WO2007057720A1

WO2007057720A1 - System for the production of fuel

Info

Publication number: WO2007057720A1
Application number: PCT/GR2006/000063
Authority: WO
Inventors: Dionysios Choidas
Original assignee: Dionysios Choidas
Priority date: 2005-11-21
Filing date: 2006-11-21
Publication date: 2007-05-24
Also published as: GR1005384B

Abstract

The invention refers to a method controlling the operation of an internal combustion engine (1) consuming two different fuels. The first of them is available commercially and, before its consumption, it is stored inside a fuel tank. The second is the product of a thermochemical reaction, inside a device called reactor (6), between one portion of the engine exhaust gases and an organic matter or biomass (60) and consists of a mixture containing flammable and inert vapors and gases. These fuel-enriched exhaust gases are reintroduced into the engine, preferably through the intake duct (2), serving as the main fuel of the engine operation, although their quantity and quality, as a fuel, are not controlled. The first fuel is transferred to the engine (1), through one or more injectors (3) or a carburetor and its consumption, during the steady-state operation of the engine, is performed through small, controlled quantities under the continuous monitoring of an electronic control unit or ECU (11). Any fuel flow adjustment is performed by the ECU according to the signal coming from an oxygen sensor (10) located downstream the exhaust gases flow. The operating concept is based on the addition of the appropriate supplementary amount of the first fuel (while the engine is operating, mainly, with the produced in the reactor gaseous fuel) in such a manner as to stabilize the signal of the oxygen sensor around a predetermined value although the production and consumption of the in-situ produced gaseous fuel remain uncontrollable.

Description

SYSTEM FORTHEPRODUCTIONOFFUEL

This invention refers to a method controlling the operation of an internal combustion engine consuming two different fuels, &e first of them (called, hereinafter, as "secondary fuel") is a gaseous or liquid fuel (and, preferably, commercially available) and the second fuel (called, hereinafter, as "primary fuel") is produced in-situ by the thermal and chemical reaction between a portion of the exhaust gases of the engine (called, hereinafter, as "recycled exhaust gases") and an organic substance (called, hereinafter, as "biomass"), consisting of agricultural or municipal or industrial wastes or any mixture of them. The chemical reaction is performed inside a chamber (called, hereinafter, as "reactor") where the recycled exhaust gases come in direct contact with the biomass, decomposing it. The products of this decomposition are a mixture of both inert and flammable gases and vapors that is mixed with the recycled exhaust gases leaving the rest of the biomass behind and getting out of the reactor. This certain mixture of decomposition products and recycled exhaust gases (called, hereinafter, as "produced gas" which is used as the primary fuel) is transferred, directly or indirectly, to the combustion chamber of the internal combustion engine becoming, in such a way, the primary fuel of the engine.

It is a known practice to use this kind of organic biomass material as a fuel in external (and not internal) combustion engines. The problem is that most of these engines (and, especially, steam engines) have alow efficiency factor which, combined with the low heat value of a fuel like biomass, leads to a very low overall performance. Additionally, there are apparent problems with flying ash from the chimney of these external burners. On the contrary, the gasification of the biomass and the combustion (under high pressure and temperature) of its decomposition products inside an efficient internal combustion engine leads to an improved overall efficiency and a better control of the exhaust gases released to the atmosphere.

The main aspect of the certain innovation, compared to the known prior art, is based on the fact that the flow of the primary fuel to the engine is not strictly controlled - and in a fully simplified version of this invention, not controlled at all. instead of this, there is an accurate control of the flow of the secondary fuel, performed in such a way that the oxygen content of the exhaust gases flowing to the atmosphere (called, hereinafter, as "spent exhaust gases") is defined according to a desired function of the engine. This is accomplished by the presence of an oxygen sensor (named, also, as lambda sensor) placed downstream of the flow of spent exhaust gases. The signal of this sensor is transferred to an electronic control unit (and preferably to the main controlling unit of the engine) which electronic controlling unit (called hereinafter, as "ECU") controls the flow of the secondary fuel to the engine in such a way that the air/fuel ratio (where the fuel feeding the engine is the sum of a random amount of primary fuel and a controlled amount of secondary fuel) is adjusted, automatically, according to the desire of the user or the tuner of the engine. Obviously, the amount of air entering the combustion chamber of the engine can also be controlled, according to the desired torque output of the engine. Known technical level teaches that this function can be accomplished either by a variable aperture restrictor (i.e. : a throttle device placed inside the intake flow duct of the engine) or by the variation of inlet valve closing timing (Atkinson-cycle emulation) or by the adjustment of the variable output of a supercharger device (mechanical supercharger or turbocharger) or, finally, by a flow restricting device positioned downstream of exhaust gases flow.

In a more complicated embodiment of the present invention, the flows of air entering the engine and primary fuel can be adjusted simultaneously, by the ECU, according to a desired value of torque output of the engine. This can be performed with or without the additional help of a signal from a torque sensor (or any other torque sensing apparatus - i.e.: electric generator) connected, directly on indirectly, with the torque output shaft of the engine.

The working procedure of an engine equipped with a fuelling device as prescribed in our invention is performed as follows.

The cold engine starts conventionally as if it was fuelled only with the secondary fuel. The secondary fuel is provided, preferably, by an ordinary fuel system (consisting of a direct or indirect fuel injection system or an electronically controlled carburetor) based on the known technical level and, most preferably, commercially available. The amount of fuel consumed by the engine, per revolution, is controlled by the ECU according (among others) to the signal of oxygen sensor. Obviously, in this mode, the engine behaves identically with an engine not equipped with the elements consisting our invention. During this first period, even if a part of the exhaust gases passes through the reactor, the low temperature of the decomposable matter will leave it unaffected. Evidently, there is no primary fuel production at this period of time and the exhaust gases return to the engine, through its intake, as per in a conventional Exhaust Gas Recirculation (EGR) device, without any fuel enrichment. After a while, the continuous passage of exhaust gases through the inside of the reactor creates a sufficient temperature rise in the decomposable matter. As a result, the biomass starts the emission of a mixture of vapors and gases which are mixed with the attacking exhaust gases, enriching them. When these enriched exhaust gases are reintroduced into the engine, the air/fuel mixture will become richer than previously. This will be detected by the ECU, via the oxygen sensor signal, and the programmed response of the ECU will be an enforced reduction of the secondary fuel flow, in an attempt to stabilize the sensor signal in a predetermined value. While the engine continues its running, the temperature rising of the biomass will have the result of an augmentation of the gas/vapor emissions from the biomass, enriching even more the exhaust gases and transforming them in primary gas as per our invention. This situation will have an amplified result when the biomass temperature becomes higher than a threshold defining the start of pyrolysis. During all this procedure, the ECU will decrease, continuously, the flow of secondary fuel up to a minimum value (which can be either a predetermined pilot value or even a zero value) in its programmed attempt to keep the oxygen content of the spent gases above a predetermined value. It is obvious to anybody familiar with the art that the comparatively lower heat value of the "supplemental" quantity of primary fuel (which, in practice, replaces a "chemically equivalent" amount of secondary fuel, after every "oxygen content correction" performed by the ECU) will have the effect of lower engine performance in comparison with the performance of the same engine fuelled with secondary fuel only. The obvious benefit of such a "performance sacrifice" is that the engine, in our invention, consumes mostly a primary fuel characterized by its very low (even nil) cost, compared to the high cost of any commercially available fuel (which is used, here, as secondary fuel). In such a case, if the achievement of a certain minimum power has a greater importance than the absolute fuel cost suppression, then there is a need to define a minimum (pilot value) in the secondary fuel flow. Otherwise, it is advisable to leave the flow of the secondary fuel to diminish if the production of the primary fuel, from the reactor, is sufficient for the certain working conditions of the engine. In such a case where there is a need for a higher temperature of the exhaust gases (i.e.: when the biomass has a high content of water) it is advisable to keep a higher level of the pilot flow of the secondary fuel. Alternatively, there must be a provision to burn, inside the reactor, a portion of the primary fuel, as it will be explained afterwards.

In a more complex embodiment of this invention, where the ECU controls both the secondary fuel flow and the air flow into the engine, it is apparent that the ECU strategy must be adjusted accordingly. In this situation, the priority must be given to the stabilization of the torque output according to a predetermined level. So, whenever it is been diagnosed (via the lambda sensor signal) a reduction of the oxygen content in the spent exhaust gases flow, it is preferable for the ECU to respond, initially, with a small increase of the air flow to the engine; and, immediately after, to proceed with the reduction of the flow of the secondary fuel if such a need continues to exist.

PRIORART

The solution of splitting the exhaust gases to a recycled flow and an "expelled to atmosphere" flow and the use of recycled gases, inside a reactor, for the production of fuel gas from a solid material, is well known from the prior art. For example, Figure 7 represents such a device, known as "Kalle Gasifier" (Sweden,

1942) which, during those times, performed as an on-board reactor wherein hot exhaust gases (and, in practice, a split fraction of the exhaust gases of the engine) attacked an amount of coal to produce a so- called "producer gas". This kind of fuel was a substitute to the gasoline, during 2^nd WW. Of course, due to the lack of a contemporary lambda sensor (and the accompanied ECU), such a simplified device does not have the ability to control adequately the air/fuel ratio and, subsequently, the quality of the exhaust gases of the engine. Additionally, the engine which was connected to this device was fueled strictly by the (so-called by us) primary fuel which is of low heat value, affecting adversely the power output. Obviously, the lack of a "strong" (in heat value) secondary fuel, performing as a "power additive" for the engine combustion, makes the use of this Kalle Gasifier acceptable only in certain circumstances where the solid material is coal or, in an emergency, dry wood pellets. Apparently, the lack of a supplemental amount of secondary fuel prohibits the use of this gasifier whenever the solid material is wet biomass or municipal waste with high humidity content, instead of pure coal. On the contrary, in the present invention, it is feasible to use any device identical or similar to the original Kalle Gasifier as a reactor to decompose any kind of biomass. In this case the reactor is just a part of the whole arrangement and it is supported by electronic controlled devices which are able to adjust the performance of the engine according to demand.

The operating principle of the original Kalle Gasifier is based on at least one split of the flow of the exhaust gases. As we can see in Fig. 7, the Kalle Gasifier consists of a tank (KGl) filled with coal (ICG2). The engine exhaust flow is splitted, in the junction KGO, to two separate flows, one exiting to the atmosphere and a second fed to the Gasifier. From the opening KG4 of the Gasifier, exhaust gases enter inside a flow splitter/mixer (KG5) where they are split to a"reactantflow" (KGIl) and a "fuel flow" (KGl 2). The reactant flow is driven, through the duct KGlO₃ into the venturi mixer (KG8) where it is mixed with atmospheric air. This amount of air is sucked inside the Gasifier (with the aid of a local "under pressure", created by the Bernoulli effect) through the air inlets KG3, which are controlled by the one-way valve KG9. The mixture of air and exhaust gases travels through the (buried inside the coal mass) vertical duct KG13 and reacts, partially, with the carbon. The products of this reaction (carbon monoxide/dioxide, hydrogen, nitrogen from the atmospheric air) are forced, through the outlet KG7, to enter inside another portion of the splitter/mixer (KG5) where they are mixed with the "fuel flow" of the remaining exhaust gases. This final mixture of exhaust gases and flammable gases, behaving as the sole engine fuel, is sucked by the engine via the outlet KG6. Apparently, the selection of a Kalle Gasifier, as the reactor of the system, is not mandatory in our present invention. Anybody skilled in the art can use any other appropriate type or configuration of drum, chamber or duct as a thermal or thermo-chemical reactor for biomass decomposition according to the demands of the present invention. Also known, from the prior art, is the solution of splitting the exhaust gas flow and forcing a small portion of it (enriched with oxygen and, sometimes, with water vapor) through a chemical reactor where the aforementioned gases contribute in the molecular cracking of hydrocarbons, preferably with the help of a catalyst. After their enrichment with the products derived from the chemical reforming (and, specifically, light hydrocarbons, hydrogen and carbon monoxide), these exhaust gases are reintroduced to the engine as a "primary fuel" or, alternatively, as a secondary fuel with the role of a "chemical additive" in such a manner as to enhance the combustion behavior of the engine. The document US4735186 describes an engine with a split flow of the exhaust gases. A portion of the exhaust gases passes through a reformer, fed with hydrocarbons, preferably consisting of heavy molecules. The cracking of these molecules enrich the exhaust gases with light molecule hydrocarbons and this mixture of exhaust gases and hydrocarbons is being fed again to the engine as an enhanced fuel with better properties than the initial hydrocarbons, before their cracking. There is not any provision for real-time self- adjustment of air/fuel ratio through the use of an oxygen sensor and an electronic ECU. Additionally, the reformed fuel is used as the primary one without any provision of a secondary fuel.

The document FR2860455 describes, also, an engine with a split flow of the exhaust gases. A portion of the exhaust gases passes around a heat exchanger/reformer without any physical contact between the exhaust gases and the reactants inside the reformer. In this case (and contrary to the scope of our invention) the exhaust gases are used only for their heat (which is transferred to the reactants, indirectly, through the walls of the heat exchanger) and they are not recycled in the engine.

There is also known, from the technical level, a method of using two different fuels in external combustion engines, especially Stirling engines, with the help of an oxygen sensor placed downstream of the exhaust gases. In this case, the primary fuel is coal (or another solid fuel, usually of low heat value) and the secondary fuel is a commercially available mixture of heavy hydrocarbons. The flow of the secondary fuel into the external burner is controlled from an ECU (connected with the oxygen sensor) so as to achieve the maximum heat release inside the external burner of the engine without surpassing a minimum predetermined value of oxygen content in the flue gases released to the atmosphere.

Known, also, from the technical level, are some arrangements where an engine is being fed, simultaneously, with two different fuels separated as primary and secondary. In one known case the diesel reciprocating engine is fed (through the suction of its air intake duct) with the vapors of an hydrocarbon spillage (i.e. in a well) using them as a secondary fuel whilst the primary fuel is diesel oil being introduced, in the conventional manner, through a direct injection in the combustion chamber. Ih a similar arrangement, another diesel engine (connected with an electro-generator) uses directly injected diesel fuel as the secondary fuel (in a pilot manner) and the mixture of gases and vapors, flaring from a petrochemical refinery, as the main fuel.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:

FIG. IA is a schematic view of an exemplary layout of the main parts of the present invention.

FIG. IB is a schematic view of an exemplary forced induction of both the atmospheric air and the primary fuel.

FIG. 2 is a schematic view of an exemplary layout of the main parts of an embodiment of the present invention applied to an internal combustion engine of a reciprocal piston type.

FIG. 3 is a schematic view of an exemplary layout of the main parts of the present invention indicating some possible places where the secondary fuel is fed to the engine when the primary fuel is being fed directly into the combustion chamber of the engine. FIG. 4A is a schematic view of an exemplary internal combustion engine of a reciprocal piston type where the exhaust gas flow is split among different exhaust valves.

FIG. 4B, 4C and 4D are schematic views of an embodiment in an exemplary internal combustion engine of a reciprocal piston type where the exhaust gas flow is split among different exhaust valves and, additionally, the exit of recycled gas and the inlet of the primary fuel is performed through the same valve.

FIG. 5 is a schematic view of an exemplary lay out of the main parts of the present invention incorporating a method for an additional usage of the primary fuel, after its enrichment with oxygen. FIG. 6A,6B are schematic views of an embodiment of the present invention concerning a reactor arrangement with improved performance

FIG. 6C, 6D are schematic views of an embodiment of the present invention concerning a reactor connected with the exhaust side of a turbine.

FIG. 7 is the layout of an original version of the Kalle Gasifier in an arrangement presented in various internet sites.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following description of the preferred embodiments) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

Ih Fig. IA there is a schematic presentation of the fundamental elements of this invention and their interconnection. A block represents the internal combustion engine (1), which can be of any reciprocal or rotary piston type or a turbine type engine. The admission of atmospheric air inside the engine is provided by the intake duct (2) and the exit of exhaust gases is provided, in a first embodiment, by the common outlet duct (89). At some point the common outlet duct splits itself in an exhaust outlet terminal duct (8) - which leads one portion of exhaust gases (spent exhaust gases) to the atmosphere- and a recycling duct (9) which leads the other portion of the exhaust gases (recycled exhaust gases) to the reactor (6) wherein they meet the biomass (60) and react thermo-chemically with it through a direct contact with its molecules. The decomposition of biomass enriches the recycled exhaust gases with flammable gases and vapors, transforming them to primary fuel. The primary fuel leaves the reactor and is transferred, through the primary fuel duct (5), to an outlet point (50) where it re-enters into the engine. In the exemplary embodiment of figure IA, the primary fuel duct (5) leads the primary fuel into a junction of the intake duct (2) where the primary fuel is mixed (preferably with the aid of an appropriate mixing device, not shown in the figure) with the atmospheric air entering in the engine. At this point it is desirable to have a blow-by protection device (not illustrated) in the flow of primary fuel inside the primary fuel duct (5). This device can be of any type known from the technical level (i.e.: one-way valve, spark arrester, bubble water filter etc.) and its primary function is to prevent the "traveling", inside the primary fuel duct (5), of any flame or flash which will, accidentally, appear inside the intake duct (2) during the operation of the engine. The adjustment of the flow of the air, entering into the engine, can be controlled by a throttle (4) or any other appropriate device or method. At a certain point of the intake duct (or, directly, in the combustion chamber of the engine), there is a device which feeds the engine with controlled amount of secondary fuel. In the example of figure IA this device is a fuel injector (3) whose flow is controlled by the ECU (11) according to the electrical signal of an oxygen sensor (10) located on the exhaust outlet terminal duct (8) or the common outlet duct (89).

For example, let us suppose that the ECU is programmed for an operation of the engine with stoichiometric air/fuel ratio. In such a case, the ECU will control the secondary fuel flow according to the deviations (from the stoichiometric value λ=l) of the signal produced by the oxygen sensor. Ih every case that the "lambda" signal corresponds, momentarily, to a rich mixture, the ECU will decrease, accordingly, the secondary fuel flow to the engine. On the contrary, when the "lambda" signal corresponds to a lean mixture, the ECU will increase, accordingly, the secondary fuel flow to the engine.

Apparently, in the case where there is a catalyst device in the exhaust outlet terminal duct (8) for the final refining of the spent gases before their exit to the atmosphere, it is advisable, by the common practice, to use two oxygen sensors, one upstream of the catalyst device and one downstream. By combining the signals of these two sensors, the estimation of the oxygen content in the spent gases (and consequently, the air/fuel ratio inside the engine) can be more accurate.

The secondary fuel can be any appropriate liquid or gaseous organic matter or mixture. Preferred examples (and commercially available) are hydrocarbons, alcohols, esters (bio- diesel, for example), di-methyl-ether (DME), seed oils etc. or, even, hydrogen. In some cases there is a possibility to use, as a secondary fuel, not an "external" fuel but a fuel produced inside the reactor and excluded from the synthesis of the primary fuel by an appropriate device, preferably one belonging to the known technical level. For example, if the biomass is wood, then it is feasible, for anybody skilled in the art, to achieve a concentration of the methanol vapours (a procedure known as "dry distillation of wood") which are emitted from the biomass at an acceptable, technically, temperature level. These methanol fractions can be stored, temporally, as a liquid or vapour and, according to the momentary demands of the engine, they are used as the secondary fuel or part of it. Additionally, the technical level provides a lot of arrangements for on-board hydrogen production and storage. Commercially available, also, are the necessary devices for the use of this gas as a fuel in internal combustion engines.

The flow of the primary fuel, from the reactor (6) to the intake duct (2), is in a direct relation to the pressure difference between the recycling duct (9) and the intake duct (2). In most cases, this pressure difference is adequate for the operation of the system. On the contrary, there are cases where it is preferable not to rely, solely, on this positive pressure difference, especially when it is not easily predictable and controllable. Figure IB represents an exemplary configuration where the flow of the gaseous primary fuel, inside the primary fuel duct, is enforced by a centrifugal pump (12) or any other device of the known technical level with similar performance and, preferably, with a provision for a controlled output. In Hie same figure there is also an exemplary provision of an enforced induction of the air into the engine, through an appropriate device which can be, for example, a mechanical centrifugal pump or a positive displacement supercharger or the compressor of a turbocharger (13). The choice of the point where the primary fuel duct (5) meets the intake duct (before or after the compressor, in this example, as it is illustrated by the dotted lines) is related to the specific conditions under which the engine is operating and the relative pressure differences between the primary fuel duct and the various points of the intake duct. As it is already mentioned, it is desirable to have some kind of automatic control of the air flow entering the engine. This control can be performed by the ECU, according to its programmable operation, affecting either the opening position of the throttle (4) or the output of a supercharging device such as this one (13) which is illustrated in Fig. IB. It is also feasible to control the air flow to the engine through a supplementary charger or blower whose output is adjusted by the ECU, according to demand.

In Fig. 2 there is a schematic presentation of a simple embodiment of the present invention applied to an internal combustion engine of a reciprocal piston type, consisting of a cylinder (102), a reciprocating piston (103) in the cylinder, a crankshaft (105) and a connecting rod (104) which connects the piston and the crankshaft. In the cylinder head (101) there are poppet valves controlling the entrance of air (or mixture of air and fuel) inside the cylinder (inlet valves) and the exit of burnt gases out of the cylinder (exhaust valves). Jn this example there is at least one inlet valve (14) and at least one exhaust valve (7) and, for example, the secondary fuel injector is placed in a point upstream to the outlet point (50) of the primary fuel flow.

In Fig. 3 there is a schematic presentation of some possible places of a secondary fuel injector (3) and the two possible places of the outlet point (50) of the primary fuel duct (5). As we can see, the outlet point can be positioned on the intake duct (2), as indicated by the dotted lines, or directly inside the combustion chamber of the engine, as indicated by the solid lines. In this case it is necessary to provide a means of an one-way valve at the outlet point or, generally speaking, a controlled valve at the outlet, to avoid backflow. The first possible place (3A) for the secondary fuel injector (3) is on the intake duct (2), as previously mentioned, in a similar manner to the "indirect injection" of the conventional gasoline engines. The second possible place (3B) is inside the combustion chamber of the engine in a manner similar to the "direct injection" of gasoline and diesel engines. The third possible place (3C) is on the primary fuel duct (5). In this case the secondary fuel can be easily premixed with the warm primary fuel stream before their final mixing with the atmospheric air. Obviously, it is feasible to combine two or more of these proposed places, by the usage of two or more fuel inj ectors.

If the mixing of the secondary fuel and the atmospheric air is performed through an electronically controlled carburetor and not an injector, the preferable location for the mixing of air and secondary fuel is the same as indicated in the figure by the throttle (4). In this case, it is possible (but not strongly advisable) to have the outlet point (50) of the primary fuel in a location upstream of the throttle (4). The rate of primary fuel production from the biomass can be increased if there is not a common outlet duct (89) for recycled and spent exhaust gases before the split of their flows. Instead, it is preferable for the reciprocating engine to have separate exhaust valves for each one of the two exhaust gas flows - especially whenever the energy of the spent gases is absorbed by a turbocharger, located downstream of the common outlet duct. Figure 4 A represents a desired configuration where, in a reciprocating engine, there is at least one exhaust valve (called, hereinafter, as recycled exhaust valve (7A)) which is controlling the exit of the recycled exhaust gases from the cylinder and their discharge into the separate recycling duct (9). Also, there is at least one exhaust valve (called, hereinafter, as spent exhaust valve (7B)) which is controlling the exit of the spent exhaust gases from the cylinder and their discharge into the separate exhaust outlet terminal duct (8). Ih one embodiment of the present invention, the recycled exhaust valves (7A) of an engine have an advanced opening timing, compared to that of the spent exhaust valves (7B). This timing differentiation enables the recycled gases to carry in the reactor a greater amount of energy and, subsequently, to promote a greater decomposition rate of the biomass. In another, more effective embodiment, there is a variable timing of the exhaust valves and, preferably, with a variable phase difference between the opening timing of the recycled exhaust valves (7A) and the opening timing of the spent exhaust valves (TB).

Jh the case where the engine is of a two-stroke type, with exhaust ports controlling the cylinder gas exchange in the place of poppet valves, it is apparent that at least one exhaust port (controlled by the piston skirt) can be dedicated for the communication between cylinder and reactor through a recycling duct. Ih a manner similar to the facts described in the previous paragraph, the opening of this exhaust port at a slightly advanced time (in comparison to the opening time of the spent gases exhaust port or ports) is beneficial for the gas producing performance of the reactor.

In another embodiment of the present invention, a better control of the system can be achieved. This embodiment consists of at least one device controlling, approximately, the flow rate of primary fuel to the engine. Also, in this embodiment, it is useful to have at least one device (located inside the intake duct and downstream of the outlet point) by which the flow rate of the fuel mixture (consisting of air and primary fuel, at least) can be controlled. This embodiment is illustrated in Fig. 4A where the flow rate of the primary fuel is controlled by a primary fuel throttle (4B) and the flow rate of the air/fuel mixture is controlled by a mixture throttle (4A). Apparently, a better control can be achieved when the flow rate of the primary fuel is adjusted by the variable output of a positive displacement pump (not illustrated) which is located in a place similar to that of the primary fuel throttle (4B). Even then, it is impossible to perform an accurate control of the primary fuel content in the final air/fuel mixture which is consumed by the engine. The reason for this inadequacy is the lack of consistency in the composition of the mixture of gases and vapors produced inside the reactor.

Whenever there are separate exhaust valves for the recycled gases and the spent gases, it is possible to use the recycled exhaust valve, additionally, for the controlled flow of the primary gas inside the cylinder. This embodiment is illustrated in Fig. 4B where (at least) one recycled exhaust valve (7A) controls, simultaneously, the outflow of recycled gases to the airtight reactor (6) and the inflow of primary gas from the (nearby) reactor to the cylinder (102). In this case, the recycled exhaust valve (7A) opens, for a first time, during a moment of the expansion cycle of the engine operation while the pressure, inside the cylinder, is higher than the pressure inside the reactor. Under these circumstances, a quantity of hot gases will be transferred from the cylinder to the reactor, activating the biomass decomposition. The closing of this valve is preferred to be performed during the expansion stroke of the engine or in an early stage of the exhaust stroke, so as to keep a high level of pressure and temperature inside the reactor. The second opening of this valve must be performed during the intake stroke of the engine or at an early moment of the compression stroke, while the pressure inside the reactor is higher than the pressure inside the cylinder. Under these circumstances, a quantity of primary fuel will be transferred from the reactor directly to the inside of the cylinder. A sufficient filtering device (not shown in the figure), located between reactor and cylinder, will protect the cylinder from the biomass derived ashes and, in an advanced embodiment of the known technical level, from the acid vapors which are produced during the biomass decomposition.

Jn Fig. 4C there is a schematic view of an improved embodiment of the arrangement presented in Fig. 4B. In this case there is a partial separation between inflow and outflow inside the common duct (or pair of ducts, as illustrated in Fig.4D) connecting the reactor with the cylinder. This separation enhances the circulation of gases inside the reactor (and, consequently, the biomass decomposition performance) and it is performed through one (at least) one-way valve (77) located inside the aforementioned duct(s) which connect the reactor with the cylinder.

As it is already mentioned, the reactor in the arrangement of Figures 4B, 4C and 4D must be of an absolutely airtight type in the scope of avoiding leakages due to the much higher working pressures which are an elementary part of its operation. In the case where there is an external air pump which supplies additional air inside the reactor, the skilled in the art person must adjust the pressure of this compressed air in such a manner as not to provoke a blockage against the passage of hot gases from the cylinder to the reactor during the first opening of the recycled exhaust valve(s). On the contrary, if the selected pressure of the compressed air is lower than a threshold value, the presence of a (backflow preventing) one-way valve, between the reactor and the compressor, will be beneficial or even necessary. Otherwise, in a much simpler embodiment, it is preferable to incorporate this additional air in the working gases of the cylinder. In this case, the ECU must be programmed to control (constantly or temporally) the operation of the engine according to a (pre-determined) lean air/fuel ratio. The acceleration of biomass decomposition inside the reactor will be accomplished with the help of the excessive oxygen which will be present in the composition of the hot gases transferred from the cylinder to the reactor. This condition can be accomplished easily in an engine operating on a diesel cycle. In this case, the engine is operating, almost exclusively, under lean air/fuel ratio with the directly injected diesel fuel (as secondary fuel) used mostly for the ignition of the (already present in the cylinder) lean mixture of air and primary fuel. In Fig. 5 there is a schematic view of an embodiment of the present invention wherein a controlled portion of the primary fuel is recycled into the reactor whenever there is a demand for accelerated decomposition of the biomass. The flow rate control of this recycled primary fuel can be performed, manually or automatically, either through an appropriate pump (and, preferably, characterized by a controllable output) or straight through a recycled fuel throttling device (16) of any convenient type, provided that there is sufficient pressure differentiation between the inlet (591) of the interconnecting duct (59) and its outlet (592). Apparently, the presence of a one-way valve (77), located in the interconnecting duct outlet (592), is preferred as a protection against a possible backflow inside the interconnecting duct. Recommended, also, is the appropriate formation of the interconnecting duct outlet (592) (and, preferably, the shape of the recycling duct, in the same location) in such a way as to enhance the Bernoulli effect occurring in front of the interconnecting duct outlet (592). The result will be an amplified suction of the primary fuel by the rapid flow of recycled exhaust gases.

In another embodiment, shown in Fig. 5, the recycled exhaust gases or the mixture of recycled exhaust gases and recycled primary fuel are enriched with a controlled (manually or automatically, by a pump or a throttle) amount of supplementary air through the supplementary air duct (15). This oxygen enrichment of the recycled gases can be performed at any location (with subsequent benefits or disadvantages) of their route to the reformer. Ih the certain drawing is presented an embodiment where the oxygen enrichment takes place after the mixing of recycled exhaust gases and recycled primary fuel and before the entrance of this mixture inside the reactor (6). The optimal amount of supplementary air in the air-enriched mixture can be determined, indirectly, via a calculation (preferably, executed by the ECU) according to the operating parameters of the engine, including the signal of the lambda sensor (10) located in the spent exhaust gases flow and, additionally, taking into concern the signal from a secondary oxygen sensor (18), located in the flow of the air-enriched mixture. In a more efficient embodiment (and in the scope of achieving a higher operating temperature inside the reactor), the recycled exhaust gases are enforced to pass through an oxidation catalyst (17) prior their entrance inside the reactor. The obligatory passage of the recycled exhaust gases through this "oxicat" (as it is known, commercially, in the automotive field) is preferred to occur independently of the existence of any arrangement which performs an enrichment of the recycled exhaust gases with recycled primary fuel or supplementary air.

Ih the same Fig. 5 is shown, indicatively, a kind of a filtering device, known from the technical level as "bubbling jar" (19). This filter is located between two halves of the primary fuel duct (5) and collects ashes and tars inside its bubbling water — and, also, acids; especially when the working liquid is an alkaline solution. Additionally, this recommended kind of filter serves as a protection to the reactor (6) against any "backflow explosion" occurring inside the engine and transmitted through the intake duct (2) when the intake valves are open. These backflow explosions (or "flashes") are rather common in this type of "enriched exhaust gas recirculation" arrangements due to the easy accumulation of carbon deposits inside the engine and the ample presence of hydrogen in the mixture of the primary gas.

In another embodiment of the present invention (Figures 6A, 6B, 6C₅ 6D), the flow of the exhaust gases, after their exit from the engine (1) and its common outlet duct (89), is split into two ducts which are placed one inside the other. According to this way, the flow of the exhaust gases is split into an "internal" flow (which occupies the internal duct) and an "external" flow which occupies the outside duct. Preferably, the internal flow consists of spent exhaust gases, en route to their exit to the atmosphere and the external flow consists of recycled exhaust gases en route to their transfer to the reactor. In such a case, the internal duct is the exhaust outlet terminal duct (8) and, accordingly, the external duct is the recycling duct (9) as it is illustrated in Fig. 6 A.

Additionally, in Fig. 6A is illustrated (in an extremely generalized view) an embodiment by which the present invention gains a performance advantage related to the operation of the reactor. As it can be seen, the reactor (6) is formed inside a portion of the recycling duct (9) having, as its inner wall, the outer surface of the exhaust outlet terminal duct (8).

It is obvious that this arrangement maximizes the heat transfer from the recycled exhaust gases to the biomass (60) and, additionally, provides an "active insulation" to the walls of the reactor. In the same drawing there is a generalized view of a preferable way to feed the reactor with biomass and the collection of its remains and ashes (67) inside an ash collector (68).

In Fig. 6B is illustrated (in an extremely generalized view) the lay-out of the embodiment of Fig. 6A in a case where there are different exhaust valves (7 A, TB) for the recycled exhaust gases and the spent exhaust gases respectively.

In Fig. 6C is illustrated (in an extremely generalized view) an embodiment of the present invention where the arrangement that has been already described in Fig. 6 A is now adapted to the exhaust side of an internal combustion engine (1) of the turbine type, presented schematically. Ih this case, the duct of the exhaust outlet terminal duct (8) and the recycling duct (9) are of a circular section and the exhaust outlet is positioned inside the recycling duct and, preferably, in the same axis. This arrangement is providing the reactor (6) area, which is located inside the recycling duct, with exhaust gases coming from the periphery of the circular exhaust side of the turbine (IB). The temperature of these exhaust gases is higher than the temperature of exhaust gases coming from locations of the turbine exhaust having smaller radial distance from the centre of the turbine disc. In such a way, it is preferable to split the exhaust gases and use the hotter ones, from the periphery of the turbine, as recycled exhaust gases, inside the reactor (6) and leave the less hot gases (coming from the "central" areas of the turbine) pass, through the exhaust outlet terminal duct (8), to the atmosphere, as spent exhaust gases.

In Fig. 6D is illustrated (in an extremely generalized view) an embodiment of the present invention, almost identical to that described in Fig. 6C. In this case the turbine (IB) is part of a turbo-supercharger connected with the exhaust system of an internal combustion engine (1) of the piston type (where the piston can be reciprocating as in conventional engines or rotating as in Wankel engines).

In the case where the biomass has a high water content - as, for example, waste water 5 concentrations provided as an organically enriched mud -, the procedure of its decomposition to a dry, final product, can be derived, profoundly, from the various embodiments of the present invention or a combination of two or more of them.

For example, when the biomass is in a rather liquid state with very high water content 10 then it is suggested to be decomposed in a reactor where it is injected, in small droplets, inside the stream of recycled gases and, preferably, in repeated cycles (and, preferably, in separate reactors) up to the point of a final dry state. Then, according to the embodiment described in Fig. 5, the biomass can be pyrolysed, in a high temperature reactor, in an atmosphere of recycled exhaust gases enriched wife primary fuel and air. In the primary 15 stages of this procedure it is advisable to use (through a heat exchanger) the heat of the spent exhaust gases in the scope of removing a first amount of moisture.

A skilled in the art person is able to materialize all these procedures in a plurality of alternative arrangements, derived profoundly, from the described embodiments and 20 remaining inside the spirit of the present invention.

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Claims

1. System for the production of fuel for an internal combustion engine (1), which production is performed through the reaction of a portion of the engine exhaust gases with an appropriate kind of organic waste called hereinafter, generally, as biomass (60) and this system is consisted of

- at least one device, called hereinafter as reactor (6), wherein the aforementioned portion of exhaust gases reacts with the biomass through a direct contact with its matter, decomposing it, an exhaust system wherein the exhaust gases are split in two flows and the first of these flows, called hereinafter as spent gases flow, is exhausted to the atmosphere through the exhaust outlet terminal duct (8) and the second of them, called hereinafter as recycled exhaust gases flow, is transferred through a recycling duct

(9) to the inside of the reactor wherein the hot recycled exhaust gases attack the biomass thermally or thermo-chemically, according to temperature, decomposing it in a mixture of gases and vapors and this mixture is called, hereinafter, as the primary fuel of the engine, a primary fuel system consisting of a primary fuel duct (5) and the assorted fuel filtering devices where, this primary fuel duct is transfers, through the outlet point (50), the primary fuel inside the engine, wife a flow rate depending, partially, on the operation state of the reactor, and this flow rate is consumed by the engine either directly by its transfer inside the combustion chamber of the engine or indirectly, by the mixing of the primary gas with the intake air of the engine at an appropriate location lengthwise the intake duct (2) of the engine, a secondary fuel system whose flow rate to the engine is controlled by an electronic control unit, called hereinafter as ECU (11), and this control is being performed according to the operating state of the engine, to the operating program incorporated in the ECU and, finally, to the electric signal of at least one oxygen sensor (10) located in Ae flow of the exhaust gases which exit from the engine, where, the signal of the oxygen sensor is a function of the oxygen content of exhaust gases and this system is characterized by that the flow rate to the engine and the composition of the primary fuel, during the operation of the engine and the system, are not controlled accurately or not controlled at all and by that in every momentary deviation from a predetermined value of the signal produced from the oxygen sensor, the ECU responds with an appropriate adjustment of the flow rate of the secondary fuel which is being transferred to the combustion chamber of the engine

2. System for the production of fuel for an internal combustion engine, according to Claiml, characterized by that the recycled exhaust gases are mixed with a controllable amount of supplementary air prior to their introduction inside the reactor.

3. System for the production of fuel for an internal combustion engine, according to Claiml, characterized by that the recycled gases are mixed with a controlled amount of primary fuel, prior to their introduction inside the reactor. 4. System for the production of fuel for an internal combustion engine, according to

Claiml, characterized by that the recycled gases are forced to pass through an oxidation catalyst (17) prior their contact with the biomass (60) inside the reactor.

5. System for the production of fuel for an internal combustion engine, according to Claims 1 and 2, characterized by that there is at least one secondary oxygen sensor

(18) positioned at a point of the flow of the recycled exhaust gases, which point is located upstream of the biomass matter inside the reactor and downstream of the point where the recycled gases are mixed with an amount of supplementary air, provided through the supplementary air duct (15).

6. System for the production of fuel for an internal combustion engine, according to Claiml, characterized by that the exit, from the engine, of the exhaust gases which will be transferred to the reactor as recycled exhaust gases, is being performed through the recycled exhaust valve (7A) which is different from the spent exhaust valve (7B) through which is being performed the exit of the spent exhaust gases from the cylinder and by that the recycled exhaust valves (7A) open a fraction of time earlier than the spent exhaust valves (7B) of the same cylinder.

7. System for the production of fuel for an internal combustion engine, according to Claims 1 and 6, characterized by that the communication between the cylinder

(102) of the engine and its corresponding reactor (6) is being performed, exclusively, through a recycled exhaust valve (7A), by that this valve opens for a first time and closes during a period of the engine cycle where the pressure inside the cylinder is higher than the pressure inside the reactor, thereby provoking the spontaneous transfer of recycled exhaust gases from the cylinder to the reactor and by that this aforementioned valve opens, for a second time in the same engine cycle, at a moment where the pressure inside the reactor is higher than the pressure inside the cylinder, thereby provoking the spontaneous transfer of primary fuel from the reactor to the cylinder.

8. System for the production of fuel for an internal combustion engine, according to Claiml, characterized by that the exit of the exhaust gases from a cylinder is performed through more than one exhaust ports located on the cylinder, by that at least one exhaust port is being uncovered from the piston skirt at a fraction of time earlier than the rest of the exhaust ports of the same cylinder and by that the recycled exhaust gases exit from the cylinder through the exhaust port which opens a fraction of time earlier than the rest exhaust ports of the same cylinder.

9. System for the production of fuel for an internal combustion engine, according to Claiml , characterized by that a part of the exhaust outlet terminal duct (8) is located inside the recycling duct (9) and by that a part of the internal space, between these aforementioned ducts, is the reactor (6).

10. System for the production of fuel for an internal combustion engine, according to Claims 1 and 9, characterized by that at the portion where the exhaust outlet terminal duct (8) is located inside the recycling duct (9) the two aforementioned ducts have, approximately, the same longitudinal axis.

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