FR2792723A1 - LIGHT TURBINE FOR FLOW METER - Google Patents

Abstract

The turbine comprises a hollow body intended to be traversed by a stream of fluid, a rotor provided with at least one blade (3) adapted to rotate freely in the body at a speed proportional to the flow rate of the stream of fluid, and at least one detector means adapted to create at least one electrical signal which is a function of the value of a physical quantity characteristic of the rotation of the rotor. The rotor comprises a hub (1) having only a cavity (2) limited by the outer wall of the hub and sealed so that the hub floats in the liquid stream. The turbine can be used in flowmeters in a wide range of flow rates, for example to measure the flow of liquid hydrocarbons.

Description

The present invention relates to turbines for turbine flowmeters

  used to measure the flow or amount of fluid, for example from

liquid, which passes through them.

  The invention is intended to improve the accuracy and reliability of turbine flowmeters of the "axial" type as well as of the "tangential" type. A first type of turbine flow meter is known comprising an element provided with blades, of any shape, which is free to rotate and is set in motion by the action of the fluid to be measured on the blades. This rotating element is held in a turbine body by bearings and stops, possibly combined, so that its axis of rotation is

  parallel to the flow of the fluid.

  A second type is known which differs from the first in that the axis of rotation of the rotary element is perpendicular or inclined with respect to

fluid flow.

  These widely used flowmeters are precise, simple, light, compact and inexpensive. However, their precision, the reproducibility of the measurements, and their reliability are largely dependent on the quality of the pivotal members for the rotating element, called in the

"swivel members" technique.

  It is known that the metrological characteristics of turbines depend, to a certain extent, on the friction forces exerted at the bearings. These friction forces are due to the radial and axial loads applied by the rotating element, called rotor in the rest of the text. These loads originate from the weight of the rotor as well as the hydrodynamic forces it undergoes. These efforts are, by way of nonlimiting examples, the results of the viscosity of the fluid and the profile drag forces; compensation for hydrodynamic effects has long been

  the subject of numerous patents, and will not be discussed here.

  The invention aims to remedy these drawbacks, and thus the reduction or even the elimination of the loads due to the weight of the rotor, and the improvement of the reliability of the axial stops; it preferably concerns,

  but not exclusively, medium and large turbines.

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  In the French patent N 80 12 264 which relates to the lightening of turbines, the request for protection relates to the realization of entirely hollow axial turbine propellers; is also mentioned in this patent, the production of plastic propellers loaded with hollow microbeads. These solutions can be adapted to very small turbines preferably built in large series or not subject to economic constraints. However, they cannot be suitable for larger devices for several reasons, and in particular for both

following reasons.

  On the one hand, the use of plastic loaded with hollow microbeads is not suitable for all types of fluid. In fact, plastics have a power of absorption of liquids, which generally does not allow the very precise conservation of the shapes of the blades therefore of the precision of the turbine, and in addition they do not have a sufficient physico-chemical resistance. for measuring fluids at high temperatures

  or for the measurement of chemically aggressive liquids.

  On the other hand, the manufacture of fully hollow thin wall rotors is, for economic and technical reasons, applicable neither to medium or large turbines built in small series nor to the relatively high pressures often encountered in industries.

  petroleum and petrochemical, for example.

  The invention therefore aims to remedy the drawbacks mentioned above as well as those of these known lightened turbines, and relates to this end a turbine comprising a hollow body intended to be traversed by a stream of fluid, a rotor provided with '' at least one blade adapted to rotate freely in the body at a speed proportional to the flow of the fluid current, and at least one detector means adapted to create at least one electrical signal which is a function of the value of a physical quantity characteristic of the rotation of the rotor, turbine characterized in that the rotor comprises a hub which alone has a cavity limited by the outer wall of the hub and closed in leaktight manner so that the hub

  float form in the liquid stream.

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  Thanks to these characteristics, the friction due to the weight of the rotor exerted on the pivoting members of the latter is considerably or even totally reduced, as a result of the reduction or even cancellation of the apparent weight of the rotor. that is to say the weight reduced by the Archimedes thrust exerted by the measured fluid. The invention also makes it possible to thus improve the accuracy of the measurement, mainly at low flow rates, and the fidelity and reliability of the turbines as a result of the reduction in the value of the product P x V of the load of the pivoting by its speed, The wear of the pivoting being strongly dependent on this product P x V. According to the type of turbine concerned and according to the mounting position, the improvement is felt by the reduction of the friction on the pivoting members of the rotor such as bearings , stops or combinations thereof. The invention as defined above is applicable to all

pivot types.

  The turbine can also, according to the embodiments, have one or more of the following characteristics: - comprise at least one blade whose thickness decreases, with possibly discontinuities in its decrease, from the periphery of the blade to the root of it; include, to close the cavity, at least one rotor support in which the rotor is supported by a shaft and o is housed at least one axial stop for the shaft; - Include, to close the cavity, a rotor support in one piece with the hub, where is housed at least one axial stop; - Include two axial stops in opposite end regions of the hub; - Include bearings maintained in a bearing carrier mounted to rotate relative to a fixed shaft which passes through the rotor along its longitudinal axis, held in the body of the turbine at at least one of its ends;

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  - Include a shaft or at least a half-shaft maintained on the one hand in the rotor and rotating on the other hand in a fixed bearing maintained in the body of the turbine; - Include bearings held in shutters forming rotor supports, at least one of which may be integral with the hub; - Include half-shafts held in shutters forming rotor supports, at least one of which may be integral with the hub; have at least one blade extending approximately helically; - Have blades extending in planes, or profiles, inclined relative to the direction of the axial flow of the fluid; - Include blades extending in planes parallel to the axis of rotation of the rotor, itself inclined or perpendicular to the flow of the fluid; have a hub made of a low density material such as a carbon-based material, for example in the form of graphite; - Include cooling means constituted by channels extending in at least one rotor support or in a warhead

  attached around a rotor support, where an axial stop is housed.

  Other characteristics and advantages of the invention will emerge

  of the description which follows, of embodiments of the invention

  given by way of nonlimiting examples, illustrated by the accompanying drawings in which: - Figure 1 shows a first embodiment of a turbine rotor according to the invention, - Figure 2 shows a second embodiment of a turbine rotor according to the invention, - Figure 3 shows a third embodiment of a turbine rotor according to the invention, - Figure 4 is a diagram showing the percentage of error as a function of the flow rate for a turbine conventional and a light turbine according to the invention, and

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  FIG. 5 is a diagram showing the percentage of error as a function of the flow rate in another range of flow rates also for a

  lightened turbine according to the invention.

  The turbine rotor represented in FIG. 1 is intended for an axial type turbine flow meter, this turbine comprising a hollow body intended to be traversed by the current of fluid to be measured and in which is housed the rotor which is adapted to rotate therein freely at a speed proportional to the flow of the fluid stream; the turbine also comprises at least one detector means associated with the rotor to create at least one electrical signal which is a function of the value of a physical quantity characteristic of the movement of at least one blade of the rotor or more

  generally from the rotation of the rotor.

  This rotor is produced in the form of a propeller comprising a hub 1 having internally a cavity 2 limited by the external wall of the hub thus forming a float in the stream of liquid, and externally, over most of its length, a section of generally cylindrical shape, the periphery of which is provided with one or more blades 3 here helical, and here coaxially an upstream end region also of generally cylindrical shape of smaller diameter connected to the first

2 0 section by a shoulder.

  The blades 3 have a thickness which here decreases regularly between their periphery and their root where they originate on the hub 1; however, the blades 3 may possibly have one or

  several discontinuities in the decrease of their thickness.

  Here, the small diameter end region of the hub 1 is housed in a housing of a warhead 4, and its opposite end region is sealed by a plug 5 having however a central through bore, to form bearing holder support as will be more precisely explained below; alternatively, the cavity could be closed by the fact that the hub would have in one piece a narrowed portion itself forming a bearing carrier support; in the case of

  Figure 1, the upstream end region of small diameter of the hub 1 forms itself

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  same bearing holder 5, although not closed, as is

will see later.

  Inside the small diameter end region of the hub 1 and of the central bore of the shutter 5, are fitted the ends of a tubular sealing bearing holder 6 adapted to rotate with the hub 1 and entirely housed therein, passing right through the hub, from this upstream end region to the bore of the shutter; externally, the end regions of this bearing holder 6 housed respectively in the end region of the hub 1 and in the bore of the shutter 5 have a diameter slightly greater than that of its central section; it is the same internally, in the through bore of the bearing holder 6. In this through bore, in the two end regions of larger inside diameter of the bearing holder 6, are housed respective bearings 7 in the form rings, constituting the pivoting members of the rotor; these bearings 7 are in abutment against shoulders connecting the end regions of the bore of larger internal diameter to the central region of the latter of smaller internal diameter. The central hole passing through the bearings 7 is

  centered in the bearing 6, on the axis of the hub 1.

  Inside the bearings 7 arranged in the end regions of the bearing carrier 6, the fixed central shaft 8 of the rotor is adjusted, which passes through and maintains the latter extending along the longitudinal axis of the hub I; this shaft 8 has a generally cylindrical section over most of its length, extended beyond the upstream bearing by a first cylindrical end region of larger diameter, ending frustoconically almost at a point at its free end; this end region is connected to the very long section by a shoulder facing the upstream face of the upstream bearing, and is housed in the upstream end region of the bearing carrier 6 itself housed in the upstream end region of the hub 1, inside the warhead 4. The upstream end of the bearing holder 6 o is housed the large diameter region of the shaft 8 is closed by an axial stop 9 for the tree, against which the free end

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  frustoconical of the shaft 8 is in support; the axial stop 9 is itself in

  support against the bottom of the upstream end region of the hub 1.

  According to an advantageous characteristic of the invention, the upstream end of the hub 1, on the other hand, does not bear against the bottom of its housing provided in the warhead 4, and has an opening, while the warhead has channels 10 connecting this housing and the exterior of the warhead; these channels 10 allow the fluid to be measured surrounding the rotor to reach the

  axial stop 9, and constitute means for cooling the stop.

  In the case of Figure 1, the rotor is mounted in overhang.

  1 0 In certain embodiments, the rotor may have rotor bearing supports containing a stop and also comprising

  cooling channels of this stop.

  By means of the channels 10 of the warhead or other end support (s), a circulation of fluid is created sweeping the face of the stop.

  axial which is not in direct contact with a shaft or half end

  shaft, ensuring the cooling of the stop. Thanks to the fact that the rise in temperature of the active surfaces of the axial stops is avoided, the decrease in the mechanical characteristics of the materials is limited, and thus the reliability of the pivoting is increased. This limitation of the temperature also acts on the increase of the friction coefficient of the stop, therefore reduces the corresponding friction forces and improves the accuracy of the measurement. While FIG. 1 shows an embodiment in which the shaft 8 of the rotor is held in the body of the turbine by only one of its ends and therefore extends in overhang, FIGS. 2 and 3 show alternative embodiments of a helical rotor in which the turbine comprises two end half-shafts. The elements shown in these Figures 2 and 3 and corresponding to elements of Figure 1 have the same numerical references. The elements of

  these figures which differ from the corresponding elements of FIG. 1.

  In the embodiment of FIG. 2, the hub 1 forming a float does not have an upstream end region of smaller diameter

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  and is not crossed right through by a bearing holder. On the other hand, the cavity 2 opens out through the two end regions of the hub 1 which are

  therefore each closed by a shutter 5 itself forming both a holder

  bearing and rotor support, having a central bore; however, this central bore for the rotor support is not through and has a bottom on the side of the cavity 2. Against this bottom, an axial stop 9 is arranged; the bores of the shutter 5 have two parts of different diameters, connected by a shoulder, the part of larger diameter being located on the side close to the outside of the hub 1. The bearings 7 in the form of rings in which are intended to be inserted the respective half-shafts are maintained in these parts of larger diameter, abutting against these shoulders. As we have seen, the axial stops 9 for the half-shafts can be cooled by a circulation of fluid if the shutters 5

  rotor supports have channels.

  In the embodiment of Figure 3, the hub 1 also does not have an upstream end region of smaller diameter and is not traversed right through by a bearing holder. The cavity 2 opens through the two end regions of the hub 1 which are therefore each closed by a shutter 5 having a central bore; this central bore is not through and has a bottom on the side of the cavity 2. It is directly in the central bore of the shutters 5 that are intended to be inserted and

  maintained the two respective half-shafts 81.

  Thus, in general, in all the embodiments, the hub 1, which, alone, is hollow, is produced so as to constitute a float subjected to the Archimedes thrust in the liquid to be measured. To this end, this hollow hub is sealed, and its walls are as thin as possible, taking into account the method of manufacture and the conditions of use.

rotor.

  Also with a view to reducing the apparent mass of the rotor, the thickness of the blades, which themselves are not hollow, is reduced to its minimum, a preferential but non-limiting means consisting in manufacturing the

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  blades so that their thickness, normal to the periphery of the rotor,

  decreases, gradually or not, towards the hub.

  Always for the same reason, the rotor is made of a material whose density is the lowest possible while having resistances, mechanical and chemical, adapted to the use of the turbine. By way of example, to measure hydrocarbon flow rates and in particular of G.P.L., the rotors can be made from carbon by

example in the form of graphite.

  l0 It should be noted that the embodiments shown are not limiting, and in particular the blades can extend along planes, or profiles, inclined relative to the direction of the axial flow of the fluid, or even parallel planes. to the axis of rotation of the rotor, itself

  inclined or perpendicular to the flow of the fluid.

  The rotor according to the invention can make use of all types of pivoting, whether with plain bearings and / or stops, as in the case of the drawings, or with bearings and / or bearings with balls or needles, or bearings and / or stops with liquid film, with points and cuvettes, or with spheres, or that they comprise any combinations of these elements or elements

equivalent.

  Also, the invention can be applied to other types of

  turbines and in particular tangential turbines.

  In the case of the rotor shown in FIG. 1, a light alloy propeller was produced whose mass without float is 79 grams. Her

  apparent mass in diesel is 56 grams.

  This propeller fitted with the only hub float but without lightening the blades or thinning the walls weighs 42 grams and its

  apparent mass in diesel is 24 grams.

  It will be noted that the complete application of the teachings of the invention brings an additional gain by reducing the wall thicknesses in accordance with the representation of FIG. 1. In the above example, the reduction in the thickness of the blades, this thickness varying from 2 i2792723 mm at the periphery to 1 mm at the root, leads to an apparent mass of

6.3 grams.

  This apparent mass which is almost nine times lower than

  that of the original propeller highlights the advantage of the invention.

  The curves in FIG. 4 represent experimental results obtained on two comparable propellers, one of normal construction (curve in broken lines), the other geometrically identical to the

  first but whose float-shaped hub as described in the figure

  1, without optimizing the thicknesses of the walls and without reducing the thickness of the blades, that is to say with a relatively reduced reduction

(curve in solid line).

  The graph is limited to low and very low flow rates for better

  highlight the improvement in precision provided by the invention.

  The normal operating range for this type of turbine is between 8 and 80 m3 per hour. The differences of the maximum and minimum errors of the normal propeller and the lightened propeller in this range of flows are equal to 0.88% and 0.7%. The error at the minimum flow rate of the operating range (8m3 / h) is reduced from -0.44% to -0.26%, which is considerable. The invention here provides a 20% reduction in turbine errors. This decrease is even greater by applying

  all the provisions of the invention.

  The curve of FIG. 5 is an error curve recorded by way of example on a propeller whose hub is a float according to the object of the invention, but whose wall thicknesses are reduced to increase the relief without reach the minimum possible weight, however, for

  flow values up to 100 m3 per hour.

  It will be noted that the implementation of the invention then makes it possible to maintain the errors of the turbine in the range -0.15% and + 0.15%, values which are particularly low and which can still be improved by appropriate optimizations.

12. 12792723

Claims (14)

  1. Turbine comprising a hollow body intended to be traversed by a stream of fluid, a rotor provided with at least one blade (3) adapted to rotate freely in the body at a speed proportional to the flow rate of the stream of fluid, and at least a detector means adapted to create at least one electrical signal which is a function of the value of a physical quantity characteristic of the rotation of the rotor, turbine characterized in that the rotor comprises a hub (1) having only a limited cavity (2) by i0 the outer wall of the hub and closed tightly so that the   hub forms a float in the liquid stream.   2. Turbine according to claim 1, characterized in that it comprises at least one blade (3) whose thickness decreases, with possibly discontinuities in its decrease, from the periphery of   the blade at the root of the latter.   3. Turbine according to any one of claims 1 and 2,   characterized in that it comprises, to close the cavity (2), at least one rotor support (5) in which the rotor is supported by a shaft (8) and o   is housed at least one axial stop (9) for the shaft.   4. Turbine according to any one of claims I to 3,   characterized in that it comprises, to close the cavity (2), a rotor support (5) in one piece with the hub (1), where at least one is housed axial stop (9).   5. Turbine according to any one of claims 1 to 4,   characterized in that it comprises two axial stops (9) in   opposite end regions of the hub (1).   6. Turbine according to any one of claims 1 to 5,   characterized in that it comprises bearings (7) held in a holder   bearings (6) mounted rotating relative to a fixed shaft (8) which crosses the rotor along its longitudinal axis, kept in the body of the turbine at least one of its ends. 12 2792723   7. Turbine according to any one of claims I to 5,   characterized in that it comprises a shaft (8) or at least a half-shaft (81) held on the one hand in the rotor and rotating on the other hand in a bearing   fixed held in the turbine body.   8. Turbine according to any one of claims 1 to 7,   characterized in that it comprises bearings (7) held in shutters (5) forming rotor supports, at least one of which can be integral with the hub (1).   9. Turbine according to any one of claims 1 to 7,   characterized in that it comprises half-shafts (81) held in shutters (5) forming rotor supports, at least one of which can be integral with the hub (1).   10. Turbine according to any one of claims 1 to 9,   characterized in that it comprises at least one blade (3) extending   approximately helically.   11. Turbine according to any one of claims 1 to 9,   characterized in that it comprises blades (3) extending along planes, or profiles, inclined relative to the direction of the axial flow fluid.   12. Turbine according to any one of claims 1 to 9,   characterized in that it comprises blades (3) extending along planes parallel to the axis of rotation of the rotor, itself inclined or perpendicular to fluid flow.   13. Turbine according to any one of claims 1 to 12,   characterized in that the hub (1) is made of a low density material such as a carbon-based material for example in the form graphite.   14. Turbine according to any one of claims 3 and 4,   characterized in that it comprises cooling means (10) constituted by channels extending in at least one support (5) of the rotor or in a warhead (4) attached around a support (5) of the rotor, where is housed an axial stop (9).