Wear Mechanism Evaluation and Measurement in Fuel-Lubricated Components

Abstract : Previous studies have demonstrated that the durability of some fuel injection systems on compression-ignition engines will be adversely affected by fuels of sufficiently low lubricity. However, no widely accepted lubricity measure is available; indeed, the wear mechanisms present have not been conclusively defined. The results of the present study indicate that oxidative corrosion is the predominant mechanism with very highly processed fuels, resulting in catastrophic wear and rapid failure. A laboratory test procedure directed toward the oxidative wear mechanism was evaluated and a number of modifications suggested. Two closely related laboratory wear test procedures that rely on the transition from mild boundary lubricated wear to adhesive scuffing were also developed. The resulting procedures allow the fuels to be either ranked using a continuous scale or separated using a simple pass/fail criteria. All the procedures are sensitive to the addition of trace quantities of lubricity additives and show directional correlation with refinery severity, as measured by sulfur and aromatic content. As a result, the tests produced excellent correlation with full-scale equipment tests performed at a number of locations, as well as the criteria necessary for oxidative corrosion. However, the scuffing load tests show greatly increased separation between good and unacceptable fluids compared to the oxidative corrosion tests. Evaluation of commercially available fuels indicates that fuel lubricity is decreasing and that very poor lubricity fuels are occasionally observed. Humidity, Boundary lubrication, Corrosive wear, Bench test, Diesel, Viscosity, Corrosion inhibitor, Oxidative wear, Adhesive wear.