Filtration Technology Challenges for Common-Rail Diesel Engine Fuel Systems

The focus of this study was to determine the role of liquid filtration in controlling debris in fuel and maintaining common-rail fuel system life for off-highway diesel engine applications. Three key areas of filtration design surfaced as most important areas of focus – basic filtration efficiency, robustness of filter manufacturing, and filter assembly cleanliness from production (before and during installation into fuel system). The study also revealed the importance of designing fuel filtration systems consisting of primary filtration (suction-side water separation and particulate filtration) combined with pressure-side particulate filtration. The performance characteristics of the filtration system as a whole were found to be extremely critical in optimum fuel system performance and life goals, especially in severe-duty applications.

The study analyzed two filter systems – the Control System that consisted of pre-common-rail technology and the Proposed System that included all of the improvements designed to adequately protect the fuel system. The Control System consisted of B_20(c) = 75 primary filtration and B_8(c) = 75 secondary filtration. The results of the study recommended the Proposed System consist of B_10(c) = 75 primary filtration and B_4(c) = 200 secondary filtration. This system improved fuel system life by 20× in normal applications and nearly 10× in heavy-duty applications.

Several test methods were used to generate data including the multipass test (ISO 4548-12), fabrication integrity (ISO 2942) test, and specially developed production cleanliness and fuel system simulation tests. The study examined the adequacy of existing filtration technology in protecting common-rail fuel systems (benchmarking) and determined acceptable design requirements in the previously mentioned areas for individual fuel filters (pressure-side filtration) and filter systems (combining suction-side and pressure-side filtration).