Increasing attention has being paid to alternative fuels that have the potential to reduce overall greenhouse gas emissions and fossil fuel dependence. The alcohol fuel n-butanol, as one of the advanced biofuels, can be potentially utilized as a partial or complete substitute for the diesel fuel in diesel engines. Experimental results from literature, as well as from the authors’ previous research, have shown promising trend of low soot and nitrogen oxides emissions from the combustion with n-butanol high pressure direct injection. However, due to the significant fuel property differences between n-butanol and diesel, the fuel delivery mechanism and combustion control algorithm need to be optimized for n-butanol use. A better understanding of the high pressure n-butanol injection characteristics, such as the injector opening/closing delays and spray droplet sizes, can provide the guidance for the control optimization and insights to the empirical observations of engine combustion and emissions. Meanwhile, the experimental data could be used for the model development of the n-butanol high pressure fuel injection events.
In this work, injection rate measurement, high-speed video direct imaging, and phase Doppler anemometry (PDA) analysis of neat n-butanol and diesel fuel have been conducted with a light-duty high pressure common-rail fuel injection system. The injection rate measurement was performed with an offline injection rate analyzer at 20 bar backpressure to obtain the key parameters of the injector opening/closing delays, and the instantaneous pressure rise. The spray direct imaging was carried out in a pressurized chamber, and the PDA measurement was conducted on a test bench at ambient temperature and pressure. The injector dynamics and spray behavior with respect to the different fuels, variation of injection pressures, and variation of injection durations are discussed.