US2316764A - Fluid system - Google Patents

Description

FLUID SYSTEM Filed July 5, 1940 s Sheets-Sheet 1 & 3

ATTORNEY.

April 20, 1943.

R. M. HARDGROVE FLUID SYS TEM Filed July 5, 1940 5 Sheets-Sheet 2 INVENTOR. BY Ea/p/v M Hardgrove ATTORNEY.

April 20, 1943. R. M. HARDGROVE 2,316,764

FLUID SYS TEM Filed July 5, 1940 5 Sheets-Sheet 3 INVENTOR.

BY 0/ 0/17 M Hardy/ave ATTORNEY.

R. M. HARDGROVE April 20, 1943.

FLUID S YS T EM Filed July 3, 1940 5 Sheets-Sheet 4 INVENTOR. Zea lpfz MHardgroz e Y Wmmq ATTORNEY.

April 1943. R. M. HARDGROVE 2,316,764

SSSSSSSSS EM INVENTOR BY Kcz/ h MHarclgrm e Wmw ATTORNEY.

at high pressures.

Patented Apr. 20, 1943 FLUID SYSTEM Ralph M. Hardgrove, Westfield, N.

The Babcock & Wilcox Company,

J assignor to Newark,

N. J a corporation of New Jersey Application July 3, 1940, Serial No. 343,725

20 Claims.

The invention herein disclosed relates to boilers and their operation, embracing for example a type of boiler wherein the flow of water or other liquid from which vapor is generated is maintained by natural circulation. In general such a boiler may include a system of heated upflow passages in which vapor is generated and from which vapor and unvaporized liquid are discharged into one or more upper drums, th vapor and liquid being separated and the liquid returned to the lower ends of the upflow passages through downflow passages, the column of liquid in the downflow passage establishing a hydraulic head which promotes and maintains a natural circulation of fluid in the boiler.

The demand for high steaming capacities and lrigh boiler pressures has introduced various problems relating to th safety and efficiency of the units, among which are certain problems involving circulation which it is an object of this invention to overcome.

In a boiler employing natural circulation, it is essential that the fluid flow passages in both the upflow and downflow portions of the circuit be so proportioned that under the most severe normal operating conditions, the hydraulic head differential between the columns of fluid in these two sets of passages will be such as to overcome the resistances to fiow and set up an adequate flow of fluid so that the heat transfer surfaces will be maintained at proper temperatures. This is of particular importance when the boiler is operated at high rates of heat absorption, and of more importance when the boiler is operated At elevated pressures, the high temperature of the boiler liquid reduces the margin of safety between the temperature at which the metallic heat transfer parts must op erate and th temperatur at which such parts would become overheated.

With higher operating pressures, the circulatory conditions are afiected, since the properties of the liquid from which the vapor is generated are such that the density of the vapor increases with pressure and the density of the liquid decreases until at some critical pressure the densities of the liquid and its vapor are the same; in the case of water, which is the liquid used in the majority of vapor generators, the density of the steam equals the density of the water at a critical pressure of approximately 3200 lbs. per square inch. Such a relation of densities is particularly pertinent to the design of natural circulation boilers which derive their circulating flow from the head difierential which is a function of the difference in density between the water in the downflow passage and the water-steam mixture in the upflow passage.

In the construction of a high capacity and high pressure boiler of the type under discussion, it is therefore essential that resistances and impedances to flow which use up an appreciable portion of the available hydraulic head that might otherwise be available for inducing and maintaining an active circulation and flow of liquid to the heat absorbing surfaces, be avoided or held to a minimum. In this respect, it is advantageous to use downcomers of large flow area from the elevated steam and Water drum, and to locate the downcomers in unheated positions.

- It has been found that with cylindrical downcomers of large diameter, particularly when connected to the end portions .of the drum whereby an appreciable approach velocity occurs, a condition is provided which is conducive to vortex formation in the moving liquid at the entrance end of the downcomer. Such a vortical flow reduces the effective hydraulic head of the downflow water column and may be still further detrimental to good circulating conditions by causing the entrainment of vapor in the downflow water stream.

Inhibition of a vortex therefore, eliminates a factor which contributes towards a reduction in the rate of boiler circulation. While it is important to prevent vortex formation in connection with a boiler at all operating pressures, the importance is emphasized particularly with reference to an upper operating range, for example, from about 1500 lbs. per square inch to 2500 lbs. per square inch. For such pressures, Water at saturated temperatures of 597 F. and 869 F. respectively, has specific weights of 42.5 lbs. per cubic foot and 34.7 lbs. per cubic foot, while the steam has specific weights of 3.66 lbs. per cubic foot and 7.73 lbs. per cubic foot.

The solution of this problem has entailed the development of certain devices which for convenience of identification are known as vortex inhibitors, their purpose being to prevent the formation of a vortex and thereby permit the maintenance of a high rate of natural circulation.

An object of the invention is therefore to utilize to the fullest extent the available hydraulic head in a natural circulation boiler operating at high capacities or high pressures, or at high capacities and high pressures.

A further object is to improve the characteristics of fluid flow in a natural circulation'boiler, particularly to and through the return flow passages.

An additional object is to improve the flow conditions within an elevated boiler drum from which liquid is returned through a downcomer connection; also to inhibit or entirely prevent the formation of a vortex within such a drum at the entrance to such a connection.

The invention also contemplates the arrangement of specific devices within a boiler drum whereby the foregoing objects may be accomplished, such devices having a direct action on the fiow of liquid into the downcomer passage to prevent the formation of .a vortex and consequent impairment of boiler circulation.

These and other objects and features of the invention are more fully set forth in the ensuing detailed description and claims, particularly when read in conjunction with the accompanying drawings, of which the several figures are briefly described as follows:

Fig. 1 is a sectional side elevation indicating a .type of boiler favorable to utilization of the invention;

Fig. 2 is .a sectional elevation of the boiler taken along line 2-2 of Fig, 1;

Fig. 3 is a partial section taken along line 3-3 of Fig. 1 indicating in plan a form of vortex inhibitor in operative position within the boiler drum;

Fig. 4 is a side elevation partly in section of the structure shown in Fig. 3;

Fig. 5 is an end section taken along line 5-5 of Fig. 4;

Fig. 6 is a partial section similar to Fig. 3 showing a modification;

Fig. 7 is a partial section similar to Fig. 3 showing a second modification;

Fig. 8 is a side elevation partly in section of the structure shown in Fig. 7

Fig. 9 is an end section taken along line 99 of Fig. 8; r

Fig. 10 is an end section similar to Fig. 9 showing a third modification;

Fig. 11 is a side elevation partly in section showing a fourth modification;

Fig. 12 is a fragmentary projection along line l2--I2 of Fig. 11;

Fig. 13 is an end section taken along line |3--I3 of Fig. 11;

Fig. 14 is a side elevation partly in section showing a fifth modification;

Fig. 15 is a fragmentary projection along line l5-i-5 of Fig. 14;

Fig. 16 is a fragmentary projection along line i5l5 of Fig. 14.

The boiler indicated in Figs. 1 and 2 of the drawings is a boiler of the natural circulation type capable of generating vapor at high rates and at high pressures and temperatures; for example, such a boiler may have steaming capacities of several hundred thousand pounds of steamper hour, and operate at a gauge pressure of approximately 2500 lbs. per square inch and a corresponding saturation temperature of approximately 669 F. Such'a boiler, together with its furnace and other related parts is included in the subject matter of U. S. Patent 2,231,872 grantedFebruary '18, 1941, formerly application Ser. No. 137,196 filed on April 16, 1937, as the joint application of E. G. Bailey and others. It is to be understood that the boiler illustrated and described herein is'broadly representative of the type of boiler in which the subject invention may be utilized, and that its specific characteristics, such as the form and arrangement of its component parts, may be variously modified.

The boiler as shown comprises a plurality of groups of steam generating tubes which with their connections constitute the upfiow section of a natural circulation system having connections with the water supply header 2!] at its lower end and with the steam and water drum 2| at its upper end. The downfiow section comprises the downcomer pipes 22 connecting the ends of drum 2| with the ends of the header 20. One or more feed water connections such as 23 are made to the drum 2| at suitable locations for replacing water evaporated from the system and for maintaining a normal operating level of water within the drum between predetermined limits. In the drawings, the level of liquid is indicated at approximately the horizontal center line, but certain conditions might make it desirable to maintain a level either below or above the center line position. The necessary heat for vapor generation is supplied by a two stage furnace having a primary stage A which is fired by suitable burners B, and a secondary stageC which receives hot products of combustion from the primary stage. The heating gases pass from the secondary stage C to a convection passage D and finally leave the setting through gas outlet E.

The vapor generating elements of the boiler comprise a plurality of groups of tubes which in the main define the primary and secondary stages A and C of the furnace and thus are subjected to intense heat of radiation from the burning fuel and products of combustion. The tubes associated with the passage D are heated mainly by convection, being exposed to combustion gases which have been cooled in their passage through the preceding two stages of the furnace.

The tubes associated with the primary stage A include the floor tubes 24 which are connected at their lower ends to the water supply header 20, the front wall tubes 25 which are connected to floor tubes 24 by means of the intermediate header 26, and the side wall tubes 21 which are connected at their lower ends to side wall headers 28. The tubes 25 and 21 are connected at their upper ends to headers 29 and 30 respectively, the headers 30 being suitably connected to the drum 2! through riser tubes 3|.

The tubes associated with the secondary stage C include the rear wall tubes 32 which extend upwardly from header 33 to the drum 2 I, and side wall tubes 34 which extend upwardly from lower side wall headers 35 to upper side wall headers 35, the latter having suitable connections 3''! also to the drum 2 I.

Water or other liquid for vapor generation is distributed from header 2!] to the lower side wall headers 28 and 35, and to the rear wall header 33, through connections 38, 39 and 40, respectively.

A division wall 4| between the two furnace stages is formed of tubes 42 which extend upwardly from header 20 to header 29 and have I portions 43 within the furnace arranged to provide outlets 44 for products of combustion passing from the primary to the secondary stage.

The tubes associated with the convection passage D include the bank of tubes 45 extending upwardly from header 29 to the upper drum 2| and transversely of the flow of heating gases. Additional tubes 46 which extend from header 29 to the drum 2| have their end portions arranged along the walls 41 and 48 of the passage D and their intermediate portions 49 arranged across the passage in transverse relation to gas flow. Other heating surface associated with the passage D includes a superheater 50 and an economizer In the arrangement shown and described, all tubes forming the upfiow section of the system derive their total supply of liquid either directly or indirectly, from a lower header such as 20, and all tubes discharge their total content of heated liquid, or liquid and vapor mixed, into a common upper drum such as 2|. The individual connections from the upflow section to the drum 2| are made at successive longitudinal positions, as shown in Fig. 2 for tubes 32 and 31, occupying the major central portion of the drum length and leaving the end regions for connection of the downcomers 22 which are disposed exteriorly of the setting walls 52 and thereby shielded from heat of the furnace.

The downcomers 22 as shown are circular conduits of relatively large internal diameter to provide adequate flow area for the total quantity of liquid which must be returned to the lower part of the upfiow section at a high rate to maintain the desired high rate of vapor generation. The flow area provided by any downcomer is greater than the flow area of any tube discharging into the drum, but for practical considerations the total downfiow area is only a fraction of the combined flow area of all such discharging tubes. The total flow area afforded by the downcomers may also represent only a fraction of the transverse cross section of the normal liquid content of the drum. It is desirable for economic reasons to keep the diameters of drums and downcomers down, where it can be done without involving undue limitations to other factors of the unit. The location of such downcomers relative to the entrances for liquid into drum 2| throughout its central portion requires that the liquid attain a high velocity of flow longitudinally of the drum in its approach to the downcomer, and an accelerated velocity as the direction of flow is changed and the liquid enters the downcomers; furthermore, such conditions are conducive to the formation of a vortex in the body of liquid above and within the downcomer. Thus, there is a twofold effect on the amount of hydraulic head available for maintaining circulation, first a loss due to the acceleration of velocity at the entrance, and second, a further loss due to the formation of the vortex. The vortex under certain conditions may be hollow and penetrate to a considerable distance below the upper surface of the liquid within the drum, and in some instances may actually extend within the downcomer; in such cases the eifect of the vortex is accentuated and entails a further loss in hydraulic head due to the presence of vapor or gas which reduces the density of the descending column of liquid.

The conditions described have led to the development of certain devices known as vortex inhibitors which, as shown in the copending applications of E. G. Bailey, Serial No. 343,707, filed July 3, 1940, and H. J. Kerr, Serial No. 343,715.

filed July 3, 1940, both of which applications are assigned to the assignee of the present invention, are incorporated in the circulatory system of a boiler for counteracting and preventing vortical action of the fluid in the downfiow section. Figs. 3 to 16 inclusive of the present application illustrate further developments in connection with this same general problem, each specific embodiment being shown in association with a downcomer from a boiler drum for inhibiting vortical action in the descending column of fluid. In general, such devices divide the body of circulating liquid into a plurality of streams and direct the flow of individual streams toward the downcomer connection.

In Figs. 3, 4 and 5 a form of vortex inhibitor is shown which comprises a plurality of spaced plates 53, 54, having portions of cylindrical curvature providing a nested arrangement of arches 56, 51, 58 of successively different heights and spans. The outer arch 56 and the intermediate arch 51 are indicated as being of the pointed or Gothic type having crowns at 59 and 60 respectively, while the inner arch 58 is represented as being of the rounded type having a Such plates may have their arched portions formed as arcs of circles, and

the arcuate portions of adjacent arches arranged concentrically as shown for the pointed arches 59,

60. Separate passages 62, 63 are thereby formed between adjacent plates and additional separate passages 64, 65 are formed within the inner arch 58 by means of spaced plates 66 which terminate .at their rearward edges adjacent the rounded crown 6|.

The plates are preferably arranged in an upright position and for the embodiment shown, may be vertically disposed and may have their lower edges 61 made to conform to the contour of the inner wall of the drum 2| with which they may contact except where the plates traverse the outlet opening 68 within which the downcomer 22 is received; their upper edges 59 being disposed in substantially horizontal alignment at a predetermined distance below the center line of the drum. Moreover, the plates may be symmetrically arranged relative to a plane common to the longitudinal axis of the drum 2| and to the central axis of the downfiow conduit 22, and may have their forward or leading edge portions H! in alignment in a vertical plane extending transversely of the drum, as shown. The plates may be held in the required relative positions by means of reinforcing bars H, 12 and the entire assembly conveniently held in position relative to the downcomer by attachment of the outer arch plates to clips 13 which are welded or otherwise fixed to the drum.

The device is preferably entirely submerged in the circulating boiler liquid at all normal operating levels, the liquid entering the passages 62, 63, 64, 65 between the spaced leading edges 10 of the plates and also from above between the spaced upper edges 69, the plates dividing the flowing body of liquid into a plurality of sep-' arate streams and localizing the delivery of such streams to separate flow area units of the down corner 22. The outermost arch 56 may extend a sufficient distance downstream to include the rounded periphery of the outlet opening 68 and provide at that location a substantial barrier to continued horizontal flow of liquid beyond the entrance to the downfiow passage provided by conduit 22.

It will be noted particularly from the plan view Fig. 3 that the plates 53, 54, 55 and S6, in their symmetrical formation and arrangement relative to the longitudinal axis of the drum, provide passages 62, 63 and 64 at opposite sides of the axis, each passage at one side being equal in flow area to the correspondingly positioned passage at the opposite side and thus accommodating the same proportionate division of the total flow of liquid as is accommodated by at least one other passage. With plates 54, 55 and 66 tra versing the outlet opening 68 .as shown, there are provided a plurality of divisional outlet areas I62," I63, I64, and I65 of which the areas I62, I63 and I64, respectively, form substantially equal proportionate divisions of the total outlet area for the discharge of liquid from passages of equal flow capacities; the larger areas I62 and I63 accommodating the flow from pairs of passages 62 and 63, respectively, and the areas I54 accommodating the flow from a pair of passages 64; the area I65 serving as the outlet from a single centrally disposed passage 65.

Figs. 3 and 4 also show a form of water column connection I4 suitable for flow conditions within drum 2|. In certain constructions the connec tion below the liquid level may extend inwardly of the drum, and the liquid flowing past the inner end of such a connection at high velocity may affect the reliability of level indication presumably due to a local deflection or eddying of the liquid at the orifice. Therefore, in order to provide consistent and accurate indications of level, irrespective of flow velocity which may vary, the connecting indicator tube 15 is made to extend inwardly of the drum wall in a horizontal direction and is provided at its inner end with a plate or disc I6 having its inner planar surface I1 flush with the perimeter of the orifice I8 and substan- .tially parallel to the longitudinal axis of the drum and to the generally longitudinal direction of flow toward the downcomer 22. As a result, the velocity factor due to longitudinal flow of liquid past the orifice is substantially eliminated and amore reliable indication due to static head is obtained. The indicator tube I5 opens into the drum 2| at a location suitably in advance of the inhibitor device to provide an effective correction due to the disc. The tube may be protected and supported by a surrounding'tube I9 which has a fluid-tight connection with thedrum wall. This form of connection is also applicable to other devices such as feed-water regulators which depend on reliable indications of level for satisfactory operation.

Fig. 6 is representative of a modification in which the nested arches 80, 8|, 82 are of the rounded type and concentrically arranged. The plates 63, 84, 35 forming such arches, and the additional spaced plates 86 are shown as being extended in parallel relation forwardly of the center of curvature of the arches, the plates terminating in spaced leading edges 87 which may be vertically disposed and in alignment transversely of the drum 2 I. As in the case of the previously described embodiment, the plates may be held in proper relation by reinforcing bars 88, 89, and the entire assembly fixed in relation to the downcomer 22 by suitable attachments such as clips.

The embodiment illustrated in Figs. '7, 8 and 9 utilizes flat, upright plates 9 I, arranged in parallel longitudinally of the drum 2| and across the outlet opening 68, the plates extending upwardly within the drum to a predetermined level below the horizontal center line. A central plate 92 may have its lower edge 93 in contact with the drum wall, while other plates at opposite sides have lower edges 94 spaced from the wall to provide substantial equalization of fiow of liquid into the downcomer from different passages. A back plate 95 extends transversely of the plates 9|, 92 at the marginal limit of discharge opening 68, and may be suitably secured to the plates to substantially impede the flow of circulating boiler liquid into the drum space beyond the downto streamline the flow of the comer connection and thereby direct a greater proportion" of the liquid into the downflow passage. The back plate is preferably segmental in form, the upper edge portion 96 being substantially straight and horizontal in its assembled position within the drum, and the lower edge portion 91 being arcuate and spaced from the inner wall of the drum about as shown. A bar 98fmay be provided across the upper edges of the plates for reinforcement and the assembled unit held in position within the drum by a suitable arrangement of clip fastenings 99.

Fig. 10 illustrates a device similar to that shown in Figs. 8, 9 and 10 except that the spaced plates which extend longitudinally of the drum include plates I 00 which are inclined to the vertical, the plates at opposite sides of the longitudinal axis of symmetry converging downwardly toward the entrance to downcomer 22. The central plate 92 may contact the drum wall, while the symmetrically disposed side plates I 00-may have lower edge portions IOI spaced from'the drum wall, as shown.

In the foregoing embodiments, the outlet for boiler liquid has been illustrated and described for convenience as located in a cylindrical wall portion of the drum and having its axis of flow vertically disposed and intersecting the horizontal axis. It is to be understood, however, that variations of this relation are permissible and that other directions of discharge may be utilized while preserving the function .of the flow-directing device as an inhibitor of disturbances in the circulating liquid.

Figs. 11 to 16 inclusive, for example, illustrate modifications wherein the aXis of the outlet connection I92 is oblique to the horizontal axis of the drum I03 and extends downwardly from a lower portion of the spherical drum head I04. Again for convenience and simplicity of disclosure, the axis of the downcomer and the horizontal axis of the drum are indicated as being in the same vertical plane.

In Figs. 11, 12, 13 the vortex inhibitor is generally of the type shown in Fig. 3, utilizing a series of nested arches I05, I 06 of the Gothic or pointed type with plates I01, I08 extended in spaced relation forwardly of the outlet passage I09 and terminating in edge portions IIO, III which are substantially vertical and in alignment transversely of the drum. In this embodiment, the arch plates have portions of cylindrical curvature about parallel axes and meet at crowns H2, H3 in parallel lines disposed at a greater angle to the longitudinal axis of thedrum than the outlet connection. The upperedges II4 of the arch plates I01, I08 terminate in a plane which is substantially normal to the plates and inclined to the horizontal. The unit may be removably fixed in position by attachment at suitable locations to clips H5, H6 secured to the drum, stiffener means such as bar I I I being provided as required. A plate I I8 conveniently shaped to the inner contour of the drum and flared into the outlet passage I09 may be included discharging liquid. Such a plate preferably overlies the cavity II9 which in certain constructions may result from a localized circumferential enlargement of the drum interior;

In Figs. 14, 15, 16 the inhibitor device includes a plurality of spaced plates I 20 arranged in an upright position and extending longitudinally of the drum I03 across the entrance to the inclined downcomer passage I09. A back plate I'2I of segmental form extends upwardly from adjacent the rearward margin of the downcomer passage 19 preferably in a direction more nearly vertical than the flow-axis of the downcomer passage. The plates I20 in the form shown are symmetrically arranged at opposite sides of the central axis of the drum and are more widely spaced at their leading edges I22 than at the junctures with the back plate I2! (Fig. 15), the plates furthermore being inclined upwardly from their lower edges to provide an increased spacing at their upper edges 123- (Fig. 16); thus providing passages 124 between successive plates of decreasing taper from the different directions in which the circulating liquid may enter such passages. The plates IZB may terminate in upper edges 123 lying in a common plane normal to the back plate I21, and in lower edges I25 in a common plane substantially normal to the central axis of the downcomer passage. A reinforcing bar H! and clips H5, H5 may be provided for support, and a curved plate H8 for the purpose of streamlining the flow of liquid into and through the device.

In this disclosure of the invention the description and illustrations have necessarily been restricted to certain selected embodiments but it is to be understood that the practical application of the invention may involve apparatus of different form and appearance, and that such variations in structure are fully included within the scope of the invention as defined in the appended claims.

, I claim:

1. In a fluid circulatory system, an elevated drum having closed ends horizontally spaced, said drum having inlet means for liquid intermediate said ends and means providing an outlet through which said liquid is discharged downwardly from a location adjacent one of said ends, said outlet being sufliciently large to permit liquid to be discharged therethrough under conditions conducive to a vortical disturbance within said drum, means for directing liquid into said outlet with minimum turbulence and loss of velocity head comprising means iorming passages having entrances for liquid arranged transversely of said drum in advance of said outlet, said passages having lower portions open toward difierent flow-area units of said outlet, and means for preventing longitudinal flow of liquid beyond the rearward margin of said outlet.

2. In combination, an elevated drum having inlet and outlet means for liquid at horizontally spaced locations, a conduit extending downwardly from said drum for conducting liquid discharged through said outlet means under conditions conducive to the formation of a vortex, and means for directing liquid into said conduit with minimum turbulence and loss of velocity head comprising upright plates defining horizontally extending fiow passages for liquid approaching said conduit from said inlet means, said passages having entrances arranged in side-by-side relation transversely of the approaching body of liquid and having opposite ends closed for preventing continued horizontal flow of liquid beyond said conduit, said passages having exits for liquid opening downwardly toward said conduit.

3. In a fluid heater, an elevated drum having its longitudinal axis horizontally disposed, said drum having a downcomer for liquid connected to an end region thereof, said downcomer having a flow capacity suflicient for the discharge of liquid from said drum at a rate contributing to vortical flow into said downcomer, said drum having inlet means for liquid connected to a region horizontally spaced from said end region, and means for directing liquid received through said inlet means toward and into said downcomer comprising upright plates defining horizontally extending flow passages having entrances [or liquid arranged transversely of the direction of flow of liquid toward said downcomer, said passages having exit portions communicating downwardly with said conduit, some of said passages having portionsremote from said entrances in mutual communication horizontally above the entrance to said conduit.

4. In combination with an elevated drum having horizontally spaced inlet and outlet means for liquid, a conduit extending downwardly from said outlet means for discharging liquid from said drum at a rate contributing to vortical movement of liquid flowing into said conduit, and means for directing liquid received through said inlet means toward and into said conduit. comprising spaced plates defining horizontally extending flow passages having entrances for liquid arranged transversely of the direction of flow of liquid toward said conduit, some of said plates having portions curved laterally to form an arch opposite the entrance to said conduit.

5. In combination with an elevated drum having horizontally spaced inlet and outlet means for liquid, a conduit extending downwardly from said outlet means for discharging liquid from said drum at a rate contributing to vortical movement of liquid flowing into said conduit, and means for, directing liquid received through said inlet means toward and into said conduit comprising spaced plates defining horizontally, extending flow passages having entrances for liquid arranged transversely of the direction of fiow of liquid toward said conduit, said plates having portions remote from said entrances forming arches in nested arrangement, at least one of said arches overlying the entrance to said conduit.

6. In combination with an elevated drum having horizontally spaced inlet and outlet means for liquid, a conduit extending downwardly from said outlet means for discharging liquid from said drum at a rate contributing to vortical movement of liquid flowing into said conduit, and means for directing liquid received through said inlet means toward and into said conduit comprising spaced plates defining horizontally extending flow passages having entrances for liquid arranged transversely of the direction of flow of liquid toward said conduit, said plates having portions remote from said entrances extended in nested arch formation, an interior arch traversing the entrance to said conduit and the exterior arch encompassing said entrance.

7. In combination with an elevated drum having horizontally spaced inlet and outlet means for liquid, a conduit extending downwardly from said outlet means for discharging liquid from said drum at a rate contributing to vortical movement of liquid flowing into said conduit, and means for directing liquid received through said inlet means toward and into said conduit comprising spaced plates defining horizontally extending flow passages having entrances for liquid arranged transversely of the direction of flow of liquid toward said conduit, said plates havingv portions remote from said entrances extended in nested arch formation, an interior arch traversing the entrance to said conduit, and the enclosing arch having its crown substantially at the downstream limit of said entrance.

8. In combination with a cylindrical boiler drum having its longitudinal axis horizontally disposed, said drum having inlet means for liquid at an intermediate location and outlet means for said liquid at an end location, said outlet means including a downcomer having an upper connection with said drum and having its axis of flow at said connection at an angle to the direction of flow of said liquid from said inlet means toward said outlet means, said outlet means being large enough to permit the discharge of liquid from,

said drum at a rate contributing to vortical flow into said downcomer, and means for preventing vortical movement of liquid entering said-downcomer comprising arched members mutually defining flow passages having exits for liquid directed toward said downcomer connection.

9. In combination with an elevated drum having horizontally-spaced inlet and outlet means for liquid, a downcomer extending downwardly from said outlet means, said outlet means and said downcomer each having sufiicient flow capacity for the discharge of liquid from said drum at a rate contributing to vortical flow into said downcomer, and means for directing liquid received through said inlet means toward and into said downcomer comprising spaced plates extending longitudinally of the directionof flow of said liquid and arranged edgewise of said outlet means whereby multiple paths are provided for liquid flowing toward and into said downcomer, said passages having entrances at an upstream location relative to said outlet means, and means forclosing said passages at the downstream limit of saidoutlet means.

' 10. In combination with an elevated drum having horizontally spaced inlet .and outlet means for liquid, a downcomer extending downwardly from said outlet means, said outlet means and said downcomer each having suflicient flow capacity for the discharge of liquid from said drum at a rate contributing to vortical flow intosaid downcomer, and means. for directing liquid received throughsaid inlet means toward and into said downcomer comprising spaced plates extending longitudinally of the direction of flow of said liquid and arranged 'edgewiseof said outlet means whereby multiple paths areprovided .for liquid.

flowing. toward and into said, downcomenisaid plates converging downwardly. toward the .entrance to said downcomer, said passages. having entrances at an upstream location relative tosaid outlet means, and means for closing the majority of saidpassages at the downstream limit of said outlet means.

11. In combination with a horizontally ;ex. tending cylindrical drum having horizontally spaced inlet and outlet openings for liquid, a downcomer extending downwardly from an outlet opening, said downcomer and the associated outlet opening each having suflicientflow capacity to conduct liquid from said drum at a rate contributing to vortical movement of said liquid, and

means for directing said liquid towardand into said downcomer comprising spaced plates ar ranged in an .upright position longitudinally within said drum to provide passages in multiple for liquid flowing toward and into said downcomer, said plates extending from an upstream location forwardly of said outlet opening to a 10- cation adjacent the downstream limit of said opening, said passages having lower portions opening downwardly. toward the interior of said downcomer, and a segmental back plate for closing said passages at theirdownstream end 12. In combination with a horizontally extending cylindrical drumhaving horizontallyspaced inlet and outlet openings for liquid, a downcomer extending downwardlyirom an outlet opening, said downcomer and the associated outlet opening each having sufiicient flow capacity to conduct liquid from said drum at a rate contributing to vortical movement of said liquid, and. means. for directing said liquid toward and intosaid .down-. comer comprising spaced plates. arranged in an upright position longitudinally withinsaid. drum to provide passages in multiple for liquid flowin toward and into said downcomer, said plates extending from an upstream. location forwardlyof said outlet opening to a location adjacent the. downstream limit of said opening, said plates having lower edge portions spaced from the in terior wall of said drum and said passages having lower portions. opening downwardly toward the interior of said downcomer, and a segmental back plate for closing said passages at their downstream ends.

13. In combination with a'horizontally extending cylindrical drum having horizontally spaced inlet and outlet openings for liquid, a downcomer extending downwardly from an outlet opening. said downcomer and the associated outlet opening each having sufficient flow capacity to conduct liquid from said drum at a rate contributing to vortical movement of said liquid, and means for directing said liquid toward and into said downcomer comprising spaced plates arranged in an upright position longitudinally within said drum to provide passages in multiple for liquid flowing toward and into said downcomer, said plates extending from an upstream location forwardly of said outlet opening to a location adjacent the downstream limit of said opening, said passages having lower portions opening downwardly toward the interior of said downcomer, and a segmental back plate for closing said passages at their downstream ends, said back plate having curved edge portions spaced from the interior wall of said drum. 7

14. In combination with a cylindrical boiler drum having its longitudinal axis horizontally disposed, said drum having inlet means for liquid at -an intermediate location and outlet means for said liquid at an end location, said outletmeans including a downcomer having an upper connection with said drum and having its axis of flow at said comiection at an angle to the direction of flow of said liquid fromsaid inletmeans toward said outlet means, said outlet means having sufficient flow capacity for the discharge of liquid from said drum at a rate contributing to the formation of a vortex, andmeans forpreventin'g vortical movement of liquid entering saiddoWn comer comprising spaced plates extending longitudinally of said drum and arranged upright across said outlet means, said plates having leading edge portions arranged forwardly of said outlet means and spaced at greater distancesthan succeeding portions of said plates, and a back plate contormingsubstantially to the inner contour of said drum for closing, said passages adjacent the rearward margin of said outlet means.

15. In combination with an elevated drum having horizontally spaced inletand outlet means for liquid, a downcomer extending downwardly from said outlet means, said outlet means and said downcomer each having s'uifici entflowcapacity for conductingliquid therethrough at a rate contributing. to the formation f a vortex,

and means for direc'ting li'quid received through I said inlet means toward and into said downcomer comprising spaced plates having adjacent end portions extending longitudinally of the direction of flow of said liquid and having portions arranged edgewise of said outlet means whereby multiple flow passages are provided for liquid flowing toward and into said downcomer, said passages having entrances between said adjacent end portions at an upstream location relative to the flow axis of said outlet means, and means for closing at least some of said passages at a location within the projected outline of said outlet means.

16. In combination with an elevated drum having horizontally spaced inlet and outlet means for liquid, a conduit extending downwardly from said outlet means, said outlet means and said conduit each having sufficient flow capacity for conducting liquid therethrough at a rate contributing to the formation of a vortex, and means for directing liquid received through said inlet means toward and into said conduit comprising spaced plates defining horizontally extending flow passages having entrances for liquid arranged transversely of the direction of flow of liquid toward said conduit, the majority of said plates having portions remote from said entrances forming arches in nested arrangement, at least one of said plates extending within an interior arch of said arrangement to form a plurality of said passages, said passages having exits for liquid directed toward said outlet means.

17. In a circulatory system for liquid, a horizontally disposed cylindrical drum having an outlet adjacent one end through which said liquid is discharged downwardly under conditions conducive to the formation of a vortex in said liquid in the vicinity of said outlet, and vortex inhibiting means within said drum comprising platelike elements arranged to divide said liquid into a plurality of streams and to form passages for multiple flow of said streams longitudinally of said drum and downwardly toward said outlet, certain of said streams constituting substantially equal proportionate divisions of the total flow of liquid, said plate-like elements having portions arranged upright in edgewise relation to said outlet inclusive of portions arched horizontally across said outlet for discharging streams constituting substantially equal proportionate divisions of said liquid through substantially equal proportionate divisions of the total outlet area.

18. In a fluid circulatory system, an elevated drum having closed ends horizontally spaced, said drum having inlet means for liquid intermediate said ends and means providing an outlet through which said liquid is discharged downwardly from a location adjacent one of said ends, said outlet being sufficiently large to permit liquid to be discharged therethrough under conditions conducive to a vortical disturbance within said drum, means for directing liquid into said outlet with minimum turbulence and loss of velocity head comprising means forming passages having entrances for liquid arranged transversely of said drum for dividing said liquid into a plurality of streams, said passages having lower portions open toward different flow area units of said outlet, the walls of said passages including longitudinally extending portions spaced transversely of said drum to define entrances to said passages, and including other portions at a downstream location arranged to prevent longitudinal flow of said streams beyond the rearward margin of said outlet.

19. In combination with an elevated drum having its longitudinal axis horizontally disposed, said drum having a submerged outlet for discharging liquid downwardly therefrom, said outlet having sufiicient flow capacity for the formation of a vortex in liquid entering said outlet from said drum, and means for inhibiting the formation of a vortex in said entering liquid comprising spaced plates arranged upright within said drum and extending longitudinally thereof in edgewise relation to said outlet whereby multiple paths are provided for liquid flowing toward and into said outlet, said plates being substantially flat throughout and having portions converging downwardly toward said outlet.

29. In combination with an elevated drum having its longitudinal axis horizontally disposed, said drum having a submerged outlet for discharging liquid downwardly therefrom, said outlet having sufficient flow capacity for the formation of a vortex in liquid entering said outlet from said drum, and means for inhibiting the formation of a vortex in said entering liquid comprising spaced plates arranged upright within said drum and extending longitudinally thereof in edgewise relation to said outlet whereby multiple paths are provided for liquid flowing toward and into said outlet, said plates being substantially flat throughout and having portions arranged obliquely to the central axes of said drum and outlet to form multiple flow paths tapering both horizontally and downwardly in the direction of said outlet.

RALPH M. HARDGROVE.

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