US2791406A

US2791406A - Fluid agitating devices

Info

Publication number: US2791406A
Application number: US518574A
Authority: US
Inventors: Robert L Bates
Original assignee: Chemineer Inc
Current assignee: National Oilwell Varco LP
Priority date: 1955-06-28
Filing date: 1955-06-28
Publication date: 1957-05-07
Anticipated expiration: 1974-05-07

Description

May 7, 1957 R. BATES FLUID AGITATING DEVICES 2 Sheets-Sheet 2 Filed June 28, 1955 FIG-6 FIG-5 FIG-7 FIG-IO INVEN TOR.

ROBERT L. BAT-ES ATTORNEYS United States 2,791,406 7 FLUID AGITATING DEVICES Robert L. Bates, Dayton, Ohio, assignor to Chemineer, Inc., Dayton, Ohio, a corporation of Shin Application June 28, 1955, Serial No. 518,574

(Claims. (Cl. 259-97) This application relates to agitating devices for liquid containing tanks, and particularly to such devices for use with tanks having one horizontal dimension considerably greater; than the other and presenting elongated generally rectangular configuration in horizontal cross-section.

Proper arrangement of a draft bend housing assembly about a propeller type agitator will develop a natural flow pattern in such tanks which provides maximum circulation with minimum power requirements. By utilizing a marine type propeller rather than a centrifugal impeller, high speed motor operation is possible, with attendant operating economies. Also, when operating against a negligible discharge head, the marine type propeller provides higher flow efiiciencies than other types of impellers. Furthermore, such a propeller produces a positive flow within the tank when used with this draft bend assembly, and in addition creates a zone of high turbulence within the. assembly which assures good mixing action when the agitator is used in applications involving the mixing of materials into the liquid contained within the tank.

In accordance with this invention the draft bend assembly has certain characteristics which provide sufficiently high linear velocity of the liquid in a horizontal direction as it. is moved by the propeller to give steady turbulence throughout the tank without surging, localized boiling, or other such undesired actions in the liquid. By minimizing frictional losses in the draft bend assembly, and by gradually constricting that assembly from inlet toward outlet, suflicient velocity is obtained in a horizontal direction to create this desired natural flow pattern. The design, of the draft bend is critical in the sense that a careful proportion of fiow capacity and discharge head must be produced to provide sufiicient velocity to control the full length of the vessel and yet have ample volumetric capacity to provide proper tank turnover. The higher velocity, while resulting in a somewhat reduced flow rate which is due in parts to added friction, provides optimum agitating conditions in the liquid without requiring more power input.

Accordingly, it is a primary object of this invention to provide agitating devices incorporating draft bend assemblies which afiord optimum agitation in such elongated tanks with a minimum of power input.

Another object of the invention is to provide agitators of this type affording a high mixing action which is highly eflicient in blending liquids or mixing solids into liqids ,dand improving heat transfer to a large quantity of iqui A further object of this invention is to provide such agitating devices which may be utilized in liquid containing tanks wherein the liquid level is variable in depend.- ence upon certain factors incident to the use of the tanks;

An additional object of the invention is to provide agitating devices of this type which are relatively compact, self-contained and portable, and therefore may be removed from and mounted upon mixing tanks with a minimum of effort.

Other objects and advantages of the invention will be 2,791,406 Patented May 7, 1957 apparent from the following description, the accompanying drawings and the appended claims.

In the drawings-- Fig. 1 is a vertical section through a tank provided with an agitating device in accordance with the invention;

Fig. 2 is a detail view, partly in section and partly in elevation, of the agitating device seen in Fig. 1;

Fig. 3 is a section along line 33 of Fig. 2;

Fig. 4 is a section along line 4-4 of Fig. 2;

Fig. 5 is a vertical section through a tank provided with a modified type of agitating device in accordance with the invention;

Fig. 6 is a detail view of the draft bend assembly'provided in the agitating device of Fig. 5;

Fig. 7 is a vertical section through a tank provided with other modified agitating devices in accordance with the invention;

Fig. 8 is a detail view of the draft bend assembly on one of the agitating devices seen in Fig. 7;

Fig. 9 is a detail view of the draft bend assembly on the other agitating device in Fig. 7; and

Fig. 10 is a vertical section through a tank provided with a single agitating device incorporating the construction of Fig. 9.

Referring to the drawings, which illustrate preferred embodiments of the present invention, Fig. 1 shows one application of the agitating devices provided by the invention wherein liquid to be acted upon is contained in a tank 19 which is elongated in one horizontal direction, and is therefore shown in section through its elongated dimension. Such a tank might be, for example, a rail road tank car for transporting liquids, or any other tank of similar elongated configuration. The tank is provided with an access opening or port 12 through which the agitating device is extended into the liquid.

Referring to Fig, 2, the agitating device includes a horizontal mounting plate 13 which may be attached across port 12 in any suitable manner, and upon which a motor 15 is carried. Depending from motor 15 is a drive shaft 16 which extends through an. upper hearing or stuffing box 17 on plate 13 and'through a lower bearing 18 supported by a spider. construction. indicated generally at 2 A mixing propeller 22, preferably a conventional three blade square pitch marine type propeller, is secured to the end of shaft 16 and thus adapted for driving by motor 15.

The entire draft bend housing assembly 25 is suspended from mounting plate 13 by tie rods 26 which extend through and are suitably fastened to a lower plate 27. Assembly 25 includes an inlet or throat section 30 of inverted frusto-conical configuration, with the larger upper end thereof surrotmding propeller 22 and having small peripheral clearancewith the tips of the propeller blades, and a lower section 32 depending from inlet section 30 and divided, into opposed curved outlet sections 33. Both outlet sections 33 curve through approximately and terminate in substantially vertical outlet openings 34 of generally semi-circular cross-section as shown in Fig. 4.

This agitating device is arranged within the tank to face the outlets 34 along the longer dimensions of tank 10, as in Fig. 1, and the liquid thus issues from assembly 25 in the direction of arrows 35 at relatively high velocity, seting up the flow pattern within the tank as indicated by the arrows in Fig. 1 A segmental bailie 36 may be provided at the intersection of outlets 33 to minimize swirl in the liquid as induced by the propeller 22, and thereby to give maximum movement of the liquid in the direction of arrows 35.

To obtain the desired high velocity output from the agitator without unduly increasing the amount of power necessary to maintain a satisfactory flow rate, it is desir:

able to restrict the total outlet area to less than the inlet area. Experiments have indicated that suitable results are obtained with the area ofoutlet openings 34 equal to from one-halfthe cross-sectional. area of inlet .30 (the larger area about the propeller) to a value just less than the total inlet area, approximately in the range of 10:5 up to 10:9. Optimum results have been obtained with the total outlet cross-section equal to about 60 percent of the total inlet cross-section.

The walls of the draft bend housing assembly 25 are smoothly curved from the inlet toward the outlet, as shown in Fig. 2, and the bafile 36 extends vertically at the juncture of the outlet sections 33 up toward the throat section 30, thus dividing the flow areas of the separate outlets into equal parts. This construction provides relatively high velocity output from outlets 34 which causes the liquid to flow laterally toward the farthest sides of the tank 10, and thereby to set up the flow pattern indicated in Fig. 1.

Referring to Fig. 5, a modified type of agitating device is shown mounted in a tank 40 and incorporating a modified draft bend housing assembly 45. This device is especially adapted for use in tanks wherein the liquid level is variable, and the draft assembly 45 is seen in Fig. 6 to include a plate 46 which may be suitably secured to the tie rods 47 and upon which is mounted a frusto-conical throat section 50 having outlet sections 52 extending upwardly and outwardly therefrom, turning through approximately 90 to locate the outlet opening 53 in a substantially vertical plane. The drive shaft 55 extends through a bearing 56 located at the intersection of outlet sections 52, and a suitable mixing propeller 57 is attached to the end shaft 55. The draft bend assembly 45 has substantially the same configuration and dimensions as assembly 25, but is supported in an inverted position upon its plate 46, so that the inlet is below the propeller and the outlets 53 are above and to one side of the propeller. This arrangement provides for the location of the inlet throat 50 closer to the bottom of the tank, as shown in Fig. at a level below which the liquid level is unlikely to recede. The flow pattern set up by this agitating device is opposite to the pattern set up in the arrangement of Fig. 1, but is equally effective in agitating the contents of the tank.

Figs. 7, 8, 9 and'lO show two somewhat dilferent types of agitating devices provided by the invention, and which are adapted to be mounted vertically along one side of an elongated tank to set up a natural flow pattern along the length of the tank as indicated by the arrows in Figs. 7 and 10. The devices dilfer from the embodiments of Figs. 1 and 5, respectively in that there is only one outlet opening in the draft tube assembly rather than two opposed outlets, and like reference numerals indicate parts common to all the devices. The housing assembly shown in detail in Fig. 8, and embodied in the agitating device shown on the left side of the tank in Fig.7, includes ,an upper inlet portion 60 surrounding the impeller, and a lower outlet portion 61 terminating in an outlet 62 which is adapted to be mounted in a substantially vertical plane, and which has the same general cross-sectional configuration as shown in Fig. 4. This draft tube assembly, incorporated in the agitating device shown generally at 65 in Fig. 7, directs the high velocity flow from the impeller across the bottom of tank 40 and toward the opposite corner, after which the flow pattern extends upwardly alongthe opposite wall, back through the liquid, and to inlet 60 of the impeller.

The agitating device 70 in Fig. 7 differs from the agitator 65 solely in that its draft tube assembly is inverted. This assembly is shown in detail in Fig. 9 as including an inlet portion 71 and an outlet portion 72 terminating in an outlet 73 which extends vertically and generally at right angles to the inlet. The impeller is housed within inlet portion 71 and driven by drive shaft 55 which extends through bearing 56 into the draft tube assembly.

In Fig. 10 the agitating device is shown in a typical variable liquid level installation wherein the device is mounted along one wall of tank 40, with the inlet portion 71 adjacent the bottom of the tank, so as to draw the liquid in and discharge it at relatively high velocity across the tank immediately below the surface of the liquid, thereby setting up the elongated flow pattern shown by the arrows inFig. 10. 7

While the forms of apparatus herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. An agitator especially adapted for use in liquid containing tanks having one horizontal dimension thereof considerably greater than the other horizontal dimension, comprising a drive shaft, means for mounting said shaft substantially vertically within the tank, a marine type mixing propeller having a relatively high ratio of flow to head secured to the lower end of said shaft, a draft bend housing assembly carried by said mounting means and having an inlet section surrounding said propeller, outlet sections on said housing terminating in a pair of outlet openings of generally semi-circular configuration in cross section facing in opposite directions from each other and extending in generally vertical planes, walls in said housing connecting said inlet and outlet sections and having smoothly curved and continuous inner surfaces free from abrupt changes in direction and gradually converging from said inlet section toward said outlet sections to provide a gradually constricted flowpath between said sections, said outlet openings having a total cross-sectional area substantially less than the largest cross-sectional area of said inlet section, means for rotating said shaft in a direction such that said propeller draws liquid through said inlet section and discharges the liquid laterally of said housing assembly through said outlet openings, the gradual-constriction of said flow path providing. for an increase in head sufiicient to discharge the liquid from said outlet opening at relatively high velocity, and said draft bend housing assembly being positioned by said .mounting means to direct said outlet openings along the greater horizontal dimension of the tank to provide for agitation of the liquid contained in the tank in the parts thereof farthest from said draft bend housing.

2. An agitator especially adapted for use in liquid containing tanks having one horizontal dimension thereof considerably greater than the other horizontal dimension, comprising a drive shaft, means for mounting said shaft substantially vertically within the tank, a marine type mixing propeller having a relatively high ratio of flow to head secured to the lower end of said shaft, a draft bend housing assembly carried by said mounting means and having an inlet section surrounding said propeller, a single pair of outlet. sections extending downwardly and outwardly in opposite directions away from said inlet section and terminating in outlet openings of generally semicircular configuration in cross-section, said outlet openings being located in substantially parallel and. generally vertically extending planes, saidinlet and outlet sections including connecting wall portions having smoothly curved and continuous inner surfaces free from abrupt changes in direction and gradually converging from said inlet section toward said outlet sectionsto provide a gradually constricted flow path between said sections, said outlet openings having a total cross'sectional area substantially less than the largest cross-sectional area of said inlet section, means for rotating said shaft in a direction such that said propeller draws liquid through said inlet section and discharges the liquid laterally of said housing assembly through said outlet openings, the gradual constriction of said flow path providing for an increase in'head sufiicient to discharge the liquidfrom said outlet opening at relatively high velocity, and said draft bend housing assembly being positioned by said mounting means to direct said outlet openings along the greater horizontal dimension of the tank to provide for agitation of the liquid contained in the tank in the parts thereof farthest from said draft bend housing.

3. In agitating apparatus of the character described the combination of a liquid receiving tank having a closed bottom and having one horizontal dimension substantially greater than the other horizontal dimension thereof, a drive shaft, means mounting said shaft generally vertically in said tank with the upper end thereof at the top of said tank and the lower end thereof spaced from said bottom, a marine type propeller having a relatively high ratio of flow to head carried on the lower end of said shaft, a draft bend housing assembly supported in fixed position on said mounting means, said housing including an inlet section surrounding said propeller and an outlet section defining an outlet opening, said mounting means being oriented with respect to said tank to face said outlet opening along the greater horizontal dimension of said tank drive means connected to said upper end of said shaft for rotation of said propeller in a direction to draw liquid through said inlet section and discharge said liquid through said outlet opening laterally of said housing, said outlet section having a cross sectional area substantially less than the largest cross sectional area of said inlet section, and wall portions defining a passage between said inlet and outlet sections having smoothly curved and continuous inner surfaces free from abrupt changes in direction and gradually converging from said inlet section toward said outlet section to provide a flow path between said sections gradually constricted in the direction of said outlet section, said gradually constricted flow path providing for an increase in head suflicient to discharge liquid from said outlet opening at relatively high velocity along the greater horizontal dimension of said tank to provide for agitation of the liquid at the end of said tank farthest from said housing.

4. Apparatus in accordance with claim 3 wherein the ratio of the cross sectional area of said outlet section to the cross sectional area of said inlet section is in the range of 10-9 to 105.

5. Apparatus in accordance with claim 3 wherein the smallest cross sectional area of said outlet section is approximately sixty percent of the largest cross sectional area of said inlet section.

References Cited in the file of this patent UNITED STATES PATENTS 535,237 Cawthron et a1 Mar. 5, 1895 1,163,704 Taylor Dec. 14, 1915 1,720,333 Ketchum July 9, 1929 1,786,009 DuWe Dec. 23, 1930 2,164,944 Rosmait July 4, 1939 FOREIGN PATENTS 504,634 Belgium July 31, 1951