Durability Study of a High Pressure Common Rail Fuel Injection System Using Lubricity-Additized Gasoline-Like Fuel

Paper #:
  • 2018-01-0270

  • 2018-04-03
Based on preliminary experimental and modeling work, the use of gasoline-like fuels in compression ignition engines shows promise in simultaneously achieving high efficiency and low pollutant emissions. Proving that existing hardware systems are tolerant to these alternative fuels is a key step towards implementing a low cost, drop-in replacement for diesel in heavy duty applications. In this study, a 400 hour NATO test cycle was used to assess the overall robustness of a Cummins XPI common rail injection system operating with gasoline-like fuel. The cycle is designed to accelerate wear and identify any significant failure modes that could persist under normal operating conditions. Although prior work has investigated injection system durability with alternative fuels, this study uniquely focuses on a high volatility, low viscosity, gasoline-like fuel that has been additized to meet the current lubricity specification of market diesel. Fuel system parameters including rail pressure and fuel flow rates were continuously logged on a dedicated test bench in order to monitor hardware performance over time. Fuel and lubricant samples were acquired every 50 hours to assess possible fuel lubricity degradation, low level metallic wear, and dilution of the oil. Although test bench data indicated that 400 hours of testing were completed without any performance issues, it was not possible for the fuel system to meter very low injection quantities near the zero delivery point. Upon a teardown inspection, it was identified that the inlet check valve of the high pressure pump had experienced significant cavitation damage leading to degradation in sealing quality. Fuel analysis showed some changes in several elements that could be associated with dilution by oil. Lubricating oil samples did not show a strong trend of increasing dilution by fuel over time. An injection sweep comparison between gasoline and diesel clearly indicated that the low viscosity fuel exhibits significantly higher return flow rates and temperature. Increased return flows can lead to eventual thermal degradation of hardware, lacquer buildup within the system, and are also well correlated to higher fuel system parasitic losses. Further testing to 800 hours of operation and a complete teardown of the injectors is planned as future work.
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