Abstract:
A liquid propellant management device for placement in a liquid storage tank adjacent an outlet of the storage tank to substantially reduce or eliminate the formation of a dip and vortex in the liquid of the tank, as well as prevent vapor ingestion into the outlet, as the liquid drains out through the outlet. The liquid propellant management device has a first member adapted to suppress the formation of a vortex of a liquid exiting the storage tank. A plate is affixed generally perpendicular to the first member, wherein the plate is adapted to suppress vapor ingestion into the outlet by reducing a dip in a surface level of the liquid leaving the tank. A second member is affixed to the second side of the plate. The second member ensures that the plate is wet with liquid and assists in positioning bubbles away from the outlet.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED DEVELOPMENT 
     This invention described herein was made in the performance of work under NASA Contract No. NCC8-190 and is subject to the provisions of Section 305 of the National Aeronautics and Space Act of 1958 (72 Stat. 435: 42 U.S.C.2457.) 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to anti-vortex and vapor-ingestion-suppression devices, and more particularly to an anti-vortex vapor-ingestion-suppression device that works in various gravity environments. 
     BACKGROUND OF THE INVENTION 
     Many space vehicles, generally use a liquid propellant which is stored in storage tanks and fed into engines during take off and flight in space. The liquid must be moved from the storage tanks to the engine in an efficient manner. First, vapor or gas cannot be allowed to enter the engines in any great amount or too early in the ignition process. If gas is introduced into the engines, it may cause a stall or other malfunctioning of the engine that may increase the possibility of engine failure. It is generally known in the art to provide a device that is be placed in the propellant storage tanks which will reduce the acquisition of gas into the engine. Second, it is desirable to empty the storage tanks as completely as possible during an engine burn and flight to reduce re-entry weight and increase vehicle payload. Typically, a portion of liquid propellant still remains in the tank, thereby increasing the vehicle weight and reducing the maximum payload of the vehicle. 
     One solution to vapor ingestion is to provide a screen that encompasses the interior area of the tank or at least a portion thereof. Therefore, fluid is wicked through the screens by capillary action, and vapor or gas bubbles are prevented from flowing through the screens by the bubble point pressure of the fluid screen system. Screen systems are made most advantageous only for storage tanks being used in low gravity and are less useful in environments where significant gravity is present. Additionally, the screen systems typically cannot be used with certain liquid propellants such as hydrogen peroxide due to material incompatibility between H 2 O 2  and typical screen materials. The increased surface area of the screens adds more area for chemical reactions where the liquid propellant may decompose. 
     Other systems provide vanes extending a distance from the sump of the tank towards the walls of the storage tank. These vanes help bring liquid propellants to the outflow area of the storage tank through capillary action. Furthermore, the vanes help reduce the ingestion of gas bubbles into the engine of the vehicle. The vanes used in known vapor ingestion suppression systems, however, are for very low flow rates and cannot provide substantial vapor ingestion suppression at the higher flow rates of many reusable space craft. 
     Thus, the generally known anti-vapor ingestion systems include several drawbacks. Additionally, known systems allow too much fuel to be left in the storage tanks thereby decreasing the efficient use of the fuel stored in the tanks and decreasing the payload for a similarly sized tank and vehicle. Additionally, the known systems increase the breakdown of certain propellant fluids into gas and non-fuel or inert substances. Therefore, there is a need in the art for a device that will allow for anti-vortexing of the fuel as it leaves the tank, and to increase ingestion of liquid propellant into the sump and outlet, thereby increasing the efficiency of the storage tanks and decreasing the possible ingestion of gases. 
     SUMMARY OF THE INVENTION 
     In a first preferred embodiment of the present invention, a storage vessel has an outlet and a liquid propellant management system adjacent the outlet. The liquid propellant management system reduces a dip and a vortex of a liquid, which reduces vapor ingestion into the outlet of the tank in both high gravity environments and low gravity environments. The liquid propellant management system has a first vane with bores, a first end a second end. A plate is also included with bores having a first side and a second side where the first side is operably associated with the first vane. The system also has a second vane operably associated with the second side of the plate. The first vane is adapted to substantially reduce a vortex of a liquid. The plate substantially reduces a dip of a liquid due to frictional energy dissipation, and the second vane provides frictional energy dissipation and substantially wets the plate with a liquid in the tank. 
     In a second preferred embodiment of the present invention, a liquid propellant management device for use in a liquid storage tank has a first member to suppress the formation of a vortex in a liquid exiting the tank. A plate operably associated with the first member is also included to substantially reduce vapor ingestion into the outlet of the tank. A second member is also included and operably associated with the plate to wet the plate with liquid stored in the tank and provide additional energy dissipation via friction. 
     In a third preferred embodiment of the present invention, a liquid storage tank is disclosed which has at least an outlet and a liquid management device. The liquid management device has a vortex suppression vane with a plate, to reduce ingestion of vapor, affixed to the top of the vortex suppression vane. Also, a bubble positioning vane is affixed atop the plate. The vortex suppression vane suppresses vortices that attempt to form in liquids as they are exiting the liquid storage tank. The plate, reduces the dip due to frictional energy dissipation as the liquid attempts to exit the tank. The bubble positioning vane works to ensure that the plate is wet with liquid at all times during emptying of the liquid storage tank. It also helps to position the bubbles away from the outlet to ensure that ingestion of gas into the outlet is non-existent or minimal. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
     FIG. 1 is a perspective, cross-sectional view of a tank including a liquid management device according to a first preferred embodiment of the present invention; 
     FIG. 2 is an enlarged perspective view of the liquid management device in the storage tank shown in FIG. 1; 
     FIG. 3 is a cross-sectional view taken along line  3 — 3  of FIG. 2; 
     FIG. 4 is a fragmentary view of a liquid storage tank including a volume of liquid; 
     FIG. 4 a  is a fragmentary view of a liquid storage tank including a volume of liquid being withdrawn therefrom; 
     FIG. 4 b  is a fragmentary view of a liquid storage tank with a residual volume of a liquid still held therein; 
     FIG. 5 illustrates a partial cross-sectional view of a liquid storage tank holding a volume of liquid, and having the liquid management device according to the present invention installed; 
     FIG. 5 a  illustrates the liquid storage tank of FIG. 5 having a volume of liquid extracted; 
     FIG. 5 b  illustrates the liquid storage tank of FIG. 5 with a residual volume of liquid; 
     FIG. 6 is a perspective view of a liquid management device according to a second preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     With reference to FIG. 1, a liquid management device or an anti-vortex/vapor-ingestion-suppression device (AVVIS)  10  is shown in accordance with a preferred embodiment of the present invention. The AVVIS  10  operates in variable gravity environments and is affixed within a tank  12  near a sump  14  of tank  12 . Sump  14  includes an outlet port  15 . Extending externally from tank  12  and connected to outlet port  15  is an outlet line  16 . Tank  12  generally has a cylindrical wall  18  extending between a tank bottom  20  and a tank top  22 . It will be understood, however, that tank  12  may be any shape suitable for the intended application. Tank  12  is a liquid storage tank where the liquid stored therein exits through sump  14  and outlet port  15  and into outlet line  16 . Tank  12  is generally pressurized or has a higher pressure relative to outlet line  16 . The higher pressure of tank  12  helps to ensure that fluid in tank  12  exits through outlet line  16  to its intended destination. Tank  12  forms a storage tank for a vehicle, and the liquid stored in tank  12  is generally a liquid propellant, particularly a fuel or oxidizer. The outlet line  16  leads to an engine which uses the liquid propellant stored in tank  12  for powered flight. Generally, fuels include high grade hydrocarbons, such as kerosene, and oxidizers include liquids such as hydrogen peroxide. 
     With continuing reference to FIG.  1  and further reference to FIG. 2, AVVIS  10  generally includes four vanes  24  which meet at a center or interconnection area  26 . Interconnection area  26  is generally directly above outlet port  15 . Resting on a top edge  27  of each of vanes  24 , and affixed to the top edges  27  of the vanes  24  by any appropriate means, is a plate  28 . Extending from a top surface  28   a  of plate  28  and generally co-planar with vanes  24  are bubble positioning vanes  30 . Bubble positioning vanes  30  also meet each other at the intersection area  26 . At the outside terminus  24   a  of each vane  24  is a post  31  to which the associated vane  24  is affixed. Each vane  24  is affixed to its respective post  31  through any suitable means such as spot welding or adhering material. Posts  31  are then mounted to sump  14 , again by any appropriate fastening or adhering means. The posts  31  may each be press fitted into associated bores, formed in sump  14 , or they may also be welded to position the AVVIS  10  directly over the outlet port  15 . In this way, AVVIS  10  is precisely affixed to sump  14  so that it does not move during operation. 
     Each vane  24  includes a plurality of vane bores  32 . Vane bores  32  have an exemplary diameter of preferably about 0.2 inches (5.08 mm) to about 0.5 inches (12.70 mm). Vane bores  32 , however, may have any diameter that is suitable to the particular application for which the AVVIS  10  is used. Additionally, vane bores  32  are formed in a pattern on each vane  24  that is generally nested. The pattern is one similar to any nested pattern of circles or spheres simply spaced apart by a distance between the centers of between about 0.6 inches (15.24 mm) and about 0.8 inches (20.32 mm). Again, it will be understood by those skilled in the art, that vane bores  32  may be separated by any distance suitable to the application to which the AVVIS  10  is put. Generally, it is desirable to size and position vane bores  32  such that each vane  24  is about 20% to about 40% porous. 
     Referring to FIGS. 2 and 3, vanes  24  are placed in at an angle of preferably about 85 to about 95 degrees to each other and form the body or main support structure of AVVIS  10 . Plate  28  includes a plurality of plate bores  36 . Plate bores  36  are generally similar to vane bores  32  such that vanes  24  and plate  28  may be formed from a single piece of starting sheet material. Plate  28  may either be a single piece or may be formed from a plurality of sections affixed to the top edge  27  of vanes  24  in between two adjacent vanes  24 . Plate  28  also forms a cone having a vertex or center  37  coinciding with and adjacent interconnection area  26 . The cone formed by plate  28  has a directrix formed by an outer perimeter  38  of plate  28 . The angle θ of plate  28  (FIG. 3) from the outer perimeter  38  to the interconnection area  26  preferably is about negative  5  to about negative 15 degrees from a plane  39  extending perpendicular to post  31  and bisecting the outer perimeter  38 . The vertex  37  of plate  28  is below the outer perimeter  38  of plate  28 , thus the reason for the negative angle. It will be understood that the angle may also be designated positive if viewed from the plane of the vertex  37 . 
     The bubble positioning or wicking vanes  30  extend from the top surface  28   a  of plate  28 . Bubble positioning vanes  30  are substantially solid and do not generally include bores. It will be understood that bubble positioning vanes  30  need not be coplanar with vanes  24  nor be equal in number to vanes  24 . Bubble positioning vanes  30  have top edges  40  that each extend at an angle θ′ (FIG. 3) from a plane  43  extending perpendicular to add bisecting, an outside edge  44  and parallel to its associated post  31 , towards the intersection area  26 . Angle θ′ is preferably between about negative 3 degrees to about negative 15 degrees. Again, the portion of bubble positioning vane  30  near intersection area  26  is lower than the portion near outer perimeter  38 , therefore the negative degrees. It will be understood that the degrees are positive if viewed from the plane of the portion of the bubble positioning  30  vane near intersection area  26 . 
     With reference to FIGS. 4 through 4 b,  tank  12  is shown to contain a liquid  42  and no liquid propellant management device to reduce a dip  42   a  in the upper surface level  42   b  of the propellant attempting to exit tank  12 . Here gas may be ingested into outlet port  15  and moved through outlet line  16 . The initial dip  42   a  is produced by inertia forces due to draining of the tank. However, gas bubbles are more buoyant and attempt to float up, which is in a direction opposite the inertia of the fluid moving out of tank  12  through sump  14 . Therefore, this buoyancy to inertia effect initially creates dip  42   a  and is increased by the vortex motion of the liquid  42  as it attempts to exit through the outlet port  15 . Dip  42   a,  increased in size by a vortex, increases the likelihood of the ingestion of gas-into outlet line  16 . When there is enough liquid  42  in tank  12 , as shown in FIG. 4, no dip  42   a  is present. However, as the liquid  42  empties out of tank  12 , dip  42   a  begins to: form, as shown in FIG. 4 a.  The bottom of dip  42   a  grows ever nearer outlet port  15  as more and more liquid  42  is removed from tank  12 . Finally, as shown in FIG. 4 b,  dip  42   a  enters outlet port  15  thereby allowing ingestion of gas into outlet port  15  and outlet line  16 . When gas is ingested into outlet line  16 , it may cause the engine to stall. 
     Generally, gas in a propellant tank comes from the tank pressurization system. However, with propellants like H 2 O 2 , the liquid can decompose into gaseous components. Cryogenic liquids also generate gas when heated due to low boiling points. Furthermore, when liquid  42  is removed several times from tank  12  several successive dips  42   a  are formed. Each of these successive dips creates a chance for gas to be introduced into the tank  12 . The amount of liquid  42  left in tank  12  when dip  42   a  enters sump  14  is called the “residual volume”. 
     AVVIS  10  may be formed from a wide variety of suitable materials including plastics, composite materials, or metals and metal alloys. Whatever material the device is fabricated from, it must be prepared for use with the intended propellant. This includes pacification and: cleaning for oxidizers, such as H 2 O 2 . The pacification of the material helps to reduce the reactivity of the material with the liquid  42  in tank  12  especially, if the liquid comprises hydrogen peroxide. If the liquid is hydrogen peroxide, screens or larger devices would increase the rate of break down of the hydrogen peroxide into water and oxygen gas. Neither water nor gaseous oxygen are proper propellants for an engine plus they increase the tank gas pressure possibly requiring venting of the tank to keep it within its structural limits. Therefore, it is necessary to substantially eliminate the breakdown of the propellant. 
     AVVIS  10  also has a relatively small surface area that takes up only a small portion of the internal volume of tank  12  and does not provide a significant surface area for the breakdown of hydrogen peroxide. Generally, AVVIS  10  is no larger in diameter than sump  14 , which in turn is preferably only about 20% of the diameter of tank  12 . AVVIS  10  also has a height of preferably about one-half its diameter, but the actual dimensions depend on the application. It is to be understood, however, that AVVIS  10  may be used with any liquid propellant that must be stored in tank  12  before it is removed. 
     With reference to FIGS. 5 through 5 b,  AVVIS  10  provides a means to reduce the residual volume of liquid  42  left in tank  12  after attempting to empty tank  12  either through a propellant dump or through an engine burn. Generally, tank  12  is pressurized to a pressure of about 70-85 pounds per square inch (psi). Plate  28  acts as a vapor ingestion suppression mechanism that initially reduces the downward motion of the gas liquid interface  42   b  to form dip  42   a.  As the bottom of dip  42   a  reaches plate  28 , the friction on plate  28  removes the kinetic energy of the liquid gas interface thereby flattening or reducing dip  42   a  formed in the liquid. The liquid  42  flows through plate bores  36  reducing the kinetic energy thereof. Plate bores  36  increase the interaction of plate  28  with liquid  42  thereby increasing the effectiveness of plate  28  to reduce the kinetic energy of the liquid  42 . Vanes  24  reduce the vortex formed by the liquid  42  as it attempts to leave tank  12 . Vanes  24  reduce the momentum of liquid  42  as it enters sump  14 . Vane bores  32  also increase the interaction of vanes  24  with liquid  42  to help reduce the momentum of the liquid  42 . Additionally, vane bores  32  allow the liquid  42  to flow through vanes  24  as opposed to around the vanes  24 . As the liquid  42  flows through vanes  24 , the momentum of the liquid  42  is reduced to a greater degree than if the liquid  42  was forced to flow around vanes  24  due to frictional energy dissipation. Additionally, if the liquid  42  was not allowed to flow through vanes  24 , additional mini-dips might be created between each of the vanes  24 . As vanes  24  reduce the vortex in the liquid  42 , dip  42   a  becomes less pronounced. Therefore, vanes  24  work in conjunction with plate  28  to resist ingestion of gas into outlet line  16 . Plate  28  initially reduces dip  42   a  while vanes  24  reduce the vortex force so that the vortex force cannot enhance the dip  42   a.    
     The residual volume that is not able to be removed from tank  12  and must be accounted for or it may adversely affect a vehicle which attempts to reenter the earth&#39;s atmosphere. Therefore, the residual volume reduces payload that can be carried by a vehicle. With reference to FIGS. 4 to  4   b,  the progression of liquid  42  being removed from tank  12  is shown without AWIS  10 . As the liquid  42  is removed from tank  12 , dip  42   a  becomes enlarged. At the time shown in FIG. 4 b,  dip  42   a  becomes so great that gas is being, or will be, ingested into outlet port  15  rather than liquid  42  alone. At this point, no more liquid  42  can be safely removed from tank  12  without causing an adverse reaction in the engine. Therefore, FIG. 4 b  shows an example of a “residual volume” that is left in tank  12  when AVVIS  10  is not present. Generally, the “residual volume” in tanks with no AWIS  10  device is between about 3% and 6% of the total capacity of the tank  12 . 
     When AWIS  10  is present, in a tank similarly sized and shaped as one shown in FIGS. 4 through 4 a,  residual volumes in tank  12  are generally no more than between about 0.5% to about 1%. FIGS. 5 through 5 b,  show a progression similar to what is shown in FIGS. 4 through 4 b.  However, due to the presence of AWIS  10 , the dip  42   a  is not present or is greatly reduced. The interaction of AVVIS  10  with the liquid  42  being removed from tank  12  reduces or eliminates the dip such that it does not significantly affect the removal of the liquid from tank  12 . Therefore, the residual volume left in the tank  12  is greatly reduced which enhances the efficiency of tank  12 . Though a small residual volume may still be present in tank  12  to ensure that no gas is ingested through outlet line  16 , the residual volume is about three times less than the residual amount of propellant left in tank  12  when no AWIS  10  is present. 
     Bubbles are capsules of gas surrounded by liquid  42  in tank  12 . The formation of bubbles may be through any number of mechanisms described above. The cone shape of plate  28  helps position the bubbles away from sump  14 . In a liquid environment, since a bubble is more buoyant it will tend to flow upward towards plate  28  out of sump  14 . Once it encounters plate  28 , it will then move along the angled under portion  28   b  (FIG. 3) of plate  28  which is directed away from sump  14 . Since a bubble will always tend to move up from the sump  14 , angle θ of plate  28  will ensure that it moves out of sump  14  as well. If plate  28  were flat, the bubble would only move up to the plate and then stop. A flat plate would hold the bubble in place. Due to the angle θ of plate  28 , the bubble moves away from and further out of the sump  14 . 
     Bubble positioning vanes  30  act as wicking and bubble placement vanes. In a low acceleration or low gravity environment, capillary forces of the liquid  42  force it into the interface of bubble positioning vanes  30  and plate  28 , thereby keeping plate  28  wet with liquid  42 . The capillary forces created on bubble position vanes  30  ensure that liquid  42  remains near the sump  14 . If bubble positioning vanes  30  are not present to provide such capillary forces in low acceleration environments, liquid  42  would be more likely to move away from sump  14  and up walls  18  of tank  12 . Additionally, bubble positioning vanes  30  help to ensure that bubbles are positioned away from sump  14 , especially large bubbles formed on the top surface  28   a  of plate  28 . Sump  14  is below AVVIS  10  whereas larger bubbles formed in tank  12  would first encounter top surface  28   a  of plate  28  before entering sump  14 . Bubble positioning vanes  30  help move the bubbles away from sump  14  in a similar fashion, as does plate  28  for bubbles formed in sump  14 . Again, as bubbles are buoyant, they tend to move up and, due to the angle θ′ of bubble positioning vanes  30 , bubbles will tend to move up and away from the sump  14  towards the outer perimeter  38 . This helps to ensure a reduction or a non-ingestion of gas vapor from the bubbles into sump  14 . 
     With reference to FIG. 6, on AVVIS  50  in accordance with a second preferred embodiment of the present invention is shown. The AWIS  50  includes anti-vortex vanes  52  in a generally vertical orientation that intersect at an intersection area  54 . Adjacent and affixed to the top edge  56  of each of the anti-vortex vanes  52  is a plate  58 . Plate  58  has a cone shape substantially identical to the cone of plate  28  described in reference to the AWIS  10  of the first embodiment. Bubble positioning vanes  60  extend above plate  58  and are substantially planar with anti-vortex vanes  52 . Bubble positioning vanes  60  also intersect at the intersection area  54  but each is affixed to a respective tab  62  of one of the anti-vortex vanes  52  which extends through plate  58 . Then a rivet or other interconnecting means connects each of the bubble positioning vanes  60  with its respective tab  62  through bore  63  to hold each of the bubble positioning vanes  60  in place. Additionally, tabs  64  are formed on a bottom portion of each of anti-vortex vanes  52  with a bore  66  formed in each mounting tab  64  to allow a screw or other fastening means to be used to affix AWIS  50  to a sump. Antivortex vanes  52  and plate  58  contain bores substantially similar to bores  32  of AWIS  10 . 
     It is understood that the preferred embodiments described herein may be altered without departing from the scope of the present invention. AVVIS  10  or AWIS  50  may be affixed to a sump  14  or a tank  12  by any number of suitable. The edges of the anti-vortexing vanes  24 ,  52  may themselves be directly affixed to the wall  18  of tank  12  without reducing the effectiveness of AWIS  10  or AWIS  50 . Furthermore, the relative size of the plates  28 ,  58 , antivortexing vanes, and the bubble positioning vanes  30 ,  60  may be adjusted to produce the most desirable effect depending upon the orientation and size of tank  12  into which they are placed. Furthermore, the overall size of AWIS  10  or AWIS  50  may be adapted for the particular tank into which it is to be placed to produce the optimum anti-vortexing and anti-vapor ingestion effect. It will also be understood that AWIS  10  and AVVIS  50  are effective in environments that include gravity and those without gravity. In particular, the present invention is effective in reducing the vortex and vapor ingestion described herein as well as in wetting the plate, while in various gravity environments. AVVIS  10  and AWIS  50  are also very helpful in respect to holding the liquid  42  near the sump  14  in low and no gravity environments. 
     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.