DEVICE FOR THE INJECTION IN INTERNAL COMBUSTION ENGINES OF COMBUSTIBLE EMULSIONS WITH A READILY VARIABLE EMULSION RATIO

Abstract: Device for the injection in internal combustion engines of combustible emulsions with a readily variable ratio, constituted by a hydrocarbon phase and a component poorly miscible with it, which comprises a positive-­ displacement pump (10) driven by a portion of the delivery of the injection pump (1) fed with the hydrocarbon phase, said positive-displacement pump (10) carrying out the pumping of the other component of the emulsion; the two components of the emulsion are combined (9), (12) in the injector (8), which incorporates a static emulsifying device upstream the same injector.

Description: "DEVICE FOR THE INJECTION IN INFERNAL COMBUSTION ENGINES OF COMBUSTIBLE EMULSIONS WITH A READILY VARIABLE EMULSION RATIO" The present invention relates to a device for the injection of combustible emulsions in internal combustion engines, with a readily variable ratio between the emulsion components. From the art, the advantages are known, which derive from feeding the internal combustion engines with fuels constituted by emulsion combustible mixtures. Said emulsions are generally constituted by the hydrocarbon fuel, whether gasoline for the spark-plug-ignited engines, or gas oil for compression-ignition engines, and a polar compound poorly miscible with it, such as, e.g., water or methanol. Said polar compounds show very advantageous effects from an economic, energetic and environmental viewpoint, and make it possible to improve the combustion, to keep clean and efficient the engine, and to reduce the polluting emissions. For the purpose of fully exploiting such advantageous effects of the emulsion feeding, and limiting the disadvantages thereof, it is however necessary that the possibility be supplied of readily varying the ratio between the emulsion components, as a function of the revolution speed and of the load under which an internal combustion engine must usually operate, wherein such operating parameters, e.g., in the customary use on road vehicles, can vary within very wide limits. The present invention relates hence more particularly to the solution of the technical problem of the ready and efficacious regulation of the ratio between the hydrocarbon component and the polar component. It is disclosed hereunder with reference to a compression-ignited engine _ commonly denominated "Diesel engine" and to the gas oil/water emulsions, with the necessary warning that the invention is not limited to such a type of practical embodiment. Referring to the use in the Diesel engines, it is known that the adoption of a fuel constituted by a gas oil/water emulsion _ as long as such emulsion is endowed with the necessary characteristics of fineness and uniformity _ allows the smokiness and the amount of nitrogen oxides present in the exhaust gases to be very considerably reduced. That means a better combustion, and a higher efficiency of the engine, which remains clean and more efficient. That involves also the non-secondary advantage that the noxious and troublesome emissions are limited, in particular in town traffic. According to the prior art, such emulsions are generally prepared by an emulsifying device provided upstream the injection pump, viz., in the low-pressure branch of the engine feed system. The injection pump and the whole high-pressure branch of the fuel feed circuit are hence fed with the emulsion previously prepared upstream said injection pump. This type of technical solution engages with the emulsion the whole high-pressure branch of the fuel feed system, the ducts and the same injectors, which, in their whole, have a very large volume, as compared with the volume generated by a stroke of the reciprocating injection pump. As a consequence thereof, it is evident that the effect of changing the "emulsion ratio", viz., the water/fuel weight ratio, takes place after the time necessary for consuming all the emulsion already contained in the volume of the high-pressure branch of the feed system. As relates to the use on road vehicles _ in particular in town traffic _ such a delay, by being of the order of magnitude of one minute, is regarded as being too long and unacceptable. The reduction of the above said "noxious volume" is feasible only within such limits as imposed by the geometry of the engine, and does not make it possible to substantially reduce the above mentioned time. For exemplifying purposes, it is enough to consider, e.g., that the engine _ when the vehicle is not running _ should idle and be fed with gas oil only, in particular in case of long stops, and that on the contrary, when starting out again, when it must run under a high load, it should preferably be fed whith an emulsion containing the provided highest water level (approximately 15-25% by height). A further drawback is due to the fact that the water/gas oil emulsions can show problems of unstability over time. Representative of the prior art is FR-A-2 113 601, which discloses a fuel injection nozzle for injecting a mixture of fuel and water, formed upstream of the injection nozzles, into the combustion chambers of an internal combustion engine, and a transfer device consisting of a closed vessel having a moveable separator piston, one end of the vessel is connected to a fuel conduit in connection with a high-pressure pump and the injector nozzle, the other end of the vessel is connected to a water supply and via valves to said nozzle. Mixing of fuel and water takes place in the nozzle. US-A-4 481 921, DE-A-2 924 128, and the Abstract of JP-A-58 048 771 introduce water into an injector by a duct leading through the injector body to emulsification orifices. It is to be noted, however, that the above cited prior art disclosures do not pose, or solve, the problem of preparing a readily variable emulsion of a fuel with a fluid poorly miscible with it, and feed the engine sequentially, so that it is not possible, on the basis of their teachings, to regulate the weight ratio of the fuel to the poorly miscible fluid in a very short time, in the order of tenths of one second. In order to offset these deficiencies and drawbacks of the prior art, the present invention provides: A device for injecting into an internal-combustion engine a combustible emulsion of a readily variable ratio of a hydrocarbon fuel and of a fluid poorly miscible with the hydrocarbon fuel, comprising an injection pump assembly consisting of a pump and driving means therefor, delivering a stream of hydrocarbon fuel to an injector assembly incorporating a static emulsifier device operatively coupled to said injector assembly, branching conduits connected to said injection pump assembly for subdividing said hydrocarbon fuel stream into a first and a second substream, said first fuel substream feeding said injector assembly via a first modulating valve said second substream being connected to a hollow transfer device divided, by a sealtight moveable separation member responsive only and exclusively to the positive or the negative pressure differential generated by said pump into a first and a second chamber, said first chamber containing said second substream of hydrocarbon fuel and said second chamber containing the poorly miscible fluid delivered by a first poorly miscible fluid delivery means and by a two-ended second poorly miscible fluid delivery means connected at one end to said second chamber and at the other end, via a second modulating valve to said injector assembly. The device as defined above is preferably positioned immediately before each injector. The single Figure of the drawing diagrammatically shows a practical application to a Diesel engine. The injection pump 1 is driven by the mechanical drive means 2 and is fed with the gas oil from tank 3, with which it is connected by the feed line 4 and the return duct 5. The delivery of the pump 1 is sent to the fuel feed by means of the duct 6, which divides into two branches 6A and 6B. The duct 6A, throttled by the valve 7, feeds the injector 8 through the duct 9. The other branch 6B delivers the residual amount of fuel to a transfer device 10. The transfer device 10 _ which constitutes an important component of the device according to the invention _ is constituted by a closed vessel containing a moving separation member 11. Such separation member subdivides the volume comprised inside the vessel into two separate volumes, inside which the same pressure exists. It can be constituted by a flexible and elastic membrane, or by a bellows or a moving piston, or the like. The separation member 11, in the form of membranes or of bellows, can be made from flexible materials, such as natural or synthetic polymers chemically resistant to the components of the emulsion, metal foils, composite materials and the like; it must be properly supported and constrained inside the transfer device 10, but does not pose any constraints as to its shape. In case, on the contrary, that the separation member 11 is accomplished as a piston, the inner shape of the vessel is constrained to accurately match with the cross section of the piston sliding iniside it. Such piston can be made from rigid materials, such as metals, ceramic or rigid polymeric materials, such as fluorocarbons. The preferred shape is the cylindrical one, with its contact surface being precision-ground. The volume G adjacent to duct 6B is occupied by the gas oil, the other volume A is occupied, on the contrary, by the water to be emulsified into the gas oil. It appears evident that, at each delivery stroke of the pump 1, the gas oil transmits its pressure inside the transfer device 10, to volume A; as a consequence, water contained inside volume A _ due to the effect of the shift of the separation member 11, and in an amount corresponding to the volume displaced by it _ is delivered, by means of duct 12, throttled by the control valve 13, to the injector 8. On the contrary, at each return, or intake, stroke of pump 1, inside the transfer device 10, on G side, a suction is generated, which shifts towards the opposite direction the separation member 11 and draws water from the tank 14, through the line 15, and the nonreturn valve 16. If necessary in the line 15 an auxiliary water-feed pump 17 can be interposed, which supplies to the transfer device 10 a slight overpressure, which disengages the tank 14 from obliged positions. The injectors 8 of the engine must be provided with a mixing duct, and an emulsifier device 19 inside their interior. Such injectors can be accomplished by incorporating inside them, e.g., a static, jet-diffraction emulsifying device _ which, thanks to its small dimensions, is particularly suitable for the intended purpose _ upstream a normal-design injector. The water-gas oil mixing duct upstream the emulsifying device can be indifferently positioned inside or outside the injector 8, which will respectively have, in the two cases, separate inlet ports 9 and 12 for gas oil and water, or one inlet port only, for the mixture. The return from the injector 8 is conveyed through the duct 18 to the water feed pipe 15 upstream the nonreturn valve 16. Summarizing, the function of the device consists in feeding the injector 8 _ which incorporates the static emulsifying device _ with gas oil and water in their desired proportions: the first is directly delivered by the injection pump 1, and the second is pushed, on the contrary, by a portion of gas oil, which drives the transfer device 10 so to make it act as a positive-displacement pump. The relative amounts of gas oil and water are regulated, at each pump delivery stroke, by the valves 7 and 13. Either of said two valves _ e.g., valve 7 in Figure _ is adjusted in its position once for all, and has the purpose of generating a localized pressure drop inside the duct 6A, for securing the inflow into the volume G of the transfer device 10. In that case, the valve 7 can be replaced, e.g., by a calibrated nozzle, so calibrated for the purpose of maintaining said desired pressure drop. The regulation is entrusted to the other valve. Still referring to the example shown in Figure the other valve 13 is, on the contrary, modulated; its operation regulates _ by throttling the outflow into the duct 12 _ the emulsion ratio, viz., the gas oil/water weight ratio. It results evident that the regulation roles can be inverted between the two valves, and that the only valve which is really necessary is the regulation valve. The time of regulation of such ratio in outflow E results shorter than 1 second, and can reach values as short as 50-80 msec.

Claims: 1. A device for injecting into an internal-combustion engine a combustible emulsion of a readily variable ratio of a hydrocarbon fuel and of a fluid poorly miscible with the hydrocarbon fuel, comprising an injection pump assembly (1, 2) consisting of a pump (1) and driving means (2) therefor, delivering a stream of hydrocarbon fuel (6) to an injector assembly (8, 19) incorporating a static emulsifier device (19) operatively coupled to said injector assembly, branching conduits (6A, 6B) connected to said injection pump assembly for subdividing said hydrocarbon fuel stream into a first (6A) and a second (6B) substream, said first fuel substream (6A) feeding said injector assembly (8, 19) via a first modulating valve (7), said second substream (6B) being connected to a hollow transfer device (10, 11, G, A) divided, by a sealtight moveable separation member (11) responsive only and exclusively to the positive or the negative pressure differential generated by said pump (1), into a first (G) and a second (A) chamber, said first chamber containing said second substream of hydrocarbon fuel and said second chamber containing the poorly miscible fluid delivered by a first poorly miscible fluid delivery means (14, 15), and by a two-ended second poorly miscible fluid delivery means (15, 13), connected at one end (12) to said second chamber (A), and at the other end, via a second modulating valve (13), to said injector assembly (8, 19). 2. A device according to claim 1, wherein said sealtight moveable separation member (11) is a membrane. 3. A device according to claim 1, wherein said sealtight moveable separation member (11) is a bellows. 4. A device according to claim 1, wherein said sealtight moveable separation member is a piston. 5. A device according to claim 1, wherein said internal combustion engine is a compression-ignited engine, and wherein the hydrocarbon fuel is gas oil and the poorly miscible fluid is water. 6. A device according to claim 1, wherein said first modulating valve (7) modulates the weight ratio of the hydrocarbon fuel to the poorly miscible fluid and said second modulating valve (13) maintains a constant localized pressure drop. 7. A device according to claim 1, wherein said second modulating valve (13) modulates the weight ratio of the hydrocarbon fuel to the poorly miscible fluid and said first modulating valve (7) maintains a constant localized pressure drop. 8. A device according to claim 1, further comprising a nonreturn valve (16) incorporated into said first poorly miscible fluid delivery means (14, 15).

Inventors: CAPUTO, CARMELO
Applicants: AGIP PETROLI S.P.A.
Application year: 1988
Main classification: F02D19
IPC codes: F02D19, F02B47, F02M25, F02M43, F02F7, F02B13, F02B3