APPARATUS AND METHOD FOR OXY-COMBUSTION OF FUELS IN INTERNAL COMBUSTION ENGINES

Abstract

A method and apparatus for the oxy-combustion of fuel in an internal combustion engine (ICE) used to power a vehicle includes one or more air separation devices that separate oxygen from the atmospheric air to mix with the fuel and return the nitrogen to the atmosphere and converts the free energy available in the form of waste heat from the engine exhaust gas stream and coolant system on board the vehicle into electrical and/or mechanical energy, which energy is used to separate oxygen from air to eliminate or significantly reduce the volume of nitrogen entering the ICE's combustion chamber, and thereby reduce NO.sub.x pollutants released into the atmosphere and increase the concentration of CO.sub.2 in the engine exhaust stream for capture using an integrated system to compress and increase the density of the captured CO.sub.2 for temporary on-board storage until it is discharged at a recovery station, e.g., during vehicle refueling.

Claims

1. An internal combustion engine (ICE) producing an exhaust gas stream having reduced nitrogen and NO.sub.x emissions from the combustion of a fuel with an oxygen-enriched atmospheric air stream from which nitrogen has been separated, the ICE having an engine block with a plurality of cylinders having walls forming combustion chambers and one or more channels in fluid communication with the cylinders for delivering the oxygen-enriched air for combustion of the fuel, the improvement comprising: one or more air separation devices integrated with the operation of the ICE and in fluid communication with the engine's air intake and the combustion chambers, the one or more air separation devices being adapted and configured to separate oxygen molecules from the atmospheric air to mix with the fuel and to return nitrogen molecules to the atmosphere, and wherein the channels are in the form of a manifold and one or more oxygen separation devices are positioned in the manifold.

2. The ICE of claim 1 in which there are a plurality of oxygen separation devices and the devices are positioned in series and the proportional oxygen content of the gas stream is greater downstream of each of the separation devices in the series.

3. The ICE of claim 1 in which the one or more air separation devices are membranes that provide fluid communication for oxygen molecules to pass from the air channels into the combustion chamber.

4. The ICE of claim 3 in which the membranes are ceramic membranes.

5. The ICE of claim 4 in which the membrane passes nitrogen and the retentate is the oxygen-enriched gas.

6. The ICE of claim 4 in which the ceramic membrane material is a perovskite type ceramic and releases retained oxygen in response to an increase in temperature.

7. The ICE of claim 6 in which the membranes are maintained at a temperature of about 800 F. by heat exchange with hot exhaust gases from the engine.

8. The ICE of claim 3 in which the membrane is a solid ceramic electrolyte with porous electrodes that are oxygen permeable and the solid electrolyte passes oxygen ions under an electrical potential.

9. The ICE of claim 1 in which a portion of the exhaust gas stream from the ICE is recycled and mixed with the intake air.

10. The ICE of claim 1 which includes a turbo-supercharger powered by the exhaust gas stream and in fluid communication with the atmospheric air to pressurize the air upstream of the one or more separation devices.

11. The ICE of claim 1 in which the one or more oxygen separation devices comprise two or more fixed beds containing an adsorbent material that releasably adsorbs oxygen from the air and passes the non-adsorbed gases for discharge into the atmosphere, each of the beds having an inlet for receiving an oxygen-depleted purge gas to release the adsorbed oxygen and an outlet in fluid communication with one or more of the plurality of cylinders for conveying the oxygen-enriched gas stream to mix with the fuel.

12. The ICE of claim 11 in which the purge gas is a portion of the hot exhaust gas from the ICE.

13. The ICE of claim 11 that operates in conjunction with an engine management system having a processor/controller operatively linked to at least one oxygen sensor located in the oxygen-depleted gas stream outlet of each of the two or more fixed beds, at least one valve associated with the inlet and outlet of each bed and controlled by the processor/controller in response to the amount of oxygen in the oxygen-depleted gas stream to divert air from one bed to at least one other bed and to admit the purge gas to release the adsorbed oxygen for discharge from the bed outlet as the oxygen-enriched stream.

14. The ICE of claim 1 in which the engine's air intake manifold includes a valve operable in response to the engine's performance to open and admit atmospheric air when the engine's requirements for oxygen cannot be met by oxygen passing through the one or more air separation devices.

15. The ICE of claim 1 in which the one or more air separation devices are pressure swing adsorption nitrogen generators.

16. The ICE of claim 1 in which the one or more air separation devices are vacuum swing adsorption systems.

17. The ICE of claim 1 in which the one or more air separation devices are hybrid vacuum-pressure swing adsorption systems.

18. The ICE of claim 1 in which the CO.sub.2 from the exhaust stream is captured and undergoes a densification process for temporary storage on board a vehicle powered by the ICE.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The invention will be described in further detail below and with reference to the attached drawings in which the same or similar elements are identified by the same number, and where:

[0049] FIG. 1 is schematic illustration of the energy balance of a typical hydrocarbon fueled internal combustion engine of the prior art;

[0050] FIG. 2 is a schematic illustration of an embodiment of the oxy-combustion process of the present invention in combination with a process for the capture of CO.sub.2 from the ICE exhaust stream and its densification for on-board storage;

[0051] FIG. 3 is a simplified partial cross-sectional elevation view of the cylinder of an in-line or I-block ICE with an embodiment of the invention positioned in the air intake manifold;

[0052] FIG. 4 is a simplified schematic illustration of an ICE and the embodiment corresponding to FIG. 3;

[0053] FIG. 5 is a simplified partial cross-sectional view similar to FIG. 3 that includes another embodiment of the invention in conjunction with the air intake valve; and

[0054] FIG. 6 is a simplified partial cross-sectional elevation view of the cylinder of an in-line or I-block engine that has been modified in accordance with another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0055] Referring now to the simplified illustration in FIG. 3 of a cross-section view of a portion of an ICE 10 representative of a four-stroke cycle. The engine block 20 includes an intake manifold 22 the flow of air being controlled by intake valve 24 and an exhaust manifold 26 closed by exhaust valve 28. Cylinder 30 contains piston 32 which is fitted with one or more piston rings 34.

[0056] In accordance with conventional four-stroke engine operations, the intake down stroke commences with the closing of the exhaust valve 28 and the opening of the intake valve 24 that is coordinated with the down stroke of piston 32 which draws the mixture of air and fuel into the open portion of cylinder 30 from the intake manifold 22. During the compression stroke, both valves 24 and 28 are closed and the fuel/air mixture is compressed as the piston 32 moves to the top of the cylinder, the spark plug or other ignition device 36 ignites the fuel/air mixture and a controlled combustion occurs which drives the piston to the bottom of the cylinder 30 in the power down stroke, causing the crankshaft 38 to turn and provide the propelling force to the vehicle through a transmission and drive train (not shown). During the exhaust up stroke, exhaust valve 28 is opened and the hot exhaust gases exit through exhaust manifold 26, and the cycle is repeated with the closing of the exhaust valve 28 and opening of the intake valve 24.

[0057] In accordance with an embodiment of the present invention, an air separation membrane 50 is positioned in the intake air manifold 22 to pass oxygen into the cylinder during the air intake down stroke. Nitrogen present in the intake air stream is maintained on the upstream side of the membrane 50 as the retentate gas and is discharged from the manifold into the atmosphere. Since no nitrogen is exposed to the high temperature and pressure oxidation conditions during combustion, no NO.sub.x compounds are produced and emitted with the exhaust gas.

[0058] In order to maintain a pressure differential across the membrane 50 and allow the retentate nitrogen and any other atmospheric gases that do not pass through the membrane 50 to be released back into the atmosphere, the air intake manifold includes an orifice downstream of the membrane that is sized and configured to maintain a back pressure, while at the same time permitting the nitrogen-enriched retentate stream to be released into the atmosphere. This arrangement is illustrated schematically in FIG. 4 where the discharge orifice 62 as illustrated, a supercharger, or a super-turbocharger powered by the mass of the exhaust gas stream, or other pressurizing device 60 that raises the pressure of the air supplied to the cylinders, directs pressurized atmospheric air via air manifold inlet 68 into air intake manifold 22 which is provided with an outlet to each of the cylinder intake ports of the four cylinders 30. The manifold 22 terminates in an orifice 62 positioned downstream of the last cylinder. In this simplified schematic illustration of one embodiment of the invention, fuel is delivered from tank 64 via fuel line 66 to fuel pump 67 and into cylinders 30.

[0059] As will be understood by one of ordinary skill in the art, additional elements from the prior art are required for the operation of the system which are omitted in the interest of clarity and understanding of the principal features of the present invention. For example, a plurality of fuel injection ports or nozzles can be utilized to more evenly distribute the fuel in the air intake manifold 22 and assure a more uniform mixture in response to changes in load, sudden acceleration or deceleration, and other changes in the operating conditions of the ICE. Although the invention is being illustrated with reference to an engine having an I-block configuration, most automobile engines on the market are equipped with V-blocks, which can contain from four, six, eight or even ten cylinders. Although the configuration of the air intake manifold corresponding to element 22 in the figures is more complex than the essentially straight air intake manifold used with an I-block engine, the general principles of operation of the air separation membranes described above apply. For example, the air intake manifold of each cylinder can be provided with a retentate orifice downstream of the membrane 50 (not shown).

[0060] It is also to be understood that the fuel is added to the oxygen downstream of the membrane 50 and an opportunity for adequate mixing of the fuel/oxygen-enriched air mixture must be provided. Additionally, membrane 50 comprises two or more fixed beds 40 containing an adsorbent material that releasably adsorbs oxygen from the air and passes the non-adsorbed gases for discharge to the atmosphere. In certain embodiments, oxygen sensors 70 can be located in the oxygen-depleted gas stream outlet of each of the two or more fixed beds 40. An engine management system 80 having a processor/controller is operatively linked to each of the oxygen sensors 70.

[0061] In an embodiment of the invention illustrated in FIG. 5, an air separation membrane 150 is incorporated into the inlet valve 124. Fuel is introduced directly into the cylinder 130 via direct fuel injection system 160, which is also known as gasoline direct injection or GDI. In the direct fuel injection system depicted, the fuel is highly pressurized and is introduced directly into the cylinder during the down stroke and it is mixed with the oxygen or air-enriched oxygen that has passed through the air separation membrane 150. The direct fuel injection, or GDI system enables a stratified fuel charge combustion, or ultra-lean burn, to improve fuel efficiency and reduce emission levels under low ICE loads. The valve assembly 124 containing the membrane 150 remains closed during the intake down stroke. During the compression stroke and the power stroke when the fuel is combusted, a fuel-tight cover 152 mounted on valve stem 125 is lowered to prevent loss of the fuel and air mixture and the pressure of the down stroke through the membrane. As will be apparent to one of ordinary skill in the art, this arrangement will require some modification of the valve stem and the associated operating mechanism. A further advantage of the adaptation of the invention to this embodiment is that fewer modifications are required to the structure and mode of operation of a direct fuel injection system.

[0062] In an alternative of this embodiment, the valve assembly 124 containing the air separation membrane 150 remains closed for all or a portion of the intake down stroke and is open for a portion in order to admit a volume of atmospheric air that is required to support combustion. In another alternative embodiment, the cylinder head is provided with at least one additional air intake manifold port and intake valve that admits atmospheric oxygen directly and a second port that admits oxygen that has passed through the air separation membrane 150 as described above in connection with FIG. 5 or through a membrane 50 as previously described in connection with FIG. 3

[0063] Referring now to FIG. 6 an embodiment will be described in which one or more air separation membranes 250 that pass oxygen are integrated into the wall of all or a selected number of the cylinders 230 in a modified ICE 210. As shown in this cross-sectional view, air separation membranes 250 are positioned in the cylinder walls 230 and are supplied with atmospheric air passing through manifolds, or atmospheric air delivery channels 222. The air delivery channels can surround the periphery of the cylinder in order to increase the surface area of membranes serving each cylinder. A sufficient number of membranes 250 are provided to meet the oxygen requirements for complete combustion of the fuel in the cylinder under the range of operating specifications of the ICE. As a result, the intake valve assembly and air intake manifold inlet to the cylinder are eliminated, thus simplifying the construction of the engine. As in the earlier embodiments, the retentate nitrogen and any other atmospheric gases are released to the atmosphere via one or more orifices which allow for the flow of fresh atmospheric air to the membranes.

[0064] In order to prevent the reverse flow of gases and fuel during the compression stroke and the passage of hot combustion gases during the compression stroke, power stroke and exhaust stroke, a membrane cover can be provided to isolate the oxygen-passing membranes from the compressed gases in the cylinder. As will be understood by one of ordinary skill in the art, the engine block and cylinder walls are modified to provide for the installation of the membranes 250 and to provide communicating internal manifolds or air channels 222 for the introduction of pressurized atmospheric air.

[0065] In order to inhibit the reverse flow of gases from the combustion chamber during the compression and power strokes, a membrane material is utilized that restricts or impedes the flow of nitrogen, NO.sub.x and CO.sub.2. In the case of a solid ceramic electrolyte, the current is interrupted to discontinue the ion transport through the electrolyte.

[0066] In an alternative embodiment, an additional valve is provided in the cylinder head to admit atmospheric air in order to meet oxygen requirements associated with rapid acceleration, increased loads and the like. In the event that atmospheric air is admitted to the cylinder to support the complete combustion of the fuel, some NO.sub.x compounds will be produced and emitted in the exhaust gases. The same valve, or an additional valve in the cylinder head, can be utilized to recirculate hot exhaust gases in order to control the combustion temperature and therefore the heat transferred to the engine block and its associated components.

[0067] The O.sub.2 separation unit or membrane can be adapted for use in different types of internal combustion engines and propulsion systems. For example, the invention can be used with 4-stroke, 2-stroke, 6-stroke, Wankle, Atkinson, Stirling, gnome, gas turbine, jet, wave disc, and other types driven by the combustion of any type of hydrocarbon fuel.

[0068] Since pure or nearly pure O.sub.2 is combusted with the fuel, the resulting combustion product will constitute principally CO.sub.2 and H.sub.2O. The water can readily be condensed and separated to provide a pure, or nearly pure CO.sub.2 stream for densification and storage. In addition, the elimination or reduction of nitrogen oxide products (NO.sub.x), unburned hydrocarbons, carbon monoxide and other by-products eliminate or reduce the need for the catalytic converter or other on-board exhaust gas stream treatment systems.

[0069] While the foregoing desorption and the attached drawings are representative of various embodiments and examples of the invention, additional embodiments will be apparent to those of ordinary skill in the art and the scope of protection for the invention is to be determined by the claims that follow.