WO2019030078A1

WO2019030078A1 - Fuel injector nozzle

Info

Publication number: WO2019030078A1
Application number: PCT/EP2018/070890
Authority: WO
Inventors: James DOETSCH; Kevin Peterson
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2017-08-08
Filing date: 2018-08-01
Publication date: 2019-02-14
Anticipated expiration: 2020-02-08

Abstract

A fuel injector including a fuel injector housing, a valve seat formed at one end of the fuel injector housing, and a valve body disposed in the fuel injector housing and operable to open and close a spray hole in the valve seat. The spray hole includes one or more surface features that permit control of the fuel injector spray pattern and spray characteristics.

Description

FUEL INJECTOR NOZZLE

BACKGROUND

[001] Many internal combustion engines are supplied with fuel using fuel injection systems that include one or more fuel injectors that are configured to spray fuel directly into an engine cylinder. The spray characteristics required for an engine varies depending on engine conditions, for example as shown in Fig. 13.

[002] The spray pattern and characteristics of a fuel injector nozzle are determined by shape of the valve seat and the spray holes formed in the valve seat. The characteristics of the spray can contribute greatly to engine-out emissions. For example, controlling certain characteristics can minimize the particulate and gaseous emissions generated by the internal combustion engine that is supplied by the fuel injector. Some of the characteristics that can be controlled include the flow of the fuel within the spray hole of the valve seat, the breakup/atomization of the spray as it exits the spray hole, the penetration of the spray in the combustion chamber and tip wetting of the valve seat.

SUMMARY

[003] A fuel injector nozzle includes features that reduce the potential for unburned liquid fuel in the combustion chamber of a direct injection combustion engine. Liquid fuel at the time of combustion is associated with the production of particulate matter, a regulated emission. By altering the shape of the spray hole, the amount of wetting of the injector tip may be decreased, and the penetration distance of the spray may be decreased, reducing the amount of liquid fuel impingement on internal engine surfaces and reducing the likelihood of liquid fuel persisting in the cylinder.

[004] The main improvements and advantages of the disclosed fuel injector nozzle lie in using a new understanding of fuel injector wetting to mitigate the wetting and reduce engine-out particulates. The problem of fuel injector wetting has not been studied in great depth, and recent testing by the inventors has shed new light on the problem, and the ways to solve the problem. Small changes to the shape of the spray hole will change the way the fuel exits the injector compared to current designs, resulting in less tip wetting and reduced spray penetration.

[005] In some aspects, the fuel injector nozzle includes a valve seat having a spray hole provided in an improved shape. In some embodiments, the spray hole is shaped so as to create a curved, smooth inlet and/or outlet edge having a large entrance and/or exit radius to minimize cavitation and turbulence generation at the nozzle inlet. Advantageously, the spray hole having the improved shape may minimize or better control cavitation at inlet, and thus may improve spray quality. In some embodiments, a step feature is provided within the spray hole passageway that is configured to allow controlled cavitation generation, which in turn allows for cavitation reduction via the ability to control cavitation. In some embodiments, the shape of the outlet of the spray hole (e.g., the shape of the counter bore) is controlled to address tip wetting. For example, in some embodiments, a feature is added to the outlet edge that reduces the surface area immediately around the counter bore edge. In other embodiments, a helical feature is provided in the spray hole passageway that increases angular momentum of the fuel spray.

[006] By providing a valve seat spray hole shape that controls the spray pattern and

characteristics of a fuel injector nozzle, the characteristics of the spray can be controlled and thus the engine-out emissions may be reduced.

BRIEF DESCRIPTION OF FIGURES

[007] Fig. 1 is a perspective view of a fuel injector.

[008] Fig. 2 is an axial cross-sectional view of a fuel injector.

[009] Fig. 3 is an enlarged perspective view cross sectional view of the valve seat of the fuel injector.

[0010] Fig. 4 is a schematic cross sectional view of a portion of the valve seat including a spray hole, where a broken line represents the valve body in an open position and an arrow represents the direction of fuel flow.

[0011] Fig. 5 is a schematic cross sectional view of a portion of an alternative embodiment valve seat including a spray hole.

[0012] Fig. 6 is a schematic cross sectional view of a portion of another alternative embodiment valve seat including a spray hole. [0013] Fig. 7 illustrates an exterior view of a portion of a fuel injector including an outlet of a spray hole before a spraying event.

[0014] Fig. 8 illustrates an exterior view of the portion of the fuel injector of Fig. 7 including the outlet of the spray hole during a spraying event.

[0015] Fig. 9 illustrates an exterior view of the portion of the fuel injector of Fig. 7 including the outlet of the spray hole following a spraying event.

[0016] Fig. 10 is a schematic cross sectional view of a portion of another alternative embodiment valve seat including a spray hole.

[0017] Fig. 1 1 is a schematic cross sectional view of a portion of another alternative embodiment valve seat including a spray hole.

[0018] Fig. 12 is a schematic cross sectional view of a portion of another alternative embodiment valve seat including a spray hole.

[0019] Fig. 13 is a table outlining fuel injector spray requirements for various engine conditions.

DETAILED DESCRIPTION

[0020] Referring to Figs. 1 -3, a fuel injector 1 is used for injection of fuel such as gasoline into the combustion chamber of an internal combustion engine (not shown). The fuel injector 1 has a tubular housing 2 that supports a valve seat 4 at one end thereof. The valve seat 4 includes at least one spray hole 20 that serves as a nozzle of the fuel injector 1, or a portion thereof. The fuel injector 1 includes a valve body 10 operable by a valve needle 12 to move between a first position abutting the valve seat 4 (Fig. 2) in which the spray hole 20 is closed, and a second position spaced apart from the valve seat 4 (Fig. 3) in which the spray hole 20 is open. In the illustrated embodiment, the fuel injectorl is an inward opening fuel injector 1. When the fuel injector 1 is operated, valve body 3 is lifted upward and away from valve seat 4 face via the valve needle 12. The valve seat 4 includes a valve body facing surface 6, an opposed, outward facing surface 8, and the spray hole 20 that forms a passageway 26 between the valve body surfaces 6, 8. The spray hole 20 includes an inlet 22 at the valve body facing surface 6, and an outlet 24 at the outward facing surface 8. In some embodiments, a counter bore 28 is formed at the spray hole outlet 24. The valve seat 4 also includes one or more surface features in the vicinity of the spray hole 20 that permit control of the spray pattern and characteristics, as discussed in detail below.

[0021] Referring to Fig. 4, the valve seat 4, and particularly the inlet 22 of the spray hole 20 of the valve seat 4, can be shaped so as to create a smoothly curved inlet edge. In some

embodiments, the inlet 22 may include a large entrance radius to minimize cavitation and turbulence generation at the nozzle inlet 22.

[0022] Referring to Fig. 5, cavitation occurs to some degree in most injector designs, but it is not highly controlled. It can be difficult to control cavitation since it is not only a function of nozzle shape, but is also a function of fuel temperature and in-cylinder pressure, which are not fully controllable.

[0023] In some embodiments, the valve seat 4 is shaped to address cavitation. For example, the spray hole inlet 22 can be shaped so as to create a smooth inlet edge as discussed above with respect to Fig. 4, and may also include a step feature 30 within the spray hole passageway 26. In some embodiments, the step feature 30 is an annular ridge having a rectangular cross-sectional profile that protrudes into the spray hole passageway 26 in a direction perpendicular to the fluid flow direction. In the figures, the fluid flow direction is shown by an arrow. By providing the step feature 30, a known amount of cavitation can be created. That is, the shape of the spray hole 20 allows for a controlled approach to cavitation generation (counter bore or no counter bore). This can be advantageous since the vapor layer produced by cavitation may decrease tip wetting. Controlled cavitation generation may also provide a more stable flow through the spray hole 20.

[0024] Referring to Figs. 6-9, injector tip wetting at the outlet of the counter bore 28 is a major soot contributor. In some embodiments, a surface feature is added to the outlet 24 that reduces the surface area immediately around the counter bore edge (Fig. 6). For example, the surface feature may be a protrusion 32 that encircles the counter bore edge and protrudes in the direction of fluid flow. A radially outward surface 34 of the protrusion 32 is beveled. A thickness of the protrusion 32 is minimum at the protrusion terminal end 36 and maximum at the nozzle outward facing surface 8. In addition, the inner surface 38 of the protrusion 32 is flush with, and provides an extension of, the spray hole outlet 24 and passageway inner surface 26. In the illustrated embodiment, the protrusion 32 has a right triangular cross-sectional profile. [0025] By providing this protrusion 32, the growth of a fuel ring (Fig. 9) around the spray hole outlet 24 is minimized, and the spreading/drying is maximized. Advantageously, tip wetting can be minimized without interfering with any other spray parameters.

[0026] The shape of the feature (i.e., the protrusion 32) may need to be optimized to avoid generation of hot spots and/or to ensure durability of features even when the features are small in size.

[0027] Referring to Fig. 10, another contributor to tip wetting is due to the interaction between the fuel spray and outlet edge 24. By providing a spray hole 20 having an outlet 24 formed to provide a gradual outlet curvature, this interaction may be reduced/eliminated and tip wetting can be further minimized.

[0028] Referring to Fig. 1 1, in some embodiments, the spray hole having a gradual outlet curvature may be combined with large radius at the spray hole inlet 22. In some embodiments, the radius of the outlet curvature may be the same as the radius of the inlet curvature (shown). In other embodiments, the radius of the outlet curvature may be the different from the radius of the inlet curvature (not shown).

[0029] The particular shape of the spray hole inlet and outlet curvatures may be optimized to minimize flow rate reduction and/or potential clogging issues.

[0030] Referring to Fig. 12, it can be advantageous to increase the angular momentum of the fuel passing through the spray hole 20 since increased angular momentum will increase spray breakup and/or minimize penetration.

[0031] The angular momentum of fluid passing through the spray hole 20 may be increased by either altering the fuel path to the spray hole outlet 24, or by adding channels to the spray hole passageway surface 26. For example, features including channels/grooves (not shown) or a helical protrusion 40 can be added to the surface of the spray hole passageway 26. The features 40 serve to alter the fuel path through the nozzle to generate angular momentum. In the illustrated embodiment, the helical protrusion 40 has a triangular cross-sectional shape, but the helical protrusion 40 is not limited to this cross-sectional shape. For example, the helical protrusion 40 may have a rectangular cross sectional shape, a curved cross sectional shape or other appropriate shape.

[0032] The specific shape and dimensions of the angular momentum increasing features may be optimized to avoid a widened plume angle and avoid or minimize an increase cavitation. [0033] The features described herein with respect to Figs. 4-6 and 10-12 may be used alone or in combination to control the characteristics of the fuel spray and thus reduce the engine-out emissions.

[0034] Selective illustrative embodiments of the fuel injector and valve seat are described above in some detail. It should be understood that only structures considered necessary for clarifying the fuel injector and valve seat have been described herein. Other conventional structures, and those of ancillary and auxiliary components of the fuel injector and valve seat, are assumed to be known and understood by those skilled in the art. Moreover, while a working example of the fuel injector and valve seat have been described above, the fuel injector and valve seat are not limited to the working examples described above, but various design alterations may be carried out without departing from the fuel injector and valve seat as set forth in the claims.

Claims

We claim,

1. A fuel injector comprising a fuel injector housing; a valve seat disposed in the fuel injector housing, the valve seat including a valve body- facing surface, an outward facing surface opposed to the valve body facing surface, and a spray hole that extends between the valve body- facing surface and the outward facing surface, the spray hole defining a spray hole passageway; and a valve body 3 disposed in the fuel injector housing and operable to move between a first position abutting the valve seat in which the spray hole is closed, and a second position spaced apart from the valve seat in which the spray hole is open; wherein the spray hole comprises a surface feature that permits control of the spray pattern and characteristics.

2. The fuel injector of claim 1 wherein the spray hole comprises an inlet at the valve body facing surface and an outlet at the outward facing surface, and the surface feature includes forming the inlet to have a curved transition from the valve body facing surface to an interior surface of the spray hole passageway.

3. The fuel injector of claim 1 wherein the spray hole passageway is formed having the surface feature, and the surface feature protrudes inward along the passageway and is disposed between an inlet and an outlet of the spray hole passageway.

4. The fuel injector of claim 3, wherein the surface feature is an annular ridge having a rectangular cross-sectional profile.

5. The fuel injector of claim 3, wherein the surface feature extends along a helical path between the inlet and the outlet of the spray hole passageway.

6. The fuel injector of claim 1 , wherein the surface feature is a protrusion that encircles an outlet of the spray hole, where a radially outward surface of the protrusion is beveled.

7. The fuel injector of claim 1 wherein the spray hole comprises an inlet at the valve body facing surface and an outlet at the outward facing surface, and the surface feature includes forming the outlet to have a curved transition from the outward facing surface to an interior surface of the spray hole passageway.

8. The fuel injector of claim 1 wherein the spray hole comprises an inlet at the valve body facing surface and an outlet at the outward facing surface, the surface feature includes forming the inlet to have a curved transition from the valve body facing surface to an interior surface of the spray hole passageway, and forming the outlet to have a curved transition from the outward facing surface to an interior surface of the spray hole passageway.