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

Experimental data and modeling work have shown that gasoline-like fuels can potentially be used to simultaneously achieve high efficiency and low pollutant emissions in compression ignition engines. Demonstrating that existing hardware systems are tolerant to these fuels is a key step in harnessing this potential. In this study, a 400-hour North Atlantic Treaty Organization (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 was designed to accelerate wear and identify any significant failure modes that could appear under normal operating conditions. Although prior work has investigated injection system durability with a wide variety of alternative fuels, this study uniquely focuses on a high-volatility, low-viscosity, gasoline-like fuel that has been dosed with lubricity additive. Fuel system parameters including pressures, temperatures, 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 fuel consistency, low-level metallic wear, and dilution of the oil. Test bench data indicated that 400 hours of runtime were completed without serious degradation of the components. However, a performance check conducted at the conclusion of the test revealed that it was not possible for the fuel system to meter very low injection quantities near the zero delivery point and control rail pressure within specifications. Upon a hardware teardown inspection, it was identified that the inlet check valve (ICV) of the high-pressure pump had experienced significant cavitation damage which led to a degradation of sealing quality. Fuel analysis showed some changes in several elements that are likely associated with material wear and dilution by oil, although oil samples did not show a strong trend of increasing dilution by fuel over time. An injection quantity sweep comparison between gasoline and diesel clearly indicated that the lower viscosity fuel exhibited significantly higher fuel return rates and temperatures.