FR2770300A1 - Instrument for measuring fluid velocity and solid or liquid particle flow in a fluid or vacuum - Google Patents

Abstract

A sealed chamber in the form of a thin pipe has a rigid membrane covering one end and a small microphone (bandwidth 100-18000 HZ) located at the other. The chamber is filled with air. Particles or fluid striking the outside of the chamber produce an acoustic signal at the microphone. The resultant microphone output is filtered by an electronic circuit leaving only the 200 Hz and 14 kHz components. The 200 Hz measures fluid velocity and the 14 kHz measures particle flow.

Description

Description
Technical field of the invention
Measuring tool.

State of the art
The invention relates to an instrument for measuring the flow rate of a fluid and the flow of solid or liquid particles in motion in a fluid or vacuum. This problem arises, for example, in industry for process control, or in the area of natural hazards. In particular, in this area, knowing the quantities of snow transported locally by the wind is crucial information for the study, prevention and forecasting of avalanche risks. No technical solution makes it possible to automatically and continuously know the amount of snow transported by the wind on a mountainous site:
trap devices require manual counting of the quantity of particles
of snow captured,. existing automatic systems allow only an all-or-nothing measurement of the presence of
solid particles in the air, optical systems are often disturbed by the properties
optics of snow or frost or ice on components; characteristics
electromagnetic systems do not allow to consider their generalization on a site.

The instrument according to the invention is typically intended to be placed in a flow of fluid such as wind, charged or not with solid or liquid particles such as snow, rain or sand. Its function is to automatically and continuously deliver information, for example in the form of an electrical signal, on the speed of the fluid relative to the instrument and on the flow of solid or liquid particles interacting with the instrument.

Statement of the invention
The invention is a mechanical-acoustic instrument for automatically and continuously measuring the speed of flow of a fluid and the flow of solid or liquid particles possibly in motion in this fluid or in vacuum. The invention is composed of a mechanical part such as a spheroid or parallelepiped wall or of another shape, an electroacoustic or opto-acoustic part and an electric part. The mechanical part is an element of the metal tube or plastic or other material type, of cylindrical, rectangular or other section, forming one or more cavities. The wall may include a deformable part in the form of a thin or thick, metallic, plastic or other material membrane. The electroacoustic part consists of a gas which occupies the cavity (ies) of the mechanical part and at least one acoustic pressure transducer arranged in a precise place of a cavity, located according to the shape of this one either wall outcrop is at another point in the cavity. The electrical part is a circuit possibly protected by a box, the input of the circuit is connected to the sound pressure transducer (s) in the cavity (ies), and the output includes a plug, a cable, an antenna or any other means of connection or transmission of information.

The vibrations induced on the mechanical part either by the shocks of solid or liquid particles in
movement either by the friction of a fluid vary the acoustic pressure of the gas contained in the cavity (ies). The electroacoustic or opto-acoustic transducer (s) transform (s) these variations in acoustic pressure into electrical or optical signals. These signals are amplified and filtered by the electrical part in at least two distinct frequency bands, one typically
less than 1000 Hz and the other typically greater than 1000 Hz. In these frequency bands, the voltage or the electric current are linked - by a mathematical expression which depends on the form of
the cavity (ies) and the fluid (s) in the cavity (ies) - at the speed of the fluid relative to the device, respectively, and at the flow of solid or liquid particles striking the device.

 The technical characteristics specific to the invention are a mechanical part forming walls defining one or more cavities comprising a gas and at least one electroacoustic or optoacoustic transducer; positioning in a precise location (s) of the transducer (s) in the cavity (ies), electrical filtering in frequency bands distinct from the electrical signals delivered by the transducer (s). This device makes it possible - by mechanical-electroacoustic transduction of the impact energy of solid or liquid particles and of the friction pressure of the fluid against the walls of the device - to obtain two independent pieces of information: the speed of the fluid with respect to the device with which it is in contact, the flow of solid or liquid particles striking the device.

Presentation of an embodiment
One embodiment (see Figure 1) of the mechanical part is an aluminum tube (1) of length 1 m, internal diameter 30 mm, thickness 1 mm. A microphone (2) of small diameter (typically 4 mm), with a bandwidth of 100 Hz -18,000 Hz, and with a pressure action mode, is positioned at the base of the tube filled with air (3) by a retaining ring (4) made of aluminum or another material so that its axis is 3 mm from the inside wall of the metal tube. The retaining ring is fitted into the tube and fixes the microphone so that the acoustic seal is very good at this end of the tube. At the other end of the tube, a sealed shutter plug (5), made of aluminum or another material, is also fitted. The microphone cable (6) is connected to an electronic circuit (7) contained in a protective case (8). The electronic circuit amplifies and filters the electrical signal in two frequency bands: the first centered at 200 Hz, the second at 14 kHz.

The housing has at its outlet a socket (9) delivering the effective electric voltages in these two frequency bands. The first provides the information corresponding to the speed of the fluid in which the device is located, the second provides the information corresponding to the flow of solid or liquid particles striking the tube.

Potential applications
The device according to the invention applies to any measurement of fluid speed or flow of solid or liquid particles. It applies in particular - to the measurement of snow or sand flows transported by the wind - to the measurement of chips, flakes or other solid or liquid particles flows in industrial conduits or other transport of particles such as for example those by gravity in silos - in the field of air or land transport to the detection of the presence of solid or liquid particles in the air such as hail, rain or snow precipitation.

Claims (10)

 acoustic.  against the walls of a closed cavity containing a gas and in which a pressure is measured  determines the speed by mechanical-acoustic filtering of the energy produced by the friction of the fluid  Claims 1) Device for measuring the flow speed of a fluid, characterized in that the device 2) Device for quantitative measurement of the flow of solid or liquid particles in motion in a  fluid or vacuum, characterized in that the device determines the flow of particles by filtering  mechanical-acoustic energy produced by the impact of particles against the walls of a cavity  closed container of a gas and in which a sound pressure is measured. 3) Device for simultaneously measuring the speed of a fluid and the flow of solid or liquid particles  in said fluid, characterized in that the device determines the speed by mechanical filtering  acoustics of the energy produced by the friction of the fluid against the walls of a closed cavity  containing a gas and the flow of particles by mechanical-acoustic filtering of the energy produced by  the impacts of the particles against the walls of said cavity, in which a pressure is measured  acoustic. 4) Device for simultaneously measuring the speed of a fluid and the flow of solid or liquid particles  in said fluid according to claim 3, characterized in that the sound pressure is measured  by means of an electroacoustic transducer whose output is filtered in two bands of  distinct frequencies, a first band to determine the speed of the fluid and a second  tape to determine the flow. 5) Device according to one of claims 14, characterized in that the acoustic pressure is  measured using an electroacoustic transducer positioned flush with a wall to  inside the cavity. 6) Device according to one of claims 1-5 characterized in that the cavity is a section tube  cylindrical, square or rectangular. 7) Device according to one of claims 1-5, characterized in that the shape of the wall is  spheroid, parallelepiped or conical. 8) Device according to one of claims 1-7, characterized in that the cavity is compartmentalized. 9) Device according to one of claims 1-8, characterized in that the wall is metallic or in  plastic material. 10) Device according to one of claims 1-9 characterized in that one (or more) part (s) of the  wall is (are) made of a membrane of the same material as the wall or another  material.