MXPA00003734A - Fluid oscillator with extended slot - Google Patents

Abstract

The invention concerns a fluid oscillator symmetrical relative to a longitudinal symmetry plane (P), comprising, an opening (22) for the fluid to penetrate into a chamber (24) called oscillation chamber in the form of a two-dimensional fluid jet oscillating transversely relative to said symmetry plane (P), an obstacle taking up the greater part of said oscillation chamber and having a front wall (40) provided with a cavity (42) located opposite said opening and swept by the oscillating fluid jet. The invention is characterised in that two mutually parallel side walls (34, 36) extend on either side of the opening (22) and form a nozzle inside the oscillation chamber, in the direction of the obstacle, alonga longitudinal dimension less than the distance between the opening and the obstacle front wall.

Description

FLUID OSCILLATOR, SYMMETRICAL-RESPECT TO-A PLANE OF LONGITUDINAL SYMMETRY _DJEL = RIPCIQN OF. THE INVENTION The present invention relates to a symmetrical fluid aacilation with respect to a plane of longitudinal symmetry P., comprising a > An element that allows the finite to enter a chamber called an "oscillation" in the form of a two-dimensionally oscillating fluid jet with respect to said plane of meteors-Pv e_in.cl.xye an obstacle that cope. ... part of said oscillation chamber, and having a front wall ... provided with a cavity disposed-facing said opening, and which is swept by the oscillating fluid jet. Fluid oscillations are well known, and WO 93/22627 provides an example which is shown in a top view in Figure 1. This oscillator - (1) / s - pyrf with respect to a longitudinal symmetry plane P, comprises an oscillation chamber (3). __and an obstacle (5) housed inside it. The obstacle (5) has a front wall (7) in which a cavity called "front" .1,3.) --e-S ~ .p-r. ficada_ facing an opening (11). The aperture (11) defines a fluid inlet within the oscillation chamber (3) and = s cap to form a two-dimensional fluid chariot that oscillates transversely in relation to the longitudinal symmetry plane- P.ds.l_ oscillator . As a consequence of the operation of the fluid asc-ladar, when the fluid jet encounters the frontal cavity (9) _? he sweeps the same in the course of his ... illa, illa. main vortices are formed TI, T.2. on both sides of the jet (see Figure IX *) which are alternately high and low intensity, in opposition to phase and in relation to the flow of the fluid jet. Figure 14. The swirl TI occupies a space superior to that of the frontal cavity of the obstacle, and the swirl pressure is such that the jet is tilted from an extreme position despite the presence of the other whirlwind located T2. between the front-side (.7) of the obstacle (5) adjacent to the wall cavity (13) in relation to the oscillation chamber-in communication with the opening (11). in that position, a part of the flow of the jet is directed downstream of the obstacle, and another portion of the jet increases the vortex T2 which increases more and more, and where the pressure increases just at the moment when the pressure is enough to rock. eX jet to and on the other side, in the opposite extreme position. The container oscillates from this one form, from one extreme position to the other, and the detection of the frequency of the spill, the debris enables the flow of the fluid to be deferred, the frequency being considered. proportional to the flow. To reduce the errors in the determination of the fluid flow, the relation of the oscillation / flow rate should not vary too much depending on the de-flux regime. Or, under a so-called transition regime, ie For the Reynolds number, calculated for the flow located to the right of the opening 11, located in the vicinity of 300, Xa Applicant has been able to confirm the appearance of a high pressure zone (vortex T3) in the vicinity of . The base is the fluid jet on the side where the IT torrent is located, as well as swirl voids located with respect to the front wall below the vortices TI and T3 in the Figure 1. These tarb.ellinos reinforce the action of the whirlwind-TI and, therefore, it takes more time for the vortex T2 to acquire enough force in order to counterbalance _Xas pressures excercised by XI _ and T_3-and that decreases the oscillation fr-e, and thus introduces errors in the determination of the flow rate of the fluid. On the other hand, it is known by the LLS document -4.y.i t.23 _a fluid oscillator comprising a duct extending in the direction of a U-shaped obstacle which. Defines an oscillation chamber. The longitudinal dimension of the duct side walls is equal, even greater than the distance between the ends of the walls of the obstacle _and the apex of Xas -surfaces downstream of two elements of section in Xor to the semi-oval arranged perpendicularly with respect to the conduit and whose main axes are parallel to the direction of fluid flow. During the operation of the fluid oscillator, this type of conduit affects the oscillation of J. -charro - they affect or consi erably the development of the whirlwind Ti. The present invention aims to remedy these problems by proposing a symmetrical fluid oscillator with reXation to a plane of longitudinal symmetry P, comprising an opening that allows the fluid to enter a so-called oscillation chamber in the form of a jet. of fluid bidi ensional oscillating transversely with respect to the plane of symmetry P, an obstacle that occupies. most of the oscillation chamber and having a front wall provided with a cavity located opposite the opening, and which is swept by the fluid jet at a = Xta-t., characterized in that two side walls extend through. both parts of the opening., and Xa extend coa_ aoj afo to form a conduit inside the oscillation chamber, in the direction of the obstacle ,. a_ lo. Xarga of_ one. longitudinal dimension strictly inferior to the distance between the opening and the front of the obstacle, so that the end of the walls is not very close to the cavity. This cavity forms a protective screen for the jet of fluid against vortices located in the high pressure zone in the vicinity of the., Base-of the jet. which contribute to curving it excessively. The fluid jet is thus less subject to the influence of these disturbing vortices than in the prior art. Thus, the flux oscillator according to the invention has an increased oscillation frequency in the transition regime in relation to that of the fluid oscillator of the. technical- anterior. According to one feature, Xas LateraXes walls are substantially parallel to each other. Preferably the length of the longitudinal walls is between 0.75 and lb, where b denotes _Xa. i nstransverse or ncho d-e -Xa aperture. For example, -X-longitudinal dimension The side walls are substantially equal to b. Advantageously, the front wall of the obstacle comprises two essentially flat frontal surfaces, which frame the obstacle cavity. X plane of each one. of the surfaces is substantially perpendicular to the longitudinal symmetry plane JP. Advantageously, the oscillation chamber has two wall portions located on both sides of the wall, and comprises two surfaces respectively -disposed with respect to the front surfaces. of the obstacle, and that are sensibly parallel to it. According to a characteristic of the invention, the cavity is defined, by a surface possessing, in a plane of oscillation of the fluid jet, by a part, two straight portions substantially parallel to the plane of longitudinal symmetry P in the places said surface is spliced to each of the front surfaces s., and. by. On the other hand, a semicircular shaped portion of the cavity furthest from the opening is located at a distance Lo .from. the front wall of the obstacle between 2 . 3b and 2 5b, where xXX transverse dimension or eX. width of the opening. According to another characteristic of the invention, the di s tanci a- L_ between the. The opening and the front wall of the obstruction is included. between _2_- 3 .and 3. 2b-, where _b - - = -si na -Xa_ - dimension_ ión_ transvers to or the width of the opening. According to a feature of the invention, the fluid oscillator comprises at least two sensors for detecting variations in the speed or pressure of the flow rate of the fluid. Advantageously, the sensors for detecting the variations of the fluid flow rate of the fluid are arranged adjacent to the end of the passage or conduit. Other advantages and features of the invention will appear, apparent in the course of the following, description / given solely by way of non-limiting example, and with reference to the accompanying drawings, in which: - Figure 1 - is a -vi ta snperi or ... of .un-ose and 1-fluid of the prior art; - Figure -2 is the top view of X. fluid oscillator e. the present invention; Figure 3 is a top view of the fluid oscillator of Figure 2, in which the main vortices TI / _X2 have been represented for an extreme position of the fluid jet; Figure 4 is a graph showing the linearity curves of the fluid oscillator shown in Figure 2, with and without the onduct j or j. As shown in Figure 2, it is designated with the general reference 2Q ), a fluid oscillator used in relation to a gas flow rate with the sole value of determining the flow rate and the volume of gas flowing through the oscillator. The finite oscillator L2.0) is symmetrical with respect to a plane of longitudinal symmetry P along which it is aligned. (22) that allows the flow rate to penetrate into a so-called "oscillation" chamber (24) _, in the middle of which an obstacle (26) occupying the largest part-of-the-chamber is positioned. and - an exit-outlet (28) for the evacuation of the flow of gas out of the oscillation chamber. The oscillation chamber is determined by two walls (30, 321 symmetrical with respect to the plane P, which agree between -yes -Xas -Xert.ur.as -of -input and output.The entrance opening X22.). .made in the form of one. slot of transverse dimension, whose width b, constant, is its greatest dimension. The height is contained in a plane perpendicular to the plane of Figure 2. The slot is extended to the long, of Xa dire-CC ón_.XongitudinaX that. corresponds to the direction of alignment of the entrance (22) and exit (2_8) openings by two lateral walls (34, 36) parallel to each other./ and which form a conduit (38). Said side walls extend into the interior of the oscillation chamber (24), respectively., From each wall-L3-Q 3.21 of. Xa oscillation chamber, on both sides of the entrance opening on the total aperture of the. same The conduit transforms the flow rate of the gas that passes through it. what. It is represented by the arrow F, in a stream of b.idimensional Flux LeX fluid jet - it remains approximately the same along the direction parallel to the height of the groove), which oscillates axially in -Xaxis to the plane of symmetry. langXtndinaX P. The oscillation chamber (24) defines with its walls (3JQ _, _ 32) together with the walls of the obstacle (26) two channels _C1_, £ .2 that allow the flow of gas XXujo - to be discharged alternatively by one or another channel to the outlet (28.) of the fluid oscillator. The obstetrician (26) has a front wall (.40) in which a cavity (42) located facing the entrance conduit (38) is practiced, where there is a sweep by the fluid jet in the course of its operation. despXaz.ami nto in his. oscillation movement. The front wall (.40) of oxture L25) also comprises two surfaces, called front surfaces (44, 46), which are symmetrically located on each side of. the cavity (42), which are essentially flat. The plane within which the front surfaces are arranged is substantially perpendicular to the plane of longitudinal symmetry P and to the direction of flow rate X. relative to the slot (22). The oscillation chamber (24) also comprises two wall portions (30a, 32a) which are arranged symmetrically to both Xados of the groove (22) facing the front surfaces (44, 46).

The wall portions (30a, 32a) have surfaces that. They are. pair the front surfaces (44, 46). Assumed.,. The vortices that form on both sides of the jet are positioned in the free spaces located between. frontal surfaces Í44, 46) and surfaces-. cor.es.pon.dient s of the. wall portions (_30a, .3? a) --These, weave 11 and we-san.-in this way developed almost freely between said surfaces. It is not necessary that the dimensions - ransverse 1 PS, or the wide Ea of the front surfaces (44, 46) are of large dimensions for said surfaces to fulfill their function, and a wide Fo between Q_.8b ..and .4b-, example pair equal to 1. 2b is extremely convenient ^ The distance L between the frontal surfaces ÍA.4 .. ,, 46) .. ^ - Xas. super-ficies of the portions of paxed. (30a, 32a.). It should not be too small, in order to leave an e-sp-acic.- free, sufficient for the development of the whirlwinds. Indeed, if .Xa distance .X is too small, for example less than 2.8b, then problems can arise in the laminar regime, because the turbulence pressure increases too rapidly, and in. As a consequence, the dog swings very quickly. The distance L is for example equal to 3b. The -cavity (42) presents, in the plane of Figure 2, a surface where ei. The profile allows the fluid to be guided within the cavity in the course of its oscillation, and to prevent any creation of a recirculation phenomenon inside the cavity. In the plane of Figure 2_, the surface of the cavity is delimited by two straight portions (42a, 42b) which are substantially parallel to the plane of longitudinal symmetry P, and which respectively connect the two frontal surfaces. { AA4 46) at the entrance of the cavity .. The surface of the cavity is also delimited by. a. portion of semicircular shape (42c) which is attached to the straight portions., and which also forms the bottom of the cavity. In this way, the flow rate coming from the jet that has separated when it meets the surface of the cavity, and which is guided by said surface, has a s-ens-i b1 epi eate direction. paraXela to the plane P when leaving the aforementioned cavity. In any case, other convenient configurations may also complete the functions cited above. For example, the profile of the surface can be parabolic. Moreover, what can the surfaces of the wall portions (30a, 32a) be parallel to the front surfaces? 6 _, and that the outflow flow of the cavity (42) has a substantially perpendicular direction to said surfaces allows it to communicate with the flow rate found on the surfaces of wall portions (J3.na_). , -32a) ... an angle of incidence too far from the perpendicular .a. Xas _supexfici_, whatever the flow rate is. , In erect, the incidence angle too far from. the perpendicular to the surfaces will have as a consequence -modify the section of X torbeXXino positioned between one of the frontal surfaces and the consxderada surface -corresponding to the wall portion (30a., 32a) -_ Convien- also notice that Xa cavity is deeper than that of the fluid oscillator of the prior art ^ represented in Xa. Figure, to allow the morphology of the main turbine TI to be fixed, whatever the flow regime of the finum (laminar, transient, turbulent). Also, at very low flow rates, that is, for ReynoXds numbers in the vicinity of 5_Q, a vortex may develop in a manner similar to that under a turbulent regime, within said cavity. This also makes it possible to measure a frequency of jet radiation for Reynolds numbers in the vicinity of 50, which is not possible with the oscillator cavity of Figure 1. The cavity portion which is farthest from the slot. (22) is located at a distance Lo from the front surfaces (44, 46) which are disposed in the plane of the opening of the cavity, the co being supplied between .2 .__ 2b and_2.5b_, - .pa example equal to 2-b .. In effectj the cavity (42) should not be too deep - (par_ example Lo = 3b) so that the action of the torbeXlino TI on eJL jet is not reinforced. __ aj-O-s -_c.aiLdale.Sr well - in this way the oscillation frequency of the jet will be significantly weakened. FORMER. width. Ro of the cavity (42) between the two straight portions l_42a_, 42b.) Is comprised between 3.4b and 3.8b, and is p r, example equal to 3.6b. When the slot extends the conduit (38) ,. when the jet of fluid is bent towards a position such as that shown in Figure 3, the jet is isolated from the disturbing action of the vortices situated between the front surface (-4.6) and the corresponding surface of the wall portion. (32a) inside. this, canaiizada portion, by the wall (34, 36). The jet thus becomes rigid in. sn_base, which allows it to resist the disturbing action .. of the parasite torbeXXinQS-, .and on. consequence to have, one. oscillation frequency much higher than that of the prior art (Fissure 1) in a regime, of. transition. Moreover, ..with _the_configuration -of the oscillator of - Fluid according to the invention, and represented in the Figures 2 j and 3, the jet is still more "folded" in its free portion, than in the prior art device, it being also observed that the jet folds in reXation to the front surface (44) in the direction of the corresponding surface of the . portion of the wall (3.0a) that leaves less room for the development of the vortex T2_. Es.ta e__. fill the reason why the vortex T2 will be fed in pressure faster than., in. the previous technique, going the pressure exerted by IT where it is more - quickly compensated, which causes the jet to swell more quickly.

The longitudinal dimensions .J_e. -X.as lateraXes walls .. (3.4, 361 should be smaller than the distance L_, in order to .. that said na walls are too close to the cavity (42) that will be fully occupied by one of the whirlpools IX, ... while the other whirlwind T2 will be located in the free space located between the front surface, 14..4.), and the surface with respect to the portion of ... wall. See Figure 3.)? In effect, the walls. too large laterals (for example Le = 2b) _generate the development of torbeilinos-TI and where the oscillation of the jet affects. The development of. vortex _I2 will be. also modified, since the jet will then remain inside the cavity, and thus forces T2 to amplify, within a restricted space. Advantages.amen.te, Xa dimension .Xe is r.np rp? H i ría-eja.tx.e- CLX7-5b and Ib, and for example is equal to 0.9b. On the other hand. Part., Xa presence of .Xas. walls isolates the base. of the. chorra de. fXuido of the return flows that u pn p nvncar & rm rf > ? __. n the -detection -of the frequency of oscillation of the jet. As represented by FIG. 2, the side walls 34, 36 of the conduit 38 have a constant spacing along the longitudinal dimension Le, except for the level of the junction between the side walls and the wall portions. (3Qa, 3.2a.) Where the surface of the laterator wall forms a slight concavity. It is important that the side walls take the smallest ..place - possible. with the purpose of not generating the .. development of the main vortices Ti. and I2-. In this way, the side walls (34, 36) can take the form of two very thin straight sheets, which reach to guide the. chorra of fluid and protect against disturbances. The configuration of the fluid oscillator described in 1Q__ above allows to obtain a vortex morphology Ti and T2 which varies little depending on the flow regime of. flow, and that ensures a good measurement. The fluid oscillator of Figure _2 allows for the operation of the. flow of gas that crosses it thanks to two pressure taps. located at X points we enter the sweep of the gas jet inside the cavity (42). _J_.ich. s -pressure symptoms are linked to known devices. that allow to measure the frequency of oscillation of the jet. An adequate calibration allows linking the frequency to the flow.

The sensors -thermal or ultrasonic sensors can also be used to detect the variations in the flow velocity of the jet stream in order to determine the frequency of oscillation of the jet. The sensors may also be placed between the conduct (38) and the obstacle (26) within the upper wall (not shown in Figure 2) forming the cover, of the. Fluid oscillator, or also in the bottom wall. of the flux oscillator (which forms the background plane in .la Ergura.2). _ The location of the sensors (48, 50) is indicated. p-T-two circles in. Figure 2. It should be noted that in the plane of -la Figure 2. The seams (4.8., 50) are advantageously located in front of the end of the base (38) and are displaced a. a dXstance less than or equal to the displacement of the side walls (34_, 36) with eX end-e-s _-_ r. -location a-s- within the fluid flow rate. For low flows, a layer -limit _development to the lar, ga of the. inner surface of the side walls (34, 36.) and confers to the jet in the outlet of the duct (38) a gradient of more accentuated speed, than that obtained in the base of X jet -situated aligned to the opening (11) on the Figure 1, and where the signal detected by the sensors is stronger than in the prior art.- In this way, the. detection, of the frequency of oscillation of the fluid jet at low flow rates, par. The sensors (48,. 5.0.) located in front of the duct (38) become easier - that. in. the ascending of the prior art. On the other hand, for high flow rates, the sensors thus positioned are protected from disturbances due to the flow of return flow that are at risk. from. be detected by the sensors. Figure 4 shows three fluid-oscillating nanometer curves with three different configurations: curve A corresponds to that of the oscillator of Figure __2-sin, the. inlet duct (38); the curves B and C are those of the oscillator of Figure 2 for two different lengths of the conduit (38), one with the length of 0.5b (curve B) and the other for a length of Ü__3b Xcurva Ci - For the oscillators, the iiai ob of Xa groove (22) is equal to 19 mm, and the other dimensions are those that are defined above as a function of the magnitude b__. In this way, the presence of a conduit in the interior of the oscillating chamber has the effect of increasing the frequency of oscillation of the jet in a transition regime, and correcting the linearity of the curve. oscillator. fluid. By slightly lengthening the duct, the effect is also increased, but it is convenient to do not increase the louder dimensions too much, since then the frequency of tilt of the jet has the risk of increasing considerably under a laminar regime. The fluid oscillator can be applied to both a gas. bed to a liquid (water, vehicle fuels, etc.).

Claims (11)

1. REJVIMHIC- C-XÜNIS 1. Oscillator of. symmetrical fluid relative to a plane of longitudinal symmetry, comprising an opening that perinitequ e-el. fluid penetrate, to a camera called oscillation chamber, .in the form of a ^ C ± LOJC? Hydraulic fluid that oscillates transversally relative to the plane of symmetry, an obstacle occupies most of. the camera, of oscillation - and has a front wall provided with a cavity located opposite the opening, - __ is. The two side walls extend over both parts of the opening and extend it to form a conduit in the interior of the chamber. to cXlation ,, in the direction of X obstacle, along a longitudinal dimension strictly lower than the. distance between the opening and the front wall of the obstacle, so that the end of the walls is not very close to the cavity.
2. 2. Fluid oscillator according to claim X ,. in. which the side walls are substantially parallel to each other.
3. 3. - Oscillator- of. fluid according to claim 1 or 2, in which the longitudinal dimension Le of the side walls -is between 0 --- 75- and lr where bd s-igna the transverse dimension or width of the opening.
4. 4_ Fluid oscillator. according to claim 3, in which Xa dimension 1ongl uciinai Le of the side walls is substantially equal to b.
5. 5. Fluid oscillator according to any of the above indications 1 to 4, in which the front wall of the obstacle comprises two essentially flat frontal surfaces which. they frame the obstacle cavity, the plane of each of the surfaces is substantially erpendicular to the plane of longitudinal symmetry.
6. 6. Fluid oscillator according to .. 1 to claim. 5, in which the oscillation chamber has two wall portions located for more parts of the opening. and they comprise two surfaces respectively disposed with respect to the superhighways of the obstacle, and are substantially parallel thereto.
7. Fluid oscillator according to claim 5, wherein the cavity is defined by a surface that., Possesses *, in. he. plane of oscillation of the jet of fluid., on the one hand, two straight portions substantially parallel to the plane of longitudinal symmetry at the sites that said surface is _. splice a.- each of the frontal surfaces, and on the other hand, a portion of iorma-semicircular spliced to the straight portions.
8. 8. Fluid oscillator in accordance with any of the. claims. 1 to 7, in the fourth part of the cavity further away from the opening is located, at a distance Lo from the front wall of the obstacle comprised between 2.2b and 2.5b, where b designates the dimension. cross section or width of the opening.
9. 9. Fluid oscillator according to any one of claims 1 to 8, in which the distance L between the opening and the front wall or obstacle is between 2.8 and 3.2b, where b designates the d i T? ? S i? N tra_-s ___ r_-al or width -of-the opening.
10. 10 Fluid oscillator in accordance with any of .1 -i v-i n i < -a < --i nnp.g; _a ~ ~ r - --that - you have at least two. sensors for detecting variations in the speed or pressure of the fluid flow.
11. 11. Fluid oscillator according to claim 1.0, in which the sensors for detecting the variations of the fluid flow velocity are arranged in the vicinity of the pipe opener.