Patent Application
20070290077
The present invention generally relates to a fuel injection system and more specifically the invention relates to an apparatus and method for injecting a fuel plume into a combustion chamber via a singular gap formed between a flanged portion of a needle valve and a valve seat.
The conventional combustion process in a diesel engine is initiated by the direct injection of fuel into a combustion chamber containing compressed air. The fuel is essentially ignited instantaneously upon injection into a highly compressed combustion chamber, and thus produces a diffusion flame or flame front extending along the plumes of the injected fuel. The fuel is directly injected into the combustion chamber by a fuel injector having a perforated nozzle tip extending into the combustion chamber. The nozzle tip may extend slightly into the combustion chamber from a wall of the chamber located opposite a reciprocating piston of the combustion chamber. The nozzle tip comprises a series of holes from which fuel is extruded into the combustion chamber.
Nozzle tips are commonly designed with the largest number of spray holes having the smallest diameter possible to inject the required fuel quantity at each locomotive engine's speed and load setting in order to preserve the nozzle's wall thickness and strength.
Diesel fuel is injected at 10,000-18,000 psi out through 5 to 7 individual, separate and distinct round orifice holes located at the very bottom of the spray tip. The resultant spray pattern consists of separate and distinct solid plumes of atomized fuel droplets that evaporate and mix with the combustion air at the proper temperature, pressure and air/fuel ratio auto-ignite.
The spray holes are the first components of the injector assembly to ultimately affect the service life and durability of the nozzle assembly. Typically, a spray tip's fuel flow characteristics deteriorate approximately 0.5% per year for the first three years, increasing rapidly to 1% to 1.5% per year by a service life of 5 and 6 years. The service life and long term durability of the hole geometry is strictly a function of the total fuel consumed or injected through each of the spray holes.
The fuel plumes after an extended service life become less of an atomized and turbulent gaseous spray pattern and become more like a solid laminar fuel stream taking more time to break up into small droplets, evaporate and burn. The ignition of a gaseous spray is much more efficient than that of a solid stream of fuel.
In an effort to overcome such short comings, spay tip orifices require very precise machining at great expense. The manufacture of such spray tips requires the creation of spray holes, which must be perfectly round having a precise diameter in order to provide the correct geometry for the proper fuel flow and atomization. Such spray holes require a certain case hardness depth to help prevent premature wear and erosion. This hardening process is very critical. If the case depth is too shallow, the hole will wear prematurely and if too hard will become brittle, the hole will be prone to stress fractures and premature failures.
Thus, what is needed is a method and apparatus capable of providing a durable spray assembly that can deliver a consistent atomized spray plume over the service life of a fuel injector.
The present invention generally relates to a fuel injection nozzle assembly and in particular the invention relates to a poppet type valve assembly capable of producing a circumferential spray pattern. The circumferential spray pattern can maximize the contact surface area and optimize the air and fuel mixture within the combustion chamber.
In greater detail, the fuel injector nozzle assembly includes a nozzle body defining a valve outlet including a valve seat and a longitudinal axis. The needle valve includes a first and second end wherein the needle valve is slidably affixed and housed within the nozzle body about the longitudinal axis. The second end of the needle valve extends though the valve outlet and past the valve seat. A flanged portion is formed at the second end to the needle valve for directing a fuel plume and closing the valve outlet.
The fuel injector nozzle assembly may also include indications about the outside circumference of the needle valve for providing rotational motion as fuel is passed down and along the needle valve. The flanged portion produces a circumferential spray pattern and includes sloping edges for directing a fuel stream into a combustion chamber.
A further embodiment includes a direct fuel injection combustion chamber assembly including a combustion chamber and a piston forming a moving end wall of the combustion chamber. The fuel injector includes a nozzle assembly in communication with the combustion chamber. The nozzle assembly includes a nozzle body defining a valve outlet including a valve seat and a longitudinal axis. The needle valve has a first and second end wherein the needle valve is slidably affixed and housed within the nozzle body about the longitudinal axis with the second end extending though the valve outlet and past the valve seat. A flanged portion formed at the second end of the needle valve and is in communication with the valve seat.
An additional embodiment includes a method of injecting fuel into a combustion chamber. The method includes injecting fuel into a fuel injector nozzle assembly. The method further includes forming a gap between a flanged portion of a needle valve and a valve seat formed on the exterior of a nozzle body. The method further includes forming the gap at a certain fuel pressure created by the injection of the fuel into the fuel injection nozzle assembly. A quantity of fuel is injected out of the formed gap and into the combustion chamber and the formed gap closes as the fuel pressure decreases. The fuel may be ejected in a circumferential spray pattern.
In the Drawings:
Disclosed is a fuel injection nozzle assembly comprising a poppet type valve assembly capable of producing a circumferential spray pattern. The fuel injection nozzle assembly includes a nozzle body defining a valve outlet into which is fitted a needle valve having a flanged portion extending from the nozzle body. The flange portion open and closes the valve outlet as the needle valve travels up and down the nozzle body as dictated by the fuel pressure within the nozzle body. The flanged portion directs a fuel spray into a combustion chamber.
The substantially circumferential spray pattern of the present assembly increases the number of possible ignition points over the full cone-shaped sheet of diesel fuel. The term “substantially circumferential” and “circumferential” are defined herein to include spray patters having radiuses of between about 365 to about 250 degrees. An increased number of ignition points significantly improves the fuel's combustion efficiency. The thin cone-shaped plume produced by the assembly is conducive to rapid fuel droplet evaporation, thus promoting a significant increase in the number of areas reaching the correct air/fuel ratio necessary to initiate the start of ignition in a diesel engine's combustion process.
A further advantage of the present assembly is the lack of significant corrosion within the injection gap. Orifice spray holes are prone to erosion, wear and corrosion due to their size, manufacturing process and nozzle material characteristics. The single opening injection gap of the present assembly can be manufactured and produced from significantly harder materials combined with an additional surface hardening process to produce higher surface hardness levels.
Additionally, the geometry of the single opening injection gap distributes the fluid forces evenly about the contact surfaces. Deterioration of the nozzle spray hole geometry is directly related to the amount of fuel consumed, with a resultant decrease in fuel economy and emissions. An additional advantage of the present assembly includes opportunities to lower manufacturing and assembly costs due to the simpler manufacturing design of the nozzle assembly.
Referring now in greater detail to the drawings in which like numerals indicate like parts throughout the several views,
During the injection event, the injector's plunger is pushed downward by the camshaft lobe creating a significant increase in the fuel supply pressure and flow through the end of the plunger bushing, around and through the check valve cutouts, down through the multiple flow passages of the check valve cage, the valve spring cage, and the spray tip itself, and finally into the spray tip's fuel cavity. The spray tip's fuel cavity is sealed by the needle valve seat angle contacting a matching seat angle inside the spray tip. The needle valve is held in place by the valve spring and valve spring seat.
As the fuel supply pressure increases, it exerts pressure on the needle valve to lift up off its seat. Once the fuel supply pressure exceeds 3400-3000 psi, the needle is lifted and pushed up against the valve spring and the fuel is then injected down through the spray tip fuel sac and out through the orifice holes. Once the pressure drops below 3400-3000 psi, the needle then closes and reseats on the spray tip's seat angle preventing any possibility of a secondary injection event.
As illustrated, the nozzle body 6(a-b) may be formed from two parts including the spray tip housing 6a and the spring valve housing 6b. The nozzle body 6 defines a valve outlet 3 at the end of the nozzle body 6 adjacent to the combustion chamber 10. The nozzle body 6 further includes a horizontal axis 7.
A needle valve 4 is housed within and is aligned along the longitudinal axis 7 of the nozzle body 6. The needle value 4 includes a first and second end wherein the first end is substantially contained within a cavity formed within the spring value housing 6b and the second end of the needle valve 4 is substantially housed within a cavity formed within the spray tip housing 6a of the nozzle body 6(a-b). The needle valve 4 further includes a flanged portion 8 which is located at the second end of the needle valve and is exposed to the combustion chamber 10. The flanged portion 8 of the needle valve 4 works in cooperation with the valve seat 5 to form a seal to regulate the injection of fuel into the combustion chamber 10. The valve seat 5 is located at the end of the valve opening 8 adjacent to the combustion chamber 10.
The needle valve 4 is slidably affixed within the nozzle body 6 such that the needle valve 4 may be raised or lowered within nozzle body 6. The movement of the needle value 4 is determined by the pressure of the fuel within the nozzle body 6 or spray tip housing 6a. The needle valve 4 moves down towards the combustion chamber 10 as the pressure builds within the spray tip housing 6a. Typically the needle valve 4 will move down or open when the pressure within the spray tip housing 6a reaches a psi of greater than 2,900.
A fuel injector 30 may include a flanged portion 8 extending directly into the combustion chamber 10 through an opening 33 in the cylinder end wall 36. The fuel injector 30 may be concentric or parallel with the longitudinal axis 17 of the combustion chamber 10 or may extend at an acute angle with respect to the longitudinal axis 17 of the combustion chamber. Further, the fuel injector 30 may be of any conventional type. For example, the fuel injector 30 may be of the mechanically actuated, hydraulically actuated, or common rail type, and may be designed for single mode or mixed mode operations.
While Applicants have set forth embodiments as illustrated and described above, it is recognized that variations may be made with respect to disclosed embodiments. Therefore, while the invention has been disclosed in various forms only, it will be obvious to those skilled in the art that many additions, deletions and modifications can be made without departing from the spirit and scope of this invention, and no undue limits should be imposed except as set forth in the following claims.
This application claims priority to U.S. Provisional Patent Application Ser. No. 60/694,497 filed Jun. 28, 2005, the contents of which are hereby incorporated in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60694497 | Jun 2005 | US |
