Abstract:
The invention relates to a fuel reforming system in which an intensifier is used to pressurize the fuel. An intensifier is a simple device that can be used to step up the pressure provided by a conventional fuel pump. The fuel at increased pressure is passed through a nozzle. As the fuel leaves the nozzle, it atomizes and partially vaporizes. Optionally, the nozzle entrains air through the Venturi effect. Treating the fuel in this manner promotes mixing, increase reformer efficiency, and reduces the formation of byproducts. The invention is particularly suited to vehicle-mounted fuel reformer systems.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to fuel reformers in general and a vehicle-mounted diesel fuel reformer in particular.  
       BACKGROUND OF THE INVENTION  
       [0002]     Fuel reformers can be used to break long chain hydrocarbons into smaller more reactive molecules such as short chain hydrocarbons, oxygenated hydrocarbons, hydrogen, and carbon monoxide. For vehicles, fuel reformers have been proposed for use in connection with fuel cells, to produce low emission combustion fuels, and also as a source of reducing species for regenerating of NOx traps in emission abatement systems.  
         [0003]     U.S. Pat. No. 4,108,114 discloses a compression ignition engine having one cylinder adapted to operate as an on-board fuel reformer. Fuel and air are mixed prior to injection into the cylinder and at least one of these components is pre-heated by either exhaust gas or the reformer product. The reformer product can be supplied to the power cylinders of the engine to reduce emissions.  
         [0004]     U.S. Pat App. No. 2004/0124259 describes a system for producing a fine mist of sub-micron sized fuel particles and suggests using the system in an on-board fuel reformer. The pressurized fuel is heated prior to discharging the fluid into a discharge zone. Prior to discharge, the fuel is heated to a temperature at which the fuel&#39;s vapor pressure exceeds the pressure in the discharge zone. The fuel is preferably heated using a glow plug.  
         [0005]     There remains a long felt need for more efficient fuel reformers that can be used on-board vehicles.  
       SUMMARY OF THE INVENTION  
       [0006]     The following presents a simplified summary in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. The primary purpose of this summary is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.  
         [0007]     One aspect of the invention relates to a fuel reforming system in which an intensifier is used to pressurize the fuel. An intensifier is a simple device that can be used to step up the pressure provided by a conventional fuel pump. The fuel at increased pressure is passed through a nozzle. As the fuel leaves the nozzle, it atomizes and partially vaporizes. Optionally, the nozzle entrains air through the Venturi effect. Treating the fuel in this manner promotes mixing, increase reformer efficiency, and reduces the formation of byproducts. The invention is particularly suited to vehicle-mounted fuel reformer systems.  
         [0008]     To the accomplishment of the foregoing and related ends, the following description and annexed drawings set forth in detail certain illustrative aspects and implementations of the invention. These are indicative of but a few of the various ways in which the principles of the invention may be employed. Other aspects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a schematic illustration of an exemplary fuel reforming system;  
         [0010]      FIG. 2  is an illustration of a nozzle;  
         [0011]      FIG. 3  is an illustration of another nozzle.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0012]      FIG. 1  is a schematic illustration of an exemplary fuel reforming system  10  according to one aspect of the present invention. The fuel reforming system  10  comprises a fuel tank  11 , a fuel pump  12 , a pressure intensifier  13  comprising a piston intensifier  21 , and a reformer  14 . The fuel pump  12  is supplies fuel from the fuel tank  11  at a first pressure. The fuel, optionally combined with water, is drawn into a lower chamber  15  of the piston intensifier  21 . Fuel is then supplied to an upper chamber  16  of the piston intensifier  21 , whereby the fuel acts on the upper surface of a piston  22  to pressurize the fuel in the lower chamber  15 . The intensifier  13  increases the fuel&#39;s pressure over the pressure provided by the fuel pump  12 , typically by a factor of about  3  to about  10 . The pressurized fuel enters the fuel reformer  14  through a nozzle  17 . The fuel and water atomize, mix with air, and partially vaporize as they are expelled from the nozzle  17 . Air can be drawn into the reformer through the nozzle  17  by the Venturi effect. The fuel is further vaporized in a heat exchanger  18  before passing over a reformer catalyst  19 .  
         [0013]     Any suitable fuel can be used, but the invention is particularly adapted to fuels such as gasoline and diesel and for use in vehicle mounted systems. Vehicle mounted systems have constraints as to size and must be able to endure the vibrations inherent in vehicle-mounted systems. The fuel tank  11  is therefore typically a vehicle fuel tank. The fuel pump  12  is generally a commercially available electric fuel pump, typically giving a pressure from about 3 to about 6 bar. The fuel may be supplied from the fuel pump  12  to the intensifier  13  through a pressure regulator  20 .  
         [0014]     A pressure intensifier is a device that takes a working fluid at a first pressure and uses it to pump fluid at a second, higher pressure. The pumped fluid and the working fluid can be one and the same. The elevated pressure is achieved by directing a force generated by the working fluid acting on a first area against the pumped fluid through a second, smaller area.  
         [0015]     A typical pressure intensifier comprises a piston intensifier, such as piston intensifier  21 . The working fluid is supplied to an upper chamber  16  and the pumped fluid is supplied to the lower chamber  15 . The working fluid operates on the large upper cross-sectional area of the piston  22  and compresses the pumped fluid through the smaller lower cross-sectional area of the piston  22 . During filling of the piston with pumped fluid, the pressure in the upper chamber  16  is relieved. In the example, the upper chamber  16  contains fuel that is allowed to drain through control valve  23  to the fuel tank  11 . The middle chamber  24  of the piston  21  can also be vented to the fuel tank  11 . The lower chamber  15  is charged through check valve  25 . Where water is provided, it can be drawn in or pumped in through check valve  26 .  
         [0016]     During the compression stroke of the intensifier  21  the throttle valve  27  is open and the control valve  23  is shut. The pressurize fuel is driven to the nozzle  17  through check valve  28 . A control unit, which may be engine control unit  29 , may control all the valves  23 ,  27 , and  28 . The flow rate of high-pressure fuel may be controlled by varying the stroke length of the piston  21  or by varying the stroke frequency. Optionally, the high-pressure fuel can be stored in a reservoir, whereby a steady flow can be provided to the nozzle  17 . Optionally, the fuel is heated before passing through the nozzle  17 . Any suitable heating system can be used, including for example a heat exchanger or an electrical resistance heater, such a glow plug. Heating can promote atomization and partial vaporization of the fuel as it passes through the nozzle  17 .  
         [0017]      FIG. 2  illustrates an exemplary nozzle  50  and  FIG. 3  illustrates another exemplary nozzle  60 . The nozzle  60  incorporates nozzle holes  61  to control drop size, whereas the nozzle  50  atomizes the fuel solely through the effect of a sudden pressure decrease. Both nozzles can draw in air through the Venturi principle. The nozzle  60  is provided with a passage  62  for this purpose whereas the nozzle  50  is provided with a passage  51 . Optionally, pressurized air can be provided to the passages  62  and  51 . Optionally, air can be supplied to the reformer  14  separate from the nozzle  17 .  
         [0018]     The nozzle  17  can draw in gases to be mixed with the fuel other than, or in addition to, air. Other gases that might be mixed with the fuel include for supply to the fuel reformer include, without limitation, relatively pure oxygen, exhaust, water vapor, and recirculated exhaust from either the reformer or from a fuel cell.  
         [0019]     The reformer  14  can have a mixing chamber  30 . A mixing chamber is a zone, optionally containing baffles, swirlers, or other devices designed to promote mixing of fuel and air. After passing through the nozzle  17 , the fuel is atomized and generally partially vaporized.  
         [0020]     The reformer  14  is provided with an optional heat exchanger  18 . The heat exchanger  18  acts to further vaporize and mix the fuel, as well providing a high temperature for a fuel reforming reaction. The heat exchanger  18  can draw heat from any appropriate source, including for example from engine exhaust, exhaust from the reformer, exhaust from a fuel cell, or a burner. The heat source can pass directly through the reformer or the energy can be first transferred to a heat exchange medium that is passed through the heat exchanger  18 .  
         [0021]     The reformer  14  can be any type of reformer. Reformers can be characterized in terms of the amount and types of oxidant sources supplied and the steps taken to promote reaction. The oxidant source is generally either oxygen or water. Oxygen can be supplied from air, from lean exhaust, or in a relatively pure form, as in oxygen produced from hydrogen peroxide or water. Partial oxidation by oxygen is exothermic and partial oxidation by water in endothermic. A balance between the two can be selected to achieve a desired degree of heat release, heat consumption, or an energy neutral reaction in the reformer  14 . The reformer  14  can promote reaction with one or more of heat, a catalyst, and plasma. Plasma is typically generated with an electric arc. Specific reformer types include steam reformers, autothermal reformers, partial oxidation reformers, and plasma reformers. The invention is applicable to any of these reformers types and provides functions such as reducing byproducts, which may include soot or carbon, and increasing efficiency.  
         [0022]     A reformer catalyst can be any suitable catalyst. Preferably, the reformer catalyst is one that favors the production of CO and H 2  (syn gas) and small hydrocarbons over complete oxidation of diesel fuel to form CO 2  and H 2 O. In particular, the production of relatively large amounts of H 2  is a preferred characteristic of a reformer catalyst. Examples of reformer catalysts include oxides of Al, Mg, and Ni, which are typically combined with one or more of CaO, K 2 O, and a rare earth metal such as Ce to increase activity.  
         [0023]     The reformer catalyst  19  is preferably adapted for use in vehicle exhaust systems. Vehicle exhaust systems create restriction on weight, dimensions, and durability. The reformer catalyst  19  is optionally provided with mechanisms for heating and/or cooling. For example, the catalyst  19  can be permeated with heat-exchange passages. The catalyst  19  can have any suitable structure. Examples of suitable structures may include monoliths, packed beds, and layer screening. A packed bed is preferably formed into a cohesive mass by sintering the particles or adhering them with a binder.  
         [0024]     In one embodiment, the reformer  14  is provided in a vehicle exhaust system. In this embodiment, the high-pressure fuel is injected into an exhaust pipe and reformation takes place with oxygen present in the exhaust. In this case, the heat exchanger  18  would generally not be used. An exhaust pipe is a conduit configured to receive, or adapted to receive, the bulk of the exhaust flow from an engine.  
         [0025]     In another embodiment, the pressure intensifier  13  and the reformer  14  are provided in a single housing. Preferably, the package is designed for mounting on a vehicle, where the package can be coupled to a fuel line and used to produce syn gas. Optionally, the package is part of an auxiliary power system.  
         [0026]     Another embodiment of the invention relates to a power system comprising a fuel reformer system according to the present invention and a fuel cell. The fuel cell can be of any type, but is usually a solid oxide electrolyte fuel cell. The fuel cell uses the reformer product as feed and may be contained with the reformer in a single housing. The fuel cell generally comprises a plurality of cells connected in series. Typically, oxygen is reduced at one electrode to form oxygen ions, which diffuse through the electrolyte and react with reformed fuel on the other side.  
         [0027]     The oxygen electrode of the fuel cell can be a doped ceramic of the perovskite family, for example, doped LaMnO 3 . The electrolyte can be, for example, yttria-stabilized zirconia. The fuel electrode can be, for example, a zirconia-nickel cermet material. A typical operating temperature for the fuel cell would be in the range from about 600 to about 1000° C. The fuel cell can operate at approximately the same temperature as the reformer.  
         [0028]     Optionally, a portion of the reformer product can be recirculated to increase conversion. Recirculation can involve compressing the reformer product and injecting it anywhere upstream of the catalyst  19 . Preferably, the reformer product is recirculated to the mixing chamber  30 . More preferably, the reformer product is drawn by the Venturi effect through the nozzle  17 .  
         [0029]     The invention has been shown and described with respect to certain aspects, examples, and embodiments. While a particular feature of the invention may have been disclosed with respect to only one of several aspects, examples, or embodiments, the feature may be combined with one or more other features of the other aspects, examples, or embodiments as may be advantageous for any given or particular application.