FLOW STRAIGHTENER AND RELATED VENTURI MIXING DEVICE

Abstract

Flow straightener (434; 43B) comprising a cylinder (44) having an inlet mouth (46) and an outlet mouth (47), the cylinder (44) being internally provided with a helical rib (45) running on an inner surface (450) of the cylinder (44), wherein a ridge (456; 460) of the helical rib (45) follows a cylindrical helix with pitch p wrapped around a cylindrical volume having diameter d coaxial with the cylinder (44), whereby the ridge (456; 460) of the helical rib (45) delimits a clear central cylindrical section of the cylinder (44) having diameter d, wherein the helical rib (45) has a front main surface (457), facing the inlet mouth (46), and a rear main surface (458), facing the outlet mouth (47), the front main surface (457) forming with the inner surface (450) of the cylinder (44) a front angle that is obtuse, whereby 90<<180.

Claims

1-14. (canceled)

15. Venturi mixing device comprising a body having an inlet and an outlet nozzle, and, internally to the body, a main flow restricting channel communicating with the inlet and with a suction chamber, the suction chamber being in communication with a mouth communicating with the outside, an outlet channel being in communication with the suction chamber and ending with the outlet nozzle, wherein the outlet channel is provided with a flow straightener comprising a cylinder configured to be stably placed in a duct and having an inlet mouth and an outlet mouth, the cylinder being internally provided with a helical rib running on an inner surface of the cylinder, wherein a ridge of the helical rib follows a cylindrical helix with height h and with pitch p wrapped around a cylindrical volume having diameter d coaxial with the cylinder, whereby the ridge of the helical rib delimits a clear central cylindrical section of the cylinder having diameter d, wherein the helical rib has a front main surface, facing the inlet mouth for the whole height h of the helical rib, and a rear main surface, facing the outlet mouth for the whole height h of the helical rib, the front main surface forming with the inner surface of the cylinder a front angle that is obtuse, whereby
90<a<180, wherein the inlet mouth of the cylinder of the flow straightener is facing the inlet of the venturi mixing device and the outlet mouth of the cylinder of the flow straightener is facing the outlet nozzle of the venturi mixing device.

16. Venturi mixing device according to claim 15, wherein the inner surface of the cylinder has diameter D and wherein the diameter d of the clear central cylindrical section ranges from 40% to 90% of D, i.e.
0.4.Math.Dd0.9.Math.D.

17. Venturi mixing device according to claim 15, wherein the front angle ranges from 115 to 165.

18. Venturi mixing device according to claim 15, wherein the rear main surface forms with the inner surface of the cylinder a rear angle b ranging from 45 to 135.

19. Venturi mixing device according to claim 15, wherein a ratio between pitch p of the cylindrical helix followed by the ridge of the helical rib and length c of a projection of the helical rib on the inner surface of the cylinder is not lower than 1, i.e.
pc.

20. Venturi mixing device according to claim 15, wherein the cylinder has height H and the helical rib extends only for the entire height H of the cylinder.

21. Venturi mixing device according to claim 15, wherein the ridge of the helical rib describes not more than two turns of the cylindrical helix.

22. Venturi mixing device according to claim 15, wherein the ridge of the helical rib is substantially linear.

23. Venturi mixing device according to claim 15, wherein the ridge of the helical rib is a surface that is a helical portion of a cylindrical surface.

24. Venturi mixing device according to claim 22, wherein the helical rib has polygonal axial cross-section.

25. Venturi mixing device according to claim 22, wherein the helical rib has triangular axial cross-section.

26. Venturi mixing device according to claim 23, wherein the helical rib has trapezoidal axial cross-section.

27. Venturi mixing device according to claim 15, wherein the flow straightener is placed in correspondence with the outlet nozzle.

28. Venturi mixing device according to claim 16, wherein the diameter d of the clear central cylindrical section ranges from 50% to 75% of D, i.e.
0.5.Math..Math.Dd0.75.Math.D.

29. Venturi mixing device according to claim 28, wherein the diameter d of the clear central cylindrical section ranges from 60% to 65% of D, i.e.
0.6.Math.Dd0.65.Math.D.

30. Venturi mixing device according to claim 17, wherein the front angle ranges from 120 to 150.

31. Venturi mixing device according to claim 30, wherein the front angle ranges from 130 to 140.

32. Venturi mixing device according to claim 18, wherein the rear angle b ranges from 75 to 120.

33. Venturi mixing device according to claim 32, wherein the rear angle b ranges from 90 to 105.

34. Venturi mixing device according to claim 33, wherein the rear angle b is substantially equal to 90.

35. Venturi mixing device according to claim 15, wherein the ridge of the helical rib describes at least one-half of a turn of the cylindrical helix.

36. Venturi mixing device according to claim 35, wherein the ridge of the helical rib describes only one turn of the cylindrical helix.

37. Venturi mixing device according to claim 25, wherein the helical rib has right angle triangle shape.

Description

[0035] The present invention will be now described, by way of illustration and not by way of limitation, according to its preferred embodiments, by particularly referring to the Figures of the annexed drawings, in which:

[0036] FIG. 1 schematically shows a perspective view (FIG. 1a) and a longitudinal section view (FIG. 1b) of the hydraulic circuit of a mixing apparatus according to the prior art;

[0037] FIG. 2 schematically shows a longitudinal section view of a venturi mixer device according to the prior art;

[0038] FIG. 3 shows an exploded perspective view of a preferred embodiment of the venturi mixer device according to the invention;

[0039] FIG. 4 shows an exploded longitudinal section view of the mixing device of FIG. 3;

[0040] FIG. 5 shows a perspective view of a first embodiment of the flow straightener according to the invention;

[0041] FIG. 6 shows an axial plane section view of the flow straightener of FIG. 5; and

[0042] FIG. 7 shows an axial plane section view of a second embodiment of the flow straightener according to the invention.

[0043] In the Figures identical reference numerals will be used for alike elements.

[0044] Making reference to FIGS. 3 and 4, a preferred embodiment of the venturi mixing device 40 according to the invention comprises a body 41 having an inlet 42 and un outlet nozzle 221. Internally to the body 41, the mixing device 40 comprises a main flow restricting channel 5 (i.e. configured to make a restriction of the main flow) wherein, upon the passage of water coming from the inlet 42, a low pressure and hence an aspiration of the chemical product from a mouth 82 of an external tank and its dilution in water are generated, which dilution occurs in the outlet channel 225, starting from the suction chamber 222 and ending with the outlet nozzle 221.

[0045] In correspondence with the outlet nozzle 221, the outlet channel 225 is provided with a first embodiment of the flow straightener 43A according to the invention, comprising or consisting of a cylinder 44 having an inlet mouth 46, where the fluid flow enters, and an outlet mouth 47, from which the fluid flow exits; in particular, when the flow straightener 43A is inserted into the outlet nozzle 221 of the outlet channel 225 of the mixing device 40, the inlet mouth 46 is facing the inlet 42 of the mixing device 40 itself, while the outlet mouth 47 is facing (optionally aligned with) the outlet nozzle 221. In other words, the cylinder 44 is configured to be stably placed in a duct, i.e. in the outlet channel 225.

[0046] Making reference also to FIGS. 5 and 6, it may be observed that the cylinder 44, having height H, is internally provided with one helical rib 45 with triangular axial cross-section running on the inner surface 450 of the cylinder 44 from the inlet mouth 46 to the outlet mouth 47. The triangular axial cross-section of the helical rib 45 has a base side 451, having length c, lying on the inner surface 450 of the cylinder 44, a front side 452 facing the inlet mouth 46, and a rear side 453 facing the outlet mouth 47. As shown in FIGS. 5-6, the front side 452 corresponds to the front surface 457 of the helical rib 45 directly exposed and opposed to the direction of the fluid flow (represented by arrows F in FIG. 6), the base side 451 corresponds to the projection of the front surface 457 of the helical rib 45 on the inner surface 450 of the cylinder 44, and the rear side 453 corresponds to the rear surface 458 of the helical rib 45 not opposed to the direction F of the fluid flow; in particular, the front surface 457 remains directly exposed and opposed to the direction F of the fluid flow for the whole extension, i.e. for the whole height h, of the helical rib 45, whereby the rear surface 458 remains not opposed to the direction F of the fluid flow for the whole height h of the helical rib 45. The front side 452 corresponds to the width of the front surface 457 (and optionally remains constant for the whole height h of the helical rib 45); similarly, the rear side 453 corresponds to the width of the rear surface 458 (and optionally remains constant for the whole height h of the helical rib 45). In the first embodiment of the flow straightener shown in FIGS. 3-6, the triangular axial cross-section of the helical rib 45 is a rectangle triangle wherein the rear side 453 is orthogonal to the inner surface 450 of the cylinder 44 and the front side 452 is the rectangle triangle hypotenuse (whereby the base side 451 corresponds to the projection of the helical rib 45 on the inner surface 450 of the cylinder 44); however, it must be noted that in other embodiments of the flow straightener according to the invention, the helical rib may have an axial cross-section shaped as any triangle, in particular not a rectangle triangle.

[0047] The inner surface 450 of the cylinder 44, the axis of which is indicated with reference numeral 454, has diameter D. The ridge 456 (that is substantially linear) of the helical rib 45, defined by the vertex 455 of the triangular axial cross-section of the helical rib 45 inside the cylinder 44 (i.e. the triangular axial cross-section vertex 455 opposed to the inner surface 450 of the cylinder 44 and to the base side 451 of the triangular axial cross-section of the helical rib 45) delimits a clear central cylindrical section having diameter d of the flow straightener 43A. In other words, the ridge 456 of the helical rib 45 follows a cylindrical helix wrapped around a cylindrical volume having diameter d coaxial with the cylinder 44; in particular, in the flow straightener 43A of FIGS. 3-6, such cylindrical helix is right handed (i.e. the helix axial advancement occurs with a right handed rotation, i.e. clockwise), even if this is not an essential feature for the invention.

[0048] In the first embodiment of the flow straightener shown in FIGS. 3-6: [0049] the front angle formed, externally to the axial cross-section triangle, by the front side 452 and by the inner surface 450 of the cylinder 44 (i.e. the front angle formed by the front surface 457 of the helical rib 45 and by the inner surface 450 of the cylinder 44), that is preferably substantially constant, is substantially equal to 135 (whereby the triangular axial cross-section of the helical rib 45 is a isosceles rectangle triangle); [0050] the cylindrical helix pitch p (i.e. the height of one full turn of the helix measured parallel to the helix axis 454) is substantially equal to 220% of the length c of the base side 451 of the triangular axial cross-section of the helical rib 45, i.e.

p=2.2.Math.c; [0051] the diameter d of the clear central cylindrical section of the flow straightener 43A defined (by the vertex 455 of the triangular axial cross-section of the helical rib 45 inside the cylinder 44, i.e.) by the ridge 456 of the helical rib 45 is substantially equal to 62% of the diameter D of the inner surface 450 of the cylinder 44; [0052] the helical rib 45 extends for the whole height H del cylinder 44 (i.e. the height h of the helical rib 45 is equal to the height H of the cylinder 44, i.e. h=H); and [0053] the ridge 456 describes one full turn of the cylindrical helix wrapped around the cylindrical volume of diameter d, whereby the front surface 457 describes one full turn of the cylindrical helix.

[0054] Other embodiments of the flow straightener according to the invention may have the helical rib having a polygonal axial cross-section wherein the polygon has more than three sides, instead of a triangular axial cross-section. By way of example, and not by way of limitation, FIG. 7 shows a second embodiment of the flow straightener according to the invention, indicated with reference numeral 43B, having one helical rib having a trapezoidal axial cross-section running on the inner surface 450 of the cylinder 44 from the inlet mouth 46 to the outlet mouth 47 for the whole height h of the cylinder 44 (i.e. the height h of the helical rib is equal to the height H of the cylinder 44, i.e. h=H); in particular, the trapezium of the axial cross-section is not rectangular, even if in other embodiments of the flow straightener according to the invention the helical rib may have a rectangular trapezium shaped axial cross-section. The trapezoidal axial cross-section of the helical rib has also a base side 451, having length c, lying on the inner surface 450 of the cylinder 44, a front side 452 facing the inlet mouth 46, a rear side 453 facing the outlet mouth 47, and an inner side 459 parallel to the inner surface 450 of the cylinder 44 (i.e. parallel to the base side 451), having length b shorter than c (i.e. b<c). The front side 452 corresponds to the front surface 457 of the helical rib directly exposed and opposed to the fluid flow direction F, the base side 451 corresponds to the projection of the helical rib on the inner surface 450 del cylinder 44, the rear side 453 corresponds to the rear surface 458 of the helical rib not opposed to the fluid flow direction F, and the inner side 459 corresponds to the surface 460 constituting the helical rib ridge and that is a helical portion of a cylindrical surface of diameter d coaxial to the cylinder 44 (i.e. it is a portion delimited by a front edge 461 and a rear edge 462 parallel to each other each of which follows a cylindrical helix wrapped around a cylindrical volume having diameter d coaxial with the cylinder 44). In other words, the surface 460 constituting the helical rib ridge follows a cylindrical helix wrapped around a cylindrical volume having diameter d coaxial with the cylinder 44; even in the flow straightener 43B of FIG. 7, such cylindrical helix is right handed (even if, as stated above, this is not an essential feature for the invention).

[0055] In the second embodiment of the flow straightener shown in FIG. 7: [0056] the front angle formed, externally to the axial cross section trapezium, by the front side 452 and by the inner surface 450 of the cylinder 44 (i.e. the front angle formed by the front surface 457 of the helical rib and by the inner surface 450 of the cylinder 44) is still substantially equal to 135; [0057] the rear angle formed, externally to the axial cross section trapezium, by the rear side 453 and by the inner surface 450 of the cylinder 44 (i.e. the rear angle formed by the rear surface 458 of the helical rib and by the inner surface 450 of the cylinder 44), that is preferably substantially constant, is substantially equal to 105; [0058] the cylindrical helix pitch p is substantially equal to 4/3 of the length c of the base side 451 of the trapezoidal axial cross-section of the helical rib, i.e.

p=(4/3).Math.c; [0059] the length b is 20% of the length c; [0060] the diameter d of the clear central cylindrical section of the flow straightener 43B defined by the surface 460 constituting the helical rib ridge is still substantially equal to 62% of the diameter D of the inner surface 450 of the cylinder 44; [0061] the helical rib still extends for the whole height H of the cylinder 44, i.e. the height h of the helical rib is equal to the height H of the cylinder 44, i.e. h=H; and [0062] the front edge 461 of the surface 460 constituting the helical rib ridge describes one full turn of the cylindrical helix wrapped around the cylindrical volume of diameter d, whereby the front surface 457 describes one full turn of the cylindrical helix.

[0063] In further embodiments of the flow straightener according to the invention, the helical rib may have a polygonal axial cross-section different from a triangular or trapezoidal axial cross-section as those shown for the straightener 43A (see FIGS. 3-6) and for the straightener 43B (see FIG. 7), respectively. Moreover, the helical rib may have an axial cross section different from a polygonal cross section, for instance comprising at least partially one or more curvilinear contours.

[0064] Generally, the flow straightener according to the invention has the helical rib having (at least) one front main surface, i.e. a surface facing the inlet mouth of the flow straightener that is directly exposed and opposed to the fluid flow direction F for the whole height h of the helical rib 45 and that has a width optionally remaining constant for the whole height h of the helical rib 45, and (at least) one rear main surface, i.e. a surface facing the outlet mouth of the flow straightener that is not opposed to the fluid flow direction F for the whole height h of the helical rib 45 and that has a width optionally remaining constant for the whole height h of the helical rib 45, wherein the front main surface forms with the inner surface 450 of the cylinder 44 (at least) one respective front angle that is preferably substantially constant and that is obtuse, whereby

90<<180,

and the rear main surface forms with the inner surface 450 of the cylinder 44 (at least) one respective rear angle that is preferably substantially constant. Optionally, the front angle ranges from 115 to 165 (i.e. 115165), more optionally ranging from 120 to 150 (i.e. 120150), still more optionally ranging from 130 to 140 (i.e. 130140). The rear angle optionally ranges from 45 to 135 (i.e. 45135), whereby the rear main surface forms with the inner surface 450 of the cylinder 44 a sort of recess (creating a low pressure in the fluid) when the rear angle is acute (i.e. when <90); more optionally the rear angle ranges from 75 to 120 (i.e. 60120), still more optionally the rear angle ranges from 90 to 105 (i.e. 90105), even more optionally the rear angle is substantially equal to 90. Obviously, the just indicated values for the front and rear angles and may be used for embodiments of the flow straightener according to the invention having helical rib with triangular or trapezoidal axial cross-section similar to those shown in FIGS. 6 and 7, respectively (it must be noted that the rear angle (3 of the flow straightener 43A of FIG. 6 is substantially equal to 90).

[0065] In further embodiments of the flow straightener according to the invention, the values of the ratio between the diameter d of the clear central cylindrical section of the flow straightener defined by the helical rib ridge and the diameter D of the inner surface 450 of the cylinder 44 may be different from that of the embodiments shown in FIGS. 6 and 7 (equal to 0, 62). In general, the diameter d of the clear central cylindrical section optionally ranges from 40% to 90% of D, i.e.

0.4.Math.Dd0.9.Math.D,

more optionally ranges from 50% to 75% of D, i.e.

0.5.Math.Dd0.75.Math.D,

still more optionally ranges from 60% to 65% of D, i.e.

0.6.Math.Dd0.65.Math.D.

[0066] In other embodiments of the flow straightener according to the invention, the values of the ratio between cylindrical helix pitch p and length c of the base side 451 of the helical rib axial cross section may be different from those of the embodiments shown in FIGS. 6 and 7, substantially equal to 2, 2 and 4/3, respectively). In particular, the ratio between cylindrical helix pitch p and length c of the base side 451 of the helical rib axial cross section must be configured to create a swirling motion of the fluid entering the inlet mouth 46; generally, the optimal value may also depend on the fluid flow speed, fluid viscosity and ratio between diameter d of the clear central cylindrical section and diameter D of the inner surface 450 of the cylinder 44. Optionally, the ratio between cylindrical helix pitch p and length c of the base side 451 of the helical rib axial cross section is not lower than 1, i.e.

pc

[0067] Other embodiments of the flow straightener according to the invention may have the helical rib extending only for a portion, optionally a central one, of the height H of the cylinder 44, whereby the helical rib height h is generally less or equal to the height H of the cylinder 44, i.e. hH.

[0068] Further embodiments of the flow straightener according to the invention may have the helical rib ridge that describes more than one full turn, not necessarily an integer number of turns, preferably not more than two full turns (in order not to introduce significant pressure drops, most of all in in steady state operating conditions), or less than one full turn of the cylindrical helix wrapped around the cylindrical volume of diameter d. Optionally, the helical rib ridge describes at least half of a full turn of the cylindrical helix wrapped around the cylindrical volume of diameter d, whereby the helical rib ridge may describe a helix with height h equal to k.Math.p (i.e. h=k.Math.p), where k is a positive value, even a decimal one, preferably not larger than 2 (i.e. k2), optionally not lower than 0, 5 (i.e. k0, 5).

[0069] In further embodiments of the flow straightener according to the invention, the helical rib ridge may follow a left handed cylindrical helix (i.e. the helix axial advancement occurs with a left handed rotation, i.e. counterclockwise).

[0070] Thanks to its structure, the flow straightener according to the invention effectively acts for breaking the fluid flow creating a swirling motion of the mixed fluid in the outlet channel 225 of the venturi mixing device 40. This allows the outlet channel 225 itself to be filled, ensuring a wide clear central section, having diameter d, for the passage of the fluid and, consequently, it effectively allows the venturi mixing device to activate, without generating any resistance or flow rate decrease, substantially obtaining no pressure drop in steady state operating conditions and avoiding possible obstructions due to limestone or chemical reactions.

[0071] Differently from the preferred embodiment shown in FIGS. 3-4, other embodiments of the venturi mixer device according to the invention may have the outlet channel that is provided with a flow straightener according to the invention not necessarily placed in correspondence with the outlet nozzle.

[0072] The preferred embodiments of this invention have been described and a number of variations have been suggested hereinbefore, but it should be understood that those skilled in the art can make other variations and changes without so departing from the scope of protection thereof, as defined by the attached claims.