GB2025606A

GB2025606A - Device for granulometric analysis of particles in fluids

Info

Publication number: GB2025606A
Application number: GB7829619A
Authority: GB
Original assignee: BERBER V A PERVUSHIN E S MURTA
Current assignee: BERBER V A PERVUSHIN E S MURTA
Priority date: 1978-07-12
Filing date: 1978-07-12
Publication date: 1980-01-23
Also published as: GB2025606B

Abstract

A device for granulometric analysis of particles contained in fluids has a feeding channel 2 communicating with a receiving channel 4 by way of a nozzle 3. The ratio between the diameters of the nozzle and the receiving channel is in the range of 1/4 to 1/7. The receiving channel is provided with transparent windows 5, 6 through which light from a lighting means 7 is directed into the fluid in the channel. A light-sensitive means 8 receives light reflected from particles contained in the fluid and provides with its output a measure of the particle content. The axes of the feeding channel and the lighting means extend perpendicular to the receiving channel axis which is coincident with the axis of the light-sensitive means. The range of the ratio of the diameters mentioned above is found to provide a high accuracy of measurement. <IMAGE>

Description

SPECIFICATION Device for granulometric analysis of particles in fluids The present invention relates to measuring instru repents and, more particularly, to devices for granulometric analysis of particles in fluids, i.e. to devices intended to determine the quantity and size of extraneous particles contained in fluids. The invention is chiefly applicable to the analysis of suspensions of low concentrations, such as the analysis of impurities contained in fuels and lubricants.

The present invention resides in providing a device for granulometric analysis of particles contained in fluids, comprising a feeding channel which communicates through a nozzle with a receiving channel provided with transparent windows to expose the fluid flowing through the channels to a light flux emitted by a lighting means whose optical axis extends at an angle to the axis of the nozzle, and a light-sensitive means for receiving through a separate window light reflected from particles contained in the fluid being investigated, which light-sensitive means is arranged so that its optical axis passes through the point of intersection of the axis of the nozzle and the optical axis of the lighting means, the ratio between the diameters of the nozzle and the receiving channel being in the range of 1/4 to 1/7.

In order to reduce the noise current in this device, it is expedient that the feeding and receiving channels are arranged perpendicular to each other and to have the optical axis of the light-sensitive means coincident with the axis of the nozzle. It is also expedient to have the window transparent to the reflected light in the wall of the feeding channel opposite to the outlet of the nozzle.

In order to reduce the contamination of the device from foreign particles, it is advisable that the feeding and receiving channels and the internal surfaces of the nozzle should be inclined downwards in the downstream direction.

In orderto remove gas bubbles from the fluid being investigated, the receiving channel can be arranged vertically with its inlet at a lower level than its outlet.

The device according to the invention for granulometric analysisof particles contained in fluids makes it possible to investigate both individual samples of fluids and constant flows of fluids without providing a liquid envelope around the fluid under investigation. This feature, in turn, makes it possible considerably to simplify the design of the device and accounts for a high accuracy and efficiency of the analysis.

A better understanding of the present invention will be had from a consideration of the following detailed description of preferred embodiments thereof, taken in conjunction with the accompanying partly diagrammatic drawings, wherein Figure lisa section through a device for granulometric analysis of particles in fluids with inclined channels; and Figure 2 is a section through a device for granulometric analysis of particles contained in fluids with a vertical receiving channel.

According to Figure 1, the device comprises a chamber 1 provided with a feeding channel 2 which communicates through a cone-shaped nozzle of diameter dwith a receiving channel 4 having transparent windows 5 and 6 and of diameter D.

The channel 4 is coaxial with the nozzle 3 and irs axis is perpendicular to the axis of the channel 2. The windows 5 and 6 pass a light emitted by lighting means 7 through the liquid being investigated, which flows in the channel 4. The lighting means 7 comprises a set of lenses 9, a diaphragm 10 and a light source 11. Light passing through the receiving channel 4 is absorbed by a light trap 12. The optical axis of the lighting means 7 is at right angles to the axis of the nozzle 3.

Mounted on the chamber lisa light-sensitive means 8 arranged so that its optical axis passes through the point of intersection of the axis of the nozzle 3 and the optical axis of the lighting means 7.

The light-sensitive means 8 comprises lenses 13, a diaphragm 14 and a light-sensitive element 15 which is a photoelectron multiplier tube. The nozzle 3 serves to form a flow pattern 16 (shown by the dash line) of the fluid to be investigated. The ratio between the diameters d and D of the nozzle 3 and the receiving channel 4, respectively, is in the range of 1/4to 1/7.

The nozzle 3 is arranged at the inlet of the receiving channel 4. The optical axis of the lightsensitive means 8 is coincident with the axis of the nozzle 3. Provided in the wall of the feeding channel 2, opposite to the outlet of the nozzle 3, is a window 17 which is transparent to the light flux reflected from particles contained in the fluid under investigation and received by the light-sensitive means 8.

The feeding channel 2, the receiving channel 4 and the internal surfaces of the nozzle 3 are slanted downward in the direction of the flow of the fluid being investigated.

The taper of the nozzle 3 must be as small as possible to minimise hydraulic losses, although it must not be less than the spatial angle defined by the collimating ray of the light-sensitive means 8.

The embodiment of Figure 2 differs from that of Figure 1 in that the receiving channel 4 is vertical and has its inlet at a lower level than the outlet with the nozzle 3 at the lower portion of the channel 4.

The device of both Figures operates as foilows: The fluid to be analyzed is pumped through the feeding channel 2 (Figure 1) and the nozzle 3 to the receiving channel 4, wherein the flow pattern 16 is produced. In a volume 18 of the fluid being investigated, there are produced around the submerged flow pattern 16 circular whirls 19 (shown by the arrows).-These whirls 19 are produced by the forces of friction (viscosity) caused by the interaction between the flow pattern 16 and the fluid in the volume 18. Between the volume 18 and the flow 16 there is an exchange of fluid that mainly occurs in the portion of the receiving channel 4 remote from the nozzle 3 and close to the place where the divergent flow pattern 16 reaches the wall of the receiving channel 4.The volume 18 is limited; this factor and the above-mentioned exchange of fluid account for a rapid removal of bubbles from the volume 18.

At the point where the light beam emitted by the lighting means 7 intersects the flow pattern 16, the diameter of this light beam must be somewhat greater than that of the flow pattern 16 to prevent the passage of particles outside the lighted zone. Suspended particles of impurities contained in the fluid being investigated travel across the zone illuminated by the light beam whose focus is in immediate proximity to the outlet of the nozzle 3. As foreign particles do so, they produce pulses of reflected light.Some part of the light energy reflected by particles determined by the solid angle formed by the tapered shape of the nozzle 3, is transmitted through the window 17, the lenses 13 and the diaphragm 14to the cathode of the photoelectron multiplier tube which produces a corresponding current pulse to be applied to a secondary instrument, such as an indicator (not shown).

Selecting the ratio between the diameters of the nozzle 3 and the receiving channel 4 in the range of 1/4to 1/7 makes it possible to perform granulometric analysis without providing a liquid envelope. This factor, in turn, accounts for a simpler design of the device and-an increased rate of investigation. The foregoing ratio is selected for a number of reasons as follows: A decrease in the diameter D of the receiving channel 4, while the diameterdofthe nozzle 3 remains unchanged, produces the following effects: a) an increase in the sensitivity of the device due to a smaller thickness of the layer of fluid exposed to light; and, b) better conditions for the removal of bubbles, due to a decrease in the volume 18.

On the other hand, due to a decrease in the diameter D of the receiving channel 4, the transparent windows 5 and 6 are brought closer together, as well as closer to the nozzle 3 and the light-sensitive means 8. As a result, the light scattered by the surface of the windows 5 and 6 may raise the level of noise currents and thus effect the sensitivity of the device. The above-mentioned ratio between the diameters d and D of the nozzle 3 and the receiving channel 4, respectively, has been established experimentally as giving the best results by minimizing the disadvantages and optimising the advantages mentioned above.

The fact that the channels 2 and 4 and the internal surfaces of the nozzle 3 are inclined downward in the downstream direction is conducive to a faster removal of particles precipitated from the fluid being investigated. This prevents contamination of the channels 2 and 4 which otherwise may affect the accuracy of analysis. As long as the window 17 is above the flow of fluid as is the case in Figure 1, a precipitation of particles on the surface of the window 17 and a consequential loss of sensitivity is avoided.

Precipitation of particles largely occurs when the pumping is discontinued. It is necessary to stop the pumping at regular intervals when investigating individual samples of fluids or a flow of fluid containing bubbles, for example, air bubbles. If this be the case, an analysis must be preceded by a removal of bubbles from the sample, because otherwise the bubbles may be sensed as particles.

The embodiment of Figure 2 is preferable for investigating continuousiy pumped fluids without bubbles. The embodiment of Figure 2 operates as that of Figure 1. The former differs from the latter by a faster removal of the air contained in the channels 2 and 4 and the nozzle 3 prior to the arrival of the fluid to be investigated. This is due to the fact that the vector of the buoyancy force essentially coincides with the direction of the flow.

Claims

1. A device for granulometric analysis of particles contained in fluids, comprising a feeding channel which communicates through a nozzle with a receiving channel provided with transparent windows to expose the fluid flowing through the channels to a light flux emitted buy a lighting means whose optical axis extends at an angle to the axis of the nozzle, and a light-sensitive means for receiving through a separate window light reflected from particles contained in the fluid being investigated, which light-sensitive means is arranged so that its optical axis passes through the point of intersection of the axis of the nozzle and the optical axis of the lighting means, the ratio between the diameters of the nozzle and the receiving channel being in the range of 1/4to 1/7.

2. A device as claimed in claim 1,wherein the feeding and receiving channels extend perpendicularto each other, the optical axis of the lightsensitive means is coincident with the axis of the nozzle, and the window, which is transparent to reflected light, is provided in a wall of the feeding channel, opposite the nozzle outlet.

3. A device as claimed in claim 2, wherein the feeding and receiving channels and the internal surface of the nozzle are inclined downward in the fluid flow direction.

4. A device as claimed in claim 2, wherein the receiving channel is vertical, its inlet being at a lower level than its outlet.

5. A device for granulometric analysis of particles contained in fluids, as claimed in any one of the preceding claims and substantially as hereinbefore described with reference to either of the embodiments shown in the accompanying drawings.