Abstract:
A rotary engine utilizes an expansion chamber and crescent piston to capture the energy of expanding combustion gases through out substantially all of each revolution of the piston. The rotary engine uses a crescent piston, the movement of which is guided by the combined action of a hub having a saddle supporting the piston and a can track. The invention burns fuel in a separate combustion chamber charged from a coaxially mounted compressor and controlled by a pass gate sentry valve. The rotary engine of the invention is cooled by an internal coolant injection system. The coolant solution may contain a alkaline reagent to react with and neutralize acidic components of the combustion gases which would otherwise remain in the exhaust and contribute to air pollution. The rotary engine of the present invention is adaptable to compression ignition fuels and spark ignition fuels. The invention may be constructed of conventional metallic materials as well as composites and ceramics.

Description:
RELATED APPLICATION INFORMATION  
       [0001]    This application claims benefit of U.S. Provisional Application No. 60/293,390, filed May 23, 2001, which is hereby incorporated by reference. 
     
    
     
       TECHNICAL FIELD  
         [0002]    The generally invention relates to internal combustion engines and, more particularly, to a piston driven rotary-type internal combustion engine.  
         BACKGROUND OF THE INVENTION  
         [0003]    Engine designers are constantly endeavoring to design engines that maximize fuel efficiency while minimizing polluting byproducts of the combustion process. Fuel consumption has both a direct effect on the output of pollutants and the expense for the fuel used. Moreover, increasing the fuel efficiency of machinery using non-renewable resources, such as gasoline derived from oil, is an important social value. Minimizing pollutants minimizes the injurious effects on the environment and benefits the health of society on a global scale.  
           [0004]    There have been many attempts to attain efficiency increases while minimizing pollutants. The rotary engine is one example of such attempts. The principal characteristics of conventional rotary internal combustion engines are well known in the field of art. Generally, a rotary engine uses the pressure of combustion to move a triangular rotor within an epitrochoidal-shaped rotor housing. The four cycles of conventional combustion—intake, compression, combustion and exhaust—each take place in its own portion of the housing. These cycles cause the rotor to rotate an eccentric output shaft geared to the rotor. The rotary engine seemingly would have increased efficiency due to the decrease of moving parts, a combustion event of 270° of the output shaft rotation on every rotation, and better balance, since the rotor and shaft move in the same direction.  
           [0005]    Despite these advantages, the conventional rotary engine has found little commercial success because the long and shallow shape of the combustion chamber hurts both emissions and fuel economy performance with respect to conventional piston engines. The relatively brief time period of the power stroke of the piston on the power portion of the rotary motion does not allow for complete combustion of the fuel. This leads to the exhaust of unburned hydrocarbons that must be cleaned up by a catalytic converter.  
           [0006]    Known rotary engines, though capable of producing relatively high power output for their weight and size, have generally been too complex and, in operation, have exhibited excessively high wear, short useful life and relatively high fuel consumption. In operation, they generally produce undesirably high nitric oxide and unburned or partially burned hydrocarbon outputs. All of these add to problems of air pollution. Thus, the efficiency and emissions goals are not satisfied.  
           [0007]    Another attempt to meet the efficiency and emissions goals is through the use of diesel cycle engines. The diesel cycle uses compression of a fuel and air mixture to ignite a combustion event, rather than a spark. This allows the diesel engine to utilize direct injection of the fuel and a higher compression ratio than ordinary gasoline. The higher compression ratio results in better efficiency than for ordinary gasoline engines. Moreover, diesel fuel has a higher energy density than gasoline. The combination of greater energy density and higher compression results in much-improved fuel efficiency.  
           [0008]    However, diesel cycle engines perform poorly in emissions performance. The combustion in a diesel engine produces significant amounts of polluting nitrogen oxides (NO x ). This is especially true in large-scale uses, such as ship engines, or as power sources for electric generation plants. These NO x  have been addressed primarily through the use of selective catalytic reduction of the nitrogen oxides. Catalytic converter use at large-scale diesel engines, such as ships and power plants, is not always feasible due to costs and space concerns. Therefore, elimination of the formation of NO x  in the combustion chamber has been a focus of technological development.  
           [0009]    One measure to reduce NO x  in diesel engines is through the injection of water into the combustion chamber to reduce the combustion temperature. The goal is to reduce the peak temperature arising at the flame, which results in a reduction in NO x  formation. Forming fewer NO x  equals fewer NO x  emissions from the engine. Typically, the water is injected into the combustion chamber shortly before combustion, during combustion, or is mixed with the fuel before injection. A conventional four-stroke diesel engine usually injects the water towards the end of the compression stroke. The use of water injection on a piston-driven diesel engine addresses the emissions concerns to a certain degree. However, the use of a four-cycle reciprocating engine design still has the inherent efficiency drawbacks of producing only one 180° power stroke for every other cycle of the piston.  
           [0010]    Attempts have been made to design a diesel-fueled rotary engine. U.S. Pat. No. 3,957,021, to Loyd, discloses a rotary diesel engine. Said patent discusses the prior unsatisfactory attempts to utilize diesel fuel in rotary engines. The prior attempts produced unsatisfactory results due to the inability to create sufficient compression in the combustion chamber portion of the rotary housing. The Loyd patent addresses the compression problem by providing a precombustion chamber adjacent to the rotor housing and in communication with the housing.  
           [0011]    A fuel injector is disposed in the chamber for injecting fuel into the supplied combustion air. The combustion air is provided, in part, by a compressor, which ensures a sufficient pressure is maintained to combust the diesel fuel. The introduction of fuel into the precombustion chamber in the presence of high pressure and temperature causes the combustion of the fuel to flash into the working chamber of the housing via an outlet port. The burning continues in the working chamber to cause the rotor to rotate the output shaft.  
           [0012]    U.S. Pat. No. 6,125,813, to Louthan et al., discloses an alternate method of providing a precombustion chamber to a diesel fueled rotary engine without the need for a separate compressor. However, Louthan and Loyd do not address the emissions issues associated with triangular rotors or with the use of diesel fuel, as discussed previously. Therefore, there is a continuing need to provide an internal combustion engine with improved fuel economy and reduced emissions.  
         SUMMARY OF THE INVENTION  
         [0013]    The positive displacement turbine solves many of the above-indicated problems of rotary engines by providing a rotary engine, which produces an exhaust low in air pollutants while operating efficiently and requiring minimal cooling.  
           [0014]    The positive displacement turbine generally comprises a separate compressor, combustion chamber and expansion chamber. The expansion chamber utilizes a crescent-shaped piston, a hub and a cam track in order to extract maximum energy from expanding combustion gases. The positive displacement turbine may also utilize an internal coolant injector system. The coolant injector system assists in cooling the positive displacement turbine, improves efficiency by water injection, and injects a chemical exhaust precipitator into the combustion chamber to react with and precipitate pollutants from the exhaust stream, leaving only carbon dioxide and a few inert gases to escape into the atmosphere.  
           [0015]    The positive displacement turbine is adaptable for use with many different fuels, including diesel fuel, gasoline and gaseous fuels including hydrogen. It is adaptable and scaleable for various-sized applications. The invention is also well-adapted to be manufactured from non-traditional engine materials such as composites and ceramics. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 is a sectional view of the positive displacement turbine according to an embodiment of the present invention;  
         [0017]    [0017]FIG. 2 is a front sectional view of a combustion chamber according to an embodiment of the present invention;  
         [0018]    [0018]FIG. 3 is a sectional view of a pass gate sentry valve according to an embodiment of the present invention;  
         [0019]    [0019]FIG. 4 is a top elevational view of the combustion chamber of FIG. 2 according to an embodiment of the present invention;  
         [0020]    [0020]FIG. 5 is a side sectional end view through and expansion chamber according to an embodiment of the present invention;  
         [0021]    [0021]FIG. 6 is a side elevational view of a crescent piston according to an embodiment of the present invention;  
         [0022]    [0022]FIG. 7 is a front elevational view of the crescent piston of FIG. 6 according to an embodiment of the present invention;  
         [0023]    [0023]FIG. 8 schematically depicts a sequence of operation showing the relative motions of the hub and a crescent piston according to an embodiment of the present invention;  
         [0024]    [0024]FIG. 8A depicts the expansion chamber with the crescent piston at top dead center;  
         [0025]    [0025]FIG. 8B depicts the expansion chamber with the crescent piston at 90° rotation;  
         [0026]    [0026]FIG. 8C depicts the expansion chamber with the crescent piston at 180° rotation; and  
         [0027]    [0027]FIG. 8D depicts the expansion chamber with the crescent piston at 270° rotation. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0028]    Referring to FIG. 1, the positive displacement turbine (PDT)  10  generally includes housing  12 , combustion chamber  14 , compressor section  16  and expansion section  18 . The PDT  10  may be constructed from a variety of materials, including conventional steel, cast iron or aluminum, as well as ceramics and composites. Constructing the PDT  10  of aluminum, steel, cast iron or a combination of these materials offers the opportunity for the PDT  10  to be readily manufactured using presently available production facilities without the need for extensive retooling. However, non-metallic low thermal conductivity ceramics and carbon fiber composites may be preferable for construction of the PDT  10 . Ceramics and carbon composites offer the advantages of being strong, lightweight and recyclable, as well as facilitating simple and inexpensive manufacturing of the PDT  10 . A further advantage of the use of ceramics and carbon composites is that they will allow the manufacturing of a hermetically sealed engine unit. A hermetically sealed engine unit will prevent the end user from tampering with the tuning of the engine, thereby maintaining highly efficient operation.  
         [0029]    Ceramics are commercially available for many providers, such as Dow-Corning and Champion Spark Plug, Ceramic Division. Carbon fiber composites and other composites are commercially available from DuPont.  
         [0030]    Housing  12  generally includes compressor end  20 , center partition  22 , and expansion chamber end  24 . Shaft  26  passes through, and is indirectly supported by, compressor end  20 , center partition  22  and expansion chamber end  24 . Shaft  26  is preferably made of steel, iron or Kevlar carbon fiber composite. Shaft  26  is directly supported by appropriate bearings  28  and sealed by appropriate seals  30  at its passage through each of compressor end  20 , center partition  22  and expansion chamber end  24 . Shaft  26  may be splined or keyed to allow those structures mounted on it to slide longitudinally to accommodate assembly and thermal expansion. DuPont VESPEL® manufactures composite bearings and seals with adequate performance for this purpose.  
         [0031]    Compressor section  16  encloses compressor  32 . Compressor  32  is driven by shaft  26  and may be any sort of compressor known to the compressor arts. Compressor  32  is preferably a radial compressor capable of providing sufficient pressure and gas volume to charge combustion chamber  14 . Compressor  32  is preferably an axial single-direction compressor.  
         [0032]    Combustion chamber  14  generally includes combustion chamber enclosure  34 , compressor check valve  36 , fuel injector  38 , temperature sensor/glow plug  40 , coolant injector  42  and pass gate sentry valve (PGSV)  44 . Combustion chamber  14  may be designed in various shapes to meet the configuration needs of engines for different specific fuels. For example, combustion chamber  14  may be shaped differently for engines burning unleaded gasoline, propane, #2 fuel oil, natural gas or hydrogen.  
         [0033]    The combustion chamber is constructed from a material tolerant to explosive shock and conductive of thermal energy. For example, combustion chamber  14  may be constructed of carbon-carbon fiber composites or ceramic as well as cast iron, steel, aluminum or other conventional materials. Information on carbon-carbon composites is available from the National Aeronautics and Space Administration. Combustion chamber  14  may be placed in a deliberate position relative to housing  12 , so as to salvage thermal energy from the exhaust as the hot gases pass around the combustion chamber  14  exterior.  
         [0034]    Compressor reed valve  35  separates compressor  32  from compressor check valve  36 . Compressor check valve  36  includes valve body  46 , spring  48 , and washer  50 . Compressor check valve  36  allows fluid communication between compressor  32  and combustion chamber  14  when open. Compressor check valve  36  allows fluid flow from compressor  32  into combustion chamber  14  when open, while preventing backflow when closed.  
         [0035]    Fuel injector  38 , temperature sensor/glow plug  40 , and, as required for a non-diesel fuel, spark plug  41  are well-known in the internal combustion engine arts and will not be described further.  
         [0036]    Coolant injector  42  serves to inject a metered quantity of liquid coolant into combustion chamber  14 . The liquid coolant itself will be described later in this disclosure.  
         [0037]    Pass gate sentry valve (PGSV)  44  includes combustion gas passages  52 , valve body  54 , valve piston  55 , valve seat  56  and spring  58 . PGSV  44  is enclosed in PGSV chamber  60 . Combustion gas passages  52  provide fluid communication between combustion chamber  14  and PGSV chamber  60 . Valve body  54  is held firmly against valve seat  56  by spring  58 . PGSV  44 , when open, provides fluid communication between combustion chamber  14  and expansion section  18 .  
         [0038]    Expansion section  18  includes expansion chamber redirecting surface  62 , stator body  64  and exhaust port  68 . Stator body  64  along with center partition  22  and expansion chamber end  24 , define expansion chamber  70 . Center partition  22  and expansion chamber end  24  define cam tracks  72  therein. Cam tracks  72  are generally race track-shaped and eccentrically located about shaft  26 . Expansion chamber  70  is generally circular in shape, with a flattened portion at the upper edge thereof, as is readily apparent from FIG. 5. Stator body  64  further defines rotor seal cavity  74  in which rotor seal  76  is seated.  
         [0039]    Further referring to FIG. 5, oscillating piston assembly  78  is enclosed within expansion chamber  70 . Oscillating piston assembly  78  includes piston hub  80  and crescent piston  82 . Piston hub  80  is rotationally secured to shaft  26  while being free to slide longitudinally. Crescent piston  82  is seated in a saddle  84  on the outer diameter  86  of piston hub  80 .  
         [0040]    Referring particularly to FIGS. 6 and 7, crescent piston  82  generally includes piston body  88  and piston actuator arm assembly  90 . Piston actuator arm assembly  90  includes actuator arms  92 , cam arms  94  and cam followers  96 . Cam followers  96  are sized to fit closely but to travel freely within cam tracks  72 .  
         [0041]    Piston body  88  is generally crescent-shaped and defines an arcuate face  98 , leading edge  99  and a flat face  100 . Flat face  100  further defines a concave piston face contour  102 . Arcuate face  98  is sized and shaped to fit closely and movably into saddle  84 . Leading edge  99  is adapted to follow closely and scour the inner surface of stator body  64 .  
         [0042]    Referring particularly to FIG. 8, as piston hub  80  and crescent piston  82  rotate about shaft  26  within expansion chamber  70 , crescent piston  82  defines a path of travel as illustrated in sequential sub FIGS. 8A, 8B,  8 C and  8 D. As can be seen from FIG. 8, the interaction of cam follower  96  with cam tracks  72 , in combination with the interaction between piston body  88  and saddle  84 , define the motion of crescent piston  82 . This relationship maximizes surface area for gases with an expansion chamber  70  to push against.  
         [0043]    Coolant injector  42  is used to inject an injection fluid coolant into combustion chamber  14  during the combustion process. Water injection is well known in the art and has been employed in reciprocating engines since the 1930s. The term “injection fluid coolant” is intended here to mean any non-fuel fluid introduced into the positive displacement turbine  10  internal combustion engine. The injection fluid coolant is made, preferably, of water and a small amount of a chemical alkali; for example, calcium hydroxide or calcium phosphate. The concentration of the alkali component preferably corresponds to the amount of acidic combustion by products produced by the engine during the combustion process. Thus, sufficient base, such as calcium hydroxide, is mixed with the injector fluid to react with and neutralize the resulting acids formed in the combustion process. As is well known, the acid-base reaction yields water and a salt. The case of calcium hydroxide with sulfuric acid is as follows:  
         Ca(OH) 2 +H 2 SO 4           CaSO 4 .2H 2 O  
         [0044]    In operation, compressed air is taken in and compressed by compressor  32 . Compressed air is forced through compressor check valve  36  into combustion chamber  14 . When the pressure has equalized between the outside of compressor check valve  36  and the inside of combustion chamber  14 , compressor check valve  36  closes. After the closing of compressor check valve  36 , fuel injector  38  injects a metered quantity of fuel to mix with the compressed air already in combustion chamber  14 . Compression ignition then occurs to ignite the fuel-air mixture. Alternatively, a spark plug  41  may be provided to the combustion chamber to ignite the fuel-air, depending on the type of fuel used.  
         [0045]    Simultaneously with combustion, coolant injector  42  injects a charge of coolant into combustion chamber  14 . Coolant may be injected at another point in time during the combustion cycle, such as prior to the introduction of the compressed air. Coolant is converted to steam with a consequent increase in combustion chamber pressure and reduction in temperature. The gas pressure created by the combustion process forces gas into and through combustion gas passages  52  and acts on valve piston  55 . This opens PGSV  44 . Hot expanding combustion gases then cause PGSV  44  to open, allowing the hot combustion gases, along with the gaseous coolant, to leave combustion chamber  14  and expand into expansion chamber  70 .  
         [0046]    At this point in time, crescent piston  82  is located at the top dead-center position, as depicted in FIG. 8A. The hot combustion gases pass over expansion chamber redirecting surface  62  and then apply force to piston face contour  102 . The force applied causes piston hub  80  to rotate in a clockwise direction, as depicted in FIGS. 8B, 8C and  8 D.  
         [0047]    It should be noted that crescent piston  82  absorbs energy from the hot combustion gases throughout substantially its entire rotation. The location of exhaust port  68  allows the piston to receive force from the hot combustion gases throughout an effective approximate 370° of rotation. The 370° includes a 330° primary exhausting plus a secondary 40° exhausting. Exhaust gas begins to leave expansion chamber  70  at about 330° of rotation and continues for about another 40°. The expanding combustion gases are still applying force to arcuate face  98  of crescent piston  82 , while the next charge of combustion gas is beginning to apply force to piston face contour  102  during the following cycle.  
         [0048]    The crescent piston  82  employs the back pressures of the previous combustion cycle to create a sealing force between events. The action of crescent piston  82  and leading edge  99 , in addition to the aerodynamic shape of the piston, accomplishes this. The leading edge  99  of the crescent piston  82  pushes against the previous cycle of gases to exhaust them from the expansion chamber  70 . Sustained high operating temperatures within the positive displacement turbine  10  promote a complete combustion reaction leaving few particulates. Hydrocarbon fuels reacting with oxygen in the air produce large quantities of water vapor or live steam as a product of the reaction. Additional steam is generated from the coolant injected in the combustion chamber  14 .  
         [0049]    Expansion chamber  70  has a perimeter shape to accommodate the movements of the crescent piston  82 . The perimeter of the expansion chamber  70  is a circle, flattened in one aspect. This shape may be referred to as a semi-oblate circle.  
         [0050]    Expansion chamber redirecting surface  62  is shaped to direct combustion gases at piston face contour  102  and to create a turbulent, circular, centrifugal flow of combustion gases within expansion chamber  70 . Crescent piston  82  includes piston face contour  102  which tends to redirect hot exhaust gases upward and outward, creating a cyclonic gas movement along outer diameter  86  of piston hub  80 , and then in a reverse direction along the interior of expansion chamber  70 . This cyclonic movement of rotating hot gases creates an extremely turbulent gas circulation. This encourages complete oxidation of all components of the fuel. A fundamental principal of the expansion chamber  70  is that the more turbulent the gases in the expansion chamber  70 , the lower the exhaust gas temperature. The cyclonic movement of hot combustion gases also facilitates the chemical reactions between acidic components of the combustion process and the calcium hydroxide or other alkali in the injection cooling fluid, thus facilitating the pH neutralization of acid combustion products.  
         [0051]    Further, the expansion of injection fluid coolant into expansion chamber  70  tends to recover thermal energy that would otherwise be wasted through a cooling or exhaust system. Regulating of engine operating temperature may be achieved by monitoring the exhaust gas temperature and by using this data to meter the amount of injection fluid coolant injected.  
         [0052]    The PDT  10  engine is configured to take advantage of the high temperatures developed in the combustion chamber  14  to salvage excess thermal energy. Coolant introduced into combustion chamber  14  is converted into live steam, thereby transferring additional force to the drive shaft as useful work. This salvaging of excess thermal energy tends to reduce the need for external air-cooling fins or water jackets. The PDT  10  regulates its operating temperature through the use of injector fluid coolant. It is expected that, for every gallon of petroleum utilized in the PDT  10 , one to six gallons of injector fuel coolant will be used to absorb excess thermal energy. Actual usage will depend upon engine load and conditions.  
         [0053]    The present invention may be embodied in other specific forms without departing from the spirit of any of the essential attributes thereof. Therefore, the illustrated embodiments should be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention.