Abstract:
An internal combustion engine is provided. The engine comprises at least one combustion chamber. The engine is suitable for various types of fuel. The engine, depending on fuel type, may have at least one spark plug. The engine uses an external source of compressed oxidant, such as air, which is delivered from a compressor and/or pressurized storage tank. Compressed oxidant, such as air, is delivered directly into the combustion chamber. Fuel is delivered directly into the combustion chamber. Oxidant and fuel mixture is ignited either by means of a spark plug, laser ignition, or by other means, or ignites spontaneously, depending on fuel type and pressure in the combustion chamber. The engine may comprise at least one cylinder, or may be of rotary or other type. A hybrid vehicle based on such an engine is provided. An automatic parking system for such a vehicle is provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit under 35 USC §119(e) of U.S. Provisional Application No. 61/511,571 filed Jul. 26, 2011 and titled “Internal combustion engine with direct air injection and hybrid vehicle based thereupon”; U.S. Provisional Application No. 61/483,915 filed May 9, 2011 and titled “Internal combustion engine with direct injection of air and fuel”; U.S. Provisional Application No. 61/483,952 filed May 9, 2011 and titled “Rotary internal combustion engine”; and U.S. Provisional Application No. 61/381,948 filed Sep. 11, 2010 and titled “Mechanism of the gas distribution of internal combustion engine.” 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention pertains to the field of internal combustion engines. Presently, the internal combustion engines being manufactured generally suffer from a plethora of problems, such as excessive weight and size, low efficiency, low power-to-weight ratio, low torque, high fuel consumption, high levels of air pollution, excessive noise and vibration, high complexity and large number of parts, which leads to decreased reliability and durability of the engine. The present invention endeavors to solve these problems to some extent, improving the relevant parameters substantially. 
       US PATENT REFERENCES 
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         U.S. Pat. No. 4,478,304, Compressed air power engine, Delano, 1984 
         U.S. Pat. No. 4,596,119, Compressed air propulion system for a vehicle, Johnson, 1986 
         U.S. Pat. No. 4,741,164, Combustion engine having fuel cut-off at idle speed and compressed air starting and method of operation, Slaughter, 1988 
         U.S. Pat. No. 4,776,306, Valve operating system for internal combustion engine, Matsuura et al., 1988 
         U.S. Pat. No. 4,782,801, Internal combustion motor, Ficht et al., 1988 
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         U.S. Pat. No. 4,989,558, Spherical rotary valve assembly for an internal combustion engine, Coates, 1991 
         U.S. Pat. No. 5,230,314, 4-Cycle engine, Kawahara et al., 1993 
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         U.S. Pat. No. 5,460,239, Air compressor based vehicle drive system, Jensen, 1995 
         U.S. Pat. No. 5,535,715, Geared reciprocating piston engine with spherical rotary valve, Mouton, 1996 
         U.S. Pat. No. 6,363,723, Method and device for reaccelerating a vehicle equipped with high-pressure air compressors, Negre et al., 2002 
         U.S. Pat. No. 6,752,131, Electronically-controlled late cycle air injection to achieve simultaneous reduction of NOx and particulates emissions from a diesel engine, Poola et al., 2004 
         U.S. Pat. No. 6,962,137, Two-cycle rotary engines, Udy, 2005 
         U.S. Pat. No. 7,121,247, Spherical rotary engine valve assembly, Lee, 2006 
         U.S. Pat. No. 7,328,680, Cylinder head assembly and spherical valve for internal combustion engines, Diamond, 2008 
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         U.S. Pat. No. 7,802,550, Cylinder head arrangement including a rotary valve, Dirker, 2010 
       
     
       US PATENT APPLICATION REFERENCES 
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         20080314342, Desmodromic variable valve actuation, Pattakos et al., 2008 
         20100000491, Rotary engines, systems and methods, Tinder, 2010 
       
     
       FOREIGN PATENT REFERENCES 
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         WO/2003/058045, Two-process rotary internal combustion engine, Krajnovic, 2003 
         WO/2005/124105, Rotary machine and internal combustion engine, Olofsson, 2005 
       
     
       OTHER PUBLICATIONS 
       [0000]    
       
         Grünefeld, G., Knapp, M., Beushausen, V., and Andresen, P., “Direct Air Injection for Substantial Improvement of SI Engine Cold Start Performance,” SAE paper 971069, 1997 
         Siuru, W. D., Jr. “Automotive Superchargers and Turbochargers,” Handbook of Turbomachinery, 2003 (2nd ed) 
         Siuru, W. D., Jr. “Why We Want to Plug In Our Cars,” www.GreenCar.com, 2007 
         Müller, B., Deutscher, J., Grodde, S., Giesen, F., and Roppenecker, G., “Universal Trajectory Planning for Automatic Parking,” ATZ Worldwide eMagazines, 2007 
         Mickelson, P., “Why 2-Stroke Direct Injection is a Big Deal,” Snow Goer, October 2008 “Clean, economical engines to cut greenhouse gas emissions,” PSA Peugeot Citroën, 2011 
       
     
       BRIEF SUMMARY OF THE INVENTION 
       [0037]    The principal objects of the present invention are: to provide an improved internal combustion engine; to also provide an engine of greatly improved efficiency, higher output power to weight ratio, and improved torque capabilities; to also provide such an engine, which utilizes an external air compressor and/or compressed air reservoir to inject compressed air directly into the combustion cavity, obviating the need for intake valves; to also provide such an engine, which utilizes spherical pivoting intake and/or exhaust valves; to also provide an engine which avoids the reciprocation of relatively large masses therein, thereby avoiding the conversion of the linear movement to rotary movement with the goal of improving fuel efficiency and reducing vibrations; to also provide such an engine with fewer parts and without the need for complex types of valve mechanisms, which are required in conventional reciprocating engines; to also provide a rotary engine including a lobed rotor or a rotor with retracting vanes; to also provide a rotary engine with a pluraliry of rotors; to also provide an engine, which can be powered both by fuel and compressed air; to also provide a hybrid vehicle, which can be operated using fuel, electricity, and compressed air; to also provide a hybrid vehicle with electric motor in each wheel, which would enable greater maneuverability and would decrease size and weight of the vehicle; and to also provide an automatic parking system for such a hybrid vehicle. 
         [0038]    According to an aspect of the invention, this objective is met by the valves being of a rotary type, having a rotation body, such as a sphere, for example. The spherical valves pivot around their axes and thus control the opening and the closing of the intake and exhaust channels. The camshafts forcibly close the valves without requiring springs. This has the effect of making the engine lighter and more durable, reducing its weight and fuel consumption and eliminating improper untimely spontaneous ignition, thus resulting in overall improved power and performance. 
         [0039]    According to another aspect of the invention, this objective is met by converting a traditional 4-stroke piston engine into an effectively 2-stroke engine by adding a source of compressed air. Compressed air is delivered from a compressor or a storage tank directly into the combustion chamber and fuel is injected directly into the combustion chamber by fuel injector, thereby eliminating the intake and compression strokes of a traditional 4-stroke engine, leaving only the power and exhaust strokes. Therefore, such a 2-stroke engine would only require exhaust valves, since the need for intake valves would be obviated by direct air injection. 
         [0040]    According to another aspect of the invention, this objective is met by the engine being of a rotary type, having a rotation body, such as a cylinder, for example. The rotor of the engine can have at least two vanes. One preferred embodiment, which is illustrated in  FIG. 9 , comprises two combustion chambers and four vanes. The vanes may be moving radially from within the rotor body, or may be tilted at an angle different from 90°, and their axes do not necessarily have to go through the center of the rotor. 
         [0041]    Each pair of vanes and the stator define a rotary combustion chamber and an exhaust chamber. This engine needs no intake or exhaust valves, nor does it need an intake manifold. This engine uses compressed fuel-air mixture (or some other fuel-oxidant mixture), which gets created by having the fuel and compressed air (or another oxidant) delivered separately prior to ignition by their respective injectors into the combustion chamber, where fuel and oxidant (such as air) get mixed immediately prior to combustion. 
         [0042]    This has the effect of making the engine smaller, lighter and more durable; reducing fuel consumption; eliminating improper, spontaneous, and untimely ignition; increasing engine torque, speed, and power; decreasing vibration and noise; all of which leads to overall improved performance and increased expected mean time between failures (MTBF). 
         [0043]    According to another aspect of the invention, this objective is met by utlizing a Roots-type (also referred to as rotary tooth) supercharging compressor configuration for a rotary internal combustion engine, whereby the lobes (vanes) of the rotor would not be touching the walls of the engine stator (body) when rotating. The lobes could be of various geometric shapes for increased efficiency. There could be a plurality of rotors within a single stator (engine body). 
         [0044]    According to another aspect of the invention, this objective is met by combining the internal combustion engine with electric drive and pneumatic drive in a hybrid vehicle, capable of running on fuel, electricity, or compressed air. 
         [0045]    According to another aspect of the invention, this objective is met by the hybrid vehicle having a separate electric motor for each wheel, enabling the vehicle to turn each of the wheels up to 90 degrees in either direction, allowing for greater maneuvaribility and substantially decreased size and weight due to the resultant absence of transmission, drive shafts, and other standard equipment, which exists in traditional vehicles. 
         [0046]    According to another aspect of the invention, this objective is met by providing an automatic parking system for such a hybrid vehicle, whereby the vehicle&#39;s onboard computer program and ancillary equipment, such as video, infrared, utlrasound, radar, or other distance-measuring sensors would guide the vehicle into a parking space with minimal or no operator input. 
         [0047]    Further objects of the invention will be brought out in the following part of the specification, wherein detailed description is for the purpose of fully disclosing the invention without placing limitations thereon. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0048]    The invention is explained in more detail with reference to the drawings. 
           [0049]      FIG. 1  is a cross-sectional schematic view of an embodiment of the invention, showing the variable pivoting valve mechanism in accordance with one embodiment of the present invention during the intake stroke; 
           [0050]      FIG. 2  is a cross-sectional schematic view of an embodiment of the invention, showing the compression stroke; 
           [0051]      FIG. 3  is a cross-sectional schematic view of an embodiment of the invention, showing the power stroke; 
           [0052]      FIG. 4  is a cross-sectional schematic view of an embodiment of the invention, showing the exhaust stroke; 
           [0053]      FIG. 5  is a cross-sectional schematic view of an embodiment of the invention, showing the converted 2-stroke internal combustion engine with poppet valves; 
           [0054]      FIG. 6  is a cross-sectional schematic view of an embodiment of the invention, showing the converted 2-stroke internal combustion engine with spherical valves; 
           [0055]      FIG. 7  is a cross-sectional schematic view of the rotary engine mechanism with appurtenant apparatus according to one embodiment of the invention; 
           [0056]      FIG. 8  is a cross-sectional schematic view of another embodiment of the rotary engine with two rotors, each having two lobes; 
           [0057]      FIG. 9  is a cross-sectional schematic view of another embodiment of the rotary engine with three rotors, each having four lobes; 
           [0058]      FIG. 10  is a cross-sectional schematic view of another embodiment of the rotary engine with one rotor with four lobes; 
           [0059]      FIG. 11  is a cross-sectional schematic view of another embodiment of the rotary engine with two rotors, each having five lobes. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0060]    Referring to the drawings, particularly to  FIG. 1 , which shows a valve, mechanism for a machine such as an internal combustion engine, which requires distribution of gases, a variable pivoting valve mechanism can be seen, wherein valve opening and closing can be achieved by pivoting it by means of a rocker arm and plunger. Gas distribution timing and phases are regulated by moving the axis of the rocker arm.  FIG. 1  shows the fuel-air mixture intake stroke, the engine crankshaft (not shown), which, while turning, moves piston  100  down along the axis of cylinder  110 , creating low pressure in cavity bore  210  within cylinder  110 . Cam  120  of the left distribution camshaft by means of plunger  150  and rocking lever  190  turns intake spherical valve  160  with its intake valve cavity  200  counter-clockwise and opens gas mixture access through intake pipe  170 . Thus, gas mixture from intake pipe  170  enters cavity bore  210  of cylinder  110 . At the end of the intake stroke of the cycle, cam  120  of the left distribution camshaft by means of plunger  150  and rocking lever  190  turns spherical valve  160  with its valve intake cavity  200  clockwise and closes gas mixture access through intake pipe  170 . At the same time, right distribution camshaft is also turning counterclockwise, turning cam  121  with it. However, since the round part of cam  121  moves along the plunger  151 , the latter is stationary during the intake stroke of the cycle along with rocking lever  191 . Spherical exhaust valve  161  remains closed and stationary throughout the intake stroke of the engine cycle. Profile of cam  141  moves plunger  150  and turns rocking lever  190  around its axis  130 . Spherical valve  160  turns inside lower compression O-ring seals  180  and upper compression O-ring seals  181  into the open position. Geometric movement of axis  130  of rocking lever  190  changes phases of intake gas distribution during operation of the engine. 
         [0061]    Referring to  FIG. 2 , which shows the gas mixture compression stroke, the engine&#39;s crankshaft (not shown), while turning, moves piston  100  up along the axis of cylinder  110 , creating pressure in cavity  210  of cylinder  110 . Intake spherical valve  160  and exhaust spherical valve  161  remain stationary and closed during the compression stroke. Intake pipe  170  and exhaust pipe  171  remain closed. Piston  100  moves up along the axis of the cylinder  110 , compressing the gas mixture in cavity  210  of cylinder  110 . Gas pressure pushes lower compression O-ring seals  180  towards spherical valves  160  and  161 . Valves  160  and  161  are pushed into the saddle inside the body of the engine head (not shown). 
         [0062]    Referring to  FIG. 3 , which shows the power stroke, valves  160  and  161  are stationary and closed during the stroke. Intake pipe  170  and exhaust pipe  171  are closed. Compressed gas mixture in cylinder cavity  210  explodes. Explosion energy is converted into the downward movement of piston  100 . 
         [0063]    Referring to  FIG. 4 , which shows the exhaust stroke, piston  100  moves upward along the axis of cylinder  110 . Cam  140  of the left distribution camshaft turns valve  161  with its exhaust valve cavity  201  clockwise by means of plunger  151  and rocking lever  191 , opening exhaust pipe  171 . Exhaust gases exit from cylinder cavity  210  into exhaust pipe  171 . At the end of the exhaust stroke, cam  121  of right distribution camshaft by means of plunger  151  and rocking lever  191  turns valve  161  with its exhaust valve cavity  201  counterclockwise and closes gas exhaust from cylinder cavity  210  through exhaust pipe  171 . Geometric movement of axis  131  of rocking lever  191  changes phases of exhaust gas distribution during operation of the engine. 
         [0064]    Referring to  FIGS. 1-4 , the axes of rotation  130  and  131  of rocking levers  190  and  191  can be moved left, right, up or down to change the timing of the opening and the closing of the valves. For example, if axis  130  is moved to the left, then the timing of the opening and the closing of intake valve  160  is advanced. If axis  130  is moved to the right, then the timing of the opening and the closing of intake valve  160  is retarded. If axis  130  is moved up, then the angle of the opening and the closing of intake valve is decreased. If axis  130  is moved down, then the angle of the opening and the closing of intake valve is increased. 
         [0065]    Referring to  FIG. 5 , which shows a conventional 4-stroke internal combustion engine converted into a 2-stroke one, it can be see that this engine has no intake valve or intake manifold. The compression of gas and fuel mixture is accomplished outside the engine by means of fuel pump  330  and air compressor  320 , which inject fuel and compressed air into the combustion chamber, forming a compressed fuel-air mixture immediately prior to combustion.  FIG. 5  shows cross-section of the converted 2-stroke internal combustion engine, consisting of engine cylinder body  110 , crankshaft  220 , piston  100 , poppet valve  162 , cam  142 , and valve spring  240 , where crankshaft  231  moves within engine body  110  clockwise (in this embodiment). Fuel is delivered from fuel pump  330  through fuel line  310  and fuel injection control valve  270  into combustion chamber  210  via fuel injector  250 . Air is delivered from air compressor  320  through compressed air line  300  and air injection control valve  280  into combustion chamber  210  via compressed air injector  260 . Fuel-air mixture is ignited by spark plug  290  and is combusted in chamber  210 , after which exhaust gases are forced out of the engine through exhaust valve  162  and via exhaust manifold  171 . Changes in amounts and pressure of fuel and air (or any other oxidant), which are injected into combustion chamber  210 , are accomplished by electronic control unit  340 , which controls all modules with electrical interfaces and which may be implemented as fuel injection controller, or which may be an integral part of an onboard computer responsible for overall control of the engine or the system. 
       Power Stroke 
       [0066]    When piston  100  is at the upper dead center position inside cylinder  110 , exhaust valve  162  is fully closed, and air/oxidant is injected under pressure via air injection control valve  280  and air injector  260  into the combustion chamber  210 . At about the same time, fuel is injected through fuel injection control valve  270  and fuel injector  250  into the combustion chamber  210 . This creates a compressed fuel-air mixture in the combustion chamber  210 . This mixture is then ignited, either by means of spark plug  290  (in case of gasoline engines, for example), or by the pressure itself (in case of Diesel engines, for example). The force of the explosion makes piston  100  move downwards, which makes piston rod  230  go down as well, thereby turning crankshaft  231 , thus translating linear motion of piston  100  into rotational motion of crankshaft  231 . 
       Exhaust Stroke 
       [0067]    After piston  100  reaches bottom dead center inside cylinder  110 , exhaust valve  162  is opened, piston  100  begins to move upward, forcing the exhaust gases out of cylinder  110  through exhaust valve  162  and exhaust manifold  171 . This process continues until piston  100  reaches top dead center and exhaust valve  162  is closed, thereby finishing exhaust stroke and starting power stroke. 
         [0068]    Referring to  FIG. 6 , which shows cross-section of the converted 2-stroke internal combustion engine with spherical valves, this embodiment is essentially similar to the one shown in  FIG. 5 , except that instead of poppet valve  162  this embodiment has spherical valve  161 ; instead of cam  142  this embodiment has a different cam  143 ; and instead of spring  240  this embodiment has plunger  152 , connecting spherical valve  161  with cam  143 . 
         [0069]    Referring to  FIG. 7 , which shows a rotary internal combustion engine, it can be seen that the engine has no intake or exhaust valves. The compression of gas and fuel mixture is accomplished outside the engine by means of fuel pump  330  and air (or another oxidant) compressor  320 , which separately inject compressed fuel and air (or some other oxidant) into combustion chamber(s)  211  and/or  212 .  FIG. 7  shows cross-section of the rotary internal combustion engine with, appurtenant apparatus, where rotor  350  consists of a rotation body, such as, for example, a cylinder, which has, in this particular embodiment, four radially moving vanes  360 . In this particular embodiment, rotor  350  moves within engine body  400  (stator) clockwise. Fuel is delivered through line(s)  310  and into combustion chamber(s)  211  and/or  212  through fuel injection control valve(s)  270  and/or  271  and via fuel injector(s)  250  and/or  251 . Air (or another oxidant) is delivered through line(s)  300  and into combustion chamber(s)  211  and/or  212  through air injection control valve(s)  280  and/or  281  via air injector(s)  260  and/or  261 . Fuel-air mixture is ignited by spark plug(s)  290  and/or  291  and is combusted in combustion chamber(s)  211  and/or  212 . After fuel-air mixture is combusted, exhaust gases are forced out of the engine via exhaust duct(s)  171  and/or.  173 . Electric motor  380  serves as starter motor as well as generator, and may serve as compressor motor for fuel and/or air (or another oxidant). Rotor vanes  360  radially move in and out of rotor  350  depending on their position in engine body  400 . Vanes  360  may be pushed out of rotor  350  by means of springs or compressed air, or by some other means so as to seal against engine body  400  at low rotational speed. As the RPM increases, the centrifugal forces will force the vanes out. Changes in amounts and pressure of fuel and air, which are injected into combustion chamber(s)  211  and/or  212 , are accomplished by electronic control unit  340 , which may be implemented as fuel injection controller or may be an integral part of an onboard computer responsible for overall control of the system. Present invention may have different embodiments employing at least one combustion chamber with at least two vanes. 
       Start-Up and Idling Mode of Operation 
       [0070]    Battery  370  supplies electrical current to electrical motor  380 , which turns rotor  350 , air compressor  320 , and fuel pump  330 . Air or another gaseous oxidant necessary for combustion is delivered from air compressor  320  via compressed oxidant line  300  through air injection control valve  280  into injector  260 , which delivers it into combustion chamber  211 . Fuel is delivered from fuel pump  330  via fuel line  310  through fuel injection control valve  270  into fuel injector  250  and injected into combustion chamber  211 . Ignition is accomplished by means of spark plug  290  in case of fuels requiring means of ignition, or by self-combustion due to Diesel effect. During the idling mode it is possible to only use one spark plug  290 , one fuel injector  250 , and one air injector  260 . The periodicity of activation of spark plug  290 , fuel injection control valve  270 , air injection control valve  280 , fuel injector  250 , and air injector  260  is once per 180° turn of rotor  350 . 
       Operation Under Low Load at Low RPM 
       [0071]    Rotor  350  or electric motor  380  turns air compressor  320  and fuel pump  330 . Compressed air (or some other gaseous oxidant) is delivered via compressed air lines  300 , air injection control valves  280  and  281 , and through air injectors  260  and  261  into combustion chambers  211  and  212 . Fuel is delivered via fuel lines  310 , through fuel injection control valves  270  and  271 , and through fuel injectors  250  and  251  into combustion chambers  211  and  212 . Ignition is accomplished by spark plugs  290  and  291 . During low load operation spark plugs  290  and  291 , fuel injection control valves  270  and  271 , air injection control valves  280  and  281 , fuel injectors  250  and  251 , and air injectors  260  and  261  are operated periodically, once per 180° turn of rotor  350 . 
       Operation Under Full Load at High RPM 
       [0072]    This is similar to operation under low load at low RPM, except that during full load operation spark plugs  290  and  291 , fuel injection control valves  270  and  271 , air injection control valves  280  and  281 , fuel injectors  250  and  251 , and air injectors  260  and  261  are operated twice as frequently, once per 90° turn of rotor  350 . 
         [0073]    Reference is made to  FIG. 8 , which shows another embodiment of the rotary engine with two rotors  351  and  352  within stator  401 , each having two lobes, rotor  351  is leading and rotor  352  is following. There is a single combustion chamber  213  and a single exhaust pipe  174 , with all the other appurtenant parts being the same or essentially similar to those shown in  FIG. 7 . The principle of operation of this embodiment is similar to the one shown in  FIG. 7  under its start-up, idling, and low load modes of operation. 
         [0074]    Reference is made to  FIG. 9 , which shows another embodiment of the rotary engine with stator  402  and three rotors  353 ,  354 , and  355 , each rotor having four lobes, with rotors  354  and  355  leading and rotor  353  following. There are two combustion chambers  214  and  215 , and two exhaust pipes  175  and  176 . In most other respects and principles of operation, this embodiment is essentially similar to that shown in  FIG. 7 . 
         [0075]    Referring to  FIG. 10 , which shows another embodiment of the rotary engine with stator  403 , one rotor  356  with four lobes, two combustion chambers  216  and  217 , and two exhaust pipes  177  and  178 , it can be said that with the exception of rotor  356  itself, in most other respects and principles of operation this embodiment is essentially similar to that shown in  FIG. 7 . 
         [0076]    Similar to the embodiment shown on  FIG. 7 , embodiments shown on  FIGS. 9 and 10  can be tuned to run with one or both sets of fuel injection and combustion equipment working, depending on the load and power requirements, or with one or both sets supplying only compressed air, as when used, for example, in a hybrid vehicle. 
         [0077]    Reference is made to  FIG. 11 , which shows another embodiment of the rotary engine with stator  404  and two rotors  357  and  358 , each having five lobes. In this embodiment, there are three combustion chambers,  218 ,  219 , and  220 , all leading to a single exhaust pipe  179 . There are three sets of combustion equipment, consisting of fuel injection control valves  270 ,  271 , and  272 ; air injection control valves  280 ,  281 , and  282 ; fuel injectors  250 ,  251 , and  252 ; air injectors  260 ,  261 , and  262 ; and spark plugs  290 ,  291 , and  292 . In most other respects and principles of operation, this embodiment is essentially similar to that shown in  FIG. 7 . 
         [0078]    Another distinct feature of this embodiment, which is different from other shown embodiments, is radiating air ducts  390  of small diameter passing through each of the five lobes of each of the two rotors  357  and  358 , emanating from the center of each rotor. These air ducts  390 , which could be less than 1 mm in diameter, deliver compressed air from air compressor  320  via compressed air line  300 , enter the housing of stator  404  and are connected to each of the hollow rotor axles, from which the air spreads through inside of the rotors, cooling them, and exiting the rotors into the inside of the stator, cooling the inner surfaces of stator  404 . This serves as the cooling system of the rotary engine in this particular embodiment, which may totally obviate the need for liquid cooling. 
         [0079]    Yet another distinct feature of this embodiment is the way the three sets of air and fuel combustion equipment—namely, the air and fuel injectors and control valves, as well as the spark plugs—are used. These could be configured in such a way as to deliver the air and fuel only into the middle combustion chamber  213 , while the other two combustion chambers  211  and  212  would only be supplied with compressed air. This would serve to complete the combustion of the unburned air and fuel mixture, coming from the middle combustion cavity  213 , as well as to cool rotors  357  and  358 , and stator  404 . 
         [0080]    Alternatively, all three combustion cavities in the embodiment shown in  FIG. 11  could be used to inject air and fuel, thereby increasing the output power by about a factor of three as compared to the previous example. There could also be other embodiments providing useful combinations of the combustion equipment controlled by controller  340 . For example, yet another, fourth set of combustion equipment (injectors, valves, spark plug) could be added to the shown configuration, creating another combustion chamber so as to increase the total output power of the engine. 
         [0081]    In general, the greater the number of combustion chambers, the greater the power output of the rotary engine. The number of combustion chambers may be increased by increasing the number of rotors and/or the number of rotor lobes per rotor. Furthermore, rotary engine modules of any of the above designs could be stacked together to provide even higher output power, if desired.