Fuel injector for gaseous fuel

Abstract

A fuel injector (1) for gaseous fuel has: an injection nozzle (3); a support body (4) having a tubular shape and provided therein with a supply channel (5) terminating in the spray nozzle (3); an injection valve (7); a tubular sleeve (12) arranged around the end of the support body (4), the flashboard (9) being completely contained in the tubular sleeve (12), the tubular sleeve (12) terminating in the injection nozzle (3); and an actuator (6) configured to move the shutter (9). The injection duct (14) formed when the injection valve (7) is in the open position has a convergent initial section in which the area of the injection duct (14) gradually decreases from a first maximum value at the beginning of the injection duct (14) to a minimum value, and a divergent end section in which the area of the injection duct (14) gradually decreases from a second maximum value at the beginning of the injection duct (14) to a minimum value. The area of the injection duct (14) increases from a minimum value until a second maximum value is reached.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims the priority of Italian patent application No. 102023000019236, filed on September 19, 2023, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The present invention relates to fuel injectors for gaseous fuels.

[0004] The present invention is advantageously applicable to electromagnetic hydrogen injectors, to which the following discussion will make explicit reference without loss of generality. Background Art

[0005] The electromagnetic fuel injector comprises a cylindrical tubular support provided with a central supply channel, which serves as a fuel conduit and ends in an injection nozzle regulated by an injection valve controlled by an electromagnetic actuator. The injection valve is provided with a needle which is moved between a closed position and an open position of the injection nozzle by the action of the electromagnetic actuator against the action of a closing spring which pushes the needle towards the closed position. The end of the needle has a shutter which is adapted to rest sealingly on a valve seat of the injection valve.

[0006] The most suitable configuration of a fuel injector for injecting hydrogen allows the gate to open outwardly so that the closed position of the gate is not negatively affected by the pressure generated in the combustion chamber; that is, when the gate opens outwardly, the pressure generated in the combustion chamber pushes the gate toward the closed position, thereby always ensuring that the fuel injector will not have an unwanted opening caused by pressure peaks in the combustion chamber.

[0007] However, a fuel injector having an open head opening outwards can only generate a fuel spray coaxial with the longitudinal axis of the injector, and this morphology of the fuel spray does not allow an optimization of the mixing between air and fuel and therefore of the combustion.

[0008] Patent application US2001025892A1 describes a supersonic fuel injector for gaseous fuels, wherein a nozzle for delivering the fuel is shaped with converging and diverging sections to accelerate the fuel flow to supersonic speeds.

[0009] Utility model DE 202023100690 U1 describes a fuel injector for gaseous fuels, in particular for hydrogen, wherein a gate is separated from a valve seat to form an injection duct through which the gaseous fuel flows and which has a converging initial section and a diverging terminal section. Summary of the invention

[0010] The object of the present invention is to provide a fuel injector for gaseous fuels which does not have the above-mentioned disadvantages (ie allows the production of a fuel spray which allows the mixing between air and fuel to be optimized) and which, in particular, is easy and inexpensive to produce.

[0011] According to the invention, a fuel injector for gaseous fuel is manufactured as stated in the appended claims.

[0012] The claims describe preferred embodiments of the invention and are an integral part of the present description. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The invention will now be described with reference to the accompanying drawings which illustrate non-limiting example embodiments of the invention, in which:

[0014] Figure 1 is a partially cut-away side view of a fuel injector;

[0015] Figure 2 yes Figure 1 A longitudinal sectional view of a distal end portion of a fuel injector;

[0016] Figure 3-6 yes Figure 1 three longitudinal cross-sectional views of the distal end of each variant of a fuel injector; and

[0017] Figure 7 Schematic showing the use of Figure 1 Fuel injectors for internal combustion engines.

[0018] List of reference numerals in the accompanying drawings

[0019] 1 Fuel Injector

[0020] 2 Longitudinal axis

[0021] 3 Injection nozzle

[0022] 4 Support

[0023] 5 Supply channel

[0024] 6 Electromagnetic actuator

[0025] 7 Injection valve

[0026] 8-pin

[0027] 9 Gate

[0028] 10 Valve seat

[0029] 11 Closing spring

[0030] 12 Sleeve

[0031] 13 End area

[0032] 14 Injection pipe

[0033] 15 Lateral pipe

[0034] 16 Outer edge

[0035] 17 Opening

[0036] E Internal combustion engine DETAILED DESCRIPTION

[0037] exist Figure 1 In the drawings, reference numeral 1 denotes as a whole a gaseous fuel (in particular hydrogen) injector having cylindrical symmetry about a longitudinal axis 2 and adapted to be controlled to inject hydrogen through an injection nozzle 3 which leads directly to an internal combustion engine E (at Figure 7 That is, the internal combustion engine E is supplied with hydrogen and is provided with an injection system, which directly injects hydrogen into a plurality of cylinders by using corresponding hydrogen injectors 1; therefore, the internal combustion engine E includes at least one cylinder and an injection system, which directly injects hydrogen into the cylinder by using a fuel (fuel) injector 1.

[0038] according to Figure 1 As shown, the fuel injector 1 comprises a support body 4 having a cylindrical tubular shape with a variable cross section along the longitudinal axis 2 and having a supply channel 5 extending along the entire length of the support body 4 to supply the injection nozzle 3 with pressurized hydrogen.

[0039] The support body 4 accommodates the electromagnetic actuator 6 in its upper part and the injection valve 7 in its lower part (in Figure 2 When in use, the injection valve 7 is actuated by the electromagnetic actuator 6 to adjust the hydrogen flow through the injection nozzle 3, and the hydrogen flow is obtained at the injection valve 7. According to a different embodiment not shown, the actuator 6 is piezoelectric instead of electromagnetic.

[0040] The electromagnetic actuator 6 is configured to move the movable unit axially (ie along the longitudinal axis 2), the movable unit being provided with a needle 8 (at Figure 2 The gate plate 9 and the valve seat 10 of the injection valve 7 (shown in Figure 2) cooperates to regulate the flow of hydrogen through the injection nozzle 3. In other words, the support body 4 terminates in a through opening, in which a valve seat 10 is defined and which is engaged by a gate 9. In particular, the electromagnetic actuator 6 is configured to move the gate 9 between a closed position and an open position of the injection valve 7. In addition, the electromagnetic actuator 6 is provided with a closing spring 11, which normally keeps the fuel injector 1 closed, i.e. the closing spring 11 pushes the gate 9 to the closed position of the injection valve 7. In other words, the injection valve 7 is normally closed under the action of the closing spring 11, which pushes the needle 8 into the closed position, in which the gate 9 of the needle 8 is pressed against the valve seat 10 of the injection valve 7.

[0041] according to Figure 2 As shown in the figure, the gate 9 is arranged outside the support body 4 and is pushed against the support body 4 by the closing spring 11 of the electromagnetic actuator 6; accordingly, in order to turn the injection valve 7 from the closed position to the open position of the injection valve 7, the gate 9 moves along the longitudinal axis 2 to the outside of the support body 4, that is, in a direction consistent with the supply direction of hydrogen. In the open position of the injection valve 7 (in Figure 2 ), the gate 9 is separated from the valve seat 10 to form a channel opening with a crown-shaped cross section; accordingly, the hydrogen injected through the injection nozzle 3 is in a hollow cone shape at the outlet. In other words, the electromagnetic actuator 6 is configured to be in the closed position of the injection valve 7 and the open position of the injection valve 7 (in Figure 2 In the closed position of the injection valve 7, the gate plate 9 is pressed against the valve seat 10. In the open position of the injection valve 7, the gate plate 9 is separated from the valve seat 10 to form an annular opening for hydrogen flow.

[0042] according to Figure 2 As shown, around the end of the support body 4 (i.e. at the injection valve 7 and the injection nozzle 3), a tubular sleeve 12 is arranged, which completely accommodates the gate 9 inside it and ends at the injection nozzle 3; that is, the injection nozzle 3 is delimited by the sleeve 12, which constitutes the end element of the fuel (fuel) injector 1.

[0043] exist Figure 2-5 In the embodiment shown, the gate 9 has a bulb-like shape and has an outer surface, which includes a first portion facing the valve seat 10 and is shaped to be sealingly coupled to the inner surface of the valve seat 10 when the injection valve 7 is in the closed position, and a second portion facing the inner surface of the sleeve 12 and always maintaining a given distance from the inner surface of the sleeve 12. Generally, between the outer surface of the gate 9 and the inner surfaces of the valve seat 10 and the inner surfaces of the sleeve 12, an annular injection duct 14 is defined, the initial portion of which is formed when the injection valve 7 is in the open position, and when the injection valve 7 is in the open position (in Figure 2), the fuel flows along the injection conduit 14 to the end region 13 of the injection conduit 14 (ie to the injection nozzle 3). More generally, the injection conduit 14 is externally bounded (defined) by the inner surface of the valve seat 10 and subsequently by the inner surface of the sleeve 14.

[0044] When the injection valve 7 is in the open position ( Figure 2 The injection conduit 14 formed by the valve seat 10 (shown in the figure) (initially between the gate 9 and the valve seat 10 and the sleeve 12) has a converging initial section (everywhere) and a diverging terminal section (at least initially), in which the area of ​​the injection conduit 14 gradually decreases from a first maximum value at the beginning of the injection conduit 14 to a minimum value (the minimum value is located at the center of the injection conduit 14 downstream of the valve seat 10 and corresponds to the throat section), and in the diverging terminal section, the area of ​​the injection conduit 14 gradually increases from the minimum value until a second maximum value is reached at the end of the injection conduit 14 (usually, the second maximum value is larger than the first maximum value).

[0045] Preferably, the injection duct 14 has an intermediate section, interposed between a (everywhere) converging initial section and a (at least initially) diverging terminal section, having a constant area equal to a minimum value and having a non-zero axial length.

[0046] In other words, the converging initial section of the injection pipe 14 extends from the area where the area of ​​the injection pipe 14 is equal to the first maximum value to the area where the area of ​​the injection pipe 14 is equal to the minimum value (i.e., the throat section) and thus the middle section begins; however, the diverging terminal section of the injection pipe 14 extends from the area where the area of ​​the injection pipe 14 is equal to the minimum value (i.e., the throat section) and thus the middle section ends at least in the area where the area of ​​the injection pipe 14 is equal to the second maximum value.

[0047] According to a preferred embodiment, the (at least initially) diverging terminal section of the injection duct 14 is axially longer than the (everywhere) converging initial section of the injection duct 14 (i.e. the hydrogen has to travel a greater length through the diverging terminal section of the injection duct 14 than through the converging initial section).

[0048] Inside the sleeve 12 there is an end region 13 of an injection duct 14 which is located downstream of the gate 9 and ends at the injection nozzle 3 .

[0049] The convergence-divergence alternation in the injection duct 14 constitutes a Laval nozzle, which is a supersonic exhaust nozzle consisting of a tube with a central bottleneck, similar to an asymmetric hourglass; its steady-state operation (in the throat section, that is, in the smaller section, the speed of the hydrogen is equal to the speed of sound) allows to accelerate the hydrogen to supersonic speed, conveying the exhaust flow and thus converting its thermal and pressure energy into kinetic energy.

[0050] exist Figure 2-5In the embodiment shown, the gate 9 has an initial portion, a middle portion, and an end portion, the initial portion being connected to the valve seat 10 and having a gradually increasing outer diameter along the longitudinal axis 2, the middle portion having a constant outer diameter along the longitudinal axis 2, and the end portion being closer to the injection nozzle 3 and having a gradually decreasing outer diameter along the longitudinal axis 2. However, the sleeve 12 has an initial portion, a middle portion, and an end portion, the initial portion being arranged immediately downstream of the valve seat 10 and located at the middle portion of the gate 9 and also having a constant inner diameter along the longitudinal axis 2, the middle portion having a gradually decreasing inner diameter along the longitudinal axis 2, and the end portion being closer to the injection nozzle 3, defining an end region 13 of the injection conduit 14, and having a constant inner diameter along the longitudinal axis 2.

[0051] exist Figure 2-5 In the illustrated embodiment, in the diverging terminal section, the area of ​​the injection pipe 14 gradually increases from a minimum value until it reaches a second maximum value, which is preferably reached at the end of the injection pipe 14 (i.e., the second maximum value can be reached at the end of the injection pipe 14 at the injection nozzle 3, or it can be reached before the end of the injection pipe 14 upstream of the injection nozzle 3).

[0052] exist Figure 6 In the alternative embodiment shown, the gate 9 basically has only an initial portion and a middle portion, the initial portion is connected to the valve seat 10 and has a gradually increasing outer diameter along the longitudinal axis 2, and the middle portion has a constant outer diameter along the longitudinal axis 2; Figure 6 In the embodiment shown, the end portion closer to the injection nozzle 3 and having a tapering outer diameter along the longitudinal axis 2 is substantially absent. Figure 6 In the embodiment shown, the shutter 9 ends in a truncated shape and therefore has a flat bottom wall which is closer to the injection nozzle.

[0053] exist Figure 6 In the alternative embodiment shown, the area of ​​the injection duct 14 increases gradually from a minimum value to a second maximum value at the flat bottom wall of the shutter 9 in the diverging terminal section.

[0054] In the embodiment shown in the figures, the end region 13 of the injection conduit 14 is coaxial with the longitudinal axis 2 of the fuel (or other gaseous fuel) injector 1, thereby giving the hydrogen spray leaving the injection nozzle 3 an orientation coaxial with the longitudinal axis 2 of the fuel injector 1. According to a different embodiment, not shown, the end region 13 of the injection conduit 14 is inclined (angled) relative to the longitudinal axis 2 of the fuel injector 1 (i.e. the end region 13 of the injection conduit 14 forms an acute angle with the longitudinal axis 2 of the fuel injector 1), thereby giving the fuel spray leaving the injection nozzle 3 an orientation inclined (angled) relative to the longitudinal axis 2 of the fuel injector 1.

[0055] exist Figure 3In the alternative embodiment shown, the sleeve 12 comprises at least one lateral through-duct 15, which passes through the sleeve 12 from one side to the other side and opens into the end region 13 of the injection duct 14; i.e., the lateral duct 15 puts the combustion chamber of the corresponding cylinder (around the terminal portion of the fuel injector 1) in communication with the end region 13 of the injection duct 14. According to a preferred embodiment, each lateral duct 15 is inclined relative to the longitudinal axis 2 of the fuel injector 1 and forms an acute angle with the longitudinal axis 2 of the fuel injector 1; in particular, the acute angle between each lateral duct 15 and the longitudinal axis 2 of the fuel injector 1 ranges from 20 to 40 degrees, preferably 30 degrees.

[0056] Typically, the sleeve 12 includes a plurality of lateral ducts 15, which may be arranged along the entire circular extension of the sleeve 12 (i.e., they may form a closed circle, thereby having a symmetrical distribution around the longitudinal axis 2), or may be arranged only along a limited portion of the circular extension of the sleeve 12 (i.e., they may form a circumferential arc, thereby having an asymmetrical distribution around the longitudinal axis 2).

[0057] The role of the lateral duct 15 is to allow the air (i.e., oxidant) to be drawn from the combustion chamber of the corresponding cylinder (around the tip of the fuel injector 1) to the end region 13 of the injection duct 14, so as to allow a first mixing between the hydrogen (fuel) and the air (oxidant) already inside the end region 13 of the injection duct 14, thereby improving the overall mixing between the hydrogen and the air. In other words, the presence of the lateral duct 15 allows improving the overall mixing between the air (oxidant) and the hydrogen (fuel) present in the combustion chamber of the corresponding cylinder (around the tip of the fuel injector 1).

[0058] It is noteworthy that, as mentioned above, the injection duct 14 has an initially converging and subsequently diverging shape to constitute a Laval nozzle, thereby determining an increase in the fuel velocity and a decrease in the fuel pressure, thereby forming a (relative) low pressure in the end region 13 of the injection duct 14, which draws air from the combustion chamber of the corresponding cylinder (around the end part of the fuel injector 1) through the lateral duct 15.

[0059] If the lateral ducts 15 are symmetrically distributed around the longitudinal axis 2 of the fuel (fuel) injector 1, the presence of the lateral ducts 15 does not affect the direction of the fuel spray coming out of the injection nozzle 3; however, if the lateral ducts 15 are asymmetrically distributed around the longitudinal axis 2 of the fuel injector 1 (i.e. there are more lateral ducts 15 or larger lateral ducts 15 on one side of the sleeve 12 than on the opposite side of the sleeve 12), the presence of the lateral ducts 15 affects the direction of the fuel spray coming out of the injection nozzle 3, and the fuel spray can therefore present an inclined (angled) direction relative to the longitudinal axis 2 of the fuel (fuel) injector 1. In other words, the asymmetrical distribution of the lateral ducts 15 relative to the longitudinal axis 2 of the fuel (fuel) injector 1 allows to give the fuel spray coming out of the injection nozzle 3 an inclination relative to the longitudinal axis 2 of the fuel (fuel) injector 1.

[0060] In order to obtain a fuel spray coming out of the injection nozzle 3 with a given inclination relative to the longitudinal axis 2 of the fuel (fuel) injector 1, an asymmetric distribution of the lateral duct 15 relative to the longitudinal axis 2 of the fuel (fuel) injector 1 may be adopted, an inclination of the end area 13 of the injection duct 14 relative to the longitudinal axis 2 of the fuel (fuel) injector 1 may be adopted (as described above), or a combination of these two solutions may be adopted.

[0061] exist Figure 2 and Figure 3 In the embodiment shown, the outer edge 16 of the injection nozzle 3 is smooth. Figure 4 In the embodiment shown, the outer edge 16 of the injection nozzle 3 is jagged (i.e. has a more or less irregular series of protrusions and depressions). In other words, the outer edge 16 of the injection nozzle 3 has a series of convex corners (which can be more rounded or more pointed) which give the outer edge 16 a sawtooth shape. The jagged (uneven, uneven) shape of the outer edge 16 of the injection nozzle 3 allows to improve the mixing of the fuel with the air (combustion aid) because it creates greater turbulence in the fuel spray. In addition, the jagged (uneven, uneven) shape of the outer edge 16 of the injection nozzle 3 allows to reduce the noise (i.e. pressure waves in the audible range) generated during the fuel spray: the jagged shape increases the mixing process and weakens the formation of large-scale structures (related to the generation of low-frequency noise in the audible range), and excites small-scale structures (related to the generation of high-frequency noise outside the audible range).

[0062] exist Figure 2 , Figure 3 and Figure 4 In the embodiment shown, the end region 13 of the injection duct 14 is connected to the outside (ie, to the combustion chamber) through a single opening for injecting fuel; Figure 2 , Figure 3 and Figure 4In the embodiment shown, the injection nozzle 3 has a single opening for injecting fuel. Figure 5 In the alternative embodiment shown, the end region 13 of the injection nozzle 14 is connected to the outside (ie, to the combustion chamber) for injecting fuel through a series of openings 17 arranged side by side and which may have different sizes (diameters); Figure 5 In the embodiment shown, the injection nozzle 3 has a series of openings 17 arranged side by side and which may have different sizes (diameters). Figure 5 In the embodiment shown, a "multi-hole" arrangement is provided, in which the fuel is discharged from the end region 13 of the injection duct 14, which constitutes the injection nozzle 3, through a series of openings 17 arranged side by side and of different sizes (diameters). Figure 5 In the embodiment shown, the openings 17 are parallel to each other, but alternatively they may be inclined (non-parallel) with respect to each other.

[0063] In the above described embodiments, the injection of hydrogen is mentioned, but the fuel injector 1 can be used to inject any other type of gaseous fuel, such as methane.

[0064] The embodiments described herein may be combined with each other without departing from the protection scope of the present innovation.

[0065] The fuel injector 1 described above has many advantages.

[0066] Firstly, the above-mentioned fuel injector 1 generates a fuel spray that allows to optimize the mixing between air (combustion aid) and hydrogen (fuel). In fact, the above-mentioned fuel injector 1 gives the hydrogen (fuel) spray a high discharge velocity, which is conducive to mixing with air, increasing the swirl motion. In addition, the above-mentioned fuel injector 1 allows to guide the hydrogen (fuel) spray at a certain angle relative to the longitudinal axis 2 of the fuel injector 1, so that the fuel spray can be given an optimal direction, regardless of the position and orientation of the fuel (fuel) injector 1 at the top of the cylinder (tendency, the fuel spray must be sprayed into the piston laterally rather than in the center in order to maximize turbulence and thus obtain a better mixing of fuel and air).

[0067] Finally, the above-described fuel injector 1 is simple and inexpensive to produce as compared to similar known hydrogen (fuel) injectors, since it has few structural differences which are easy to manufacture.

Claims

1. A fuel injector for gaseous fuel, comprising: Injection nozzle (3); a support body (4) having a tubular shape, having a longitudinal axis (2) and in which a supply channel (5) terminating in the injection nozzle (3) is arranged; an injection valve (7) configured to regulate the flow of the gaseous fuel through the injection nozzle (3) and provided with a movable shutter (9) arranged outside the support body (4) and a valve seat (10) obtained in the support body (4); a tubular sleeve (12) arranged around the end of the support body (4), the shutter (9) being completely contained in the tubular sleeve (12) and terminating at the injection nozzle (3); and an actuator (6), the actuator (6) being configured to move the gate (9) between a closed position of the injection valve (7) and an open position of the injection valve (7), in which the gate (9) is pressed against the valve seat (10), and in which the gate (9) is separated from the valve seat (10); wherein the gate (9) comprises a first portion and a second portion, the first portion facing the valve seat (10) and being formed to be sealingly coupled to the inner surface of the valve seat (10) when the injection valve (7) is in a closed position, and the second portion facing the inner surface of the sleeve (12) and always maintaining a given distance from the inner surface of the sleeve (12); and wherein the inner surface of the valve seat (10) and the inner surface of the sleeve (12) define an annular injection channel (14), and when the injection valve (7) is in the open position, an initial portion of the injection channel (14) is formed, and when the injection valve (7) is in the open position, the gas fuel flows along the injection channel (14) toward the injection nozzle (3); The fuel injector (1) is characterized in that the injection duct (14) formed when the injection valve (7) is in the open position has a converging initial section and an at least initially diverging terminal section, in which the area of ​​the injection duct (14) gradually decreases from a first maximum value at the beginning of the injection duct (14) to a minimum value, and in which the area of ​​the injection duct (14) increases from the minimum value until a second maximum value is reached.

2. The fuel injector (1) according to claim 1, wherein: The injection conduit (14) has an intermediate section interposed between the converging initial section and the diverging terminal section, having a constant area equal to a minimum value, and having a non-zero axial length separating the initial section and the terminal section.

3. The fuel injector (1) according to claim 1, wherein: The end region (13) of the injection duct (14) is located inside the sleeve (12), the end region (13) being located downstream of the gate (9) and terminating at the injection nozzle (3).

4. The fuel injector (1) according to claim 3, wherein: The end region (13) of the injection duct (14) is located downstream of the shutter (9) coaxially with the longitudinal axis (2) of the fuel injector (1).

5. The fuel injector (1) according to claim 3, wherein: The end region (13) of the injection duct (14) is located downstream of the gate (9), is inclined relative to the longitudinal axis (2) and forms an acute angle with the longitudinal axis (2).

6. The fuel injector (1) according to claim 3, wherein: The sleeve (12) comprises at least one lateral through-duct (15) which passes through the sleeve (12) from one side to the other side and opens into the end region (13) of the injection duct (14) downstream of the shutter (9).

7. The fuel injector (1) according to claim 6, wherein: The lateral duct (15) is inclined relative to the longitudinal axis (2) and forms an acute angle with the longitudinal axis (2).

8. The fuel injector (1) according to claim 7, wherein: The acute angle between the lateral duct (15) and the longitudinal axis (2) ranges from 20 to 40 degrees, preferably 30 degrees.

9. The fuel injector (1) according to claim 6, wherein: The sleeve (12) comprises a plurality of lateral ducts (15) which are symmetrically distributed around the longitudinal axis (2).

10. The fuel injector (1) according to claim 6, wherein: The sleeve (12) comprises a plurality of lateral ducts (15) which are asymmetrically distributed around the longitudinal axis (2).

11. The fuel injector (1) according to claim 10, wherein: There are more lateral ducts (15) or larger lateral ducts (15) on one side of the sleeve (12) than on the opposite side of the sleeve (12).

12. The fuel injector (1) according to claim 1, wherein: The outer edge (16) of the injection nozzle (3) is jagged and has a series of protrusions and depressions.

13. The fuel injector (1) according to claim 1, wherein: The divergent terminal section of the injection conduit (14) is axially longer than the converging initial section of the injection conduit (14).

14. The fuel injector (1) according to claim 1, wherein: The convergence-divergence alternation in the injection pipe (14) constitutes a supersonic Laval nozzle.

15. The fuel injector (1) according to one of claims 1 to 14, wherein: The gate plate (9) exclusively comprises: an initial portion coupled to the valve seat (10) and having a gradually increasing outer diameter along the longitudinal axis (2); and A middle portion having a constant outer diameter along the longitudinal axis (2).

16. The fuel injector (1) according to one of claims 1 to 14, wherein: The shutter (9) ends in a truncated shape and has a flat bottom wall closer to the injection nozzle.

17. The fuel injector (1) according to one of claims 1 to 14, wherein: In the diverging terminal section, the area of ​​the injection duct (14) increases stepwise from the minimum value to the second maximum value.

18. The fuel injector (1) according to one of claims 1 to 14, wherein: The gate has a bulb-like shape and comprises: an initial portion, the initial portion being coupled to the valve seat (10) and having a gradually increasing outer diameter along the longitudinal axis (2); a middle portion having a constant outer diameter along the longitudinal axis (2); and An end portion, which is closer to the injection nozzle (3) and has a gradually decreasing outer diameter along the longitudinal axis (2).

19. The fuel injector (1) according to claim 18, wherein: In the diverging terminal section, the area of ​​the injection duct (14) gradually increases from the minimum value until reaching the second maximum value, which is preferably reached at the end of the injection duct (14).

20. The fuel injector (1) according to one of claims 1 to 14, wherein: The inner surface of the sleeve (12) comprises: an initial portion having a constant inner diameter along the longitudinal axis (2); a middle portion having a reduced inner diameter along the longitudinal axis (2); and An end portion, the terminal portion being closer to the injection nozzle (3) and having a constant inner diameter along the longitudinal axis (2).

21. The fuel injector (1) according to one of claims 1 to 14, wherein: The injection nozzle (3) is provided with a series of openings (17) which are arranged side by side and may have differentiated sizes.

22. The fuel injector (1) according to one of claims 1 to 14, wherein: The second maximum value is greater than the first maximum value.

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