Abstract:
Pressurized fuel vaporizers for engines. Fuel is vaporized under substantial super-atmospheric pressure. Surfaces are heated by the engine&#39;s electrical system. Vapor heated by a wall bounding a vaporization space turbulently mixes with incoming liquid spray, helping to produce new vapor. Useful for cold start, liquid spray reaching a rapidly heated impact plate is vaporized. Multiple heat-transfer surfaces are exposed to the same vapor volume, one, a surface of revolution surrounding the spray, another, a transverse surface across the spray. The spray is in pulses. Glow plugs are arranged perpendicular to heat-distributing members. A volume-surrounding wall receives heat from an annular medium, e.g. an annular conductive plate or an annulus of phase change material, such as low melting point metal, e.g. sodium. Air is shown excluded from the pressure chamber. A fuel vaporizer dedicated to a single combustion region has a cup-shaped vaporization chamber heated by a central heater in opposition to liquid spray. Bottom and side surfaces of the cup are constructed to promote mixing circulation. Liquid fuel injection is synchronized with timing of the engine. In such a system also having a vapor injection valve synchronized with engine timing, the interval between operation of the valves is controlled to enable heat-transfer to vaporize the fuel and build-up pressure. The heating coil of a glow plug is electrically insulated from, but thermally conductively related to, its exterior tube predominantly by fine powdered glass and the exposed stem of the glow plug is pressure-sealed by high temperature seal glass.

Description:
CLAIM OF PRIORITY  
       [0001]     This application claims priority under 35 USC § 119(e) from U.S. Provisional Patent Application Ser. No. 60/550,159, filed on Mar. 4, 2004, the entire contents of which are herein incorporated by reference. 
     
    
     TECHNICAL FIELD  
       [0002]     Systems that transform liquid fuel into fuel vapor to improve combustion in internal combustion engines.  
       BACKGROUND  
       [0003]     The manner in which fuel is provided to an engine significantly affects fuel efficiency and exhaust emissions. In a piston engine with a carburetor, liquid gasoline is introduced centrally to a flow of combustion air, following which the air-fuel mixture is divided and distributed to the engine cylinders. In a piston engine with fuel injectors at the cylinders, pressurized liquid fuel is forced through nozzles of the injectors to inject sprays of liquid fuel particles. The sprays are injected into combustion air at the inlet ports of the cylinders or directly into the combustion regions. Incomplete combustion of the fuel in these and other engines detrimentally affects fuel economy and produces harmful emissions. Over many decades suggestions have been made to pre-vaporize fuel as a way to improve fuel efficiency and decrease emissions of internal combustion engines, but no acceptable solution has been found.  
       SUMMARY  
       [0004]     For a running engine, a vaporization chamber (or vapor chamber) under substantial super-atmospheric pressure has a pulsed, pressurized fuel spray injector spaced from a heated heat-transfer surface. Vapor at pressure, previously produced by spray heated by the heat-transfer surface, recirculates adjacent the injector. The vapor intercepts and turbulently mixes with injected liquid spray. This assists in producing more vapor, while the mixture is heated further by the heat-transfer surface. A vapor passage from the chamber conducts the fuel vapor to the engine in a manner preserving substantial super-atmospheric pressure in the chamber. Thus the vapor density associated with the pressure condition of the chamber helps produce fuel vapor. Time delay and flow conditions between liquid injection into the vaporization chamber and entry of the fuel into a combustion region of the engine can promote mixing of vapor with any residual atomized fuel particles. With fuel such as gasoline it is found that effective vaporization and transport from a central vapor chamber to cylinders of an engine can be produced without use of airflow in the vapor chamber. In other instances, a limited input of pressurized air may facilitate operation. The air can aid in recirculation of the heated vapor and mixing with the injected liquid spray. In either system, the motive power of the introduced liquid spray, itself, can produce strong turbulent mixing action. If air is to be introduced to the vapor chamber, it may be admitted as cross-jets at the nozzle at which the liquid spray emerges to promote atomization of the liquid spray into finer particles.  
         [0005]     In another arrangement, a pressurized vaporization chamber is dedicated to each engine cylinder or other combustion region of the engine. A vapor injection nozzle may be arranged to inject the fuel vapor into the air inlet port of the combustion region or directly into the region. The level of super-atmospheric pressure in the vapor chamber is a function of the energy of the incoming liquid spray, the heated vaporizing action and valving of vapor discharge from the chamber. The valving may be electrically activated in time coordinated with engine timing or may be spring-loaded to be responsive to pressure in the chamber. The value of the super-atmospheric pressure employed depends upon the type of engine involved. In any event, the fuel vapor emerges at pressure sufficient to propel the vapor to its point of utilization in the engine. Embodiments of such dedicated vaporizers operate with air excluded from the vapor generating chamber.  
         [0006]     In some embodiments using a dedicated vapor generating chamber for each combustion region of an engine, a pulse of liquid fuel spray into each combustion region is sized to form a single fuel charge. This liquid spray can be timed in advance of vapor discharge from the chamber to provide an appropriate heating interval. The duration of the interval, the size of the injected liquid pulse, and the timing of vapor discharge is all under control of the engine management computer. In the case of the vaporizer being associated with a cylinder of a reciprocating diesel engine, for instance, the duration of the interval and amount of heating is controlled to produce a substantial pressure build-up in the vaporization chamber. This can enable injection of diesel vapor at very high pressure directly into the combustion region of the diesel cylinder, suitably timed with the beginning of the power stroke.  
         [0007]     In the context of this description, the term “substantial super-atmospheric pressure” in the vaporization chamber refers to pressures at least above 10 psig. It is preferred to employ pressures substantially higher, i.e., pressures in excess of 20 psig, up to about 80 psig for gasoline engines. For vaporization chambers that inject directly into engine cylinders, pressures that are much greater are appropriate. The system may be useful as the sole means of fuel delivery or in combination with other fuel delivery features such as injection of liquid fuel particles into the air system, e.g. for cold start, or into the combustion space, e.g. for diesel engines.  
         [0008]     A vapor-producing arrangement for cold conditions, in a preferred construction, comprises a rapidly heated surface in the vapor chamber, which receives liquid fuel spray to produce initial vaporization.  
         [0009]     In a particularly efficient construction, heat-transfer surfaces for both cold starting and running and for warm running conditions are associated with the same vapor-producing volume. In one construction, a heated heat-transfer surface surrounds the spray, e.g. a cylindrical heated heat-transfer surface surrounds a conical spray from an injector. This heat-transfer surface is located at a sufficient distance from the injector to enable much of the vaporizing action to occur in free-space during warm running conditions. A second heat-transfer surface, extending transversely across the axis of the injector, is located in position to be wetted by initial spray. This second heat-transfer surface is rapidly heated to produce heated vapor to enable operation in cold conditions. In some designs, this second heat-transfer surface can be used for cold starting, cold running and warm running of the engine.  
         [0010]     Heating of the heat-transfer surfaces is preferably electrical. In some designs an electric heater for a heat-transfer surface is isolated from the vapor volume while in other cases it is directly exposed to the fuel.  
         [0011]     Glow plugs (i.e. electric heaters based on resistance heating of a projection such as a tube) are found effective for the vapor generation. Long life glow plugs feature a durable construction. Preferred features include a central resistor predominantly of platinum and an electrically insulative, heat-conductive fine powder substantially comprising glass that fills the space between the resistor element and a surrounding heat-conductive tube. A heat resistant seal of high temperature pressure seal glass.  
         [0012]     In a number of advantageous arrangements a glow plug is employed to heat an intermediate heat-conductive medium which extends from the glow plug to the member defining the active heat-transfer surface. For example, glow plug heating can be employed with an annular heat-conductive medium provided between glow plugs and a cylindrical wall that defines the vaporizing heat-transfer surface. In one instance the annular conductive medium is a conductive metal ring, such as an annular aluminum plate, which is engaged by the glow plugs and in conductive heat-transfer relationship with the wall member. In another instance this annular conductive medium is heat-conductive metal, which may be liquid under operating conditions and the heat associated with the phase change of this metal from solid to liquid and vice versa can serve as a heat sink and produce stable temperature conditions around the annulus.  
         [0013]     Rapid start-up vapor generation is preferably enabled by glow plug heating of a heat-transfer surface defined by a thin, low mass conductive plate wetted by the liquid spray. In embodiments of this feature the glow plug and the plate are both exposed to heat the fuel.  
         [0014]     In some embodiments a heat-transfer surface in the form of a surface of revolution is centered on the axis of a glow plug, extending outwardly from it. This is an advantageous construction for vapor generators dedicated to individual cylinders of an engine. In an advantageous construction the dedicated vapor generator is generally cup-shaped, with a central glow plug protruding at the center toward an aligned liquid spray injector nozzle, the glow plug being exposed for producing vapor and in a heating relationship with the cup bottom, and, via the cup bottom, with the upwardly extending sidewalls of the cup. The cup bottom may be shaped as a deflective surface to guide the flow into a mixing motion. With higher pressures within the vapor chamber, the dimensions of the vapor chamber may be reduced.  
         [0015]     Particular features of fuel vapor systems will now be described.  
         [0016]     One particular feature is a fuel vaporizer for an internal combustion engine, the fuel vaporizer comprising: a closed pressure chamber defining a volume, a heat-transfer surface associated with the volume and arranged to be heated, and a liquid fuel supply system disposed to emit into the volume, under pressure, an expanding pattern of liquid fuel spray from at least one outlet spaced from the heat-transfer surface, the chamber and the liquid fuel supply system being constructed and arranged relative to the heat-transfer surface to establish between the at least one outlet and the heat-transfer surface a mixing domain in which the fuel spray, as it progresses through the volume from the outlet, is substantially heated and vaporized by mixing with recirculated, heated fuel vapor that previously has moved over and received added heat from the heat-transfer surface, the fuel vaporizer being associated with a vapor outflow passage which includes a flow control, the fuel vaporizer constructed and arranged to enable flow of pressurized fuel vapor to the engine while maintaining substantial super-atmospheric pressure within the volume in which vaporization occurs.  
         [0017]     Embodiments of this feature may have one or more of the following features.  
         [0018]     The fuel vaporizer is equipped with an electrical system that comprises a battery and electric source powered by the engine, wherein the heat-transfer surface is heated by electric power from the electrical system.  
         [0019]     The fuel vaporizer is constructed to vaporize liquid fuel in substantial absence of airflow.  
         [0020]     The fuel vaporizer is constructed to vaporize liquid fuel in presence of a limited flow of pressurized air into the pressure chamber.  
         [0021]     The fuel vaporizer includes, as a liquid fuel supply system, a liquid fuel injection system constructed to inject controlled pulses of liquid fuel spray into the volume.  
         [0022]     A liquid fuel supply system is constructed to produce pulses of pressurized liquid fuel flow to the spray system, each pulse of duration of about a second or more.  
         [0023]     A liquid fuel supply system includes a controller to produce pulses of pressurized liquid flow of varying duration and/or frequency in response to fuel vapor demand.  
         [0024]     In a preferred form, a liquid fuel injection system for the vaporizer comprises: a signal pulse generator constructed to produce a series of signal pulses according to the fuel requirements of the engine; a liquid fuel injector; a liquid fuel line connected to receive pressurized flow from an electric fuel pump and to supply the pressurized fuel to the liquid fuel injector, the liquid fuel injector being constructed and arranged, in response to the signal pulses, to produce through the outlet, pulses of diverging spray of liquid fuel.  
         [0025]     The liquid fuel injection system for use with gasoline engines comprises an electric fuel pump constructed to provide liquid fuel for injection into the chamber at liquid pressure in the range of about 60 to 100 psig, and the fuel vaporizer is constructed to maintain pressure in the chamber volume in the range of about 30 to 80 psig, with the pressure of the liquid fuel being substantially greater than pressure in the chamber volume.  
         [0026]     In a carburetor type system constructed to provide fuel vapor to a flow of combustion air, the vaporizer is constructed to maintain pressure in the chamber between about 65 and 75 psi.  
         [0027]     In a gasoline fuel injection system, for instance for injection at the inlet port of a gasoline engine, the vaporizer is constructed to maintain pressure in the chamber between about 40 and 50 psi.  
         [0028]     In embodiments so far described, the vaporizer is constructed to maintain the pressure of the liquid fuel greater than the pressure in the chamber, preferably greater by at least 5 psi, in some cases greater by 10 psi, 15 psi or much more.  
         [0029]     The fuel vaporizer is constructed for association with a single combustion region of an internal combustion engine.  
         [0030]     The liquid fuel injection system for a vaporizer dedicated to a single combustion region of an engine is constructed to inject a controlled pulse of liquid fuel spray into the chamber of the vaporizer in a timed relationship with the engine and in amount suitable to charge the combustion region.  
         [0031]     A fuel vaporizer dedicated to a single combustion region of an engine is constructed to provide liquid fuel at pressure above about 100 psig for injection as a liquid spray into the volume of the vaporizer, in many cases the pressure being above 150 psig.  
         [0032]     The fuel vaporizer is constructed to vaporize diesel fuel and inject diesel fuel vapor for combustion in a diesel cylinder.  
         [0033]     The liquid fuel supply system of the vaporizer is constructed to produce a spray having an axis and the heat-transfer surface is a surface of revolution axi-symmetric with the spray.  
         [0034]     The heat-transfer surface of the vaporizer surrounds the spray, in preferred cases the spray is conical and the heat-transfer surface is substantially cylindrical.  
         [0035]     The heat-transfer surface as a surface of revolution is defined by thermally conductive metal of thickness between about 1/16 to ⅛ inch.  
         [0036]     The heat-transfer surface includes a transverse surface opposed to the spray. Embodiments of this feature have one or more of the following features. The transverse surface is of round form. The heat-transfer surface is effectively cup-shaped, including a transverse surface opposed to the spray and an outer wall portion surrounding the spray. The transverse surface is associated with, effectively, at least one electric heater. The transverse surface is associated with, effectively, at least one glow plug.  
         [0037]     A fuel vaporizer is constructed for association with a single combustion region of an internal combustion engine, and has, effectively, a single glow plug, the glow plug being centrally disposed with respect to the transverse surface, the glow plug being substantially aligned with the spray.  
         [0038]     A transverse heat-transfer surface opposed to the spray has a shape constructed to receive and deflect the spray in a mixing pattern, e.g. the transverse surface is a concave torroidal section.  
         [0039]     The fuel vaporizer is constructed to both vaporize diesel fuel and inject diesel vapor.  
         [0040]     The fuel vaporizer is constructed to both vaporize gasoline and inject gasoline vapor.  
         [0041]     The fuel vaporizer has a heater which is associated with the heat-transfer surface and is exposed for direct contact with fuel in the volume.  
         [0042]     The fuel vaporizer has a heater that is associated with the heat-transfer surface in a manner protecting the heater from contact with fuel in the volume.  
         [0043]     The fuel vaporizer includes a conductive substance that may undergo phase change under operating conditions, which is in contact with a member defining the heat-transfer surface, the substance defining part of a heat-transfer path between a heater and the heat-transfer surface. The substance may be conductive metal that may be melted, e.g. sodium.  
         [0044]     The fuel vaporizer has a heater associated with the heat-transfer surface comprising one or more glow plugs in conductive heat-transfer relationship with the heat-transfer surface.  
         [0045]     A conductive heat-transfer medium extends from at least one glow plug to a member defining the heat-transfer surface.  
         [0046]     A conductive heat-transfer medium extending from a glow plug to a heat-transfer surface is a thermally conductive annular ring surrounding and in thermal contact with the exterior of a wall which on its interior defines the heat-transfer surface.  
         [0047]     The fuel vaporizer includes an electric heater comprising multiple glow plugs spaced apart along a member defining the heat-transfer surface.  
         [0048]     In the fuel vaporizer, a spray produced by the liquid fuel supply system is directed along an axis, and the fuel vaporizer comprises a transverse member defining the heat-transfer surface, the surface being associated with an electrical heater that is powered by an electrical system of an engine and extending across the axis.  
         [0049]     The fuel vaporizer includes a heated heat-transfer surface positioned for impact of liquid fuel spray under cold start conditions to vaporize the liquid, for providing fuel vapor for starting the engine or running the engine cold. In preferred embodiments, this heated heat-transfer surface is positioned for impact of spray is in a conductive heat-transfer relationship with at least one glow plug, for electric heating of the heat-transfer surface.  
         [0050]     The fuel vaporizer has both a first and a second heat-transfer surface associated with respective heaters.  
         [0051]     First and second heat-transfer surfaces are associated with a given volume within the chamber, the first heat-transfer surface being associated with a mixing domain and the second heat-transfer surface being disposed for impact by liquid fuel spray at least under cold conditions to vaporize impacting spray.  
         [0052]     The fuel vaporizer produces an expanding pattern of liquid fuel spray distributed about an axis and a first heat-transfer surface is constructed to surround the spray at a distance spaced from the axis and a second heat-transfer surface extends across the axis of the spray.  
         [0053]     The fuel vaporizer has a second heat-transfer surface that is defined by a perforated member of thermally conductive material.  
         [0054]     The fuel vaporizer has a second heat-transfer surface associated with electric glow plug heating.  
         [0055]     The fuel vaporizer has its vapor outflow passage arranged to discharge into a region of a combustion air conduit associated with an engine, and the flow control is a vapor control valve adapted to be actuated in response to engine power requirements to control flow of vapor into the air conduit. In a preferred embodiment, the region of the combustion air conduit is a venturi region.  
         [0056]     The fuel vaporizer is associated with an internal combustion engine having multiple combustion regions, and the vapor outflow passage of the vaporization chamber is arranged to supply a set of fuel vapor injectors each communicating directly or indirectly with a respective combustion region of the engine, the vapor injectors adapted to be actuated in response to power requirements of the engine.  
         [0057]     The fuel vapor injectors are constructed to discharge fuel vapor to the air inlet port regions of respective combustion regions of the engine or the fuel vapor injectors are constructed to discharge fuel vapor directly to respective combustion regions of the engine.  
         [0058]     The fuel vaporizer is sized and constructed to provide fuel vapor to a single combustion region of an engine having multiple combustion regions, the heat-transfer surface of the vaporizer is effectively cup-shaped including a transverse surface opposed to the spray and an outer wall portion surrounding the spray. Embodiments of this feature may have one or more of the following features. The vaporizer has a glow plug centrally disposed with respect to the transverse surface, the glow plug has an axis, the axis being substantially aligned with an axis of the spray. The transverse surface is radially curved or sloped to receive and deflect the spray in a mixing pattern. The transverse surface is a concave surface of a torroidal section. The valve for vapor flow is a spring-loaded valve constructed to be opened by pressure in the pressure chamber. The valve for vapor flow is constructed to be opened and closed by a timing system of the engine.  
         [0059]     The fuel vaporizer is dedicated to serve one combustion region of an engine having multiple combustion regions, the liquid fuel injection system being constructed to inject controlled pulses of liquid fuel spray into the volume of the vaporizer, each pulse in a timed relationship with the engine and in amount suitable for a fuel charge for the combustion region. Embodiments of this feature may have one or more of the following features. The flow control is a vapor injection valve constructed for operation in a timed relationship with the engine and a control system is adapted to control the interval between each pulse of liquid spray into the vaporizer volume and actuation of the vapor valve. The fuel vaporizer is constructed to produce diesel fuel vapor. The control system is constructed to maintain the interval between injection of liquid spray into the chamber and injection of diesel vapor to assure pressure in the vapor chamber sufficient to enable injection of diesel injection of diesel vapor directly into the combustion region at commencement of the power phase of the combustion chamber.  
         [0060]     Another particular feature is a fuel vaporizer for an internal combustion engine having a combustion region, comprising: a closed pressure chamber defining a volume, a heat-transfer surface associated with the volume and arranged to be heated, and a liquid fuel supply system disposed to emit into the volume, under pressure, an expanding pattern of liquid fuel spray from at least one outlet spaced from the heat-transfer surface, the liquid fuel supply system comprising a fuel injection system constructed to inject the spray in controlled pulses, each pulse synchronized with timing of the engine and in amount suitable for a fuel charge for the combustion region of the engine, the heat-transfer surface being effectively cup-shaped including a transverse surface opposed to the spray and an outer wall portion surrounding the spray, the vaporizer having, effectively, a glow plug that is centrally disposed with respect to the transverse surface, the glow plug having an axis, the axis being substantially aligned with the spray, and a vapor flow control comprising a valve constructed to be opened to deliver fuel vapor for the combustion region of the engine.  
         [0061]     Embodiments of this feature may have one or more of the following features.  
         [0062]     The valve through which fuel vapor is delivered is spring-loaded and constructed to be opened by pressure in the pressure chamber.  
         [0063]     The valve through which fuel vapor is delivered is constructed to be opened and closed by a timing system of the engine. In a preferred form, the vaporizer is associated with a control system adapted to control the interval between each pulse of liquid spray into the volume of the vaporizer and actuation of the valve through which fuel vapor is delivered. The fuel vaporizer is constructed to produce diesel fuel vapor and inject the vapor into the combustion region.  
         [0064]     Another particular feature is a fuel vaporizer for an internal combustion engine equipped with an electrical system that comprises a battery and electric source powered by the engine, the fuel vaporizer comprising: a closed chamber; first and second heat-transfer surfaces associated with the chamber and arranged to be heated, at least the second heat-transfer surface being heated by electric power from the electrical system; and a liquid fuel supply system disposed to emit into the chamber, under pressure, at least one expanding pattern of fuel spray of liquid from at least one outlet, the chamber and the liquid fuel supply system being constructed and arranged relative to the first heat-transfer surface to establish between the at least one outlet and the first heat-transfer surface a vaporizing region in which during running conditions, the fuel spray is substantially heated and vaporized, and the chamber and the liquid fuel supply system being constructed and arranged relative to the second heat-transfer surface to enable, under cold conditions, impact of liquid spray directly upon the second heat-transfer surface, the second heat-transfer surface being arranged to be heated rapidly and constructed to vaporize impacting spray to provide fuel vapor for the engine under cold conditions.  
         [0065]     Embodiments of this feature may have one or more of the following features.  
         [0066]     The liquid fuel supply system is constructed to produce from the at least one outlet a spray pattern distributed about an axis, the first heat-transfer surface being of the form of a surface of revolution surrounding the spray, and the second heat-transfer surface comprising a surface disposed across the axis in opposition to the general direction of progress of the spray.  
         [0067]     The fuel vaporizer has its second heat-transfer surface heated by at least one glow plug energized by the electrical system, in a preferred embodiment the heat-transfer surface being defined by a thermally conductive plate and the glow plug is in thermal contact with the plate.  
         [0068]     The fuel vaporizer includes a control for energizing the glow plug of the second heat-transfer surface only under cold conditions.  
         [0069]     The fuel vaporizer chamber defines a single volume to which both of the heat-transfer surfaces are exposed for vaporizing action.  
         [0070]     The fuel vaporizer is constructed to vaporize liquid fuel during running conditions in substantial absence of air.  
         [0071]     Another particular feature is a fuel vaporizer for an internal combustion engine that is equipped with an electrical system that comprises a battery and electric source powered by the engine, the fuel vaporizer constructed to vaporize liquid fuel in substantial absence of air during running conditions, the fuel vaporizer comprising: a closed pressure chamber defining a volume; first and second heat-transfer surfaces associated with the volume, each heated by electric power from the electrical system; and a liquid fuel supply system disposed to emit into the volume, under pressure, an expanding pattern of fuel spray of liquid from at least one outlet, the chamber and the liquid fuel supply system being constructed and arranged relative to the first heat-transfer surface to establish between the at least one outlet and the heat-transfer surface a mixing domain in which the fuel spray, as it progresses through the volume from the outlet, is substantially heated and vaporized by mixing with recirculated, heated fuel vapor that previously has moved over and received added heat from the heat-transfer surface, the pressure chamber and the liquid fuel supply system being constructed and arranged relative to the second heat-transfer surface to enable, under cold conditions, impact of liquid spray directly upon the second heat-transfer surface, the second heat-transfer surface being constructed to vaporize impacting spray, the fuel vaporizer associated with a vapor outflow passage which includes a flow control, the fuel vaporizer constructed and arranged to enable flow of pressurized fuel vapor to the engine while positive pressure is maintained within the volume.  
         [0072]     Another particular feature is a diesel fuel vaporizer for an internal combustion engine equipped with an electrical system that comprises a battery and electric source powered by the engine, the fuel vaporizer constructed to vaporize liquid diesel fuel, the vaporizer comprising: a closed pressure chamber defining a volume, a heat-transfer surface associated with the volume and heated by electric power from the electrical system, and a liquid fuel supply system disposed to emit into the volume, under pressure, an expanding pattern of diesel fuel spray of liquid from at least one outlet spaced from the heat-transfer surface, the chamber and the liquid fuel supply system being constructed and arranged relative to the heat-transfer surface to establish between the at least one outlet and the heat-transfer surface a mixing domain in which the fuel spray, as it progresses through the volume from the outlet, is substantially heated and vaporized by mixing with recirculated, heated fuel vapor that previously has moved over and received added heat from the heat-transfer surface, the fuel vaporizer associated with a vapor outflow passage which includes a flow control, the fuel vaporizer constructed and arranged to enable flow of pressurized diesel fuel vapor to the engine while maintaining positive pressure within the volume in which vaporization occurs.  
         [0073]     Embodiments of this feature may have one or more of the following features.  
         [0074]     The diesel fuel vaporizer includes an air inlet constructed and arranged to introduce a limited flow of pressurized air into the volume.  
         [0075]     The diesel fuel vaporizer includes a second heat-transfer surface, the pressure chamber and the liquid fuel supply system being constructed and arranged relative to the second heat-transfer surface to enable, under cold conditions, impact of liquid spray directly upon the second heat-transfer surface, the second heat-transfer surface being constructed to vaporize impacting spray to provide fuel vapor for the engine.  
         [0076]     Another particular feature is a fuel vaporizer and vapor injector for an internal combustion engine, comprising: a closed pressure chamber defining a volume, a heat-transfer surface associated with the volume and arranged to be heated, and a liquid fuel supply system disposed to emit into the volume, under pressure and in the absence of air, an expanding pattern of liquid fuel spray from at least one outlet spaced from the heat-transfer surface, the liquid fuel supply system comprising a fuel injection system constructed to inject controlled pulses of liquid fuel spray into the volume, each pulse in timed relationship with the engine and in amount suitable as a charge for a combustion region of the engine, the heat-transfer surface including a transverse surface opposed to the spray and an outer wall portion surrounding the spray, the heat-transfer surface associated with a glow plug to heat the spray and produce fuel vapor, the flow control comprising a valve constructed to be opened in a timed relationship with the engine at an interval following the respective pulse of liquid spray to deliver fuel vapor directly to the engine.  
         [0077]     Embodiments of this feature may have one or more of the various cup-shape and glow plug features described above with respect to dedicated fuel vaporizers, and may be constructed to vaporize diesel fuel.  
         [0078]     Another particular feature is a fuel vaporizer for an internal combustion engine, the engine equipped with an electrical system that comprises a battery and electric source powered by the engine, the fuel vaporizer comprising: a closed pressure chamber defining a volume, at least one heat-transfer surface associated with the volume and arranged to be heated solely by the electrical system of the engine, and a liquid fuel supply system disposed to emit into the volume, under pressure, an expanding pattern of fuel spray of liquid from at least one outlet spaced from the heat-transfer surface, the chamber, the liquid fuel supply system and heating of the heat-transfer surface being cooperatively constructed and arranged to vaporize the fuel to produce fuel vapor under substantial pressure, the fuel vaporizer associated with a vapor outflow passage which includes a flow control, the fuel vaporizer constructed and arranged to enable flow of pressurized fuel vapor to the engine while maintaining substantial super-atmospheric pressure within the volume in which vaporization occurs.  
         [0079]     Embodiments of this feature may have one or more of the following features.  
         [0080]     The fuel vaporizer is constructed to vaporize liquid fuel in substantial absence of airflow.  
         [0081]     The fuel vaporizer is constructed to vaporize liquid fuel in presence of a limited flow of air into the pressure chamber. The air may be injected under pressure in a manner to promote atomization of the spray of liquid.  
         [0082]     Another particular feature is a fuel vaporizer having a heat-transfer surface defined by a transversely extending heat-conductive member having a general direction of extent, and at least one electrically energizeable glow plug having its heated portion in intimate thermal contact with the conductive member, the axis of the glow plug being generally perpendicular to the direction of extent of the heat-conductive member.  
         [0083]     Embodiments of this feature may have one or more of the following features.  
         [0084]     The fuel vaporizer has a vapor-producing heat-transfer surface that comprises the inside surface of a wall member in the form of a surface of revolution, and the transversely extending heat-conductive member comprises an annular member surrounding and in thermal contact with the wall member.  
         [0085]     The fuel vaporizer has a transversely extending heat-conductive member which extends transversely to the direction of a spray of fuel from an injector. In one embodiment the member comprises a thermally conductive plate. In another embodiment the transversely extending member defines a bottom portion of a cup-shaped fuel vaporization chamber. In another embodiment the heat-conductive member is shaped to assist in guiding flow into a recirculating pattern of mixing action.  
         [0086]     Another particular feature is a glow plug comprising an internal electrically resistive heater in the form of an elongated helical coil of a platinum alloy, an elongated, closed end outer tube of heat resistant metal defining an internal cavity in which the resistive heater coil resides, and a thermally conductive, electrically insulative filler within the tube comprised substantially of fine glass powder, insulating the heater electrically from the tube while forming a thermal conductive path therebetween. In one embodiment an outer end of the resistive heater coil is connected to a terminal member, the terminal member being sealed to outer structure of the glow plug by high temperature pressure seal glass.  
         [0087]     The details of selected designs are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. 
     
    
     DESCRIPTION OF DRAWINGS  
       [0088]      FIG. 1  is a cross-sectional diagram of a mixing chamber for vaporization of fuel.  
         [0089]     FIG  1 A is a partially broken away diagrammatic, perspective view of active parts of a fuel vaporizer.  
         [0090]      FIG. 2  is a cross-sectional diagram of an impingement arrangement for vaporization of fuel under cold start conditions.  
         [0091]      FIG. 2A  is a diagrammatic perspective view of active parts of a fuel vaporizer.  
         [0092]      FIG. 3  is a cross-sectional diagram of a vaporizer for delivering an air and fuel vapor mixture to an engine.  
         [0093]      FIG. 3A  is a cross-sectional diagram of a rotary valve of the vaporizer of  FIG. 3 .  
         [0094]      FIG. 4  is a cross-sectional diagram of a system that includes the vaporizer of  FIG. 3  and additional components.  
         [0095]      FIG. 5  is a cross-sectional diagram of another vaporizer for delivering an air and fuel vapor mixture to an engine.  
         [0096]      FIG. 6  is a cross-sectional diagram of another vaporizer for delivering an air and fuel vapor mixture to an engine.  
         [0097]      FIG. 7  is a circuit diagram of the pulse controller of the system of  FIG. 4 .  
         [0098]      FIG. 7A  is a diagram of a pulse train generated by the pulse controller of  FIG. 4 .  
         [0099]      FIG. 8  is a cross-sectional diagram of a vaporizer for delivering fuel vapor to a fuel vapor-injected engine.  
         [0100]      FIG. 8A  is a cross-sectional diagram of a variant of the vaporizer of  FIG. 8 .  
         [0101]      FIG. 8B  is a view similar to  FIG. 8A  of another embodiment while  FIGS. 8C and 8D  are respectively plan views of the top and bottom plates of the vaporization chamber.  
         [0102]      FIG. 9  is a cross-sectional diagram of a system that includes the vaporizer of  FIG. 8  and additional components.  
         [0103]      FIG. 9A  is a view similar to  FIG. 9 , of a system that includes additional features.  
         [0104]      FIGS. 9B and 9C  are diagrammatic end and plan views respectively of a V-8 engine employing a fuel vaporizer, fuel vapor injection, and cold start liquid fuel injection.  
         [0105]      FIG. 9D  is a diagrammatic cross-sectional view of a fuel vapor injector while  FIG. 9E  is a similar view of a cold start liquid fuel injector.  
         [0106]      FIG. 9F  is a partial cross-section diagrammatically depicting the relationship of a fuel vapor injector to its supply rail.  
         [0107]      FIGS. 9G-1  through  9 G- 4  depict respectively the strokes of a four-stroke gasoline engine employing a fuel vapor injector at its air inlet port.  
         [0108]      FIG. 10  is a cross-sectional diagram of a vaporizer for delivering diesel vapor to a diesel engine.  
         [0109]      FIG. 10A  is a cross-sectional diagram of another diesel vaporizer.  
         [0110]      FIG. 11  and  11 A are side cross-section and horizontal cross-sections of a vaporizer combining impingement and mixing actions in producing fuel vapor.  
         [0111]      FIGS. 12 and 12 A, and  FIGS. 13 and 13 A are views similar to those of  FIGS. 11 and 11 A of other embodiments.  
         [0112]      FIG. 14  is a diagrammatic cross-section, similar to  FIG. 9D , of a fuel vapor injector that incorporates its own fuel vaporizer.  
         [0113]      FIG. 15  is a diagram depicting injection of fuel vapor into the air inlet port of a cylinder of an engine.  
         [0114]      FIG. 16  is a view similar to  FIG. 14  of another embodiment of a combined fuel vaporizer and vapor injector.  
         [0115]      FIG. 17  is a diagram depicting injection of fuel vapor directly into a cylinder of an engine.  
         [0116]      FIG. 18  is a schematic diagram of the fuel supply arrangement for a diesel engine employing the device of  FIG. 16 .  
         [0117]      FIGS. 19A through 19D  illustrate the four strokes of a conventional diesel engine.  
         [0118]      FIG. 20  is a magnified side-view of a glow plug useful in the embodiments shown, while  FIG. 21  is a cross-sectional view of greater magnification of the tube, insulation and heating element of the glow plug, and  FIG. 22  is a cross-sectional view of the connection of the stem of the glow plug to the mounting body. 
     
    
       [0119]     Like reference symbols in the various drawings indicate like elements.  
       DETAILED DESCRIPTION  
       [0120]     Referring to  FIG. 1 , a vaporization chamber  10  vaporizes liquid fuel in a volume  12 . This vaporization is a process whereby liquid fuel particles are converted to a gas state in which very finely divided residual particles may also be suspended. For instance the lighter components of liquid fuel particles may be totally transformed to gas while the heavier components are partially transformed to gas with residual exceedingly small particles as in a fine fog, that present a large aggregate surface area that enables rapid heating and combustion in the engine.  
         [0121]     A closed pressure chamber that includes cylindrical wall  14  and end walls  15 ,  17 , defines the volume  12 . The cylindrical wall  14  is heated by an external heat source, as indicated by the arrows. The liquid fuel  16  arrives at the chamber  10  from a pressurized source and enters the volume  12  in pulses through an injector  18 . The injector  18  sprays the liquid fuel into the volume  12  at pressure through one or a set of small holes. The injector  18  breaks up the liquid fuel into spray, initially forming a cone or other desired spray pattern about an axis A l . The radius R of chamber  10  is sufficient to define an open space in which the spray traveling through the volume  12  is subjected to an energetic mixing and heating action by contact with recirculated, heated fuel vapor that previously has moved over wall  14  and received added heat. The fuel vapor fills exit channel  20 . An outlet system, diagrammatically indicated at  22 , controls the exiting flow rate of the fuel vapor. The fuel flow rate through the injector  18 , the heating and vaporization action, and the flow-restrictive effect of the outlet system  22  determines the pressure of the vapor inside the volume  12 . Under normal operating conditions, injection pressure P of the liquid fuel entering the injector  18  is greater than pressure P 1  of the fuel vapor inside the volume  12 , while the pressure P 1 is maintained substantially above atmospheric pressure.  
         [0122]     In manner described later, see  FIGS. 7 and 7 A, flow of fuel is produced in pulses of pulse width and frequency to meet the fuel demand, advantageously with pulse width in excess of one second.  
         [0123]     In the system shown, during normal operating conditions there is substantial absence of air in the volume  12 .  
         [0124]     In one example, radius R of the chamber is in excess of 1 inch but less than 3 inches, for instance 1¼ inch, while the height H of the chamber is in excess of 3 inches but less than 8 inches, for instance 5 inches.  
         [0125]     Details of an example of a vaporizer unit constructed to operate according to the principles of  FIG. 1 , are shown in  FIG. 1A . A cylindrical wall member  60  defines an inner, cylindrical heat-transfer surface S that, together with end walls, bounds a region into which liquid spray L is emitted. Wall member  60  is formed of a continuous sheet of aluminum, of 1/16 inch thickness. The cylinder  60 , for instance, may have a diameter of 2½ inch. On the exterior of wall member  60  is a thermally conductive annular heat distribution member  62  in thermal contact with the wall member  60 . An array of electric glow plugs G is associated with the annular heat distribution member  62 . The heat distribution member is constructed and arranged to provide both radial and circumferential heat-conductivity paths H, enabling the glow plugs G to efficiently heat strategic regions of the wall member. Surface S of the heated wall member in turn heats vapor that passes over that surface. In the embodiment shown, annular heat distribution member  62  is of flat disk form, of aluminum plate of ⅛ inch thickness. The plane of the plate  62  lies perpendicular to the axis A 1  of the cylinder. The plate  62  is in thermal contact with the exterior of cylindrical wall member  60  at a location spaced from the ends of member  60 . This thermal contact is accomplished for instance by press fit or welding. At selected locations about the annular heat distribution member  62 , electrically powered glow plugs G are disposed in thermal contact with distribution member  62 . The axis of each glow plug G is perpendicular to the plane of the plate  62  and the most heated portion of each glow plug G is disposed in a depression or hole formed in the plate  62 , in thermal contact with the substance of the plate  62  as by a press fit. In the example shown, there are three glow plugs G equally spaced about the periphery of wall member  60 .  
         [0126]     The glow plugs G are connected to the electrical system of an automotive engine, as shown. When the vaporizer unit is constructed for running conditions of the engine, the glow plugs may be selected each to draw 5 amps from a 12 volt electrical system. The glow plugs are intended to be cycled on and off, simultaneously or one at a time, in response to an appropriate control system. The control system may employ thermal sensors to monitor the thermal status, and may be supplemented by a pressure control system, to monitor the pressure within the vaporizer. By such an arrangement, the glow plugs are energized to meet the vapor demand. The glow plugs G may be energized simultaneously with activation of the cold start system or energization may follow activation and turn off of the cold-start system. The initial phase of warming wall member  60  may continue until the unit reaches operational conditions. Then, in a second phase, the glow plugs may be energized from time to time in accordance with vapor demand. In some examples the set of glow plugs G may be energized simultaneously or they may be energized sequentially about the array to reduce the instantaneous power demand on the electrical system to one glow plug at a time.  
         [0127]     A feature of this construction is that the thermal mass of thin wall member enables relatively quick warm up while enabling efficient electrical operation during running condition. Further features that may be included are shown in broken lines at the bottom of  FIG. 1A  and will be described following the description of  FIGS. 2 and 2 A.  
         [0128]     A construction similar to that of  FIG. 1A , that is suitable for mass production, may be formed as an integral casting, e.g. of aluminum, into which a heating device equivalent to glow plugs is incorporated. Details of the construction may be adapted to accommodate differences in thermal expansion that may occur, which may depend upon variations in time and location of the heating. For example, flexible regions serving as expansion joints may be provided. For higher temperature operation, material suitable for higher temperature may be employed, for instance high temperature stainless steel alloy such as Inconel 617.  
         [0129]     Referring to  FIG. 2 , another vaporization system transfers heat from a rapidly heated transverse plate  54  located within pressure chamber  50 . Cylindrical wall  56 , end walls  57  and end plate  54  enclose vapor volume  52 . Injector  58  that sprays liquid fuel through one or a set of small holes injects pressurized liquid fuel. The spray from the injector  58  proceeds, for instance, in a cone symmetric about an axis A 2 . Heated transverse plate  54  extends across the axis A 2 , in the case shown being perpendicular to axis A 2 .  
         [0130]     In the example, using the construction illustrated in  FIG. 2 , the plate is positioned to serve during cold start conditions as an impact plate upon which liquid fuel impacts, wetting the plate  54 . In this case, the components of the vaporizer unit are chosen such that vaporization occurs directly at plate  54  during cold start. Under cold start conditions the position of plate  54  relative to injector  58  enables the plate to intercept central portions of the liquid spray. The liquid fuel is vaporized by the rapidly heated plate  54 , the vapor filling volume  52  and exit channel  62 . An outlet system, diagrammatically indicated at  64 , controls the exiting flow rate of the fuel vapor such that the pressure of vapor inside the volume  52  is P 2 . Liquid fuel is supplied in one or more pulses to the injector. The source of liquid fuel  60  keeps the pressure P above P 2  at times of spray injection to produce the flow through the injector.  
         [0131]     For a vaporizer supplying fuel vapor to an automotive engine, advantageously the volume of the chamber  52  for cold start may also serve as the vaporizing space  12  of chamber  10  of  FIG. 1  for running conditions. In other examples, the vaporization system includes separate volumes  12  and  52 , in which the vaporization chamber  50  is used during cold start conditions while the vaporization chamber  10  is used for warm running conditions, in which case the volumes can communicate so that vapor produced in the cold start volume fills the running condition volume, to assist in initiating running conditions, and the cold start volume may serve for additional vapor storage during running conditions.  
         [0132]     Details of an example of a vaporizer unit constructed to operate according to the principles of  FIG. 2  are shown in  FIG. 2A . A transverse conductive heat distribution member  70  having a generally continuous surface is disposed within the bounds of an enclosing wall member  72 . The wall member may be the cylindrical wall  60  of  FIG. 1A , or a wall member of different construction or configuration. In the embodiment shown, heat distribution member  70  is a flat aluminum plate of 1/16 inch thickness of circular configuration, the plane of the plate lying perpendicular to the axis A 2  of the cylindrical wall. Plate  70  has its peripheral region in thermal contact (i.e. with thermal conduction continuity) with the interior of the wall member as by press fit, welds, or otherwise. Plate  70  is spaced from the ends of the wall member to define an additional vapor volume  55  that communicates with volume  52  via flow passages such as holes  53  provided in plate  70 .  
         [0133]     At selected locations inwardly from the periphery of the transverse heat distribution plate  70 , electrically powered glow plugs G 1  are disposed perpendicular to and in thermal contact with the plate  70 . For instance, the heated portion of each glow plug G 1  is press fit within a depression or hole formed in the plate  70 . In the example shown, there are two glow plugs G 1  spaced equally from each other and from the periphery of transverse member  70 . In this example, the body of the glow plugs extends upward from the bottom, through the auxiliary vapor space  55 , the side surfaces of the glow plug bodies that receive heat from the glow plug resistive element being exposed to vapor in space  55 .  
         [0134]     The glow plugs G 1  are connected to the electrical system of an automotive engine and may be selected each to draw 5 amps from a 12 volt electrical system. When such a unit is constructed for cold start of the engine, the member  70  is located relative to liquid spray injector  18  to receive liquid spray L upon its surface during cold start conditions. For use in start-up mode, the two glow plugs G 1  may be energized upon activating the ignition switch of the engine, and then de-energized quickly, e.g. within 3 to 5 seconds, as the vaporizer reaches an appropriate vapor-filled condition. Control of injection and heating may be accomplished with an appropriate control system. The vaporizer may employ thermal sensors to monitor the thermal status and a pressure sensor to monitor the pressure within the vaporizer. This vaporizer arrangement enables the cold start vaporizer action of the embodiment of  FIG. 2  to begin. The active portion of this construction has low thermal mass, enabling rapid, electrically efficient start-up. After start-up, the glow plugs in transverse member  40  may be de-energized to hand off the vaporizing action to another system, for instance the system of  FIG. 1A . The heating of the surrounding member may thus initially be accomplished by the glow plugs G 1  of the transverse wall member, and after hand-off by the glow plugs G heating the annular member of  FIG. 1A . In another system, in which the electrical system is sufficiently robust, both sets of glow plugs G and G 1  are energized at start-up, with the cylindrical wall being rapidly heated and serving as an additional liquid impact surface at start-up, for surface evaporation.  
         [0135]     With further reference to  FIG. 1A , in some cases, after its initial use in cold start, the glow plugs G 1  of the transverse member  40  may be periodically heated, e.g. in sequence with the glow plugs G of the embodiment of  FIG. 1A , so that the surface of transverse member  70  may participate in the vaporizing action described with respect to  FIG. 1 . Even with the glow plugs in member  70  de-energized, the surface of member  70 , via its thermal contact with the cylindrical wall member, may be adapted to play a role in heating vapors or maintaining their heated condition.  
         [0136]     A construction similar to the embodiment of  FIG. 2A , suitable for production, may be formed of as a unit, for instance an integral metal casting, e.g. of aluminum, into which a device equivalent to glow plugs is incorporated. In another case, a unit combining both the annular heat distribution feature of  FIG. 1A  and the transverse member feature of  FIG. 2A  may be combined in a single unit such as on aluminum casting.  
         [0137]     In a variation, the transverse member  70  of  FIG. 2A  may be adapted to provide the principal vaporization action according to the principles of both  FIG. 2  for cold start, and  FIG. 1  for running operations.  
         [0138]     Referring to  FIG. 3 , a vaporizer  100  includes essential features of both chambers  10  and  50 , of  FIGS. 1 and 2 . In addition to the vaporizing volume  104 , the vaporizer  100  includes vapor storage volume  120  that communicates with a delivery passage  125 .  
         [0139]     The vaporizer  100  replaces a carburetor of a gasoline engine by supplying gasoline fuel vapor to combustion air for the engine. The engine includes an electrical system that includes a battery associated with a generator or alternator, the system capable of supplying electrical power at startup and during running conditions. The vaporizer  100  can be referred to as a throttle body fuel system or single point or central fuel system. The vaporizer  100  can be constructed to be a bolt-on replacement for the carburetor, so a conventional engine design normally using a carburetor does not require significant modification to receive the vaporizer  100 .  
         [0140]     The vaporizer  100  includes a liquid fuel injector  102  that sprays the liquid into the volume  104  at a pressure through one or a set of small holes. In one example, the liquid fuel injector  102  has a single hole orifice of about 0.001 inch in diameter. The injector  102  is electronically controllable such that an electrical “ON” signal opens the liquid supply passage while an electrical “OFF” signal shuts the passage. The spray from the injector  102  forms a cone of spray about an axis. In some examples, the cone of spray forms about a ninety degree apex angle. The vaporization volume  104 , during warm running conditions, contains recirculating fuel vapor that is heated as it reaches and flows over the surface of cylindrical wall  106  in a turbulently recirculating flow. Similarly to the process illustrated in  FIG. 1 , the vaporizer  100  vaporizes the spray of liquid fuel from the injector  102  by energetic turbulent mixing of the high velocity liquid fuel spray with recirculated, heated fuel vapor that previously has moved over and received added heat from the wall  106 . During warm running conditions, the temperature in the volume  104  is maintained at a temperature corresponding to the vaporization temperature of the fuel under operating conditions. The particular temperature depends upon the vaporization temperature of a volatile fraction that makes up the fuel selected as well as the particular positive pressure range selected for operation of the vaporizing volume. In one example, the temperature in the volume  104  may be maintained at 168° F.  
         [0141]     The cylindrical wall  106  is heated, through heat-transfer, by glow plugs  108 A and  108 B, powered by the electrical system of the engine. There may be for instance three glow plugs symmetrically located about the cylinder. Glow plugs operable in this application, manufactured by Bosch are available from Mercedes-Benz USA, LLC of Montvale, N.J. as part number 001.159.2101. These glow plugs can readily achieve temperatures of about 300° F. at their tips, and see  FIGS. 20-22 , below. In other examples (not shown), additional glow plugs may be used to heat the cylindrical wall  106 . The glow plugs  108 A,  108 B are located in an annular space  112  defined on the inside by wall  106  and on the outside by spaced-apart cylindrical wall  114 . The glow plugs  108 A,  108 B transfer thermal energy to the wall  518  using an annular, thermally conductive metal ring  110 , with which there is good thermal conduct, e.g. by press-fit. An insulating space  115  is produced between the outer periphery of annular ring  110  and the surrounding housing to reduce heat loss to the exterior.  
         [0142]     The cylindrical walls  106 ,  114  rest on a bottom plate  116  and a top plate  118  encloses the space. The central volume  104  communicates with storage volume  120  through the top plate  118  via a circular hole, and with vapor storage space  155  below transverse plate  154 . The parts  106 ,  114 ,  116 ,  118  and  154  are made of thermally conductive metal, e.g. of aluminum. The plates  116 ,  118  enclose the annular space  112  by sealing against the cylindrical walls  106 ,  114 . For example, sealing is by silicone rubber O-rings or by suitable gaskets. In an example, the cylindrical wall  106  is ⅛ inch thick while the central volume  104  is 2¼ inch in diameter. The storage volume  120  is defined between the plate  118  and an additional top plate  121 . The top plate  121  seals the storage volume  120  e.g. by a silicone rubber o-ring or a suitable gasket.  
         [0143]     As fuel vapor is produced in volume  104 , it fills the volume  120 . Fuel liquid from fuel supply  122  is supplied under elevated pressure from an electric fuel pump via fuel line  124  to the injector  102 . During warm running conditions, for liquid fuel injection, the pressure in the volume  104  is lower than in the fuel line  124 , but higher than atmospheric pressure. In some examples, the liquid in the fuel line  124  is at a pressure between about 60 to 100 pounds per square inch above atmospheric, i.e., gauge pressure (psig), while pressure of the vapor in the volume  104  is between about 30 and 80 psig at times of injection, with a substantial pressure differential between the pressures at times of injection. For example, the liquid in the fuel line  124  is at 88 psig and the pressure of the vapor in the volume  104  is 70 psig.  
         [0144]     Generally, for use with a carburetor system, it is preferred that the pressure in the chamber be maintained between about 65 and 75 psig and in a fuel injection system between about 40 and 50 psig, with the pressure of the liquid fuel being greater than the pressure in the chamber, preferably greater by at least 5 psi, in some cases greater by 10 psi, 15 psi, or more.  
         [0145]     The fuel vapor moves from volume  120  through a flow restrictor  160  to a vapor channel  125 . The flow restrictor  160  has one or more holes of about 1/16 inch in diameter to constrict the flow of vapor and hold the pressure in the volume  120 . It preferably has an adjustment feature. The purpose of the flow restrictor  160  is to limit vapor flow such that pressure is maintained in the pressure chamber  104 ,  120  even at “full throttle” so as to preserve proper operation of the vaporizer  100 . The fuel vapor moves from the vapor channel  125  to an air intake passage  130 , which may be shaped as a venturi passage in the usual way (not shown), with the outlet to the air passage located at the low pressure region of the venturi passage.  
         [0146]     The flow rate of fuel vapor into an air/vapor mixing region of the air intake passage  130  is further controlled by a rotary valve  132 , formed by a rotary central member having a flow slot  133 ,  FIG. 3A . Air into the air intake passage  130  passes through an air filter  134 , while airflow is controlled by a butterfly valve  136 . An additional butterfly valve  138  controls the flow of the air/vapor mixture from the air intake chamber  130 . The rotary movements of the butterfly valves and the rotary valve  132  are produced by axial movement of an accelerator rod  140  and appropriate linkage diagrammatically suggested in  FIG. 3 . Adjustment features are provided in this linkage.  
         [0147]     Air/vapor mix exiting from the air intake passage  130  enters an air intake manifold of engine  152  via passage  150 .  
         [0148]     During startup of the engine  152 , the vaporizer  100  is typically cold so that there is no preexisting warm fuel vapor in volume  104 . During startup, plate  154 , to serve as an impact plate, is rapidly heated and used to vaporize liquid spray from the injector  102 . This follows the techniques described with respect to vaporization chamber  50  ( FIG. 2 ). The plate  154  is thermally conductive metal, preferably aluminum, and of low thermal mass. In one example, the plate  154  is a 1/16 inch thick with 1/32 inch holes through the thickness of the plate  154 . In other examples, plate  154  can be ⅛ inch thick. The holes enable vapor or fluid to pass through the plate  154 . A volume  155  below the plate  154 , adds to the vapor storage capacity of the system. A glow plug  156 , powered by the electrical system of the engine, extends upwardly from the bottom of the chamber, through space  155 , to heat the plate  154 . A heated length of the glow plug body, adjacent to the plug tip, serves as a heat-transfer surface in space  155 , its heated length, heated by the glow plug, providing heat to that region. The glow plug  156  is turned on during the cold startup period and then turned off by the control circuit. In other examples, one or more additional glow plugs can be used to heat plate  154  for vaporizing impacting liquid, or to otherwise form a surface for vaporizing the fuel.  
         [0149]     For sensing temperature within the vaporizer, in this example a thermocouple  158  measures the temperature of plate  154 . During running conditions, with glow plug  156  turned off, a controller (not shown) uses feedback from the thermocouple  158  to control the glow plugs  108 A,  108 B to maintain a specific temperature within design range in the volume  104 . The controller may use proportional, derivative, and integral linear control rules to maintain the temperature in the volume  104 . Other known temperature control systems may be employed.  
         [0150]     Referring to  FIG. 4 , a vaporization system  200  includes the vaporizer  100  of  FIG. 3 . The liquid fuel supply  122  includes fuel tank  202 , electric fuel pump  204 , fuel filter  206 , and fuel pressure regulator  208 . Liquid fuel from the fuel tank  202  is pumped by fuel pump  204  through fuel filter  206  and through fuel pressure regulator  208  to arrive at the injector  102  under pressure. The vaporization system  200  also includes a pulse generator  210  capable of generating pulses to turn the injector  102  off and on. A computer  212  controls the frequency and width of pulses generated by the pulse generator  210 . The frequency and width of the pulses relates to the desired power demands on the engine  152 . The computer  212  also receives feedback from thermocouple  158  to control activation of glow plugs  108 A,  108 B according to appropriately established control rules during running conditions. The engine  152  includes an intake manifold  214  that supplies the air/fuel vapor mixture to cylinders  216 A,  216 B,  216 C, and  216 D. In other examples, the engine  152  of course may have a different number of cylinders and other configurations.  
         [0151]     Referring to  FIG. 5 , a vaporizer  300  includes many features of the vaporizer  100  including the thermally conductive plate  154  extending across the central axis of the wall  106 , which is in thermal contact with the wall  106 . The vaporizer  300  also includes a vapor storage volume  302 . The vapor storage volume  302  is connected to the volume  120  by an open passage (not shown). During cold start conditions, the vaporizer  300  operates in a similar fashion to that of the vaporizer  100 , using the glow plug  156  to heat the plate  154 . During warm running conditions, the vaporizer  300  operates in a similar fashion to that of the vaporizer  100 , using the glow plugs  108 A,  108 B for heating, during which the plate  154  may be heated to assist in heating fuel vapor that recirculates to vaporize the injected fuel spray. The vaporized fuel flows from the volume  120  to the vapor storage volume  302 . The vapor storage volume  302  provides additional fuel vapor for meeting fuel demands of the engine. The vaporizer  300  also includes a flow restrictor  306 , a vapor channel  308  and a rotary valve  310 . The flow restrictor is similar to restrictor  160  with one or more 1/16 inch holes to constrict vapor flow and maintain vapor pressure in the volume  302 . As the vapor fills the vapor storage volume  302 , the vapor passes through the restrictor  306  to fill the vapor channel  308 . Vapor is released into the air intake passage  130  when the rotary valve  310  opens. The rotary valve  310  is mechanically coupled to the rotary valve  132  such that the valves  132 ,  310  open the same amount in response to actuation of the accelerator rod  140  (described previously with respect to  FIG. 3 ).  
         [0152]     Referring to  FIG. 6 , a vaporizer  400  is similar to the vaporizer chamber  100  ( FIG. 3 ) except that the glow plugs  108 A,  108 B heat the volume  104  via a different heat-transfer path. For the vaporizer  400 , the glow plugs  108 A,  108 B are press fitted in holes in the cylindrical wall  114 . An annular volume  402 , tightly and permanently sealed, surrounds the cylindrical wall  112 . The volume  402  contains an amount of thermally conductive metal  404  that may be liquid under operating conditions. It is distributed continuously in annular form around the floor of the volume  402 . It is in thermal contact with the corresponding outer portion of wall  112 . In some examples, the metal  404  can be heated to about 300° F. In some of these examples, the thermally conductive metal  404  is sodium. Heat is transferred from the glow plugs  108 A,  108 B to the thermally conductive metal wall  114 , thence to the thermally conductive metal  404  and to the thermally conductive wall  112 . It is to be noted that the constant temperature of metal in changing from solid to liquid and vice versa introduces a heat sink effect that enables uniform temperature to be maintained around the chamber despite introduction of heat at spaced-apart point locations and despite the glow plugs cycling on and off during operation of the engine. In similar fashion a liquid heat-transfer medium may be provided in accordance with heat pipe principles. At the desired temperature for the fuel vapor-producing heat-transfer surface, within the pressure range for which this heat-transfer unit is designed, this liquid undergoes phase change to gas fuel which fills the heat-transfer volume and heats the walls which define the fuel vapor-producing heat-transfer surface.  
         [0153]     Referring to  FIG. 7 , one example of the pulse generator  210  shown in  FIG. 4  uses a timer chip  450  that is available as LM555 from Fairchild Semiconductor Corporation of South Portland, Me. In one example, the pulse generator  210  uses two variable resistors, VR 1 , VR 2  to determine frequency and width of pulses from the pulse controller  210 . Referring to  FIG. 7A , a pulse train  452  has pulse width  454  and time  456  between pulses. Changing the resistance of VR 1  modifies the pulse width  454  while changing the resistance of VR 2  modifies the time  456  between pulses. Suitable arrangements of the pulse generator  210  can allow for the pulse width  454  to have a range of 0 to 8 seconds and the time  456  between pulses to have a range of 0 to 60 seconds. The variable resistors VR 1 , VR 2  can be controlled for demonstration by hand using simple hand knobs. In production systems, the pulse generator  210  may be controlled by a computer that is responsive to power demands and running conditions of the particular engine selected.  
         [0154]     Referring to  FIG. 8 , a vaporizer  500  uses many elements similar to those of vaporizer  100  to deliver fuel vapor to a fuel injected engine  540  rather than to an engine normally utilizing a carburetor. The fuel injected engine system includes an electrical system capable of supplying electrical power at startup and during running conditions. The vaporizer  500  includes an injector  502  that sprays liquid fuel into the volume  504  at a pressure through one or a set of small holes. In one example, the liquid fuel injector  502  has a single hole orifice of about 0.001 inch in diameter. The injector  502  is electronically controllable such that an electrical “ON” signal opens the injector while an electrical “OFF” signal shuts it. The spray from the injector  502  forms a cone about an axis. The vaporization volume  504 , during warm running conditions, contains turbulently recirculating fuel vapor that is heated by heat from a cylindrical wall  518 . Similar to the process illustrated in  FIG. 1 , the vaporizer  500  vaporizes spray of liquid fuel from the injector  502  by vigorous, turbulent mixing of the liquid spray with recirculated, heated fuel vapor that previously has moved over and received added heat from the wall  518 . During warm running conditions, the temperature in the volume  504  is maintained at vaporization temperature.  
         [0155]     The cylindrical wall  518 , axi-symmetric with the fuel vapor spray from the injector  502 , is heated, through heat-transfer, by glow plugs  510 A and  510 B. The glow plugs  510 A and  510 B are powered by the electrical system of the engine system. Glow plugs operable for this application, by Bosch, are available from Mercedes-Benz USA, LLC of Montvale, N.J. as part number 001.159.2101, and see  FIGS. 20-22 . In other examples (not shown), additional glow plugs may be used to heat the cylindrical wall  518 . The glow plugs  510 A,  510 B are located in an annular space  514  that extends around the volume  504  and transfer thermal energy to the wall  518  via an annular, thermally conductive metal ring  516  that is press-fit about cylindrical member  518 . A cylindrical wall  512  surrounds the annular space  514 . The cylindrical walls  518 ,  512  rest on a bottom plate  520  and a top plate  522  encloses the structure. Sealing rings between the plates  520 ,  522  and the cylindrical members  512 ,  518  enable the pressure in the volume  504  to be maintained. The volume  504  is 2¼ inch in diameter. The parts  518 ,  512 ,  520 , and  522  are made of thermally conductive metal, preferably aluminum. In one example, the cylindrical wall  518  is ⅛ inch thick.  
         [0156]     A liquid fuel supply  506  supplies liquid fuel under pressure from an electric fuel pump via fuel line  508  to the injector  502 . The pressure P of the liquid fuel in the fuel line  508  is higher than atmospheric pressure. During warm running conditions, the pressure P in the volume  504  is also higher than atmospheric pressure but lower than in the fuel line  508 . In some examples, the liquid in the fuel line  508  is at a pressure within the range of about 60 to 100 pounds per square inch above atmospheric (psig) while pressure of the vapor in the volume  504  is between about 40 to 50 psig.  
         [0157]     During startup of the engine  540 , the vaporizer  500  is typically cold so that there is no preexisting warm fuel vapor in the volume  504 . During this startup time, a heated impact plate  526  is used to vaporize the liquid spray from the injector  502 . This follows the techniques described with respect to vaporization chamber  50  ( FIG. 2 ). In one example, the impact plate  526  is a 1/16 inch thick plate with 1/32 inch holes through the thickness of the plate  526 , the space  528  below the plate serving as additional vapor storage volume for both running and cold start operation, the holes enabling vapor to pass back and forth through the plate  526 . The plate  526  is thermally conductive metal, preferably aluminum. Glow plugs  524 A,  524 B heat the impact plate  526 . The glow plugs  524 A,  524 B are powered by the electrical system of the engine. In the arrangement shown, the glow plugs  524 A,  524 B are turned on during the cold startup period and then turned off by a controller (not shown). A thermocouple  530  measures the temperature of the impact plate  526  for thermal control of the system during running conditions. The controller uses feedback from the thermocouple  530  to control the glow plugs  524 A,  524 B to maintain a specific temperature in the volume  504 . The controller may use proportional, derivative, and integral linear control rules to maintain the temperature in the volume  504 . As previously stated, in some examples, the controller maintains the temperature in the volume  504  at the vaporization temperature.  
         [0158]     As vapor is generated in the vaporizing volume  504 , the vapor fills the channel  532  and vapor manifold  536 . It may pass through a flow restrictor not shown such as restrictor  160  of  FIG. 3 . Vapor injection valves  538 A,  538 B,  538 C, and  538 D, under computer control, time the injection of vapor fuel for respective cylinders (not shown) of the engine  540  through respective 1/16 inch holes. The engine  540  also receives air from air manifold  542 . The fuel vapor injection may occur directly into the cylinders through vapor injection valves as suggested in  FIG. 9 , or in respective air paths immediately preceding air intake valves of the respective cylinders.  
         [0159]     Referring to  FIG. 8A , a vaporizer  544  is similar to the vaporizer  500  except that it has heat-conductive features as described above with respect to  FIG. 6 . The glow plugs  510 A,  510 B are press fit in the cylindrical wall  512  and the heat from the glow plugs  510 A,  510 B is transferred via a thermally conductive metal  546  to the volume  504 . The volume  514  contains an amount of the thermally conductive metal  546  that may be liquid under operating conditions. In some examples, the metal  546  can be heated to about 300° F. In some of these examples, the thermally conductive metal  546  is sodium. Heat is transferred from the glow plugs  510 A,  5101 B to the thermally conductive metal wall  518 , thence to the thermally conductive metal  546  and thence to the thermally conductive wall  518 .  
         [0160]     Referring to  FIG. 8B , the vaporizer is similar to that of  FIG. 8 , with further features. Two spaced apart transverse plates are provided in the pressure volume. Impact plate  526 A, see  FIG. 8C , is disposed to directly encounter downwardly projected liquid spray from the injector system. It is imperforate in its center region for maximizing the area for interception and heating of liquid particles of the spray. There is a peripheral array of passages  527 A through the thickness of the plate, through which vapor may move downwardly to vapor storage in the region below, and upwardly from storage for passage to the engine. Spaced part way below plate  526 A is secondary plate  526 B. It is more highly perforate. Since it faces heated plate  526 A and the ends of the glow plugs  524 A′ and  524 B′, it is heated by radiation as well as by convection. It serves to keep hot the vapor in the storage volume below plate  526 A. When the vaporizer is oriented vertically as shown, any excess liquid that reaches the outside region of plate  526 A, can progress through passages  527 A by gravity down to plate  526 B where it may be vaporized. If any liquid passes through plate  526 B to the bottom of the vaporizer, it may be removed by a pressure-preserving drain provision not shown. In one example, plate  526 A has two diametrically opposite holes e.g. of 0.235 inch diameter to receive the glow plugs, while the peripheral holes  527 A may be of 0.076 inch diameter. Holes in the bottom plate  526 B may have a diameter of 0.085 inch.  
         [0161]     Also shown in  FIG. 8B  is a control system by which the temperature of plate  526 A, the pressure of the pressure chamber  540 A, and temperature at selected points on the annular heat-conductive ring  516  are monitored. Additional thermocouples not shown such as thermocouples  158  and  530  may be employed. Based upon the monitored values a computer  562  controls energization of the two sets of glow plugs  510  and  524  by the battery of the engine system. The computer may be a computer dedicated to the vaporization-based fuel system, or the general engine management computer.  
         [0162]     Referring to  FIG. 9 , a vaporizing system  550  includes the vaporizer  500  of  FIG. 8  and additional components. The liquid fuel supply  506  includes fuel tank  552 , electric fuel pump  554 , fuel filter  556 , and fuel pressure regulator  558 . Liquid fuel from the fuel tank  552  is pumped by the fuel pump  554  through the fuel filter  556 , and through pressure regulator  558  to arrive at the liquid spray injector  502  under pressure. The vaporization system  550  also includes a pulse generator  560  capable of generating pulses to turn the liquid injector  502  off and on. A computer  562  controls the frequency and width of pulses generated by the pulse generator  560 . The frequency and width of the pulses relate to the desired power demands on the engine  540 . The computer  562  also receives feedback from the thermocouple  530  to control activation of glow plugs  510 A,  51 OB according to appropriately established control rules to maintain a desired temperature in the volume  504 . The engine  540  includes air intake manifold  542  that supplies air to cylinders  564 A,  564 B,  564 C,  564 D, and an appropriate injection system for the fuel vapor for the respective cylinders as described with respect to  FIG. 8 . In other examples, the engine  540  of course may have a different number of cylinders, and other configurations.  
         [0163]     Referring to  FIG. 9A , an engine system has the features of  FIG. 9 , combined with further features. A cold start liquid fuel injector system is associated with the air intake and manifold system  542  of the engine, fed by fuel line  562  from fuel pump  554 . The cold start injector is constructed and arranged to inject a spray of liquid fuel into the combustion air to facilitate start-up and running in cold conditions. It may be implemented to function only while the vapor-producing system comes up to pressure, or it may be implemented to also assist the fuel vapor system under specified power demand situations. In the system illustrated, cold start liquid fuel injector  560  is arranged to inject atomized liquid fuel spray into the central airflow, the resulting air-fuel mixture to be divided by the air manifold to serve all cylinders. In other embodiments separate liquid fuel injectors may be employed for subsets of cylinders or for respective individual cylinders.  
         [0164]     The engine management computer has inputs from critical monitoring locations to provide data from which it can select optimum operating conditions from moment to moment for the combined system of the fuel vaporizer and the cold start liquid fuel injector. Besides inputs that are typical of available computer controlled engines, the inputs include temperature and pressure of the vaporization chamber  504 , of the main vapor supply line and of the vapor distribution rail, and temperature of the impact plate  526  and the heat distribution system in the outer heating chamber of the vaporizer. For instance, pressure inputs are conveyed from monitors  564  and  565  at, respectively, the vaporizer and the fuel vapor rail, and temperature inputs are applied from temperature data line  567  monitoring temperature of impact plate  526 , data lines  566  and  568  monitoring temperature of the heat distribution ring  516  of the vaporizer and from temperature monitor  570  at the fuel vapor rail.  
         [0165]     In  FIGS. 9B  and C, a system similar to that just described is diagrammatically illustrated with respect to a V-8 engine. Two fuel rails  536 A and  536 B supply respective sets of four fuel spray vapor injectors, while the cold start injector  560  is centrally arranged to inject liquid fuel spray into air following the air intake  542 . Also illustrated in this figure is pressure control valve  22 A, for controlling the pressure in the vapor supply line, and idle air control valve which is controlled by the engine management computer.  
         [0166]     The function of a fuel vapor injector  531  is to accurately meter fuel vapor to its respective cylinder on command by an electronic signal pulse controlled by the computer. The pulse is timed with respect to the power stroke of the engine, and is of duration suitable to pass the desired volume of vapor. When de-energized, the valve is closed, preventing unwanted flow of vapor or backflow. Presently it is preferred to employ a pintle valve for this purpose. As is known, a pintle is a finely machined tapered part, typically of stainless steel, that normally sits upon a matching tapered valve seat, the pintle passing fluid only when lifted from its seat. The size of the seat and pintle, as well as the downstream nozzle or outlet, determine the size and pattern of the injected flow.  
         [0167]      FIG. 9D  diagrammatically illustrates a solenoid-operated, pintle-based fuel vapor injector,  538 ′. Pintle valve assembly  702  is constructed, on each actuation, to pass a fuel vapor charge for a power stroke of the cylinder with which it is associated. Its basic construction is similar to that of a liquid fuel injector, except that its passages are characteristically substantially larger to enable the larger volumetric flow required for a vapor charge of the same weight. An operating rod  704  extends from the pintle member to a translatable armature  706  of material selected to magnetically interact with solenoid coil  708 . When the coil is energized under computer control, the armature is raised by magnetic force to the position shown, overcoming the resistance of return spring  710 . When solenoid coil  708  is de-energized, its magnetic field collapses, and the spring returns the pintle member to its firmly closed position against its seat. A vapor passage extends along the entire length of the moving structure, to enable fuel vapor to move freely from vapor fuel rail  536  through the injector assembly to the pintle-valved port at the bottom of the vapor injector. In the particular arrangement of this figure, the flow passage is through the hollow center of return coil spring  710 , into a central passage  706  of the armature, thence out side outlets  709  of the armature, to flow along the outside of operating rod, then outside past a guide to the open central valve passage  711 . In one example the outlet passage of the vapor injector pintle valve is 0.032 inch (in comparison to 0.004 to 0.008 inch for a liquid injector, for instance). In some instances, multiple vapor outlet orifices are provided at the discharge side of the pintle member of the vapor injector to disperse the vapor flow. The materials and design of the vapor fuel injectors are selected to withstand the vapor temperature of the hot vapor and provide long life.  
         [0168]     In  FIG. 9E , a cold start liquid spray injector is diagrammatically illustrated. It has a solenoid and pintle valve arrangement similar to that of the vapor injector, however its liquid outlet passage is of 0.004 inch diameter, and the other passages through the device are correspondingly small.  
         [0169]     In  FIG. 9F  fuel rail  536  is shown, sized to provide fuel vapor to a set of fuel vapor injectors,  538 ′.  
         [0170]      FIGS. 9G-1  through  9 G- 4  diagrammatically illustrate an engine cylinder of a fuel vapor injector-fed, four stroke gasoline engine. At the critical admission stroke, fuel vapor is injected to the discrete air inlet port for that cylinder, timed with the opening of the air inlet valve. Following that stroke, in which the fuel and combustion air enter the cylinder, conventional compression, power and exhaust strokes occur. There are significant differences in performance over a conventional engine. At the end of the compression stroke, virtually all of the fuel is in vapor form, in contrast to the significant quantity of liquid droplets that still exist at this stage in a conventional gasoline engine. In the power stroke, the spark is timed to optimize the crank angle for the more immediate and thorough combustion that can take place, thus enabling more useful power to be derived from a given weight of fuel than is obtained in conventional gasoline engines. Furthermore, retention of liquid fuel in crevices of the engine during the power stroke is avoided. At the exhaust stroke, the emissions are substantially free of unburned hydrocarbons and particulates while other emissions can be at acceptable or improved levels.  
         [0171]     The principles described are useful with various internal combustion engine designs. A further example is that of a two stroke gasoline engine. While two stroke engines are advantageous in providing more power per engine weight that four stroke engines, they suffer from worse combustion properties. It is realized that principles of the invention can be employed to improve combustion in two stroke gasoline engines. Fuel vapor may be introduced to a two stroke engine centrally to combustion air, or by vapor injection at the air inlet port of each individual cylinder generally in the manner described above. In other cases, direct gasoline vapor injection into each cylinder may be employed, for instance after the exhaust port of a cylinder of a two stroke engine has been closed but before the compression stroke is completed. Another category of engines with which the fuel vaporizing principles are useful is the rotary engine (such as a Wankel engine) in which the moving part of the combustion region is rotary rather than reciprocating.  
         [0172]     Principles described are also useful with diesel engines. Referring to  FIG. 10 , a vaporizer  600  delivers diesel fuel vapor to a diesel engine  640 . The diesel engine  640  is associated with an electrical system capable of supplying electrical power. The vaporizer  600  includes an injector  602  that sprays liquid diesel fuel into the volume  604  at a pressure through one or a set of small holes. In one example, the liquid fuel injector  602  has a single hole orifice of about 0.001 inch in diameter. The injector  602  is electronically controllable such that an electrical “ON” signal opens the injector while an electrical “OFF” signal shuts the injector. The spray from the injector  602  forms a cone of spray about an axis. The vaporization volume  604 , during warm running conditions, contains recirculating fuel vapor that is heated by heat from surrounding cylindrical wall  618 . Similar to the process illustrated in  FIG. 1 , the vaporizer  600  vaporizes the spray of liquid diesel fuel from the injector  602  by vigorous mixing of the spray with recirculated, heated fuel vapor that previously has moved over and received added heat from the wall  618 . During warm running conditions, the temperature in the volume  604  is maintained at the vaporization temperature.  
         [0173]     A limited amount of pressurized air is introduced into the volume  616 , and thus into volume  604 , via a pressure valve  628 , from an air pump, which may for instance be a small positive displacement air pump. This air disseminates and adds to the circulation and mixing action upon the diesel spray in volume  604 , and may also serve a carrier gas function in transfer of pressurized flow to the engine.  
         [0174]     As with previously described examples, the cylindrical wall  618  is heated, through heat-transfer, by glow plugs  606 A and  606 B. The glow plugs  606 A,  606 B are powered by the electrical system of the diesel engine. Operable glow plugs for this application, by Bosch, are available from Mercedes-Benz USA, LLC of Montvale, N.J. as part number 001.159.2101, and see  FIGS. 20-22  below. In other examples (not shown), additional glow plugs may be used to heat the cylindrical wall  612 . The glow plugs  606 A,  606 B are located in an annular space  608  that extends around the volume  604 . Glow plugs  606 A,  606 B transfer thermal energy to the wall  618  via an annular, thermally conductive metal ring  610  that is press-fit about the cylindrical member  612 . A cylindrical wall  618  surrounds the annular space  608 . The cylindrical walls  612 ,  618  rest on a bottom plate  614  and a top plate  617  encloses the structure. Sealing rings between the plates  614 ,  617  and the cylindrical walls  612 ,  618  enable the pressure in the volume  604  to be maintained. The parts  612 ,  614 ,  617 , and  618  are made of thermally conductive metal, e.g. aluminum or a suitable high temperature alloy. In one example, the cylindrical wall  612  is ⅛ inch thick while the volume  604  is 2¼ inch in diameter.  
         [0175]     A liquid diesel fuel supply  606  provides liquid fuel under pressure via fuel line  608  to the injector  602 . The pressure of the liquid diesel fuel in the fuel line  608  is higher than atmospheric pressure while the pressure in the volume  604  is also higher than atmospheric pressure during warm running conditions but lower than the pressure in the fuel line  608 . In some examples, the diesel liquid in the fuel line  608  is at a pressure between about 60 to 100 pounds per square inch above atmospheric (psig) while pressure of the diesel vapor in the volume  604  is between about 40 to 50 psig, with a differential between the two pressures as previously described.  
         [0176]     During startup of the engine  640 , the vaporizer  600  is typically cold so that there is no preexisting warm diesel fuel vapor in the volume  604 . During this startup time, a heated impact plate  620  is used to vaporize the diesel liquid spray from the injector  602 . This follows the techniques described with respect to vaporization chamber  50  ( FIG. 2 ). In one example, the impact plate  620  is a 1/16 inch thick plate with 1/32 inch holes through the thickness of the plate  620  with a storage volume  616  below the impact plate  620 . The holes enable diesel vapor and the air to pass back and forth through the plate  620 . The plate  620  is thermally conductive metal, e.g. aluminum or a suitable high temperature alloy. Glow plugs  622 A,  622 B heat the impact plate  620 . The glow plugs  622 A,  622 B are powered by the electrical system of the diesel engine. The glow plugs  622 A,  622 B are turned on during the cold startup period and then turned off. A thermocouple  624  measures the temperature of the impact plate  620 . A controller (not shown) uses feedback from the thermocouple  621  to control the glow plugs  606 A,  606 B to maintain a specific temperature in the volume  604 . The controller may use proportional, derivative, and integral linear control rules to maintain the temperature in the volume  604 .  
         [0177]     As diesel vapor is generated in the vaporizing volume  604 , the diesel vapor fuel fills and moves through the vapor channel  632  into vapor manifold  636 . Vapor fuel valves  638 A,  638 B,  638 C, and  638 D regulate the flow of diesel vapor fuel into cylinders (not shown) of the engine  640 . The engine  640  also receives air from air manifold  642 . Such a system may be used for only a partial fuel charge for a cylinder, relying upon other techniques to complete the charge. Such techniques are described below.  
         [0178]     Referring to  FIG. 10A , a vaporizer  650  is similar to the vaporizer  600  except that it has heat-conductive features as described above with respect to  FIG. 6 . The glow plugs  606 A,  606 B are press fit in the cylindrical wall  618  and the heat from the glow plugs  606 A,  606 B is transferred via a thermally conductive metal  652  to the volume  604 . The volume  608  contains an amount of the thermally conductive metal  652  that may be liquid under operating conditions. In some examples, the metal  652  can be heated to about 300° F. In some of these examples, the thermally conductive metal  652  is sodium. Heat is transferred from the glow plugs  606 A,  606 B to the thermally conductive metal wall  618 , thence to the thermally conductive metal  652  and to the thermally conductive wall  612 .  
         [0179]     Principles described are also applicable to decentralized vaporization of fuel for an engine. An important case is a vaporizer dedicated to a single cylinder of a piston engine. A vapor injector may be associated directly with such a vaporizer. In the embodiment of  FIGS. 11 and 11 A, vaporization is produced by combined impingement-contact heating and free-space mixing based on heat produced by a central heater. In the example of these figures, glow plug  702  is located centrally in the bottom of a cup-shaped thermally conductive member  700 . As shown, the glow plug has its upwardly-directed hot end exposed for contact by liquid spray. Cup member  700  is comprised of a transversely extending heat-conductive bottom wall  704 , which is in heat-receiving relationship with the central glow plug, and upstanding outer heat-conductive sidewall  706 , which is in thermal continuity with the bottom wall to also receive heat from glow plug  702 . The top of the cup is closed by top member  701  to complete a pressure chamber that is constructed to operate at substantial super-atmospheric pressure P 1 . The inner surfaces of the cup define a heat-transfer surface for fluids. Located in the top member is a liquid spray injector  710 . It is directed downwardly, toward the glow plug, and is constructed and arranged so that a significant portion of its spray contacts the glow plug and regions of the heat-transfer surface close to it. As in the previous embodiments there is a vapor exit channel  714 . It, and an associated outlet control system  716 , are denoted diagrammatically. These are effective to maintain super-atmospheric pressure in the vaporization chamber. As illustrated, the exposed surface of bottom wall member  704  is shaped as a section of a torroid, to guide the entering flow into a torroidal mixing motion. In radial cross-section, the bottom surface of the cup progresses from the exposed surface of the cylindrical glow plug in a curved manner, outwardly, downwardly, curving through horizontal, then outwardly, upwardly to blend into outer wall  706  of the cup. This surface cooperates with the downward, axi-symmetric spray to guide the liquid spray, as it heats, and vapor, as it is produced, into a circulating flow useful to provide heat exchange by mixing. At the top of its circulation, the flow turns inwardly to encounter and mix with the atomized particles of freshly arriving liquid spray. This aids in vaporization of the sprayed liquid particles. The higher the pressure within the chamber, the greater is the density of produced vapor, the greater is the heat-transfer by mixing, and hence the smaller may be the dimensions of the vaporizer. It is realized that this arrangement can be sufficiently compact to be practical at an individual engine cylinder or adjacent a small number of cylinders. In production versions, the glow plug and the bottom of the cup-shaped chamber, or indeed the whole chamber, can be manufactured as a unit, without joints in the internal surface. For instance a casting of heat-conductive, heat resistant metal may have a continuous bottom surface and a central depression in its underside into which a resistive heater element, such as that used in glow plug, is sealed, the central part of the cup member effectively becoming a glow plug. In certain embodiments, the unit may be constructed as a high pressure vessel, to enable elevation of the pressure of operation to pressure in the hundreds of psi, or higher, with care being taken to select materials for the walls of the chamber that can withstand the corresponding high temperature of vaporization. In some cases the material of at least a part of the chamber may be a ceramic. A portion of a ceramic member, itself, can form an electrically resistive heating element of the vaporizer, generally in the manner presently used in some makes of glow plugs.  
         [0180]     Dedicated vaporizer designs can be combined with pintle valves for both admitting liquid spray for vaporization and for controlling flow of the produced, pressurized fuel vapor.  
         [0181]     In the embodiment of  FIGS. 12 and 12 A, a liquid supply pintle valve  720  operated by a suitable control  724 , and seated on a valve seat in a wall of the chamber, moves in translating motion to alternately open the passage to admit liquid spray to the chamber and to seal the chamber. A set of side vapor outlets  714 A are provided in the wall  706 A of the chamber for directing fuel vapor to one or more cylinders of an engine.  
         [0182]     In the embodiment of  FIGS. 13 and 13 A, a surrounding cylindrical wall  730  and bottom wall  731 , guide flow through from the outlets  714 A downwardly and then radially inwardly to merge into a single flow that is controlled by a vapor flow control valve, here shown as vapor pintle valve  736 .  
         [0183]     In the vaporizer A of  FIG. 14 a  solenoid assembly  726  is provided to activate pintle valve  720  to produce a liquid spray from the valve outlet nozzle. An iron armature  732  is arranged in driving relationship with the pintle member. The parts of this solenoid assembly are constructed to provide a continuous liquid flow path from the pressurized liquid fuel line to the pintle valve  720  and spray nozzle  739 , following principles previously described.  
         [0184]     When activated by electric current flowing in surrounding solenoid coil  728 , the magnetic field produced by the coil overcomes the resistance of return spring  734 , pulling the pintle member upwardly from its valve seat. This produces fuel flow from the pressurized liquid supply line through the pintle valve and injection of liquid spray into the vaporization chamber through nozzle  739 . Upon deactivation of the coil, the return spring  734  returns the pintle member to closed position on its valve seat.  
         [0185]     Also, at the vapor outlet, the vaporizer of  FIG. 14  includes a spring-loaded vapor control pintle valve  736 A, which includes return spring  738 . It enables vapor flow when the pressure of fuel vapor in the chamber exceeds the resistance of the spring, and closes the valve when the pressure of the vapor drops below that level.  
         [0186]     In the embodiment of  FIG. 15 , the vaporizer is sized and arranged to supply fuel to a single cylinder of an engine. In the case shown, the timing system of the engine activates the solenoid coil  728  in advance of each power stroke of the cylinder, to provide a fuel vapor charge. The timing, flow rate and duration of the liquid spray pulse, and the degree of heating are selected and managed under computer control in accordance with the type and demand of the engine. The attained pressure of heated vapor in the vapor chamber may be employed to provide the motive force for the vapor to flow to the point of fuel injection.  
         [0187]     The vaporizer B of  FIG. 16  is constructed to itself also serve as a computer controlled vapor injector. In vaporizer B, as was the case with vaporizer A, a solenoid assembly  726  is provided to activate the liquid spray pintle valve  720  to enable liquid flow and production of liquid spray into a vaporization chamber. An iron armature  732  is arranged in driving relationship with the pintle member. When activated by current flowing in surrounding solenoid coil  728 , the magnetic force of the coil upon the armature overcomes the resistance of return spring  734 , pulling the pintle member  720  upwardly from its valve seat. This produces liquid fuel flow F from the pressurized supply line through the liquid spray injector, to produce a spray of atomized liquid particles. Upon deactivation of the coil, return spring  734  returns the pintle member to closed position on the valve seat. Further, in the vaporizer B of  FIG. 16 , the outlet pintle valve  736 B is also provided with a solenoid assembly  726 A to activate the vapor release pintle valve to enable vapor flow to the engine. In this case return spring  734 A is sized to provide a closing force exceeding the force of the contained pressurized vapor. An iron armature  732 A is arranged in driving relationship with the pintle member. When activated by current flowing in surrounding solenoid coil  728 A, it overcomes the resistance of return spring  734 A, pulling the pintle member downwardly from its valve seat. This produces fuel vapor flow from the pressurized vaporization chamber. Upon deactivation of coil  728 A, the pintle member is returned to closed position on the valve seat by the spring  734 A. The parts of this injector assembly are constructed to provide a continuous vapor flow path from the pintle valve to the vapor delivery point of the unit by suitable passages past or through the operative members of the pintle actuation assembly, according to principles described earlier.  
         [0188]     Vaporizer B of  FIG. 16  is sized and arranged to supply fuel to a single cylinder of an engine. When used in the general arrangement shown in  FIG. 15 , the timing system of the engine activates both solenoid coils in synchronization with the engine. The liquid solenoid is activated to provide a liquid fuel spray charge to the cylinder. The timing, flow rate and duration of the liquid spray pulse and the heating interval between liquid fuel injection and activation of the vapor solenoid to discharge vapor to the engine are selected and managed under computer control in accordance with the type and demand of the engine. The attained pressure of heated vapor in the vapor chamber may be employed to provide the motive force for the vapor to flow to the point of fuel injection. The chamber may be constructed for high temperature operation. In one case it is formed of Inconel 617 or other high temperature stainless steel.  
         [0189]     The embodiment of  FIG. 17  differs from that of  FIG. 15  in that the fuel vapor injector B is constructed and arranged to discharge directly into the combustion region of an engine cylinder at the appropriate time. For instance, it may discharge into the cylinder of the specialized two stroke gasoline engine mentioned above. If designed for suitable high pressure, it may inject diesel vapor directly into the combustion space of a diesel engine, i.e. into the diesel cylinder or into a combustion pre-chamber of the cylinder, depending upon the design of the diesel engine. The heating interval between completion of injection of liquid fuel spray into the vaporization chamber and discharge of vapor to the engine can provide important pressure build-up to enable vapor flow. In addition a vapor purging piston timed with the engine, for instance driven by a linear motor, might be arranged to purge the vaporization chamber, to force the vapor through the vapor injection valve, into the compressed air in the combustion region.  
         [0190]     In one example, the liquid spray is initiated into the vaporization chamber early during the air-admission stroke of the engine, or even earlier. In a diesel engine, vapor injection would be timed to occur soon after the beginning of the diesel power stroke.  
         [0191]     In  FIG. 18 a  fuel distribution system is diagrammatically illustrated for use with the fuel vapor injectors of the type of  FIG. 16 . A high pressure liquid diesel fuel rail is supplied by a suitable pump. This rail supplies a set of vaporizer/vapor injectors of the type B of  FIG. 16 , one for each cylinder. The engine management computer times the actuation of the liquid diesel furnish solenoid valve and subsequently, of the vapor injector solenoid valve, to produce a vapor charge for each power stroke.  
         [0192]     Other arrangements may be made for practical application in a diesel environment, using one or more of the diesel arrangements that have been described. For instance, a diesel vapor injector of the type described may be arranged to inject only a partial fuel charge to the diesel cylinder, with the remaining fuel requirement of each power stroke provided by a liquid diesel fuel injector. In such a case the diesel fuel vapor injection may be timed with the air admission stroke, and may inject directly into the combustion region of the diesel cylinder or into its air inlet port. If done in this manner, it is important that the fuel vapor partial charge be limited in size to not reach the critical value that would create a danger of pre-ignition during the compression stroke. An advantage this system may provide is that of better combustion efficiency as only part of the fuel is supplied by the conventional system that produces particulate emissions and the like.  FIG. 19  illustrates the stages of a typical diesel engine.  
         [0193]     It is advantageous that the glow plug selected have a long life rating under the conditions of use. Referring to  FIGS. 20-22 , a long life resistive coil element  802  within a glow plug is advantageously made of platinum alloy wire. The wire may be of 0.012 inch diameter, straight length of 4 inch, wound into a helical coil of length l 1  of about ½ inch. The outer metal tube  812  into which the coil is inserted may be of Inconel 617, of length l 1 , of about ½ inch. It may have an inner diameter of about 0.170 inch and wall thickness of 0.035 inch. As shown it has a lower end closed about the lower extension of the coiled wire. This lower end of the wire is welded to the tube. For fast heating of the tube it is advantageous to employ fine glass powder  804  as the predominant electrical insulation between the sides of the coil and tube. Fine, high temperature glass powder is seen to have favorable thermal conductive properties for conducting heat quickly from the coil to the tube, while providing appropriate electrical insulation. The filling may be 100% of the fine glass powder or 90% of the fine glass powder and 10% ceramic powder, for instance. The upper end of the coil is inserted in a receiving aperture and welded to the lower end of central stem  806 , which may be of stainless steel. The upper end of the stem  806 A serves as an electrical terminal to receive power from the battery. A body  811  e.g. of machined steel is joined to the top of tube  812 . A seal member  807  of temperature-resistant fiber extends between stem  806  and the outer body at  810 . A long life electrically insulative, pressure seal  808  of high temperature pressure seal glass is formed above member  807 , between the electrically conductive connector stem  806  and the outer body. The overall length l 2  of the glow plug unit may be about 4 inch.  
         [0194]     A number of systems have been described for illustration. It will be understood that various modifications may be made without departing from the spirit and scope of the inventive contributions. For example, the heat-transfer surfaces may be of other configuration, heating of these surfaces can also be performed by other means of heating, such as other electrical heating techniques, and exterior surfaces of the vaporizer and associated conduits may be provided with thermal insulation and/or auxiliary heating. Accordingly, systems of other designs are within the scope of the following claims.