Effect of fuel temperature on heavy fuel oil spray characteristics in a common-rail fuel injection system for marine engines

• Physical properties of HFO are measured as a function of fuel temperature.
• Effect of fuel temperature on injection rates were analyzed.
• Spray development processes were visualized for various fuel temperature.

The present study was conducted to investigate the effects of fuel properties on the spray characteristics of a common-rail type marine diesel injector. Spray characteristics are highly influential in determining engine performance and emission characteristics in direct-injection engine systems containing marine diesel engines. Thus, the relationship between the physical properties of HFO fuel and its spray characteristics is investigated via an analysis of HFO and spray experiments. Data from physical property measurements (e.g., fuel density, dynamic viscosity, and surface tension) are used to derive empirical equations between fuel temperatures and physical properties, and the results follow the common tendencies of temperature–property curves for general liquid substances. In spray experiments, injection quantity measurements, injection rate profiles, and spray visualization were conducted under various injection pressures, energizing durations, and ambient pressures. The test temperatures of HFO were set from the results of physical property measurements.Experimental data reveal that spray characteristics are affected by fuel properties in terms of injection delays, injection profiles, and spray development speed. The injection quantity increased proportionally with fuel densities and the onset of injection was delayed with increased dynamic viscosity. Spray tip penetration decreased with increased fuel temperature.