Gas and liquid contact apparatus – Fluid distribution – Valved
Reexamination Certificate
2002-09-10
2004-11-30
Bushey, Scott (Department: 1724)
Gas and liquid contact apparatus
Fluid distribution
Valved
C261S065000, C261S121100, C261S124000
Reexamination Certificate
active
06824125
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The invention relates to an apparatus and method for producing vortex ring bubbles of a gas in a host liquid. It allows these rings to be continually generated under conditions in which the parameters of their generation can be independently controlled over a wide range. It therefore allows one device to produce, within limits, a range of different rings from slow-moving, large rings, to fast-moving, small rings and various combinations in between.
2. Description of the Prior Art
Some forty years ago it was first reported that it that it is possible to generate toroidal ring-shaped bubbles, or ring bubbles as they were then called, of gas rising in liquids. These are in fact vortex rings in which the gas collects in the ring-shaped core and which is thereby made visible as a circular tube of gas. In recent years it has become appreciated that they are a natural phenomenon and have even been observed to be produced by whales and dolphins evidently simply for amusement. Apparently they do this by rapidly exhaling a short pulse of air which self organizes into the ring. Skilled professional divers have also been known to produce them by carefully exhaling a pulse of air upwards. It is now known that the key to formation of ring bubbles lies in the momentary flow of a gas, i.e. a pulse of gas, through a nozzle into a surrounding liquid medium. This is the natural phenomenon that whales and dolphins have learned to exploit, but not just any pulse of gas will work. Apparently, proper adjustment of the parameters that determine the pulse characteristics is critical if rings are to form, as opposed to just normal chaotic plumes of bubbles. It is well known that for a given nozzle shape, there are two parameters that determine the behavior of this kind of pulsed nozzle flow. One is the pressure of the source that establishes the strength of the pulse. Good flow will arise if this pressure is constant and does not decay while the flow exits the nozzle. The other parameter is the time duration of that pulse. Evidently, if both these parameters are within certain ranges of values rings will form, but outside of those ranges rings will not form. Instead, single bubbles or chaotic turbulent jets of bubbles will be obtained. Additionally, variations of these parameters, within the ranges, can be expected to give rise to different kinds of rings. For example, low source pressures, and long duration pulses will generally give rise to large slow moving rings. Conversely, higher pressures and shorter pulses will give rise to smaller, faster moving rings. Ideally, any apparatus designed to generate these rings should allow the operator to easily change the values and thereby create rings of different shape and velocity.
It has often been argued that these toroidal bubbles are analogous to the familiar smoke rings in air. However, they are much more complex as two distinct fluid phases are involved, namely the liquid medium, and the tubular core of gas. It has been known for over a hundred years that a tube of gas in a liquid should spontaneously collapse and break up through the effect of surface tension instability. That this does not happen for the toroidal tube of the ring bubble can be attributed to the stabilizing influence of the circulation around the tubular core. The centrifugal force of the liquid spinning around the core opposes and balances the collapsing force of the surface tension. For the vortex ring bubble, there is also an upward buoyancy force present but that is balanced by a downward cross-flow force arising from the lateral spread of the spinning core of the ring, analogous to the lateral force on a spinning ball. Thus the ring, once formed, will steadily rise and spread out and thin. However, eventually a point is reached where viscosity dampens the energy of the circulation so that surface tension then dominates leading to breakup of the ring. Despite this, very long lived rings can be created before breakup occurs.
Various U.S. patents document methods of producing vortex rings of different co-mingled fluids. U.S. Pat. No. 3,589,603 by Fohl allows two different fluids to come together in a co-annular nozzle and mix to form a vortex ring. The fluid motions are generated by two moving pistons, but the device does not consider the case of one fluid being a liquid and the other being a gas as would be needed for forming a gas-filled ring bubble. The inventor gives no evidence that the device could produce toroidal ring bubbles. U.S. Pat. No. 5,100,242 by Latto uses a technique in which a moving orifice plate generates a ring vortex that can be used to enhance fluid mixing. The inventor claims it can be used in water to produce aerated rings through seeding of the vortex flow with bubbles, but this is not the same as producing ring bubbles which are single, coherent self-organized structures. These structures require very specialized conditions of pulse flow and pulse duration. One example, U.S. Pat. No. 4,534,914 to Takahashi et al. does provide those conditions and describes a device that uses an accumulator with a diaphragm in one wall that unseats a spring loaded valve when under pressure allowing gas to flow out into a nozzle. The nozzle has a second elastic valve at its exit which is driven open by the pressure it is exposed to following the opening of the spring valve. As the flow exits through the two valves, the pressure in the accumulator falls, both valves close, leaving a gas-filled ring vortex forming at the tip of the second elastic valve. In a second embodiment, they replace the spring-loaded valve with an electrically-driven valve and a pressure sensitive switch on the diaphragm inside the accumulator. This electrically-driven valve allows the gas in the accumulator to flow to, and open the second elastic valve once a predefined pressure is reached. After the flow starts and the pressure in the accumulator begins to fall, the diaphragm moves against the switch to close the electric valve. In a third embodiment, they use a timed pulse to an electrically-actuated valve, but the valve is now placed externally upstream of the accumulator so as to feed gas to the accumulator. Opening the electric valve causes the pressure to start to rise in the accumulator, eventually forcing the second elastic valve open, thereby creating the flow. This flow through the second elastic valve continues even after the electric valve is closed and does not stop until the pressure in the accumulator falls below a certain level so that the second elastic valve will close.
An examination of the devices of Takahashi et al. points out the following operating characteristics:
1. The pressure levels where the valves open and close can not be externally controlled, since these are a consequence of the resilience of the valves and of the valve springs in the first embodiment, or of the diaphragm in the second and third embodiments, as well as the resiliency of the second exit valve.
2. In the first embodiment, a pulsed flow is established, but the duration of the flow is not determined by any external timing pulse, but by the pressure-induced movement of the diaphragm against the resiliency of the spring of the first valve. Likewise, the second embodiment uses an electrically operated valve, but nor is it driven by any external timing pulse. It is also activated and deactivated by the pressure-induced deflection of the diaphragm contacting a mechanical switch. Therefore in both embodiments, the duration of the pulse can not be easily changed without changing the mechanical elements of the device.
3. The third embodiment also uses an electrically operated valve, but the timing of that valve does not directly define the time duration of the pulse flow. Opening the electrically-driven valve merely starts to pressurize the accumulator, and it is that pressure that ultimately unseats the second elastic valve, starting the flow. Further, once started, the electric valve does not, and can not shut off the flow through the second elastic valve since it o
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