Wear with low-lubricity fuels II. Correlation between wear maps and pump components

Increasingly severe refinery processes remove many of the compounds necessary for effective lubrication with diesel fuels. No widely recognized lubricity test or standard currently exists relating to the needs of the fuel injection system on compression ignition equipment. The Ball-on-Cylinder Lubricity Evaluator (BOCLE) is commonly used by the US Air Force to measure aviation turbine fuel lubricity. However, the tribological requirements of fuel-lubricated components in aviation may not coincide with the needs of ground vehicles. This study uses the wear-mapping technique developed in the preceding paper (“Development of a wear mapping technique”) to indicate the significance of the BOCLE test methodology in this context. In particular, the work highlights the effects of various contact parameters on fuel-lubricated wear that are not revealed by the BOCLE results.

Where possible, both the BOCLE and wear map data are compared with the results of full-scale pump stand tests detailed in the previous paper. Additional nonstandard bench wear tests were performed to further evaluate the contact conditions present within the operating pump. The wear mechanisms of each fluid were determined to be strong functions of both metallurgy and contact stress. Moreover, the onset and severity of each wear mechanism appear to be controlled by different fuel properties. As a result, the relative lubricity observed between fuels depends on the test conditions chosen so it is unlikely that fuel lubricity may be uniquely defined by a single bench wear test procedure.