An injector assembly, a common rail fuel feed system, a reciprocating internal combustion engine and a method of operating thereof

Abstract

An injector assembly (1) for providing change-over of fuels direct-injected in an alternating manner through the same injector assembly (1) from a pressurized fuel rail (10a) into a reciprocating internal combustion engine (20). The injector assembly (1) comprises an injector (2), having one or more nozzle orifices (4a) through which fuel is injected, and an accumulator (6), having one or more feed orifices (7a) through which fuel is introduced into an accumulator chamber (9). A minimum throughput flow area of the injector is 1 - 18 times of a combined cross sectional flow area of the one or more feed orifices (7a). After switching between fuels in the fuel feed system (10) the injector assembly (1) provides a gradual change-over of fuels over a pre-determined number of injection cycles. A common rail fuel feed system, a reciprocating internal combustion engine and a method of operating such engine are also concerned.

Description

[0001] AN INJECTOR ASSEMBLY, A COMMON RAIL FUEL FEED SYSTEM, A RECIPROCATING INTERNAL COMBUSTION ENGINE AND A METHOD OF OPERATING THEREOF

[0002] FIELD OF THE DISCLOSURE

[0003] The present disclosure relates to reciprocating internal combustion engines, and more particularly to an injector assembly for providing change-over of fuels direct- injected in an alternating manner through the same injector assembly from a pressurized fuel rail of a fuel feed system into a reciprocating internal combustion engine. The present disclosure further concerns a fuel feed system, a reciprocating internal combustion engine, and a method of operating the reciprocating internal combustion engine.

[0004] BACKGROUND OF THE DISCLOSURE

[0005] Reducing emissions from reciprocating internal combustion engines has prompted the need for running such an engine on different fuels so that the change-over from one fuel to another can be carried out during operation of the engine. A typical approach for achieving this has been to fit respective injectors and possibly other fuel feed system components for each of the intended fuels. While this approach can be adapted when designing new engines, retrofitting such arrangements might not be feasible on existing engines due to space constrains e.g., on the cylinder head or in the vicinity of the engine itself. On the other hand, a change-over between different fuels through a single injector has been considered challenging due to the sudden change in properties of the fuel injected.

[0006] BRIEF DESCRIPTION OF THE DISCLOSURE

[0007] An object of the present disclosure is to provide a solution for alleviating the challenges discussed above.

[0008] The object of the disclosure is achieved by an injector assembly, a fuel feed system, a reciprocating internal combustion engine and a method for operating the engine, which are characterized by what is stated in the independent claims. The preferred embodiments of the disclosure are disclosed in the dependent claims.

[0009] The disclosure is based on the idea of providing an accumulator associated to and arranged upstream of an injector, wherein the accumulator has an accumulator chamber in which a first fuel is mixed with a second fuel during a changeover of the fuels, so as to achieve a gradual change of the fuel injected. Moreover, feed orifices of the accumulator are dimensioned with respect to injector orifices in a way to result in a high-shear mixing of fuel introduced into the accumulator chamber and fuel already present in the accumulator chamber.

[0010] An advantage of the disclosure is that multiple fuels can be used on a single fuel feed system, while still allowing gradual change-over between fuels. Moreover, this allows the use of a single injector, which in turn, allows the provision of a multi-fuel feed system even on pre-existing engines without redesigning the cylinder head.

[0011] According to a first aspect of the present disclosure, an injector assembly is provided. Notably, the injector assembly is intended for providing change-over of fuels direct-injected in an alternating manner through the same injector assembly from a pressurized fuel rail of a fuel feed system into a reciprocating internal combustion engine. In the context of this disclosure, the term direct-injected refers to injection of fuel directly into a combustion chamber, or a prechamber, of a reciprocating internal combustion engine, as opposed to port injection or manifold injection.

[0012] The injector assembly comprises an injector, which in turn, comprises an injector inlet, an injector nozzle, and an injector valve. The injector valve is configured to sequentially open and close fluid communication between the injector inlet and the injector nozzle, so as to allow, and respectively interrupt, fuel flow through the injector nozzle. The injector nozzle comprises one or more nozzle orifices through which fuel is injected.

[0013] The injector assembly further comprises an accumulator, which in turn, comprises an accumulator feed passage, an accumulator outlet, and an accumulator chamber.

[0014] The accumulator feed passage is couplable in fluid communication with a pressurized fuel rail of a fuel feed system, and the accumulator outlet is arranged in fluid communication with the injector inlet. Moreover, the accumulator chamber is arranged in fluid communication with the accumulator feed passage and the accumulator outlet, thereby defining a flow route therebetween.

[0015] Moreover, the accumulator feed passage comprises one or more feed orifices, through which feed orifices fuel is introduced into the accumulator chamber. Most suitably, the one or more feed orifices open into the accumulator chamber. For example, the one or more feed orifices may open directly into the accumulator chamber (i.e., the feed orifices separate the feed passage from the accumulator chamber. Alternatively, the one or more feed orifices may be arranged within the feed passage, at a distance from the accumulator chamber. In the former configuration, the one or more feed orifices are advantageously arranged such that the fuel flow from the orifice reaches the accumulator chamber as a jet. Notably, a combined cross-sectional flow area of the one or more feed orifices is 1 - 18 times of a minimum throughput flow area of the injector. In the context of this disclosure, the minimum throughput flow area of the injector is defined as the cross-sectional flow area of a portion along a flow route through the injector with a most prominent throttling effect. For example, the minimum throughput flow area could be defined, e.g., as the cross- sectional flow area of a neck portion upstream of a nozzle (sac), or as the combined cross- sectional flow area(s) of one or more nozzle orifices of the injector. Such relative dimensioning has been considered suitable for achieving a sufficient velocity of the fuel flow through the one or more feed orifices to induce high-shear mixing between the different fuels. At the same time, sufficient flow through the feed orifices is achieved to prevent excessive pressure drop within the accumulator volume and at the injector nozzle (sac). Particularly, the relative dimensioning discussed above has been considered suitable for preventing cumulative pressure drop over successive injections (i.e., a situation in which a desired injection pressure is not recovered before between successive injections). This is particularly relevant for arrangements where fuels of different energy content are used, as a fuel with a smaller specific energy content requires a larger volumetric flow and is more prone to such excessive pressure drop. Moreover, a gradual change-over of fuels over a pre-determined number of injection cycles is achieved after switching between fuels in the fuel feed system.

[0016] In an embodiment according to the first aspect of the disclosure, the combined cross- sectional flow area of the one or more feed orifices is 4 - 12 times of a minimum throughput flow area of the injector. Such relative dimensioning has been considered to further optimize the balance between achieving high-shear mixing while preventing excessive pressure drop (and particularly cumulative pressure drop).

[0017] In an embodiment according to the first aspect of the disclosure, the one or more feed orifices are arranged as one or more throttle openings extending through an internal wall surface of the accumulator chamber.

[0018] Preferably, but not necessarily, the one or more feed orifices and the accumulator outlet are positioned on opposite sides of the accumulator chamber. Such an arrangement is considered to be particularly advantageous for producing a gradient mixture of the different fuels, thereby resulting in a gradual change-over between said fuels.

[0019] In an embodiment according to the first aspect of the disclosure, the accumulator feed passage extends into the accumulator chamber as a protrusion. Preferably, but not necessarily, the accumulator chamber annularly surrounds the protrusion of the feed passage. For example, the protrusion may be arranged centrally within the accumulator chamber.

[0020] Preferably, but not necessarily, multiple feed orifices may be provided along a length of the protrusion of the accumulator feed passage. Alternatively, or in addition, multiple feed orifices may be provided at different circumferential positions about the protrusion of the feed passage.

[0021] Where multiple feed orifices are provided along the length of the protrusion, distinct flow paths of various lengths are defined between an inlet end of the feed passage (i.e., junction of the feed passage and the pressurized fuel rail) and respective feed orifices. Advantageously, in such an arrangement, a feed orifice having a longer flow path has a larger cross-sectional flow area than a feed orifice having a shorter flow path. That is, the longer the fuel flows along the feed passage, the larger is the cross-sectional flow area of the feed passage through which it is introduced into the accumulator chamber. This serves to compensate for pressure drop along the feed passage, thereby balancing flow between different feed orifices.

[0022] Preferably, but not necessarily, the feed passage extends into the protrusion as an internal duct opening into and extending within the protrusion, so as to define an intermediate volume between an outer wall surface of the internal duct and an internal wall surface of the protrusion. That is, the protrusion and the feed passage are provided as a doublewalled structure, in which the feed passage is internal to the protrusion. In such an arrangement, fuel flow from the internal duct is introduced firstly into the intermediate volume, from where it continues to flow into the accumulator chamber.

[0023] Suitably, such an internal duct may taper towards a distal end thereof. That is, the cross- sectional flow area may decrease towards the distal end of the of the internal duct.

[0024] Moreover, feedback orifices may extend between the internal duct and the accumulator chamber, thereby establishing direct fluid communication therebetween. The internal duct and the feedback orifices are configured to induce a feedback flow from the accumulator chamber into the internal duct, when a motive flow (fuel flow from the pressurized fuel rails passage) runs through the internal duct to the intermediated volume. That is, the feedback orifices and the internal duct are configure as an ejector drawing fuel from the accumulator chamber into the internal duct, entrained by the fuel flow form the pressurized fuel rail into the intermediate volume (and further into accumulator chamber). Consequently, in addition to the fuel flow from the feed passage to the accumulator chamber along the internal duct and the intermediate volume, a simultaneous feedback flow from the accumulator chamber back to the internal duct is also achieved. This results in a further improved mixing between fuels during a change-over, thus contributing in a more gradual change of the fuel introduced to the injector.

[0025] Advantageously, multiple feedback orifices may be provided along a length of the internal duct. Alternatively, or in addition, multiple feedback orifices may be provided at different circumferential positions about the protrusion of the feed passage.

[0026] Where multiple feedback orifices are provided along a length of the internal duct, distinct flow paths of various lengths are defined between an inlet end of the feed passage and respective feedback orifices. Advantageously, in such an arrangement, a feedback orifice having a longer flow path has a smaller cross-sectional flow area than a feedback orifice having a shorter flow path.

[0027] That is, the further away from the inlet end of the feed passage a feedback orifice is located (along the flow route to said feedback passage), the smaller the cross-sectional flow area of the feedback orifice is, as compared to other feedback orifices. This serves to compensate for pressure drop along the feed passage, thereby balancing flow between different feedback orifices.

[0028] In an embodiment according to the first aspect of the disclosure, the accumulator and the injector are provided as an integrated unit. That is, the accumulator may be directly coupled to the injector, or the accumulator may be formed as a single unit together with the injector.

[0029] In an embodiment according to the first aspect of the disclosure, the accumulator and the injector may be provided as separate units coupled in fluid communication with each other.

[0030] It should be noted that the first aspect of the present disclosure encompasses any combination of two or more embodiments, or variants thereof, as discussed above.

[0031] According to a second aspect of the present disclosure, a common rail fuel feed system for direct-injecting multiple fuels into a reciprocating internal combustion engine is provided. Notably, the common rail fuel feed system comprises multiple injector assemblies according to the first aspect of the disclosure, each of the injector assemblies corresponding to a respective distinct combustion chamber.

[0032] The fuel feed system further comprises a common pressurized fuel rail, a first fuel delivery arrangement and a second fuel delivery arrangement. The pressurized fuel rail is coupled to the multiple injector assemblies, so as to feed fuel to the accumulator feed passages thereof. Moreover, the first fuel delivery arrangement is configured to provide a first pressurized fuel to the pressurized fuel rail, whereas the second fuel delivery arrangement is configured to provide a second pressurized fuel to the pressurized fuel rail.

[0033] The fuel feed system further comprises a controller operationally coupled to the first fuel delivery arrangement and the second fuel delivery arrangement so as to control the provision of either or both of the first pressurized fuel and the second pressurized fuel into the pressurized fuel rail. It should be noted that such a controller could be provided as a control unit of the associated reciprocating internal combustion engine.

[0034] For example, the provision of the of the first pressurized fuel and the second pressurized fuel may be carried out by activating and deactivating separate pumps and valves corresponding to the first pressurized fuel and the second pressurized fuel, respectively. Alternatively, or in addition, both the first pressurized fuel and the second pressurized fuel may be provided into the pressurized fuel rail via same pump(s) or even same pressure lines(s).

[0035] Preferably, but not necessarily, an accumulator chamber of an injector assembly has an accumulator volume corresponding to 15-60 times a maximum fuel amount deliverable into a combustion chamber corresponding to the injection assembly during a single combustion cycle. Such dimensioning of the accumulator volume has been considered advantageous for mitigating propagation a pressure shock wave from the injector to a pressurized fuel rail of a fuel feed system. This is particularly relevant for arrangements where fuels of different energy content are used, as a fuel with a smaller specific energy content requires a larger volumetric flow, and consequently, a larger flow area of the feed orifices(s). However, such larger feed orifices may no longer provide sufficient pressure shock wave dampening, which can be compensated for with the dimensioning of the accumulator volume, as discussed above.

[0036] It should be noted that the second aspect of the present disclosure encompasses any combination of two or more embodiments, or variants thereof, as discussed above.

[0037] According to a third aspect of the present disclosure, a reciprocating internal combustion engine is provided. The engine comprises multiple combustion chambers, and the common rail fuel feed system according to second aspect of the disclosure. Notably, each of the injector assemblies are coupled to a respective combustion chamber so as to inject therein fuel from the pressurized fuel rail. It should be noted that the third aspect of the present disclosure encompasses any combination of two or more embodiments, or variants thereof, as discussed above.

[0038] According to a fourth aspect of the present disclosure, a method of operating the internal combustion engine according to the second aspect of the disclosure is provided.

[0039] The method comprises, during running of the engine, a transition step, in turn, comprising the steps of interrupting provision of the first pressurized fuel to the pressurized fuel rail, and initiating provision of the second pressurized fuel to the pressurized fuel rail.

[0040] Following provision of the second pressurized fuel to the pressurized fuel rail the transition step further comprises monitoring combustion characteristics of one or more combustion chambers, and determining a deviation of monitored combustion characteristics from nominal combustion characteristics. For example, combustion characteristics may include or more of the following: RPM, cylinder pressure and exhaust temperature.

[0041] Moreover, in response to the determined deviation, injection parameters are adjusted. For example, injection parameters may include one or more of the following: injection duration, injection timing and injection pressure. Notably, if combustion characteristics are monitor per cylinder, then injections parameters can also be adjusted per cylinder.

[0042] Preferably, but not necessarily, the first pressurized fuel is LFO fuel or diesel fuel, and the second pressurized fuel is an alcohol -based fuel or an ammonia -based fuel.

[0043] Preferably, but not necessarily, the first pressurized fuel and the second pressurized fuel are immiscible with each other.

[0044] Preferably, but not necessarily, the first pressurized fuel and second pressurized fuel have different viscosities.

[0045] Preferably but not necessarily, the first pressurized fuel and the second pressurized fuel have different specific energy contents.

[0046] It should be noted that the fourth aspect of the present disclosure encompasses any combination of two or more embodiments, or variants thereof, as discussed above.

[0047] BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In the following the disclosure will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings, in which

[0049] Fig. 1 schematically illustrates an injector assembly according to an embodiment of the present disclosure, provided in connection with a reciprocating internal combustion engine; Fig. 2 schematically illustrates an injector assembly according to an alternative embodiment of the present disclosure, provided in connection with a reciprocating internal combustion engine, and

[0050] Fig. 3 schematically illustrates an injector assembly according to a further embodiment of the present disclosure, provided in connection with a reciprocating internal combustion engine.

[0051] DETAILED DESCRIPTION OF THE DISCLOSURE

[0052] Fig. 1 schematically depicts an injector assembly 1 for injecting fuel from a fuel feed system 10 into a reciprocating internal combustion engine 20. More particularly, the injector assembly 1 allows change-over of fuels direct-injected in an alternating manner through the same injector assembly 1 from a pressurized fuel rail 10a into a reciprocating internal combustion engine 20. Notably, the injector assembly 1 comprises an injector 2 and an accumulator 6.

[0053] A feed passage 7 of the accumulator 6 is coupled to a pressurized fuel rail 10a of the fuel feed system 10, such that fuel from the pressurized fuel rail 10a can be introduced into an accumulator chamber 9 via the feed passage 7. Moreover, an accumulator outlet 8 of the accumulator 6 is coupled to an injector inlet 3 of the injector 2, such that fuel from the accumulator chamber can be introduced to the injector 2.

[0054] The injector 2 comprises an injector valve 5 and a nozzle 4 having nozzle orifices, through which fuel can be injected into the combustion chamber 21 or a prechamber of the combustion engine 20. The injector valve 5 is configured to sequentially open and close fluid communication between the injector inlet 3 and the injector nozzle 4, so as to allow, and respectively interrupt, fuel flow through the injector nozzle 4.

[0055] The fuel feed system 10 comprises a first fuel delivery arrangement 11 for providing a first pressurized fuel into the pressurized fuel rail 10a, and a second fuel delivery arrangement 12 for providing a second pressurized fuel in the pressurized fuel rail 10a.

[0056] Notably, the first fuel delivery arrangement 11 and the second fuel delivery arrangement 12 are controlled by a controller 13. That is, the provision of either of both of the first pressurized fuel and the second pressurized fuel into the pressurized fuel rail 10a is controlled by the controller 13. The controller may be provided as a part of the internal combustion engine 20, or the fuel feed system 10.

[0057] For example, the first fuel delivery arrangement 11 may comprise a dedicated first pump and a first pressure line coupling said first pump to the pressurized fuel rail 10a, whereas the second fuel delivery arrangement 12 may comprise a dedicated second pump and a second pressure line coupling said second pump to the pressurized fuel rail 10a. In another exemplary alternative, a mutual pump and a mutual pressurized fuel line may be provided for providing both the first pressurized fuel and the second pressurized fuel to the pressurized fuel rail 10a. This could be achieved, for example, by coupling the mutual pump to a first fuel supply and a second fuel supply via separate respective pump feed valves.

[0058] When a change-over from e.g., the first fuel to the second fuel is initiated, the control unit 13 controls the first fuel delivery arrangement 11 to interrupt supply of the first pressurized fuel to the pressurized fuel rail 10a, and controls the second fuel delivery arrangement 11 to initiate supply of the second pressurized fuel to the pressurized fuel rail 10a.

[0059] The second pressurized fuel then flows from the pressurized fuel rail 10a to feed passage 7, and further through on or more feed orifice 7a to the accumulator chamber 9, as drawn by the opening and closing of the injector valve 5. Notably, in the embodiment of Fig. 1 the feed orifice 7a is provided as a single orifice in the feed passage 7 extending through the wall of the accumulator chamber 9. The feed orifice 7a opens directly to the accumulator chamber 7a. In Fig. 1 , the feed orifices 7a and the accumulator outlet 8 are depicted on opposite sides of the accumulator chamber 9. While this is believed to be advantageous for the gradual change over of fuels, other configurations may be envisaged.

[0060] As the minimum throughput flow area of the injector 4 is 4 - 12 times of a combined cross- sectional flow area of the one or more feed orifices 7a, the second pressurized fuel is introduced through the feed orifices 7a into the accumulator chamber 9 at a relatively high velocity, inducing high-shear mixing of the second pressurized fuel with the first pressurized fuel already present in the accumulator chamber 9.

[0061] Consequently, a mixture of the first and second pressurized fuels is achieved within the accumulator chamber 9, the composition of which gradually changes over from the first fuel to the second.

[0062] Fig. 2 illustrates an injector assembly 1 according to another embodiment of the disclosure, the configuration being otherwise similar to that of Fig. 1. Notably, the feed passage 7 extends into the accumulator chamber 9 as a protrusion 7b. In the embodiment illustrated in Fig. 2, the protrusion 7b is provided centrally such that the volume of the accumulator chamber 9 surrounds the protrusion 7b, albeit other configurations can be envisaged.

[0063] Moreover, Fig. 2 illustrates multiple feed orifices 7a provided both along the length of the protrusion 7b, and on different circumferential positions about the protrusion 7b. The arrangement depicted in Fig.2 is also considered advantageous for achieving proper mixing of between different fuels and a gradual transformation of mixture composition during a change-over from a first pressurized fuel to a second pressurized fuel.

[0064] Fig. 3 illustrates an injector assembly 1 according to a further embodiment of the disclosure, the configuration being otherwise similar to that of Fig. 1 and Fig. 2.

[0065] Also in Fig. 3, the protrusion 7b is provided centrally such that the volume of the accumulator chamber 9 surrounds the protrusion 7b, albeit other configurations can be envisaged. However, the feed passage 7 extends into the protrusion 7b as an internal duct 7c, such that an intermediate volume is defined between an internal wall surface of the protrusion 7b. and an outside wall surface of the internal duct 7c. That is, a double-walled structure may be provided, where the protrusion 7b forms an outer wall and the internal duct 7c forms an internal wall.

[0066] In the embodiment of Fig. 3, fuel from the pressurized fuel rail 10a is introduced along the internal duct 7c into the intermediate volume, from where the fuel flows further into the accumulator chamber via feed passages 7a. Also in Fig. 3, feed passages 7a are positioned along the length of the protrusion 7b, and at various circumferential positions about the protrusion 7b.

[0067] Notably, multiple feedback orifices 7d are provided between the internal duct 7d and the accumulator chamber 9. Such feedback orifices 7d may be positioned along the length of the internal duct 7d and at different circumferential positions about said internal duct 7d. The feedback orifices are dimensioned to draw fuel form the accumulator chamber 9 into the internal duct, entrained by fuel flow from the feed passage 7. That is, the internal duct is configured to act as an ejector for drawing fuel from the accumulator chamber 9, while the fuel from the feed passage acts as a motive fluid.

[0068] The arrangement depicted in Fig.3 is further considered advantageous for achieving proper mixing of different fuels and a gradual transformation of mixture composition during a change-over from a first pressurized fuel to a second pressurized fuel.

[0069] LIST OF REFERENCE NUMERALS

[0070] 1 injector assembly

[0071] 2 injector

[0072] 3 injector inlet

[0073] 4 injector nozzle 4a nozzle orifice(s)

[0074] 5 injector valve

[0075] 6 accumulator

[0076] 7 accumulator feed passage 7a feed orifice(s)

[0077] 7b protrusion

[0078] 7c internal duct

[0079] 7d ejector orifice

[0080] 8 accumulator outlet 9 accumulator chamber

[0081] 9a internal wall surface

[0082] 10 feed system

[0083] 10a pressurized fuel rail

[0084] 11 first fuel delivery arrangement 12 second fuel delivery arrangement

[0085] 13 controller

[0086] 20 reciprocating internal combustion engine

[0087] 21 combustion chamber

Claims

CLAIMS1. An injector assembly (1 ) for providing change-over of fuels direct-injected in an alternating manner through the same injector assembly (1 ) from a pressurized fuel rail (10a) of a fuel feed system (10) into a reciprocating internal combustion engine (20), the injector assembly (1 ) comprising: an injector (2), in turn, comprising: - an injector inlet (3); - an injector nozzle (4), and an injector valve (5) configured to sequentially open and close fluid communication between the injector inlet (3) and the injector nozzle (4), so as to allow, and respectively interrupt, fuel flow through the injector nozzle (4), and an accumulator (6), comprising: an accumulator feed passage (7) couplable in fluid communication with a pressurized fuel rail (10a) of a fuel feed system (10), - an accumulator outlet (8) arranged in fluid communication with the injector inlet (3), and- an accumulator chamber (9) in fluid communication with the accumulator feed passage (7) and the accumulator outlet (8), thereby defining a flow route therebetween, wherein the nozzle (4) comprises one or more nozzle orifices (4a) through which fuel is injected, characterized in that the accumulator feed passage (7) comprises one or more feed orifices (7a), which opens into the accumulator chamber (9) and through which feed orifices (7a) fuel is introduced into the accumulator chamber (9), wherein a combined cross sectional flow area of the one or more feed orifices (7a) is 1 - 18 times of a minimum throughput flow area of the injector, wherein after switching between fuels in the fuel feed system (10) the injector assembly (1 ) provides a gradual change-over of fuels over a pre-determined number of injection cycles.

2. The injector assembly (1) according to claim 1 , characterized in that the combined cross sectional flow area of the one or more feed orifices (7a) is 4 - 12 times of the minimum throughput flow area of the injector3. The injector assembly (1) according to claim 1 or 2, characterized in that the one or more feed orifices (7a) are arranged as one or more throttle openings extending through an internal wall surface (9a) of the accumulator chamber (9a).

4. The injector assembly (1) according to claim 3, characterized in that the one or more feed orifices (7a) and the accumulator outlet (8) are positioned on opposite sides of the accumulator chamber (9).

5. The injector assembly (1 ) according to claim 1 or 2, characterized in that the accumulator feed passage (7) extends into the accumulator chamber (9) as a protrusion (7b).

6. The injector assembly (1 ) according to claim 5, characterized in that the accumulator chamber (9) annularly surrounds the protrusion (7b) of the feed passage (7).

7. The injector assembly (1) according to claim 5 or 6, characterized in that either or both of: multiple feed orifices (7a) are provided along a length of the protrusion (7b) of the accumulator feed passage (7), and multiple feed orifices (7a) are provided at different circumferential positions about the protrusion (7b) of the feed passage (7).

8. The injector assembly (1 ) according to claim 7, characterized in that multiple feed orifices (7a) are provided along the length of the protrusion (7b) thereby defining distinct flow paths of various lengths between an inlet end of the feed passage (7) and respective feed orifices (7a), and wherein a feed orifice (7a) having a longer flow path has a larger cross-sectional flow area than a feed orifice (7a) having a shorter flow path.

9. The injector assembly (1 ) according to any of the preceding claims 5-8, characterized in that the feed passage extends into the protrusion (7b) as an internal duct (7c) opening into and extending within the protrusion (7b), so as to define an intermediate volume between an outer wall surface of the internal duct (7c) and an internal wall surface of the protrusion (7b), wherein feedback orifices (7d) extend between the internal duct (7c) and the accumulator chamber (9) thereby establishing direct fluid communication therebetween, andwherein the internal duct (7c) and the feedback orifices (7d) are configured to induce a feedback flow from the accumulator chamber (9) into the internal duct (7c), when a motive flow runs through the internal duct (7c) to the intermediated volume.

10. The injector assembly (1 ) according to claim 9, characterized in that either or both of: multiple feedback orifices (7d) are provided along a length of the internal duct (7c), and multiple feedback orifices (7d) are provided at different circumferential positions about the protrusion (7b) of the feed passage (7).11 . The injector assembly according to claim 10, characterized in that multiple feedback orifices (7d) are provided along a length of the internal duct (7c), thereby defining distinct flow paths of various lengths between an inlet end of the feed passage (7) and a respective feedback orifice (7a), and wherein a feedback orifice (7d) having a longer flow path has a smaller cross-sectional flow area than a feedback orifice (7d) having a shorter flow path.

12. The injector assembly according to any of the preceding claims 9-11 , characterized in that the internal duct (7c) tapers towards a distal end thereof.

13. The injector assembly (1 ) according to any of the preceding claims 1 -12, characterized in that the accumulator (6) and the injector (2) are provided as an integrated unit.

14. The injector assembly according to any of the preceding claims 1 -12, characterized in that the accumulator (6) and the injector (2) are provided as separate units coupled in fluid communication with each other.

15. A common rail fuel feed system (10) for direct-injecting multiple fuels into a reciprocating internal combustion engine (20), characterized by the common rail fuel feed system (10) comprising: multiple injector assemblies (1) according to any of the preceding claims 1 -14, each of the injector assemblies (1 ) corresponding to a respective distinct combustion chamber (21); a common pressurized fuel rail (10a) coupled to the multiple injector assemblies (1 ), so as to feed fuel to the accumulator feed passages (7) thereof;a first fuel delivery arrangement (11 ) configured to provide a first pressurized fuel to the pressurized fuel rail (10a); a second fuel delivery arrangement (12) configured to provide a second pressurized fuel to the pressurized fuel rail (10a), and a controller (13) operationally coupled to the first fuel delivery arrangement (11) and the second fuel delivery arrangement (12) so as to control the provision of either or both of the first pressurized fuel and the second pressurized fuel into the pressurized fuel rail (10a).

16. The common rail fuel feed system (10) according to claim 15, characterized in that an accumulator chamber (9) of an injector assembly has an accumulator volume corresponding to 15-60 times a maximum fuel amount deliverable into a combustion chamber (21) corresponding to the injection assembly (1 ) during a single combustion cycle.

17. A reciprocating internal combustion engine (20) having multiple combustion chambers (21 ), characterized by comprising the common rail fuel feed system (10) according to claim 15 or 16, wherein each of the injector assemblies (1 ) are coupled to a respective combustion chamber (21) so as to inject therein fuel from the pressurized fuel rail (10a).

18. A method of operating the internal combustion engine (20) of claim 17, characterized in that the method comprises, during running of the engine (20), a transition step, in turn, comprising the steps of: - interrupting provision of the first pressurized fuel to the pressurized fuel rail (10a), and- initiating provision of the second pressurized fuel to the pressurized fuel rail (10a), wherein the transition step further comprises, following provision of the second pressurized fuel to the pressurized fuel rail (10a):- monitoring combustion characteristics of one or more combustion chambers (21 ), determining a deviation of monitored combustion characteristics from nominal combustion characteristics, and - adjusting injection parameters in response to the determined deviation.

19. The method according to claim 18, characterised in by one or more of the following:the first pressurized fuel is LFO fuel or diesel fuel, and the second pressurized fuel is an alcohol -based fuel or an ammonia -based fuel; the first pressurized fuel and the second pressurized fuel are immiscible with each other; the first pressurized fuel and second pressurized fuel have different viscosities, and the first pressurized fuel and the second pressurized fuel have different specific energy contents.

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