CZ20002238A3 - Water and fuel above-critical composition and fuel system - Google Patents

Abstract

The fabric composition comprises a mixture of 5 to 50% water and hydrocarbon. At 400 ° C and 4,000 psi (ie 27.58 MPa) is its emulsified phase near or above critical point. The fuel system can be a water source and hydrocarbon fuel that is connected via high pressure a metering pump (34) into the electrically operated valve injectors (10) and combustion, compression, combustion chambers or gas turbine engines (40) of the power plant.

Description

Technical field

The present invention relates to a combustion system, and more particularly to a combustion system utilizing a supercritical composition of water and fuel.

BACKGROUND OF THE INVENTION

Recently adopted legislation on air quality has focused on fossil fuel emissions. These laws require that both engine manufacturers and fuel suppliers look for solutions that will enable them to continue selling their products. Refineries must seek alternative formulations of substances and / or mixtures to reduce such emissions. On the other hand, engine designers have to reassess the entire combustion process and how the combustion process is carried out from start to finish.

Engine manufacturers are increasingly demanding in terms of tolerances - wall machining to reduce engine oil combustion. In addition, they use increasingly high injection pressures. Higher pressures result in better spray fuel entry into the combustion zone, as well as achieving finer droplet sizes. Higher pressures allow smaller holes to be applied to the injector tips while maintaining the same mass flow ratio.

With newly developed injection molding machines operating up to 30,000 psi, the droplet size decreases, but droplet sizes are still in the range of 1 to 10 microns. Decreasing the droplet size by a factor of two would necessarily be accompanied by an increase in the number of droplets by a factor of eight in terms of perspective mass balance. This is important because a large number of small droplets improve microscopic homogeneity and reduce the formation of particulate matter. Unfortunately, droplet size reduction at these extreme pressures is less than a factor of two compared to standard 3,800 psi (26.2 MPa) systems.

By way of example, a droplet having a diameter of 2 microns occupies 3 x 10 -1 ¹² cm ³ and one mole of diesel fuel occupies 300 cm ³ . Therefore, a droplet of such size still contains 10 ^w moles of fuel molecules or 6 x 10 6 molecules. It is clear that even these smaller droplets still present some challenge for perfect evaporation and

-2burn. Therefore, another mechanism must be found that goes beyond the above mentioned pressure increase.

It is well known in the art that droplet size is primarily related to the surface tension of the fluid. Therefore, any process that reduces surface tension can potentially reduce droplet size. In surface technology, a chemical approach to reducing droplet size can be found. Additives may be used to reduce the surface tension, but their applicability is limited by high costs. It is therefore clear that there is a need to develop additional chemical approaches.

It is well known in the art that additional heating of a hydrocarbon fuel reduces its surface tension. In this sense, fuel pre-heating has some prospective effect on both emissions and fuel economy. However, heating leads in practice to the premature transformation of fuel into higher compounds as well as lower molecular weight compounds. The fuel viscosity increases at a rate that surpasses the decrease in surface tension, creating adherent tar deposits. Therefore, simple preheating of hydrocarbon fuels has limited usability.

However, there are impurities which may represent an alternative to this tendency to increase the molecular weight by heating. For example, water supports the reverse process in which the molecular weight of the hydrocarbon fuel is reduced by partial conversion of the H ₂ and CO gases and shortening of the chain length. Therefore, mixing water and fuel together and heating offer an economical solution to reduce droplet size. Additionally reformulated H ₂ improves cetane that has a wider flammable range. The H ₂ gas is of limited usable quality because the wider flammability ranges allow ignition at low oxygen concentrations. Thus, these H ₂ molecules serve as efficient combustion initiators that distribute well in the reaction zone.

Adding water to heated fuels offers useful advantages, but mixing water and hydrocarbons is not easy. The polar nature of the water and the non-polar nature of the fuels help phase separation into two unmounted pure liquids. Water does not interact with fuels. It simply overcomes the strong attraction of other water molecules, making it impossible to bond with hydrocarbon units. This phase separation property can be improved by the addition of surfactants and mixtures thereof, but, as already mentioned, these are expensive matters.

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SUMMARY OF THE INVENTION

In one aspect, the present invention is a composite material comprising a mixture of 5 to 70% water and hydrocarbon, and preferably 5 to 50% water and hydrocarbon, and more preferably 20 to 40% water for use in engines in which the water and hydrocarbon mixture is near or above a critical point so that the mixture is uniform, a single phase. Lower amounts of water are preferred for engines and higher amounts of water are preferred for burners and burners. The composition is in the temperature range of 350 to 500 ° C and preferably in the range of 350 to 400 ° C at a pressure in the range of 3,000 to 6,000 psi (ie, from 20,685 MPa to 41,37 MPa) and preferably from 3,000 to 6,000 psi. 4000 psi (i.e., from 20.685 MPa to 27.58 MPa). According to another feature, the present invention is a fuel system having a structure comprising a mixture of water and a hydrocarbon near or above a critical roll such that the mixture is in a uniform, single phase. Said structure is adapted to deliver a mixture for combustion. The combustion may be carried out in an internal combustion engine, turbine engine or other burner. In one embodiment, an injector is provided to deliver the mixture to the internal combustion engine, both by the spark of the spark-ignition engine and to the diesel-type diesel engine. Advantageously, the injector is actuated electrically by means of a magnetically actuated armature which is adapted to open the injection port based on the adjusted crankshaft angle.

In order to keep the water / fuel mixture close to its critical point, the mixture is maintained at a temperature of about 400 ° C and a pressure of about 4,000 psi (27.58 MPa). The high pressure preferably produces a two-piston metering pump, and the injector is preferably maintained at 400 ° C using a heating pipe to supply heat from the engine exhaust pipe system. There is also the possibility of using additional electric heaters.

Since the water-hydrocarbon fuel mixture is maintained in a homogeneous, isotropic, single phase, it will be completely combusted upon introduction into the fuel chamber. More complete combustion takes place because liquid droplets are eliminated. Improved combustion reduces the formation of particulate material. The uniform dispersion of fuel molecules in the air results in lower emissions of nitrogen oxide and nitrogen oxides are further reduced due to insufficient catalysis of reaction pathways on droplet surfaces. A faster, more complete combustion cycle also reduces emissions of carbon monoxide, unburnt hydrocarbons and volatile organic and polyaromatic hydrocarbons.

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Overview of the drawings

An embodiment of the present invention will now be described with reference to the accompanying drawings, in which:

Fig. 1 is a cross-sectional view of an injector according to the present invention;

Fig. 2 is a schematic representation of a system for combusting a supercritical water-fuel mixture.

DETAILED DESCRIPTION OF THE INVENTION

As mentioned above, water added to heated fuels offers combustion benefits, but the formation of a mixture of water and hydrocarbons is not easy. The most efficient way of forming a mixture of these two insoluble liquids utilizes the effect of high pressures and temperatures. Sufficiently high pressures and temperatures of supercritical conditions promote solvation and at the same time prevent tar formation. Supercriticity is defined as the point at which the heat of evaporation becomes zero. After dissolution, the supercritical mixture has optimal combustion properties.

The supercritical phase is a dense gas that is partially shifted to convert some of the reactants into H ₂ and CO gases. These gases, together with the hydrocarbons themselves, exit the supercritical injector without passing through the liquid phase. The concept of droplet dispersion itself is eliminated from the reaction pathways. If the cylinders are large and the supercritical gas stream does not penetrate to the desired distance from the injector, the temperature may decrease by a few degrees to the point where the high density subcritical fluid is ejected. The current then flashes rapidly upon entering the cylinder. Incorporated water molecules and water clusters create catalytic surfaces for heterogeneous reactions. H ₂ gases are easier to ignite and the delay time of ignition is shorter. Accordingly, supercritical mixing increases the "effective cetane number" of the fuel mixture.

The cetane value of diesel fuel is a parameter used to measure the fuel flammability. It is the exact opposite of octane in gasoline. In the case of spark-ignited combustion, premature ignition is undesirable and therefore fuels are used which are less easy to ignite. The higher the octane number, the higher the compression ratio that supports the increase in output power can be applied.

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On the other hand, diesel engines rely on automatic fuel ignition based on the interaction of the fuel and the heated air supplied. The air is heated adiabatically during the compression stroke above 700 ° C and fuel is injected near the top dead center. Combustion follows at a ratio that follows the cetane number of the fuel. Fuels with a higher cetane number ignite earlier and develop more power at a favorable specific fuel consumption.

Of course, supercritical mixing of diesel fuels and water changes the cetane number. Water not only dissolves fuel molecules, but also converts some fractions to CO and H ₂ based on the water shift reaction. In general, supercritical mixtures of hydrocarbons and water are subject to some extent to pyrolysis, hydrolysis, steam reforming, water gas conversion reactions, methanation and hydrogenation.

Increasing the cetane number shortens the ignition delay and increases the burning time. The temporary development of pressure-to-volume characteristics may be quite different, since the necessarily mixed water may accelerate the reaction together with the new components. Reducing the ignition delay means that ignition of the fuel may be delayed, assuming higher power levels.

Supercritical combustion is not expected to involve reactions on the surface of the liquid droplet. Completely eliminating the surface tension, these conditions make it impossible to form droplets at air temperatures near the injector that generally exceed 800 ° C. Without the formation of droplets, the entire essence of the combustion process changes. As a result, local occurrences of NO are eliminated because there is no reaction that targets the surface of the droplets.

Droplet removal is also expected to eliminate the formation of nucleation centers for forming particulate materials, thereby preventing the formation of carbon black. This second benefit further reduces the malfunctioning of the lubricating oils, since the soot is no longer present in the thin layers of oil on the cylinder walls. Reducing soot production can therefore be expected to reduce maintenance costs and reduce downtime for high-performance diesel engines.

The very high density of the individual molecules in the supercritical fluid offers a convenient reaction that improves properties. These properties directly relate to improved transport of the reactants, since the dilution coefficient of the dense gas is a quantity that is on the order of magnitude greater than in the liquid state. Changes in reaction rates and by-product of the reaction obtained in the vicinity

Thus, the -6-critical point of the blends and fuel can be achieved at higher lych speeds and even with the participation of different reactants.

Differences in transport properties were observed which differed from 3 to 4 orders of magnitude close to T ^ t. The formation of certain by-products is advantageous above the critical temperature on the basis of pressure increments, while such liquid-forming reactions have limited reaction rates. Reaction rates do not increase significantly as thermophysical greases are improved. Naturally different reactants begin to compete and shift product concentration profiles. Under normal circumstances, increasing the pressure of the gaseous system does not affect chemical grease. Ideal gases remain ideal as pressure increases. Van der Waals gases maintain a slight interaction. However, critical fluids have detailed richness that can only be explained by removing local binding interactions.

Attempts

The water / diesel mixtures are poured into an airtight, high pressure chamber and heated at a heating rate of 2 ° C per minute. The water has a density of about 1 gram / cm ³ below a critical temperature of 374 ° C with a critical pressure of about 3,250 psi (i.e., about 22.4 MPa). The diesel fuel contains components with a wide molecular weight range and as such does not have a well-established critical temperature.

In a first attempt was made constant pressure 2000 psi (i.e. 13.79 MPa), and the mixture was heated under _Tc of water to 400 ° C. At 2000 psi and 400 ° C, the tico is too low and the temperature too high to keep the water in a liquid state. Dense gas was formed on the still liquid diesel fuel and no complete mixing was observed.

The fact that the diesel fuel maintains its liquid grease at 400 ° C is indicative of its supercritical temperature. Adding more thermal energy to the motor oil without water would break many bonds before converting to a combination of dense gas and heavy deposits.

In a second experiment, a pressure of 3000 psi was maintained while the mixture was heated at a heating rate of 2 ° C per minute. Surprisingly, at 363 ° C, both fluids were completely mixed to form a supercritical fluid. It is important to note that this phase change manifested itself under supercritical conditions of both water and diesel as separate fluids.

The second experiment showed that the role of pressure was decisive in relation to reaction chemistry.

The water solubility increases in magnitudes of magnitude over a specific pressure and temperature range.

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A third attempt was made to verify the features of this pressure parameter on the nature of supercritical chemistry. The pressure was increased to 4000 psi (27.58 MPa) and the temperature in the reaction vessel was increased again at a heating rate of 2 ° C per minute. In this case, the temperature of both supercritically stirred liquids was raised to 378 ° C. The supercritical stirring temperature increased from 363 ° C to 378 ° C due to a pressure increase of 1000 psi. This contraintuitive trend proves that there is an optimum pressure and temperature point for a given water / fuel mixture and this phase stability relationship is the subject of ongoing research.

These experiments demonstrate that a diesel fuel injection system operating at 4000 psi and 400 ° C will provide significant benefits. One advantage is that a higher temperature will reduce the ignition delay and feed the heat content into the combustion process. Expansion of the supercritical fuel mixture into the heated air in the cylinder ensures better mixing and combustion at the molecular level and eliminates the time that is otherwise required for droplet evaporation. The use of exhaust heat to achieve desired temperatures creates thermodynamic regeneration, which adds several percent to engine cycle performance along with associated emission improvements as a result of faster, more complete combustion.

The observation of supercritical mixing in combination with other measures showing the beneficial effect of water on combustion characteristics offers certain strategies for better combustion of hydrocarbon fuels. Without limitation, these fuels include gasoline, diesel fuel, heavy distillates, heavy fuel oil (bunker C), kerosene, natural gas, oil, asphalt, or some other carbon-containing material such as biomass. All of these hydrocarbon aggregates can be improved by mixing with water under or near supercritical conditions. Accordingly, there is the possibility of implementing new refining processes for fuel reformulation based on careful management of pressure, temperature and water content.

Fuel injection systems in high-speed internal combustion engines inject fluids at high pressure in rapid succession, and each such injection must be performed within a very short period of time. The injection periods take place in the order of one millisecond and the amount of fuel injected is measured according to different schemes. In fact, all these pressure pulse systems rely on liquid phase incompressibility. Very small movements are required to make small volumetric changes in the dense liquid phase. In addition, the pressure pulses are

8 in the case of liquids at the speed of sound in the liquid phase, which generally represents more than

000 meters per second.

These small volumetric changes are generally made by means of physical means in which the camshaft guides the piston in the rocker so as to increase the pressure in the enclosure. The pressure increase depends on the very tight clearances of the sliding components, which prevent leakage of fluid by their precise sliding fit.

Moreover, in fact, the outer sealing components of all injection systems contain carbon materials such as viton, buna N, teflon, plastic and the like. None of these materials can withstand the temperature expected to supercritically inject a water / fuel mixture. Therefore, there is a need for special motion control means without the need for sliding seals or tight clearances.

The supercritical mixture will not exhibit the same transfer of pressure properties as the liquid. It is more compressible in order of magnitude. As a result, alternative strategies are needed to control the injected dose of fluid. This dosing is further complicated by the fact that sliding seals have to seal gas rather than liquid. Thus, leakage is a very serious problem with supercritical fluid.

Referring to Fig. 1, the injector 10 bypasses the problem of sealing at high temperatures by jointly eliminating the seal. The injector 10 comprises an airtight housing 12 in which a magnetically actuated needle valve assembly 14 is disposed. A useful material for making the housing 12 is stainless steel "174PH" and the housing 12 is closed with a magnetic steel lid 16 which is screwed on top of the housing 12 and is sealed with a copper seal (not shown). The magnetically actuated needle valve assembly 14 comprises a magnetic steel anchor 18 having a square shape with rounded corners that are flush with the inner diameter of the kiytu 12. The lower end of the assembly 14 includes a pin valve 20 that normally closes the injector tip opening 2. The pin 20 extends from the end of the injection assembly 10 on which a small thread is formed and enters the injector nozzle where it is held by the spring 24. The spring 24 keeps the pin 20 in contact with the bore 22 when the injector 10 is closed. A two-layer solenoid with approximately 130 turns of the magnetic wire 26 of the magnetic assembly 14 is wound around the top of the injector 10. The magnetic wire 26 is insulated with a ceramic fiber designated "3M Nextel". The top of the magnetic wire winding 25 is approximately 5 inches (12.7 cm) long.

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The magnetic steel lid 16 is screwed onto the structure such that a gap of approximately 0.030 inch (i.e. approximately 0.762 mm) remains between the armature 18 and the lid assembly 16.

The injection assembly 10 is controlled by a pulse width modulated 50 amp pulse, the timing of which is adjusted, for example, in relation to the engine crankshaft. The timing and pulse width may be varied to provide control of the start of the injection and the length of the injection period. For corrosion protection, all magnetic steel parts are protected by electroless nickel plating with a coating thickness of 300 to 600 microns (i.e., 0.762 to 1.52 microns), which is carried out in a manner well known in the art of plating.

Giant. 2 is a schematic representation of one embodiment of the present invention using the injector 10 shown in FIG. 1. The fuel inlet 30 and the water inlet 32 are connected to a two-piston metering pump 34 that supplies water and fuel to the inlet port 35 of the injector 10. water and fuel at a high pressure of about 4000 psi (27.58 MPa). The heater jacket 36, which may be powered or heated by a heat supply pipe (not shown) from the engine exhaust manifold, heats the injector to a temperature of about 400 ° C. The injector tip 10 is adapted to inject a homogeneous fuel-water mixture into the combustion chamber 48 of the engine 40. The power source 42 serves to power the helix 26 and its timing is adjusted with respect to the crankshaft 44 of the engine 40 to control fuel delivery. The temperature adjuster 46 maintains the operating temperature of the injector 10 such that the fluid therein is maintained at or near supercritical conditions.

Combining a more efficient dissolution force of supercritical water together with better transition properties of the dense gas are needed for a prospective chemical reaction. Elevated temperatures support reformulation chemistry, but reaction rates are always limited by species diffusion coefficient k from the homogeneous catalytic surface. The diffusion coefficient of dense, supercritical gas is 3 to 4 orders of magnitude higher than that of a typical liquid. Accordingly, the high gas density at these supercritical pressures maintains the density at nearly 60% of the density of the fluid state, so that the resulting power can remain high.

Supercritical reaction chemistry is particularly valuable in fractionation columns because the solubility of species is a significant function of temperature and pressure. In general, supercritical fluids exhibit solubilities that are completely unlikely under subcritical conditions. For example, salts that are highly soluble in hot water become insoluble

-10When the critical temperature level is exceeded and eliminated. In contrast, insoluble materials such as hydrocarbons dissolve more easily when a certain critical temperature and pressure is exceeded.

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Industrial applicability

The presented technology has application for both mobile and stationary devices. For example, the fuel injection system of the present invention may be used in a combustion chamber of a gas turbine or jet engine that is used in aircraft, ship, automobile or stationary power equipment. The result of using exhaust from the exhaust system to heat the injector is a heat recovery cycle that dissipates the usable energy from the exhaust system and provides additional enthalpy to the combustion cycle near the peak of the compression stroke. This technology can also be used to process heavy distilled fuels such that different molecular weights are optionally extracted in accordance with pressure and temperature gradients within the supercritical reaction vessel. This technology is also applicable to flammable muds with a higher molecular weight than kerosene and diesel fuels due to the high solubility of supercritical water. In another embodiment, the natural gas can be converted into a supercritical and reformed mixture such that the mixture becomes a hypergolic mixture and spontaneously ignites in the compression engine without the need for controlled injection of the second fuel.

In another embodiment, the fuel injection system of the invention uses a flexible membrane that forms a bellows structure to seal the mixture at high pressure and temperature. The cam controls the movement of the valve that performs its action through the resilient diaphragm.

Claims (22)

PATENT CLAIMS A fabric composition comprising a mixture of 5 to 70% water and hydrocarbon, characterized in that the mixture of water and hydrocarbon is near the critical point, such that the mixture is in a uniform, single phase. The fabric composition of claim 1, wherein the mixture has a temperature of 363 ° C and a pressure above 3,000 psi. The fabric composition of claim 1, wherein the temperature of the mixture is in the range of 363 ° C to 400 ° C and the pressure is in the range of 3000 psi to 4000 psi (ie, from 20,685 MPa to 27,58 MPa) . 4. The composition of matter of claim 1 wherein the hydrocarbon is a hydrocarbon fuel. 5. A fuel system comprising a structure comprising a mixture of water and a hydrocarbon fuel, the mixture being near a critical point such that said mixture is in a uniform, single phase and further comprising means for supplying the mixture to a combustion plant. chambers. 6. The fuel system of claim 5, wherein the structure that comprises said mixture has an injector, including a valve for delivering the mixture to the combustion chamber. 7. The fuel system of claim 6, further comprising a high pressure metering pump for supplying water and hydrocarbon fuel to the injector. 8. The fuel system of claim 6 wherein the injector is actuated electrically to deliver fuel to the combustion chamber. φφ φ φφ φ -129. The fuel system of claim 8, wherein the combustion chamber is an engine combustion chamber having a crankshaft and the electrical actuator of the ejector responds to the crankshaft angle. • Φ φ φ · φ φ φ φ φ φ • φ φ φφ 10. The fuel system of claim 9 wherein said engine is a diesel diesel engine. 11. The fuel system of claim 9, wherein said engine is a spark ignition engine. 12. The fuel system of claim 9 wherein said engine is a gas turbine engine. 13. The fuel system of claim 9, wherein the electrical injectors are operated by pulse width modulation. 14. The fuel system of claim 11, wherein the fuel injector opens into the intake port or throttle body of the spark ignition engine, and the fuel is gasoline, diesel, alcohol, light fuel oil, and mixtures thereof. 15. The fuel system of claim 9, wherein the injector is heated by utilizing the heat from the engine exhaust. 16. The fuel system of claim 15, further comprising a heating tube for transferring heat from the engine exhaust to the injector. 17. The fuel system of claim 6, wherein the injector comprises a resilient diaphragm that forms a bellows seal of the water / hydrocarbon mixture, and further comprises a mechanical cam for controlling the movement of the injector. • 4 ·· -1318. A fuel injection system for a furnace burner system of a power plant, comprising means for injecting a mixture of water and hydrocarbon fuel into the burner system, wherein the mixture is near a critical point such that said mixture is in a uniform, single phase. 19. The fuel system of claim 6, further comprising electrical means for heating the injector. 20. A fuel system comprising a water source, a hydrocarbon fuel source, a two fluid, high pressure, limited pressure metering pump having an inlet port connected to a water source and a hydrocarbon source, and having an outlet port; an injection chamber which communicates with the pump outlet port and receives water and hydrocarbon fuel at high pressure, the injection chamber comprising heating means for heating the water / hydrocarbon fuel mixture, and wherein the injection chamber includes a control valve for controlled discharge of the water-hydrocarbon fuel mixture, wherein the temperature and pressure of the water-hydrocarbon mixture is near a critical point such that the mixture is in a uniform, single phase. 21. The fuel system of claim 20, further comprising an internal combustion engine to which said mixture is fed and having a crankshaft, and wherein the control valve is actuated in response to the angular position of the crankshaft. 22. The fuel system of claim 21, wherein the engine is a spark ignition engine. 23. The fuel system of claim 21, wherein the engine is a compression ignition engine. 24. The fuel system of claim 20, wherein the mixture is fed to a gas turbine engine of a power plant. • 4 4 · · 4 4 44 ♦ · 4 4 4 4 -1425. The fuel system of claim 20, wherein the temperature of the water / hydrocarbon fuel mixture is above 363 ° C and the pressure is in the range of 3000 psi to 4000 psi (i.e. 20.685 MPa to 27.58 MPa).