FR3129725A1 - Air intake device for an air quality measuring instrument - Google Patents

Abstract

The invention relates to an air intake device (3) for an air quality measuring instrument. The device (3) comprises a peripheral opening (50), a sampling cavity (55) and two slowing cavities (52, 53) in fluid communication with the peripheral opening (50) and the sampling cavity (55). The peripheral opening (50) and the slowing cavities (52, 53) extend concentrically around an axis (A1). Figure for abstract: Fig. 3

Description

Air intake device for an air quality measuring instrument

The invention relates to the field of instruments for measuring particles in a gaseous fluid such as atmospheric air.

State of the prior art

Atmospheric air contains solid particles in suspension, in particular fine particles called "PM10" whose diameter is less than 10 µm and "PM2.5" whose diameter is less than 2.5 µm. Such particles, which are partly of anthropogenic origin, have a considerable health impact. In particular, it has been estimated that the presence of PM2.5 particles in the ambient air contributes to the premature death of several tens of thousands of people each year in France.

In this context, the measurement of atmospheric air quality is decisive in the deployment of appropriate solutions to protect populations exposed to such particles.

To this end, it is known to carry out measurements of ambient air using sensors or particle counters to which an air sample is routed via an air sampling system.

The measuring instruments known in the state of the prior art cannot be embarked on a drone-type aircraft, in particular in an urban environment, because they are too massive and/or bulky and/or energy-consuming.

Furthermore, the known measuring instruments are generally ineffective in the presence of a sustained wind.

The invention aims to overcome all or part of the drawbacks of the measuring instruments known in the state of the prior art.

A particular object of the invention is to provide a device that can operate in a fixed station or on the move, including in the presence of a sustained relative wind.

To this end, the subject of the invention is a device for admitting a gaseous fluid with a view to carrying out a measurement of particles present in the fluid, characterized in that it comprises:
– a sampling cavity,
– an intermediate cavity,
– a peripheral opening configured to allow introduction of the fluid into the intermediate cavity, and
– two slowing cavities which are each in fluid communication with the intermediate cavity on the one hand and the sampling cavity on the other hand so as to convey part of the fluid present in the intermediate cavity towards the sampling cavity in order to constitute in the sampling cavity a sample of the fluid,
the intermediate cavity and the sampling cavity being spaced from each other along an axis, the slowing cavities and the peripheral opening extending concentrically around this axis.

The device of the invention thus makes it possible to constitute a sample of fluid in the sampling cavity, with a view to carrying out on this sample a measurement of particles present in the fluid.

This device does not require a high-flow suction system, which simplifies the instrument and reduces its mass, size and consumption.

In addition, this device has been found to work both in a fixed station and on the move, including in the presence of a sustained relative wind.

In one embodiment, the device comprises a receiving cavity in fluid communication with one of said slowing cavities extending radially inside the other of said slowing cavities with respect to said axis, the device comprising a wall separating the sampling cavity and the receiving cavity from each other, this wall comprising orifices establishing fluid communication between the receiving cavity and the sampling cavity.

In one embodiment, the device comprises one or more section restriction members of one and/or the other of the slowing cavities.

The section restriction member(s) may comprise one or more annular collars.

In one embodiment, the device comprises fluid guide members arranged in the at least one peripheral opening so as to guide the fluid towards the intermediate cavity.

Such guide members make it possible in particular to reduce or prevent a gyratory movement of the fluid around said axis.

Preferably, the guide members delimit at least a first channel and a second channel, the device being able to be implemented so that the fluid is introduced into the intermediate cavity via the first channel and that the part of the fluid conveyed towards the cavity sampling can be evacuated outside the device through the second channel via at least one of the slowing cavities.

In one embodiment, the device comprises a surface delimiting the at least one peripheral opening, this surface having one or more radii of curvature.

One or more radii of curvature make it possible to increase the distance traveled by the fluid during its introduction into the intermediate cavity and/or to promote the aerodynamics of the device.

In one embodiment, the at least one peripheral opening is configured so that, when it is introduced into the intermediate cavity, the fluid moves along a trajectory comprising a component oriented in a first direction along said axis, the device being configured so that, during its delivery from the intermediate cavity to the sampling cavity, the fluid moves along a trajectory comprising a component oriented in a second direction along said axis, the second direction being opposite the first direction.

The invention also relates to an instrument for measuring particles in a gaseous fluid, comprising an admission device as defined above.

This instrument can be intended to be stationary or to be moved.

Thus, according to a first variant embodiment, the instrument forms a ground station.

According to a second variant embodiment, the instrument is intended to be embarked on board a land vehicle such as a tram, a floating structure or an aircraft.

In the context of this second variant, the invention also relates to an aircraft comprising a measuring instrument as defined above.

In a preferred embodiment, the aircraft is a drone.

Other advantages and characteristics of the invention will appear on reading the detailed, non-limiting description which follows.

The following detailed description refers to the attached drawings in which:

is a schematic view of a measuring instrument comprising an admission device according to the invention;

is a schematic perspective view of the admission device of the ;

is a schematic cross-sectional view of the air intake device .

Detailed Description of Embodiments

Figures 1 to 3 include a frame D1, D2 and D3 respectively defining a first direction, a second direction and a third direction orthogonal to each other.

He is depicted on the an instrument intended to assess the quality of a gaseous fluid. In the following description, the fluid is atmospheric air. The invention can however be implemented to carry out a measurement on another type of fluid.

The instrument of comprises on the one hand a main module 1 provided with a casing 2 and various components (not shown) which are housed in the casing 2, in particular a detection component (see below), a supply component, a analysis, storage and/or data transfer unit and a cooling unit, possibly including a Peltier system.

In a manner known per se, the detection member comprises in this non-limiting example a detection chamber, a light source, for example laser, a low-flow suction pump, typically of the order of 0.132 m ³ /h , making it possible to move a sample of air through the detection chamber so as to subject this sample of air to the light beam generated by the light source, and a photodetector configured to detect variations in luminosity associated with the passage of solid particles present in the sample.

In this example, the detection member is configured to detect the presence of solid particles having a size less than or equal to 12 μm.

In a variant embodiment, the casing 2 can optionally form a Faraday cage in order to reduce the electromagnetic disturbances.

The instrument of further comprises an admission device 3 mounted at the head of the main module 1.

The invention relates more specifically to this admission device 3, which is represented in isolation in FIGS. 2 and 3. Of course, the admission device 3 described below, or more generally any similar admission device conforming to the invention, can be used to admit a gaseous fluid into a system different from that shown in the .

The device 3, also called "sampling head", is provided to take air from the environment of the instrument and constitute the said air sample which is the subject of the measurement carried out within the main module 1.

In this example, the device 3 is made by additive manufacturing.

In order to facilitate its description, the device 3 is described below, with reference to Figures 2 and 3, distinguishing different parts of this device 3, in this case three parts 4, 5 and 6 called "main parts" and parts 7A and 7B forming wall elements. These different parts are arranged so as to delimit between them different cavities making it possible to constitute said air sample under conditions which make it possible to obtain reliable measurements.

The first main part 4 extends along an axis A1 parallel to the first direction D1.

In this example, axis A1 forms an axis of symmetry of part 4.

In general, part 4 comprises a lower part 8, an upper part 9 and an opening which crosses it right through axially, that is to say along the axis A1.

The lower part 8 of part 4 has a threaded outer surface provided to cooperate with a threaded inner surface of an orifice (not shown) of the main module 1, so as to be able to fix the device 3 on the module 1 according to the configuration illustrated. on the .

With reference to the , the upper part 9 of the part 4 has a lower surface 10, an upper surface 11, an internal surface 12 and an external surface 13.

The lower surface 10 is substantially perpendicular to the axis A1 and is intended to bear against an upper surface of the main module 1 when the device 3 is fixed on this module 1. The seal can be improved by interposing between these surfaces a seal.

The upper surface 11 defines an upper end of the part 4, opposite the lower end of the part 4 which is formed by the lower threaded part 8.

The inner surface 12 of the upper part 9 delimits a portion of said opening passing axially through the part 4 so that this opening portion has a circular section whose diameter decreases overall from the upper end of the part 4 to the opposite end of the upper part 9, that is to say substantially at the level of the lower surface 10, i.e. from the top to the bottom of the . In other words, the opening portion which passes axially through part 4 has a generally frustoconical geometry.

The outer surface 13 of part 4 also has a globally frustoconical geometry but whose section decreases axially in the opposite direction. Indeed, the diameter of the upper part 9 of the part 4 decreases overall from the lower surface 10 to the upper surface 11, that is from the bottom to the top of the .

In a non-limiting way, the outer surface 13 of the part 4 has a single radius of curvature.

In this particular example, it also has a geometry making it possible to ensure aerodynamic continuity with an external surface 2A formed by the casing 2 of the main module 1 when the device 3 is assembled with the main module 1 (see ).

Considering that the radius of curvature of the outer surface 13 of the part 4 is positive, the outer surface 2A of the casing 2 has a negative radius of curvature.

The geometry of part 4, a fortiori in combination with that of casing 2, makes it possible in particular to promote the admission of air into device 3.

With reference to the , part 4 comprises in this example two annular collars 14 and 15.

Collars 14 and 15 are formed on internal surface 12 of part 4 by projecting radially inwards. Each of the collars 14 and 15 thus constitutes a member for local restriction of the diameter of the opening passing through the part 4.

In this example, the collar 14 extends at the level of the upper end of the part 4 so as to form part of the upper surface 11.

The collars 14 and 15 are axially spaced from each other by a distance X1.

In this example, the distance X1 is less than a total dimension X2 of the upper part 9 of the part 4. The dimension X2 corresponds to the axial distance between the lower surface 10 and the upper surface 11. In a non-limiting manner, the distance X1 is here less than a third of the distance X2.

Concerning the second main part 5 of the device 3, this also extends along an axis A1 which also forms an axis of symmetry of this part 5.

In general, part 5 comprises an upper part 16, a hollow tapered part 17 and a stud 18 centered on axis A1.

The upper part 16 forms in this example a plate defining an inner surface 19 circular.

The frustoconical part 17 of the part 5 extends axially from a periphery, that is to say from a radial end, of the upper part 16, in the direction of the first part 4, defining a surface inner surface 20 connected to the inner surface 19 of the upper part 16 by a fillet 21. The fillet 21 in particular provides a smooth transition capable of reducing aerodynamic disturbances.

The inner surface 20 of the frustoconical part 17 has a geometry similar to that of the outer surface 13 of the first part 4, so that these surfaces 13 and 20 define radially between them a circular opening 50, called "peripheral opening", which extends circumferentially around axis A1.

In this example, the peripheral opening 50 is compartmentalized by the wall elements 7A, which for this purpose are distributed circumferentially around the axis A1 so as to define visible channels between them on the .

Thus, the peripheral opening 50 is in this example formed of a plurality of channels spaced from each other around the axis A1.

With reference to the , the stud 18 extends for its part in line with the internal surface 19 formed by the plate 16, in the direction of the first part 4 so as to extend radially inside the opening passing through the first part 4 .

The stud 18 comprises an outer surface 24 connected to the inner surface 19 of the upper part 16 by a fillet 22, which in particular ensures a smooth transition capable of reducing aerodynamic disturbances.

The internal surface 19 formed by part 5 and the upper surface 11 formed by part 4 are axially spaced from each other by a distance X3 so as to define between them a cavity 51, called "intermediate cavity".

The intermediate cavity 51 is thus a substantially annular cavity delimited radially on the inside by the stud 18 and the fillet 22 and, radially on the outside, by a part of the internal surface 20 formed by the frustoconical part 17 of the part 5 and by leave 21.

In this way, the intermediate cavity 51 is in fluid communication with the peripheral opening 50.

The stud 18 further comprises an annular collar 25 formed on its outer surface 24. The collar 25 projects radially outwards.

In this non-limiting example, the collar 25 extends axially between the collars 14 and 15, close to the collar 15.

Regarding the third main part 6, this comprises an upper part 26 which is generally annular and a lower part 27 which is hemispherical.

The upper part 26 of part 6 extends radially between the stud 18 of part 5 and the internal surface 12 formed by the upper part 9 of part 4.

The upper part 26 of part 6 has an upper surface 28 defining an upper end of part 6, opposite its lower end formed by hemispherical part 27.

In this example, the upper surface 28 formed by the part 6 is located axially at the same level as the upper surface 11 formed by the part 4. In particular, the surfaces 11 and 28 are located in the same plane normal to the axis A1 .

Part 6 comprises in this example an internal annular collar 29 and two external annular collars 30 and 31.

The internal collar 29 is formed on an internal surface 32 of the upper part 26 of the part 6, so as to extend radially inwards, at the level of the upper end of the part 6 so as to form a part of the upper surface 28.

The collar 29 locally forms a restriction of the internal diameter of the upper part 26 of the part 6.

The collar 29 of part 6 and the collar 25 of part 5 are axially spaced from each other by a distance X4, which in this particular example is less than the distance X1.

The external collars 30 and 31 extend for their part projecting radially outwards, vis-à-vis the collars 14 and 15, respectively, being spaced apart from each other by a substantially identical distance. at distance X1.

Concerning the hemispherical part 27 of part 6, this is in this example a wall comprising orifices 33 which pass right through it.

Wall elements 7A provide the mechanical connection between parts 4 and 5.

The mechanical connection between parts 4 and 6 is ensured by two wall elements, not shown, which extend radially between the upper part 26 of part 6 and the upper part 9 of part 4.

With reference to the , the device 3 thus forms an opening 50, which comprises various channels circumferentially delimited by the wall elements 7A, and various cavities, or chambers, in fluid communication with each other. These cavities include said intermediate cavity 51, two cavities 52 and 53 called “deceleration cavities”, a cavity 54 called “reception cavity” and a cavity 55 called “sampling cavity”.

Cavity 52 is a circular cavity bounded radially inward by stud 18 and radially outward by upper part 26 of part 6. Axially, cavity 52 extends between collars 25 and 29.

In the present description, it is considered that the radial space between the collar 29 and the stud 18 as well as the radial space between the collar 25 and the upper part 26 of the part 6 form part of the cavity 52. In this sense , the collars 25 and 29 constitute section restriction members of the cavity 52.

The cavity 53 is also a circular cavity, which is delimited radially towards the inside by the upper part 26 of the part 6 and radially towards the outside by the internal surface 12 formed by the upper part 9 of the part 4. Axially , the cavity 54 extends between the collars 14 and 15.

In the present description, it is considered that the radial space between the collars 14 and 30 and the radial space between the collars 15 and 31 are part of the cavity 53. In this sense, the collars 14, 15, 30 and 31 constitute section restriction members of the cavity 53.

The cavities 52 and 53 as well as the opening 50 thus extend concentrically around the axis A1.

Each of the cavities 52 and 53 is also in fluid communication with the intermediate cavity 51, via the radial space between the stud 18 and the collar 29 for the cavity 52 and via the radial space between the collars 14 and 30 for the cavity 53.

The cavity 54 extends axially in the direction of the lower part 8 of the part 4 the cavity 52 being delimited by the hemispherical part 27 of the part 6.

Cavity 54 is thus in fluid communication with cavity 52 via the radial space between collar 25 and upper part 26 of part 6.

Cavity 55 extends axially in the direction of lower part 8 of part 4, cavity 53 also being delimited by hemispherical part 27 of part 6.

The orifices 33 made in the hemispherical part 27 establish fluid communication between the cavities 54 and 55.

The intermediate cavity 51 and the sampling cavity 55 are therefore spaced from each other along the axis A1 while being in fluid communication with each other on the one hand via the slowing down cavity 52 and the reception cavity 54 and, on the other hand, via the slowing cavity 53.

The cavities 52 and 53 are said to be slowing down taking into account in the first place the axial spacing that they define between the intermediate cavity 51 and the sampling cavity 55, producing an elongation of the path of the air flow between the cavities 51 and 55.

This slowing down is favored by the geometry of the device 3 since an air flow penetrating the peripheral opening 50 in the direction of the intermediate cavity 51 moves along a trajectory comprising an axial component oriented along a first direction S1, while the displacement of this flow from the intermediate cavity 51 towards the sampling cavity 55 follows a trajectory having an axial component oriented in a second direction S2 opposite to the direction S1, and vice versa.

A fortiori, the section restrictions formed by the collars 14, 15, 25, 29, 30 and 31, which define baffles, also cause a slowing down of the air flow by creating within the cavities 52 and 53 plenum chambers .

In operation, an airflow typically enters through at least one of the channels of the peripheral opening 50, in this example located to the left of the , to reach the intermediate cavity 51. The wall elements 7A, also called "fins", form guiding members of this flow, making it possible to reduce a gyratory displacement of the flow within the opening 50 by thus directing it towards the intermediate cavity 51.

In the intermediate cavity 51, part of this flow is capable of bypassing the pad 18. This phenomenon is attenuated by the presence of the wall elements 7B, also called "fins", which extend in this example in line with the surface internal 19 of the plate 16 and the stud 18 and which are distributed circumferentially around the axis A1.

Ultimately, part of the flow is driven from the intermediate cavity 51 to the withdrawal cavity 55, mainly via the slowing cavity 52 and the reception cavity 54, and possibly via the slowing cavity 53 depending on the speed of stream entry.

The device 3 makes it possible to constitute in the sampling cavity 55 said sample of air which reaches in this cavity 55 a speed lower than that of the flow in the intermediate cavity 51.

Part of the air present in the sampling cavity 55 can thus be sucked towards said detection chamber via the portion 56 of the opening of the lower part 8 of the part 4.

In a manner known per se, the air passing through the detection chamber is expelled outside the instrument via an opening (not shown) of the main module 1.

Another part of the air present in the sampling cavity 55 tends to come out of the device 3 by flowing mainly through the cavity 53, the intermediate cavity 51 then at least one of the channels of the peripheral opening 50, in this example located to the right of the , i.e. mainly by the shortest path. Depending on the atmospheric conditions and the relative wind speed, part of the air present in the sampling cavity 55 may possibly come out of the device 3 by flowing through the orifices 33 of the wall 27, the cavity 54, the intermediate cavity 51 then the peripheral opening 50.

In general, the device 3 is inexpensive, requires low maintenance and, in terms of performance, makes it possible to promote the absorption of fine particles, in particular for sizes ranging up to 12 μm, while respecting the distribution of the particles present in the atmosphere.

Tests of the device 3 in the wind tunnel have shown in particular that this device makes it possible to constitute in the sampling cavity 55 an air sample capable of being the subject of a satisfactory measurement, including in the presence of a sustained wind, in l occurrence up to 18.5 m/s.

The geometry of the device 3 also allows it to be operational in the event of a change in wind direction, taking into account in particular the circularity of the cavities and the circumferential repair of the channels of the peripheral opening 50.

The device 3 makes it possible to dispense with a high-flow suction device, which makes it possible to lighten the total mass of the instrument. In this respect, the instrument of has a total mass not exceeding 1100 g.

The device 3 can thus be implemented within an instrument that can be embarked on board an aircraft of the drone type for flights in urban areas, for example with a view to carrying out three-dimensional atmospheric analyses. For example, a drone thus equipped can fly over an area to be studied and the measuring instrument can be configured to take measurements continuously so as to restore a measurement average at a given time interval, for example every ten seconds.

In such an application, said power member of the measuring instrument can be a battery. Alternatively, in the case of a stationary application, the supply member can comprise an external supply unit, for example removable.

Of course, the invention is not limited to such applications nor to the admission device 3 described above with reference to Figures 2 and 3.

For example, in an embodiment not shown, the device 3 may be devoid of the hemispherical wall 27, in which case the slowing cavity 52 may be in direct fluid communication with the sampling cavity 55, and not via the receiving cavity 54.

In another embodiment not shown, the device 3 can comprise a means of assembly different from the threaded part 8. For example, the part 4 can be devoid of the part 8 and the device 3 can be configured to be fixed to a module such as module 1 by fastening means such as pins and/or screws, or even by gluing. In another variant, the part 8 of the device 3 can be threaded not externally but internally, with a view to its assembly with an externally threaded tube.

Furthermore, the device 3 can be produced by separate manufacture of some of its parts, for example the main parts 4, 5 and/or 6, and by subsequent assembly of these parts previously produced by additive or subtractive manufacturing.

More generally, the geometry of the device 3 and of its various cavities may be different from that illustrated in FIGS. 2 and 3 and the section restriction members described above, namely the collars 14, 15, 25, 29, 30 and 31, can be different in number and/or shape.

Claims (10)

Device (3) for admitting a gaseous fluid with a view to carrying out a measurement of particles present in the fluid, characterized in that it comprises:
– a sampling cavity (55),
– an intermediate cavity (51),
– a peripheral opening (50) configured to allow introduction of the fluid into the intermediate cavity (51) and
– two slowing cavities (52, 53) which are each in fluid communication with the intermediate cavity (51) on the one hand and the sampling cavity (55) on the other hand so as to convey part of the fluid present in the intermediate cavity (51) towards the sampling cavity (55) with a view to forming a sample of the fluid in the sampling cavity (55),
the intermediate cavity (51) and the sampling cavity (55) being spaced apart along an axis (A1), the slowing cavities (52, 53) and the peripheral opening (50) extending concentrically around this axis (A1). Device (3) according to claim 1, comprising a receiving cavity (54) in fluid communication with one (52) of said retarding cavities extending radially inside the other (53) of said retarding cavities relative to said axis (A1), the device (3) comprising a wall (27) separating the sampling cavity (55) and the reception cavity (54) from each other, this wall (27) comprising orifices (33) establishing fluid communication between the receiving cavity (54) and the sampling cavity (55). Device (3) according to Claim 1 or 2, comprising one or more members (14, 15, 25, 29, 30, 31) for restricting the section of one and/or the other of the slowing cavities (52 , 53). Device (3) according to Claim 3, in which the section restriction member(s) (14, 15, 25, 29, 30, 31) comprise one or more annular collars. Device (3) according to any one of Claims 1 to 4, comprising members (7) for guiding the fluid arranged in the at least one peripheral opening (50) so as to guide the fluid towards the intermediate cavity (51) . Device (3) according to Claim 5, in which the guide members (7) delimit at least a first channel and a second channel, the device (3) being able to be implemented so that the fluid is introduced into the intermediate cavity (51) through the first channel and that the part of the fluid routed to the sampling cavity (55) can be evacuated outside the device (3) through the second channel via at least one of the slowing down cavities (52, 53 ). Device (3) according to any one of Claims 1 to 6, comprising a surface (13) delimiting the at least one peripheral opening (50), this surface (13) having one or more radii of curvature. Device (3) according to any one of Claims 1 to 7, in which the at least one peripheral opening (50) is configured so that, when it is introduced into the intermediate cavity (51), the fluid moves along a trajectory comprising a component oriented in a first direction (S1) along said axis (A1), the device (3) being configured so that, when it is routed from the intermediate cavity (51) towards the sampling cavity (55 ), the fluid moves along a trajectory comprising a component oriented in a second direction (S2) along said axis (A1), the second direction (S1) being opposite the first direction (S2). Instrument for measuring particles in a gaseous fluid, comprising an admission device (3) according to any one of Claims 1 to 8. Aircraft comprising a measuring instrument according to claim 9.