US3598153A

US3598153A - Mass flow rate equalizer usable for exhaust or supply openings of a duct

Info

Publication number: US3598153A
Application number: US845189A
Authority: US
Inventors: Taro Hayashi; Aritsune Moriyama
Original assignee: Sanko Air Plant Ltd
Current assignee: Sanko Air Plant Ltd
Priority date: 1968-11-30
Filing date: 1969-07-28
Publication date: 1971-08-10
Anticipated expiration: 1988-08-10
Also published as: CH512676A; FR2024607A1; GB1266917A; GB1266918A; BE737434A; SE355398B; DE1946667B2; DE1946667A1; DE1946667C3

Abstract

An improved mass flow rate equalizer disposed in a vicinity of opening terminals of a flow duct with inclination against flow direction and having one or more flow passable cutoffs whose flow passable effective area decreases gradually along the flow direction. The equalizer may favorably be provided with one or more perforations having angles with respect to the flow direction.

Description

United States Patent Inventors Appl. No.

Filed Patented Assignee Priority MASS FLOW RATE EQUALIZER USABLE FOR EXHAUST on SUPPLY omvmcs OF A DUCT 6 Claims, 2: Drawing Figs.

U.S.Cl......

511 1111.01 5111/02 501 FieldofSearch 138/37- [56] References Cited UNITED STATES PATENTS 1,377,970 5/1921 Parent.1 138/42 3,286,992 ll/l966 Armeniadesetal. 13s/42x Primary Examiner-Houston S. Bell, Jr, Altorneys- Robert E. Burns and Emmanuel J. Lobato ABSTRACT: An improved mass flow rate equalizer disposed in a vicinity of opening terminals of a flow duct with inclination against flow direction and having one or more flow passable cutoffs whose flow passable effective area decreases gradually along the flow direction. The equalizer may favorably be provided with one or more perforations having angles with respect to the flow direction.

PATENTED AUBI 01971 3.598.153

sum 1 (IF 4 ATTORNEY PATENTEUAUGIOBH 3,598,153

sumuura III/III) Jul/III!!! IIII ATTORNEY MASS FLOW RATE EQUALIZER USABLE FOR EXHAUST OR SUPPLY OPENINGS OF A DUCT The present invention relates to an improved mass flow rate equalizer usable for exhaust or supply openings of a duct, more particularly to an improved mass flow rate equalizer having, in combination with an inside wall of the duct at least one effective flow-passable opening decreasing in its extent along an advancing direction of the flow processed therethrough.

In the following description, reference will be mainly made to the case of a supply opening of a duct for the simplification of the explanation. However, the art of the present invention is well applicable to the case of an exhaust opening of a duct with a same effect byintroducing a suitable modification thereto as stated later in detail.

For the purpose of equalization ofa mass flow rate passing through a supply opening of a duct, various attempts have been proposed in the field of hydrodynamics. Those attempts can be classified into several groups. In the flowing system of the first group, the supply opening is provided with a rear wall disposed in an inclined arrangement with respect to an advancing direction of the flow. When the variation of the mass flow rate across the opening is 15 percent or smaller, the supplied flow is considered as being in an equalized condition. By adopting the above-described inclined rear wall structure, it is feasible to decrease the dimensions of the flow duct with respect to those of the supply opening to some extent. However, no considerable decrease in the flow duct dimensions can be attained by this method. Besides, it is also difficult to make the mass flow rate variation smaller than 15 percent even when this method is employed.

Another group of the flowing system includes one or more flow resistants disposed in the duct across the supply opening. Although this system can present an appreciable mass flow rate equalizing effect, it is inevitably accompanied with considerable pressure loss.

In the third group, the supply opening of the duct is divided into several divisions by suitable flow-rectifying elements disposed in the duct and each division is provided with the above-described inclined rear wall structure or flow-resisting means. Although an appreciable extent of mass flow rate variation decrease can be obtained by this mechanism. it requires a great deal of power loss for activating the flow currency.

In case of the fourth group, a main duct is provided with a plurality of branch ducts of similar diameter arranged in order along the'length of the main duct and the branch ducts are provided with respective flow resistants having different flow resistance. The branch ducts are connected to a single supply opening. Because of the presence of the flow resistants, this system also requires a great deal of power loss for activating the flow currency.

A modification ofthis attempt includes a main duct having a plurality of branch ducts of different diameters arranged in order along the length of the main duct with elimination of the flow resistant. This system is also accompanied with the drawback the same being with that possessed by the system of the fourth group although slightly mitigated because of the absence of the flow resistant.

The fifth group of the flow system includes an attachment longitudinally disposed in the duct in the vicinity of the supply opening and the wall of the attachment is provided with a plurality of perforations of a different cross-sectional area. In this case, it is difficult to obtain a continuous mass flow rate distribution along the longitudinal direction of the main duct.

A principal object of the present invention is to provide an improved mass flow rate equalizer which can eliminate all the drawbacks possessed by the conventional flow-equalizing system ofa duct.

Another object of the present invention is to provide a mass flow rate equalizer of simple structure which can bring about an efficient and desirable equalization of flow passing through supply or exhaust openings ofa duct.

In order to attain the above-described objects, the mass flow rate equalizer of the present invention comprises one or more flow guide vanes. The flow guide vane is disposed within the duct in the vicinity of the opening in an inclined relationship with respect to the advancing direction of the flow. The flow guide vane is provided with at least one cutoff of a particular profile and the extent of the flow-passable opening formed by the cutoff of the flow guide vane substantially decreases gradually along the advancing direction of the flow processed therethrough.

In case of such a flow guide vane, the particular profile of the cutoff plays an important role in the equalization of the mass flow rate and the particular profile is formed by a particularly designed curvature of the side edges of the flow guide vane. However, provision of such a particularly designed curvature to the vane side edges requires a highly skilled, difficult and complex technique in its design, calculation and actual manufacturing.

For the purpose of mitigating this difficulty while surviving the advantage of the flow guide vane of the above-described type, a flow guide vane having straight side edges for defining the cutoff can be employed as a substitute. This modified flow guide vane may further be provided with one or more perforations formed therethrough into a lateral direction thereof.

Because of the presence of such lateral perforations, loss in functional advantage caused by elimination of curvature can be compensated to an appreciable extent.

The flow guide vanes of the above-described types can be installed within the duct in the vicinity of the supply or exhaust opening in a mutually three-dimensional relationship, that is in a cubic arrangement. In case the duct is divided into several 7 sections by suitable flow-rectifying elements, each section can be provided with such flow guide vanes of a cubic arrangement.

A further modification of the mass flow rate equalizer of the present invention is given in the form ofa flow guide cylinder disposed longitudinally within the main duct adjacent to the supply or exhaust openings. The effective inside diameter of the cylinder changes gradually along the advancing direction of the flow and the cylinder is provided with a plurality of peripheral perforations formed in order along the longitudinal direction of the cylinder. Effective cross-sectional area of the perforations decreases one by one along the advancing direction of the flow. Because of the combination of the change in the cylinders diameter with decrease in the perforations cross-sectional area along the advancing direction of the flow, discontinuous effect given by the latter can be compensated by continuous effect given by the former.

Further features and advantages of the art of the present invention will be apparent from the ensuing description, reference being made to the accompanying drawings, wherein FIGS. 1A to 1C are perspective views of several embodiments of the flow guide vane of the present invention,

FIG. 2 is a partly sectional side view of a supply opening of a duct with disposition of the flow guide vane of the present invention,

FIGS. 3A to 3C are sectional plan views, with omission of overhead slits, of the supply opening of the duct with disposition of the flow guide vanes shown in FIGS. 1A to IC, respectively,

FIGS. 4A and 4B are perspective views of several modified embodiments of the flow guide vane shown in FIG. 18,

FIG. Sis a partly sectional side view ofa supply opening of a duct with disposition of the flow guide vane shown in FIGS. 4A and 4B.

FIGS. 6A and 6B are sectional plan views. with omission of overhead slits, of the supply opening of the duct with disposition of the flow guide vanes shown in FIGS. 4A and 4B according to the present invention,

FIGS. 7A and 7B are explanatory side and plan views of a supply opening'terminal of a circular slit type for distributing the flow into the surroundings and provided with the flow guide vanes of the present invention,

FIGS. 8A to SF are explanatory plan views of various types of the opening terminal of the duct having the flow guide vane or vanes of the present invention,

FIG. 9A is a partly sectional side view of a flow guide cylinder disposed in a supply opening of the duct according to the present invention,

FIG. 9B is a cross section taken along a line 9B9B in FIG. 9A,

FIG. is a cross-sectional representation of a modified embodiment of the flow guide cylinder shown in FIGS. 9A and 98.

Referring to FIGS. 1A to IC, several embodiments ofa flow guide vane of the present invention are shown. In the embodiment shown in FIG. 1A, the flow guide vane 1 of the present invention is provided with a middle cutoff 2 defined by convexly curved edges 3 whereas, in the embodiment shown in FIG. 1B, the flow guide vane 1 is provided with two side cutoffs 6 and 7 defined by the convexly curved edges 3. The flow guide vane 1 may be provided with one side cutoff 8 defined by one convexly curved edge 3 as shown in FIG. 1C. Although the flow guide vane l is provided with convexly curved side edge or edges in the above-described embodiment, the convex curvature may be replaced by a concave curvature in accordance with the requirements for practical use.

Referring to FIG. 2, disposition of the flow guide vane of the present invention in the duct is illustrated. In the vicinity of slits 9 of a supply opening 11, the flow guide vane l of the present invention is disposed in an inclined relationship with respect to an advancing direction of the flow to be processed. The flow supplied from a given supply source through a duct 12 is conducted toward the slits 9 passing through an opening or openings defined by the flow guide vane 1 and the inside walls of the supply opening 11 of the duct 12 as shown with arrows in the drawing. Passing through the slits 9, the flow is supplied into the surroundings for which the supply opening 11 of the duct 12 is directed.

Relation between the advancing direction of the processed flow and the disposition of the flow guide vane I is shown in FIGS. 3A to 3C. In the case of FIG. 3A, the flow guide vane 1 shown in FIG. 1A is disposed in the supply opening 11 of the duct 12 in such a manner that the extent of the total flowpassable opening 13 defined by the side edges 3 and 4 of the flow guide vane 1 decrease along the advancing direction of the flow designated by an arrow 14 in the drawing. In the embodiment shown in FIG. 3B, the flow guide vane 1 shown in FIG. 1B is used and the extent of the total flow-passable opening 13 defined by the side edges 3 and 4 of the flow guide vane l and the inside walls of the duct 12 decreases in a same way. This is also the same in the case of the embodiment shown in FIG. 3C, wherein the flow guide vane 1 shown in FIG. 1C is adopted.

Through all the shown embodiments, it is a fundamental requirement to dispose the flow guide vane within the supply opening of the duct in such a manner that the extent of the resulting total flow-passable opening should decrease along the advancing direction of the processed flow.

Therefore, in case the shown flow guide vanes are used for an exhaust opening of a duct, they should be disposed therein in an arrangement opposite to those shown in FIGS. 3A to 3C.

Because of the above-described characteristic structure and arrangement of the flow guide vane of the present invention, the most effective mass-flow-rate-equalizing effect can be acquired with minimum pressure and power loss due to minimum flow resistance thereof.

Degree of inclination of the flow guide vanes disposition and the selection of the flow guide vanes edge line or lines are decided in relation to the dimensions of the slits, aspect ratio, mass flow rate and induction ratio Further, it was confirmed through repeated experiments by the inventor of the present invention, that the flow resistance caused by the disposition of the flow guide vane of the present invention is negligibly small from the view point of actual utilization thereof.

Although, the above-described flow guide vane having curved edges can present a considerably enhanced mass-flowrate-equalizing effect, design calculation of the curvature to be bestowed to the edges and the manufacturing thereof sometimes require a relatively complex procedure. On the other hand, there sometimes is a case wherein a not so accurate mass-flow-rate-equalizing effect is required. In order to obviate the above-described complicated design calculation and manufacturing, several substitutes for the flow guide vanes shown in FIGS. 1A to 1C are also proposed by the inventor of the present invention. Referring to FIG. 4A, an embodiment of such a modified flow guide vane is illustrated. In this embodiment, the flow guide vane 16 is provided with a substantially triangular profile and straight edges 17. Still another modified embodiment of the flow guide vane of this type is shown in FIG. 4B, wherein the flow guide vane 16 is provided with a plurality of lateral perforations 18. Because of the presence of such lateral perforations 18, loss in the functional advantage caused by substitution of the curved edges by the straight edges can be compensated to an appreciable extent. In case this technique is applied to the embodiment shown in FIG. 1A, the cured edges 3 should be substituted by straight edges.

Disposition of the flow guide vane 16 of the abovedescribed types is shown in FIGS. 5, 6A and 68, wherein the flow guide vane 16 disposed at the rear of the slit 9 of the supply opening 11 of the duct 12 in a manner the same as that shown in FIGS. 3A to 3C and the flow advances as shown with the arrow 14. So, in case the flow guide vane 16 is to disposed to an exhaust opening, it should be disposed in a reverse manner as already described. Further, when it is necessary or more advantageous, the flow guide vane 16 of this type may also be disposed with adequate inclination to the advancing direction of the processed flow as in the case shown in FIG. 2.

In case the flowing system is purposed for, for example, airconditioning of rooms, the supply or exhaust opening of the flow duct sometime hangs down from the ceiling of the room and, in this case, the opening terminal of the duct is provided with a plurality of slits encircling a central longitudinal line of the duct with a spaced relationship. This opening terminal of the duct may be usually divided into several sections by a plu rality of partitions radially extending from a central support. The flow guide vane of the present invention can also be applied to the opening terminal of the type with a favorable mass-flow-rate-equalizing effect.

Provided that the flow guide vane of the type shown in FIG. 1A is employed in a supply opening terminal of the abovedescribed type, the flow guide vane should be disposed therein in such a manner that the total area of the flowpassable opening will decrease gradually along the advancing direction of the processed flow.

Referring to FIGS. 7A and 78, an example of the disposition of the flow guide vane shown in FIG. 1A to a supply opening terminal of the above-described type is shown. In this example, the supply opening 11 is divided into six sections by six partitions l9 radially extending from a central longitudinal support 21 to a peripheral wall of the supply opening 11. Each section is provided with one or more slits 9 formed through the peripheral wall thereof and for passing the processed flow. The flow guide vane 1 shown in FIG. 1A is disposed in each section with a given inclination with respect to the advancing direction of the processed flow designated with an arrow 22 as shown in FIG. 7A in such a manner that the total area of the flow-passable opening 13 (see FIG. 3A) should decrease along the advancing direction of the processed flow. If the supply opening terminal 11 so arranged that it rotates around the central longitudinal support 21, the flow can be distributed into the surroundings in a uniform condition. In case the flow guide vane is used for an exhaust opening terminal, the disposition of the flow guide vane should be opposite to that shown in the drawings.

Referring to FIGS. 8A to SF, various types of opening terminals of ducts provided with the flow guide vane or vanes of the present invention are shown. In the drawings, the flow guide vanes are shaded for the purpose of clear understanding.

Although, in the foregoing embodiments, the mass flow rate equalizers are all given in the form of a vane, a cylindrical-type flow guide member can also be adopted as the mass flow rate equalizer of the present invention.

Referring to FIGS. 9A and 98, an embodiment of such a cylindrical-type flow guide member is shown. In this embodiment, a flow guide cylinder 23 is disposed longitudinally within the main duct 12 in the vicinity of a supply opening 11 and the effective inside diameter of the cylinder converges gradually toward the terminating end 12a of the main duct 12. The flow guide cylinder 23 is provided with a plurality of peripheral perforations 26 formed in order along the longitudinal direction thereof directing towards the slits 9 of the supply opening 11. Effective cross-sectional areas of the perforations decrease one by one along the advancing direction of the processed flow. For example, with the perforations disposed as shown in FIG. 9A, the direction of airflow would be as indicated by arrow 24. Because of the combination of the gradual divergence in the cylinders diameter with one-byone decrease in the perforations cross-sectional area along the advancing direction of the processed flow, the discontinu ous effect given by the latter can be compensated for by continuous effect of the former. A modification of the embodiment shown in FIGS. 9A and 9B is shown in FIG. 10, wherein the opening terminal 11 of a duct is provided with a quadrant cross section. Accordingly, the flow guide member is also provided with a quadrant cross section. The dimension of the lateral perforations is decided in a manner already explained. In the selection of the lateral perforations profile, not only circular but also any kind of profile can be adopted so far as the effective cross-sectional area thereof decreases one by one along the advancing direction of the processed flow.

What we claim is:

1. In a duct having exhaust and intake openings, means defining a plurality of slits in one side portion of said duct at one of aid openings, and flow-equalizing means disposed within said duct at said one opening, an improvement wherein said equalizing means comprises a first flow guide vane disposed adjacent said slits at one end of said one opening nearest the other opening and extending angularly and longitudinally away from said slits toward an end of said opening opposed to said one end, said vane having tapered edge means along its angular extent for providing a flow passage of decreasing cross section in the direction of an advance of flow through said duct.

2. A duct having improved equalizing means as set forth in claim 1, in which said tapered edge means defines a convex curve.

3. A duct having improved equalizing means as set for in claim 1, in which said tapered edge means defines a concave curve.

4. A duct having improved equalizing means as set forth in claim 1, in which said flow guide vane defines an isosceles triangle having its vertex disposed adjacent said slits, and in which said tapered edge means are defined by the equal length sides of said flow guide vane, said flow guide vane having a plurality of transverse perforations therethrough.

5. A duct having improved equalizing means as set forth in claim 1, further comprising means defining a plurality of slits at other side portions of said duct, said other side portions being spaced around said duct from said one side portion, and in which said flow-equalizing means comprises a plurality of said flow guide vanes having the same relationship, respectively, to said plurality of slits at said other side portions of said duct as the relationship of said first vane to said first plurality of slits.

6. In a duct having exhaust and intake openings, means defining a plurality of slits in said duct at one of said openings, and flow-rate-equalizing means disposed within said duct at said one opening, an improvement wherein said equalizing means comprises flow guide means having sidewalls defining a hollow central portion which increases in cross-sectional area in a direction along said duct toward the other of said openings, and defining a plurality of perforations directed toward said one opening and having decreased cross-sectional areas in the direction ofan advance of flow through said duct.

Claims

1. In a duct having exhaust and intake openings, means defining a plurality of slits in one side portion of said duct at one of said openings, and flow-equalizing means disposed within said duct at said one opening, an improvement wherein said equalizing means comprises a first flow guide vane dispOsed adjacent said slits at one end of said one opening nearest the other opening and extending angularly and longitudinally away from said slits toward an end of said opening opposed to said one end, said vane having tapered edge means along its angular extent for providing a flow passage of decreasing cross section in the direction of an advance of flow through said duct.

6. In a duct having exhaust and intake openings, means defining a plurality of slits in said duct at one of said openings, and flow-rate-equalizing means disposed within said duct at said one opening, an improvement wherein said equalizing means comprises flow guide means having sidewalls defining a hollow central portion which increases in cross-sectional area in a direction along said duct toward the other of said openings, and defining a plurality of perforations directed toward said one opening and having decreased cross-sectional areas in the direction of an advance of flow through said duct.