Abstract:
A simple propulsion engine utilizing unheated atmospheric air as the propellant, and driven by a single cycle (unicycle) engine with internal combustion cylinder and free piston is disclosed. A free piston with an annularly arranged thrust piston to divide a dual-diameter cylinder into two combustion chambers and two thrust chambers is provided. Scavenge feeder lines connected the thrust chambers to the combustion chambers via check valves provide exhaust scavenging, additional thrust output through exhaust nozzles, and feeding of fresh air into the combustion chambers. Also, pressure-actuated fuel injectors utilize pressure changes in respective combustion chambers to inject fuel at the appropriate time. The fuel injector includes an intensifier piston and pintle to raise the fuel pressure.

Description:
[0001]    This Application is a divisional of co-pending Application No. 09/500,468, filed on Feb. 9, 2000, the entire contents of which are hereby incorporated by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention is in the field of propulsive machines cooperating with internal combustion, free piston engines and compressors to produce motive power, lifting, or other uses. This invention also relates to a self-actuated fuel injector that may be utilized in such an engine.  
           [0004]    2. Background of the Invention  
           [0005]    Numerous inventions known in the prior art have been developed, and many proposed which are based on the Newtonian principle of reactive propulsion. Propellers and helicopter rotors, jet engines, and rockets are the principal examples of that genre.  
           [0006]    Propellers and rotors, however, require complex internal combustion or gas turbine engines to supply rotating torque to airfoil shaped blades. Large amounts of unconstrained, low pressure air is propelled aftward of the propeller/rotor due to the lift and screw action of the airfoil shaped blades, creating thrust and invoking the concomitant slip, drag, and kinetic energy air stream losses. The total fuel efficiency of these systems is determined primarily by the engine and propeller inefficiencies. In the present invention, there are no propeller losses, and engine losses and engine weight are minimized by the elimination of piston rods, crankshafts, flywheels, transmissions, and, in the case of turbines, high soak temperature turbine blading, adjunct compressors, and internal flow losses.  
           [0007]    Chemical thermal-jet engines utilize ram air and axial flow or centrifugal compressors to force air into an engine inlet and raise its pressure in a combustion chamber. In the combustion chamber, fuel is injected and burned creating high temperature, high velocity gases. Part of the gas velocity energy is used up driving turbine blades for the compressor, and the gas then exits a nozzle to produce thrust. Large thermal losses are incurred due to the extreme temperatures at which the jet engine must operate. Rocket engines carry fuel and oxidizer internally and generate their propulsive gasses from within.  
           [0008]    Free piston internal combustion engine and compressor combinations are well known, and the prior art contains many examples of various concepts and configurations. None were found which incorporates a power stroke at each end of a single cylinder and uses an unadorned, simple piston whose only functions are to separate the combustion and compression chambers and provide inertial energy storage. Free piston engines and compressors disclosed in the literature are complex and heavy devices which go to great lengths to counteract cylinder reaction to the acceleration of the piston(s) by the use of elaborate spring-counterweight mechanisms or tandem pistons synchronized by rack and pinions, linkages, gears, or other mechanical means.  
           [0009]    However, there are no feasible, chambered high pressure propulsion systems that utilize unheated atmospheric air, on a continuous basis, as the main propellant medium. The reason for this is undoubtedly the difficulty of conceiving an engine and compressor combination that is simple and lightweight enough to make it practical.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention involves a major change in the concept of vertical lifting and locomotion in each of the primary modes of land, air, and marine propulsion. As a necessary prerequisite to invention of the atmospheric propulsion engine, the unicycle free piston engine was invented as described herein. The combination of atmospheric air propellant and unicycle free piston engine are part of the unique and defining elements of the present invention.  
           [0011]    The single cycle free piston engine disclosed herein uses a simple lightweight piston which minimizes the reactive movement of the cylinder assembly (this movement being a function of the ratio of piston mass-to-cylinder assembly mass).  
           [0012]    This present invention is an atmospheric propulsion engine, firing its free piston at each end of the cylinder, scavenging of exhaust products, and natural self cooling due to the large internal ingestion of atmospheric air.  
           [0013]    As an indication of the efficacy of the atmospheric propulsion engine, a simple calculation is presented. A cylinder 1.5 inches in diameter, and 18 inches long contains a volume of 31.8 in 2  and has a weight of air equal to 0.0014 lbs. at standard atmospheric conditions. When this mass of air is expelled at 70° F. (520° R), at sonic velocity, in 0.010 seconds through a thrust-producing nozzle, a force of 4.83 lbs. is generated. If this same mass of air is expelled at the temperature and pressure corresponding to a 10 to 1 compression ratio (1300° R and 370 psi), the force generated would be 7.71 lbs.  
           [0014]    The atmospheric propulsion engine will produce a thrust (force) somewhere between the above numbers, and a computer simulation of the above configuration indicates that an average thrust of 6.4 lbs. can be achieved. Using aircraft type construction, it is estimated that such a device would weigh about 2.1 lbs., yielding an engine thrust-to-weight ratio of 3-to-1. Based on this evaluation, the atmospheric propulsion engine would be suitable for flying and hovering applications, as well as numerous other uses discussed in the following descriptions.  
           [0015]    Note: The above performance calculations are based on the following formulas: 
           Thrust=Mass of air×Sonic velocity/time 
           Sonic velocity={square root}{square root over (k×g×R×T)} 
           [0016]    Where:  
           [0017]    k=Ratio of specific heat for air=1.4  
           [0018]    g=Gravity constant=386.4 in./sec 2    
           [0019]    R=Gas Constant=640 in-lb/lb-°F.  
           [0020]    T=Temperature °R  
           [0021]    The specific impulse of the above configuration is calculated to be in the 2000 to 4000 lb-sec/lb range using standard automotive gasoline or diesel fuel.  
           [0022]    A comparison of existing art with the present invention of the atmospheric propulsion engine reveals the superior characteristics of the concept and method.  
           [0023]    This invention directly converts the fuel&#39;s thermal energy primarily into mechanical Pressure/Volume (PV) forces, compressing atmospheric air and expelling it at sonic velocity to efficiently generate thrust. The only major moving part in the atmospheric propulsion engine system is the internally shared engine/compressor piston which presents another major advantage of this invention, especially in the case of helicopters, by the elimination of noisy and dangerous external rotating propellers and rotor blades.  
           [0024]    In the present invention, most of the fuel&#39;s thermal energy is used up in the PV expansion process of the working fluid to drive the piston, thus, after the compressed air propellant is expanded in the thrust nozzles, a relatively cool, benign gas is expelled. No compressor is required as atmospheric pressure is adequate to refill the expulsion gas chamber. However, superchargers, or in applications involving moving vehicles, ram air, can be utilized to raise the compressor inlet pressure, thus enhancing compressor volumetric efficiency and increasing the engine&#39;s thrust-to-weight ratio.  
           [0025]    Applications for an independent, free standing thrust engine are manifest.  
           [0026]    Given a nominal engine thrust to weight ratio of 3 to 1, coupled with the benignity of the exhaust products, it becomes feasible to design and market a personal passenger vehicle which can fly to its destination without having to concern itself with roads, bridges, or other ground based obstacles. This thrust to weight ratio also may make the engine applicable to “backpack” individual flying machines. Steering, stability and control of such flying machines can be accomplished through thrust vector control mechanisms such as movable nozzles or jet vanes as shown in FIGS. 10 and 11, or may be implemented by other well known aerodynamic means available in the existing art.  
           [0027]    Much effort has been expended in the quest for reducing weight and increasing the efficiency of automobiles to combat air pollution. An automobile designed using the lightweight atmospheric propulsion engine disclosed herein would preclude the necessity for flywheels, crankshafts, piston rods, cooling systems, transmissions, driveshafts, differentials, and drive axles. This would eliminate the weight, power losses, and thermal inefficiencies due to these components. Probably, 50% or more of an automobile&#39;s weight could be eliminated and fuel requirements reduced considerably. In addition, the propulsion drive would make vehicle acceleration independent of tire traction. A passenger car could be designed with forward and rearward facing thruster nozzles to control acceleration and braking (thrust reversal, as shown in FIG. 6), and vectored nozzles could control steering to effect a vehicle which is independent of road and tire friction. Or, a hybrid of conventional braking and steering with propulsive drive could be contrived. These same characteristics apply to travel over water, snow, and ice.  
           [0028]    Present ground effect machines (GEM) require substantial amounts of air to create sufficient pressure in the vehicle-to-surface interface plenum with which to support the gravity load and provide sufficient surface clearance. This is normally accomplished by the use of large, noisy, inefficient fans. The present invention could be used to provide partial lift from its propulsion engine(s), while using the nozzle exhaust to pressurize the, GEM interface plenum. The small plenum back pressure would have little effect on the nozzle&#39;s thrust efficiency.  
           [0029]    Aircraft propulsion would benefit from this invention&#39;s enhanced engine specific impulse and from the availability of high speed ram air to increase the propulsion chamber&#39;s volumetric efficiency, thus minimizing the size and weight of the overall propulsion system. The availability of simple, full engine thrust reversal would greatly increase aircraft braking capabilities and reduce runway rollout.  
           [0030]    The atmospheric propulsion engine can be slidably mounted to its structure with a simple centering spring mechanism and allowed to traverse a small distance back and forth as shown in FIG. 8. This engine can also be configured in tandem opposed end-to-end combinations to eliminate reactive engine movement, with synchronization being accomplished by a correct starting procedure, metering of fuel, and timing of the ignition process. FIG. 7 shows schematically how two tandem engines could be configured.  
           [0031]    In addition to its use in the atmospheric propulsion engine, the simplicity and lightweight of the single cycle free piston engine disclosed herein is desirable for other engine applications such as air compressors and power tools.  
           [0032]    Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.  
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0033]    The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:  
         [0034]    [0034]FIG. 1 is a schematic cross section of the atmospheric propulsion engine of a first embodiment made up of the unicycle free piston engine and propulsion components;  
         [0035]    [0035]FIG. 2 is the schematic of FIG. 1 with the piston in firing position at the left end of the cylinder;  
         [0036]    [0036]FIG. 3 is the schematic of FIG. 1 with the piston crossing the inlet/exhaust ports at the left-of-center cylinder region;  
         [0037]    [0037]FIG. 4 is the schematic of FIG. 1 with the piston crossing the nozzle port on the right end of the cylinder;  
         [0038]    [0038]FIG. 5 is the schematic of FIG. 1 with the piston in firing position at the right end of the cylinder;  
         [0039]    [0039]FIG. 6 is the schematic of FIG. 1 showing an engine configuration with discrete thrust reversal nozzles and valving;  
         [0040]    [0040]FIG. 7 is a configuration of engines in tandem to eliminate reactive cylinder movements;  
         [0041]    [0041]FIG. 8 shows a spring centered, slidably mounted engine to allow reactive movements;  
         [0042]    [0042]FIG. 9 is a schematic of an integrated atmospheric propulsion system with fuel, compressed air, and electrical components;  
         [0043]    [0043]FIG. 10 shows a conventional swivel nozzle concept that may be utilized in conjunction with the inventive engine;  
         [0044]    [0044]FIG. 11 shows a conventional jet vane concept that may be utilized in conjunction with the inventive engine;  
         [0045]    [0045]FIG. 12 is a schematic cross section of a second embodiment of the inventive engine;  
         [0046]    [0046]FIG. 13 is the schematic of FIG. 12, with the piston in firing position at the left end of the cylinder;  
         [0047]    [0047]FIG. 14 is the schematic of FIG. 12 with the combustion in the left combustion cylinder in progress;  
         [0048]    [0048]FIG. 15 is the schematic of FIG. 12 with the piston at the midpoint of its stroke and at maximum velocity;  
         [0049]    [0049]FIG. 16 is the schematic of FIG. 12 compressing the right combustion chamber;  
         [0050]    [0050]FIG. 17 is the schematic of FIG. 12 in firing position at the right end of the cylinder;  
         [0051]    [0051]FIG. 18 is a schematic of an inventive self-actuated fuel injector that may be utilized with the second embodiment of the inventive engine;  
         [0052]    [0052]FIG. 19 is a schematic of the inventive self-actuated fuel injector of FIG. 18 during an injection phase of operation; and  
         [0053]    [0053]FIG. 20 is a schematic of the inventive self-actuated fuel injector of FIG. 18 during a reset phase of operation. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0054]    The first embodiment of the atmospheric propulsion engine is illustrated schematically in FIG. 1, and generally by reference numeral  1 . It is a single-cycle (unicycle), spark ignition engine and compressor having a cylinder  02  with cylinder heads  012   a  and  012   b  on each end and having a piston  03  slidably interposed therebetween, forming alternate combustion and compression chambers  010   a  and  010   b . Cylinder heads  012   a , 012   b  contain fuel injectors  08   a , 08   b  and igniters  09   a , 09   b . The engine has thrust nozzles  04   a , 04   b  with associated valves  06   a ,  06   b  and actuators  014   a , 014   b  which sense piston  03  obturation of nozzle ports  011   a , 011   b  to effect appropriate valve, fuel injection, and ignition timing for sustained operation as further explained below.  
         [0055]    The engine also has common exhaust/inlet ports  07   a , 07   b  which perform the dual functions of exhausting combustion gasses and admitting atmospheric air for propulsion, scavenging, and cooling. Exhaust/inlet ports  07   a , 07   b  are opened and closed by valves  05   a , 05   b  and associated actuators  013   a , 013   b  which sense obturation of exhaust/inlet ports  07   a  and  07   b  and enforce the appropriate valve action of valves  05   a ,  05   b ,  014   a , and  014   b.    
         [0056]    The valves, actuators, fuel injectors, and igniters for the first embodiment are conventional elements whose description will be omitted here for the sake of brevity.  
         [0057]    The operational cycle is defined as follows:  
         [0058]    Referring to FIG. 2, piston  03  is positioned in cylinder  02  such that the air charge and fuel mixture in chamber  010   a  is at the required combustion pressure. With piston  03  in this position, igniter  09   a  is energized to initiate combustion in chamber  010   a  and begin the cycle. As further shown in FIG. 2, nozzle valve  6   b  is open, nozzle valve  06   a  is closed, and valves  05   a , 05   b  are closed at this part of the cycle and piston  03  begins accelerating to the right due to the combustion pressure in chamber  010   a  (dashed line arrows indicate movement).  
         [0059]    As piston  03  moves to the right under the impetus of the combustion pressure in chamber  010   a , the air/exhaust mixture in  010   b  is compressed and expelled through nozzle port  011   b , open nozzle valve  06   b  and thrust nozzle  04   b , thus generating the thrust Tb.  
         [0060]    As shown in FIG. 3, when piston  03  crosses exhaust/inlet ports  07   a , actuator  013   a  senses port  07   a  closure and opens nozzle valve  06   a  and causes actuator  13   a  to open exhaust/inlet port  07   a  via the valve  05   a . FIG. 4, shows the opened state of nozzle valve  06   a  and exhaust/inlet port  07   a . At this point, piston  03  reaches its maximum velocity.  
         [0061]    The remaining unexpanded low-pressure combustion gasses are then exhausted through exhaust/inlet port  07   a  and nozzle port  011   a , nozzle valve  06   a , and thrust nozzle  04   a . Meanwhile, piston  03  continues to travel to the right in cylinder  02  due to its inertial energy. The continuing rightward movement of piston  03 , draws atmospheric air into chamber  010   a  through exhaust/inlet port  07   a  and nozzle  04   a . Nozzle  04   a  is open at this event time to provide scavenging and dilution of the exhaust products.  
         [0062]    The distance between nozzle port  011   b  and cylinder wall  012   b  is prefixed such that the mass of air charge required for subsequent combustion in chamber  010   b  is attained as piston  03  crosses and obturates nozzle port  011   b  as shown in FIG. 4.  
         [0063]    At this point, the loss of high pressure in port  011   b  sensed by actuator  014   b  initiates five actions, shown in FIG. 4: the actuator  013   a  for slide valve  05   a  closes off exhaust/inlet ports  07   a ; the actuator  014   b  closes nozzle port  011   b ; the injector  08   b  injects a metered amount of fuel into chamber  010   b ; actuator  014   a  for nozzle valve  06   a  opens nozzle port  011   a  to nozzle  04   a ; and a delayed signal is sent to fire the igniter  09   b  when piston  03  achieves maximum compression in chamber  010   b  as shown in FIG. 5. The remaining inertial energy of piston  03  is dissipated in achieving the required combustion pressure in chamber  010   b.    
         [0064]    The atmospheric propulsion engine has completed one cycle and is in position to repeat the next cycle in the opposite direction. The sequence of this next cycle can be followed by substituting the a and b components for one another and reversing the piston&#39;s direction.  
         [0065]    [0065]FIG. 6 illustrates how the inventive engine can be utilized to generate reverse thrust. Essentially, the thrust assembly including nozzle port, valve, actuator and thrust nozzle is duplicated. Specifically, nozzle port  011   c  is disposed opposite to nozzle port  011   a  and has attached thereto a valve  06   c , actuator  014   c  and reverse thrust nozzle  04   c . A corresponding nozzle port  011   d  is disposed opposite to nozzle port  011   b  and has attached thereto a valve  06   d , actuator  014   d  and reverse thrust nozzle  04   d . To generate reverse thrust, valves  06   c  and  06   d  would be activated instead of valves  06   a  and  06   b , but with the same timing relationship as for valves  06   a  and  06   b  described above. The result is the generation of reverse thrust Tc and Td.  
         [0066]    [0066]FIG. 7 illustrates a tandem engine design in which two engines  1  are mounted back to back as shown. A tandem configuration joining structure  015  is utilized to affix the two engines  1  to each other in the tandem configuration. In the tandem configuration fuel injection and ignition are synchronized to eliminate reactive engine movements. This synchronization may be accomplished via conventional rack and pinions, linkages, gears, or other mechanical means. Of course, the tandem design may also include a reverse thrust arrangement like the one shown in FIG. 6.  
         [0067]    [0067]FIG. 8 shows a spring centered, slidably mounted engine to allow reactive movements. In other words, the atmospheric propulsion engine can be slidably mounted to a vehicle structure  018  via slidable engine mounts  016   a  and  016   b  and a centering spring mechanism  017  as shown in FIG. 8. In this way, the engine  1  can traverse a small distance back and forth with slidable engine mounts  016   a , 016   b  and centering spring mechanism  017  compensating for reactive forces generated by the engine  1 .  
         [0068]    [0068]FIG. 9 is a schematic showing how the unicycle engine indicated by reference  1  can be integrated into an operating system containing adjunct fuel and electrical systems. Gas lines  019  with check valves  028   a  and  028   b  are picked off of cylinder  02  to pressurize high pressure gas reservoir  020  and feed the pressurized fuel tank  021  and turbine generator  023 . The fuel lines  022  feed fuel to fuel injectors  08   a  and  08   b . Turbine generator  023  charges battery and electronics package  024  which transmits a timed firing signal to igniters  09   a  and  09   b  at the predetermined event time through electrical lines  025 . Appropriate sensors may be utilized to sense the position of the piston via obturation of ports  07   a , 07   b , 011   a , and  011   b  so that the actuators  013   a , 013   b , 014   a , 014   b  as well as the fuel injectors  08   a , 08   b  and igniters  09   a , 09   b  can be activated at the correct timing relationship that is described above. These sensors and activators may be, for example, electrical or pneumatic.  
       Description of Second Embodiment  
       [0069]    Referring to FIG. 12, the primary elements of a second embodiment of the invention which is essentially a free piston intermittent pulse rocket engine includes two combustion cylinders,  2   a  and  2   b , coaxially located within, and separated by, a thrust chamber cylinder  7 . The combustion pistons  3   a ,  3   b  and thrust piston  4  are connected and slidably inserted into cylinders  2   a ,  2   b , and  7  respectively, forming combustion chambers  5   a , 5   b  and thrust chambers  6   a , 6   b . Intake check valve assemblies  20   a , 20   b  provide a valved inlet for air into thrust chambers  6   a , 6   b  via thrust intake ports  19   a , 19   b.    
         [0070]    The opposing ends of combustion cylinders  2   a , 2   b  are closed by cylinder heads  21   a , 21   b  that contain fuel injectors  18   a , 18   b , respectively. Fuel injectors  18   a  and  18   b  are fed by the pressurized fuel supply line  28 . The opposing ends of thrust chambers  6   a , 6   b  are closed by thrust chamber flanges  8   a , 8   b.    
         [0071]    Injector control gas ports  16   a , 16   b  are provided in cylinders  2   a , 2   b  and are connected to injector gas control lines  17   a , 17   b , respectively. The other ends of injector gas control lines  17   a ,  17   b  are, in turn, connected to fuel injectors  18   a , 18   b . As further described below, injector control gas ports  16   a , 16   b  activate fuel Injectors  18   a , 18   b  as combustion pistons  3   a , 3   b  cross respective injector control gas port  16   a , 16   b  while moving on the compression stroke.  
         [0072]    Exhaust ports  9   a , 9   b  formed in combustion chambers  2   a , 2   b  allow for expulsion and scavenging of burnt combustion gases via exhaust ducts  10   a , 10   b  and exhaust thruster nozzles  11   a , 11   b . Scavenge purge lines  14   a , 14   b  allow high pressure air from thrust chambers  6   b , 6   a  to scavenge combustion chambers  5   a , 5   b  through scavenge ports  12   a , 12   b  and scavenge inlet ports  15   a , 15   b , when pistons  3   a , 3   b  opens combustion chambers  5   a , 5   b  to exhaust. Scavenge port check valves  13   a , 13   b  prohibit counter-flow during the combustion, expansion and compression cycles of each combustion cylinder as further described below. Thrust chamber exhaust separators  24   a , 24   b  ensure separation of exhaust from combustion chambers  5   a , 5   b  to thrust chambers  6   a , 6   b.    
         [0073]    Main thruster check valves  22   a ,  22   b  interconnect main thruster nozzles  23   a , 23   b  with thruster ports  25   a , 25   b  and thrust chambers  6   a , 6   b , respectively.  
         [0074]    Pneumatic starter valves  26   a ,  26   b  allow compressed air from a compressed air source (not shown) to enter combustion chambers  5   a , 5   b  and permit engine starting.  
       Operation of Second Embodiment Engine  
       [0075]    Operation of the engine will be described here, while construction and operation of the preferred fuel injector  18  will be described in following paragraphs.  
         [0076]    Assume that piston  3   a  is in its compression position to the left of cylinder  2   a  as shown in FIG. 13. When piston  3   a  is in its compression position, the volume of chamber  5   a  is at its minimum, and compression pressure therein is at a maximum. Fuel injection has been accomplished and combustion is underway. Piston  3   b  has opened chamber  5   b  to exhaust through ports  9   b , exhaust duct  10   b  and exhaust nozzle  11   b . Thrust chamber  6   a  has completed expulsion of its thrust gas and its pressure is approaching atmospheric. Thrust chamber  6   b  has completed its air intake stroke and is near atmospheric pressure. Injector gas control port  16   a  is at atmospheric pressure through exhaust port  9   a . Check valve  13   a  is closed since thrust chamber  6   b  is at low intake pressure.  
         [0077]    As the combined piston ( 3   a - 4 - 3   b ) begins moving to the right under the impetus of compression pressure and fuel combustion, the following actions occur:  
         [0078]    Thrust chamber  6   a  begins intake of air through check valve  20   a , while check valve  25   a  prevents entry of air through nozzle  23   a.    
         [0079]    Pressure builds up in thrust chamber  6   b  with the subsequent expulsion of air and generation of thrust through thruster port  25   b , check valve  22   b  and nozzle  23   b . Check valve  20   b  prevents loss of air through the inlet port  19   b.    
         [0080]    Piston  3   b  begins closure of cylinder  2   b  exhaust ports  9   b.    
         [0081]    As shown in FIG. 14, when the combined piston ( 3   a - 4 - 3   b ) has moved right to the point where piston  3   b  has closed cylinder  2   b  exhaust ports  9   b , the following actions have taken place or now occur:  
         [0082]    Piston  3   b  begins compression of the combustion air in chamber  5   b.    
         [0083]    Piston  3   a  has uncovered scavenge port  12   a , but check valve  13   a  prevents any flow.  
         [0084]    Piston  3   a  has uncovered injector gas control port  16   a  and reset of the injector  18   a  for the next cycle has begun. This will be explained in a following paragraph describing injector operation.  
         [0085]    Expansion of combustion gas in chamber  5   a  is increasing the velocity of piston  3   a - 4 - 3   b  to the right.  
         [0086]    Under the impetus of piston  4 , pressure is increasing in chamber  6   b , with the resultant increase of mass flow and thrust out of nozzle  23   b.    
         [0087]    Chamber  6   a  is ingesting atmospheric air through valve  20   a.    
         [0088]    As shown in FIG. 15, when piston  3   a  is around mid point of its stroke in cylinder  2   a , its maximum velocity is attained, and it begins to decelerate due to the pressure degradation in chamber  5   a  and the opposing forces generated by the increase in pressures in chambers  6   b  and  5   b.    
         [0089]    As shown in FIG. 16, when piston  3   a  crosses exhaust ports  9   a , the following events have taken place or now occur:  
         [0090]    Chamber  5   a  is vented to atmosphere through ports  9   a  and exhaust nozzle  11   a , with some thrust generation.  
         [0091]    The pressure in chamber  5   a  drops below the pressure in chamber  6   b , thus allowing fresh air from chamber  6   b  to enter chamber  5   a  through port  15   b , line  14   a , check valve  13   a , and port  12   a . This air then scavenges chamber  5   a  through exhaust ports  9   a  and exhaust nozzle  11   a . Note that the scavenged air is not wasted, but used to generate thrust through exhaust nozzle  11   a.    
         [0092]    Piston  3   b  is approaching the point of maximum compression in chamber  5   b.    
         [0093]    Piston  3   b  has crossed injector gas control port  17   b  and communicated it with exhaust ports  9   b  and nozzle  11   b.    
         [0094]    This begins activation of fuel injector  18   b . This function will be explained in a paragraph. describing injector operation.  
         [0095]    Chamber  6   b  is reaching maximum pressure, mass flow through check valve  25   b  and nozzle  23   b , and is generating maximum engine thrust output.  
         [0096]    As shown in FIG. 17, the mass inertia of piston  3   a - 4 - 3   b  then carries it to the point of maximum compression pressure in chamber  5   b , and its velocity reaches zero. At this time, the following conditions exist and the engine repeats the foregoing cycle in the opposite direction as follows:  
         [0097]    Fuel injector  18   b  is injecting fuel into combustion chamber  5   b  and combustion has begun.  
         [0098]    The pressure in thrust chamber  6   b  has decayed to atmospheric and scavenging of chamber  5   a  is complete, while chamber  5   a  remains open to exhaust and check valve  13   a  ceases interflow between  6   b  and  5   a.    
         [0099]    Thrust chamber  6   a  has ingested its maximum volume of air and is at near atmospheric pressure.  
         [0100]    Starting of the engine may be accomplished via pneumatic starter valves  26   a , 26   b . Specifically, a source of compressed air may be connected to at least one of the pneumatic starter valves  26   a  or  26   b . For example, compressed air may be passed through pneumatic starter valve  26   a  and enter combustion chamber  5   a  thereby moving the piston ( 3   a - 4 - 3   b ) to the right until the operational state shown in FIG. 17 is achieved. At this point, the fuel injector  18   b  injects fuel into combustion chamber  5   b , combustion begins, and the engine starts. Alternatively, a conventional igniter can be added to at least one of the cylinder heads  21   a ,  21   b  and utilized as a starting means with appropriate utilization of the pneumatic starter valves to inject compressed air to move the combined piston  3   a - 4 - 3   b  to a desired position, actuate a fuel injector  18  and thereby start the engine. Furthermore, pneumatic starter valves could also be added to the engine  1  of the first embodiment as an alternative method of starting that engine.  
         [0101]    Furthermore, the system shown in FIG. 9 can be utilized with the engine of the second embodiment as indicated by the common usage of pressurized fuel line  022 .  
       Fuel Injector  
       [0102]    The engine of the second embodiment is preferably equipped with the fuel injector shown in FIG. 18. For ease of reference, fuel injectors  18   a  and  18   b  will be collectively referred to as fuel injector  18  it being understood that the same fuel injector  18  design is used for both  18   a  and  18   b.    
         [0103]    As shown in FIG. 18, the self-actuated, uniaxial fuel injector  18  consists of an injector body  50  into which is slidably mounted an intensifier piston  53  containing a slidably mounted fuel pintle  52 , closure spring  56 , and pintle stop  55 . All of these elements are coaxially located. An annular intensifier piston cylinder stop  54  is attached on the combustion chamber side of the injector body  50  to constrain motion of the intensifier piston  53 . On the opposite end, a fuel quantity plug and stop  51  with seal  64  is centrally located and threadably inserted into the injector body  50 .  
         [0104]    The fuel quantity plug and stop  51  contains the pressurized fuel inlet connection  36 , fuel inlet passage  62 , and check valve  63 . The check valve  63  allows fuel to flow into the fuel cavity  65  when the cylinder pressure PI is less than the inlet fuel pressure P 4 , enabling the fuel cavity  65  to refill and reset the intensifier piston  53  when the combustion cylinder enters the exhaust phase. The threaded insertion of the fuel quantity and plug  51  into the injector body  50  allows for simple adjustment of the amount of fuel metered for each injection cycle.  
         [0105]    When installing the fuel injector  18 , the pressurized fuel inlet connection is connected to pressurized fuel line  022 .  
       Operation of Fuel Injector  
       [0106]    The fuel injector  18  accomplishes the following functions: meter the amount of fuel required for a single combustion action; contain that fuel until injection is required; multiply the fuel injection pressure by the ratio of A 1  to A 2  above the cylinder compression pressure; inject the fuel into the combustion chamber when the engine piston crosses the gas control port; reset the pintle and intensifier piston, and refill the injector for the next cycle.  
         [0107]    Refer to FIGS. 12 and 18 and assume that injector  18  is filled with fuel (fuel cavity  65  and passages  62  and  66 ) and ready to perform the injection function. As pressure (P 1 ) rises in the cylinder chamber  5  during compression, the control gas inlet  28  (P 3 ) and chambers  58 ,  60  and  61  track this pressure through gas control port  16  and injector gas control line  17  until piston  3  crosses gas control port  16 . During this period, the annular volume and area  60  (P 3 ) is at the same pressure as the compression chamber  5  (P 1 ), thus, that portion of A 2  is counterbalanced and the effective area under P 1  is equal to A 1 . Since the top area of the slidable intensifier piston  53  in contact with the incompressible fuel in fuel cavity  65  is also equal to A 1 , the pressure in fuel cavity  65  (P 2 ) is equal to P 1 . Also, since the gas control pressure P 3  is communicated to control gas pintle cavity  61 , the areas and pressures on top and bottom of the pintle  52  being equal, this allows the pintle closing spring  56  to maintain the pintle  52  in the closed position, thus preventing fuel flow into the cylinder chamber  5 .  
         [0108]    When the piston  3  has crossed gas control port  16 , control gas inlet  28  (P 3 ), passage  57  and chambers  58 ,  60 , and  61  are vented to atmosphere through injector gas control line  17 , gas control port  16 , exhaust port  9 , and exhaust nozzle  11 . When this occurs, the effective area of the intensifier piston  53  exposed to the compression pressure P 1  is now equal to A 2 , while the effective area on the opposite end in contact with the fuel in cavity  65  (P 2 ) is still equal to A 1 . Thus, the fuel injection pressure P 2  increases in the ratio of A 2  to A 1  (P 1 ×A 2 =P 2 ×A 1 ) . This pressure increase is consistent with the operation of a conventional intensifier piston.  
         [0109]    Typically, a cylinder compression pressure P 1  of 1000 psi, might yield a fuel injection pressure P 2  of 4000 psi, but this can be tailored for any specific design by appropriately adjusting, for example, A 2  and A 1 . At the same time, the release of pressure in pintle cavity  61  allows compression pressure P 1  and the increased fuel injection pressure P 2  to act on the pintle  52  nose at injection nozzle  67 , overcoming the force of the pintle closing spring  56  and causing the pintle to snap open. Fuel is now injected into combustion chamber  5  at pressure P 2  until the fuel cavity  65  is depleted and the intensifier piston  53  contacts fuel quantity stop and plug  51  as shown in FIG. 19. Pressure P 2  then drops to the more benign pressurized fuel inlet value P 4 , and any further fuel flow through the fuel delivery passage  66  is prevented by its inlet being in contact with the stop  51 . This state and mechanical condition of fuel injector  18  remains constant until there is a change in the gas control pressure P 3 .  
         [0110]    As piston  3  in cylinder  2  reverses direction for its power stroke under the impetus of compression pressure and combustion, piston  3  recrosses injector gas control port  16 , again communicating control gas inlet  28  (P 3 ) with combustion pressure P 1  through injector gas control port  16  and gas control line  17 . Gas control chambers  58 ,  60 , and  61  then rise pressures equal to P 1 . Pintle  52  now has equal pressures on both ends, therefore, the pintle closing spring  56  causes the pintle  52  to return to its closed position as shown in FIG. 20, expelling any residual fuel in its cavity. Intensifier piston  53 , however, has an effective area of A 1  exposed to pressure P 1 , and since P 1  is much higher than the fuel supply pressure P 4 , intensifier piston  53  will remain against stop  51  until piston  3  uncovers exhaust ports  9 , and P 1  in combustion chamber  5  decays to near atmospheric pressure. At this point, the fuel supply pressure P 4  is greater than the chamber  5  pressure P 1 , fuel cavity  65  refills until intensifier piston  53  reaches piston cylinder stop  54 . The fuel injector  18  is now reset, primed and ready for the next injection cycle.  
         [0111]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.