Fluid handling – Systems – Plural tanks or compartments connected for serial flow
Reexamination Certificate
2000-02-03
2001-04-24
Lee, Kevin (Department: 3753)
Fluid handling
Systems
Plural tanks or compartments connected for serial flow
C251S127000, C220S563000, C220S734000
Reexamination Certificate
active
06220287
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a baffle for suppressing slosh in a tank containing fluids and a tank for incorporating same.
BACKGROUND OF THE INVENTION
Launch vehicles used for space exploration use a large amount of liquid propellant while traveling through the earth's atmosphere and into outer space. Unlike long distance travel for many airplanes, there are no refueling stops or rendezvous with refueling aircraft in mid-flight for space vehicles. Therefore, launch vehicles used for space exploration must carry onboard all fuel necessary for propulsion and power generation for the entire voyage. This requirement means that launch vehicles must be equipped to store hundreds of thousands of pounds of liquid propellant, like liquid oxygen, and handle such propellant efficiently and safely.
One problem encountered with transporting large volumes of liquid fluids in launch vehicles is the sloshing of the fluids in the tanks. Slosh is caused by tank motions during travel and results in the production of forces that can affect launch vehicle stability and control. If the fluid is allowed to slosh freely in the tank, the moving fluid can have an adverse effect on the flight of the launch vehicle. For example, exciting the fluid above its natural frequency can result in oscillating, pendulum-like forces that can change the stability of the overall dynamic system of the vehicle. As is readily appreciated by those skilled in the art, sloshing fluids can produce forces that cause additional vehicle accelerations that, when responded to by the vehicle control system, form a closed loop that can lead to instability and, ultimately, structural failure. Consequently, the slosh must be suppressed.
Slosh suppression devices typically are used to damp liquid motions in the tanks of launch vehicles. Existing systems for slosh suppression primarily consist of a series of annular ring baffles arranged around the inner wall of the tank. These ring baffles run continuously around the periphery of the inside of the tank and are spaced apart by a given distance. The ring baffles are designed to not flex or bend with the moving fluid.
Numerous experiments have been performed on the effectiveness of various baffle designs. For example, NASA Technical Note D-694, dated February 1961, briefly discusses experiments involving the damping characteristics of semi-circular plates placed at given intervals around the inside of a tank. The technical note illustrates numerous different configurations for baffles that were tested. However, the experiments were aimed at gauging the effectiveness of the various baffle designs when incorporated with annular rings. The note finds that flat rings with a sharp edge are the most effective dampers for baffle depths greater than two chords.
Additionally, NASA Space Vehicle Design Criteria Report on Slosh Suppression SP-803, dated May 1969, and David G. Stephens article entitled “Flexible Baffles for Slosh Damping,”
J. Spacecraft
(1965), discuss the use of flexible baffles to damp slosh in a tank. Both references conclude that flexible ring baffles could be used on space vehicles. However, as the Stephens article points out, a simple flat ring baffle was found to be the best damper of those tested. Although many different baffle designs have been experimented with in the past, including flexible baffles, the baffles adapted for actual use in launch vehicles continue to primarily consist of the rigid annular ring type design.
Rigid annular ring baffles have been successfully used to suppress slosh in the tank of a launch vehicle. However, ring baffles of this type add more than an insignificant amount of weight to the overall weight of the vehicle. For example, the Delta III rocket employs a rigid ring design that weighs approximately 400 pounds. In order to prevent the rocket from being unduly heavy, the weight devoted to the rigid ring design disadvantageously limits the weight of other items onboard the launch vehicles, such as the payload, the fuel and any other equipment.
SUMMARY OF THE INVENTION
It would be advantageous to provide a baffle for suppressing slosh in a tank that can sufficiently suppress slosh, while at the same time providing weight, material, and cost savings over ring baffles. It would also be advantageous to provide a tank for incorporating such a baffle.
The foregoing and other advantages are provided by the invention of an improved baffle for suppressing slosh in a tank adapted for containing fluids. The baffle includes an attachment portion adapted to connect the baffle to an inner sidewall of the tank, and a baffle body extending from the attachment portion and adapted to protrude into the tank.
According to one aspect of the invention, the baffle includes a smoothly curved corrugation operably connecting the attachment portion and the baffle body. For example, the smoothly curved corrugation operably connecting the attachment portion and the baffle body may be either S-shaped or U-shaped. In such an embodiment, the baffle body is permitted to flex relative to the attachment portion in response to movement of fluid within the tank. According to another aspect, the baffle body has a proximal edge, a distal edge opposite the proximal edge, and a plurality of ribs extending from the proximal edge to the distal edge. As such, the baffle body is advantageously stiffened without unnecessarily increasing its weight. According to either aspect, the baffle body may be semi-circular in shape. In addition, the baffle may further include a doubler extending along the attachment portion at an attachment lip. The doubler acts to alleviate stress in the attachment portion at attachment holes when the baffle is attached to the inner sidewall of the tank. Although not necessary, the doubler also can extend outwardly from the attachment portion and into the tank in two tongue-like projections at opposite ends of the doubler in order to provide added reinforcement.
The tank of the present invention includes a plurality of baffles operably attached to at least one sidewall that at least partially defines an internal cavity for housing fluids. The plurality of baffles extend into the internal cavity defined by the at least one sidewall and comprise first and second baffles disposed at first and second heights, respectively, within the tank. Preferably, the first and second heights are different. Each baffle extends along only a portion of a perimeter of the at least one sidewall, and the first and second baffles are disposed at different peripheral locations within the tank to further suppress the slosh. The plurality of baffles may also be operably connected to each other by a connecting member to ensure that the baffles move in concert.
According to the present invention, an improved baffle is provided to effectively limit slosh within a tank that weighs less than conventional ring baffles. As such, the overall weight of the launch vehicle can be advantageously reduced or additional payload or fuel can be carried without increasing the overall weight of the launch vehicle. However, the baffle of the present invention can be designed such that slosh is suppressed as well or better than the suppression provided by ring baffles, even though the overall weight of the baffles is significantly reduced.
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Stephens, David G.,Flexible Baffles for Slosh Damping, NASA Langley Research Center, Langley Station, Hampton, VA; vol. 3, No. 5.
Cole, Henry A., Jr., and Gambucci, Bruno J., Measured Two-Dimensional Damping Effectiveness of Fuel-Sloshing Baffles Applied t
Alston & Bird LLP
Lee Kevin
The Boeing Company
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