Abstract:
An open-cycle engine in which rotary power is produced by the pressure of hot gasses against confined, rotating vanes.

Description:
[0001]     This application is based on provisional application U.S. Ser. No. 60/841,918, filing date Sep. 5, 2006. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention is an improved internal combustion engine of the Brayton, or open cycle type. An open cycle engine may be defined as an internal combustion engine in which the compression of air and the burning of fuel when mixed with the compressed air, takes place continuously.  
         [0003]     Jet turbine engines that produce shaft power may best represent open cycle engines of the prior art. Engines of this type are called turbo-shaft engines, and are typically used to power helicopters and larger fixed-wing aircraft because they are efficient, lightweight, clean-burning, have a multi-fuel capability, and spin smoothly with no reciprocating parts.  
       BACKGROUND OF THE INVENTION  
       [0004]     The aforementioned attributes notwithstanding, the turbo-shaft engine is not generally utilized to provide power in common conveyances such as boats, motorcars and, trucks. This is largely because a turbo-shaft engine is expensive to build, as much as ten times as expensive as reciprocating engines of the same horsepower. Additionally, the turbo-shaft engine cannot change its speed of rotation very quickly. This is because the rotating components are driven at very high speeds causing a high rotational inertia. This high rotational inertia also causes a danger when failure of a rotating component occurs, because the energy that is stored in the high speed rotating parts can be very difficult to contain.  
         [0005]     A modern turbo-shaft engine is certainly smoother and lighter than today&#39;s dated reciprocating engines, and with the use of a regenerator, can be very efficient besides, however the acquisition and processing costs of the exotic materials needed in the turbine section push the cost of the turbo-shaft engine well out of reach for most applications. The use of a regenerator adds even more bulk and cost to the system.  
         [0006]     In a turbo-shaft engine, the hot gasses of combustion are required to enter the turbine power section at near-sonic speeds. These near-sonic gas speeds are required to produce meaningful power. Unfortunately, the high velocity of the hot gasses causes a major energy loss due to friction and turbulence, with the parasitic friction loss increasing generally as the square of the velocity.  
         [0007]     The aforementioned near-sonic gas speeds are required because the gasses must impinge the initial rows of turbine blades at very high velocities to provide a meaningful kinetic energy force to the blades. Subsequent rows of blades produce power using a reaction force that can be compared to the lift produced by air flowing over an aircraft wing. These rows of blades also require a high velocity in the hot gasses. Both the impingement forces and the reaction forces increase greatly with an increase in the speed of the hot gasses. For this reason, turbine engines are designed to use as high a gas velocity as possible—just below the velocity that would cause detrimental sonic shock waves to form. Again, there is a substantial energy loss due to the turbulence and parasitic drag caused by these high gas speeds.  
         [0008]     Also in the turbine type of power section, the tremendous turbulence caused by the high gas speeds and the vectoring of hot gasses from blade to blade, causes a substantial transfer of heat to the power section components, requiring that they be fabricated from exotic, high temperature materials in order to have adequate strength.  
         [0009]     In contrast, the present invention, an improved open cycle internal combustion engine, does not utilize a turbine power section. The present invention instead uses the pressure of hot gasses against confined, rotating vanes to produce power, and therefore does not require the ultra-high gas velocities that are needed in a turbine. The lower speed of hot gasses in the power section of the present invention, provides a huge reduction in parasitic drag when compared to a turbo-shaft engine, resulting in a greater economy of operation. The reduced speeds of the hot gasses, and the absence of blade-to-blade vectoring provides a reduction in turbulence that also reduces heat transfer from the hot gasses to the metal parts of the power section, providing a greatly reduced requirement for exotic high temperature materials.  
         [0010]     A reduced speed of hot gasses is made possible in the present invention by the use of a unique and efficient counter-rotating rotor system to extract power, rather than the turbine found in a turbo-shaft engine. This dual rotor system provides a substantially positive containment of the hot gasses of combustion during the power-producing portion of a cycle. In comparison, the gasses flow relatively freely through the blades of a turbine type of power section, losing useful energy in turbulence and drag as they are vectored from blade to blade. Rotational power in the present invention is produced mainly by the pressure of hot gasses against the surfaces of confined rotating vanes, rather than by the kinetic and reactive forces utilized in a turbine. This eliminates the need for ultra-high gas velocities with the resultant high amounts of energy loss and heat transfer.  
         [0011]     The present invention utilizes the hot, pressurized gasses of combustion, produced by any of a multitude of different fuels, to apply a pressure force to the surfaces of vane protrusions on counter-rotating rotors that rotate within a closely confining encasement. The surfaces of the vanes opposite to the surfaces on which the pressure force is applied are in gaseous communication with the atmosphere via an exhaust port, and the resultant pressure differential provides the force to turn the rotors.  
         [0012]     The hot gasses change direction smoothly and infrequently in the power section of the present invention, as opposed to the significant number of vector changes found in a turbine power section. This ease of gas movement provides a reduced amount of drag and turbulence and helps to provide a dramatic increase in efficiency over the turbo-shaft engine.  
         [0013]     As previously mentioned, the turbo-shaft engine is available only at a very high cost, which limits its use to military and commercial aircraft, military conveyances such as tanks and ships, and large electrical power plants, where the costs of acquisition and the provision of regeneration is not so much at issue. In addition to the high cost of the exotic materials required in the turbo-shaft engine, additional costs are incurred due to the turbo-shaft engine&#39;s high rotational speeds, which require special bearings and lubrication systems, with no tolerance for error in manufacturing.  
         [0014]     In contrast, the power section of the present invention has relatively low rotational speeds, reducing the requirement for special bearings and lubrication systems. Additionally, the low rotational inertia present at low speeds of rotation allows speed changes to be effected much more easily and quickly when compared to the turbo-shaft engine. As in a turbo-shaft engine, speed changes in the present invention are accomplished by reducing the amount of fuel metered to the engine. When extremely rapid changes in rotational speed are required, additional throttling of the intake air may be effected.  
         [0015]     The present invention is simple in structure, with little requirement for exotic metals. These traits help make it considerably less expensive to manufacture than a turbine engine, and because it has few moving parts, it can also be significantly less expensive to manufacture than a reciprocating engine. This low cost of manufacture along with an unprecedented efficiency that is inherent in the design, allows an opportunity for wide-spread use in automobiles (especially the hybrid type of automobile), boats, trains, airplanes, electrical generators, and other usages in which a simple, low cost, highly efficient, clean burning, multi-fuel engine can be of service.  
       SUMMARY OF THE INVENTION  
       [0016]     A primary object of the present invention is to provide an open cycle internal combustion engine with an increased fuel efficiency over open cycle engines of the prior art, reducing emissions and lowering operating costs.  
         [0017]     Another object of the present invention is to provide an open cycle internal combustion engine that is less complex in fabrication than open cycle engines of the prior art, easing manufacture, and lowering acquisition costs.  
         [0018]     An additional object of the present invention is to provide an open-cycle internal combustion engine in which heat transfer to the power section components is less than open cycle engines of the prior art, reducing the need for exotic, heat resistant metals, and their attendant manufacturing complexity and cost.  
         [0019]     Another object of the present invention is to provide an open-cycle internal combustion engine for general use that can run cleanly, efficiently and safely on a wide range of different fuels.  
         [0020]     These, and other objectives are achieved in the present invention, which extracts power from the pressure of hot gasses of combustion. The pressure of hot gasses is applied to the surfaces of vanes that are integral with, or rigidly coupled to counter-rotating rotors, rotating within a closely confining encasement. The use of confined rotating vanes to provide power allows a substantial reduction in the speed of the hot gasses relative to the metal parts of the power section when compared to a turbine power section. This reduction in speed greatly reduces drag, a product of the square of the speed, which substantially increases efficiency. Slower gas speeds also result less heat transfer to the metal parts of the power section, which is represented by a lower film co-efficient in the heat transfer equation. This equation shows that lowering the speed of the hot gasses results in a substantial reduction of the amount of heat transferred into adjacent parts. Lowering the amount of heat transfer, reduces or eliminates the need for exotic heat-resistant metals and their attendant manufacturing costs.  
         [0021]     Additional cooling of the components in the power section of the present invention, takes place due to the expansion and resultant cooling of the hot gasses during the part of the cycle that the gasses are released through the exhaust port into the atmosphere. The portions of the vanes and rotors that are in gaseous communication with these expanding gasses are provided cooling by the expanding gasses. In comparison, the turbine parts in a turbo-shaft engine are continuously exposed to high-speed hot gasses, and there is little cooling of the turbine components that can be attributed to expanding gasses.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]      FIGS. 1 and 1 A show cross-sections of an embodiment of an open cycle internal combustion engine of the present invention. A gear-driven centrifugal air compressor  1  provides compressed air through a compressed air duct  2  to a plenum  4  for admittance through a burner liner  9  in which the compressed air is mixed with fuel and ignited so that combustion takes place. A centrifugal air compressor is used in this embodiment because of its high efficiency, however other types of air compressors, including an embodiment of the mechanism that extracts power from the burning gasses of the present invention, could be used as well. After ignition of the compressed air and fuel, resulting hot gasses of combustion provide pressure to integral hollow vanes  19  of dual counter-rotating rotors  13  with integral vane follower cavities  16  that counter-rotate at a 1:1 ratio within a rotor encasement  3 . 
     
    
       [0023]     The compressor  1  also provides cooling bleed air to the hollow rotor shafts  21  by way of the rotor shaft ducts  34  to cool the rotors and vanes. The rotor gears  28  ensure that both rotors counter-rotate at the same speed, so that the tips and adjacent surfaces of the hollow vanes  19  can follow the contours of the surfaces of the vane follower cavities  16  with substantial precision. The closeness of surfaces of the hollow vanes  19  to the surfaces of the vane follower cavities  16 , prevents any substantial leakage of combustion gasses between said surfaces, during the portion of the cycle that the surfaces of the hollow vanes follow the surfaces of the vane follower cavities. During the remainder of the cycle, combustion gasses are substantially prevented from escaping between the rotors  13  by the closeness of the surfaces of the outside diameters of the rotors. Leakage between the sides of the rotors  31 , and the inner surfaces of the sides of the rotor encasement  3  is also substantially prevented by the closeness of said surfaces. Leakage of hot gasses between the tips of the hollow vanes  19  and the inside contours  9  of the rotor encasement  3  is substantially prevented by the closeness of their surfaces. Labyrinth or other types of seals may augment some of the areas of closeness in which leakage of hot gasses might occur. Power may be taken from drive gears  29  that are connected to the rotor shaft  21 .  
         [0024]      FIG. 2  shows a cross section of another embodiment of the present invention having counter-rotating rotors  13  and  11 . There are two solid rotor vanes  12  fixedly attached to rotor  13 . The vane follower rotor  11  contains the vane follower cavity  16  and is geared to rotor  13  in a 2:1 ratio, which drives the vane follower rotor  11  at twice the speed of rotor  13 . Hot gasses of combustion are substantially prevented from leaking between the vane follower rotor  11  and the vane follower rotor case contour  22  by a closeness in tolerance between the two. Again, labyrinth or other types of seals may augment some areas of closeness in which leakage of hot gasses might occur. There is one vane follower cavity in this embodiment, however other embodiments could provide a vane follower rotor having two or more vane follower cavities and be driven at speeds other than 2:1 to allow the vane follower cavities to follow in concert with the rotor vane or vanes. The rotor vanes  12  are not hollowed for cooling in this embodiment, but are instead cooled by conduction into the material of the rotor  13 . The material of the rotor is in turn cooled by providing the rotor cavities  10  with a cooling fluid that may be liquid or gas, through a cooling duct  15  in the side case. The vane follower rotor  11  may also be hollowed for cooling.  
         [0025]      FIG. 3  shows a cross section of another embodiment of the present invention, the dual rotors  13 , having integral vane follower cavities  16 . As in  FIG. 2 , the rotor vanes  12  are not hollowed for cooling, but are instead cooled by conduction into the material of the rotors  13  and by the expansion of hot gasses at the low-pressure side of the vanes. The rotors  13  are hollowed so that cooling fluid introduced through cooling ducts  15  at the side of the engine casings may pass through the rotor cavities  10 .  
         [0026]     In this embodiment, compressed air for combustion is provided by a turbocharger  37  powered by residual hot gasses from the exhaust duct  14 . The turbocharger in this embodiment is of the radial inflow type with a centrifugal compressor, however other types of turbochargers or compressors may be used as well.  
       DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0027]      FIGS. 1 and 1 A show cross-sections of the preferred embodiment of an open cycle internal combustion engine of the present invention. The  FIG. 1  section is taken on a line through the mid-point of the rotors  13 , combustion chamber liner  9 , and plenum  4 . The rotor shaft plugs  23 , shown in  FIG. 1A , are not depicted in this view. The  FIG. 1A  section is taken on a line taken longitudinally through the centers of the hollow rotor shafts.  
         [0028]     In operation;  
         [0029]     A centrifugal compressor  1 , driven by a drive gear  29  on one of the rotor shafts  21 , forces compressed air through a compressed air duct  2  and into a plenum  4 . The plenum  4  transfers the compressed air to a burner shroud  8 , which conducts the compressed air to a swirler  7 , and a burner liner  9 . Fuel is introduced into the combustion area by a fuel-metering nozzle  6 , which is fed by a fuel-metering pump, which is of conventional design and not shown. The swirler creates turbulence to mix the compressed air homogeneously with the fuel, which may be a liquid, solid particulate, or gas.  
         [0030]     The fuel-air mixture is ignited inside the burner liner by an igniter  5  and is further mixed with the compressed air entering the burner liner through air metering holes  30 . The resulting expanding hot gasses of combustion provides pressure to the hollow vanes  19  which are integral with the rotors  13 , that turn counter-rotationally at a speed that even under load is fast enough to allow enough of the pressure of combustion inside the burner liner to be released to ensure that the pressure inside the burner liner is always slightly lower than the pressure of the compressed air outside the liner, so that burning gasses do not bleed back through the metering holes  30 .  
         [0031]     The rotors  13 , which are identical in diameter in this embodiment, turn counter-rotationally in a precise 1:1 ration due to a pair of rotor gears  28  which are fixedly connected to rotor shafts  21 . The rotors turn in the directions shown by the arrows around the rotor peripheries in  FIG. 1  that depict burning gasses. The pressurized hot gasses are substantially prevented from leaking between vanes  19  and the vane follower cavities by the closeness of the surfaces of the vanes  19  to the surfaces of the vane follower cavities  16  during the portion of rotation in which they are in proximity. Vane and vane follower cavity shapes other than those shown may also be useful, as long as the surfaces of the vanes and vane follower cavities remain in close proximity during the part of the cycle that the vane sweeps through the vane follower cavity. The gasses are substantially prevented from leaking between the rotors by the closeness of the outside diameters of the rotors  13  at all other times during the cycle.  
         [0032]     Pressurized hot gasses are substantially prevented from leaking between the tips of the vanes  19 , and the internal engine case contours  35  by the closeness between said parts. Pressurized hot gasses are also substantially prevented from leaking between the sides of the rotors  31  and the inner sides of the engine cases  3  by a closeness between said parts. The surfaces of the sides of the rotors  31  and the sides of the engine case sides  3  are depicted as flat in this embodiment for ease of fabrication, however to provide a lighter weight, said rotor and engine case sides could also be convex and concave respectively, or vice-versa, so that the engine case sides could providing a higher strength to resist the pressure of the hot gasses, while weighing less. Labyrinth or other types of seals may be used in any or all of the areas of close proximity to provide additional sealing of leakage of the combustion gasses.  
         [0033]     The rotor shafts  21  are supported by rotor shaft bearings  26 , which are ball bearings in this embodiment, however the bearings could also be of the plain or roller type. Oil for lubrication is pumped to the bearings through oil feed tubes  24  by an oil pump of conventional design that is not shown. The oil flows to, or is sprayed on the rotational parts of the bearing, and is contained within the bearing housing  36  by bearing seals  27 . Pressure from the compressor bleed air may be applied to the cavity between the innermost of the bearing seals  27  and the engine cases  3 , through seal cavity ports  36  to prevent hot gasses from leaking through to the seals. Excess oil is returned by way of the oil return tubes  25  to an oil cooler and sump of conventional design, which are not shown.  
         [0034]     The rotors  13 , rotor shafts  21 , rotor vanes  19 , and vane follower cavities  16 , are cooled by compressor bleed air that is introduced to the hollow rotor shafts  21  through the bleed air intake ports  34 . Other pumping means and other fluids may be used for cooling as well, such as water cooling, The hollow rotor shafts have rotor shaft plugs  23  at their middle, to force air through a plurality of rotor shaft ducting holes  18  on the air entrance side of the rotor shaft plug for the purpose of cooling the internal walls of the rotors, vanes, and vane follower cavities. The air absorbs heat from the rotors, vanes, and vane follower cavities, and then exits through rotor shaft ducting holes  18  on the air exit side of the rotor shaft plug  23 .  
         [0035]     Compressor bleed air is piped to the bleed air intake ports  34  from the bleed air exit tubes  33  that are in gaseous communication with the plenum  4  by air duct piping that is not shown. The rotor vanes  19  have rotor vane bleed holes  17  to help cool the tips of the vanes, and the engine case contours  35 . The cooling requirements may be reduced with the use of insulating ceramic or other high temperature coatings in the areas that are exposed to hot gasses.  
         [0036]     Rotational power may be taken from the engine using one or both of the drive gears  29 . Said rotational power may alternately be taken from one or both of the enmeshed rotor gears  28  as could power be taken to drive the compressor, in which case one or both of the drive gears  29  could be eliminated.