Patent Application
20100077987
Internal combustion engines contain multiple cylinders. Exhaust gas is generated when a fuel and air mixture is ignited and expanded within a cylinder to drive a piston. The exhaust gas is typically vented from the cylinders through an exhaust stroke to the atmosphere. The exhausted gas typically has a very high temperature when leaving the cylinders. In some proposed systems, the exhaust gas is delivered to a second cylinder for further expansion.
Some internal combustion engines have injected water into the same cylinder performing combustion with fuel and air intake.
There has also been a proposal for a combined engine that has a combustion cylinder mounted upstream of an expansion cylinder. The expansion cylinder receives hot exhaust gas from the combustion cylinder, and also receives a source of water that is expanded into steam by the hot exhaust gas to create further drive for a common crankshaft.
While this proposed system has good potential, there are many improvements that would make the system more practical.
In features of this invention, downstream expansion cylinders are associated with a combustion cylinder to provide an overall surface area and volumetric displacement of expansion cylinders sufficient to lower the temperature of fluids associated with the combined engine to such an extent that a radiator can be eliminated in an associated vehicle, or other system.
In a separate feature, a catalytic material is placed on surfaces which will “see” the hot exhaust gases such that catalytic conversion of impurities in the gases can be achieved within the engine itself.
In yet another feature, water is recovered from a system having both a water injection expansion cylinder, and a combustion cylinder, and the recovered water is re-used for the expansion.
In yet another feature, gearing is provided between an expansion cylinder and a combustion cylinder such that the output of the combined engine is optimized, and the two cylinders do not drive the crankshaft in a one-to-one fashion.
An engine 20 is illustrated in
The cylinders 32 and 34 are combustion cylinders and are shown having spark plugs 44. However, other combustion cylinders which do not require spark plugs would also benefit from the teachings of this application.
As shown, intake valves 40 control the flow of air and fuel into the cylinders 32, 34, in some engine types, such as Diesel, the fuel may be directly injected into the cylinders. The combined air and fuel is compressed, ignited, and exhausted through exhaust valves 42 into an associated exhaust line 46. The cylinders 32 and 34 may be four-stroke cylinders, and will operate as known, at least as described to this point.
Inlet valves 48 on the expansion cylinder 33 alternately operate in sync with the alternating operation of valves 42 and receive the hot, high pressure exhaust from the exhaust lines 46. The gases at least partially drive the larger displacement piston 50 associated with the expansion cylinder 33 in a two-stroke fashion. As known, the cylinders 32 and 34 will be out of phase by 360°. Cylinder 33 has a final exhaust valve not shown.
A water injection system 70 takes water from a source of water 71 and injects it into the engine at any one of several possible locations. As shown, the water may be injected through line 72 into the exhaust line 46. Water may be injected through line 74 to the top of the cylinder of the expansion cylinder 33. The water may be injected as shown at 76 into the top of cylinders 32, 34. If injected into the cylinders 32 and 34, it is preferred that the water be injected late in an exhaust cycle.
The water injection and metering can be performed in much the same way as high pressure fuel injection is commonly performed in a diesel engine, for example. The injection of water is estimated to be at a rate of 1 to 2 times the rate of fuel consumption for a gasoline engine. The water can be injected into the expansion cylinder 33 head at the time exhaust gases are being communicated to the expansion cylinder 33. Owing to a finite thermal absorption and vaporization delay for the heat of the ignition to vaporize the injected water, it may be beneficial in some cases to move the injection of the water forward in the process, into the exhaust passage 46, or into one of the cylinders as described above at 76. In the case of injecting the water into one of the combustion cylinders 32 or 34, this should occur at a mature point of the power-stroke, 160 degrees—175 degrees, past top dead center, for example.
Valves V are shown for controlling the flow of the injection of the water, and may be controlled by an overall engine control, in a manner that would be apparent to a worker of skill in this art.
While cam shafts are shown for controlling the operation of the several cylinder valves, other means of valve timing, such as electronic valve controls may be utilized.
Fuel and air fed combustion cylinders 32 and 34 may fire nominally at 0 degrees and 360 degrees of rotation respectively. The cylinders 32, 34 alternate intake and power strokes while the expansion cylinder 33 executes an exhaust stroke. During the exhaust stroke, gases exit the expansion cylinder through a valve, not shown. Each cylinder 32, 34 contributes torque to a crankshaft 52 through the power-stroke. The combustion cylinders 32, 34 alternate compression and exhaust strokes while the second cylinder 33 is executing a power stroke. In the power stroke, the piston 50 in the expansion cylinder is driven by expansion of the steam and exhaust gas. The expansion cylinder 33 expands the exhausted gas of the cylinder 32 beginning nominally at 180 degrees of rotation and then, after completing an exhaust stroke, the cylinder 33 alternately further expands the emission from the cylinder 34 beginning nominally at 540 degrees of rotation, in a two-stroke fashion.
In one example, displacement of the expansion cylinder 33 is four times that of the cylinders 32 or 34 (the displacements of the cylinder 32 and cylinder 34 may be nominally the same). Accordingly, the second cylinder 33 contributes significant positive torque to the crankshaft 52.
Oil pans 60 associated with the combustion cylinders 32 and 34 are shown. The sump 62 of the expansion cylinder may be sealed from the oil pans 60, and their combustion cylinders 32 and 34, such that water can collect, as will be described below.
In general, the use of the several expansion cylinders provides that the total surface area of expansion cylinders is sufficiently large that all, or the great majority, of the generated heat and energy can be recaptured prior to being exhausted to atmosphere. In this manner, the invention may allow the elimination of the radiator.
The pistons of the outer expansion cylinders 102 can have the same rotational phase as the four-stroke cylinders 132, respectively, and could be 180 degrees out of phase with the central two-stroke expansion cylinder 133. In this example, the need for ever larger displacement through a cascade is provided by having the combined displacement of the outer cylinders 102 be substantially greater than the displacement of the central cylinder 133, while the interior configuration may operate as previously described.
The example outer cylinders 102, may have bores that are larger than the central cylinder 133 by a factor of √{square root over (2)}, causing a combined displacement four times larger than the first cascade in the central cylinder 133.
In one example, two outer cylinders 102 receive the exhausted gas. In other examples, cascading continues from cylinder 133 to a single downstream cylinder. The direction and number of cylinders receiving the exhaust is not limited. It is desirable that each downstream, or cascaded, cylinder has larger displacement than the cylinder providing exhaust gases.
Water injection can occur through a water injection line 108 which is shown injecting water into the first stage expansion cylinder at 107, and the second stage expansion cylinders 102 at 106. As will be described below, the several stage cascading as disclosed in the
As seen in
The crankshafts of the two cylinders 202, 204 are mechanically synchronized in this embodiment through gear reduction 206, such that the 360 degree operation of cylinder 204 is effectively expanded to 720 degrees to match the operation of four-stroke cylinder 202. The example arrangement has the heavier reciprocating mass of the two-stroke, secondary power-stroke expansion cylinder 204 now reciprocating at half speed of the lighter, but faster, fuel and air fed four-stroke cylinder 202. The example arrangement has appreciable opportunity for additional thermal-to-mechanical energy extraction through a single cascade.
As shown in
The
Referring to
For each two-stroke expansion cylinder 502, there are four quarter-exhaust strokes and four quarter-power strokes for each one thousand fourteen hundred forty degree cycle, or two four-stroke cycles. The first two-stroke cylinder 502 is offset from the second two-stroke cylinder 502, such that when one is in an exhaust stroke, the other is in a power stroke. This allows the four-stroke 504 to feed one two-stroke at a time.
Again, a water supply source 535 may inject water through a line 537 into an exhaust line 19 connecting the single combustion cylinder 504 to each of the expansion cylinders 502. Of course, as with the earlier embodiments, any number of other locations for water injection may also be utilized.
Again, an oil pan 583 may be maintained separate from water sumps 579.
An embodiment 700 is illustrated in
The operation of the system may generally be as described above. Again, water injection is shown schematically through a source 710 into the expansion cylinder 702 and 704. Again, water pans 703 may be maintained separate from oil pan 701. However, here oil pan 701 services both combustion cylinders 706 and hot first expansion cylinders 704 while only the second, and final in this example, expansion cylinders 703 are cool enough to be serviced by water pans 703.
In other examples, N-two-stroke expansion cylinders can be coupled to M positioned four-stroke cylinders to create multiple cascades. Here, N and M are arbitrary numbers greater than or equal to 1.
In a similar example, one four-stroke cylinder could feed N-number of two-stroke, secondary-power-stroke expansion cylinders, where N is an arbitrary but generally even number. This creates an adaptable system configuration where the engine wastes little to no heat and the final exhaust temperature is brought to an exceptionally low value. Therefore, the only system energy exit is through the performance of mechanical work. This may allow the elimination of the radiator for an associated vehicle.
High-temperature, water-lubricated polymeric materials may be used in critical places within the construction of the second cascade, such as the outer cylinders 702. For example, the second cascade can have a dense, Teflon-like coating on the interior of the cylinder wall. The type of coating is not limited here. The connecting rod bearings similarly may use dense Teflon for bearing material, although similarly, not limited. The second cascade may be intentionally driven beyond the condensation point, such that water lubrication is available, as water condensation is captured within the engine for re-use. The heat loss by the final exhaust can be managed in this manner down to a negligible level.
The prior art systems typically lose heat to a radiator. The inventive systems attempt to minimize any heat to a radiator, and in fact to eliminate any need for a radiator, as will be explained below.
Prior systems lose heat to the exhaust. The inventive systems aim to reduce the temperature of the exhaust to such an extent that there will be little or no heat loss at this location. The same is true with heat loss to convection.
The main requirement for the cooling water jacket to cool the combustion cylinders, and then heat the expansion cylinders, is that the temperature of the cascade or expansion cylinders needs to be lower than the working temperature of the liquid coolant. This requirement can be facilitated by increasing the operating pressure, and therefore temperature, of the liquid coolant system. A temperature sensor 914 can be set such that it will send a signal to a control 916 to allow higher temperatures if such are desirable. While water may be used as the cooling fluid, any number of other coolants may be utilized.
The temperature sensor 914 may provide information back to the control 916 which controls the water valve 910 to ensure adequate water supply to maintain the temperatures as desired.
In addition, the control 916 may be an ignition control input which can control the timing of the ignition for the combustion cylinder 904. In a standard engine, it would not be desirable to slow ignition timing based upon undue temperatures in the system, as this will simply reduce the overall produced useful energy. However, given that the present invention captures a much greater percentage of the useful energy, slowing of ignition timing can be utilized while still capturing sufficient power through the subsequent cascades. Thus, the control 916 may be programmed with an algorithm that will identify an undesirably high temperature at the temperature sensor 914, and slow ignition timing. In this manner, the overall system can be more likely to capture a greater percentage of the useful energy created by combustion.
In general, the control 916 can modulate the ignition timing to achieve tight control over the temperature of the combustion cylinder. A sensed over-temperature condition can be rectified by retarding the ignition timing by one to twenty-five degrees of crank rotation, for example. The exact amount may depend on the size and abruptness of the overall temperature condition. This will transfer some of the heat load to the expansion cylinders, where it can contribute to useful work. This retardation of ignition timing will also reduce the peak temperature and pressure for the benefit of reduction of pollutant generation.
Any number of other ways of transferring heat from the combustion chambers to the expansion chambers may be incorporated into this invention.
With either of the
By capturing and transferring the heat in this manner, the system is able to reduce the exhaust gas and water from the most downstream cascade cylinder to such an extent that no radiator may be necessary.
The piston 933 is provided with piston seals 948 which may provide a loose seal with an internal surface 950 of the expansion cylinder 932. The amount of “clearance” is exaggerated in this Figure to show the fact of the clearance. The crankcase 946 for the expansion cylinder may be separated from oil such that the expansion cylinder components are lubricated only by this water. The water-containing crankcase may be similar to the case 62 in
The recovery of the water from the crankcase 946 may be only necessary on the most downstream expansion cylinder, however, it can optionally be utilized on more expansion cylinders than simply the most downstream. A water scrubber 939 is shown on the line leading from the crankcase 946, and may remove an exhaust gas 929, similar to the above-described embodiment.
The water scrubbers may be known water traps, and in particular may be chilled or cold water traps of known design. Further, the crankcase drain line can be combined into the exhaust line 938 such that a single set of water scrubbers may be utilized to achieve the above-described features.
By having this detailed water recovery system, the present invention ensures that the source of water will be largely recycled, and that an unduly large water tank will not be necessary.
Across the embodiments, expansion cylinders may be provided in sufficient numbers, such that the final exhaust may be brought to a low temperature, say below 500° F., and in a preferred embodiment, at or below 212° F. When surrounded with high levels of an external insulation, this low temperature exhaust becomes almost entirely the sole source of thermal efficiency loss in steady-state operation. The frictional “loss” of internal moving components also becomes captured within the system so as to be either converted as part of the useful mechanical output or to otherwise be a component of this modest final exhaust emission. These engines may achieve steady-state thermal-to-mechanical efficiencies that are in the range of 94-96%.
Steady-state operation may be characterized by the following rough thermal budget. In a current engine, say a radiator would account for 25% of the thermal budget, while in the described examples accounting for essentially 0%. In a current engine, conduction/convection might account for 25% of the thermal budget whereas in the described examples accounting could be approximately 1-2% of the thermal budget. In a current engine, exhaust may account for 25% of the thermal budget whereas in the described examples may account for approximately 2-3% of the thermal budget. Further, in a current engine, mechanical extraction may account for 25% of the thermal budget where as in the described examples might account for approximately 95% of the thermal budget.
It is believed that there could be back pressure due to the injection of the exhaust gas that could complicate the breathing induction of the combustion cylinders. By injecting water into a cascade cylinder head space after the exhaust gas communication is complete (as an example at the 50% cut-off point for a 2:1 crank synchronization; at the 25% cut-off point for a 4:1 crank synchronization, there will be less back pressure for the exhaust cycle to work into. As another example, should there be a 8:1 speed reduction on the cranks, the above can occur at the 12.5% cut-off point. This will improve the breathing of the combustion cylinder to improve power density, while still allowing the establishment of a steam vaporization pressure front.
Other ways of addressing this breathing concern can be utilized. As an example, the combustion four-stroke cylinder can be RAM charged or super-charged. The combustion cylinder can be of a particularly long stroke, as in a diesel cycle. The combustion cylinder can employ at Atkinson cycle, resulting in a very low cylinder pressure by the end of its power-stroke. The displacement ratio of the expansion cylinder to the combustion cylinder can be designed to be higher than described above. The combustion cylinder can be replaced with a split-cycle pair of cylinders, as has been proposed by Scuderi Motors. Water can be injected into the cascade cylinder head space after the exhaust communication is complete, as described above. Any of these methods of simplifying the breathing/back pressure issue can be utilized.
Referring to
In another example, different surface materials for internal environments become required as the final exhaust emission is likely to be much cooler than presently-in-use four-stroke engines, and possibly much lower than desirable for best catalytic reaction kinetics.
Generally, surfaces exposed to the hot gaseous fluid flow may have thermal insulation on the outside of the arrangement, or hot interior-surfaces and structural components may be made of thermally low conductive material. Another alternative would be to maximize heat loss prevention and use a low conductive material that is additionally thermally insulated on the outside. For example, the piston tops have substantial surface area exposed to hot gases, while their bottoms are exposed to crankcase oil. The heat-of-combustion to the displacement volume above the piston top may be confined for thermal-to-mechanical extraction and to avoid heating the crankcase oil. Therefore piston tops made of, for example, a thermally dead ceramic, or ones with a lightweight, crankcase-compatible insulation on the underside, or both, may be used. Another example would be pistons made of normal material, clad bonded with a thermally dead ceramic top surface. Similar concepts could be applied to the valves and valve tops, the hot gaseous-exposed interior-surface of the cylinder-head, the intake passages and exhaust passages from one cylinder to the next in the several above embodiments. This creates a continuous expansion motor with heat energy preserved through all the hot gaseous fluid flow and confined to mechanical energy extraction by the various, and now cascaded, power strokes.
Ultimately, water vapor condensation concerns may limit the minimum desirable final exhaust temperature, but only after a far greater thermal-to-mechanical extraction has been accomplished relative to currently-in-use internal combustions engines. Distilled water may be sufficient for the disclosed purpose, but tap water, or, tap water with a de-calcification/de-crystallization agent alone may also be sufficient. Further, the fuel can carry de-calcification/de-crystallization capability.
Many operating environments will be cold enough to freeze the water, causing a potential problem. However, this is likely manageable using, for example, flexible storage containers that can accommodate freeze expansion or similar technology. The final exhaust can also be used to melt the stored water over the longer operational term and a small high temperature thermal extraction channel from the 4-stroke cylinders can be used to melt water initially for the near term start-up. One other possibility is an electric melt device which is most cost-effective for initial, temporary use.
The combustion cylinder can be made up of, but not limited to, one or more of the following types of fuel and air cylinders including aspirated, fuel injected, carbureted, turbo-charged, super-charged, ram-charged, or any combination of these. The fuel can include, but is not limited to, the use of fuels including gasoline, diesel, propane, natural gas, alcohol, hydrogen, kerosene, or any other fuel known in the art.
In another example, the combustion cylinders may include an Otto four-stroke cylinder, Atkinson four-stroke cylinder, Diesel four-stroke cylinder, or any other known four-stroke cylinder.
While the expansion cylinders have generally been described as two-stroke cylinders, the invention would extend to four-stroke cylinder assemblies.
Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
The application claims priority to U.S. Provisional Application No. 61/173355, which was filed on Apr. 28, 2009, U.S. Provisional Application No. 61/166260, which was filed on Apr. 3, 2009, and U.S. Provisional Application No. 61/100295, which was filed on Sep. 26, 2008.
| Number | Date | Country | |
|---|---|---|---|
| 61173355 | Apr 2009 | US | |
| 61166260 | Apr 2009 | US | |
| 61100295 | Sep 2008 | US |
