Patent Application
20110226219
The present disclosure relates generally to high pressure fuel lubricated pumps for common rail fuel systems, and more specifically to a method of limiting nozzle outlet coking due to fuel degradation.
Nozzle coking, in the context of fuel injection systems for compression ignition engines, refers to the build up of solids in the nozzle outlets of fuel injectors. Nozzle outlet coking can reduce the flow area through a given nozzle orifice, and hence alter intended fuel quantities to be delivered to a given engine cylinder. In extreme cases, nozzle coking can completely block a nozzle outlet, further complicating engine fueling problems. While the issue of nozzle outlet coking is not new, the problems associated with potential nozzle coking have become more uncertain as the usage of non-petroleum based fuels, such as biofuel, have become more widespread. For instance, SAE Technical Paper Series 2007-01-0073 recognizes that the interaction of biofuel with certain metals, such as copper, can accelerate fuel degradation.
The present disclosure is directed toward one or more problems set forth above.
In one aspect, a method of operating a fuel system includes supplying biofuel to an inlet of a fuel lubricated pump. At least one bearing of the pump is lubricated with the biofuel. The biofuel is moved from the pump toward a fuel injector and then injected from nozzle orifices of the fuel injector. Nozzle orifice coking is limited at least in part by employing a spinodal bronze alloy in the pump bearing.
In another aspect, a fuel lubricated pump includes at least one movable component positioned in a pump housing that defines an inlet. The at least one movable component is supported by at least one bearing, which is positioned to contact fuel entering the fuel inlet. Chemical interaction between biofuel and the bearing is limited by employing a spinodal bronze alloy in the bearing.
In still another aspect, a fuel system includes a fuel lubricated pump with an inlet fluidly connected to a source of biofuel. The fuel lubricated pump includes at least one bearing in contact with biofuel moving through the pump. A common rail has an inlet fluidly connected to an outlet of the fuel lubricated pump. A plurality of fuel injectors are fluidly connected to respective outlets of the common rail. A spinodal bronze alloy is employed in the bearing of the pump as a means by which nozzle orifice coking can be limited.
Referring now to
Referring now to
For a variety of reasons, engineers have come to prefer the use of copper-based alloys in bearing components of fuel lubricated pumps of the type typified in
The present disclosure teaches limiting such fuel degradation due to a chemical interaction between fuel lubricated bearing(s) of pump 16 by employing spinodal bronze in bearing 47. By using a spinodal bronze alloy, the bearing retains most of the advantages associated with a copper based bearing in the fuel lubricated pump 16, but accomplishes its bearing task with limited chemical interaction between the copper of the alloy and the biofuel. This limited chemical interaction drastically reduces fuel degradation typically associated with the chemical interaction between biofuel and copper, rendering concerns with regard to nozzle coking with the use of biofuels less than the concerns would be if conventional fuel lubricated copper alloy bearing(s) were used in pump 16. Thus, the means by which chemical interaction between biofuel and the bearing is limited is accomplished by forming the bearing 47 out of a spinodal bronze alloy. For reasons not completely understood, the copper of the spinodal bronze alloy tends to be less reactive with biofuel than nonspinodal bronze alloys, which are also predominately copper like all bronze alloys. One specific spinodal bronze alloy composition includes nickel in the range of 14.5 to 15.5 percent, tin in the range of 7.5 to 8.5 percent, lead in amount less than 0.02 percent, with the balance of the composition being copper. The only current known source for this alloy is Brush Wellman Inc. which is headquartered in Cleveland, Ohio.
The present disclosure finds potential application in any metallic component that may come in contact with biofuel. The present disclosure finds specific application as an alternative to conventional copper alloys utilized in bearings for fuel lubricated pumps in common rail fuel systems. Potential problems associated with nozzle coking of nozzle outlet orifices of fuel injectors can be limited by the employment of spinodal bronze alloys in those components that may come in contact with biofuel somewhere in the fuel system. One specific place where this could occur is in one or more bearings of a fuel lubricated pump that supplies pressurized fuel to a common rail. For instance, the spinodal bronze alloy of the present disclosure may make a good replacement for traditional beryllium copper in fuel system applications. It may also be recommended in bearing applications where a high PV value is needed for sleeve bearing, which makes it a good choice for difficult sleeve bearing applications. The spinodal bronze alloy of the present disclosure is also noted for its corrosion resistance and excellent anti-gulling properties apart from its ability to limit nozzle coking that might otherwise occur utilizing traditional beryllium copper or other copper alloy bearing materials. In general, the spinodal bronze alloy of the present disclosure may not be the best selection for applications with continuous operating temperatures above 260° C.
It should be understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present disclosure in any way. Thus, those skilled in the art will appreciate that other aspects of the disclosure can be obtained from a study of the drawings, the disclosure and the appended claims.
