Patent Publication Number: US-2003234455-A1

Title: Non-contacting fuel vaporizer

Description:
RELATIONSHIP TO OTHER APPLICATIONS  
     [0001] The present application claims priority from U.S. Provisional Patent Application, Serial No. 60/390,963, filed Jun. 24, 2002. 
    
    
     
       TECHNICAL FIELD  
       [0002] The present invention relates to an apparatus for vaporizing injected fuel; more particularly, to an apparatus for vaporizing fuel injected into a high-temperature region such as exists in a hydrocarbon reformer or an internal combustion engine; and most particularly, to a fuel vaporizing system wherein injected fuel is introduced into a vortex of heated air to both heat the fuel and prevent it from contacting with the apparatus prior to vaporization thereof.  
       [0003] This invention was made with government support under DAAE07-00-3-0004 awarded by TACOM. The Government has license rights in this invention.  
       BACKGROUND OF THE INVENTION  
       [0004] It is well known to inject fuel into internal combustion engines and hydrocarbon reformers. Typically, fuel is introduced as a conical, atomized spray, the objective being to disperse and vaporize the fuel as rapidly as possible such that combustion or catalysis takes place in the presence of fuel vapor rather than liquid fuel.  
       [0005] A known means of achieving this goal is to impinge the fuel against a hot surface (contact vaporization) such as a wall of the vaporization chamber. A drawback of contact vaporization, however, is that rapid introduction of cold fuel onto a hot surface can cause the liquid droplets to bounce off without vaporizing, known in the art as the Liedenfrost phenomenon. Further, droplets which do adhere to a hot surface may decompose by pyrolysis rather than vaporizing, causing buildup of tars and coke and resulting in reduced fuel economy.  
       [0006] It is a principal object of the present invention to vaporize injected fuel in a hydrocarbon reformer or an internal combustion engine while preventing the fuel from striking a hot surface (non-contact vaporization).  
       [0007] It is a further object of the invention to prevent buildup of fuel decomposition products in a hydrocarbon reformer or an internal combustion engine.  
       [0008] It is a still further object of the invention to increase fuel usage efficiency in such devices.  
       SUMMARY OF THE INVENTION  
       [0009] Briefly described, a non-contact fuel vaporization system in accordance with the invention adds heat to the fuel by combining the fuel with heated air in a mixing/vaporization chamber downstream of fuel and air supply inlets. The fuel is metered as an axial spray through a fuel injector and the air is metered through an air director plate that introduces the air in a helical trajectory concentrically around the injected fuel spray. When the hot swirling air comes in contact with the atomized fuel, substantially all of the fuel is vaporized before coming into contact with a wall of the mixing chamber. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0010] These and other features and advantages of the invention will be more fully understood and appreciated from the following description of certain exemplary embodiments of the invention taken together with the accompanying drawings, in which:  
     [0011]FIG. 1 is a schematic cross-sectional view of a first embodiment of a non-contact vaporizer in accordance with the invention comprising a fuel injector, an air director plate, and vaporization chamber;  
     [0012]FIG. 2 is a plan view of the air director plate shown in FIG. 1;  
     [0013]FIG. 3 is a cross-sectional view of the director plate shown in FIG. 2, showing an angled air injection passage;  
     [0014]FIG. 4 is an exploded isometric view, taken from a first direction, of fuel vaporization apparatus in accordance with the invention for use with a hydrocarbon fuel reformer;  
     [0015]FIG. 5 is an exploded isometric view of the apparatus shown in FIG. 4, taken from a second direction;  
     [0016]FIG. 6 is an exploded view like that shown in FIG. 5, showing the addition of metering means for providing heated air to the vaporization chamber in accordance with the invention;  
     [0017]FIG. 7 is an assembled view of the apparatus shown in FIG. 6;  
     [0018]FIG. 8 is a is a schematic cross-sectional view of a second embodiment of a non-contacting vaporizer in accordance with the invention; and  
     [0019]FIG. 9 is a plan view of the air director plate shown in FIG. 8. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0020] Referring to FIGS. 1 through 3, a non-contacting fuel vaporizer  10  in accordance with the invention includes a housing  11  enclosing a vaporization chamber  12 , preferably cylindrical, having side walls  14  and a transverse end wall  16 . Fuel injecting and atomization means  18 , for example, an automotive fuel injector, is disposed axially through end wall  16  for receiving fuel  20  from a source and controllably dispensing the fuel in known fashion as pulses of an atomized and preferably conical spray  22  into chamber  12 . Mounted adjacent end wall  16 , and preferably including end wall  16  as described below, is a gas director plate  24  having a plurality of passages  26  therethrough for receiving a gas  25 , for example, air or steam, from an adjacent annular manifold  28  and injecting such gas into chamber  12  in a plurality of gas jets  30  which join to form a generally cylindrical gas curtain  32  surrounding fuel spray  22 . Fuel spray  22  is thus desirably shielded by curtain  32  from coming into contact with walls  14 .  
     [0021] The number of passages  26  may be varied as desired, although plates having between twelve and sixteen such passages have been found to provide excellent shielding; first embodiment plate  24  in FIG. 2 is shown as having twelve passages  26 , whereas second embodiment plate  24 ′ in FIG. 9 is shown as having sixteen passages  26 , for reasons discussed below.  
     [0022] In currently preferred embodiments of gas director plate  24 , passages  26  are evenly distributed at equal radii and equal central angle spacing about axis  34  of plate  24 . Further, each passage axis  36  preferably is inclined to plate axis  24  by an angle  38  (FIG. 3), for example, 60°, such that curtain  32  is caused to swirl helically as it flows through chamber  12 , causing the injected gas  30  to entrain and mix rapidly with the atomized fuel  22  in an intense, generally annular, mixing zone  40 .  
     [0023] Referring to FIGS. 4 and 5, the elements of non-contact fuel vaporizer  10  are incorporated in a hydrocarbon fuel vaporization assembly  42  for supplying a vaporized fuel/air mixture to a fuel combustor such as a hydrocarbon reformer (not shown). Atomizing means, such as fuel injector  19  is received by a coolant jacket base  44  for injecting fuel through a central opening  46  in a manifold housing  48  containing annular air manifold  28 . Base  44  is secured to housing  48  via bolts  45 . Air enters housing  48  via fitting  47 . A gas director plate  24  mates against housing  48  such that passages  26  are in communication with manifold  28 . Plate  24  forms an end of a cylindrical vaporizing chamber  12  and is sealed thereupon by gasket  51 . Chamber  12  is attached to a plenum  50  receivable of a gas-permeable mixing foam element  52  in known fashion. A spark igniter  54  may be mounted with entrance into plenum  50  for igniting the fuel/air mixture upon reformer startup to provide hot combustion products to rapidly heat the reformer to temperature suitable for steady-state catalysis of the mixture. Clamps  56  are provided for attaching assembly  42  to the reformer. The assembly is bound together by bolts  58  which thread into threaded ears  60  on chamber  12 .  
     [0024] In a currently preferred embodiment of the invention, air  25  entering manifold housing  48  is preheated such that fuel  20  dispensed as conical spray  22  in mixing zone  40  is vaporized virtually instantaneously upon combination with hot air  25 ′.  
     [0025] Referring to FIGS. 1, 6, and  7 , ambient temperature air  25  is supplied to an inlet leg  61  of a T-fitting  62  wherein the air flow may be divided. A bypass air control valve assembly  64  is disposed in a bypass port  66  formed in housing  48  and is connected to a first outlet leg  68  of T-fitting  62 . A second outlet leg  70  of T-fitting  62  is connected via tubing (omitted for clarity) to a heat exchanger  72 , for example, a heat exchanger for heating the air being supplied with fuel/air mixture by non-contact vaporization assembly  42 . Heated air  25 ′ flows back via tubing (not shown) and enters fitting  47  for use in the vaporizer. The flow volume of air through heat exchanger  72  is regulated complementarily by bypass valve assembly  64 , and the valve action may be controlled in known fashion in response to temperature in manifold housing  48  as determined by a temperature probe  74 .  
     [0026] A gas director plate in accordance with the invention may be configured to supply more than one gas to vaporizing chamber  12 . Referring to FIGS. 8 and 9, a second embodiment  24 ′ of a director plate arrangement can distribute both a first gas such as air  25  through first manifold  28  and a second gas  78  through a second concentric manifold  80 . Preferably, manifolds  28  and  80  are interlocking as shown in FIG. 9 such that eight alternate passages  26   a  carry first gas  25  and eight alternate passages  26   b  carry second gas  78 . In an application such as vaporizing fuel for a reformer, providing a second gas can be extremely desirable. Such second gas may be, for example, steam, which can participate in known fashion in the catalytic decomposition of hydrocarbons; or the second gas may be, for another example, spent reformate from the anodes of a fuel cell stack, which serves to recycle combustion water and unconsumed hydrogen.  
     [0027] While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.