Internal combustion engine

Abstract

Internal combustion engine, said engine comprising: - at least one cylinder defining a combustion chamber, said cylinder comprising a cylindrical wall and an end wall limiting the cylinder in a longitudinal direction at a first longitudinal position of said cylinder, said end wall comprising: - an inlet port for feeding a gas mixture to said cylinder and an inlet valve that is moveable for opening and closing the inlet port, - an outlet port for discharging exhaust gas from said cylinder; - preferably, a fuel injector for injecting fuel into the cylinder, and - a spark plug that is centrally arranged in the end wall; - a piston disposed in said cylinder, wherein a head of said piston limits the cylinder in a longitudinal direction at a second, adjustable longitudinal position of said cylinder, said piston being moveable to reciprocate between a top position relatively close to the end wall and a bottom position at a greater distance from the end wall; - an inlet manifold connected to the inlet port for feeding the gas mixture to the cylinder via the inlet port, preferably wherein an indirect fuel injector is arranged in the inlet manifold for supplying fuel to the gas mixture; - wherein said inlet valve comprises a substantially flat guiding surface facing towards the inlet port and a guiding wall protruding from the guiding surface in the direction of the inlet port, said guiding wall being substantially curved in a longitudinal direction thereof, and said guiding wall being arranged such that it is curved in substantially the same direction as the cylindrical wall, such that said inlet valve is arranged for guiding the gas mixture in a direction substantially parallel to the end wall and having a largest component that is substantially tangential to the cylindrical wall.

Description

[0001] The present invention relates to an internal combustion engine and a method of controlling said internal combustion engine.

[0002] Internal combustion engines come in many different forms. A common type is the reciprocating internal combustion engine that is, still to this day, found in most cars, truck, motorcycles and other types of small to medium sized vehicles. The four-stroke gasoline engine, based on the Otto-cycle, and diesel engine, based on the Diesel-cycle, are the most known examples of the reciprocating internal combustion engine.

[0003] It is important to realise a proper ignitable mixture of air and fuel in the combustion chambers of such a gasoline engine, not only at medium and high loads, which are then easier to obtain, but especially at lower loads, in order to realise high volumetric engine efficiency and relatively clean exhaust gases. At lower loads a relatively small amount of air is drawn into the combustion chamber when the throttle valve, located in the inlet manifold, is then partially closed. Consequently the combustion chamber does not fill properly with air / fuel, resulting in a mediocre mixture build-up which results in a low volumetric engine efficiency and high pumping losses.

[0004] The diesel engine, due to its inherent advantages in terms of energy efficiency over the four-stroke gasoline engine, has become increasingly popular between the 1970's and 2010's. However, the exhaust gases of diesel engines come with various undesired byproducts, such as NOx and particulates, which, due to ever increasing regulations, need to be reduced as much as possible. In recent history, a program was discovered that was designed to cover up that emission standards were knowingly and willingly exceeded by many modern diesel engines. This affair become known as Dieselgate and resulted in a dramatic decrease in diesel engine popularity, and an increase in demand for gasoline engines, which in turn produce more CO 2 emissions, which, on the other hand, also need to be reduced in order to reduce the effects of climate change.

[0005] At the same time, more and more electrical cars are being introduced that, at least themselves, do not produce any emissions. However, production of batteries and, when the electricity of said cars is generated using coal- or gas powered generators, still results in (CO 2 ) emissions and other environmental impacts. There is therefore still a need for an improved internal combustion engine that is able to combine some of the benefits of the diesel and gasoline engines for obtaining an internal combustion engine having an improved energy efficiency and / or lower NO x emissions when compared to a traditional four-stroke gasoline engine and / or diesel engine.

[0006] This goal is at least partly met by an internal combustion engine, said engine comprising: at least one cylinder defining a combustion chamber, said cylinder comprising a cylindrical wall and an end wall limiting the cylinder in a longitudinal direction at a first longitudinal position of said cylinder, said end wall comprising: an inlet port for feeding a gas mixture to said cylinder and an inlet valve that is moveable for opening and closing the inlet port, an outlet port for discharging exhaust gas from said cylinder; a fuel injector for injecting fuel into the cylinder, and a spark plug that is centrally arranged in the end wall; a piston disposed in said cylinder, wherein a head of said piston limits the cylinder in a longitudinal direction at a second, adjustable longitudinal position of said cylinder, said piston being moveable to reciprocate between a top position relatively close to the end wall and a bottom position at a greater distance from the end wall; an inlet manifold connected to the inlet port for feeding the gas mixture to the cylinder via the inlet port; wherein said inlet valve comprises a substantially flat guiding surface, preferably having chamfered and / or rounded edges, facing towards the inlet port and a guiding wall protruding from the guiding surface in the direction of the inlet port, said guiding wall being substantially curved in a longitudinal direction thereof, and said guiding wall being arranged such that it is curved in substantially the same direction as the cylindrical wall, such that said inlet valve is arranged for guiding the gas mixture in a direction substantially parallel to the end wall and having a largest component that is substantially tangential to the cylindrical wall.

[0007] A spark-ignited engine requires a gas mixture in the direct vicinity of the spark plug, i.e. the source of the spark that is arranged to ignite the fuel in the combustion chamber, that comprises a sufficiently high fuel-air ratio that efficiently ignites. The curved guiding wall, i.e. a wall having a substantially concave inner surface that faces a central section of the combustion chamber and a substantially convex outer surface that faces the (closest by arranged part of the) cylindrical wall, enables to have a gas mixture flow into the combustion chamber in an inflow direction having a largest directional component that is substantially tangential to the cylindrical wall, such that the inflowing gas mixture is urged to spiral around the centre of the combustion chamber (i.e. in a swirling motion). This enables (even in engines not comprising a direct fuel injector), in for instance intermediate load levels of the engine, when an inner part of the inflowing gas mixture, that is closest to the centre of the combustion chamber, is given a different composition to an outer part of the inflowing gas mixture, that is closest to the cylindrical wall, to obtain in the centre of the combustion chamber, i.e. around the spark plug, a rich gas mixture (i.e. λ < 1) that easily and efficiently ignites, and at radii further from the centre of the combustion chamber a less rich, stochiometric (i.e. λ = 1) or even lean gas mixture (i.e. λ > 1) or substantial inert gas mixture, such that, preferably, over the full volume of the combustion chamber a stochiometric gas mixture is obtained.

[0008] In a preferred embodiment, the inlet manifold comprises a partition wall dividing the inlet manifold into an outer and inner channel, and wherein the guiding wall of the inlet valve is substantially aligned with the partition wall of the inlet manifold, such that an outer gas mixture fed to the cylinder via the outer channel of the inlet manifold is guided by an outer surface of the guiding wall and an outer part of the guiding surface and an inner gas mixture fed to the cylinder via the inner channel of the inlet manifold is guided by an inner surface of the guiding wall and an inner part of the guiding surface, wherein the outer surface is facing towards the cylindrical wall and the inner surface is facing towards a centre of the cylinder and wherein the outer part is closer to the cylindrical wall than the inner part, in particular wherein the indirect fuel injector is arranged in the inner channel of the inlet manifold.

[0009] Partitioning the inlet manifold into an inner and outer channel enables to more effectively direct inflowing gas mixtures having different compositions, as the effect of mixing the different gas mixtures in the inlet manifold during the intake stroke is minimized, such that the variation of gas mixture compositions over the radius of the combustion chamber is obtained, enabling the advantages described above. It is also noted that, in addition to the inner and outer channel, even more substantially parallel channels may be arranged in the inlet manifold. The inlet valve may than also be arranged with multiple guiding walls, preferably wherein further partition walls are provided between each pair of adjacent channels and wherein the multiple guiding walls of the inlet valve are preferably substantially aligned with the respective guiding walls.

[0010] It is then preferred that the inlet manifold comprises one or more controllable inlet valves for independently controlling flows of fresh air to the outer and inner channels, in particular wherein a respective controllable inlet valve is movable between a fully closed state, wherein the respective controllable inlet valve blocks any fresh air from passing the respective controllable inlet valve, to a fully open state, wherein the controllable inlet valve allows for a maximum of fresh air to pass the controllable inlet valve. The various valves thereby enable to modify and control the gas mixture compositions in the various channels.

[0011] The guiding wall is preferably arranged such that, when the inner and outer gas mixtures are fed to the cylinder, it forces the outer gas mixture to encircle and enclose the inner gas mixture in the cylinder, such that the inner gas mixture is urged towards the centre of the combustion chamber, and thereby towards the spark plug, thereby contributing to the above described effect.

[0012] A preferred embodiment comprises a recirculation system for recirculating part of the exhaust gas as recirculated exhaust gas to the outer and / or inner channel, in particular wherein the recirculation system comprises a gas conduit system for guiding the recirculated exhaust gas from an exhaust side of the internal combustion engine that is located downstream of the outlet port to the outer and / or inner channel.

[0013] At low speeds, gasoline engines suffer efficiency losses at small throttle openings from the high turbulence and frictional (head) loss when the incoming air must fight its way around the nearly closed throttle (pump loss). By allowing to recirculate the exhaust gases the recirculated exhaust gasses can, effectively, replace fresh air from the intake, thereby effectively reducing the throttle, while not significantly increasing the flow resistance. One effectively allows the engine to breath more freely. As the recirculated exhaust gases can be considered to be practically inert (i.e. little to no fuel and oxygen remaining), the air-fuel ratio can still be maintained in the desired range. Additionally, due to the remaining heat in the exhaust gases, the thermal loss due to an increased flow of gases (i.e. when compared to a traditionally throttled engine) running through the engine is reduced when compared to running the same amounts of fresh air through the engine.

[0014] Preferably, the recirculation system is arranged for controlling the amount(s) of exhaust gas that is / are recirculated to the outer and / or inner channel, in particular wherein said recirculation system is configured for independently controlling the amounts of recirculated exhaust gas to the inner and outer channels. This enables to create an outer gas mixture having a higher percentage of recirculated exhaust gas, when compared to the inner gas mixture, that will occupy a outer ring-shaped space in the combustion engine. As the outer gas mixture is thereby mainly inert, it does not contribute to the ignition event, which is thereby mainly contained in the space of the combustion chamber occupied by the inner gas mixture. Hereby, one reduces the "active" size of the combustion chamber, such that the engine effectively tends to function as an engine having a smaller cylinder size, such that its efficiency will improve during low and intermediate loads.

[0015] It is preferred that the recirculation system is controllable by means of one or more controllable recirculation valves, in particular wherein the one or more controllable recirculation valves are movable from a fully closed state, wherein a respective controllable recirculation valve blocks any exhaust gas from recirculating to the outer and / or inner channel, to a fully open state, wherein the controllable recirculation valve allow for a maximum of exhaust gas to be recirculated as recirculated exhaust gas to the outer and / or inner channel. This is one approach for enabling controlling the engine as described above.

[0016] In a preferred embodiment, said internal combustion engine comprises, downstream of the outlet port, an exhaust gas processing system for removing unwanted substances from the exhaust gas, preferably comprising a particle filter and / or a catalytic converter, and wherein the recirculation system is arranged for recirculating exhaust gases that have been processed by the exhaust gas processing system. This prevents particles, unburned fuel and / or other undesired components to be recirculated into the recirculation system and internal combustion engine.

[0017] Preferably, the gas mixture is a mixture of (fresh) air, fuel and recirculated exhaust gas. Recirculated exhaust gas has already passed through the combustion process for at least one time, such that it comprises minimal, to virtually no, fuel and oxygen. The recirculated exhaust gas is thereby an inert gas that is substantially stochiometric. By rerouting part of it through the combustion chamber, the total amount of fuel and oxygen in the gas mixture is reduced, without restricting the flow of the gas mixture using a throttling valve, as is traditionally done, and results in throttling losses. Furthermore, in combination with the inner and outer channel, the outer channel can be supplied with a higher percentage of recirculated exhaust gasses, such that, in the combustion chamber, an outer ring of an inert (outer) gas mixture forms around the inner gas mixture, comprising the oxygen and fuel required for the combustion step. Hereby, the fuel and oxygen is comprised in a smaller volume of the combustion chamber, such that one effectively reduced the effective volume (i.e. active volume) of the combustion chamber. The internal combustion engine can thereby operate with a higher efficiency at lower load levels, when compared to an internal combustion engine that does not comprise the features.

[0018] It is preferred that at least the guiding surface of the inlet valve is non-round, in particular elongated and preferably kidney-shaped having its curvature in substantially the same direction as the guiding wall. This enables to arrange a guiding wall that is more elongated for an improved guidance of the inflowing gas mixture. As the inlet valve is thereby substantially only elongated in the (curved) direction of the guiding wall, the width (that is defined as a direction substantially perpendicular to the tangential of the curved guiding wall) of the inlet valve need not to be increased, which would occur in case a round inlet valve is arranged.

[0019] It is then further preferred that the non-round guiding surface comprises an inner side edge and an outer side edge, wherein the outer side edge faces the cylindrical wall and is arranged closer to the cylindrical wall than the inner side edge, wherein the outer side edge is substantially convex and the inner side edge is substantially concave; and preferably wherein said guiding wall is arranged substantially in the middle between the inner side edge and an outer side edge. This enables to obtain the substantially kidney-shaped valve having a substantially equal width along the length of the guiding wall.

[0020] In a preferred embodiment, the inlet port recess is shaped correspondingly to the inlet valve. The inlet valve thereby effectively seals the inlet port during the combustion and expansion steps, wherein the inlet valve preferably has a flat, chamfered and / or rounded sealing edge.

[0021] In a preferred embodiment, one of the inner part and the outer part of the guiding surface is elevated with respect to the other of the inner part and the outer part of the guiding surface. This enables altering the inlet time of the inner channel with respect to the outer channel, or vice versa, such that timings for the inner and outer gas mixtures can be set differently. If this elevated part is chamfered and / or rounded it will guide the valve as well.

[0022] In a preferred embodiment of the combustion engine it comprises a plurality of cylinders, wherein each cylinder is formed according to the cylinder as comprised in the internal combustion engine according to any of the preceding embodiments.

[0023] In a second aspect, the disclosure relates to a method of operating an internal combustion engine according to any of the preceding embodiments, comprising the steps of, in any suitable order: controlling a flow of a gas mixture through the inlet manifold into the combustion chamber, in particular during an inlet stroke of the internal combustion engine; injecting fuel in the inner channel of the inlet manifold and / or injecting fuel directly into the combustion chamber using the direct fuel injector, in particular during, preferably in a final stage of induction or early stage of the compression stroke of the internal combustion engine; and igniting the air / fuel mixture using the spark plug during the ignition event. The improved internal combustion engine according to any of the preceding embodiments can hereby be operated.

[0024] Preferably, the step of controlling a flow of a gas mixture comprises the steps of, in any suitable order: controlling, during the intake stroke of the engine, flows of the inner and outer gas mixtures through the inlet manifold such that, at least in a state prior to the direct injection of fuel into the combustion chamber, the combustion chamber holds the inner and an outer gas mixture, wherein the inner gas mixture is encircled and enclosed by the outer gas mixture, wherein said inner gas mixture has a different composition than the outer gas mixture.

[0025] It is preferred that the internal combustion engine comprises the exhaust gas recirculation system for recirculating part of the exhaust gas as recirculated exhaust gas to the outer and / or inner channel, wherein the method comprises controlling the exhaust gas recirculation system for controlling the composition of the inner and / or outer gas mixture such that the inner gas mixture has a different composition than the outer gas mixture.

[0026] In a preferred embodiment of the method, the inner gas mixture, at least in a state prior to directly injecting fuel into the combustion chamber using the direct fuel injector and in particular under load conditions in between idle and full load, comprises a higher volumetric percentage of fuel than the outer gas mixture, preferably wherein the outer gas mixture comprises no fuel; and / or in particular under load conditions in between idle and full load, the inner gas mixture comprises a higher volumetric percentage of oxygen than the outer gas mixture; and / or in particular under load conditions in between idle and full load, the outer gas mixture comprises a higher volumetric percentage of recirculated exhaust gases.

[0027] Preferably, the internal combustion engine is controlled, in particular under load conditions in between idle and full load, such that, during the intake stroke, a lean gas mixture, preferably comprising no fuel, is supplied through the outer channel and a substantially stochiometric gas mixture is supplied through the inner channel and wherein, after directly injecting fuel into the combustion chamber using the direct fuel injector, an overall gas mixture is obtained that is substantially stochiometric.

[0028] Summarizing, the advantage of the internal combustion engine according to at least one embodiment of this invention is that by using an inlet manifold that is separated in an inner and outer channel, which are connected to the inlet port at mutually different radial distances from the centrally disposed spark plug, i.e. the central axis of the cylinder, in which the respective flows of (fresh) air through the respective inner and outer channels are controllable by respective control valves, the amount of (fresh) air into the combustion chamber as a function of the radial position from the spark plug of the combustion chamber can be controlled, as well as its velocity. For example at lower engine loads the outer channel control valve, in combination with the standard throttle valve (which is used for controlling the flow of air in the inner channel), can be operated in such a manner that a limited amount of fresh combustible mixture is drawn into the central area of the chamber (i.e. close to the spark plug) via the inner channel, in which area extra fuel is injected directly. Further towards the outside of the combustion chamber a relatively large amount of air and / or exhaust gases (in case of exhaust gas recirculation) can be drawn into the chamber via the outer channel. Consequently the amount and quality of air / fuel mixture in the combustion chamber as a function of distance from the spark plug can be controlled so that for each engine load a proper amount of mixture, variable over the radius of the chamber, is drawn into the combustion chamber. This will result in a correct air / fuel mixture (λ ≤ 1) near the spark plug, surrounded by a homogenous part (λ = 1) as well as surrounded by a leaner mixture (λ > 1) and an inert part (the recirculated gas) at the largest distance from the sparkplug. The very small amount of relatively rich (0.8 ≤ λ ≤ 0.9) mixture near the spark plug will combust easily and set the rest of the relatively lean (λ > 1) mixture on fire. Depending on the load of the engine this happens 50° - 20° before TDC (top-dead-centre). Overall the amount of recirculated exhaust gases into the combustion chamber will vary with the load of the engine prior to ignition, but does not affect the (small) amount of combustible mixture close to the sparkplug. In doing so we can overcome the problem of a petrol engine to run an overall lean mixture over a wide engine load (with low pumping losses and high volumetric efficiency ) and still arrive at a good driveability. The recirculated exhaust gas comes from the exhaust while the engine is running with λ = 1 and acts partly as an inert gas for the next combustion cycle and is being recirculated over and over again. This way the petrol engine resembles a well-designed direct diesel engine which is known for its ability to run on a very lean mixture (with its extensive exhaust recirculation) without suffering from a bad mixture build up and still having hardly pumping losses.

[0029] In a diesel engine the load / speed is regulated with the amount of fuel injected. There is always sufficient air to burn the fuel. In this petrol engine the load is regulated by the amount of fresh air that is used by the engine; the amount of fuel that is injected is as much as is necessary to burn the oxygen in the air. All the valves of the presently disclosed internal combustion engine as described in any of the embodiments will see to it that the mixture will burn / ignite always.

[0030] The above described preferred embodiments of the method enable to operate the improved internal combustion engine, in particular to enable the earlier described reduction of the effective volume (i.e. active volume) of the combustion chamber is enabled, allowing for an improved efficiency during partial-load.

[0031] The present invention is further illustrated by the following figures, which show preferred embodiments of the internal combustion engine according to the present disclosure, and are not intended to limit the scope of the invention in any way, wherein: Figure 1 schematically shows in isometric view and schematically a part of a preferred embodiment of an internal combustion engine, in particular of a cylinder head thereof, according to the present invention. Figure 2 shows the part of the internal combustion engine according to figure 1 from a different viewpoint. Figure 3 shows a transparent top view of the part of the internal combustion engine according to figure 1. Figure 4 shows a transparent side view of the part of the internal combustion engine according to figure 1. Figure 5 shows in a schematic view the gas flows (in a direction as indicated by the arrows) through a second embodiment of the internal combustion engine, in particular of the cylinder head thereof. Figure 6 shows in a schematic view the gas flows (in a direction as indicated by the arrows) through a third embodiment of the internal combustion engine, in particular of the cylinder head thereof. Figure 7 shows a schematic cross-sectional view of the inlet valve and inlet port as comprised in the illustrated embodiments. Figure 8 and 9 schematically show the various zones of different gas mixtures in the combustion chamber under different load conditions.

[0032] Figure 1 and 2 show part of a cylinder head 1 of a preferred embodiment of a four-stroke spark-ignited internal combustion engine having indirect and direct fuel injection. The cylinder head 1 comprises part of the combustion chamber 2 and is adapted to fit onto the cylinder block (not shown) of the engine comprising the remaining part of the combustion chamber (typically formed as a bowl in the piston).The volume of the bowl will give the required compression ratio, which is preferably in the range of 13-15.

[0033] An inlet port 4 and an outlet port 6 are located in the top wall 3 (i.e. end wall) of the combustion chamber 2. The inlet port 4 can be closed and opened by an inlet valve 10, while the outlet port 6 can be closed and opened by an outlet valve 12. In case the outlet port 6 is in the open position, the combustion chamber 2 is in open fluid connection with the outlet manifold 7, from whereon the exhaust gases are guided further to the exhaust system (not shown) further downstream. Furthermore a spark plug 14 is positioned centrally in the top wall 3 of the combustion chamber 2. A fuel injector 16 injecting fuel directly into the combustion chamber 2 is positioned adjacent to the spark plug 14. The fuel injector 16 is adapted to inject fuel directly into the combustion chamber 2 in such a way that its spray pattern effectively creates a combustible mixture near the spark plug 14. Fresh air, which tangentially enters the combustion chamber 2, induces a swirl in the combustion chamber 2. In order to effectively create the combustible mixture, the fuel is injected slightly opposite the direction of the swirl by properly orienting the injector.

[0034] The inlet port 4 is connected to an inlet manifold 20 (see figures 3 and 4). The inlet manifold includes a throttle valve 22 to control the flow of air towards the combustion chamber 2. Downstream of the throttle valve 22 a partition wall 24 is positioned in the inlet manifold 20. Partition wall 24 extends parallel to the central axis 18 of the cylinder, i.e. perpendicular to the paper in the view of figure 3 and runs from section valve 30 to inlet valve 10. Partition wall 24 subdivides the inlet manifold 20 into an inner channel 26 and an outer channel 28. Due to the fact that the partition wall 24 extends parallel to the central axis 18 and the inlet port is located in the top wall 3 of the combustion chamber 2, the inner channel 26 debouches into the combustion chamber 2 closer to the centrally disposed spark plug than the outer channel 28, as seen in radial direction.

[0035] The flow of (fresh) air through the outer channel section 28 can be controlled by a controllable outer channel valve 30, more in particular a butterfly valve, which in this example is located at the upstream end of wall part 24. Both valve 30 and throttle valve 22 are operatively connected to the engine ECU so that their angular positions can be controlled by the ECU taking into account various engine parameters such as the amount and timing of the injected fuel, ignition timing, throttle position, position of an exhaust gas recirculation valve 36 which regulates recirculation of exhaust gases, and so on. By (partially) closing the butterfly valve 30, the area of the channel section in which the valve 30 is disposed is narrowed so that the velocity of air through the section 26 is increased.

[0036] A further measure to improve the efficiency, i.e. to lower the fuel consumption, is to let the engine run with as little throttling as possible. Throttling a combustion engine will increase both the pumping losses and fuel consumption. Due to the above-mentioned increased velocity by partially closing section valve 30, a proper mixture build up in the combustion chamber 2 and consequently an efficient combustion after ignition can be obtained, while the losses due to throttling are reduced. Inert recirculated exhaust gas which cannot take part in combustion but does reduce the pumping losses can still enter the combustion chamber via outer channel 28 after further opening recirculation valve 36.

[0037] The position of the exhaust recirculation valve 36 in combination with butterfly valve 30 as described above produces an engine that can breathe freely exhaust gases and fresh mixture through inner and outer channels 26, 28, respectively. This creates an ignitable mixture build-up during low to medium engine loads. The outer gas mixture is thereby obtained by mixing a certain amount of fresh air and a certain amount of recirculated exhaust gases.

[0038] Inlet valve 10 is substantially kidney-shaped, the concave edge of the kidney-shape being on the side of the spark plug 14 and the convex side is on the side of the cylinder wall 21. The kidney shape, more in particular the radii of the inner and outer edges, are designed such that the shape of the valve 10 is adapted to the diameter of the cylinder as is most clearly shown in figure 3. On the side of valve 10 facing the inlet manifold a plate-shaped protrusion which forms the guiding wall 38 is disposed along the centreline of the valve 10, which guiding wall 38 thereby effectively extends from the partition wall 24. The purpose of guiding wall 38 is to keep the inner and outer gas mixture flows in the respective inner and outer channels 26, 28 separated until they actually enter the combustion chamber 2 and to induce the swirling motion of said gases in the combustion chamber 2. As described above, this allows to obtain a variation of the gas mixture composition over the radial direction of the combustion chamber 2.

[0039] The subdivided inner and outer channels 26, 28, in combination with the throttle valve 22 and valve 30 make it possible to vary the amount and speed of the flow of fresh air (whether or not mixed with recirculated exhaust gases) into the combustion chamber 2 near the spark plug 14, as well as enable a variation over the radial distance from the centre towards the side wall of the cylinder. The kidney-shaped inlet valve 10 results in a high degree of air swing control into the combustion chamber 2 i.e. more swirl with less pressure loss compared with a normal round valve.

[0040] The specific use of the injectors 15 and 16 makes it possible to operate the engine sequentially. This means that part of the fuel is indirectly injected during the intake stroke with injector 15. Depending on the injected amount this results in an homogeneous mixture (lambda =1) in a more central part of the combustion chamber 2, whereas the outer rim of the combustion chamber 2 can be filled with inert exhaust gas, thereby effectively reducing the volume of the combustion chamber 2 and causing the engine to run more efficiently, at least for lower loads.

[0041] This is the same (homogeneous) situation as with medium and high load of the engine. The directly injected fuel with injector 16 during the compression stroke just before ignition acts a pilot burner for the indirectly inject fuel from injector 15 and results in an on average stochiometric mixture (i.e. λ = 1). The other way around must also be possible. Injecting a fixed amount fuel directly with injector 16 at the right degrees before TDC and regulating an the on average stochiometric mixture (i.e. λ = 1). with indirect injector 15.

[0042] Exhaust gases can be recirculated back into the inner and outer channels 26, 28 through the inner and outer recirculation channels 39, 34 by controlling the respective controllable recirculation valves 37, 36. The second embodiment, as shown in figure 5, is identical to the first embodiment of figures 1 -4, but comprises, additionally to the outer recirculation channel 34, also an inner recirculation channel 39 that allows for also recirculating exhaust gases to the inner channel 26. The exhaust gases are to be cooled down, which is easily achieved by letting part of the exhaust gas run from the muffler at the back of the car to a plenum chamber at the front before entering the inner and / or outer channels 26 and / or 28. Recirculation control valves 36 and 37 can be fitted on this plenum chamber. When the recirculated exhaust gases enter into the combustion chamber, an outer ring of relatively cool inert gases can be realised. For a turbo charged engine an EGR cooler will be beneficial for this purpose.

[0043] In the engine according to the present invention it is possible to create a combustible mixture varying along the radial direction of the combustion chamber 2. A centre zone M1 close to the centrally mounted spark plug is to comprise a rich mixture (λ < 1) that is surrounded by a stochiometric zone M2 comprising a fuel / gas mixture having that is substantially stochiometric, which in turn is surrounded by a third zone that comprises a lean mixture M3, surrounded an outer zone of fresh air and / or recirculated exhaust gases M4; the outer zone is, at low loads, preferably formed by inert gas mixture comprising substantially only recirculated exhaust gases. Typically, the boundaries between the respective zones will not be absolute and / or distinct as some mixing of the zones will occur at these boundaries. The size of the zones will typically vary with the loading regime wherein the engine operates. The quality of combustion may then vary with the relative percentages of the various mixtures M1 - M4 in the combustion chamber 2 as a whole. Also at lower loads the combustion chamber 2 is to be filed, on average, with a substantially stochiometric mixture; the exact amount of recirculated gas on top of the amount of air / fuel mixture will provide for that.

[0044] Figures 8 and 9 provide a illustrative example of an (artificial) division of the zones M1 - M4 at two different loading conditions. In figure 8, a lower load is requested from the engine, such that the stochiometric zone M2, comprising a fuel / air mixture originating from the inner channel 16 (wherein the fuel is provided by the indirect injector 15), is smaller in comparison to the stochiometric zone M2 of figure 9, as in figure 9 the engine operates at a higher load level, such that more fuel is required in the combustion chamber 2. In such cases, in might be that more fuel is also directly injected, further reducing the λ in the centre zone M1. The outer zone M4 may then comprise a higher percentage of fresh air (versus recirculated exhaust gases) in order to balance the overall fuel / air ratio in the combustion chamber 2.

[0045] Depending on the load and speed of the engine, in the combustion chamber prior to ignition of the centrally placed spark plug, different situations can be distinguished. Steady idling can be achieved by properly controlling the throttle valve 22, outer channel valve 30 and / or outer recirculation valve 36 and adjusting the amount of fuel according to a predefined target λ.

[0046] Idling or low loads: a small amount of combustible mixture in the centre of the combustion chamber throttle valve 22 nearly closed. In this situation outer channel valve 30 is closed and outer recirculation control valve 36 is opened as much as needed to maintain a steady combustion. Large quantities of recirculated inert gas will enter the combustion chamber. Fuel will come from direct injector 16.

[0047] Low loads: throttle valve 22 is opened further: a larger amount of combustible mixture in the centre zone M1, surrounded by fresh mixture and recirculated exhaust gases. In this case outer channel valve 30 is slightly more opened and outer recirculation control valve 36 is again opened as much as needed to maintain a steady combustion. For some light loads injector 15 and inner recirculation control valve 37 together with outer recirculation control valve 36 must work simultaneously to arrive at a proper λ.

[0048] Medium loads: an even larger amount of rich combustible mixture in the centre zone M1, surrounded by a lean mixture. In this case outer channel valve 30 opens further and outer recirculation control valve 36 will close gradually. Petrol to be injected indirectly and directly.

[0049] Medium to high loads: a larger amount of combustible mixture in the centre zone M1, surrounded by a relatively smaller amount of inert exhaust gas. As a whole the mixture, as seen in the radial direction, will become more and more homogeneous. Throttle valve 22 and outer channel valves 30 are opened even further and outer recirculation control valve 36 is closing while maintaining a proper combustion.

[0050] High loads: the whole combustion chamber 2 will be filled with a substantially homogeneous (stochiometric) mixture, wherein the outer zone M4 will be minimal, and large amounts of fuel are fed to the combustion chamber 2. Throttle valve 22 and outer channel valve 30 are fully opened, while outer recirculation control valve 36 is closed. The engine will run under a heavy load (near or almost at maximum torque).

[0051] The internal combustion engine can controlled by an ECU (engine control unit). The control parameters on the basis of which the ECU can control the internal combustion engine can be, for instance, determined by mapping the engine on an engine test bench. The result of which could be that, for different outside temperatures and pressures, look-up tables (i.e. maps) are obtained with following data (i.e. operational parameters): position of each valve, pressure and temperature in each channel, amount of fuel injected, speed and load.

[0052] These calibration measurements can, for instance, start with a small (fixed) amount of fuel being injected directly with injector 16. Outer recirculation control valve 36 in outer channel will gradually be opened. Outer channel valve 30, that controls the intake of fresh air in outer channel 28 is closed. The engine will thereby (initially) get its combustible mixture through the inner channel 26. For tested load case (determined, for instance, by delivered power, torque and rotational speed), the best ratio between direct injection 16 and indirect 15 injection will be established and the results will be added to a look-up table (i.e. map) in the ECU. Adjusting the pressure of direct injection could be another variable.

[0053] Altogether this creates, for lower loads and speed, the necessary data for the positions of the throttle valve 22 and the ratio between the fuel provided by the indirect 15 and direct fuel injectors 16. By opening throttle valve 22, while outer channel valve 30 is closed and outer recirculation control valve 36 is fully open, the engine can obtain its maximum power with a combustible mixture through the inner channel 26 only. Throttle losses can be diminished by opening / closing outer recirculation control valve 36; this will be reflected in a respective lower / higher specific fuel consumption. The combustible mixture that enters the combustion chamber 2 comes from the direct injector 15, recirculation of exhaust gases (by controlling outer recirculation control valve 36) and fresh air by controlling throttle valve 22. On top of this, the directly injected fuel near the sparkplug, plus the non-combustible (i.e. inert) recirculation gases through the outer channel 34 encircling the (richer) mixture in the centre of the combustion chamber 2, enable a steady combustion. The ECU will be filled with data tables for all these circumstances (i.e. different load case scenarios).

[0054] As the power demand goes up, more fresh air is needed (such that the throttle valve 22 is moved towards a more open position) and recirculation to the inner channel 26 (through inner recirculation channel 39) must decrease by closing inner recirculation control valve 37. If even more power is required outer channel valve 30 in the outer channel 28 will be opened. Outer recirculation control valve 36 can now be closed as well until outer channel valve 30 is fully open, Instead of relying on recirculation gases the engine can now breath fresh air through both the inner and outer channels 26, 28. Consequently the engine can now deliver more power since more fuel can be injected. If even more fuel needs to be injected to arrive at the desired power (and keep λ=1 ), this can be accomplished either by indirect injection or by direct injection.

[0055] Table 1 gives one example what a table in the ECU will look like. Eventually after more tests on the test bed and kms on the road the ECU will contain hundreds / thousands of tables. The ECU could comprise a self-learning module in order to optimize its performance during use.Pressure at sea altitude, 20 degr C

[0056] Table 1.Valveinjector223036371516position open ; %idle205502low load150100801015medium load501050604020full load100100009010

[0057] The engine on the calibration testbed will give the answers for optimum results with minimum throttle losses and maximum fuel efficiency, while maintaining λ=1. Eventually outer channel valve 30 and throttle valve 22 will be fully open and the engine can deliver its full potential. Recirculation valves 36 and 37 will then be closed. The optimum ignition timing for the entire speed / power range can be established during the tests on the test bed and then added to maps in the ECU, as is typically performed for programming ECUs.

[0058] It is noted that the different zones M1 - M4 can be effectively obtained due to the guiding wall 38 arranged on the inlet valve 10, as it guides the different incoming gas mixtures to move in a swirling fashion substantially parallel (i.e. substantially tangential) to the cylinder wall 21. Mixing between the respective zones, before the overall mixture is ignited using the spark plug 14, is thereby prevented as much as possible.

[0059] Figure 6 shows, in the simplified schematical top view a third embodiment of the internal combustion engine. The third embodiment is substantially identical to the second embodiment of figure 5, wherein an exhaust gas processing system 71 is arranged downstream of the outlet manifold 7. The exhaust gas processing system 71 is arranged for removing unwanted substances from the exhaust gas, such as particulates and NO x and preferably comprises a particle filter 72 and / or a catalytic converter 73 for removing said unwanted substances. The inlet(s) 391, 341 of the respective inner and / or outer recirculation channels 39, 34 may be arranged downstream of the exhaust gas processing system 71, such that relatively clean recirculation gasses are fed back into the combustion chamber 2, thereby preventing contamination and performance degradation of the internal combustion engine. As such a The exhaust gas processing system 71 is typically a part of the exhaust system, that stretches for a certain length, the exhaust gasses are also given the time to cool down before entering the respective inner and / or outer channels 26, 28, which is beneficial for the performance of the engine.

[0060] The size of the inner and outer channel 26, 28 of the engine depends on the design speed and torque the engine has to deliver. The maximum air speed in both respective channels preferably does not exceed 50 m / s. A skilled person is able to calculate, on the basis of the speed, stroke and bore of the engine, the respective size of the channels.

[0061] Figure 7 shows, in a schematical cross-sectional vies, the kidney-shaped inlet valve 10. The inlet valve 10 is held by the valve stem 11 which is movably held in the cylinder head in order to allow for a longitudinal movement of the inlet valve 10 between an open position, wherein the combustion chamber 2 is in open fluid connection with the inlet manifold 20 for allowing a gas mixture to enter the combustion chamber 2 during the intake stroke. The inlet valve 10 comprises a flat guiding surface 13 facing towards the inlet port 4 and the guiding wall 38 protrudes from the guiding surface 13 in the direction of the inlet port 4. In the example shown here, one part 131 of the guiding surface 13 is elevated with respect to the remainer of the guiding surface 13. The one part 131 may be arranged with respect to the part of the inlet valve 10 corresponding to the inner or outer channel 26, 28. Although the inlet valve 10 is shown, when in a closed position, to sit on top of the top wall 3, it may also be arranged to sit in the top wall 3, such that a substantially flush arrangement of the top wall 3 and inlet valve 10 is obtained in the closed position of the inlet valve 10. The outlet valve 12 may be arranged in a similar fashion in the top wall 3.

[0062] All the hereabove presented embodiments, and the individual features thereof, may be combined for forming further embodiments. Additionally, the present invention is not limited to the embodiments shown, but also extends to other embodiments falling within the scope of the appended claims.

Claims

1. Internal combustion engine, said engine comprising: - at least one cylinder defining a combustion chamber, said cylinder comprising a cylindrical wall and an end wall limiting the cylinder in a longitudinal direction at a first longitudinal position of said cylinder, said end wall comprising: - an inlet port for feeding a gas mixture to said cylinder and an inlet valve that is moveable for opening and closing the inlet port, - an outlet port for discharging exhaust gas from said cylinder; - preferably, a fuel injector for injecting fuel into the cylinder, and - a spark plug that is centrally arranged in the end wall; - a piston disposed in said cylinder, wherein a head of said piston limits the cylinder in a longitudinal direction at a second, adjustable longitudinal position of said cylinder, said piston being moveable to reciprocate between a top position relatively close to the end wall and a bottom position at a greater distance from the end wall; - an inlet manifold connected to the inlet port for feeding the gas mixture to the cylinder via the inlet port, preferably wherein an indirect fuel injector is arranged in the inlet manifold for supplying fuel to the gas mixture; - wherein said inlet valve comprises a substantially flat guiding surface, preferably having a rounded and / or chambered edge, facing towards the inlet port and a guiding wall protruding from the guiding surface in the direction of the inlet port, said guiding wall being substantially curved in a longitudinal direction thereof, and said guiding wall being arranged such that it is curved in substantially the same direction as the cylindrical wall, such that said inlet valve is arranged for guiding the gas mixture in a direction substantially parallel to the end wall and having a largest component that is substantially tangential to the cylindrical wall.

2. Internal combustion engine according to claim 1, wherein the inlet manifold comprises a partition wall dividing the inlet manifold into an outer and inner channel, and wherein the guiding wall of the inlet valve is substantially aligned with the partition wall of the inlet manifold, such that an outer gas mixture fed to the cylinder via the outer channel of the inlet manifold is guided by an outer surface of the guiding wall and an outer part of the guiding surface and an inner gas mixture fed to the cylinder via the inner channel of the inlet manifold is guided by an inner surface of the guiding wall and an inner part of the guiding surface, wherein the outer surface is facing towards the cylindrical wall and the inner surface is facing towards a centre of the cylinder and wherein the outer part is closer to the cylindrical wall than the inner part, in particular wherein the indirect fuel injector is arranged in the inner channel of the inlet manifold.

3. Internal combustion engine according to claim 2, wherein the inlet manifold comprises one or more controllable inlet valves for independently controlling flows of fresh air to the outer and inner channels, in particular wherein a respective controllable inlet valve is movable between a fully closed state, wherein the respective controllable inlet valve blocks any fresh air from passing the respective controllable inlet valve, to a fully open state, wherein the controllable inlet valve allows for a maximum of fresh air to pass the controllable inlet valve.

4. Internal combustion engine according to claim 2 or 3, wherein the guiding wall is arranged such that, when the inner and outer gas mixtures are fed to the cylinder, it forces the outer gas mixture to encircle and enclose the inner gas mixture in the cylinder.

5. Internal combustion engine according to any of the preceding claims, comprising a recirculation system for recirculating part of the exhaust gas as recirculated exhaust gas to the outer and / or inner channel, in particular wherein the recirculation system comprises a gas conduit system for guiding the recirculated exhaust gas from an exhaust side of the internal combustion engine that is located downstream of the outlet port to the outer and / or inner channel; preferably, wherein the recirculation system is arranged for controlling the amount(s) of exhaust gas that is / are recirculated to the outer and / or inner channel, in particular wherein said recirculation system is configured for independently controlling the amounts of recirculated exhaust gas to the inner and outer channels.

6. Internal combustion engine according to claim 5, wherein said recirculation system is controllable by means of one or more controllable recirculation valves, in particular wherein the one or more controllable recirculation valves are movable from a fully closed state, wherein a respective controllable recirculation valve blocks any exhaust gas from recirculating to the outer and / or inner channel, to a fully open state, wherein the controllable recirculation valve allow for a maximum of exhaust gas to be recirculated as recirculated exhaust gas to the outer and / or inner channel.

7. Internal combustion engine according to claim Fout! Verwijzingsbron niet gevonden. or 6, wherein said internal combustion engine comprises, downstream of the outlet port, an exhaust gas processing system for removing unwanted substances from the exhaust gas, preferably comprising a particle filter and / or a catalytic converter, and wherein the recirculation system is arranged for recirculating exhaust gases that have been processed by the exhaust gas processing system.

8. Internal combustion engine according to any of the preceding claims, wherein the gas mixture is a mixture of air, fuel and recirculated exhaust gas.

9. Internal combustion engine according to any of the preceding claims, wherein at least the guiding surface of the inlet valve is non-round, in particular elongated and preferably kidney-shaped having its curvature in substantially the same direction as the guiding wall; preferably, wherein the non-round guiding surface comprises an inner side edge and an outer side edge, wherein the outer side edge faces the cylindrical wall and is arranged closer to the cylindrical wall than the inner side edge, wherein the outer side edge is substantially convex and the inner side edge is substantially concave; and preferably, wherein said guiding wall is arranged substantially in the middle between the inner side edge and an outer side edge; preferably, wherein an inlet port recess is shaped correspondingly to the inlet valve.

10. Internal combustion engine according to any of the preceding claims, in particular claim 2 or 9, wherein one of the inner part and the outer part of the guiding surface is elevated with respect to the other of the inner part and the outer part of the guiding surface for altering the inlet time of the inner channel with respect to the outer channel, or vice versa.

11. Method of operating an internal combustion engine according to any of the preceding claims, comprising the steps of, in any suitable order: - controlling a flow of a gas mixture through the inlet manifold into the combustion chamber, in particular during an inlet stroke of the internal combustion engine; - injecting fuel in the inner channel of the inlet manifold and / or injecting fuel directly into the combustion chamber using the direct fuel injector, in particular during, preferably in a final stage of, a compression stroke of the internal combustion engine for obtaining an air / fuel mixture in the combustion chamber; and - igniting the air / fuel mixture using the spark plug during the ignition event.

12. Method according to claim 11, wherein said internal combustion engine is preferably the engine according to at least claim 2, wherein the step of controlling a flow of a gas mixture comprises: - controlling, during the intake stroke of the engine, flows of the inner and outer gas mixtures through the inlet manifold such that, at least in a state prior to the direct injection of fuel into the combustion chamber, the combustion chamber holds the inner and an outer gas mixture, wherein the inner gas mixture is encircled and enclosed by the outer gas mixture, wherein said inner gas mixture has a different composition than the outer gas mixture.

13. Method according to claims 11 or 12, wherein the internal combustion engine comprises the recirculation system for recirculating part of the exhaust gas as recirculated exhaust gas to the outer and / or inner channel, wherein the method comprises controlling the exhaust gas recirculation system for controlling the composition of the inner and / or outer gas mixture such that the inner gas mixture has a different composition than the outer gas mixture.

14. Method according to claims 12 of 13, wherein, - the inner gas mixture, at least in a state prior to directly injecting fuel into the combustion chamber using the direct fuel injector and in particular under load conditions in between idle and full load, comprises a higher volumetric percentage of fuel than the outer gas mixture, preferably wherein the outer gas mixture comprises no fuel; and / or - in particular under load conditions in between idle and full load, the inner gas mixture comprises a higher volumetric percentage of oxygen than the outer gas mixture; and / or - in particular under load conditions in between idle and full load, the outer gas mixture comprises a higher volumetric percentage of recirculated exhaust gases.

15. Method according to any of the preceding claims 11 - 14, wherein said internal combustion engine is controlled, in particular under load conditions in between idle and full load, such that, during the intake stroke, a lean gas mixture, preferably comprising no fuel, is supplied through the outer channel and a substantially stochiometric gas mixture is supplied through the inner channel and wherein, after directly injecting fuel into the combustion chamber using the direct fuel injector, an overall gas mixture is obtained that is substantially stochiometric.

Images