Method and preparation device for preparing a liquid fuel for a combustion cycle of an internal combustion engine

Abstract

A method for preparing a liquid fuel for a combustion cycle in an internal combustion engine (8). In this method, the liquid fuel is introduced into a container (2) of a preparation apparatus (1) at a first pressure and a first temperature. The container (2) expands to turn the fuel into a gaseous state and applies heat to the fuel. The container (2) contracts to increase the pressure therein while maintaining the fuel in a gaseous or supercritical phase. The fuel is then injected from the container (2) to be further introduced into the combustion chamber (8b) of the internal combustion engine (8). A corresponding preparation apparatus (1) is also described.

Description

Technical Field

[0001] This disclosure relates to internal combustion engines, and more specifically to the preparation of liquid fuels for combustion cycles in internal combustion engines. The invention also relates to an apparatus for preparing such engines. Background Technology

[0002] One way to supply liquid fuel to the combustion chamber of an internal combustion engine (often referred to as port injection) is to introduce the liquid fuel as an atomized spray into the intake manifold (i.e., a cylinder-specific portion of the intake flow path). The atomized liquid fuel further evaporates and mixes with air within the intake manifold, and this fuel-air mixture is then directed into the combustion chamber.

[0003] Due to the pressure drop as it exits the injector nozzle, and as smaller fuel particles become more exposed to the airflow and heat within the intake passage, some of the liquid fuel evaporates, causing a drop in temperature within the intake passage. This temperature drop is common for alcohol-based and amino-based fuels, even to the point where it can adversely affect subsequent combustion processes in the combustion chamber. This temperature drop is particularly prevalent with methanol fuels. If these effects prevent proper atomization and evaporation of the fuel within the intake passage, any fuel that reaches the combustion chamber in liquid form will suffer from larger droplets, impacting the combustion process and potentially causing lubrication problems.

[0004] Potential problems associated with liquid fuels include, for example, the buildup and / or condensation of fuel droplets on the combustion chamber liner walls, which can lead to uneven distribution of the fuel mixture within the combustion chamber and thus degrade combustion events. For alcohol-based and amino fuels, particularly methanol, another adverse effect is that such buildup and / or condensation can wash the lubricating film away from the combustion chamber liner walls, resulting in excessive wear and / or lubricant contamination. Summary of the Invention

[0005] The purpose of this invention is to provide a method and apparatus for preparing liquid fuels to overcome the above-mentioned deficiencies.

[0006] The object of this invention is achieved by a method and apparatus characterized by the features described in the independent claims. Preferred embodiments of this disclosure are disclosed in the dependent claims.

[0007] This disclosure is based on the idea of ​​preparing liquid fuel by introducing it into a variable-volume container before mixing it with the engine's main air charge. The variable-volume container then expands, causing the fuel to be in a gaseous phase. Heat is applied to the fuel, and the container contracts again to achieve pressure sufficient for fuel injection. Due to the heat addition, the fuel remains in a gaseous phase (or even a supercritical phase) even when the container contracts. This allows fuel that is initially in a liquid phase to be introduced into the combustion chamber in a gaseous and / or supercritical phase.

[0008] This invention can be used in conjunction with inlet injection, i.e., injecting fuel prepared in a gaseous and / or supercritical state into the inlet channel, where the fuel mixes with pressurized air and is transferred to the combustion chamber. The advantage of this method is that the injection pressure can be kept low due to the lower pressure present in the inlet channel. Inlet injection also provides more time for the mixing and formation of a homogeneous combustible fuel / air mixture.

[0009] This invention can also be used in conjunction with direct injection, where fuel is injected directly into the combustion chamber. A major challenge in this method is the need for higher injection pressures to overcome the higher in-cylinder pressures. The benefit is that the injection is concentrated into more space within the combustion chamber, potentially causing stratification of the air-fuel mixture. A stratified mixture is a situation where fuel is concentrated in a specific portion of the combustion chamber while the rest of the mixture is relatively lean. This stratification of the mixture can improve combustion efficiency, reduce emissions, and enhance overall engine performance, especially under certain operating conditions, such as partial load or low speed conditions with a lean mixture.

[0010] Another possibility is to use the invention in conjunction with pre-combustion chamber fuel injection, wherein the pre-combustion chamber, which is in fluid communication with the main combustion chamber, receives fuel charge and helps to form and ignite the mixture in the main combustion chamber.

[0011] This invention offers several advantages; for example, providing a pristine liquid fuel in the gas phase effectively minimizes fuel buildup and / or condensation on the walls along the fuel flow path. This, in turn, minimizes problems associated with the flushing of the lubricating film and / or degradation of combustion events.

[0012] Furthermore, because less consideration is needed to prevent fuel buildup on the walls, the location and orientation of the injection points can be constructed more freely.

[0013] According to a first aspect of this disclosure, a method for preparing a liquid fuel for a combustion cycle in an internal combustion engine is provided.

[0014] The method includes the step of introducing a predetermined amount of liquid fuel at a first pressure and a first temperature into a container of a preparation apparatus, the container defining a first container volume. The first pressure and first temperature establish a first thermodynamic state of the fuel within the container.

[0015] The method also includes the step of expanding the container to define a second container volume greater than the first container volume. This causes the fuel to enter a second thermodynamic state defined by a second pressure and a second temperature, where the second pressure is lower than the first pressure. Notably, the second thermodynamic state corresponds to the gaseous phase of the fuel. That is, the expansion of the container volume is sufficient to reduce the dominant pressure within the container to a level where the fuel is in the gaseous phase or begins to transition into the gaseous phase.

[0016] It should be noted that the step of introducing liquid fuel can precede or coincide with the step of expanding the container. The step of expanding the container can even begin before the step of introducing liquid fuel. However, the step of expanding the container continues until the previously introduced liquid fuel is in the gaseous phase or begins to convert to the gaseous phase. It is worth noting that the expansion of the container can continue further.

[0017] The method also includes the step of applying heat to the fuel. This step of applying heat may be provided as a separate, independent step, consistent with other method steps, or even as a sequential step. The effective phase used to transfer heat to the fuel overlaps with or follows the transition of the fuel to a second thermodynamic state. In any case, heat is applied to the fuel at least when it is in a gaseous state (i.e., when the container defines a second container volume).

[0018] The method also includes, once heat has been applied or continues to be applied to the fuel (appropriately in gaseous form), contracting the container to define a third container volume smaller than the second container volume. This causes the fuel to enter a third thermodynamic state defined by a third pressure higher than the second pressure and a third temperature higher than the first temperature. It is noteworthy that this third thermodynamic state corresponds to the gaseous or supercritical phase of the fuel. That is, due to the addition of heat, at least in the gaseous phase, the fuel will not revert to a liquid state even if the pressure is increased by contracting the container volume.

[0019] Preferably, but not necessarily, the volume of the third container is equal to or less than the volume of the first container.

[0020] Preferably, but not necessarily, the third pressure is equal to or higher than the first pressure.

[0021] Finally, fuel is injected from the container in a gaseous or supercritical state for further introduction into the combustion chamber of the internal combustion engine. The fuel injection step can be performed as a separate, independent step or concurrently with the container shrinkage step (appropriately during its final stage).

[0022] The discharge of fuel in a gaseous or supercritical state allows for more flexible positioning of the container; that is, the container can be attached, for example, to the intake manifold or cylinder head, or have a separate fluid communication line for supplying fuel at a distance from it.

[0023] Preferably, but not necessarily, fuel is injected from the container into the intake passage of the associated combustion chamber via a separate injector and / or via an outlet valve of a preparation device integrated into the container, or even directly into the combustion chamber.

[0024] In the context of this disclosure, the term intake passage is used to describe a portion of the intake flow path specific to the combustion chamber to which it leads. For example, an intake passage may include an intake port formed on the cylinder head and any additional intake passages extending between the intake port and a common inlet passage (such as a boost air receiver). Furthermore, in the context of this disclosure, the term combustion chamber is used to describe the main chamber (i.e., the combustion volume defined between the piston top, cylinder wall, and cylinder-facing portion of the cylinder head) and, where applicable, the pre-combustion chamber (which is typically formed within or connected to the cylinder head).

[0025] In an embodiment according to the first aspect, the method may further include the step of introducing a gaseous medium into the container during or before container expansion. The gaseous medium improves fuel dispersion and is inherently compressible, which is beneficial for container expansion (compared to an arrangement in which no gaseous medium is introduced into the container).

[0026] The introduction of the gaseous medium can precede, or be partially preceded, the introduction of the liquid fuel, but alternatively, they can be carried out simultaneously.

[0027] Preferably, but not necessarily, the gaseous medium is air or nitrogen. For example, air can be provided as ambient air or compressed air, such as booster air. Another example of a suitable gaseous medium would be exhaust gas recirculation (EGR). Furthermore, the gaseous medium can be provided as any of the aforementioned mixtures. The introduced gaseous medium can be at ambient temperature or preheated. Additionally, if the gaseous medium contains an oxidizer, it is introduced in an amount insufficient to produce a combustible mixture. That is, the gaseous medium is provided in such a small amount that spontaneous combustion within the container volume does not occur.

[0028] In an embodiment according to the first aspect, fuel can be injected from the container by opening a dedicated outlet valve attached to the container's outlet. This dedicated outlet valve is suitably arranged in fluid communication with the inlet passage of the associated engine, but may also be arranged in fluid communication with an injector configured for direct injection into the combustion chamber or pre-combustion chamber.

[0029] Alternatively or additionally, fuel can be injected from the container by opening an injector valve located away from the remaining preparation device. Suitablely, such an injector valve is arranged in fluid communication with the outlet and attached to the inlet passage of the associated combustion chamber, or directly connected to the combustion chamber or pre-combustion chamber.

[0030] In other words, the outlet valve, provided as a dedicated outlet valve or as an injector, can be directly connected to the outlet, i.e., integrated with the preparation apparatus. Alternatively, the container outlet can be connected to an injector located away from the preparation apparatus via a dedicated supply line, in which case a dedicated outlet valve connected to the container outlet may or may not be provided.

[0031] In an embodiment according to the first aspect, fuel from the preparation device is introduced into the combustion chamber via an inlet passage associated with the combustion chamber (i.e., intake port injection). This has the advantage that the pressure at which fuel is injected from the container only needs to exceed the dominant pressure in the inlet passage. Furthermore, by timing the introduction of fuel into the combustion chamber by opening and closing the inlet valve of the combustion chamber, the timing dependence of fuel preparation relative to the combustion cycle (i.e., the degree of synchronization between the two) is reduced.

[0032] Alternatively, fuel from the preparation device can be directly introduced into the combustion chamber (i.e., the main chamber or pre-combustion chamber) using an injector, with the opening and closing of the injector regulating the timing of the introduced fuel. For example, the fuel can be introduced during the intake stroke of the combustion chamber. In this case, the fuel is appropriately injected as ignition fuel for pre-conditioning the combustion chamber before the introduction of the main fuel. In another example, fuel from the preparation device can be introduced during the compression stroke of the combustion chamber as ignition fuel (appropriately during the initial phase of the compression stroke) or as main fuel (appropriately during the later phases of the compression stroke). It is noteworthy that when fuel is introduced during the compression stroke, the preparation device is advantageously adapted to generate a pressure exceeding the dominant pressure within the combustion chamber during the compression stroke (typically approximately 50-120 bar).

[0033] In an embodiment according to the first aspect, the predetermined amount of liquid fuel corresponds to a portion or all of the fuel charge to be burned in the combustion chamber of the associated engine during a single combustion cycle.

[0034] In other words, the liquid fuel is not prepared in excess or in large quantities, but in batches corresponding to the amount or portion of the liquid fuel in question burned in a single combustion cycle in a combustion chamber associated with the preparation device (or, if multiple container volumes are provided for a single preparation device).

[0035] Alternatively, the liquid fuel may not be prepared in a way that directly corresponds to the amount or portion of the fuel burned within a single combustion cycle. In this case, the fuel is appropriately injected into a buffer, from which it is further introduced into the combustion chamber or even multiple combustion chambers. Suitablely, the size of such a buffer can be set to maintain the amount of fuel required for a relatively short time period (e.g., 1 to 60 seconds) corresponding to a limited number of combustion cycles. Such a buffer also reduces the timing dependence of the preparation device relative to the combustion cycle of the associated engine and helps to compensate for variations in fuel consumption between successive combustion cycles and / or different combustion chambers.

[0036] As an alternative, fuel can be injected from a container to be stored in a preparation reservoir, from which it is further introduced into the combustion chamber or even multiple combustion chambers. In contrast to the dampers discussed above, such a preparation reservoir allows the associated engine to run with the fuel it contains for a much longer period than a damper would allow.

[0037] It should be noted that such a buffer or preparation reservoir may be provided even when the amount or portion of the liquid fuel in question burned in a single combustion cycle of the combustion chamber associated with the preparation device is correspondingly prepared in batches.

[0038] In embodiments according to the first aspect, fuel from the preparation device can be introduced into the combustion chamber for combustion as the main fuel. Alternatively or additionally, fuel from the preparation device can be introduced into the combustion chamber for combustion as an ignition fuel. In the context of this disclosure, the term ignition fuel should be understood as a separately introduced portion of the fuel charge intended to ignite the main fuel or pretreat the mixture in the combustion chamber to improve the combustion of the main fuel. Another option is to use the preparation device to introduce fuel specifically designed for low-load or low-speed engine operation, where ignition and / or combustion processes may be more challenging than at full load and / or nominal speed. Therefore, the present invention can be used for fuel delivery of main fuel portions, ignition fuel portions, or special mode fuel portions.

[0039] In the embodiments disclosed in the first aspect, fuel from the preparation device can be introduced into the combustion chamber for combustion as a premixed combustion charge or a portion thereof, suitably as its main fuel or ignition fuel. Injection via the inlet channel and direct injection into the combustion chamber are both possible options for introducing said fuel for combustion as a premixed combustion charge or a portion thereof.

[0040] Alternatively, fuel from the preparation device can be introduced into the combustion chamber to burn as part of the diffusion combustion charge, suitably as its ignition fuel component. Injection via the inlet channel and direct injection into the combustion chamber are both possible options for introducing the fuel to be burned as an ignition component of the diffusion combustion charge. In the case of direct injection for introducing the ignition fuel component of the diffusion combustion charge, the ignition fuel component is suitably introduced during the intake stroke or compression stroke (preferably its initial phase).

[0041] In embodiments according to the first aspect, the liquid fuel comprises an alcohol or ammonia. As previously stated, the benefits covered by this disclosure are more pronounced for alcohol-containing liquid fuels. Preferably, but not necessarily, the liquid fuel comprises methanol, in which case the benefits covered by this disclosure are particularly pronounced.

[0042] It should be noted that the first aspect of this disclosure covers any combination of two or more embodiments or variations thereof as described above.

[0043] According to a second aspect of the invention, an apparatus for preparing liquid fuel for an internal combustion engine is provided. The apparatus includes a container, a fuel inlet valve configured to selectively introduce liquid fuel into the container, and an outlet configured to inject fuel from the container in a gaseous or supercritical phase. The fuel inlet valve may advantageously be connected to a fuel supply line, and may selectively introduce fuel from the fuel supply line into a chamber.

[0044] Furthermore, the container is configured as a variable-volume container. Preferably, this is achieved by providing the preparation apparatus with a displacement element connected to the container, such that the displacement element defines or, together with the container, defines a variable container volume within the container. For example, the displacement element may be configured as a plunger movably arranged within the container between the end positions of a plunger to define the variable container volume. Alternatively or otherwise, other types of displacement elements, such as other reciprocating or rotating elements, may also be used.

[0045] The preparation apparatus also includes a heater device for applying heat to the fuel within the container. For example, the heater device may include an electric heating element arranged to be connected to and suitably integrated therein with a displacement element. Alternatively or additionally, the heater device may include an electric heating element arranged around the container, suitably integrated within or around the wall forming the container. Alternatively or additionally, the heating device may include a heated fluid conduit for guiding heated fluid through it, the heated fluid conduit being arranged around the container. Such a heated fluid conduit may advantageously be configured to guide exhaust gas through it in order to suitably provide heat exchange between the exhaust gas and the fuel within the container via the container wall. Furthermore, the heated fluid conduit may be configured to use any other waste heat source generated by an engine or any nearby equipment in the ship or plant.

[0046] It is worth noting that the preparation apparatus is advantageously configured such that the method according to the first aspect can be performed therewith.

[0047] For example, the fuel inlet valve can advantageously be electromechanically operated using an associated solenoid. Advantageously, the fuel inlet valve can be arranged to be actuated under the control of the engine's electronic control unit (ECU) or a subunit therein. Alternatively, the fuel inlet valve can be mechanically operated, for example, by being spring-biased toward a closed position and also configured to open under the pressure difference between the fuel supply line and the container during at least a portion of the expansion of the container (appropriately corresponding to the expected time period for fuel introduction). Another example of actuating the fuel inlet valve is by coupling it to the associated engine crankshaft or camshaft, for example, via one or more of a belt, chain, or cam mechanism, or via a hydraulic system.

[0048] In an embodiment according to the second aspect, the preparation apparatus further includes an inlet valve for introducing a gaseous medium into the container, wherein an outlet is further configured for injecting a mixture of fuel and gaseous medium in the gaseous or supercritical phase from the container. Most preferably, such an inlet valve is configured to selectively open and close fluid communication between the container and the supply of the gaseous medium.

[0049] For example, the inlet valve can advantageously be electromechanically operated using an associated solenoid. Advantageously, the inlet valve can be arranged to be actuated under the control of the engine's electronic control unit (ECU) or a subunit therein. Alternatively, the inlet valve can be mechanically operated, for example by being spring-biased toward a closed position and further configured to open under the pressure difference between the gas medium supply and the container during at least a portion of the expansion of the container (appropriately corresponding to the expected time period for the introduction of the gas medium). Another example of actuating the inlet valve is by connecting it to the associated engine crankshaft or camshaft, for example via one or more of a belt, chain, or cam mechanism, or via a hydraulic system.

[0050] In an embodiment according to the second aspect, the fuel inlet valve is further configured to meter a predetermined amount of liquid fuel. Suitably, the predetermined amount of liquid fuel corresponds to a portion or all of the fuel charge to be burned in the combustion chamber of the associated engine during a single combustion cycle.

[0051] Appropriately, this is achieved by changing the duration for which the fuel inlet valve remains open during container expansion.

[0052] In an embodiment according to the second aspect, the preparation apparatus further includes an outlet valve for selectively opening and closing fluid communication with the container via the outlet.

[0053] For example, the outlet valve can advantageously be electromechanically operated using an associated solenoid. Advantageously, the outlet valve can be arranged to be actuated under the control of the engine's electronic control unit (ECU) or a subunit therein. Alternatively, the outlet valve can be mechanically operated, for example, by being spring-biased toward a closed position and also configured to open under the pressure difference between the intake and outlet of the associated combustion cylinder and the container during at least a portion of the container's contraction (appropriately corresponding to the expected time period of fuel injection). Another example of actuating the inlet valve is by connecting it to the associated engine's crankshaft or camshaft, for example, via one or more of a belt, chain, or cam mechanism or via a hydraulic system.

[0054] For example, the outlet valve can be configured as a dedicated outlet valve attached to the outlet. Such a dedicated outlet valve is suitably arranged in fluid communication with the inlet passage of the associated engine, but it can also be arranged in fluid communication with the injector, which is arranged to be connected to the combustion chamber or pre-combustion chamber.

[0055] Alternatively or additionally, the outlet valve may be configured as an injector valve located away from the remaining preparation apparatus. In this case, the injector valve is suitably configured to communicate with the outlet fluid and preferably to be attached to the intake passage of the combustion chamber, or directly connected to the combustion chamber.

[0056] In other words, the outlet valve, provided as a dedicated outlet valve or as an injector valve, can be directly connected to the outlet, i.e., integrated with the preparation apparatus. Alternatively, the container outlet can be connected to the injector via a dedicated supply line, which is located away from the preparation apparatus. In this case, an additional dedicated outlet valve connected to the container outlet may or may not be provided.

[0057] In an embodiment according to the second aspect, the fabrication apparatus includes an electromechanical actuator for driving the shifting element. For example, such an electromechanical actuator can be configured as a solenoid device that drives the reciprocating shifting element (e.g., a plunger) to its end position. In this case, the reciprocating shifting element is suitably biased toward its relative end position. Naturally, other configurations for actuating the shifting element can be provided. For example, the shifting element in a variable-volume container can be electromagnetically, pneumatically, hydraulically, or movable using any type of mechanical servo mechanism capable of producing sufficiently rapid movement. Furthermore, the active movement of the shifting element can be arranged in two directions or only in one direction. When using a reciprocating shifting element and the active movement is arranged only in one direction, the return movement is preferably biased, for example, using a return spring. Advantageously, the shifting element is arranged to be actuated under the control of the engine's electronic control unit (ECU) or a subunit therein. Another example of actuating the shifting element is, for example, connecting it to the crankshaft or camshaft of the associated engine via one or more of a belt, chain, or cam mechanism.

[0058] It should be noted that the second aspect of this disclosure covers any combination of two or more embodiments or variations thereof as described above.

[0059] According to a third aspect of this disclosure, an internal combustion engine is provided. Specifically, the engine includes a fuel preparation device according to a second aspect of the invention. The fuel preparation device is associated with a combustion chamber of the engine and arranged to inject fuel for further introduction into the combustion chamber. As discussed above in conjunction with the foregoing aspects of this disclosure, fuel can be introduced into the combustion chamber via an inlet passage corresponding to the combustion chamber, or directly into the combustion chamber using an injector. An engine having multiple combustion chambers can naturally have multiple fuel preparation devices arranged accordingly. Alternatively, a single fuel preparation device can be associated with multiple combustion chambers. Furthermore, a buffer or fuel preparation reservoir can be provided in conjunction with the fuel preparation device, such that fuel from the fuel preparation device is transferred via the buffer or reservoir. Attached Figure Description

[0060] In the following, the present disclosure will be described in more detail with reference to the accompanying drawings and preferred embodiments, wherein...

[0061] Figure 1 A pV diagram representing an idealized preparation cycle according to an embodiment of the first aspect is schematically shown; Figure 2 The preparation apparatus of combining an internal combustion engine during the introduction of a gaseous medium into a container is schematically shown according to an embodiment of the second aspect; Figure 3 This schematically illustrates the process of introducing liquid fuel into the container and the container expansion. Figure 2 Preparation apparatus; Figure 4 This schematically illustrates the process of applying heat to the fuel. Figure 2 Preparation apparatus; Figure 5 The illustration schematically shows the process during container shrinkage. Figure 2 The preparation apparatus, and Figure 6 This schematically illustrates the process of fuel being discharged from the container. Figure 2 The preparation apparatus. Detailed Implementation

[0062] Figure 1 A pV diagram representing an idealized preparation cycle according to an embodiment of the first aspect is schematically shown. The horizontal axis (V) represents the container volume, while the vertical axis (p) represents the dominant pressure in the container. The preparation cycle is continuous and can be considered as starting from point a and running through points b, c, d, e, and f, with the cycle returning to point a from these points.

[0063] At point a, the container has a minimum volume, and it expands from this minimum volume up to point d. Then, the volume of the container contracts forward from point e until it reaches point a again.

[0064] Suitablely, during the transition from point a to point b, the gaseous medium is introduced into the container while the container expands. Suitablely, during the transition from point b to point c, liquid fuel is introduced into the container while the container expands. It should be noted that the introduction of the gaseous medium and fuel can alternatively be carried out in different orders, simultaneously, or overlapping.

[0065] Even when fuel and gaseous media are introduced between points a and d, the pressure inside the container decreases due to its expansion. Notably, this pressure drop causes the previously liquid fuel to become gaseous.

[0066] The transition between points d and e represents an increase in pressure within the container due to the introduction of heat, i.e., without causing the container to contract. It should be noted that heat can also be introduced at other points or even continuously.

[0067] The transition from point e to f represents an increase in pressure within the container primarily caused by the reduction in container volume during container contraction. However, due to the heat introduced during the cycle, the fuel remains in the gas phase (or even reaches the supercritical phase).

[0068] The transition between points f and a represents a further reduction in container volume during container contraction. When fuel is ejected from the container during this transition, the pressure does not increase significantly, regardless of container contraction.

[0069] Figure 2 A preparation apparatus 1 according to an embodiment of the second aspect, incorporating an internal combustion engine 8, is schematically shown. The preparation apparatus includes a container 2 in which a displacement element 6, serving as a movable plunger, is disposed.

[0070] A fuel inlet valve 3 is arranged to connect to container 2 to selectively introduce liquid fuel into the container. An inlet valve 4 is also provided to selectively introduce a gaseous medium into container 2. Furthermore, an outlet valve 5a is configured to connect to container 2 to selectively open and close fluid communication with container 2 via outlet 5.

[0071] The shifting element 6 is equipped with an actuator 6a configured to drive the shifting element 6 between its end positions. Furthermore, the shifting element 6 is also equipped with a heater assembly 7 integrally disposed with the shifting element 6. For example, the heater assembly 7 may be configured as an electric heating element.

[0072] Figure 2An internal combustion engine 8 having a combustion chamber 8b and a corresponding intake passage 8a is also schematically depicted. The outlet 5 of the preparation device 1 is selectively connected in fluid communication with the intake passage 8a via an outlet valve 5a for injecting fuel from the container 2 into the intake passage 8a for further combustion within the combustion chamber 8b.

[0073] It is worth noting that, Figure 2 The description depicts the situation where the shifting element 6 is about to begin or has just begun to retract in order to expand the container 2. Furthermore, the inlet valve 4 opens and the gaseous medium is introduced into the container 2. That is, Figure 2 The situation corresponds to Figure 1 The transformation of ab.

[0074] Figure 3 It also describes a situation where the shifting element 6 continues its movement to further expand container 2, while the fuel inlet valve 3 opens and liquid fuel is introduced into container 2. That is, Figure 3 The situation corresponds to Figure 1 The transformation of bc.

[0075] also, Figure 4 The description depicts a situation where the shifting element 6 has reached its end position, and the container volume has reached its maximum value. At least during this time, heat is introduced into the container 2 by the heating device 7 via the shifting element 6. That is, Figure 3 The situation corresponds to Figure 1 The transformation.

[0076] Figure 5 The text describes a situation where container 2 is contracting and the pressure inside container 2 is increasing. In other words, Figure 5 The situation corresponds to Figure 1 The transformation ef.

[0077] Figure 6 It also describes a situation where, as the fuel and gaseous medium are discharged from container 2, the shifting element 6 continues its movement to contract container 2, or just reaches its end corresponding to the minimum container volume. That is to say, Figure 6 The situation corresponds to Figure 1 The transformation of fa.

[0078] List of reference numerals

[0079] 1. Preparation apparatus

[0080] 2 containers

[0081] 3. Fuel Inlet Valve

[0082] 4. Inlet valve

[0083] 5. Exports

[0084] 5a Dedicated Outlet Valve

[0085] 6. Shifting elements

[0086] 6a Electromechanical Actuator

[0087] 7. Heater device

[0088] 8. Internal Combustion Engine

[0089] 8a Intake passage

[0090] 8b Combustion Chamber

[0091] ab Introducing liquid fuel

[0092] bc Introducing a gaseous medium

[0093] cd expansion container

[0094] de Apply heat

[0095] ef shrink container

[0096] fa Injection of gaseous or supercritical fuel

Claims

1. A method for preparing a liquid fuel for a combustion cycle in an internal combustion engine (8), the method comprising the following steps: - A predetermined amount of liquid fuel is introduced into a container (2) of the preparation apparatus (1) at a first pressure and a first temperature, which defines a first container volume, thereby establishing a first thermodynamic state of the fuel within the container (2); - Expand the container (2) to define a second container volume greater than the volume of the first container, so that the fuel enters a second thermodynamic state defined by a second pressure and a second temperature lower than the first pressure, the second thermodynamic state corresponding to the gas phase of the fuel; - Apply heat to the fuel; - The container (2) is contracted to define a third container volume smaller than that of the second container, so that the fuel enters a third thermodynamic state defined by a third pressure higher than the second pressure and a third temperature higher than the first temperature, the third thermodynamic state corresponding to the gaseous or supercritical phase of the fuel. - The fuel is injected from the container (2) to further introduce the fuel into the combustion chamber (8b) of the internal combustion engine (8).

2. The method according to claim 1, characterized in that, The volume of the third container is equal to or less than the volume of the first container.

3. The method according to claim 1 or 2, characterized in that, The third pressure is equal to or higher than the first pressure.

4. The method according to any one of claims 1 to 3, characterized in that, The method further includes the step of introducing a gaseous medium into the container (2) during or before expanding the container (2).

5. The method according to claim 4, characterized in that, The gaseous medium is air, nitrogen, exhaust gas recirculation (EGR), or any mixture of the aforementioned gases.

6. The method according to claim 4 or 5, characterized in that, The amount of gas medium introduced is insufficient to produce a combustible mixture.

7. The method according to any one of claims 1 to 6, characterized in that, Fuel is discharged from the container (2) by any one or both of the following: - Open the dedicated outlet valve (5a) attached to the outlet (5) of the container (2), and - Open the injector valve away from the rest of the preparation device (1).

8. The method according to any one of claims 1 to 7, characterized in that, The predetermined amount of liquid fuel corresponds to a portion or all of the fuel charge to be burned in the combustion chamber of the associated engine during a single combustion cycle.

9. The method according to any one of claims 1 to 8, characterized in that, Fuel from the preparation device (1) is introduced into the combustion chamber (8b) to be burned as a primary fuel, an ignition fuel, or a fuel for a specific engine mode, or any combination thereof, for example, for low load or low speed mode.

10. The method according to any one of claims 1 to 9, characterized in that, Fuel from the preparation device (1) is introduced into the combustion chamber (8b) for combustion as any of the following: - Premixed combustion charge, or a portion thereof, or - Part of the diffusion combustion charge.

11. The method according to any one of claims 1 to 10, characterized in that, The liquid fuel includes ammonia or alcohol, such as methanol.

12. An apparatus (1) for preparing liquid fuel for an internal combustion engine (8), the apparatus (1) comprising: - Container (2); - A fuel inlet valve (3), configured to selectively introduce liquid fuel into the container (2), and - Outlet (5), the outlet being configured to inject the fuel from the container (2) in a gaseous or supercritical phase. The preparation apparatus (1) is characterized in that it further includes: - A shifting element (6), connected to the container (2), such that the shifting element (6) defines a variable container volume within the container (2) or together with the container (2) defines a variable container volume, and - A heater device (7) for applying heat to the fuel in the container (2).

13. The preparation apparatus (1) according to claim 12, characterized in that, The preparation apparatus (1) further includes an inlet valve (4) for introducing a gaseous medium into the container, wherein the outlet (5) is also configured to inject a mixture of gaseous or supercritical phase fuel and the gaseous medium from the container (2).

14. The preparation apparatus (1) according to claim 12 or 13, characterized in that, The heater device (7) includes one or more of the following: - An electric heating element (7) is arranged to be connected to the shifting element (6); - An electric heating element arranged around the container (2), or - A heating fluid conduit for guiding heating fluid through which the heating fluid conduit is arranged around the container (2).

15. The preparation apparatus (1) according to any one of claims 12 to 14, characterized in that, The fuel intake valve (3) is also configured to meter a predetermined amount of liquid fuel, wherein the predetermined amount of liquid fuel corresponds to a portion or all of the fuel charge to be burned in the combustion chamber (8b) of the associated engine (8) during a single combustion cycle.

16. The preparation apparatus (1) according to any one of claims 12 to 15, characterized in that, The preparation apparatus further includes an outlet valve for selectively opening and closing fluid communication with the container (2) via the outlet (5).

17. The preparation apparatus (1) according to claim 16, characterized in that, The outlet valve is configured as one or both of the following: - A dedicated outlet valve (5a) attached to the outlet (4), or - The injector valve is located away from the rest of the preparation device (1).

18. The preparation apparatus (1) according to any one of claims 12 to 17, characterized in that, The preparation apparatus also includes an electromechanical actuator (6a) for driving the shifting element (6).

19. An internal combustion engine (8), characterized in that, The internal combustion engine includes a preparation device (1) according to any one of claims 12 to 18, wherein the preparation device is associated with the combustion chamber (8b) of the engine, and the preparation device (1) is arranged to inject fuel to further introduce the fuel into the combustion chamber (8b).

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