FR2716387A1 - Device and method for the production of particles of controlled particle size suspended in a gaseous medium and application for the manufacture of fibrous materials. - Google Patents

Abstract

Device for the production of controlled grain size particles suspended in a gaseous medium, of the type comprising an enclosure (1) provided with a carrier gas inlet at a pressure above the atmospheric pressure, at least one opening for injecting the product to be pulverized at least one outlet for injecting a gaseous mixture consisting of a suspension of particles of products to be pulverized. The device comprises means of measuring incoming enthalpy, means for measuring outgoing enthalpy and a computer for thermodynamically controlling, under steady conditions, the exchange process within the enclosure (1). The invention also concerns the application of such a device for seeding from a blower system, and for surface and volume seeding of a porous material.

Description

The present invention relates to a device

  for the production of particles of controlled particle size suspended in a gaseous medium. Such a device is intended for the production of fumes for the analysis and visualization of the aerodynamic behavior of models in the wind tunnel, for show effects, or for any industrial application requiring the projection of calibrated particles, for example for the treatment of surface of materials. Among the industrial applications of such devices, there may be mentioned surface coating or volume of materials for physicochemical or mechanical treatments.

  One known in the state of the art various artificial fulmination facilities including using oily products.

  Smoke generators are known in the state of the art and usually comprise an enclosure having an inlet for the carrier gas at a pressure greater than atmospheric pressure, at least one injection port of the product to be sprayed and at least one an outlet for ejecting a gaseous mixture consisting of a suspension of particles of the product to be sprayed.

  One of the difficulties is controlling the density and opacity of the smoke.

  A smoke generating device is described in US Patent Application 765,214 which gave rise to the document "United States Statutory Invention Registration" H1124 discloses a smoke generator having a venturi tube opening into a low pressure chamber upstream of the combustion zone. . A pressurized gas comes from a pressurized tank connected by a hose to fulmigateurs provided with a diffuser. An electronic management center has the effect of increasing the safety and reliability of the operation of the smoke.

  Such a device of the state of the art is sensitive to variations in carrier gas supply pressure or mineral oil, and fluctuations in the supply temperature or fumes ejection.

  Another document of the prior art, the French patent FR2428471, discloses a nebulizer whose reactor consists of a two-piece envelope having a lower section on which stands a nozzle directed upwards and a wall section directed towards the high, secured to the lower section and surrounding the nozzle. A tubular member surrounds the nozzle. As for the previous devices, the quality of the ejected flow is not controlled and therefore does not guarantee the permanence of the particle size and flow, nor optimize the rate of flue gas production.

  The object of the present invention is to provide a particle generator of adjustable and calibrated dimensions, to provide a large and constant flow. For this purpose the reaction chamber is constituted by a hollow body provided with heating means and having at one of its ends at least one injection nozzle of the product to be sprayed and at least one base for injecting the carrier gas. said nozzle being oriented so that the projection of its median axis on a transverse plane is substantially tangent with a circle coaxial with the injection nozzle of the product to be sprayed, the median axis of the nozzle forming with said transverse plane an angle less than 60 degrees, the enclosure having at its end opposite to the injection nozzles a conical portion terminated by a central ejection orifice.

  Preferably, the device according to the invention comprises means for measuring the incoming entalpie, means for measuring the outgoing entalpie and a calculator for the thermodynamic regulation, in steady state, of the exchange process inside. of the enclosure.

  This embodiment makes it possible to guarantee the characteristics of the output stream, and to make them independent of the temperature and pressure variations of the constituents injected into the reaction chamber.

  According to an advantageous variant, the computer controls at least one of a valve controlling the flow of carrier gas at the inlet of the enclosure, a valve controlling the flow of the product to be sprayed at the entrance of the enclosure , a means for heating the carrier gas or the product to be sprayed, a valve controlling the outlet flow rate, or a means of thermal supply to the chamber, to maintain constant the difference between the cumulative entalpy of the carrier gas injected into the enclosure and the product to be sprayed in the enclosure on the one hand, and the entalpie of the output mixture on the other hand.

  Advantageously, the device comprises a first flow sensor for measuring the flow of carrier gas introduced into the chamber, a second flow sensor for measuring the flow of the product to be sprayed into the chamber, the device further comprising a calculator for controlling a first valve disposed at the outlet of the carrier gas reservoir, a second valve disposed at the outlet of the spray tank and a third valve disposed at the outlet of the enclosure, according to a servo law determined for the production of a specific flow.

  Preferably, the device comprises a reservoir of carrier gas connected to the enclosure via a regulator controlled by the computer and a heat exchanger controlled by said computer, a reservoir of spray fluid supplying the enclosure by via a high-pressure pump and a heat exchanger controlled by the computer, means for heating the enclosure controlled by the computer and an output valve controlled by the computer.

  The invention also relates to a method for depositing product particles in a porous mass, in particular a process for depositing polymerizable products in a fibrous material.

  The methods according to the state of the art consists in depositing an excess of products in the material in order to guarantee a good impression in the thickness of the material, and then to proceed with the washing of the material before passing through the polymerization chamber. This process causes significant pollutant discharges both in the washing water and in the atmosphere.

  For example, the French patent FR2682403 describes an insulating material based on glass wool, obtained by grinding a felt comprising a formaldehyde binder polymerized in an oven, at a rate of between 1 and 4.5% of the total mass of the material, whose glass fibers have a micronaire between 2.2 and 3.1 under 5 g and preferably of the order of 2.5 under 5 g, the average weight of this insulating material deposited by square meter being less than 1800 grams.

  French Patent FR2640546 discloses a process for treating mineral wool products in which the mineral wool is collected to form a mattress on a conveyor belt, conducted to a conformation and polymerization chamber of the binder comprising two complementary conveyors of calibration and transport constituted by a plurality of perforated articulated elements of the pallet type. According to the invention, the speeds of the two conveyors are different, the corresponding speed difference over the entire length of the enclosure to an offset of a length equivalent to at least the width of a pallet so that one of the faces of the mattress is smoothed during the shaping of the mineral wool product.

  Another document of the prior art, the European Patent EP263029 relates to an insulating material consisting of fibers including glass or rock coated with a polymer based on modified polyvinyl alcohol, able to serve as a base material to achieve a coating on a support by simultaneous projection of said fibers thus coated mixed with a crosslinking agent and water.

  This document also proposes a process for preparing said fibers to make them suitable for being projected in this way.

  One of the aims of the invention is the reduction of losses of fiber binding products in order to limit atmospheric or fluvial pollution, and to reduce the cost of production. This result is obtained by the implementation of the plant according to the invention for the nucleation of the binder products, which makes it possible to obtain a constant quality of the particles and a mean diameter less than that of the particles obtained by the processes according to the invention. state of the art. The process thus allows a better seeding of the binder product before polymerization due to the increase in the average path which makes it possible to improve the depth of the penetration of the particles, and especially to reduce the incidence of the depth on the density of the particles. deposited particles. Thus, it is no longer necessary to carry out an excess seeding to ensure a minimum density in the deepest areas of the material.

  The invention also relates to the application of such a device for the production of a laminar flow of calibrated particles for flow visualization in a ventilation chamber or in a wind tunnel.

  Such a device makes it possible to control the characteristics of the particles and thus to proceed with the seeding of small size calibrated particles under low pressure.

  It also relates to the application of such a device for producing a supersonic flow of calibrated particles having a high Reynolds number for flow visualization in a ventilation chamber or in a wind tunnel.

  Such a device indeed makes it possible to seed cryogenic wind tunnels in which there is a pressure higher than the atmospheric pressure and a low temperature, for operation in similarity of Reynolds.

  The invention relates more particularly to a process for the volume or surface seeding of a porous material, in particular of a fibrous web with a polymerizable binder product of controlled particle size consisting in causing the spraying of said binder product in an enclosure having a port of the entry of the carrier gas at a pressure above atmospheric pressure and in that the stream of particles in suspension delivered by an injection port of the nucleated product is directed on the sheet of porous material.

  Preferably, the spraying of said binder product is caused in an enclosure having an inlet for the carrier gas at a pressure greater than atmospheric pressure, in that the incoming entalpie of the carrier gas is determined on the one hand and the binder product introduced into the chamber on the other hand, the outgoing entalpie of the nucleated product and in that one carries out, in steady state, the thermodynamic regulation of the exchange process inside the enclosure .

  The invention also relates to an installation for the volume or surface seeding of a porous material, in particular of a fibrous web with a polymerizable binder product of controlled particle size comprising a reservoir of binder product feeding via a pump and a heat exchanger at least one injection nozzle in a chamber, the installation further comprising a reservoir of carrier gas chemically neutral with respect to the binder product, the gas reservoir being connected supplying the enclosure via a regulator controlled by the computer and a heat exchanger, the enclosure comprising means of heating the chamber controlled by the computer and an output valve controlled by the computer, the installation further comprising means for the projection of the nucleated particles onto the fibrous material The invention will be better understood on reading the description which follows, making reference to the x appended drawings o: - Figure 1 shows a block diagram of the device according to a non-limiting embodiment of the invention; - Figure 2 shows a sectional view of the reaction chamber according to the invention.

  Figure 1 shows a schematic view of the device according to a non-limiting embodiment of the invention.

  It comprises a reaction chamber (1) to which are connected: - conduits (2) for injecting the carrier gas - and a conduit (3) for injecting the product to be sprayed - an ejection duct (4).

  The reaction chamber (1) has at the end opposite to the injection pipes (2, 3) an orifice opening into a conduit (4) for ejection of the product in suspension in a gas flow. A set of sensors (13) measures the temperature and the pressure of the mixture at the outlet of the enclosure and delivers signals that are functions of the temperature and the pressure of the mixture at the outlet of the enclosure. A temperature sensor measures the internal temperature of the enclosure (1).

  The carrier gas, for example a neutral gas such as nitrogen or air, is stored in a tank (5). The carrier gas is chosen from gases which are chemically inert with respect to the product to be injected. A slave valve (6) controls the flow of the carrier gas supplying the reaction chamber (1). Before entering the enclosure (1), the carrier gas passes through a heat exchanger (7) and a set of sensors (8) delivering signals which are functions of the temperature, the flow rate and the pressure of the carrier gas to the entrance to the enclosure.

  The product to be sprayed, for example the oil marketed by the company Shell Deltaalab under the trade name ONDINA, is stored in a tank (9). A high-pressure circulation pump (10) ensures the pumping of the product and the supply of the enclosure. The product passes through a heat exchanger (11) for the fluidization and heating of the product before passing through a set of sensors (12) delivering signals that are functions of the temperature, the flow rate and the pressure of the product at the inlet of the product. enclosure (1). This reheating also makes it possible to act on the viscosity of the product before injection.

  The enclosure (1) also includes a temperature sensor measuring the internal temperature, and heating rings (14, 15) surrounding the body of the enclosure.

  The signals from the temperature, flow and pressure sensors (8, 12, 13) are processed by a computer (16) for determining the entalpy of the vector gas injected into the chamber (1) on the one hand , the entalpie of the product to be sprayed at the inlet of the enclosure on the other hand, as well as the entalpie of the mixture at the outlet of the enclosure (1).

  On the basis of these variables, the computer controls various means in order to minimize variations in the difference in enthalpy between the incoming fluids and the outgoing fluid.

  The computer controls in particular the flow of the carrier gas by a controlled valve (6), and the flow of the product entering by the pump (10). It also controls power circuits respectively regulating the operation of the heat exchanger (7) controlling the temperature of the carrier gas and the operation of the heat exchanger (11) controlling the temperature of the product to be sprayed.

  The computer (16) also controls a power circuit (17) controlling the temperature of the heating rings (14, 15).

  The computer also controls a control circuit (18) controlling the operation of the outlet valve (13).

  The servocontrol law can be determined experimentally, by observing the effect of the variation of the following parameters on the quality of the mixture generated by the device: QA Flow of vector gas entering the enclosure TA Temperature of the carrier gas at the preheating output PA Injection pressure of the carrier gas at the inlet of the enclosure (1) QH Flow rate of the product to be sprayed TH Temperature of the product to be sprayed at the outlet of the preheating PH Injection pressure of the product into the enclosure TR Temperature in the tank PR Pressure in the tank QS Output flow.

  The temperature of the chamber will be kept as constant as possible because it is an essential parameter of the good nucleation of the product to be sprayed.

  This implies a low time constant regulation of the electric power supplied to the heating rings, the injection of the carrier gas and the product to be sprayed acting as energy wells.

  The computer acts on the following parameters: - Preheating temperature of the gas set to setpoint - Preheating temperature of the product to be injected set to setpoint - Temperature of the enclosure, in real time - Flow of the incoming carrier gas - Flow of the incoming product Flow outgoing mixture.

  Figure 2 shows a schematic view of the enclosure (1). It has an inlet end (20) of hemispherical shape and a conical outlet end (21).

  It comprises a nozzle (22) for injecting the product to be sprayed arranged on the median axis and oriented axially.

  It further comprises three nozzles (23) for injecting the carrier gas. These nozzles (23) are arranged to create a swirling stream forming a cyclone driving the product to be sprayed to the ejection port (24). For this purpose, the nozzles (23) are angularly distributed over a circular zone, the projection of the axis of the nozzles (23) constituting on a transverse plane perpendicular to the axis (25) of the enclosure a tangent to said circle, and the nozzles (23) forming with this plane an angle of about 30 degrees.

  The following description relates to the application

  of the device for the production of glass wool. It is intended for spraying 60 liters per hour of binder in the form of particles with an average diameter of 0.1 microns, which is three times smaller than the average particle diameter obtained in the installations according to the state of the art.

  The installation comprises a reservoir of a binder, for example a solution of a phenolic compound in water, in a proportion of 20% / 80%.

  The carrier gas reservoir contains air at a pressure of between 2 and 10 bar.

  The efficiency of this plant is about three times higher than the prior art facilities, due to the increased degree of penetration of the particles into the fibrous mass. The particle density is substantially constant as a function of depth, which makes it possible to avoid the projection of excess binder and then to eliminate the surplus in the shallow layers before the polymerization.

  The characteristics of the chamber of the particle generator can be determined by a mathematical method described below, with reference to FIGS. 3 and 4, and concerning the particular application to the seeding of a porous material with a binder product.

  In the following, the study of mass transfers will be determined without taking into account the heat input by the heating rings (15, 16).

  The purpose of this first calculation is to model the variation of kinetic energy of a gas inside the generator. The internal shape of the generator is that of a nozzle of horizontal axis of revolution about an axis x'x.

  The area of the cross section of the generator S (x) is variable along x'x. The flow is assumed without friction at the walls. All the gas particles situated in the slice of thickness dx, with abscissa x, have the same speed W (x) in the same direction as x'x.

  U (x), H (x), P (x), T (x), u (x) respectively represent internal energy, enthalpy, pressure, absolute temperature and mass volume. U (x), H (x) are relative to one mole of gas of molar mass M. U0, Ho0, P0oe To, u0, are the state variables of the gas at the input of the generator (abscissa x = O) of surface S0.U., H1, P, Tl, UI are relative to the output of the abscisseX generator, and S1 area.

  P1 is the ambient pressure at the output of the generator. It is therefore considered, initially, that the fluid stream at the output of the generator has the same pressure as the ambient medium (near instantaneous mechanical equilibrium).

  In steady state when a given mass of gas, for example a mole, enters the generator with the speed W (0). During the corresponding time interval dt, to bring the gas under the constant pressure P0 the external pressing forces provide the work: PoSowodt = PoVo At the output of the generator the gas supplies to the external medium the work: P (, S (, w (, d = P (,) V (,) (in absolute value) Taking into account the macroscopic kinetic energy, the first principle is written: Ul Ec (x) - [Ufo) + E; c (o )] = W + Q with W = PoVo-P (.) V (X), the work exchanges being done only at the input and at the output.

  From o: U (x) + P (X) V (l) + 2MW ("- [Uo + PoV + 2 M (M)] = Q 2 2 M 2 Let H () + M W2 ([Ho + M 2 (xQ (1) o Q (,) represents the amount of heat received by one mole between the abscissae 0 and x, without taking into account the amount of heat Q (x) supplied by the heating rings (15, 16).

  It is considered that the flow is fast enough so that no heat exchange takes place (exchange coefficient of the constituent material of the wall and thermal resistance of the insulator): Q (X) = 0. The transformation undergone by each mole of gas is then assumed adiabatic and reversible, so H + Mwdw = O (2) for a reversible infinitesimal evolution: dH = ÈQ + VdPSi it is adiabatic dH = VdPce which gives in (2):

V

wdw = - dP = -udP (3)

M

  By integrating between abscissa 0 and x: 12 1 2 Pi.) 2 (l) -WJ (O) = - udP (4) P0 where u is the mass volume of gas.

  The gas used is supposed to be perfect. C, and Cv are the molar heat capacities at constant pressure and volume. Cpet Cv are independent of temperature.

  We put Y - P CV and WO = W (O). We are interested in the output speed of the generator.

  The equation of state of the perfect gas gives = RT

P RT 1

hence the mass volume: u = - M

MP

  Since the evolution is adiabatic and T To reversible: r - T p Po0 From o: M RTo pr (5) MPo r Equation (4) then gives: pT- RTp 1 2 12-RT f__p _____ 2 Wi -2wo = WoI tPiI (- Tp (PI-Po T) 2 2 M YPM25in Wl Wo (1) MP [OJ Wi2 _Wo2 + 2YTo 41-IVr7) (6) Application to the generator: Throughout the rest of our study we will ask: Wo = W (o) = 0 With regard to the mass flow D, it is necessary to determine its characteristics.

  Let us calculate the mass flow D at the abscissa x as a function of S (,) the volume of gas passing through the section S (,) during dt is that of the base cylinder S (x) and of height W; dt (cf. 3) The corresponding mass of gas is: = S (x) W (x) dt dm = U (z) we deduce the mass flow rate: D = dn S (x) W (x) dt (7) dt U (o) The mass volume at the output is obtained using the adiabatic relation: pU = constant

I

(PoOr r-1 Ui = bt P ul U o (8)

PI J

  The flow rate at the output is: D = SSlWl vy (9) Uo Finally: D = 1A (y1); Vv lf (10) Uo (y -1) MI / 71 We can put: D = kf (f) = k vr1- 1 r) df The flow passes through an extremum when- = 0 dr df _ y 2 v (v) -y

I-

  d r 1f, j + 1- '_-1 + df 2 v 2l-) d vanishes for r 1) y 2Y) 2 y + 1, that is to say:

Y y 1

  q / = t y + lJ (11) We will check that df> 0 if dy <v, and d <o if ï> / '; dyf It is thus a maximum of f and consequently of D. By replacing in (10) it comes: r + 1 D S1 =, o (2 2 (r- (12) Dma = 0 M y + (2) Application to curve plots (see Figure 4).

  The value W of the gas ejection velocity is calculated for v = v'as a function of y, R, T, M. The quantity ai = T1 represents the propagation velocity

MMT

  of a shock, or speed of sound, in the molar mass gas M, at the temperature T "with Y = CP cv It is known from the experimental point of view that for 0 <v <V the flow rate is constant and equal to the flow rate maximum obtained for vf = Vf.

  Only the curve portion D = f (qV) for if </ <1 is in agreement with the experimental measurements. The ejected gas pressure is equal to the pressure of the ambient medium (low mechanical time constant, very fast equilibrium phenomena) p1 at the outlet of the nozzle generator and as long as V / _ '<<1. On the other hand if 0 <f <i the pressure of the output gas remains equal to P * = / f Po and its speed W1, = W '(PI <v Po) In fact we have: 1- (t - = Y 1 , referring to (6) we obtain the ejection velocity: W = 2 (+ RTi = _ + 2 MTo (y + 1) M y1 M Or = oTiPT1 = Ti (7 + 1) Finally: w = XR = ai (13) | The actual flow curveD = f (q /) is drawn. When the pressure P1 is decreased at the outlet from P0, the ejection speed increases and reaches the speed of sound for the critical speed p * = / f in. This velocity is that of propagation of the shocks in the gas.The depression wave that causes a new lowering of p, can no longer go up the nozzle to give a new distribution of pressure, since its speed is equal to that of the gas flow.

  In order to simplify the writing, note: S the area, P the pressure, u the mass volume, w the velocity, T the temperature at the abscissa x + dx, these values become S + dS, P + dP, w + dw, T + dT.

  Since the flow rate is constant, differentiating (7) gives: dD dS dw of = 0 = - + --- DS wu Hence the relation: dS _ dudw (14) The flow being adiabatic and reversible, according to (3): dw = --- dP (15) by differentiating the relation w dP of the adiabatic p + y- = 0 (16)

COULD

  The relation (14) can be written as follows: - = - + 2dP

S YP W

  dS = dP _1 Pu dP yu _ W2 _ = _-_ + = _ (17) S P Y W 'P YW 2 RT.

  The mass volume is: u = - from the

PM

  setting the number of Mach W2 = YM2 M = YM2PU

M

  From o: YPu = (2 by referring to (17) dS dP _) - W 1 -1 8 SP YW y PM 2 By combining (14) and (16): d = - + dS dwA-1 P = - S WM2- After reduction it comes: dS = (M2 - 1) (20)

S

  If the flow is subsonic, the number of dS dw Mach is less than 1. -is then of the sign opposite to -, S w the section of the nozzle of the generator must decrease with x so that the speed of the gases increases: convergent nozzle . dS

  Conversely, if the flow is supersonic (M> 1, S s dw is of the same sign as - a divergent nozzle is required). w

  To obtain a supersonic flow, a convergent and then a divergent nozzle (type Laval nozzle) will be used. The speed of sound is reached at the neck of the nozzle.

  In the simple case of the use of our generator in subsonic mode, one determines the exact form to be machined inside the enclosure of the generator.

  dS _ = - (1 M2) d s w and S -) = - (1 - M2) ln w - S0 W0 \ V- (I-M2) S = So w Wo be _ = Wo Since M = w

VM we have,

  dS 2 dw s _w s = - T dw wdw is, + qt

M

  S 1 (W2-W2:> In = -Inw ± So Wo 2) RT

M

  The present invention is described by way of non-limiting example. It is understood that the skilled person will be able to achieve various variants without departing from the scope of the invention. 2.0

Claims (7)

R E V E N D I C A T I 0 N S   1 - Device for producing particles of controlled particle size suspended in a gaseous medium, of the type comprising an enclosure (1) having an inlet for the carrier gas at a pressure greater than atmospheric pressure, at least one orifice of injecting the product to be sprayed and at least one outlet for ejecting a gaseous mixture consisting of a suspension of particles of the products to be sprayed, characterized in that the device comprises means for measuring the incoming entalpie, measurement means of the outgoing entalpie and a calculator for the thermodynamic regulation, in steady state, of the exchange process inside the enclosure (1).   2 - Device for producing particles of controlled particle size suspended in a gaseous medium according to claim 1 characterized in that the enclosure (1) is constituted by a hollow body provided with heating means and having at one of its ends at least one injection nozzle of the product to be sprayed and at least one carrier gas injection base, said nozzle being oriented so that the projection of its median axis on a transverse plane is substantially tangent with a coaxial circle with the injection nozzle of the product to be sprayed, the median axis of the nozzle forming with said transverse plane an angle less than 60 degrees, the enclosure (1) having at its end opposite to the injection nozzles a conical portion completed through a central ejection port.   3 - Device for producing particles of controlled particle size suspended in a gaseous medium according to claim 2 characterized in that the computer controls at least one of a valve controlling the flow of carrier gas at the inlet of the an enclosure (1), a valve controlling the flow rate of the product to be sprayed at the inlet of the enclosure (1), a means for heating the carrier gas or the product to be sprayed, a valve controlling the outlet flow rate, or a means of thermal input to the chamber (1), to maintain constant the difference between the cumulative entalpie of the carrier gas injected into the chamber (1) and the product to be sprayed into the chamber (1) on the one hand , and the entalpie of the output mixture on the other hand.   4 - Device for producing particles of controlled particle size in suspension in a gaseous medium according to claim 1 characterized in that the device comprises a first flow sensor for measuring the flow of carrier gas introduced into the chamber (1), a second flow sensor for measuring the flow rate of the product to be sprayed introduced into the chamber (1), the device further comprising a computer for servocontrolling a first valve disposed at the outlet of the carrier gas reservoir; a second valve disposed at the outlet of the spray tank and a third valve disposed at the outlet of the enclosure (1), according to a servo law determined for the production of a specific flow .   - Device for the production of controlled particle size particles suspended in a gaseous medium according to any one of the preceding claims; characterized in that the device comprises a reservoir of carrier gas connected to the chamber (1) via a regulator controlled by the computer and a heat exchanger controlled by said computer, a fluid reservoir to be sprayed supplying the enclosure (1) via a high-pressure pump and a heat exchanger controlled by the computer, means 22.   heating of the enclosure (1) controlled by the computer and an output valve controlled by the computer.   6 - Application of a device for the production of particles of controlled particle size according to any one of the preceding claims, characterized in that it is intended for the production of a laminar flow of calibrated particles for flow visualization in a air chamber or in a wind tunnel.   7 - Application of a device for the production of particles of controlled particle size according to any one of claims 1 to 5 characterized in that it is intended for the production of a supersonic flow of calibrated particles having a high Reynolds number for visualization of flow in a ventilation chamber or in a wind tunnel.   8 - Process for the volume or surface seeding of a porous material, in particular of a fibrous web with a polymerizable binder product of controlled particle size characterized in that the spraying of said binder product is caused in an enclosure (1) having an inlet for the carrier gas at a pressure greater than atmospheric pressure and in that the stream of particles in suspension delivered by an injection orifice of the nucleated product is directed on the sheet of porous material, the process being further characterized in that the incoming entalpy of the carrier gas is determined on the one hand and the binding product introduced into the enclosure (1) on the other hand, the outgoing entalpie of the nucleated product to ensure in steady state, the thermodynamic regulation of the exchange process inside the chamber (1).