Abstract:
A method of mixing two fluids uses three open-ended tubular sections assembled to define a mixing valve. An axial relationship between two of the tubular sections is defined by the third tubular section. A first fluid is introduced into an annular channel defined by the tubular sections. A flow of a second fluid is introduced along a flow path through the tubular sections. The first fluid is drawn into the flow of the second fluid via holes linking the annular channel to the flow path.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. patent application Ser. No. 14/091,398, filed on Nov. 27, 2013. 
    
    
     FIELD OF THE INVENTION 
     The invention relates generally to mixing valves, and more particularly to a venturi mixing valve assembly that precisely and adjustably mixes two fluids. 
     BACKGROUND OF THE INVENTION 
     Diesel engines configured for bi-fuel operation utilize an air and natural gas mixture along with diesel fuel. The advantages associated with bi-fuel operation include reduced diesel fuel consumption and reduced noxious emissions. 
     Conversion of a conventional diesel engine for bi-fuel operation is readily and typically accomplished by coupling a natural gas supply line to diesel engine&#39;s air intake line. To control the amount of natural gas introduced into the air intake, some type of conventional valve is disposed in the gas supply line. While a simple valve is preferred for robustness and cost, these valves do not typically offer the kind of precise adjustability required for efficient bi-fuel operation at a variety of diesel engine speeds. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a mixing valve for use in controlling an air and natural gas mixture provided to a bi-fuel diesel engine. 
     Another object of the present invention is to provide a mixing valve that allows for precise adjustment of the amount of natural gas introduced into an air and natural gas mixture being provided to a bi-fuel diesel engine. 
     Other objects and advantages of the present invention will become more obvious hereinafter in the specification and drawings. 
     In accordance with the present invention, a method of mixing two fluids uses an open-ended first tubular section having a sleeve defined therein wherein a flow path is defined through the sleeve and an annular channel open on one end thereof is defined between the sleeve and an inner surface of the first tubular section. Also included is an open-ended second tubular section defining an annular region with a plurality of holes and a venturi region coupled to the annular region. The annular region circumscribes at least a portion of the sleeve of the first tubular section and is sealed to the sleeve. An open-ended third tubular section is sealed to an outer surface of the first tubular section and to an outer surface of the second tubular section such that (i) the annular channel is enclosed, (ii) an axial relationship between the first tubular section and second tubular section is defined by the third tubular section, and (iii) at least a portion of the holes define a fluid path between the annular channel and the flow path through the first tubular section. A first fluid is introduced into the annular channel, and a flow of a second fluid is introduced along the flow path through the first tubular section. As a result, the first fluid is drawn into the flow of the second fluid via the portion of the holes defining the fluid path. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects, features and advantages of the present invention will become apparent upon reference to the following description of the preferred embodiments and to the drawings, wherein corresponding reference characters indicate corresponding parts throughout the several views of the drawings and wherein: 
         FIG. 1  is an exploded side view of an adjustable venturi mixing valve assembly in accordance with an embodiment of the present invention; 
         FIG. 2  is an isolated cross-sectional view of the air and natural gas intake portion of the valve assembly taken along line  2 - 2  in  FIG. 1 ; 
         FIG. 3  is an isolated perspective view of the valve assembly&#39;s adjustment ring; 
         FIG. 4  is an isolated perspective view of the venturi portion of the valve assembly; 
         FIG. 5  is an isolated cross-sectional view of the venturi portion of the valve assembly; 
         FIG. 6  is a cross-sectional view of the valve assembly in its assembled configuration with the adjustment ring thereof positioned for the introduction of a gas at the venturi portion of the valve assembly; 
         FIG. 7  is perspective view of a locking bar that can be used to fix the position of the adjustment ring in accordance with another embodiment of the present invention; and 
         FIG. 8  is a plan view of the valve assembly with the locking bar coupled thereto. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, simultaneous reference will be made to  FIGS. 1-6  in order to explain the structure and advantages of the adjustable venturi mixing valve assembly in accordance with an embodiment of the present invention. By way of example, the valve assembly will be explained for its use in a diesel engine configured for bi-fuel operation. However, it is to be understood that the valve assembly could be used in any fluid mixing situation where two diverse fluids/gases need to be mixed together precisely and in adjustable concentrations. 
     The entirety of the valve assembly of the present invention will be referenced generally by the numeral  100 . Valve assembly  100  is an open-ended, flow through valve that includes three open-ended tubular sections, i.e., an intake portion  10 , an adjustment ring  30 , and a venturi portion  50 . For purposes of this description, intake portion  10  serves as an air and natural gas intake when valve assembly  100  is incorporated into a bi-fuel diesel engine as will be explained later below with reference to  FIG. 6 . 
     Intake portion  10  has an open outboard end  12  that receives a flow of air indicated by arrow  200  in  FIG. 1 , and has an open inboard end  14  that will be threadably coupled to one side of adjustment ring  30 . A natural gas supply line (not shown) is coupled to a natural gas inlet  16  formed in an outer wall  18  of intake portion  10 . The shape, size and/or configuration of inlet  16  is not a limitation of the present invention. Inlet  16  is in fluid communication with an open-end annular channel  20  ( FIG. 2 ) defined within intake portion  10 . More specifically, annular channel  20  is defined between an inner surface  18 A of outer wall  18  and an inner cylindrical sleeve  22  concentrically defined within outer wall  18 . Opposite its open end, sleeve  22  terminates in an annular flange  22 A sealed to or integrated with inside surface  18 A of outer wall  18 . An annular slot  23  can be provided in the outer surface of sleeve  22  to receive an o-ring seal (not shown) for reasons that will be explained later herein. 
     Outer wall  18  is threaded on its outside surface (as indicated by reference numeral  24 ) at inboard end  14 . An o-ring seal  26  is provided at the outside surface of outer wall  18  for sealing engagement with an inside surface of adjustment ring  30  as will be explained later below. O-ring seal  26  can rest in an annular slot  28  (shown in  FIG. 2 ) defined in outer wall  18 . 
     Adjustment ring  30  is an open-ended tubular ring having an outer surface  32  that can be partially (as shown) or completely knurled to facilitate the gripping thereof. Other surface finishes or devices could be coupled to outer surface  32  to facilitate the gripping thereof without departing from the scope of the present invention. Outer surface  32  can also include indicia and/or indexing mark(s)  34  for alignment with indexing mark(s) and/or indicia (not shown) on one or both of the outer surfaces of intake portion  10  and venturi portion  50 . Such indicia and/or indexing mark(s) can be calibrated to indicate the concentration of natural gas being supplied into air flow  200  based on the relative position of adjustment ring  30 . 
     The inner surface  36  of adjustment ring  30  ( FIG. 3 ) defines two spaced-apart and independent threaded regions  38  and  40  sandwiched by two smooth annular regions  42  and  44 . Threaded regions  38  and  40  define threads that oppose one another, i.e., one is right hand threaded and the other is left hand threaded. Threaded region  38  is designed to threadably cooperate with threads  24  on intake portion  10 . Threaded region  40  is designed to threadably cooperate with threads  66  on venturi portion  50 . Smooth annular regions  42  and  44  are designed to form a sliding seal fit with o-ring seals  26  and  68 , respectively, when valve assembly  100  is fully assembled. 
     For reasons that will be explained further below, one end (or both ends) of adjustment ring  30  can be provided with through holes  46 . Each hole  46  extends from an end of adjustment ring  30  to outer surface  32 . A line (not shown) such as a wire, a wire tie, a strap, etc., can be fed through hole(s)  46  and “tied” to a nearby stationary fixture to lock adjustment ring  30  in a desired position. However and as will be explained later below, the locking of adjustment ring  30  can be accomplished in other ways without departing from the scope of the present invention. 
     For the illustrated example, venturi portion  50  serves as an air and natural gas mixer. Venturi portion  50  includes an open outboard end  52  and an open inboard end  54  that serves as both the inlet for air flow  200  and the inlet for a flow  202  ( FIG. 6 ) of natural gas. More specifically, inboard end  54  is the end of an annular sleeve region  56  that defines a plurality of through holes  58  (e.g., circular holes as shown, slots, etc.) distributed around region  56 . The size, shape, and number of holes  58  are not limitations of the present invention. The interior of region  56  is sized to circumscribe cylindrical sleeve  22  and form a sliding but sealed fit therewith, e.g., via an o-ring  25  fitted in annular slot  23  ( FIG. 2 ) when valve assembly  100  is assembled as shown in  FIG. 6 . The interior of region  56  terminates in an annular ledge  60  sized in correspondence with the open end of sleeve  22  such that ledge  60  serves as a travel stop. At least a portion of the interior portion of venturi region  50  between ledge  60  and outboard end  52  is shaped to define a venturi  62  that is readily seen in  FIGS. 5 and 6 . The particular features of venturi  62  (e.g., its length, diameter, angular taper, etc.) are not limitations of the present invention. 
     In the illustrated embodiment, venturi  62  terminates in and is integrated with an inside surface  63  of the outer wall  64  of venturi portion  50 . Outer wall  64  is threaded on its outside surface as indicated by reference numeral  66 . An o-ring seal  68  is provided at the outside surface of outer wall  64  for sealing engagement with smooth annular region  44  of adjustment ring  30  ( FIG. 6 ). O-ring seal  68  can rest in an annular slot  69  (visible in  FIG. 5 ) defined in outer wall  64 . 
     In use, valve assembly  100  is assembled as shown in  FIG. 6 . For the illustrated embodiment, an air supply  300  is coupled/sealed to outboard end  12 , a natural gas supply  302  is coupled/sealed to inlet  16 , and outboard end  52  is coupled/sealed to an engine manifold  304  of a bi-fuel diesel engine. Each such coupling/sealing can be accomplished in a variety of ways without departing from the scope of the present invention. Valve assembly  100  allows the natural gas in supply  302  to be maintained at zero pressure as air flow  200  pulls natural gas from annular channel  20  (through any of exposed holes  58 ) into venturi  62 . 
     With valve assembly  100  so installed and assembled, adjustment ring  30  can be rotated to adjust the amount of natural gas drawn into the air and natural gas mixture. More specifically, intake portion  10  and venturi portion  50  are fixed in terms of any rotational movement about their longitudinal axes, while an opposing thread operation is defined between threads  24 /threaded region  38  and threads  66 /threaded region  40  (i.e., one is threaded for left handed operation and the other is threaded for right hand operation). Accordingly, rotation of ring  30  in one direction draws intake portion  10  and venturi portion  50  axially towards one another, while rotation of ring  30  in the opposite direction causes intake portion  10  and venturi portion  50  to move axially away from one another. Note that the amount of axial movement is relatively small and can generally be supported by the mechanical arrangement of air supply  300  and gas supply  302 . Ring  30  is sized/configured such that o-ring seals  26  and  68  remain sealingly engaged with smooth annular regions  42  and  44 , respectively, at all rotational positions of ring  30 . Ring  30  is sized/configured to control the operating range of valve assembly  100 . That is, ring  30  is configured to provide for axial movement of intake portion  10  and venturi portion  50  that, in turn, provides a range of exposure of holes  58  to annular channel  20 . The range of exposure could extend from the complete exposure of all holes  58  to the complete closure of all holes  58  to annular channel  20  (e.g., when ledge  60  abuts the open end of sleeve  22 ). The total number of completely (and/or partially) exposed holes  58  defines a total flow area in fluid communication with air flow  200  moving through intake portion  10 . 
     By way of example,  FIG. 6  illustrates valve assembly  100  with ring  30  positioned such that some of holes  58  are exposed to annular channel  20 . As long as some of (or portions of) holes  58  are exposed to annular channel  20 , natural gas  202  is drawn into channel  20  and through the exposed portions of holes  58 , and then into venturi  62  as air flow  200  moves through venturi  62 . That is, the increase in velocity and pressure drop associated with movement through venturi  62  will draw natural gas  202  through exposed one of holes  58 . Accordingly, natural gas  202  can be maintained at zero pressure. The concentration of natural gas  202  is precisely and readily adjusted by simply rotating ring  30  to thereby expose more/less of holes  58 . The resulting precise mixture of air and gas flows through venturi  62  to outlet  52  for admittance to engine manifold  304 . 
     As mentioned above, a variety of devices/mechanisms could be employed to lock adjustment ring  30  in place to thereby maintain a desired air/gas mixture. For example and as shown in  FIGS. 7 and 8 , the locking of adjustment ring  30  can be accomplished with a locking bar  70  that attaches to intake portion  10  and venturi portion  50 . More specifically, locking bar  70  is a rigid bar that defines a channel  72  that fits over ring  30 . The length of channel  72  allows for axial travel of ring  30  during the rotation thereof on portions  10  and  50 . Locking bar  70  has two holes  74  that receive screws/bolts  76  for threaded coupling to mating holes (not shown) in venturi portion  50 . A slotted hole  80  receives a screw/bolt  82  for threaded coupling to a mating hole (not shown) in intake portion  10 . During adjustment/rotation of ring  30 , channel  72  provides for axial travel of ring  30 . Once the desired rotational position of ring  30  (i.e., indicative of a desired mixture of air and gas) is achieved, a clamping screw/bolt  86  passing through a threaded hole  84  in locking bar  70  is tightened such that the end of screw/bolt  86  bears against ring  30  to lock it in place. 
     The advantages of the present invention are numerous. The mixing valve assembly provides a simple and precise approach to mixing two gases. Since there is no air or gas pressure on the adjustment ring, precise adjustments in gas concentrations are readily achieved. 
     Although the invention has been described relative to specific embodiments thereof, there are numerous variations and modifications that will be readily apparent to those skilled in the art in light of the above teachings. It is therefore to be understood that the invention may be practiced other than as specifically described.