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N1/00—Sampling; Preparing specimens for investigation
  • G01N1/02—Devices for withdrawing samples
  • G01N1/22—Devices for withdrawing samples in the gaseous state
  • G01N1/2202—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling
  • G01N2001/222—Other features
  • G01N2001/2223—Other features aerosol sampling devices
• • 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
• • 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
  • G01N15/0255—Investigating particle size or size distribution with mechanical, e.g. inertial, classification, and investigation of sorted collections
  • G01N2015/0261—Investigating particle size or size distribution with mechanical, e.g. inertial, classification, and investigation of sorted collections using impactors
• • 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
  • G01N2021/4704—Angular selective
  • G01N2021/4711—Multiangle measurement
• • 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
  • G01N2201/06—Illumination; Optics
  • G01N2201/064—Stray light conditioning
  • G01N2201/0642—Light traps; baffles

Definitions

• the technical field of the invention is that of air pollution sensors.
• the present invention relates to a sensor for measuring the concentration of particles in the air, both in an indoor environment, confined, and in an outdoor environment, outdoor.
• Air quality is an essential parameter for ensuring a good quality of life, especially in cities and urban areas.
• particles of a few ⁇ in diameter are particularly dangerous for human health. These particles are produced largely by human activities related to industry and transportation. They are responsible for health risks such as impaired lung function and can lead to decreased life expectancy.
• PM Particulate Matter particles are particles having an aerodynamic diameter of less than 10 ⁇ ; they are not retained by the upper airways (nose, mouth) and are therefore "breathable". Fine PM particles are often classified according to their size.
• the PM10 name is used for particles having an aerodynamic diameter of less than 10 ⁇ ; PM2.5 for particles with aerodynamic diameter less than 2.5 ⁇ and PM1 for particles with aerodynamic diameter less than 1 ⁇ .
• the Aerodynamic diameter of a particle is an equivalent quantity used to describe the aeraulic behavior of particles in a gas stream such as an airflow.
• the aerodynamic diameter of a particle is defined as the diameter of a sphere of unit density (1 g / cm 3 ) and having the same limit speed of fall as said particle in a fluid at rest.
• the terms "aerodynamic diameter of a particle” and “diameter of a particle” are used interchangeably.
• optical techniques rely on the disturbance of a light beam by the passage of particles through the light beam.
• the simplest gravimetric devices work by impinging the particles on a filter which is then weighed. These devices have a good selectivity in size and are relatively inexpensive but they do not allow real-time monitoring of the particle concentration.
• the beta gauge systems rely on an electron absorption technique. These systems have the advantage of being very reliable but, in addition to their high cost, they require a radioactive source which can reduce their portability.
• TEOM® gravimetric systems (Tapered Element Oscillating Microbalance) use a microbalance and are used for regulatory monitoring in some countries. These systems allow real time monitoring of the particle concentration but they do not allow good selectivity and remain relatively expensive.
• the invention offers a solution to the problems mentioned above, by making it possible to measure in real time the concentration of particles in the air, with a device that is both compact, portable and selective in size for the particles, while being sufficiently precise, that is to say, achieving a measurement uncertainty of at least less than 50% for PM1, PM2.5 and PM10 fine particulate mass concentrations.
• One aspect of the invention relates to a sensor for real-time measurement of the concentration of particles in air comprising:
• an internal channel for the circulation of an air flow comprising particles to be detected having a first portion and a second portion communicating with the first portion, the first portion having a first open end forming an input of the flow; of air and the second portion having a second open end forming an outlet of the air flow, the second portion having:
• the second portion having a folded shape with a first rectilinear branch connected to a second rectilinear branch by a link substantially perpendicular to the first and second rectilinear branches, so that the upstream zone comprises the first rectilinear branch, the downstream zone comprises the second rectilinear branch and the detection zone is in the connection between the first and second rectilinear branches;
• a light source configured to emit light radiation in a propagation direction, the light radiation being focused in the detection zone of the internal channel
• a first photodetector configured to capture a first diffusion signal emitted by particles passing through the detection zone in a first direction forming a first non-zero angle with the direction of propagation of the light radiation, the first direction and the direction of propagation defining a foreground ;
• a second photodetector configured to capture a second diffusion signal emitted by particles passing through the detection zone in a second direction forming a second non-zero angle with the direction of propagation of the light radiation, the second direction belonging to a second plane distinct from the foreground, the second angle being different from the first angle and the first and second angles not being additional;
• a light trap configured to receive the light radiation at the output of the detection zone so as to prevent a parasitic return of the light radiation towards the detection zone.
• the sensor according to one aspect of the invention may have one or several additional characteristics among the following, considered individually or in any technically possible combination:
• the difference between the first and second angles is at least 5 ° and preferably at least 15 °.
• the second plane is preferably perpendicular to the foreground.
• the light trap has a black wall and a black cavity, the wall deviating light radiation to the cavity.
• the wall is preferably smooth while the cavity is rough.
• the internal channel comprises:
• first portion having a lateral wall extending between a first open end and a closed second end, the first open end extending along an input plane; a second portion communicating with the first portion via a first opening in the side wall of the first portion, the first opening being adjacent to the first open end;
• a storage area communicating with the first portion via a second opening in the side wall of the first portion, the second opening being adjacent to the closed second end, the first and second openings being arranged on either side of the wall; lateral;
• a deflection plate attached to a junction between the first open end of the first portion and the second portion, the deflection plate extending inside the first portion and forming with a first direction normal to the entry plane an angle a such that:
• the deflection plate the first portion and the first and second openings being dimensioned so that in a flow of air entering the sensor through the first open end and having first particles of diameter less than or equal to 10 ⁇ and second particles of diameter greater than 10 ⁇ , the first particles are deflected by the deflection plate, pass through the first opening and reach the second portion of the internal channel while the second particles are deflected by the deflection plate, impacted by a portion of the side wall forming an impaction plate, pass through the second opening and reach the storage area.
• the internal channel of the sensor provides at the input a filter function: only the first particles enter the second portion of the internal channel to be subsequently detected, while the second particles are diverted into a storage area.
• the first and second particles are indeed masses and therefore different inertias, which is why they do not follow the same fluidic path. This prevents fouling of the second portion of the internal channel by the second particles, which would lead to a drift of the sensor response and measurement artifacts. No measurement being made in the storage area, its fouling by the second particles is not problematic.
• the second portion of the internal channel has a first open end communicating with the first portion of the internal channel and a second open end
• the sensor comprises a device for circulating an air flow in the internal channel, said device being arranged at the second end of the second portion of the inner channel and being configured to circulate a flow of air from the first end of the first portion of the inner channel to the second end of the second portion of the inner channel.
• the device for circulating an air flow in the internal channel is a fan or a pump.
• the ratio S2 / S1 of the second surface on the first surface is such that:
• the second portion of the inner channel having a first open end communicating with the first portion of the inner channel and a second open end, and the second portion of the inner channel having a detection zone, an upstream zone between the first end and the detection zone. and a downstream zone between the detection zone and the second end, the sensor is preferentially such that:
• the second portion of the internal channel has a folded shape, and the upstream zone of the internal channel has an inclined portion widening between the first end of the internal channel and the detection zone,
• the storage zone (120) has a volume of between 0.5 mL and 5 mL
• the first portion of the internal channel is of circular section and the sensor comprises a hollow cylinder shaped fitting piece of circular section, the adapter piece protruding from the sensor at the first open end of the first portion.
• the upstream zone further comprises at least one portion having an S shape with first and second bends.
• the inner channel extending at each point in a direction De and "section of a portion of the internal channel" means a section normal to the direction De:
• the upstream zone of the second portion comprises a laminarization element, which comprises at at least one plate projecting radially from a side wall of the second portion, said at least one plate having a height H measured radially and whose ratio of the total height Ht measured radially between the side wall and the center of the section is such that: 10% ⁇ H / Ht ⁇ 100%.
• the sensor further comprises a device for heating an air flow circulating in the internal channel, the heating device comprising at least one heating element by Joule effect arranged on a wall of the internal channel upstream of the zone. detection.
• the heating device preferably comprises a plurality of heating elements by Joule effect in series.
• the heating device preferably comprises means for controlling the at least one heating element by Joule effect as a function of a first temperature measurement and a second humidity measurement.
• the at least one heating element by Joule effect is preferably a resistance or alternatively a linear regulator.
• FIG. 1 shows schematically a perspective view of a sensor for real time measurement of the concentration of particles in the air according to one aspect of the invention.
• FIG. 2a schematically shows a view of an internal channel of the sensor of FIG. 1 along a section plane of axes y, z.
• FIG. 2b schematically shows a partial view of the internal channel of the sensor of FIG. 1 along the section plane of axes y, z.
• FIG. 2c schematically shows a partial view of a sensor according to one aspect of the invention comprising an adaptation piece.
• FIG. 3a schematically shows a view of the internal channel of the sensor of FIG. 1 along a section plane of axes x, y, according to a first embodiment.
• FIG. 3b schematically shows a partial view of the internal channel of the sensor of FIG. 1 along a section plane of axes x, z.
• FIG. 3c schematically shows a view of an internal channel of a sensor according to an x-axis section plane, according to a second embodiment.
• FIG. 3d1 schematically shows a first example of a laminarization element within an internal channel of a sensor according to any one of the embodiments of the invention.
• FIG. 3d2 shows schematically a second example of a laminarization element within an internal channel of a sensor according to any one of the embodiments of the invention.
• FIG. 3d3 schematically shows a third example of a laminarization element within an internal channel of a sensor according to any one of the embodiments of the invention.
• FIG. 4a schematically shows a view of an optical detection system of the sensor of FIG. 1 along a section plane of axes x, y.
• FIG. 4b schematically shows a partial perspective view of the optical detection system of the sensor of FIG. 1.
• FIG. 5 schematically shows a view of a heating device of the sensor of FIG. 1 along a section plane of axes x, y.
• the figures are defined in an orthogonal coordinate system of axes x, y, z.
• FIG. 1 schematically shows a perspective view of a sensor 1 for the real-time measurement of the concentration of particles in the air according to one embodiment of the invention.
• FIG. 1 shows a section plane A of axes y, z, a section plane B of axes x, y and a section plane C of axes x, z.
• the sensor 1 comprises an internal channel 10 (referenced in FIG. 2a) having a first portion 100 and a second portion 1 10 (referenced in FIG. 2b), the first portion having a first open end 101 forming an input of a flow of air in the internal channel of the sensor 1, and the second portion having a second open end 1 12 forming an outlet of the air flow of the internal channel of the sensor 1.
• the air inlet 101 and the air outlet 1 12 preferably extend in two distinct planes, and even more preferably in two planes that are not parallel to each other, so that the inlet air flow is not not disturbed by the flow of air output.
• the air inlet 101 extends in a plane parallel to plane plane B, while the air outlet 1 12 extends in a plane substantially parallel to the plane Cutting C.
• FIG. 2a schematically shows a view along the section plane A of the internal channel 10 of the sensor 1.
• FIG. 2b schematically shows a partial view along the sectional plane A of the internal channel 10 of the sensor 1.
• Figures 2a and 2b particularly illustrate a fluid filter function of the sensor 1 and are described together.
• the sensor 1 comprises an internal channel 10 having:
• the first portion 100 having a side wall 103 extending between the first open end 101 and a second closed end 102, the first open end 101 extending along an input plane Pe;
• the second portion 1 10 communicating with the first portion 100 via a first opening 105 in the side wall 103 of the first portion 100, the first opening 105 being adjacent to the first open end 101;
• a storage area 120 communicating with the first portion 100 via a second opening 107 in the side wall 103 of the first portion 100, the second opening being adjacent to the second closed end 102, the first and second openings 105, 107 being arranged on both sides of the side wall 103;
• a deflection plate 130 fixed to a junction between the first open end 101 of the first portion 100 and the second portion 1 10, the deflection plate 130 extending inside the first portion 100 and forming with a first direction D1 normal to the entry plane Pe an angle a such that:
• the deflection plate 130, the first portion 100 and the first and second openings 105, 107 being dimensioned so that in a flow of air entering the sensor 1 through the first open end 101 and having first particles of smaller diameter or equal to 10 ⁇ and second particles of diameter greater than 10 ⁇ , the first particles pass through the first opening 105 and reach the second portion 1 10 of the internal channel while the second particles pass through the second opening 107 and arrive in the storage area 120.
• the first and second openings 105, 107, arranged on either side of the side wall 103, are not facing each other, that is to say that any plane of axes x, y and passing through the first opening 105 does not pass through the second opening 107, and vice versa.
• the first and second openings 105, 107 are arranged on either side. of the side wall 103 "the fact that:
• the first opening 105 is in a first half-space, to which belong the deflection plate 130 and the second portion 1 10 of the internal channel, and
• the second opening 107 is in a second half-space, to which the storage area 120 belongs.
• Part of the side wall 103 is an impaction plate 103-i: this is the part of the side wall 103 which is arranged on the side of the first opening 105, in the first half-space.
• the impaction plate 103-i is arranged on the side of the first opening 105.
• the first portion 100 is rectilinear along the first direction D1.
• the first portion 100 may alternatively be curved.
• the first portion 100 and the second portion 1 10 are of rectangular section.
• the first portion 100 and / or the second portion 1 10 may alternatively be of square, polygonal, circular, elliptical section ...
• the first portion 100 and the second portion 1 10 may both have the same section geometry, for example both of circular section, or each have a geometry of distinct section, for example circular section for the first portion 100, and rectangular or square section for the second portion 1 10.
• section of a portion a section normal to a direction De (represented for example in FIGS. 3a and 3c) according to which extends the portion of the internal channel at each point and according to which a flow of air is brought to circulate.
• each section of the first portion 100 is in a plane parallel to the plane B of axes x, y.
• the determining parameter is the surface area of the section of each of the first and second portions 100, 1, 10. understands that several different geometries can be associated with the same surface.
• the first portion 100 is of circular section and the sensor 1 comprises an integrated adapter piece Pa, protruding from the sensor 1 at the first open end 101 of the first portion 100, so as to provide an extension of the first portion 100.
• the adaptation piece Pa has a hollow cylinder shape, with a circular cross-section of the same diameter or different diameter with respect to the circular section of the first portion 100.
• the adaptation piece Pa is in one piece with the sensor 1; the adaptation piece Pa may in particular be molded with the sensor 1.
• the adaptation piece Pa makes it possible to receive a tube.
• the first surface S1 is the inlet surface of the internal channel 10, that is to say the flow area along the entry plane Pe of the first open end 101 of the first portion 100 of the internal channel 10 ;
• the second surface S2 is the smallest flow area of the first portion 100 defined between the end of the deflection plate 130 and the side wall 103;
• the third surface S3 is the smallest flow area defined between the end of the deflection plate 130 and the end of the impingement plate 103-i delimiting the first opening 105.
• the ratio S2 / S1 of the second surface S2 on the first surface S1 is advantageously such that: 52
• the first surface S1 has an area of 50 mm 2 and the second surface S2 has an area of 30 mm 2 , a ratio S2 / S1 of 60%.
• the cutoff diameter d that is to say the aerodynamic diameter such that 50% of the particles of this diameter reach the second portion 1 10 of the internal channel and 50% do not reach it, can be estimated by the formula next :
• the reference density is 1 g / cm 3 .
• the angle ⁇ , illustrated in particular in FIG. 2b, is preferentially such that:
• the angle a is more preferably such that:
• the angle a is even more preferentially such that: 25 ° ⁇ a ⁇ 35 °
• a deflection plate 1 30 of length I 4 mm and a speed u of the air flow passing through the third surface S3 of 5 m / s:
• the storage zone 1 advantageously has a volume of between 0.5 ml and 5 ml. This ensures a maintenance-free life of the sensor 1 sufficient, that is to say greater than 1 0000 hours in environments highly polluted with fine particles. An environment is considered to be highly polluted with fine particles when it contains on average at least 250 ⁇ g / m 3 of fine particles.
• the cumulative volume of the first portion 100 of the internal channel and the storage zone 1 is advantageously less than 10 ml. This limits the size of the sensor 1, and therefore its size and mass.
• FIG. 3a schematically shows a view along the section plane B of the sensor 1 according to a first embodiment.
• Figure 3a shows a section plane D of axes x, z.
• FIG. 3b schematically shows a partial view along the section plane D of the sensor 1.
• FIG. 3b schematically shows a view along the section plane B of the sensor 1 according to a second embodiment.
• Figures 3a, 3b and 3c are described together.
• the second portion 1 1 0 of the internal channel has an open first end 1 1 1 which communicates with the first portion 1 00 of the internal channel, and the second end 1 12 open.
• the second portion 1 10 of the internal channel comprises a detection zone 1 15, an upstream zone 1 14 between the first end 1 1 1 and the detection zone 1 15, and a downstream zone 1 1 6 between the detection zone 1 and the second end 1 12.
• the second portion 1 10 of the internal channel advantageously has a folded shape, with a first rectilinear branch Br1 connected to a second straight branch Br2 by a connection substantially perpendicular to the first and second straight branches Br1, Br 2.
• the first and second straight branches Br1, Br2 may be parallel to each other but are not necessarily parallel to each other.
• the upstream zone 1 14 comprises the first rectilinear branch Br1
• the downstream zone 1 16 comprises the second rectilinear branch Br2
• the detection zone 115 is in the connection between the first and second straight branches Br1, Br2.
• the shape folded illustrated in Figure 3a can also be described as comprising the first rectilinear branch Br1, the second rectilinear branch Br2 and a third straight branch Br3 substantially perpendicular to the first and second straight branches Br1, Br2, the third straight branch Br3 being connected to the first straight branch Br1 by a first bent portion Pc1 and the second straight branch Br2 by a second bent portion Pc2.
• the link defined previously between the first and second straight branches Br1, Br2 comprises the third straight branch Br3 and the first and second elbowed portions Pc1, Pc2.
• the upstream zone 1 14 comprises the first rectilinear branch Br1 and the first bent portion Pc1
• the downstream zone 1 1 6 comprises the second bent portion Pc2 and the second straight branch Br2
• the detection zone 1 15 is in the third portion rectilinear Br3.
• the upstream zone 1 14 may further comprise at least one portion having an S shape with a first bend C1 and a second bend C2, as illustrated in Figure 3c.
• the first rectilinear branch Br1 can be in upstream or downstream of the first and second elbows C1, C2.
• the geometry and the dimensioning of the upstream zone 1 14 are advantageously chosen so that a flow of air disturbed by the first portion 100 of the internal channel and entering the second portion 1 10 of the internal channel is laminar and with a homogeneous speed when it reaches the level of the detection zone 1 15. It is considered that the air flow presents a homogeneous speed in the detection zone 1 15 when at each point of a section of the zone detection, the speed v along the y axis perpendicular to said section is such that:
• the upstream zone 1 14 of the internal channel has an inclined portion widening by connecting a first horizontal plane H1, which substantially extends the first end 1 1 1 of the internal channel, to a second horizontal plane H2, according to which substantially extends the internal channel between its detection zone 1 15 and its second end 1 12.
• the inclination ⁇ of this portion measured relative to the vertical, is such that:
• the widening of the inclined portion of the upstream zone 1 14 of the internal channel is between 150 and 300 ⁇ 2 per mm length along the x axis.
• the inclined portion which has just been described is illustrated in particular in connection with the first embodiment of FIG. 3a, but it is also compatible with the second embodiment of FIG. 3c.
• the upstream zone 1 14 of the internal channel may also have a laminarization element projecting from at least one side wall of the second portion 1 10 and extending in the direction D 1 by which the internal channel 10 extends in each point and according to which a flow of air is circulated.
• the laminarization element is rectilinear if it is in a straight portion of the second portion 1 10, curved if it is in a bent portion of the second portion.
• the laminarization element can be in one piece or have several distinct parts: thus in the example of FIG. 3c, the laminarization element comprises a first straight element EL1 in the first rectilinear branch Br1 and a second sub-element EL2 curved in the first bent portion Pc1.
• the length of the laminarization element, or the cumulative length of the sub-elements of the laminarization element measured in the direction De, may vary between 0.1% and 100%, preferably between 10% and 60% of the length. of the upstream zone 1 14 measured in the direction De.
• the length of the first sub-element EL1 is referenced "Law”
• the length of the second sub-element EL2 is referenced "Lo2”.
• the term "laminarization element” means the laminarization element or each of its sub-elements.
• the laminarization element is illustrated in particular in connection with the second embodiment of FIG. 3c, but it is also compatible with the first embodiment of FIG. 3a.
• Figures 3d1, 3d2 and 3d3 respectively show first, second and third examples of laminarization elements, represented with hatching.
• Each of the figures 3d1, 3d2 and 3d3 is a sectional view of the upstream zone 1 14, in a plane normal to the direction De.
• Different possible section geometries of the second portion 1 10 are shown in dotted lines.
• the laminarizing element comprises at least one plate projecting from the side wall shown in dotted lines and oriented radially with respect to the direction De (which corresponds to the direction normal to the plane of the sheet and passing through the center of each section geometry), said at least one plate having a height H (referenced in FIG.
• Each plate of the laminarization element has a thickness Ep (referenced in FIG. 3d1), measured at each point perpendicular to the direction De and in the radial direction, such that: 0.1 mm ⁇ Ep ⁇ 2 mm and more preferably such that: 0.5 mm ⁇ Ep ⁇ 1 mm. According to the example of FIG.
• the laminarizing element thus has a cruciform profile.
• the first, second, third and fourth plates el01, el02, el03, el04 are all of equal height H such that H ⁇ Ht, so that they do not meet at the center of the section.
• the laminarizing element may comprise only one, two or three of four plates - in any possible combination: first plate; first and second plates; first and third plates: first and fourth plates; first, second and third plates; etc. Otherwise :
• the laminarization element when the laminarization element comprises several plates, they may be of the same height or of different heights. All plates can join (as in the example of Fig. 3d1), or only a part, or none (as in the example of Fig. 3d2).
• the laminarization element when the laminarization element comprises several sub-elements, they may be of different geometry and / or dimensions.
• the sensor 1 preferably comprises a device 20 for circulating an air flow in the internal channel 10, referenced in FIG.
• the device 20 may advantageously be slaved to ensure a constant average air flow rate at the detection zone 1 15.
• the flow of air through the internal channel 10 of the sensor 1 has a flow rate of 0.0032 m 3 / min and the pressure loss generated by the internal channel 10 is calculated at 9.6 Pa: in this embodiment, the device 20 is advantageously controlled to ensure an average speed of 1 m / s at the detection zone 1 15.
• the device 20 may in particular be a fan, a pump or micro-pump.
• FIG. 4a schematically shows a view of an optical detection system of the sensor 1 along the section plane B of axes x, y.
• FIG. 4b schematically shows a partial perspective view of the optical detection system of the sensor 1.
• Figures 4a and 4b particularly illustrate an optical detector function of the sensor 1 and are described together.
• the optical detector function is compatible with all the modes and characteristics previously described in connection with the fluid circulation, and in particular with the embodiments described with reference to FIGS. 3a, 3b, 3c, 3d1, 3d2, 3d3.
• the optical sensor detection system 1 comprises:
• a light source 30 configured to emit light radiation in a propagation direction Dp, the light radiation being focused in the detection zone 1 of the internal channel 10;
• a first photodetector 40 configured to pick up a first diffusion signal emitted in a first direction D1 by particles passing through the detection zone, the first direction D1 forming a first angle ⁇ 1 non-zero with the propagation direction Dp of the light radiation;
• a second photodetector 50 configured to pick up a second diffusion signal emitted in a second direction D2 by particles passing through the detection zone, the second direction D2 forming a second angle ⁇ 2 which is not zero with the propagation direction Dp of the light radiation, the second angle ⁇ 2 being different from the first angle ⁇ 1 and the first and second angles ⁇ 1, ⁇ 2 not being additional;
• a light trap 60 configured to receive the light radiation at the output of the detection zone 1 15 so as to prevent a parasitic return of the light radiation towards the detection zone 1 15.
• the light source 30 is preferably a laser source, and in particular a laser diode laser source.
• the light source 30 may be a light emitting diode, or LED.
• the focusing of the light radiation in the detection zone is obtained by focusing optics.
• the light radiation emitted by the light source 30 preferably has a power of between 1 mW and 20 mW, more preferably a power of between 1 mW and 10 mW, more preferably a power of between 1 mW and 5 mW.
• the light radiation emitted by the light source 30 has, for example, a light radiation of 2 mW.
• the light source 30 may emit visible light radiation, i.e.
• the first and second photodetectors 40, 50 are preferably photodiodes.
• the first and second photodetectors 40, 50 could be photomultipliers. Compared to photomultipliers, photodiodes have the advantage of being less expensive and simpler to implement in miniature systems.
• Each of the first and second photodetectors 40, 50 has an active surface and an axis detection cone normal to its active surface.
• the light trap 60 comprises a wall 61 and a cavity 62, the wall 61 being oriented, with respect to the propagation direction Dp, so as to deflect the light radiation towards the cavity 62.
• the wall 61 and the cavity 62 are advantageously black to maximize absorption of incident light radiation.
• the wall 61 is smooth while the cavity 62 is rough.
• Smooth surface means a surface having a mean roughness deviation Ra such that:
• Ra surface means a surface having a mean roughness difference Ra such that:
• the average roughness deviation Ra is the standard deviation of the asperities of the surface considered, as defined in ISO 4287.
• the difference ⁇ between the first and second is preferably chosen. angles ⁇ 1, ⁇ 2 so that
• k is a constant expressed in rad / W / m
• d is the distance between each of the first and second photodetectors 40, 50 on the one hand, and the detection zone 1 1 5 on the other hand, expressed in m; if the first and second photodetectors 40, 50 are not equidistant from the detection zone 1 15, d is the smallest distance between each of the first and second photodetectors 40, 50 on the one hand and the detection zone 1 1 5;
• ⁇ is the wavelength of the light radiation, expressed in m
• S is the active area of the first and second photodetectors, expressed in m 2 ; if the first and second photodetectors do not have the same active area, S is the largest active area of the first and second photodetectors;
• P is the power of the light source, expressed in W.
• the greater the power of the light source the greater the difference ⁇ between the first and second angles ⁇ 1, ⁇ 2 may be weak.
• a difference ⁇ of at least 5 ° and preferably at least 15 ° between the first and second angles ⁇ 1, ⁇ 2 is chosen.
• the first angle ⁇ 1 between the propagation direction Dp and the first direction D1 is such that:
• first and second directions D1, D2 are preferably chosen so that:
• the first direction D1 and the direction of propagation Dp define a first plane P1
• the second direction D2 belongs to a second plane P2 distinct from the first plane P1.
• the second plane P2 is perpendicular to the first plane P1. Still in the particular example of FIG. 4c, the axis of the detection cone of the first photodetector 40 coincides with the first direction D1, and the axis of the detection cone of the second photodetector 50 coincides with the second direction D2.
• the first photodetector 40 could alternatively be arranged so that the axis of its detection cone is not coincident with the first direction D1, for example by using a mirror to deflect the first diffusion signal in a direction D1 'and by arranging the first photodetector 40 so that its detection cone coincides with the deflected direction D1 '.
• the second photodetector 50 could alternatively be arranged so that the axis of its detection cone is not coincident with the first direction D2, for example by using a mirror to deflect the second diffusion signal in a direction D2 ' and arranging the second photodetector 50 so that its detection cone coincides with the deflected direction D2 '.
• FIG. 5 schematically shows a sectional view, along plane B, of axes x, y, of a device for heating the flow of air flowing in the internal channel 10 of the sensor 1, the heating device comprising at least one Joule heating element arranged on a wall of the inner channel 10, upstream 1 14 of the detection zone 1 15.
• Figure 5 particularly illustrates a thermal control function of the hygrometry of the air flow flowing in the internal channel 10 of the sensor 1.
• the thermal control function is compatible with all modes and characteristics previously described in connection with optical detection and fluid circulation and in particular with the embodiments described with reference to FIGS. 3a, 3b, 3c, 3d1, 3d2, 3d3.
• the heating device advantageously allows a control of the hygrometry of the particles of the air flow in order to overcome the external atmospheric conditions. Indeed, certain types of particles swell significantly under the effect of moisture, which is likely, by changing the size of the particles, to distort the measurements. By controlling the hygrometry of the air flow, the accuracy of the sensor 1 is improved.
• the Joule heating element is preferably a resistor or alternatively a linear regulator.
• the heating device preferably comprises a plurality of Joule heating elements in series, said plurality being arranged on a wall of the internal channel upstream of the detection zone. This has the advantage of using a plurality of smaller heating elements, rather than a single heating element of larger dimensions, and thus minimizing the mechanical disturbance of the air flow within the internal channel 10.
• the heating device comprises first, second and third heating elements by Joule effect R1, R2, R3.
• the temperature of the air flow arriving in the detection zone is preferably 3 ° C higher than 10 ° C to the temperature of the air flow entering the sensor 1. This difference in temperature is sufficient to ensure an absence of growth factor of the particles present in the air flow ("growth factor" in English).
• the sensor 1 preferably comprises a temperature sensor and a humidity sensor and the at least one heating element by Joule effect is preferably controlled according to a first measurement of temperature and a second humidity measurement of the air flow in the sensor 1.
• the first temperature measurement and the second humidity measurement of the airflow can for example be performed at the input or at the output of the internal sensor channel 1, or at any intermediate point of the internal channel 10. It is thus adapted to outdoor weather conditions to improve sensor accuracy while optimizing energy consumption.
• the sensor 1 according to one aspect of the invention advantageously provides at the same time the functions of fluidic filter, optical detector and thermal control previously described, but the sensor 1 according to one aspect of the invention can alternatively ensure only one or two of these three functions, according to all possible combinations:
• the sensor 1 preferably comprises a computer and a storage memory in order to carry out all or part of the following functions:
• the computer is for example a microcontroller or a microprocessor.
• the storage memory is preferably a reprogrammable read-only memory EPROM (English “Erasable Programmable Read Only Memory”) but can also be a random access memory RAM (Random Access Memory), a programmable read-only memory PROM (from English "Programmable Read Only Memory”), a FLASH-EPROM memory or any other chip or memory cartridge.

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• 2017
  • 2017-05-17 FR FR1754367A patent/FR3066599A1/fr not_active Withdrawn
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