Baker, Douglas M. (8074 Lake Crest Drive Ypsilanti, MI, 48197, US)
|1.||An engine comprising: an engine block having a compression cylinder and an expansion cylinder defined therein; a compression reciprocator located in said compression cylinder, an expansion reciprocator located in said expansion cylinder, said reciprocators each connected to a crankshaft and said reciprocators each mounted for reciprocating movement within said cylinders; a prechamber tube having two, constant volume, combustion chambers defined therein and a longitudinal tube axis defined therethrough, said chambers being located on opposing sides of said tube and being generally outwardly concave in shape; a housing having portions defining a cavity for receiving said tube therein, said housing coupled to said engine block and including portions defining an induction port and an expansion port, said ports respectively forming passageways between said tube and said compression cylinder and between said tube and said expansion cylinders, said tube rotatably supported by said housing and oriented with said tube axis being generally transverse to cylinder axes defined by said compression and expansion cylinders, rotation means for rotating said tube; timing means for coordinating movement of said reciprocators and rotation of said tube; a fuel injector positioned to inject fuel into said combustion chambers; and whereby said tube is rotated such that said chambers are successively brought into communication through said induction port with said compression cylinder, then separated from communication with said compression cylinder and brought into a position to receive fuel from said fuel injector, and then brought into communication through said expansion port with said expansion cylinder.|
|2.||An engine as set out in Claim 1 wherein said induction and expansion ports define a port angle said port angle being less than 120 degrees.|
|3.||An engine as set out in Claim 1 wherein said induction and expansion ports define a port angle, said port angle being in the range of about 85 to 100 degrees.|
|4.||An engine as set forth in Claim 1 wherein said induction and expansion ports define a port angle, said port angle being in the range of about 90 to 95 degrees.|
|5.||An engine as set forth in Claim 1 wherein said compression and expansion cylinders define a bank angle, said bank angle being less than 90 degrees.|
|6.||An engine as set forth in Claim 1 wherein said bank angle being in the range of about 40 to 70 degrees.|
|7.||An engine as set forth in Claim 1 wherein said combustion chambers define a bowl angle, said bowl angle being less than ninety degrees.|
|8.||An engine as set forth in Claim 1 wherein said bowl angle being in the range of about fortyfive to sixtyfive degrees.|
|9.||An engine as set forth in Claim 1 wherein said housing includes portions defining coolant passageways therethrough.|
|10.||An engine as set forth in Claim 9 wherein water is circulated through said coolant passageways.|
|11.||An engine as set forth in Claim 1 wherein said tube includes portions defining coolant passageways therethrough.|
|12.||An engine as set forth in Claim 11 wherein oil is circulated through said coolant passageways.|
|13.||An engine as set forth in Claim 12 wherein said oil lubricates sealing rings on said tube.|
|14.||An engine as set forth in Claim 13 wherein said oil is centrifugally supplied to said sealing ring through ducts defined in said tube.|
|15.||An engine as set forth in Claim 13 wherein radial pins prevent relative rotation of said sealing rings relative to said tube.|
|16.||An engine as set forth in Claim 1 wherein said timing means is variable to vary advance of said expansion reciprocator relative to said compression reciprocator.|
|17.||An engine as set forth in Claim 1 wherein said timing means is variable to advance and retard said tube relative to one of said compression reciprocator and expansion reciprocator, or both said compression and expansion reciprocators.|
|18.||An engine as set forth in Claim 1 wherein said reciprocators are connected to a common crankshaft.|
|19.||An engine as set forth in Claim 1 wherein said reciprocators are each connected to separate crankshafts.|
|20.||An engine as set forth in Claim 1 wherein said combustion chambers are defined by inserts removable mounted to said tube.|
|21.||An engine as set forth in Claim 20 wherein said inserts are interchangeable with other inserts of different volume.|
|22.||An engine as set forth in Claim 20 wherein said inserts are constructed of steel.|
|23.||An engine as set forth in Claim 1 wherein said expansion port includes a liner insert mounted therein.|
|24.||An engine as set forth in Claim 23 wherein said liner is constructed of steel.|
|25.||An engine as set forth in Claim 1 wherein said cavity of said housing includes a sleeve liner insert mounted therein.|
|26.||An engine as set forth in Claim 25 wherein said sleeve liner is constructed of steel.|
|27.||An engine as set forth in Claim 1 wherein said expansion cylinder includes scavenging ports and exhaust ports defined therein.|
|28.||An engine as set forth in Claim 27 wherein said scavenging ports are coupled to a crankcase enclosing said crankshaft and providing positive air pressure for crankcase scavenging of said expansion cylinder.|
|29.||An engine as set forth in Claim 1 wherein said compression cylinder includes scavenging ports defined therein, intake valves being positioned in said cylinder and providing for charging of said compression cylinder during an expansion stroke thereof.|
|30.||An engine as set forth in Claim 1 further comprising scavenging means for scavenging said combustion chambers.|
|31.||An engine as set forth in Claim 30 wherein said scavenging means includes a blower.|
|32.||An engine as set forth in Claim 1 further comprising a water pump, said pump being coupled to and driven by an output shaft of said tube.|
|33.||An engine as set forth in Claim 1 wherein said engine is a diesel engine.|
|34.||A method of operating an engine, said method comprising the steps of: inducting a volume of air into a compression cylinder; compressing the volume of air in the first cylinder of the engine; transferring the compressed volume of air from the first cylinder to a constant volume combustion chamber; mixing fuel with the compressed volume of air in the combustion chamber; igniting the mixture of fuel and compressed volume of air in the combustion chamber; burning the mixture in the combustion chamber; porting the burning mixture to mix with a compressed volume of air in an expansion cylinder of the engine; further compressing the burning mixture after initial porting to the expansion cylinder thereby further burning the mixture within the expansion cylinder and enhancing combustion efficiency of the engine; expanding the volume of the burned mixture in the expansion cylinder and the combustion chamber; extracting work during expansion of the volume of the burned mixture in the expansion cylinder and the combustion chamber; and exhausting combustion biproducts from the expansion cylinder.|
|35.||The method of Claim 34 further comprising the step of isolating the volume of compressed air in the combustion chamber from the compression cylinder.|
|36.||The method of Claim 34 wherein said mixing step includes the steps of injecting fuel into the combustion chamber and moving the combustion chamber relative to the point of fuel injection as the fuel is injected.|
|37.||The method of Claim 34 wherein said igniting step is compression induced.|
|38.||The method of Claim 34 wherein said mixing step includes the step of moving the compressed volume of air in the combustion chamber past a fuel injector and injecting fuel into the compressed volume of air in the combustion chamber while the compressed volume is moved therepast.|
|39.||The method of Claim 38 wherein the injection occurs during the substantial entirety as the combustion chamber is moved therepast.|
|40.||The method of Claim 34 wherein said mixing of fuel creates a fuel rich mixture.|
|41.||A method of extracting work from a combustible fluid, said method comprising the steps of: compressing a volume of air; injecting fuel into the compressed volume of air creating a fuel/air mixture; combusting the fuel/air mixture while maintaining a constant volume during a portion of the combustion process; partially compressing a second volume of air; porting the fuel/air mixture undergoing combustion to the partially compressed second volume of air thereby forming a third volume and enhancing combustion of the fuel/air mixture; compressing the third volume and continuing combustion thereof; and expanding the third volume and extracting work during the expansion of the third volume.|
|42.||The method of Claim 41 further comprising the step of isolating the compressed volume of air after said compressing step.|
|43.||The method of Claim 41 wherein said injecting step includes the step of varying the point of injection of the fuel relative to the compressed volume, the varying being done over the duration of the injecting step.|
|44.||The method of Claim 41 further comprising the step of operating a compression cycle including said step of compressing a volume of air is performed and further comprising the steps of isolating a substantial portion of the compressed volume of air from a remaining volume, expanding the remaining volume and reducing pressure thereof to near vacuum, intaking a volume of air to replace said vacuum and compressing the volume of air and repeating the cycle.|
|45.||The method of Claim 41 further comprising the step of operating an expansion cycle including the step of partially compressing a second volume of air, porting the combusting fuel/air mixture into the second volume of air to form the third volume, compressing the third volume and further combusting the fuel/air mixture thereof, expanding the third volume and extracting work exhausting the third volume and utilizing a volume of air, partially compressing the volume of air and repeating the cycle.|
2. Description of the Prior Art Numerous different engine designs have been developed to the point where today, engine design is a matured technology. Two of the most popular gas cycles for operating engines are the Otto cycle, utilized by the internal combustion engine, and the diesel cycle, utilized by the diesel engine.
The Spark-Ignition internal combustion or SI engine uses a highly volatile fuel, gasoline, and a spark to initiate combustion in its cylinders. Both the compression and expansion portions of the cycle are conducted in that same cylinder. While SI engines have been developed with high power densities (as used herein the term"high power density" means a horsepower to weight ratio or a horsepower to cubic inch ratio of at least 1.0), they suffer from two major drawbacks, namely fuel consumption and the volatility of gasoline.
The volatility of gasoline is well documented and the problems associated with storage, transportation and use in remote locations need not be further discussed herein. Regarding economy and durability, while significant gains have been made in recent years regarding the fuel economy and durability of SI engines, these engines still lack the capabilities of their diesel engine counterparts.
Unlike an SI engine, a diesel compression ignition or Cl engine initiates combustion through the development of high pressure and autoignition temperature within the cylinder.
When temperature and pressure are risen high enough, autoignition of the fuel results without a spark. While being superior to Si engines in terms of fuel economy and the less volatile nature of diesel fuel, Cl engines have exhibited low power densities in comparison to SI engines. Previous efforts to design increased power density, small size diesel engines have been plagued by problems of bulky two-stroke superchargers, limited-pressure cycles, structural durability due to excessive mechanical and thermal loading and notoriously poor fuel consumption.
In view of the above and other limitations of the various prior art engines, it can be seen that there exists a need for a high power density, diesel engine. It is therefore an object of this invention to provide such an engine. It is also an object of this invention to provide a novel gas cycle for operation of such an engine.
SUMMARY OF THE INVENTION In meeting the above and other objects, the present invention provides a diesel engine design with an attractive, high power density potential, while maintaining desired fuel economy. The basic principal of the engine itself is well premised: increase mean effective pressures by reducing the expansion ratio of the working fluid within the reciprocator and while using recovery system to recapture exhaust energy and provide boost. However, unlike conventional diesels, which suffer from insufficient auto-ignition pressures at start up and require heavy components and late injection techniques to control peak combustion pressures, the present design isolates the compression and expansion processes, allowing for independent compression and expansion ratios, and combines constant volume combustion with port-controlled expansion. This enables this present invention to outperform existing engines and gas cycles while operating at lower peak expansion pressures, similar to those typical for gasoline engines.
The gas cycle of the present invention occurs simultaneously within three interdependent chambers: a compression cylinder, a combustion chamber and an expansion cylinder. At start-up, the compression cylinder inducts fresh air through lower intake ports, similar to a conventional two stroke diesel. The mass within the compression cylinder is subsequently compressed by the upward or compression stroke of the compression piston and is transferred into a combustion chamber via induction ports.
Slightly after top dead center (TDC) of the compression piston, the combustion chamber, and the compressed mass contained therein, is abruptly separated from the compression cylinder. With a minimal headspace, only a minimum volume remains within the compression cylinder. The compression piston is then stroked downward on its expansion stroke and the compression cylinder is provided with an initial rapid decrease in pressure that then continues to slowly drop to near vacuum. As the compression piston continues its downward stroke, the lower intake ports are opened and a fresh charge rushes in to fill the near vacuum. During the compression piston's next upward or compression stroke, shortly after closing off the intake ports, the compression piston begins to compress a second mass. Before top dead center (BTDC), a second combustion chamber is brought into communication with the second compressed mass until slightly after TDC, when this second compression chamber is also abruptly separated from the compression cylinder. Thereafter, the compression piston begins its downstroke and repeats its cycle.
After being separated or isolated from the compression cylinder, the combustion chamber containing the compressed mass is injected with fuel. The chambers themselves can be provided with glow plugs and the injection of fuel is initially directed onto the glow
plugs to initiate compression. As the fuel injection period progresses, the glow plug is moved away from the location of the injection spray resulting in the injection spray being swept across the chamber thereby providing good fuel distribution therein. At this point of the cycle, constant volume combustion is fully developed and ongoing in the combustion chamber.
The combustion chamber, containing a partially burned charge, is then brought into communication with the expansion cylinder. Prior to the combustion chamber being ported into the expansion cylinder, the expansion piston has begun its compression stroke covering exhaust and scavenging ports during its upward movement. A mixture of scavenged and residual mass within the cylinder is compressed as the expansion piston approaches TDC.
At this point, the partially burned mass within the combustion cylinder is introduced to the compressed mass of the expansion cylinder. Pressure within the expansion cylinder rises as the high pressure combusting mixture enters from the combustion chamber. The expansion cylinder thereafter compresses the combined mass as combustion continues to take place as a result of the new introduction of oxygen.
The expansion piston extracts work from the combustion process during its expansion stroke. As the expansion piston is stroked downward, the piston opens to exhaust ports and the residual mass is exhausted. As the expansion piston continues its downward stroke, the piston opens to scavenging ports and fresh air scavenging occurs within the expansion cylinder. After bottom dead center (BDC), the expansion piston closes off the scavenge and exhaust ports and begins to compress the mixture of scavenged and residual mass therein, preparing for mixing with the combusting mass in the second combustion chamber. After mixing, further compression and burning, the expansion piston again begins its downward stroke with work again being extracted. The expansion piston then repeats its cycle.
After dumping to the expansion cylinder, the combustion chamber is abruptly isolated from the expansion cylinder and opened for scavenging of any residual combustion products therein. After scavenging, the combustion chamber is closed off preparing for opening to the compression cylinder and repeating of the combustion chamber's cycle.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic illustration of an engine embodying the principes of the present invention; Figure 2 is a schematic illustration of the engine seen in Figure 1 and further showing the primary components of the present invention and their inter-relation with one another, with the compression piston being illustrated near BDC; Figures 3a and 3b are schematic illustrations similar to Figure 2 illustrating the compression piston at TDC and further defining some design parameters of the present invention; Figures 4a, 4b and 4c schematically illustrate airflow at various stages of the gas cycle of the present invention; Figures 5a and 5b are schematic illustrations similar to Figure 1 respectively illustrating the closing of the induction port and the opening of the blowdown port in the present invention and the injection of fuel into the combustion chamber; Figure 6a is a schematic illustration showing the piston position utilized in determining the geometric compression ratio of the compressor; Figure 6b is a schematic illustration illustrating the compressor piston positioned in determining the geometric compression ratio including both the compression cylinder and the combustion chamber; Figure 6c is a schematic illustration showing the expansion piston positions in defining the geometric compression ratio of the expansion cylinder; Figure 6d is a schematic illustration showing the piston positions in defining the geometric compression ratio of the expansion cylinder and the combustion chamber; Figure 7 is a perspective view of the rotary prechamber tube utilized in the present invention further illustrating one of the combustion chambers formed therein; Figure 8 is a sectional view of the tube seen in Figure 7 further illustrating the coolant passageway through the tube and a removable insert for defining the combustion chamber itself; Figure 9 is a graph of the ideal gas cycle of the present invention; Figures 10 and 11 are schematic illustrations of further embodiments of the present invention; and Figures 12a, 12b, 13a and 13b schematically show the timing configurations which may be utilized with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, an engine embodying the principles of the present invention is schematically illustrated in Figure 1 and generally designated at 10. The engine principally includes a lower unit or engine block 12, an upper unit or tube housing 14, timing belts, illustrated as being enclose beneath a cover 16, an exhaust manifold 18 (which will vary depending on the number of cylinders in the engine 10), and a scavenging manifold 20 illustrated as being associated with the housing 14. Before going into a discussion of the interior workings of the engine 10, it is believed there is a need for a discussion of the ideal gas cycle illustrated in Figure 9.
As seen in Figure 9, the ideal gas cycle actually consists of two inter-related cycles, one for the compression cylinder or compressor and one for the expansion cylinder or expander. The compression cylinder cycle will first be discussed. Obviously the volumes illustrated in this discussion of the ideal cycle are for illustrative purposes only and will actually depend on the specific implementation of the engine 10.
At the bottom of the stroke, the volume of the compression cylinder at bottom dead center or BDC (Vgoc) is illustrated as being just greater than eight cubic inches. Upon the opening of the combustion chamber to the compression cylinder, the combined volume increases to approximately 9 cubic inches. Thereafter, the compression piston undergoes an upward or compressive stroke, compressing the mass or volume of air within the combined volume of the compression cylinder and the combustion chamber, until reaching a pressure of greater than thirty-five atmospheres and a volume of less than two cubic inches.
At this point with the compression piston at TDC, the combustion chamber is abruptly cut off from the compression cylinder. Accordingly, the volume of the compression cylinder decreases to below one cubic inch. The compression piston then begins its downward or expansion stroke and it can be seen that the pressure in the compression cylinder quickly drops at first and then more slowly until approaching a near vacuum at BDC. The cycle then repeats itself.
In the ideal cycle for the expansion cylinder, at BDC of the expansion piston, the volume in the expansion cylinder is just less than thirteen cubic inches. As the expansion cylinder begins its compressive stroke, the volume decreases rapidly and the pressure increases slowly at first. As the expansion piston approaches TDC, the pressure increases more rapidly until peaking at about forty-seven atmospheres in a volume of about two cubic inches. At this point, the combustion chamber opens to the expansion cylinder and there is a corresponding increase in volume and an increase in pressure due to constant volume heat addition which occurs within the combustion chamber before the blowdown port to the
expansion cylinder opens. For an initial period after TDC, the volume within the combined combustion chamber and expansion cylinder increases, while the pressure therein remains constant. This is a result of constant pressure heat addition. At a volume of about four cubic inches, the continued downward stroke of the expansion piston results in a decrease in pressure and an increase in volume. During the expansion stroke, work is extracted.
When the expansion piston reaches BDC, at just less than fourteen cubic inches, the combustion chamber is abruptly cut off from the expansion cylinder and there is a decrease in volume in the expansion cylinder. With the pressure being near atmospheric and the volume being just less than thirteen, the expansion cylinder repeats its cycle.
Referring now to Figure 2, the inner workings of the engine 10 are schematically illustrated therein. At a minimum, the engine 10 includes two cylinders, a compression cylinder 22 and an expansion cylinder 24. Crankshafts 26 and 28 are respectively connected by connecting rods 30 and 32 to the compression piston 34 and the expansion piston 36. Generally located toward the lower end of each cylinder 22 and 24, are induction ports 38 and 40. These induction ports become exposed or opened as the pistons 34 and 36 approach BDC, allowing for the induction of a fresh charge of air into the compression cylinder 24 and for the scavenging of the combustion bi-products and any residual mass from the expansion cylinder 24. To further facilitate scavenging in the expansion cylinder 24, the expansion cylinder 24 is further provided with exhaust ports 42. The exhaust ports 42 may be positioned to open before the opening of the induction ports 40.
Located generally centrally between the two upper ends of the compression and <BR> <BR> <BR> <BR> expansion cylinders 22 and 24 is a rotary prechamber tube 44. The tube 44 is rotatably mounted within the housing 14 and is supported therein for rotation about a tube axis 46 extending longitudinally through the tube 44 (seen as generally extending into the page of Figure 2). The tube 44 is generally cylindrical in shape, as seen in Figure 7, and further has defined within its body two prechambers or combustion chambers 48.
The combustion chambers 48 define generally outwardly concave bowls in the tube 44 and may further be defined by inserts 50 removably press-fit into cavities 52 formed in the tube 44. Such a construction allows for the removal of the inserts 50 and their replacement by another insert of different volume. Accordingly, the engine 10 of the present invention can be readily modified changing the volume of the combustion chambers 48 to vary the effective compression and expansion ratios of the engine 10.
Also defined generally centrally through the tube 44 is a passageway 54. Coolant fluid, such as oil, is circulated through this passageway 54 to not only cool the combustion chambers 48 but to also provide lubrication to the tube 44 itself and to seals which may be
provided in one or more axial and radial grooves 56. The oil for lubrication may be provided via centrifugal ducts, not shown, in the tube 44.
As the tube 44 is rotated, the combustion chambers 48 alternately communicate with the compression cylinder 22 and the expansion cylinder 24. Communication with the compression cylinder 22 occurs through an induction port 58 while communication with the expansion cylinder 24 occurs through a blowdown port 60.
As a chamber 48 is rotated between the compression cylinder 22 and the expansion cylinder 24, fuel is injected from a fuel injector 62 into the chamber.
Additionally, coolant passageways 64 are defined in the housing 14 and the engine block 12. These passageways 64 allow coolant, such as a water and glycol mix, to be circulated so as to cool the engine 10 overall.
Referring now to Figure 3b, several relationships of various features of the present invention are illustrated and defined therein. The bank angle, designated by arrow 66, is defined as the angle between the central axis of the compression cylinder 22 and the central axis of the expansion cylinder 24. Preferably, the bank angle 66 between the compression and expansion cylinders 22 and 24 will be in the range of 60 to 90 degrees. Such a range allows for use of the single tube 44 with both cylinders 22 and 24. The port angle is designated at 68 and is defined as the angle between a line drawn from the tube axis 46 through the center of the induction port 58 and a line drawn from the tube axis 46 through the center of the blowdown port 60. Preferably, the port angle 68 is within the range of 85 to 95 degrees for higher speed applications. Such a port angle allows for injection of fuel while the combustion chamber 48 is closed off from and between the cylinders 22 and 24 and initiation of combustion before the chamber 48 is ported to the expansion cylinder 24. The phase angle, designated at 70, is defined as the angle of advance of the expansion piston 36 relative to the compression piston 34 at TDC. Preferably, the phase angle 70 is within the range of 55 to 65 degrees, allowing a variance in the expansion cylinder's compression ratio. The bowl angle, seen in Figure 3b and designated as 72, is defined as the angle between a line drawn from the tube axis 46 and the leading edge 74 of the combustion chamber 48 and the line from the tube axis 46 and the trailing edge 76 of the combustion chamber 48. Preferably, the bowl angle 72 is within the range of 45 to 65 degrees. like the port angle 68, such an angle allows for injection of fuel while the combustion chamber 48 is closed off from and between the cylinders 22 and 24 and initiation of combustion before the chamber 48 is ported to the expansion cylinder 24.
During operation of the engine 10, at approximately 120° after TDC, the compression piston 34 has been retracted sufficiently to open the induction ports 38 allowing a fresh
charge of air, designated by arrows 78, to enter into the compression cylinder 22. At this point, it is seen that the scavenged combustion chamber 48 has not yet been brought into communication with the compression cylinder 22..
At approximately 120° before TDC, the compression piston 34 has been moved up sufficiently to close off the induction ports and the combustion chamber 48 is opened relative to the compression cylinder 22 via the induction port 58. As the compression piston 34 continues its upward stroke, see Figure 4b, the mass/volume within the compression cylinder 22 is compressed through the induction port 58 into the combustion chamber 48 as designated by arrow 80. At TDC of the compression piston 34, a minimal amount of head space exists within the compression cylinder 22. Slightly thereafter, the combustion chamber 48 is abruptly separated from the compression cylinder as generally seen in Figure 5a. The compression piston 34 thereafter begins its downward stroke or expansion stroke, as seen in Figure 4c, resulting in an increase of volume in the compression cylinder and a decrease in pressure (to a near vacuum). At that point, the compression piston has been retracted sufficiently so as to open the induction ports 38, again as seen in Figure 4a.
At this point, the compression piston 34 repeats the above described cycle except that the mass/volume within the compression cylinder 22 is compressed into the other of the two combustion chambers 48.
Immediately after being separated or isolated from the compression cylinder 22, see Figure 5a, fuel is injected via the fuel injector 62 into the combustion chamber 48. Initially, the fuel is injected directed onto a glow plug 82. During start-up operation of the engine 10, the glow plug functions to enhance the initiation of fixed volume combustion within the combustion chamber 48. However, after the engine 10 has been operating and has warmed up, temperature and pressure conditions within the combustion chamber 48 will be sufficient for auto-ignition to occur. Alternatively, a high compression ratio can be used for cold start and later reduced when the engine 10 is warm by changing the relative phasing between the pre-chamber tube 44 and compression cylinder 22.
To eliminate the need for flow plugs during cold start, a high start-up compression ratio with an effective lower operating compression ratio can be employed. By retarding the tube 44, the effective compression ratio of the warmed up engine is reduced thereby reducing peak pressures in the combustion chambers 48. The retarding or advancing of the tube 44 relative to the compression cylinder 22 can be achieved by biasing the tube's timing belt or chain 104. This is schematically illustrated in FIGS. 12 (a) and 12 (b) where the tube 44 is respectively advanced and retarded while being driven off of the expansion crankshaft 28 and FIGS. 13 (a) and 13 (b) where the tube 44 is respectively advanced and retarded
while being driven off of the compression crankshaft 26. Timing member 106 is alternatively biased into the belt 104 to effectuate retarding or advancing.
Also see in FIGS. 12 (a) and 12 (b) and 13 (a) and 13 (b), the compression and expansion crankshafts are timed off one another via belt/chain 108. The phasing of the cylinders relative to one another can likewise be varied, advanced as seen in FIGS. 12 (a) and 13 (a) or retarded as seen in FIGS. 12 (b) and 13 (b), through use of a similar timing member 110. Such variability allows the engine to be optimized under a variety of operating conditions as one skilled in the art will appreciate.
Because the tube 44 rotates about its central axis 46, and because of the fixed position of the fuel injector 62 in the engine block 12, fuel is not continuously sprayed into the same location 82. Rather, during the period of fuel injection, the fuel spray is progressively moved away from the leading edge of the combustion chamber 48 causing the injection spray to be swept across the combustion chamber 48, as seen in Figure 5b. By sweeping the injection spray across the combustion chamber 48, good fuel distribution is provided for in the combustion chamber 48, allowing for more complete mixing and combustion within the chamber 48. As a result of the ongoing combustion within the fixed volume of the combustion chamber, pressure within the combustion chamber 48 increases dramatically. In the ideal cycle, the pressure within the combustion chamber 48 prior to opening of the blowdown port 60 between the expansion cylinder 24 and the combustion chamber 48, pressure was determined to be approximately eighty-five atmospheres in a volume of less than one cubic inch. The state of the combustion chamber in the ideal cycle of Figure 9 is generally designated at 84.
In a preferred embodiment of the present invention, three fuel injectors 62 are utilized. Each injector 62 operates once every third injection, thereby allowing for high speed operation of the engine 10. The injectors 62 can be a single hole, low pressure component because of the relatively long constant volume injection and the turbulent flow field that is created as mass is transferred from the combustion chamber 48 to the expansion cylinder 24. Standard injectors and injection pumps can therefore be utilized with the present invention.
With combustion ongoing within the combustion chamber 48, the tube 44 rotates the combustion chamber 48 effectively opening the blowdown port 60 into the expansion cylinder 24. At this point in time, the expansion piston 36 is approaching TDC as seen in Figure 4c and, the compressed mass within the expansion cylinder 24 combines and mixes with the combusting and residual mass in the combustion chamber 48. The fresh influx of air and the mixing of the compressed mass in the expansion cylinder 24 with the combusting
and residual mass in the combustion chamber results in a secondary heat release as combustion efficiency of the engine is enhanced. The injection of the fuel into the combustion chamber 48, as described earlier, is done on a fuel rich basis. By injecting fuel rich, this enables the secondary heat release to occur after the start of blowdown through the blowdown port 60 and mixture with the freshly scavenged expansion cylinder. By providing for this secondary heat release, combustion efficiency is increased and NOX formation is reduced. Mixing of the combustion and residual mass from the combustion chamber 48 with the compressed mass in the expansion cylinder 24 is generally designated by arrow 86. Further compression of this mixture ensures that auto-ignition occurs as the piston reaches TDC.
To manage heat rejection during blowdown from the combustion chambers 48 through the blowdown port 60 and into the expansion cylinder 24, the blowdown port 60 is lined with a steel insert 100. The insert 100 is best illustrated in Figure 2. As the combustion chamber 48 continues to dump through the blowdown port 60 into the expansion cylinder 24, the expansion piston 36 begins its expansion or downward stroke with combustion continuing and work being extracted from the engine 10. The exhaust gases and any residual mass is subsequently exhausted through the exhaust port 42 as the final mass is dumped from the combustion chamber 48, respectively identified by arrows 88 and 90. Before the expansion piston 36 reaches BDC, the induction port 40 is opened and scavenging air, identified by arrow 92, is utilized to scavenge the combustion by-products and residual mass from the expansion cylinder 24. Scavenging of the expansion cylinder 24 is illustrated in Figure 4b. To ensure effective scavenging of the expansion cylinder 24, a positive pressure source of scavenging air is provided to the induction port 40. The positive pressure source of air can be provided through a number of techniques including, without limitation, utilization of a blower, supercharger or crankcase scavenging technique.
Continued advancement of the expansion piston during the compression stroke of the expansion cylinder 24 closes off both the scavenging port and the exhaust port 42 and the recharged mass within the expansion cylinder 24 is compressed. Thereafter, the second combustion chamber 48, having undergone its own cycle, is ported to the expansion cylinder 24 through the blowdown port 60. The expansion cylinder 24 thereafter repeats the above described cycle for the second combustion chamber 48..
Figures 6a through 6d respectively illustrate the geometric compression ratios for the compression cylinder 22 and the expansion cylinder 24. The geometric and effective compression ratios can be distinguished in that the effective compression ratios are defined based on piston positions at which all cylinder ports have just closed whereas geometric
compression ratios are based on the piston at bottom dead center. Furthermore, compression ratios versus expansion ratios are defined for each cylinder to incorporate the volume of the combustion chamber and its effect upon the compression ratios of both the compression cylinder 22 and the expansion cylinder 24. The compression ratio of the compressor and the expansion ratio of the expander both include the combustor volume while the expansion ratio of the compressor and the compression ratio of the expander do not.
In order to time the movements of the compression cylinder 22 with the movements of the expansion cylinder 24, a timing chain or belt can be provided to couple the crankshafts 26 and 28 of the cylinders 22 and 24. Furthermore, rotation of the tube 44 can be controlled through a similar timing chain or belt, coupled with either the crankshaft 26 of the compression cylinder or the crankshaft 28 of the expansion cylinder 24. The tube revolves at one-half of the crankshaft rotational speed.
The tube 44 is generally axially received within a cylindrical chamber 94 defined in the housing 14. The tube 44 is supported by bearings (not shown) which permit rotation of the tube 44 within the chamber 94 and relative to the housing 14. Since the tube 44 and the housing 14 will be subjected to extreme temperature conditions, to enhance heat rejection and structural integrity of the engine 10, a steel sleeve liner 96 may be provided to line the chamber 94. Furthermore, to isolate and seal the combustion chambers 48, preventing blowby of the combustion gases during combustion, the tube 44 must be provided with seals (not shown) extending circumferentially about the tube 44 on both ends of the combustion chambers 48, and axially along the tube 44, between the combustion chambers 48. To accommodate the seals, the tube 44 is formed with the radial and axial grooves 56 mentioned above. As will be appreciated by those skilled in the art, sealing can be effectuated in a variety of constructions.
After being shutdown from the expansion cylinder 24 and before being opened to the compression cylinder 22, the combustion chambers 48 are scavenged to remove residual mass from within the chambers 48. Scavenging of the combustion chambers 48 can be achieved by a variety of mechanisms including, but not limited to, crankcase scavenging or through use of a positive pressure scavenging system. In achieving scavenging, ports (not shown) are provided in the housing 14 and, where positive pressure scavenging is utilized, an upstream blower (also not shown) is used.
Simulations of an engine 10 as described above have demonstrated that an overall power density for this diesel engine can reach greater than 1.0. In a study of a supercharged, turbo-compound engine based upon the following design parameters, a power density of 1.78 horsepower/cubic inch was achieved. The design parameters were as follows: Parameter Compression Cylinder Expansion Cylinder Expansion phase angle 60° Cylinder bore 5.72 cm 7.54 cm Crankshaft stroke 4.83 cm 5.59 cm Connecting rod length 12. 12 cm 11. 68 cm Geometric expansion ratio 90. 16 12.50 Effective expansion ratio 76. 86 8.33 Geometric compression ratio 16. 5 17.52 Effective compression ratio 14. 19 11.53 Clearance volume 1.39 cc 15.12 cc Displaced volume 123.80 cc 249.78 cc
Tube/Combustion Chamber Parameters combustion chamber axial length 2.54 cm bowl angle 55° port angle 92. 770 bowl volume 6.60 cc Engine Performance Results volumetric efficiency 58.4% engine indicated power 84.4 hp engine brake power 78.3 hp overall brake power 81.0 hp In addition to providing an output from the engine 10 via the crankshaft 28 of the expansion cylinder 24, since the tube 44 is coupled either directly or indirectly to the crankshaft 28, it is possible to operate various devices off an output end 102 of the tube 44, which is provided to extend beyond and through the housing 14, at one-half of the engine speed. By way of illustration and not limitation, two devices or elements which could be operated off of the end 102 of the tube 44 include a water pump 104 (seen in Figure 1) for providing coolant to the housing 14 and engine block 12 and a propeller of an aircraft.
While the engine 10 has been illustrated as employing dual crankshafts 26 and 28, the engine 10 can readily be modified for use with a single, common crankshaft by varying the position of the compression and expansion cylinders 22 and 24 relative to the tube 44.
Where more than two cylinders (one compression cylinder and one expansion cylinder) are utilized, either a single crankshaft or dual crankshaft can be provided. Where dual crankshafts are provided, a single tube 44 can be utilized with inwardly opposed cylinders.
Where a single crankshaft is utilized, an outwardly opposed four cylinder engine can be provided. In such a configuration, two tubes, one for each pair of outwardly opposed cylinders, can be employed and timed directly off of the common crankshaft. A four cylinder, inwardly opposed, dual crankshaft, single tube design is schematically illustrated in Figure 10 while a four cylinder, outwardly opposed, single crankshaft, dual tube embodiment is schematically illustrated in Figure 11.
While the above description constitutes the preferred embodiment of the present invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.