Abstract:
This invention describes a miniaturized hybrid diesel-electric engine formed by a closed-loop system powered by plasma-aided combustion of JP-8 fuel (or other hydrocarbon fuels) working in tandem with a vapor cycle utilizing miniaturized expanders and condensers. The output of this engine is electric power and mechanical work. Water, or organic fluids, heated by the combustion product developed inside a special burner, undergoes an explosive, quasi-supersonic conversion to steam. This steam drives a high-speed turbine connected together with a gas turbine outputting shaft work. This work output is utilized to power internal subsystems, cool down the miniaturized condensers, and to produce torque and electric power. The dimensions of this miniaturized hybrid-engine are so compact that it can fit inside the battery compartment of most applications requiring high-density miniaturized power sources.

Description:
[0001]     This is a continuation of application Ser. No. 10/261,685, filed Oct. 2, 2002, which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The conversion of compact gasoline spark ignition engines to diesel or heavy-fuels operated engines for various applications requiring miniaturized power sources, including robotics and exoskeleton, and small scale propulsion system, forces a series of adaptation of the current off-the-shelf engines. These adaptations allow a conventional miniaturized gasoline engine to be fueled by heavy-fuels at the expense of significant inefficiencies. Most of these diesel operated gasoline engines have serious ignition difficulties, especially at sub-zero temperatures, and generally show poor performance with respect to the actual power available for energy extraction from the fuel. Furthermore, increased fuel consumption with production of heavy smoke and pollutant emissions, and several other negative factors, severely penalizes the adoption of these modified engines. The need for air-breathing small-scale propulsion systems, with high power densities for civilian and military applications is ever increasing. The objective of the present invention is to provide a small-scale hybrid-engine (SSHE) formed by the integration of several technologies allowing its miniaturization without impairing the overall engine efficiency.  
         [0003]     A secondary objective of the proposed invention is that of providing a wearable power source equipped with its own fuel tank, pumps, starter mechanisms, mufflers, injectors, etc. This wearable, or mobile, SSHE system can deliver a minimum of 20 W average for prolonged amounts of time with minimum fuel consumption, and load following characteristics. SSHE can also produce a scalable power output able to achieve and exceed this minimum power requirement so that it can serve multiple applications. Such applications may require a power source for power hungry systems such as microclimate cooling with power requirements in excess of 1200 W-hr, or able to provide shaft power for actuators used for robotic applications, or as a propulsion system for remotely controlled vehicles. Load following characteristics imply a rigorous control of the various combustion parameters forcing a fast response on the rotating components of the burner. All components are designed for minimum weight and bulk. Components like miniaturized compressor and exhaust gases wheels impose high degrees of manufactory accuracy and complexity. All of the components of this invention can function in a wide range of temperatures and environments, including submerged in water, while resisting to shocks derived from mechanical impacts or explosions. The complete system is reliable and damage-tolerant, posing no hazards to the operator.  
         [0004]     To meet these requirements, technology has been pushed beyond its current limits and the integration of several innovative concepts produced the SSHE. Every ounce of mass of the SSHE system contributes to performance, and every watt generated, thermal, electrical, or mechanical is applied with the highest conversion efficiency. These are the main objectives of the SSHE proposed as a miniaturized power source utilizing fossil fuels.  
       SUMMARY OF THE INVENTION  
       [0005]     The heart of the Small Scale Hybrid Engine (SSHE) is a special fluid-expanding cavity thermally coupled with a plasma-aided hydrocarbon burner equipped with a U-turn combustion gases circuit. The combustion cycle executed by the burner works in tandem with a Rankine-like vapor cycle operating between a hot source formed by the combustion products and a cold source formed by a heat transfer mechanism between the burner intake air and special condensation cavities. The cold source is a highly conductive-to-convective heat transfer surface in thermal contact on one side with the large mass flow rate of intake air. This condensing cavity discharges the excess heat from the working fluid in a closed loop to the environment while providing the muffler structure of the burner capsule for sound abatement. Efficiency of the vapor-combustion cycle is estimated at approximately 54% for a JP-8 fueled SSHE. Combustion energy is also stored in the mass of the thermal reservoir structure forming a thermal flywheel, and can rapidly be converted into pressure, and mechanical work, using the fluid expanding cavity which achieves extremely high heat transfer rates from the thermal reservoir to said working fluid. The heat energy thus transferred to said working fluid is applied to an electronically controlled alternator/starter whose rotor is embedded in the vapor turbine or in a separate disk for electric production. Said vapor turbine is also mechanically linked to an exhaust gas turbine driven by the expansion of combustion gases inside the core of the burner structure. Said turbines produce torque for electric production as well as shaft power mechanically transferred via geared coupling for different rpm between the turbines themselves while providing a mechanical coupling for a torque output of the SSHE. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1 ; Is a schematic representation of the SSHE internal structures with flow lines indicating the combustion gases circuit and the vapor-cycle formed by a closed loop integrating the working fluid tank, sealed hydraulic connections, pump(s), double counter flow fluid expanding heat transfer system, and the condensing cavities.  
         [0007]      FIG. 2 ; Is a schematic representation of the SSHE internal structures with flow lines indicating mainly the fossil fuel burning cycle formed by special fuel expanding injection, ionization, and ignition systems, a U-turn exhaust gas circuit coupled with high heat transfer rate working fluid expanding systems. Said fossil fuel burning cycle including fuel tank, pump, starter all self contained inside the SSHE structure.  
         [0008]      FIG. 3 ; Is a schematic representation of the electric alternator/starter embedded inside the SSHE rotating components, showing the position of rare earth magnets, coils, and the electronic controller.  
         [0009]      FIG. 4 ; Is a block diagram of the CPU control system all integrated in a printed circuit.  
         [0010]      FIG. 5 ; Is a representation of a complete SSHE unit showing the turbine assembly and the cylindrical nature of all cavities within which the working fluid expands and condenses while the exhaust gases transfer heat inside the burner.  
         [0011]      FIG. 6 ; Is a representation of a complete SSHE unit assembled inside a power pack having dimensions similar to those offered by a typical battery for the high density power output.  
         [0012]      FIG. 7 ; Is a representation of a complete SSHE unit integrated inside a compact self sustained power pack showing a mechanical coupling able to transfer shaft power to external mechanical applications (i.e. compressors, impeller, propellers, pulleys, etc.) while still able to provide electric power at its output.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0013]     The working principles of the SSHE system are now described by utilizing the schematics and representations shown in  FIGS. 1-7 .  
         [0014]     In  FIG. 1 , two cylindrical fluid expanding cavities  1 , and la, here shown in cross-section view, are assembled around the basic structure of the SSHE combustion chamber  4 . The body of the fluid-expanding cavity la is formed by concentric and sealed cylinders-like structures separated by a gap within which the working fluid  10  contained inside a toroidal storage tank  11  expands. Tank  11  shown in  FIG. 1  is not to scale. Similarly, the body of fluid-expanding cavity  1  is formed by concentric sealed cylinders internally separated by a gap within which the working fluid  10  expands. Said working fluid  10  is pumped at relatively high-pressure inside the fluid expanding cavity  1   a  through one or more high-pressure miniaturized pump(s)  8  geared through a gear assembly  12  to a set of turbines  13 ,  14 , and  15  linked to the same shaft  9 . The high-pressure pump  8  is a piston driven positive displacement pump. Each stroke of pump  8  delivers an amount of working fluid  10  proportional to the rotating speed of shaft  9 . Pump  8  is hydraulically connected to a high-pressure fluid injector  16  acting as a check valve. When pump  8  is set in motion by the alternator/starter system  23  (shown in  FIG. 3 ), high pressure working fluid  10  is throttled inside the fluid-expanding cavity  1   a  through check valve  16 . Sub-cooled liquid working fluid  10  is now exposed to a heat transfer thermodynamic process since the inner surfaces of said fluid-expanding cavity  1   a  are in thermal contact with the combustion gases  19  produced inside combustion chamber  4 . The outer surfaces of fluid-expanding cavity  1   a  are kept at almost adiabatic conditions by means of thermally insulating materials  17  surrounding fluid-expanding cavity  1   a  and  1 . The working fluid  10  exits fluid injector  16  and expands in a counter-flow fashion with respect to the direction of the hot combustion gases  19 . It reaches the bottom of the burner structure  20  and enters hydraulic connections  2  disposed radially and exposed to the high temperatures of the combustion gases  19 , without mixing with said gases. These hydraulic connections  2  allow the expanding fluid  10  from cavity  1   a  to enter fluid-expanding cavity  1  and undergo an additional heat transfer and thermodynamic process to increase its energy content. While transiting inside fluid-expanding cavity  1  in a counter-flow fashion with respect to the direction of the combustion gases  19 , heat transfer occurs through the inner walls and surfaces of fluid-expanding cavity  1  so that at its outlet  5  the working fluid  10  is at high pressures and temperatures, in a superheated state. Fluid expanding cavity  1  is thermally insulated from the air intake manifold cavity  18  surrounding the structure of said fluid expanding cavity  1 . Through hydraulic and sealed connection between  5  and  5   a  (see also  FIG. 3 ), said superheated working fluid is allowed to expand through one or more nozzles  6  into a set of high-pressure vapor-turbine(s)  14  co-axially and mechanically linked with shaft  9 . The mechanical connection of said vapor turbine  14  can be directly coupled to shaft  9 , or indirectly coupled to shaft  9  by means of gear changing the speed ratio. At the outlet of blades  7  of turbine(s)  14  the expanded working fluid  10  flows through hydraulic vapor venting connections  21  inside a condensing cavity  22  surrounding all other cavity structures. The condensing cavity  22  is formed by concentric cylinders-like sealed and positioned so as to form a gap in between the outer surface of the inner cylinder and the inner surface of the outer cylinder. Inside this gap the expanded working fluid  10  releases heat to the intake air manifold via the inner walls of said condensing cavity  22  without mixing with said intake air. The expanded working fluid  10  also releases heat to the outer wall of said condensing cavity  22  via natural or forced convection with the environment surrounding said condensing cavity  22  through fins  22   a  positioned radially along the SSHE body. The expanded fluid  10  releases heat along the whole length and surfaces of the condensing cavity  22  such that the induced temperature drop causes the expanded working fluid  10  to return to a sub-cooled liquid state. The suction of pump  8  can be positioned anywhere along the working fluid collective tank formed by tank  11 , surrounding the top structure of the SSHE, the hydraulic connections to the condensing cavity  22 , and inside the gap itself of condensing cavity  22 . Shaft  9  is also geared to a set of speed reducing/increasing gears  45  (more in detail in  FIG. 3 ), which provide speed adjustment for the different turbines  13 ,  14 , and  15  and a mechanical outlet equipped with a coupler  44  so as to provide external shaft power to the user at the desired torque and rpm. This concludes the closed loop SSHE vapor cycle of working fluid  10  described in  FIG. 1  and  FIG. 3 .  
         [0015]     The burner side of the SSHE system is best described in  FIG. 2 . At the top of  FIG. 2 , the electric alternator/starter formed by a rotating disk  23  receives shaft power from shaft  9  whose torque magnitude is the result of the expansion of combustion gases  19 , produced in the combustion chamber  4 , and the expansion of working fluid  10  through the high-pressure vapor turbine(s)  14 . Air  24  enters the SSHE from an air filter  25  positioned above the intake of compressor turbine  13 . To reduce acoustic signature caused by the inlet air-flow, and especially by the high speed (10,000 rpm range) of the compressor turbine  13 , the inner walls of the intake manifold are lined with sound absorbing materials  26 , thereby forming the intake muffler  27 . For a 20 W-electric power output the overall weight of the SSHE rotating parts is low enough to make gyroscopic effects negligible. The air filter  25  can be positioned on the circumference of the SSHE or anywhere along the intake air path. In both cases the SSHE inlets can be made water sealed by turning said air filter casing  27  or by pressing it against the compressor wheel  13  inlet. When this operation is executed, an air-flow sensor embedded anywhere in the air intake path utilized by the SSHE computer controller  25   a  for fuel metering purposes detects the rapid change in inlet pressure, and the SSHE fuel control system immediately deactivates the fuel pump  26  or the fuel vaporizing and injecting system  27  to shut down the burner. This feature allows the submersion of the SSHE, while electric power is still provided thanks to start-up and back-up batteries  28 . The capacity of these batteries determines the time the SSHE can be submerged and still provide full power to the user. For a 20-Watt average power demand a relatively small ion-lithium battery  28  used to start the SSHE can maintain the required power output for several hours with the SSHE burner in shut-down mode. The bearings (not shown in  FIG. 2 ) for the compressor turbine  13  and the alternator/starter shaft (coupled directly or indirectly with drive shaft  9 ), can be made of self-lubricating materials, or lubricated by a closed loop oil circulation system geared with the drive shaft  9 .  
         [0016]     When air  24  enters the suction side of the compressor turbine  13 , it undergoes a compression process while channeled into the jacket-like hydraulic structure  18  surrounding the burner. Structure  18  forms a cavity in thermal contact with the condensing cavity  22  but thermally insulated from combustion gases  19 . In this manner, a relatively large mass flow of cold air is forced into contact with the surfaces of the condensing cavity  22  which, in this configuration, is also utilized as a device to cool down the exhaust gases to reduce thermal signature by bleeding cold air through calibrated orifices  33   a . Through the compressor turbine  13 , compressed air  24  is available at the inlet  29  of the burner  4  where mixing with a superheated JP-8 vapor jet occurs. This jet of fuel vapors is produced by a miniaturized heat expanding fuel injection system  27  which converts liquid fuel into superheated fuel vapor instantaneously. Fuel  30  is stored in a semi-toroidal tank  30   a  (not to scale), positioned above and surrounding the structure of compressor turbine  13 , and pumped into heat expanding fuel system  27  through fuel pump  26 . At start-up the heat expanding fuel injection system  27  is electrically heated through a heater  27   a  powered via electronic control from CPU circuit  25   a  by the start-up battery  28 . Soon after ignition of the burner the temperature of this heat expanding fuel injection system  27  is kept at the proper level through heat transferring from the exhausting combustion gases  19 . At the burner inlet  29 , JP-8 vapors and air undergo a violent ionization shower through symmetrical electrodes  31  powered by a controlled cold plasma generator  32 . Ionized species formed via cold corona discharge increase mixing favoring combustion while containing the air fuel mixture away from the metal walls of the surrounding structure to minimize fuel condensation. An instantaneous wall of approximately 5,000° C. plasma-flame is then formed in front of the ionized mixture through hot plasma electrodes  32  controlled by a hot plasma generator and controller  33 . The ionized air fuel mixtures ignites and expands in the combustion chamber  4 . Virtually any fuel available will ignite under these conditions, thereby SSHE can operate with several types of liquid or gaseous fuels. While expanding, the high-pressure, high-temperature exhaust combustion gases  19  enter the exhaust gas turbine  15  powering the alternator/starter system  23  and the compressor wheel  13  in tandem with the torque generated by the vapor cycle through high-pressure turbine(s)  14 . The shaft work generated by the combustion process also provides power to the fuel-pump  26  geared with the exhaust gas turbine  15  via drive shaft  9 . Exhaust combustion gases  19  circulate inside the body of the SSHE and transfer heat to the surfaces of the condensing cavity  1   a  and  1 . To decrease thermal signature due to the high temperature of the exhaust gases  19  these gases can be mixed with cold air  24  bled from the compressed air burner intake manifold  33   a . This process is inefficient, but provides significant cooling to the exhaust gases  19  before they enter the muffler  34 . Said muffler  34  is lined with sound absorbing materials  26 , thereby reducing thermal and acoustic signature. Therefore, exhaust combustion gases  19  will exit the SSHE unit with reduced temperature and noise since the outlet muffler  34  is lined with sound absorbing materials  26  shaped to reduce the sound produced by the combustion processes and the turbines operation. A flexible membrane  35  is positioned at the outlet of the muffler  34  forming a check valve automatically sealing the SSHE when submerged. Overall, the SSHE is designed with multiple barriers to heat and sound. The fluid expanding cavities  1   a , and  1 , and the condensing cavity  22  by being formed by series of concentric cylinders become a heat and sound shield while making the SSHE structure extremely compact and damage tolerant.  
         [0017]     In  FIG. 3 , the SSHE electric power generator or alternator and starter is shown. This electric alternator is an electronically controlled alternator-starter formed by a rotating disk  23  symmetrically containing rare earth magnets  35 , magnetically coupled with symmetrical stationary coils  36 . As shown in  FIG. 3 , representing the “head” of the SSHE, a series of multiple permanent magnets such as Ferroxdure, consisting of anisotropic sintered barium, or similar sinterized materials, are positioned on the circumference of the rotor or embedded with disk  23 . Similar results can be obtained by embedding said permanent magnets  35  with the air compressor wheel  13 , or vapor turbine  14 , or exhaust gas turbine  15  in which case the rotor disk  23  is not necessary. The symmetric coils  36  of this alternator are embedded in the SSHE head housing or stator. These coils are connected to a bridge of high-frequency switching transistors (i.e., power MOSFET) driven by a custom made specialized computer  37  controlled by CPU system  25 . The printed circuit containing all of the electronic components for the CPU system  25  (CPU card) is positioned in the vicinity of the rotor disk  23 . The electric connections from the coils  36  to the power MOSFET  38  are extremely short to minimize electromagnetic noise production as a result of the fast switching. MOSFET  38  are exposed on one side to the intake air-flow through symmetrical fins  38   a , thereby providing cooling. The electronic circuit utilizes electromagnetic interference suppression technologies (i.e., surface mount ferrite bead EMI) and an internal switching power supply to minimize irradiation of electromagnetic noise to the electronic systems feeding from the SSHE. The heat generated by the coils and MOSFET  38  switching is easily removed by fins  38   a  exposed to the high rate flowing of air  24  at the discharge of the compressor turbine  13 . A thermal barrier  46  insulates the electronic equipment of the alternator assembly formed by the rotating disk  23 , printed circuit  37  including CPU system  25  formed by microchips, components, sensors, etc. Thermal barrier  46  also insulates the air intake circuit to avoid unwanted heating of the air through heating of the metal rotating components such as the exhaust combustion gas turbine  15 . For these reasons drive shaft  9  is formed by at least two parts or shafts coupled and concentric. Drive shaft  9  is made to withstand high temperatures, while concentric shaft  9   a , essentially prolonging shaft  9 , is designed to thermally de-couple the high-temperature side of the SSHE from the low temperature side.  
         [0018]     In  FIG. 4 , the electronic system diagram block is shown. The electronic control system is primarily composed of sensors and actuators designed to provide the CPU with the required information to regulate the output of the SSHE. The entire CPU structure indicated by the block diagram in  FIG. 4  can be assembled with high degree of miniaturization and fit in the printed circuit board  25  located in the vicinity of the rotating alternator disk  23 .  
         [0019]     At the heart of the system, the CPU is responsible for the proper operation of the entire unit. The SSHE unit can be operated in different modes: start-up, shut-down due to submersion, shut-down due to silent mode operation, or in automatic mode which shuts-down the unit if the intake air flow sensor detects an irregular change in the air pressure. The CPU gathers the user input (startup, shutdown, silent mode, automatic mode), along with the current electrical or mechanical loading needs of the system, and adjusts the actuators to provide the desired effect. The CPU is constantly communicating with the Power System whose job is to regulate the available power based on the CPU&#39;s commands. The Power System receives power from both the battery  28  and the alternator/generator formed by the assemblies including disk  23 , and will combine the two to provide the required output power. The system is designed such that only one power source (alternator/starter  23  or battery  28 ) is actually needed to provide the rated power, and thus, any excess power can be used to either start the SSHE burner or charge battery  28  for use in silent or automatic modes.  
         [0020]     When the power output required by the SSHE is increased, the battery  28  ( FIG. 2 ), the cold plasma controller  32 , and hot plasma generator  33 , can be assembled outside the SSHE structure into a container whose overall geometry and dimensions are the same of those of a conventional high capacity ion-lithium battery, nominally 6×4×2 inches.  
         [0021]     In  FIG. 5 , a preferential but not limiting SSHE configuration is shown. The dimensions of the SSHE are directly proportional to the desired power output starting from a minimum of 20 W electric with dimensions smaller than a soda-can, up to kilowatt power ranges with proportionally increased dimensions. In  FIG. 5 , the water sealing system is formed by a rapid spring-loaded double gate valve  27   a  operated by the user or automatically by the CPU structure in case of detection of water in the surrounding on the SSHE unit.  
         [0022]     In  FIG. 6 , as a complete turn-key system the SSHE work unit  22   b  is mounted inside a container  39  supporting an external fuel tank  40 , the switching power supply  41  (with internal capability for multiple voltage outputs: 12, 5, 3.3 Volts), and a rechargeable battery  42  for start-up and silent mode operations. A JP-8 fueled SSHE assembled in the configuration shown in  FIG. 6  can be made with dimensions similar to those currently shown by a disposable or rechargeable battery, nominally 6×4×2 inches. The surfaces of container  39  exposed to the environment allow extensions for condensing cavities  43  to further reduce thermal signature of the unit. The supporting container  39  is equipped with strap-on connectors for easy wear-ability and integration on the user uniform/equipment. The sides of the container exposed to the environment can also provide protection from puncturing the SSHE parts since they can be made with bullet-proof materials, further reducing acoustic signature. Container  39  is also equipped with a display  45   a  driven by the CPU structure  25   a  indicating fuel consumption and availability, a start-up  46   a  and silent mode or shut-down button  44   a , and various connectors for different voltage output  41   a . In this configuration the SSHE unit is simplified by the elimination of its internal fuel tank  30   a  ( FIG. 2 ), cold and hot plasma controllers  33  and  32 , and start-up back -up battery  28 . The CPU system integrated inside the SSHE unit is connected to the power pack  39  by means of an electrical connector  47  also equipped with hydraulic connections to receive fuel from external tank  40 . In  FIG. 7  the SSHE unit shows the mechanical coupler  44  available for mechanical connection to all utilities requiring mechanical shaft power rather than electric power. However, the CPU structure integrated the SSHE unit can be programmed to provide a desired torque at the mechanical coupler  44  while providing electric power at its electric output. This concludes the technical description of the Small Scale Hybrid Engine operating with fossil fuels.