Abstract:
A highly-efficient, yet simply constructed internal combustion engine includes an intake cylinder to accommodate intake and pre-compression of an oxidizing agent, a combustion cylinder to accommodate a further compression of the oxidizing agent, an injection and ignition of fuel, and a partial expansion of combustion gases produced by the ignition of fuel; and an exhaust cylinder to accommodate a further expansion of the combustion gases and subsequent exhausting of the further expanded combustion gases. A reciprocating piston is inside each of the intake, combustion and exhaust cylinders and a crankshaft is coupled to the reciprocating pistons. A first transfer passage facilitates flow of the pre-compressed oxidizing agent from the intake cylinder to the combustion cylinder and a second transfer passage facilitates flow of the partially-expanded combustion gases from the combustion cylinder to the exhaust cylinder.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of and claims priority to copending U.S. Application entitled, “RECIPROCATING INTERNAL COMBUSTION ENGINE,” having Ser. No. 14/039,432, filed Sep. 27, 2013, which is entirely incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This disclosure relates to a reciprocating internal combustion engine and, more particularly, relates to a high-efficiency, reciprocating, internal combustion engine. 
       BACKGROUND 
       [0003]    A reciprocating internal combustion engine is a heat engine that uses one or more reciprocating pistons to convert the energy of a combusting fuel into a rotating motion. 
         [0004]    In a typical reciprocating internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by the combustion of fuel inside a cylinder applies force to drive a piston inside the cylinder. This force moves the piston over a distance thereby transforming the chemical energy of the fuel into useful mechanical energy. 
       SUMMARY OF THE INVENTION 
       [0005]    In one aspect, a highly-efficient, yet simply constructed internal combustion engine includes an intake cylinder to accommodate intake and pre-compression of an oxidizing agent, a combustion cylinder to accommodate a further compression of the oxidizing agent, an injection and ignition of fuel, and a partial expansion of combustion gases produced by the ignition of fuel; and an exhaust cylinder to accommodate a further expansion of the combustion gases and subsequent exhausting of the further expanded combustion gases. A reciprocating piston is inside each of the intake, combustion and exhaust cylinders and a crankshaft is coupled to the reciprocating pistons. A first transfer passage facilitates flow of the pre-compressed oxidizing agent from the intake cylinder to the combustion cylinder and a second transfer passage facilitates flow of the partially-expanded combustion gases from the combustion cylinder to the exhaust cylinder. 
         [0006]    In another aspect, a method includes: pre-compressing an oxidizing agent with a reciprocating piston inside an intake cylinder of an internal combustion engine; further compressing the pre-compressed oxidizing agent, injecting and igniting fuel into the further compressed oxidizing agent, and accommodating a partial expansion of resulting combustion gases to drive a reciprocating piston inside a combustion cylinder of the internal combustion engine; and enabling the combustion gases to further expand inside an exhaust cylinder of the internal combustion engine and expelling the further expanded combustion gases out of the exhaust cylinder with a reciprocating piston inside the exhaust cylinder. The reciprocating pistons inside the intake, combustion and exhaust cylinders are coupled to a crankshaft of the internal combustion engine. 
         [0007]    In some implementations, the engine employs the Brayton cycle spread across three separate cylinders. 
         [0008]    In some implementations, one or more of the following advantages are present. 
         [0009]    For example, a highly-efficient engine that has a relatively simple design and construction may be provided. In addition, the engine may have a compact size relative to conventional compression-ignition engines. Moreover, the engine may have the ability to burn natural gas by utilizing a high overall compression ratio that is not achievable in conventional engines. 
         [0010]    Other features and advantages will be apparent from the description and drawings, and from the claims. 
         [0011]    Relative terms, such as “lower,” “upper,” “horizontal,” “vertical,”, “above”, “below”, “up”, “down”, “top” and “bottom” as well as derivative thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to apply only to certain orientations (e.g., a particular orientation being described or shown in a drawing being discussed). These relative terms are used for convenience only and do not require that the apparatus be constructed or operated in a particular orientation. 
         [0012]    The dead center in an engine is the position of a piston in which it is farthest from, or nearest to, the crankshaft. The former is known as top dead center (TDC) and the latter is known as bottom dead center (BDC). These phrases, top dead center and bottom dead center, are used throughout the present disclosure and should be construed broadly in manner consistent with their respective meanings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIGS. 1-3  are partial cross-sectional views showing one implementation of a reciprocating internal combustion engine at various stages of the engine&#39;s operation. 
       
    
    
       [0014]    Like reference numerals in the figures refer to like elements. 
       DETAILED DESCRIPTION 
       [0015]    The engine  100  shown in  FIGS. 1-3  has two power-generating sections  102   a  and  102   b,  each of which is configured to deliver mechanical energy to a common crankshaft  104 . Power-generating section  102   a  includes three in-line cylinders that are on a first side of the common crankshaft  104  and power-generating section  102   b  includes three in-line cylinders that are on a second side of the common crankshaft  104 . 
         [0016]    As discussed in detail herein., the three cylinders in each power-generating section  102   a,    102   b  cooperate to accommodate the steps required to conduct one complete engine operating cycle. In general terms, these steps include intake, compression, combustion, expansion and exhaust. More particularly, as discussed herein, the steps required to conduct one complete engine operating cycle (i.e., intake, compression, combustion, expansion and exhaust) are spread out among the three cylinders in each power-generating section  102   a,    102   b.    
         [0017]    In each power-generating section  102   a,    102   b,  the three cylinders include: an intake cylinder  108 , a combustion cylinder  110  and an exhaust cylinder  112 . A first transfer passage  114  extends between the intake cylinder  108  and the combustion cylinder  110 . A second transfer passage  16  extends between the combustion cylinder  110  and the exhaust cylinder  112 . 
         [0018]    An intake valve  118  is provided to regulate the flow of fluid (e.g., air) into the intake cylinder  108 . A first transfer valve  120  is provided to regulate the flow of fluid (e.g., air) through the first transfer passage  114  from the intake cylinder  108  to the combustion cylinder  110 . A second transfer valve  122  is provided to regulate the flow of fluid (e.g., combustion gases) through the second transfer passage  116  from the combustion cylinder  110  to the exhaust cylinder  112 . An exhaust valve  124  is provided to regulate the flow of fluid (e.g., exhaust gases) out of the exhaust cylinder  112 . 
         [0019]    In the illustrated implementation, each valve  118 - 124  is poppet that consists of a hole at the top of one of the cylinders, and a tapered plug on the end of a shaft (also known as a valve stem). The portion of the hole where the plug mates to it is called the valve seat. In a typical implementation, the shaft would guide the plug portion by sliding through a valve guide (not shown). 
         [0020]    According to the illustrated implementation, in each power-generating section  102   a,    102   b,  the intake valve  118  is at the top of the intake cylinder  108 , the first and second transfer valves  120 ,  122  are at the top of the combustion cylinder  110  and the exhaust valve  124  is at the top of the exhaust cylinder  112 . 
         [0021]    In a typical implementation, the valves are controlled by a valve actuator  125 . More particularly, the valve actuator is configured to control (e.g., open and close) the intake valve, the first transfer valve, the second transfer valve and the exhaust valve at appropriate times in the engine&#39;s operating cycle to support appropriate engine operations. 
         [0022]    There is a reciprocating piston inside each cylinder. More particularly, there is a reciprocating intake piston  126  inside each intake cylinder  108 ; there is a reciprocating combustion piston  128  inside each combustion cylinder  110 ; and there is a reciprocating exhaust piston  130  inside each exhaust cylinder  112 . The reciprocating pistons are arranged such that each piston reciprocates inside one of the intake, combustion and exhaust cylinders in a direction that is substantially perpendicular to an axis of the crankshaft. Moreover, each reciprocating piston in a particular one of the power-generating sections  102   a,    102   b  is substantially parallel to the other reciprocating pistons in its power-generating section. This type of arrangement is not required, of course. Instead of being parallel, the reciprocating pistons in the particular power-generating sections  102   a,    102   b  can be arranged radially around the crankshaft, for instance. Other types of arrangements are possible as well. 
         [0023]    In the illustrated implementation, the three cylinders  108 - 112  in each power-generating section  102   a,    102   b  have different bore sizes. For example, in each power-generating section  102   a,    102   b,  the combustion cylinder  110  has the smallest bore size, the exhaust cylinder  112  has the largest bore size, and the intake cylinder  108  has a bore size that is between the bore size of the combustion cylinder  110  and the bore size of the exhaust cylinder  112 . Each piston has a diameter that corresponds to the bore size of its associated cylinder. 
         [0024]    In certain implementations, the ratios of intake piston diameter to combustion piston diameter to exhaust piston diameter to piston stroke is: 2.15:1:3.37:1.18. Of course, each of these dimensions can vary (e.g., approximately +/−% 15, or more) relative to one or more of the other specified dimensions. How they vary may depend, for example, on the specific desired engine operational characteristics of the particular engine. 
         [0025]    Each piston  126 - 130  is coupled to the common crankshaft  104  via a respective connecting rod  132  and connecting rod bearings  134 . The common crankshaft  104  is configured to translate the reciprocating, linear motion of the pistons into a rotational motion and vice versa. 
         [0026]    In each power-generating section  102   a,    102   b,  there is a fuel injection mechanism arranged to inject fuel into combustion cylinder  110  at an appropriate point in the engine&#39;s operating cycle. In the illustrated implementation, the fuel injection mechanisms are fuel injectors  134 . Notably, the intake cylinders  108  and the exhaust cylinders  112  do not have any fuel injectors or other fuel injection mechanisms. This is because, in each power-generating section  102   a,    102   b,  fuel is directly injected only into the combustion cylinder  110 , not into the intake  108  or exhaust  112  cylinders. 
         [0027]    In some implementations, fuel may be injected into the first transfer passage between the intake cylinder and the combustion cylinder. This may be done instead of or in addition to injecting fuel directly into the combustion cylinder. This dual- injection technique may be useful, for example, in applications where two different fuels are used. In some implementations, it may be desirable to inject fuel into the intake cylinder. This, too, may be done instead of or in addition to injecting fuel directly into the combustion cylinder and/or the first transfer passage. 
         [0028]    The illustrated engine is a compression-ignition engine (i.e., the engine uses the heat of compression to initiate ignition for burning fuel that has been injected into the engine. However, in some implementation, there may be a different source of ignition (e.g., a spark plug) configured to ignite the fuel that is injected into the combustion cylinder  110 . Notably, in engines that utilize spark-ignition, the intake cylinders  108  and the exhaust cylinders  112  would not have any source of ignition, such as a spark plug. This is because, in each power-generating section  102   a,    102   b  of a similar, spark-ignition, type of engine, fuel would be ignited only in the combustion cylinder  110 , not in the intake  108  or exhaust  112  cylinders. 
         [0029]    A discussion of how the illustrated engine  100  operates follows. This discussion focuses primarily on power-generating section  102   a.  It should be understood, however, that power-generating section  102   b  has similar physical and operational characteristics as power-generating section  102   a  and operates in similar and coordinated manner with power-generating section  102   a  to cooperatively deliver useable mechanical energy to crankshaft  104 . 
         [0030]    In general, and as discussed in further detail below, the intake cylinder  108  accommodates intake and pre-compression of an oxidizing agent (e.g., air); the combustion cylinder  110  accommodates further compression of the oxidizing agent, fuel injection and ignition of the injected fuel and a partial expansion of the resulting combustion gases; and the exhaust cylinder  112  accommodates a further expansion of the combustion gases and ultimately exhausting the expanded combustion gases from power-generating section  102   a.    
         [0031]    In  FIG. 1 , oxidizing agent (e.g., is being drawn into the intake cylinder  108 , fuel combustion has just begun or is about to begin in the combustion cylinder  110  and expanded combustion gases are being expelled from the exhaust cylinder  112 . 
         [0032]    The intake valve  118  is in an open position and the reciprocating piston inside the intake cylinder  108  is moving in a downward direction from top dead center to bottom dead center thereby drawing air into the intake cylinder  108 . In some implementations, the intake valve  118  remains open for most, if not all, of the time that the reciprocating piston inside the intake cylinder  108  is moving from top dead center to bottom dead center. 
         [0033]    The exhaust valve  124  is in an open position and the reciprocating piston inside the exhaust cylinder  112  is moving in an upward direction from bottom dead center to top dead center thereby expelling expanded combustion gases from the exhaust cylinder  122  In some implementations, the exhaust valve  124  remains open for most, if not all, of the time that the reciprocating piston inside the exhaust cylinder  112  is moving from bottom dead center to top dead center. 
         [0034]    Both transfer valves  120 ,  122  are in a closed position and the reciprocating piston inside the combustion cylinder  110  is at approximately top dead center. In a typical implementation, this would be just after the fuel has been injected (by fuel injector  136 ) and ignited (e.g., by heat of compression). The resulting combustion gases inside the combustion cylinder  110  are just starting to expand in the combustion cylinder  110  and drive the reciprocating piston inside the combustion cylinder  110  in a downward direction from top dead center (as shown in  FIG. 1 ) toward bottom dead center. In some implementations, the transfer valves  120 ,  122  remain closed for most, if not all, of the time that the reciprocating piston inside the combustion cylinder  110  is moving from top dead center to bottom dead center. 
         [0035]    The crankshaft  104 , which is coupled to the reciprocating pistons inside the intake cylinder, combustion cylinder and exhaust cylinder, is translating the linear motion of the reciprocating piston in the combustion cylinder  110  into a rotational motion and, at the time depicted in  FIG. 1 , driving the reciprocating pistons in the intake cylinder  108  and exhaust cylinder  112 . 
         [0036]    In  FIG. 2 , the illustrated engine components are configured as they would be approximately 90 degrees after their configuration shown in  FIG. 1 . 
         [0037]    The intake valve  118  and the first transfer valve  120  are in a closed position and the reciprocating piston inside the intake cylinder  108  has just passed bottom dead center and started moving in an upward direction from bottom dead center to top dead center thereby compressing the charge of air that previously was drawn into the intake cylinder  108 . 
         [0038]    Since the charge of air being compressed in the intake cylinder  108  in  FIG. 2  is further compressed in the combustion cylinder  110  at a subsequent point in time, the compression that occurs in the intake cylinder  108  is referred to in some places herein as a pre-compression. 
         [0039]    In some implementations, the intake valve  118  remains closed for most, if not all, of the time that the reciprocating piston inside the intake cylinder  108  is moving from bottom dead center to top dead center. Additionally, in some implementations, the first transfer valve  120  remains closed for part of the time that the reciprocating piston inside the intake cylinder  108  is moving from bottom dead center to top dead center. 
         [0040]    The reciprocating piston inside the combustion cylinder  110  is approximately at the center of its expansion stroke and is moving in a downward direction from top dead center to bottom dead center. 
         [0041]    The second transfer valve  122  between the combustion cylinder  110  and the exhaust cylinder  112  has just opened. At this point, the reciprocating piston inside the exhaust cylinder  112  is at or very near top dead center and the volume of space inside the exhaust cylinder  112  (i.e., between the top of the reciprocating piston inside the exhaust cylinder  112  and the cylinder head) is quite small. This advantageously minimizes blow down losses between the combustion cylinder  110  and the exhaust cylinder  112 . In some implementations, the second transfer valve  122  will close when the reciprocating piston inside the combustion cylinder reaches close to bottom dead center. This means that there is generally some retained combustion gas. Just as the reciprocating piston inside the combustion cylinder reverses direction, the first transfer valve between the intake and combustion cylinders opens and the intake piston pushes a fresh charge of air in. 
         [0042]    The exhaust valve  124  is in a closed position and the exhaust piston is just beginning or is about to begin its expansion stroke, moving from top dead center to bottom dead center. In some implementations, the exhaust valve  124  remains closed for most, if not all, of the exhaust piston&#39;s expansion stroke, moving from top dead center to bottom dead center. In some implementations, the exhaust valve  124  opens when the reciprocating piston inside the exhaust cylinder is close to, at or just past bottom dead center at the end of its expansion stroke. 
         [0043]    With the engine configured as shown in  FIG. 2 , the combustion gases can expand to drive the reciprocating piston inside the combustion cylinder  110  and to drive the reciprocating piston inside the exhaust cylinder  112 . The crankshaft  104 , which is coupled to the reciprocating pistons inside the intake cylinder, combustion cylinder and exhaust cylinder, is translating the linear motion of the reciprocating pistons inside the combustion cylinder  110  and inside the exhaust cylinder  112  into a rotational motion and driving the reciprocating piston inside the intake cylinder  108 . 
         [0044]    A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the present disclosure. For example, the relative bore sizes of the intake, combustion and exhaust cylinders may differ from what has been disclosed herein. In some implementations, the bore sizes of these three cylinders may be substantially the same as one another. 
         [0045]    The specific timing of various engine operations (e.g., valve timing, fuel injection timing, etc.) may vary. 
         [0046]    The intake, first and second transfer, and exhaust valves may be of a different style, size and/or arrangement than what is disclosed herein. For example, the valves may be sleeve valves instead of poppet valves. There may be two, three, four, five or more valves per cylinder. 
         [0047]    In addition, the engine may include any number of cylinders as long as that number is a multiple of three (3). So, for example, the engine may include three cylinders, six cylinders, nine cylinders, twelve cylinders, fifteen cylinders, eighteen cylinders, etc. Each set of three cylinders would include an intake, combustion and exhaust cylinder. 
         [0048]    The engine can be arranged with an in-line engine design, (e.g., a straight engine with all of the cylinders placed in a single row), a U-engine design (e.g., two separate straight engines with crankshafts linked by a central gear), a V-engine design (e.g., two banks of cylinders at an angle, most commonly 60 or 90 degrees), a flat engine design (e.g., two banks of cylinders directly opposite each other on either side of the crankshaft), and any other type of engine design. 
         [0049]    The relative order of cylinders (i.e., intake, combustion and exhaust) may differ from what has otherwise been disclosed herein. So, for example, the intake cylinder  108  may be physically positioned between the combustion cylinder  110  and the exhaust cylinder  112 . 
         [0050]    The valve actuator  125  may include a camshaft that revolves at some fixed speed relative to the crankshaft speed (e.g., half-speed). The camshaft may be driven in any convenient manner, including for example, by chain, gear or toothed belt driven from the crankshaft, and can be located, for example, in the engine&#39;s crankcase or in the cylinder head. Valves could also be driven electrically or hydraulically. Valve timing could vary depending on engine operating conditions. 
         [0051]    The physical arrangement of the transfer passages may differ. Moreover, the physical positions of the transfer valves in connection with those transfer passages may differ as well. For example, in some implementations, the first transfer valve  120  may be at the beginning of the first transfer passage  114  in the cylinder head of the intake cylinder  108 . Likewise, in some implementations, the second transfer valve may be at the end of the second transfer passage  116  in the cylinder head of the exhaust cylinder  112 . 
         [0052]    The various components disclosed can have a variety of shapes and sizes. 
         [0053]    The techniques, components and systems disclosed herein can be adapted for use in connection with a variety of different engine styles including, for example, engines that run on diesel fuel or other heavy fuels, engines that run on gasoline or alcohols and engines with or without spark ignition. 
         [0054]    Engines implementing the techniques disclosed herein can be used in connection with a wide variety of applications including, for example, aircraft auxiliary power units, alternative light vehicle engines, marine engines, on-highway truck engines, military unmanned aerial vehicles, tactical vehicle engines, stationary power generation, and aircraft engines. 
         [0055]    The engine can be adapted to include any number of optional accessories (e.g., turbochargers, superchargers, etc.) that might be used in a conventional engine to enhance efficiency. 
         [0056]    Other implementations are within the scope of the claims.