Abstract:
A new flash tube device adapted specifically for use with hot erosive flow streams is provided. This flash tube uses an extension cone fixed to the outlet of a choke to create an extension choke to insure that the shock wave occurs within the extension choke, thereby decreasing the flow velocity to a subsonic level, reducing the kinetic energy of the flow as it leaves the extension choke. By moving the shock wave into the extension choke, this device dramatically improves the working life of the flash tank, allowing for easier separation of fluid/solids and vapor in the flash tank.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This patent application is based on U.S. Provisional Patent Application No. 60/218,129 filed on Jul. 13, 2000, co-pending at the filing date of this present patent application and priority is hereby claimed thereto. 
    
    
     BACKGROUND OF INVENTION 
     1. Field of the Invention 
     This invention relates to saturated fluid/vapor flow control devices for use in controlling a flow stream. More specifically, this invention relates to devices for reducing the velocity of the flow as it leaves the choke  100 , thereby improving the working life of system flash tanks and other system components. 
     2. Description of Related Art 
     A variety of devices have been proposed for saturated fluid/vapor flow control. Typically, these prior devices result in significantly increased flow momentum as the flow leaves the choke  100  nozzle at high, even supersonic, velocities. This flow momentum increase found in prior devices typically must be dissipated in a flash tank, where significant wear and tear is induced. 
     SUMMARY OF INVENTION 
     It is desirable to provide a flow control device, described herein as a Flash Tube Device, which has an enlarged expansion cone to both avoid “explosive” flashing of liquid to vapor as well as reducing the kinetic energy or momentum of the flow, thereby improving the working life of hydraulic components, including the flash tank. While generally within this specification the flow is described as a fluid/vapor mixture it should be understood that this mixture may also include solids. For the purposes of this patent disclosure the flow should be interpreted to include an combination of fluids, vapors and/or solids. 
     Therefore, it is the general object of this invention to provide a flow control device that has an extended expansion cone to expand the fluid/vapor mixture to a pressure lower than the pressure in the outlet container. 
     It is a further object of this invention to provide a flow control device that expands the fluid/vapor mixture such that the shock wave occurs within the choke  100 . 
     It is another object of this invention to provide a flow control device that reduces the kinetic energy of the flow as it leaves the choke  100 . 
     A further object of this invention is to provide a flow control device that can be used to match the flow and pressure conditions in the flash tank. A still further object of this invention is to provide a flow control device that can be used to improve the service life of the flash tank and/or allow the flash tank to be made of less expensive materials and/or to be a smaller size. 
     It is another object of this invention to provide a flow control device that improves the efficiency of fluid (combined with solids if present) and vapor separation in the flash tank by reducing the flow energy in the flash tank. 
     These and other objects of this invention are achieved by the device described herein and are readily apparent to those of ordinary skill in the art upon review of this disclosure and/or ordinary experimentation with the device described herein. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 a  is a section view of the preferred flow control device of this invention. 
     FIG. 1 b  is an exterior view of the preferred flow control device of this invention. 
     FIG. 2 is a plot of the pressure drop within the choke  100  as a function of choke  100  position using the preferred embodiment of this invention. 
     FIG. 3 is a plot of the quality of pressure within the choke  100  as a function of choke  100  position using the preferred embodiment of this invention. 
     FIG. 4 is a plot of the kinetic power within the choke  100  as a function of the choke  100  position using the preferred embodiment of this invention. 
     FIG. 5 is a plot of the Mach number of the flow within the choke  100  as a function of the choke  100  position using the preferred embodiment of this invention. 
     FIG. 6 is a plot of the temperature of the flow within the choke  100  as a function of the choke  100  position using the preferred embodiment of this invention. 
     FIG. 7 is a plot of the velocity of sound within the choke  100  as a function of the choke  100  position using the preferred embodiment of this invention. 
     FIG. 8 is a plot of the enthalpies of various constituents in the flow within the choke  100  as a function of the choke  100  position using the preferred embodiment of this invention. 
     FIG. 9 is a plot of the sum of the pressure and momentum flux within the choke  100  as a function of choke  100  position using the preferred embodiment of this invention. 
    
    
     Reference will now be made in detail to the present preferred embodiment of the invention, an example of which is illustrated in the accompanying drawing. 
     DETAILED DESCRIPTION 
     FIG. 1 a  shows a section view of the preferred flow control device (or choke)  100  of this invention. A blast tube  103  defining an expansion cone  107  is provided within a blast tube holder  101  and mounted to the flash tank lid  104 . Holding the blast tube  103  in place is a castable refractory material  102 . The expansion cone  107  extends into a ceramic seat housing  106 . The inlet  109  of the expansion cone  107  receives flow from an inlet tube  108 , which is defined by a ceramic seat  105 . The inlet tube  108  works with the expansion cone  107  to expand the steam within the flow to a pressure lower than the pressure in the outlet container (not shown, but typically mounted to the outlet  110  of the expansion cone  107 ). The steam pressure is lowered thereby sufficiently so that a shock wave occurs within the expansion cone  107  of the choke  100  rather than in a flash tank, which although not shown is typically attached to the outlet  110  of the expansion cone  107 . Across this shock wave, the pressure increases and the velocity of the flow through the choke  100  decreases to a subsonic level. With the shock wave formed in the choke  100 , the kinetic energy of the flow as it leaves the choke  100  is significantly reduced, permitting a match of not only of the outlet pressure but also the other flow conditions within the flash tank. The location of the shock is determined by the equivalence of the sum of the pressure and momentum flux (see FIG.  9 ), where the momentum equations are satisfied for both the supersonic conditions and the subsonic conditions matching the outlet pressure. Thus, the flow is supersonic (see FIG. 5) from the choke  100  throat, or inlet tube  108  until it reaches the shock location. The flow then shocks down to a subsonic rate, and exits the choke  100  at the outlet  110  matching the pressure in the flash tank. In the current preferred embodiment, these components of this invention are constructed using machined fit within the interior of the blast tube  101 . The blast tube  101  is held to the flash tank lid  104  using mechanical fitting. Similarly, the ceramic seat housing  106  is held to the flash tank lid  104  via a mechanical fit. In the preferred embodiment the blast tube holder  101 , the blast tube  103 , the ceramic seat housing  106  and the flash tank lid  104  are constructed of tensile strength steel. While the ceramic seat  105  is made from a suitable heat and pressure resistant ceramic. Alternative materials and mechanical configurations are envisioned and can be substituted without departing from the concept of this invention. 
     FIG. 1 b  is an exterior view of the preferred flow control device  100  of this invention showing the exterior of the blast tube housing  101 . The blast tube housing  101  is shown fixed to the flash tank lid  104 . The exit portion  111  of the ceramic seat housing  111  is shown mounted to the flash tank lid  104 . 
     FIG. 2 is a plot of the pressure drop within the choke  100  as a function of choke  100  position using the preferred embodiment of this invention. Pressure, in bar, is shown on the Y-axis  202 , while position within the choke  100  is shown on the X-axis  201 . From this plot it can be seen that in the preferred embodiment of this invention the shock wave occurs at approximately 17 inches from the choke  100  inlet  203 . 
     FIG. 3 is a plot of the quality of pressure within the choke  100  as a function of choke  100  position using the preferred embodiment of this invention. Quality (as a fraction) is shown on the Y-axis  302 , while position within the choke  100  is shown on the X-axis  301 . From this plot it can be seen that in the preferred embodiment of this invention the shock wave occurs at approximately 17 inches from the choke  100  inlet  303 . 
     FIG. 4 is a plot of the kinetic power within the choke  100  as a function of the choke  100  position using the preferred embodiment of this invention. Kinetic Power, in KW, is plotted on the Y-axis  402 , while position within the choke  100  is shown on the X-axis  401 . Again from this plot it can be seen that in the preferred embodiment of this invention the shock wave occurs at approximately 17 inches from the choke  100  inlet  403 . 
     FIG. 5 is a plot of the Mach number of the flow within the choke  100  as a function of the choke  100  position using the preferred embodiment of this invention. The Mach number is plotted on the Y-axis  502 , while the position within the choke  1000  is shown on the X-axis  501 . Again from this plot it can be seen that in the preferred embodiment of this invention the shock wave occurs at approximately 17 inches from the choke  100  inlet  503 . 
     FIG. 6 is a plot of the temperature of the flow within the choke  100  as a function of the choke  100  position using the preferred embodiment of this invention. The temperature, in degrees Fahrenheit, is shown on the Y-axis  602 , while the position within the choke  1000  is shown on the X-axis  601 . Again from this plot it can be seen that in the preferred embodiment of this invention the shock wave occurs at approximately 17 inches from the choke  100  inlet  603 . 
     FIG. 7 is a plot of the velocity of sound within the choke  100  as a function of the choke  100  position using the preferred embodiment of this invention. The velocity of sound within the choke, in feet per second, is shown on the Y-axis  702 , while the position within the choke  1000  is shown on the X-axis  701 . Again from this plot it can be seen that in the preferred embodiment of this invention the shock wave occurs at approximately 17 inches from the choke  100  inlet  703 . 
     FIG. 8 is a plot of the enthalpies of various constituents in the flow within the choke  100  as a function of the choke  100  position using the preferred embodiment of this invention. The enthalpies, in joules per kilogram, are shown on the Y-axis  802 , while the position within the choke  1000  is shown on the X-axis  801 . Again from this plot it can be seen that in the preferred embodiment of this invention the shock wave occurs at approximately 17 inches from the choke  100  inlet  803 . 
     FIG. 9 is a plot of the pressure plus momentum flux within the choke  100  as a function of choke  100  position using the preferred embodiment of this invention. The momentum flux within the choke  100  is shown on the Y-axis  902 , while the position within the choke  100  is shown on the X-axis  901 . Again from this plot it can be seen that in the preferred embodiment of this invention the shock wave occurs at approximately 17 inches from the choke  100  inlet  903 . 
     It is to be understood that the above-described embodiment of the invention is merely illustrative of numerous and varied other embodiments, which may constitute applications of the principles of the invention. Such other embodiments may be readily devised by those skilled in the art without departing from the spirit or scope of this invention and it is our intent that they are deemed as within the scope of our invention.