A Multi-Stage Model for Scuffing of Reciprocating Components with Special Consideration of Fuel Injector Plungers

The majority of heavy trucks that populate the nation’s highways are powered by diesel engines. According to the latest available statistics,* there were 2.3 M registered combination trucks (those that pull trailers) and they consumed 26.5 B gallons of gas in 2002, averaging 5.2 miles per gallon of fuel. In addition, heavy single-unit trucks consumed 10.3 B gallons of fuel that same year and averaged a slightly-higher 7.4 miles per gallon. Motivated by fuel economy benefits and tighter emission regulations, the Department of Energy has invested in research to improve diesel engine technology, and some of those design improvements place increasing demands on the fuel system components. Friction, wear, and surface damage must be minimized to enable the fuel injectors to provide precisely metered quantities of fuel while smoothly sliding back and forth millions of times over their lifetime. Scuffing is a form of surface damage that can cause fuel injector parts to malfunction. Therefore it is important to understand the mechanisms of scuffing and how to utilize advanced materials and surface treatments to reduce or eliminate its deleterious effects. The model described in this report summarizes a multi-year effort that involved: development of new test methods to evaluate scuffing in reciprocating components, development of quantitative criteria to portray the initiation and propagation of scuffing damage, formulating a graphic method to enable scuffing to be displayed, and developing a model to explain scuffing behavior fundamentally and to serve as a guide for selecting more scuff-resistant materials. During the course of these studies, several open-literature publications were prepared, and these contain a more comprehensive description of the background research than does the present report which focuses mainly on the modeling aspects of the work. It is hoped that the approaches and insights provided here will enable further progress in engine materials technology . Authors: Blau, Peter Julian [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Metals and Ceramics Div.]; Qu, Jun [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Metals and Ceramics Div.]; Truhan, Jr., John J. [Univ. of Tennessee, Knoxville, TN (United States)]. DOE Contract: AC05-00OR22725. Subjects: 33 ADVANCED PROPULSION SYSTEMS; 42 ENGINEERING