Patent Application
20180051666
The invention generally relates to fuel injectors, and more particularly to a rotary needle fuel injector.
In some internal combustion engines, a specific fuel injection rate is desired to help achieve the operating targets. For example, modern diesel engines often use injection strategies in order to meet combustion emissions and noise constraints. In a conventional fuel injector, a desired fuel injection rate shape over time is approximated by executing multiple injection pulses at specified times and durations. It can be difficult to achieve a desired injection profile with this approach due to limitations in timing the activation of an injector needle relative to the timing of a combustion process.
Conventional fuel injectors for diesel engines include an internal needle which moves linearly within an injector housing. When the needle is positioned against a seat, which acts as a sealing surface on the housing, the fuel that is supplied to the housing is blocked. As the needle moves away from the seat, a pathway past the needle and through one or more nozzle holes is created to a downstream combustion chamber. A pressure difference between the high pressure fuel supply and the combustion chamber drives the fuel through the nozzle holes into the combustion chamber.
A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below.
Embodiments of the disclosure are related to systems and methods for a rotary needle fuel injector that achieves a desired injection profile.
One embodiment includes a rotary needle fuel injector having a housing including a wall having a non-circular aperture extending through the wall, and a rotatable rod inside the housing and having a bore through which fuel is supplied. The rotatable rod has an aperture communicating with the bore and in selective communication with the non-circular aperture in the housing wall.
Another embodiment includes a rotary needle fuel injector having a housing including a wall having a plurality of non-circular apertures extending through the wall, and a rotatable rod inside the housing and having a bore through which fuel is supplied. The rotatable rod has a plurality of apertures communicating with the bore and in selective communication with the non-circular apertures in the housing wall. The non-circular apertures each include an axis of symmetry extending along a direction of rotation of the rotatable rod, an axis of asymmetry perpendicular to the axis of symmetry, and a ratio of a cross-sectional area of a first region of the non-circular aperture to a cross-sectional area of a second region of the non-circular aperture ranges from about 1:10 to about 1:1.5.
The details of one or more features, aspects, implementations, and advantages of this disclosure are set forth in the accompanying drawings, the detailed description, and the claims below.
One or more specific embodiments will be described below. Various modifications to the described embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the described embodiments. Thus, the described embodiments are not limited to the embodiments shown, but are to be accorded the widest scope consistent with the principles and features disclosed herein.
An embodiment of a rotary needle fuel injector 100 is shown in
The operation of the rotary needle fuel injector 100 results in selective communication of apertures 130, 160 to provide the desired injection to the combustion chamber.
As illustrated, the size of the non-circular aperture 130 in the housing 110 generally increases in the direction of rotation 190 of the rotatable rod 140. To state it yet another way, the non-circular aperture 130 in the housing generally increases from a smaller size to a larger size in the direction of rotation 190 of the rotatable rod 140. As illustrated, the non-circular aperture is tear-drop shaped. Additionally, the cross-sectional shape of the non-circular aperture 130 extending through the housing wall 120 remains substantially constant through the thickness of the housing wall 120. In other embodiments, the cross-sectional shape of the non-circular aperture 130 may increase in size, and/or decrease in size through the thickness of the housing wall 120. Furthermore, the shape of each of the non-circular apertures 130 may be the same or different. Additionally, in other embodiments the shape of the at least one aperture 160 in the rotatable rod 140 may be non-circular in shape.
The non-circular aperture 130 further defines a mid-point 240 which is defined as halfway between the leading distal end 231 and the trailing distal end 232. A perpendicular axis 220 runs through the mid-point 240 perpendicular to the axis 210. The perpendicular axis 220 defines an axis of asymmetry of the aperture 130. The axis of asymmetry 220 is substantially perpendicular to the direction of fuel flow from the bore 150 through the apertures 160 and 130. The non-circular aperture 130 further defines a width W in a direction perpendicular to the direction of rotation 190. The width W corresponds to the widest portion of the non-circular aperture 130 in a direction perpendicular to the direction of rotation 190. The width W may lie along the axis of asymmetry 220 of the non-circular aperture or may be located elsewhere within the non-circular aperture 130. In the illustrated embodiment, the width W can be 70 microns to 200 microns. In other embodiments, the widest section or width W of the non-circular aperture 130 in the direction perpendicular to the direction of rotation 190 may be outside of the previous range. The region of the aperture 130 between the leading distal end 231 and the perpendicular axis 220 is defined as a first region 250. The region between the trailing distal end 232 and the perpendicular axis 220 is defined as a second region 260. A ratio of the area of the first region 250 to the area of the second region 260 may be 1:50 to 1:1.3. In other embodiments, the ratio of the area of the first region 250 to the area of the second region 260 may be 1:10 to 1:1.5.
The specific shape of the non-circular aperture 130 may be chosen to determine the rate at which a cross-section of the non-circular aperture 130 in selective communication with the aperture 160 changes for each unit of arc of rotation of the rotatable rod 140. This allows for the fine tuning of the fuel injection rate profile. As an alternative to the illustrated tear-drop shape, the non-circular aperture 130 may include one or more other non-circular shapes (e.g., oval, ovoid, ellipse, triangle, parallelogram, rhombus, rectangle, square, diamond, and combinations thereof). The specific shape can be customized to achieve the desired injection rate profile.
During the operation of the rotary needle fuel injector 100, the apertures 130, 160 are in varying degrees of overlap.
The apertures 130, 160 of the rotary needle fuel injector 100 may be formed using various computer-controlled manufacturing techniques (e.g., laser drilling). Techniques such as computer-controlled laser drilling allow for the aperture shapes/profiles to be customized based on the performance requirements of the engine. Control of the aperture shapes/profiles through the thickness of the housing wall 110 and the rod wall 145 allows the volume and/or turbulence of the fuel flow through the injector 100 to be customized.
It is believed that embodiments described herein and many of their attendant advantages will be understood by the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the components without departing from the disclosed subject matter or without sacrificing all of its material advantages. The form described is merely explanatory, and it is the intention of the following claims to encompass and include such changes.
