WO1994015179A1

WO1994015179A1 - Fluid flow rate measuring apparatus

Info

Publication number: WO1994015179A1
Application number: PCT/CA1993/000516
Authority: WO
Inventors: Jaromir Friedrich; Bruno H. Walter
Original assignee: Jaromir Friedrich; Walter Bruno H
Priority date: 1992-12-18
Filing date: 1993-12-10
Publication date: 1994-07-07
Also published as: CA2085805A1; AU5557794A

Abstract

A liquid flow measuring device has a deflector (31, 69) slidably mounted relative to a cylindric inlet of the liquid to be measured, for a minute displacement along the axis of the inlet conduit. The deflector is exposed to the static pressure created by the fluid. It has a concavely shaped deflection face shaped to reverse the flow of the incoming liquid. The flowing liquid creates a dynamic force vector at the deflector in the direction of the axis thereof. The dynamic force at which the deflector is urged by, and in the direction of, the incoming flow is sensed by an electric pressure cell (42, 81) whose electrical output is then directed to a suitable indicator (47) or control apparatus. The device presents a simple arrangement. Yet, it is sensible to even minor variations in the rate of flow of the liquid due to the fact that virtually the entire flow participates in the generating of the pressure active at deflector and thus at the cell (42, 81).

Description

FLUID FLOW RATE MEASURING APPARATUS

The invention relates to apparatus for measuring fluid flow, comprising a housing including an upstream end portion and a downstream end portion, a piston member slidably mounted in said housing, said piston member including an anterior end face disposed at said upstream end portion of the housing, and a posterior end part spaced axially downstream from the anterior end face, said housing defining fluid flow directing means which includes a tubular inlet portion and a tubular outlet portion, said tubular inlet portion being coaxial with and disposed just upstream of said anterior end face, to direct incoming fluid flow against an said anterior end face, said apparatus further comprising pressure transducing means fixedly secured to said piston member, for transmitting pressure active at the piston member and due to forces generated by fluid flow at the anterior end face of the piston member, to pressure receiving means. In a known type of flow rate measuring devices a flow deflecting member is placed in the path of the flow to be measured. A displacement of the flow sensing element takes place along the axis of the incoming flow. Such device is shown, for instance, in U.S. patent 3,691 ,834 (De Fasselle et al.) where the flow raises a floating piston and the displacement is indicated by a mechanical readout. The device does not allow a remote reading of the flow rate. U.S. patent 4,221 ,134 (Ekstrom Jr.) shows a combination of a diaphragm and a strain gauge. Viewed from the standpoint of the present invention, the device only reads pressure but not the flow rate which is measured by a separate device. The arrangement is complex. U.S. patent 4,361 ,051 (deFasselle et al.) is a variant of the device of U.S. patent 3,691 ,834. It does not allow a remote reading of flow rate values. U.S. patent 4,481 ,830 (Smith et al.) describes a flow measuring apparatus having a drag plate subjected to the flow of coolant of a nuclear reactor. A minute displacement of a drag plate is transmitted mechanically to a strain gauge mechanism comprised of plurality of strain gauges mounted on a flexible loop. The device presents not only a complex arrangement as far as the strain gauges are concerned but also requires a large number of moving parts placed in the path of the flow. U.S. patent 4,787,253 (De Fasselle et al.) presents a variant of the first mentioned U.S. patent 3,691 ,834. It is provided with electromagnetic means to enable remote readout of the rate of displacement of a flow measuring piston. The disadvantage is in that there are parts which require substantial displacement in order to achieve the reading of the differences in the flow. The device may be difficult to maintain. U.S. patent 4,788,869 (Li) shows a flow rate meter which comprises an elongated stem mounted in the wall of a pipe and projecting radially inwards. It has a spherical feeler at a free end. The variations in the flow velocity result in different bending stress at the stem which is sensed electronically and transformed to an electrically indicated value corresponding to the flow. The feeler is influenced by only a small part of the flow and therefore may fail to provide readout of relatively minor differences in the flow velocity which would impair, the accuracy of measurement. U.S. patent 4,947,691 presents another arrangement showing that it is known to use strain gauges to measure the speed of flow of a liquid. This device is specifically adapted for use in paper making machines and does not have a wide application due to its specific structure. U.S. patent 5,007,286 (Malcolm et al.) presents another arrangement structurally similar to and having the same drawback as the probe of U.S. patent number 4,788,869 discussed above. SUMMARY OF THE INVENTION It is an object of the present invention to provide further advance in the art of the flow meters of the kind referred to at the outset. In particular, the object is to simplify the structure and yet to secure that the device is sensible to minor variations in the flow rate measured.

In general terms, the present invention presents apparatus for measuring fluid flow rate in a pipe line, the apparatus comprising, in combination: an inlet conduit having a longitudinal axis, a flow deflector in a fluid communication with the a downstream end of said inlet conduit and freely movably mounted relative to said inlet conduit in the direction generally parallel with said axis, said deflector having a concavely configured flow deflecting surface section exposed to generally the entire flow from the inlet conduit, whereby generally the entire volume of flow of the respective fluid actuates the deflector; the flow deflecting surface being configured to reverse generally the entire volume of fluid from the inlet conduit; the flow deflector being operatively connected to a pressure cell adapted to produce electrical signal whose magnitude is commensurate with a dynamic force generated by the deflector on reversal of the fluid flow by the deflecting surface; and an outlet conduit for conducting the fluid away from the apparatus.

The invention will now be described in detail with reference to the accompanying drawings presenting a diagrammatic representation of the invention. In the drawings:

FIGURE 1 is a diagrammatic cross-sectional view of a first embodiment of the present invention;

FIGURE 2 is a cross-sectional view of the apparatus taken along the section line ll-ll of Figure 1 ;

FIGURE 3 is a cross-sectional view of the apparatus taken along the section line Ill-Ill of Figure 1 ;

FIGURE 4 is a front view of a second embodiment of the invention; and

FIGURE 5 is a side view of. the second embodiment.

Turning now to Figure 1 , a housing 1Q has an upstream end portion H and a downstream end portion 12. The embodiment as shown in Figure 1 is an arrangement having a generally vertical disposition where its longitudinal axis 13 is generally vertical. The upstream end portion 11 is the lower end of the device shown, while the downstream portion 12 is on top. The interior of the housing 10 comprises a lower, generally cylindric portion 14 which merges, at its upper end, with a conical section 15. The conical section 15 of the housing 10 is flanged at 16. A set of clamping bolts 17 secures the flange 16 to a flange 18 of a tubular outlet portion 19.

The lower or upstream end portion 11 of the housing 10 includes a reaction plate portion 20 having a flange 21 fixedly secured by bolts 22 to a flange 23 of the housing 10 disposed at the lowermost end of the cylindric portion 14 thereof.

The reaction plate portion 20 defines, in the embodiment shown, an annular projection 25 which has a convexly curved cross-section. The annular projection 25 forms the downstream extreme of a tubular inlet portion 24. The radially outwardly adjacent part of the reaction plate portion 20 is formed by an outer annular groove 26. In cross-section, the annular groove 26 is concavely curved and presents a smooth merger with an adjoining inner cylindric wall 27 at a radially outer portion 23 of the reaction plate 20.

Disposed within the housing 10 is a cylindric chamber 29 fixedly secured to the housing 10 by struts 30. Slidably received within the cylindric chamber 29 is a piston member 3 , and in particular its cylindric lower portion 32 which, like the inside wall of the cylindric chamber 29, is provided with a TEFLON™ coating for a smooth, free sliding of the piston member 31 within the cylindric chamber 29. The struts 30 maintain a spacing between the outer cylindric surface of the cylindric chamber 29 and the inner cylindric wall 27 of the housing 10 to define a generally annular flow channel 33- The channel 33 has a predetermined cross-sectional area which, preferably, corresponds to the cross-sectional area of the tubular inlet portion 24.

The upper part of the piston member 31 extends beyond the upper or downstream end of the cylindric chamber 29 and is conical at 3_4_. It combines with an inside conical wall 35 of the housing 10 to define therewith a conically annular flow passage 36. It can be seen that the passage 36 differs from the annular flow channel 33 in that the channel 34 runs between two portions fixedly secured to each other, i.e. the cylindric chamber 29 and the housing 10, while it is the piston member 31 , in particular its conical portion 34, which forms the inner surface of the annular flow passage 36. Accordingly, the piston member 31 is exposed to the flow of liquid in the annular flow passage 36. The cross-section of the annular flow passage 36 gradually increases in the direction towards the top or downstream end of the apparatus, to maintain the cross-sectional area in general correspondence with that of the annular flow channel 36 to secure a uniform speed of flow along the conical part 34 of the piston member 31. The exposure of the downstream conical portion 34 of the piston member 31 to the flow of the liquid provides for general balance of static pressure generated by the liquid at the piston 31 so that only dynamic force active at the upstream face of the piston 31 determines the pressure used in measuring the speed of flow, as will be explained.

The apex portion 37 of the conical part 34 of the piston member 31 is provided with a guide pin 38 having a rounded tip portion 39. The pin 38 is slidably received in a sleeve assembly 40 secured to the tubular outlet portion 19 by means of four struts 41. Accordingly, the piston 31 is freely slidable within the housing for a minute displacement along the axis 13. The rounded tip portion 39 abuts against a pressure cell 42 fixedly secured, for instance by screws (not shown), to an upstream face of a conical support 43 coaxial with the axis 13 and held in place by series of struts 44, much in the fashion of the struts 41 of the sleeve assembly 40. The apex portion of the conical support 43, which support is co-axial with the axis 13, is directed downstream into the cylindric part 45 of the tubular outlet portion 19.

Reference numeral 46 designates a diagrammatic representation of electric leads connecting the pressure cell 42 with a remote monitoring device, e.g. a flow indicator. The connection by the leads 46 and the indicator 47 itself are of a well known design and therefore do not have to be described in greater detail. A great variety of load cells suitable for this purpose is available having different load ranges and physical dimensions. They are manufactured, for instance, by ENTRAN Devices Inc., Strainsert Company, Stress-Tek Inc. and by many other manufactures.

Reference should now be had to the lower end face of the piston member 31 and the adjacent lower end portion 4fi of the cylindric chamber 29. These end portions may also be referred to, in general terms, as anterior or upstream end face 49 of the piston 31 or anterior end 48 of the cylindric chamber 29.

Turning firstly to the shape of the anterior end of the piston member 31 , the end face 49 is provided with a circular or annular groove 50. As shown in Figure 1 , the groove 50 has a concavely rounded cross-section. In the embodiment shown, it extends over the entire area of the downwardly facing anterior end of the piston member 31. The groove is disposed about a centrally located tip 5J_. In the cross-section, the groove comprises an arcuate bottom wall section 5_2, an arcuate outer side wall section £3 and an arcuate inner side wall section 54, all sections 52, 53 and 54 smoothly merging with each other to provide the generally semi-circular concave configuration as shown. It is important to note that the annular projection 25 is so arranged that the cylindric surface of coincidence with the tubular inner portion 24 coincides approximately with the bottom wall section 52 and does not reach radially outwardly beyond same. The groove 50 is so shaped that, apart from diverting the flow radially outwardly it reverses the flow by almost 180° to generate a dynamic force vector at the anterior face of the piston member 31. It is noteworthy that the flow reversing, radially outward portion of the groove 50 coincides with the rounded lower end portion 48 of the cylindric chamber 29, the convexly rounded cross-section of the end portion 48 being complementary with and disposed at a spacing from the concavely rounded cross-section of the annular groove 26.

With the arrangement described, the housing 10 defines a fluid flow directing means which is comprised of the already mentioned tubular inlet portion is adapted to direct incoming fluid flow against the upstream end face 49 of the piston member 31. The fluid flow directing means further comprises the arrangement of a generally S-shaped part (in cross-section) at each side of the housing, then the annular flow channel 34 outside of the cylindric chamber 29, the conically annular passage 36 and, eventually, the cylindric tubular outlet portion 19.

In operation, there is a virtually negligible spacing between the tip portion 39 of the pin 38 and the pressure cell 42. The liquid the rate of flow of which is to be measured flows in the direction from bottom to the top of Figure 1 , first encountering the tip 51 of the groove 50 to be directed radially outwardly and reversed through the tortuous path of the reaction plate portion 20 and the correspondingly shaped bottom of the piston 31. At this stage, the fluid flow develops a pressure vector directed in the upward direction and urging the piston 31 and thus the tip 39 against the pressure cell 42. There is virtually no displacement (only a few thousands of an inch) of the piston 31 relative to the housing 10. The pressure at which the tip 39 presses against cell 42 is monitored at the indicator 47. It is proportional to the flow rate of the incoming liquid. Since the cross-sectional area of the annular channels or passages 33, 36 is so designed as to maintain a uniform rate of flow, there is a minimal distortion, if any, at the conical part 33 of the piston member 29. By the same token, the liquid pressure is active at the conical part 34 of the piston 31 to compensate for the hydraulic pressure element active at the upstream face of the piston 31. Accordingly, the force generated at the cell 42 is due generally solely to dynamic forces generated by the reversal of flow of the liquid. Referring now to the representations of Figures 3 and 4 reference numeral 60 designates a solid frame provided with a pair of annular yokes such as yoke 61 at the upper end 62 of the frame 60. The yokes are in engagement with an outer surface of a pair of pipes, an inlet pipe 63 and an outlet pipe 6_4- The pipes 63 and 64 are each provided with a respective flange 65 and 66, at the inlet and outlet portions of the apparatus, respectively. The axes 67, 68 of the pipes 63, 64 are generally parallel.

A U-shaped tubular deflector 69 has an upstream end portion 7_) and a downstream end portion 7J.. The end portions 70 and 71 are telescopically and sealingly received in an end sleeve 72 of the inlet pipe 63 and in an end sleeve 73 of the outlet pipe 64. It is to be noted that the sealing connection which allows for free telescopic movement of the U-shaped deflector 69 relative to the pipes 63, 64 can be made in a number of various designs all of which are well known in the art of hydraulic devices and which may include, for instance, a flexible sleeve (not shown) secured with an end to the respective pipe 63, 64 and with the other to the respective end of the deflector 69.

It is noteworthy that the cross-sectional area of the U-shaped deflector is the same as that of the inlet and outlet pipes 63 and 64. The pipes 63 and 64, in turn correspond in cross-section to the pipeline in which the apparatus is being used. In other words, the entire flow of the pipeline to be measured is directed through the deflector 69 and participates in the operation of the apparatus as will be described.

The lower end portion of the U-shaped member is provided with a stem 74 passing through a hydraulic, cylindric chamber 75. An annular piston 76 is slidably received within the chamber 75. The chamber 75 is fixedly secured to the frame 60 by way of struts 77, 78 at the respective ends of the chamber. The chamber 75 communicates via a connection line 79 with the interior of the inlet pipe 63. The lower tip 80 of the stem 74 is in abutment with a pressure ceil assembly 8_1 held in place by a support _\2 fixedly secured to the lower struts 78, as best shown in Figure 3. Electric line 83 communicates the pressure cell assembly 81 with an indicator or controlling device (not shown) in the same fashion as described in connection with the indicator 47 of the first embodiment. ln summary, therefore, the entire assembly shown in Figures 4 and 3 is rigid with the exception of the telescopically mounted deflector 69 and the stem 74 with the piston.

In operation, the chamber 75 is filled with the liquid normally coming through the inlet pipe 63. The venting arrangements or the like required for this purpose are not shown for simplicity. As a consequence, the pressure acting on piston 76 is the same as that of the liquid coming into the apparatus through inlet pipe 63 (or active at the outlet pipe 64) . The entire volume of the fluid flow to be measured is directed into the deflector 69 and reversed to flow away into the outlet pipe 64. Since the pressure in chamber 75 maintains the telescopically arranged deflector 69 in balance with respect to the pressure prevailing in the pipeline, it is solely the dynamic force generated by the reversal of the full volume of the liquid flowing through the apparatus which is active at the tip 80 and presses against the pressure cell assembly 81 to indicate an electric value commensurate with the instant dynamic force acting at the deflector 69. It will be appreciated, of course, that the connection of the connecting line 79 could also be made to the discharged pipe 64.

It can thus be seen that the invention presents an extremely simple arrangement which, due to the exposure of the deflecting surface of the deflector, whether the piston member 31 or the U-shaped deflector 69, to the entire flow of the liquid, has an improved accuracy of measurement. By the same token, the structure of the apparatus is extremely simple and thus relatively inexpensive to produce and maintain.

Those skilled in the art will readily appreciate that modifications may exist of the present invention. For instance, the arrangement of the flow along the piston member 31 could be modified to provide an arrangement where the intermediate cylindric chamber 29 would be eliminated and the piston member 29 allowed to slide within the housing, utilizing, as an example, a series of radial ribs maintaining the spacing between the piston member and the housing 10, to provide the requisite annular flow passage. Many other embodiments may exist differing, to a greater or lesser degree, from the embodiment described, but still falling within the scope of the present invention. Accordingly, we wish to protect the Letters Patent which may issue on the present application all such embodiments as properly fall within the scope of our contribution to the art.

Claims

1. Apparatus for measuring fluid flow, comprising a housing (10) including an upstream end portion (1 1 ) and a downstream end portion (19), a piston member (31 ) slidably mounted in said housing (10), said piston member (31 ) including an anterior end face (49) disposed at said upstream end portion (19) of the housing (10), and a posterior end part (34) spaced axially downstream from the anterior end face (49), said housing (10) defining fluid flow directing means which includes a tubular inlet portion (24) and a tubular outlet portion (19), said tubular inlet portion (24) being coaxial with and disposed just upstream of said anterior end face (49), to direct incoming fluid flow against an said anterior end face (49), said apparatus further comprising pressure transducing means (38, 39) fixedly secured to said piston member (31 ), for transmitting pressure active at the piston member (31 ) and due to forces generated by fluid flow at the anterior end face (49) of the piston member (31 ), to pressure receiving means (42) characterized in that (a) said piston is adapted for a minute displacement relative to the housing (10) generally in the direction of a longitudinal axis of the housing;

(b) the anterior end face (48) of the piston member (31 ) is provided with a generally annular groove (50) open in an axially upstream direction, having a concavely rounded cross-section (52, 53, 54) and extending over virtually the entire area of said end face (49), said annular groove (50) having an inner side wall section (54), a bottom section (52) and an outer side wall section (53), each said wall section being of an arcuate cross-section complementary with the respective portion of the annular groove (50);

(c) said fluid flow directing means further includes:

(1 ) a reaction plate portion (20) including an annular projection (25) of a convexly curved cross-section, disposed at a downstream end of the tubular inlet portion (24) and facing said outer side wall section (53) of the annular groove (50), and a concavely curved annular section (26) adjoining the annular projection (25) at a radially outer portion of the reaction plate portion (28); (2) an annular flow portion (33) having an upstream end thereof adjoin a radially outermost part of said concavely curved annular section (26) of the reaction plate portion (28), said annular flow portion (33) extending along a cylindric section upstream end of the piston member (31 );

(3) a conically annular passage (36) adjoining the annular flow portion (33) and gradually decreasing in diameter in downstream direction while increasing in cross-sectional area to maintain the cross- sectional area generally equal to that of said annular flow portion (33); and

(d) said tubular outlet portion (19) is coaxial with and disposed downstream of the posterior end part (37) of the piston member (31 );

(e) said pressure receiving means (43, 44) being rigidly mounted with respect to said housing (10) and being compatible with the pressure transducing means (38, 39) to activate a pressure cell (42) adapted to produce electrical signal output the magnitude of which is commensurate with instant pressure active at said pressure transducing means (39-40).

2. Apparatus as claimed in claim 1 , characterized in that said piston member (31 ) is slidably movable within a cylindric chamber (29) fixedly secured to the housing ( 10) at the inside thereof, said annular flow portion (33) being a generally annular space between an outside cylindric surface of the cylindric chamber (29) and an inside wall (27) of the housing (10), the inside of said cylindric chamber (29) slidably receiving a cylindric section (32) of the piston member (31 ).

3. Apparatus as claimed in claim 2, characterized in that the conically annular passage (36) is defined by a conical upper part integral with the piston member (31 ) and disposed beyond said cylindric chamber (29), and by a correspondingly conical inside wall portion (35) of the housing (10).

4. Apparatus as claimed in claim 3, wherein the pressure transducing means (38, 39) and pressure receiving means (42) are coaxial with the piston member (31 ) and are disposed at the downstream end portion (12) of the housing (10).

5. Apparatus as claimed in claim 4, characterized in that the pressure transducing means includes a pin (38) coaxial with the piston member (31 ) and defining an extension of an apex portion (37) of said conical upper part (34) of the piston member (31 ), said pin (38) being slidably guided in centrally disposed guide sleeve (40) fixedly secured with respect to said housing (10) and coaxial with the axis (13) of the piston member (31 ).

6. Apparatus as claimed in claim 5, characterized in that the pressure receiving means is a pressure cell (40) fixedly secured to and disposed centrally of the housing (10) near the tubular outlet portion.

7. Apparatus as claimed in claim 6, characterized in that said pressure cell (40) is mounted on the pressure receiving means (44) coaxially with the pressure pin (38) generally in an abutment relationship therewith, whereby the pressure acting at the piston member (31 ) is directly transmitted to said pressure cell (42).

8. Apparatus as claimed in claim 1 , characterized in that the longitudinal axis (13) is generally vertical, the upstream end portion (20) of the housing (10) being a lower end portion thereof.

9. A liquid flow measuring apparatus comprising a longitudinal housing (10), a piston member (31 ) slidably mounted in said housing (10) and having an upstream face section (49) exposed to generally the entire cross-section of incoming flow to be measured, characterized in that the upstream face section (49) is concavely configured (52, 53, 54) for spreading the incoming flow radially outwardly, reversing same (26) and changing it to an annular flow directing means (29) adapted to direct the liquid alongside and past the piston (31 ) to an outlet of the apparatus, the piston (31 ) being operatively connected to a pressure cell (42) adapted to produce electrical signal whose magnitude is commensurate with instant pressure caused by the liquid flow at said piston member (31 ).

10. Apparatus for measuring fluid flow rate in a pipe line, characterized in that it comprises: an inlet conduit (63) having a longitudinal axis (67), an upstream end and a downstream end; a flow deflector (69) in a fluid communication with the a downstream end of said inlet conduit (63) and freely movably mounted relative to said inlet conduit in the direction generally parallel with said axis (67), said deflector (69) having a concavely configured flow deflecting surface section exposed to generally the entire flow from the inlet conduit (63), whereby generally the entire volume of flow of the respective fluid actuates the deflector (69); the flow deflector (69) being operatively connected to a pressure cell (81 ) adapted to produce electrical signal whose magnitude is commensurate with a dynamic force generated by the deflector (69) on reversal of the fluid flow by the deflecting surface; and an outlet conduit (64) for conducting the fluid away from the apparatus.

1 1. The apparatus of claim 10, characterized in that the outlet conduit (64) is a pipe section having an upstream end portion (73) and a downstream end portion (66), said flow deflector (69) being a U-shaped pipe section having an upstream end portion (70) and a downstream end portion (71 ), said upstream and downstream end portions of the U-shaped pipe section being in a sealed fluid communication with, and being freely axially movable relative to the inlet and outlet conduit (63, 64), respectively; the apparatus further includes a pressure compensation device (75) operatively connected (74) to the deflector (69) for urging same in the direction against the downstream end of the inlet conduit (63) by a force proportional to pressure of fluid passing through said apparatus.

12. The apparatus of claim 1 1 , characterized in that the pressure compensation device is a piston/cylinder device (76, 75); said piston/cylinder device (75, 76) having a piston end portion (74) mechanically connected to the flow deflector (69); and a cylinder end portion (75) hydraulically connected (79) to the inlet conduit (63).

13. The apparatus of claim 1 1 , characterized in that the pressure compensation device is a piston/cylinder device (75, 76); said piston/cylinder device (75, 76) having a piston end portion (74) mechanically connected to the flow deflector (69); and a cylinder end portion (75) hydraulically connected (79) to the outgoing flow conduit (64).

14. The apparatus of claim 1 1 , characterized in that the flow-through rate of the flow deflector (69) is the same as that of the inlet conduit (63), the flow-through rate of the latter (63) being generally equal to that of the flow rate in the respective pipe line.