Spray and Combustion Characteristics of CTL-Diesel Fuel Blends in a Constant-Volume Combustion Chamber

Coal-to-liquid (CTL) fuel is considered a promising alternative fuel for diesel engine applications in China owing to its excellent fuel properties. However, little research on the spray and combustion processes of CTL fuel has been scarce. Therefore, in this study, the spray and combustion characteristics of diesel fuel blends with different CTL fuel blending ratios were investigated in a constant-volume combustion chamber. The results show that under non-evaporation conditions (300 K), a longer spray tip penetration (STP) and enlarged spray cone angle (SCA) were obtained with a higher injection pressure owing to the enhanced turbulent interaction. The SCA of CTL fuel blending was larger than that of diesel fuel owing to its lower viscosity and slightly shorter STP. Under the evaporation condition (700 K), with an increase in the CTL mixing ratio, both the STP and SCA of the fuel exhibited a decreasing trend owing to the higher volatility. Meanwhile, as the CTL mixing ratio increased, the ignition delay period was shortened, and the flame lift-off length decreased, whereas both the integrated natural flame luminosity and combustion duration increased. The cetane number of CTL fuel plays an important role in the occurrence of these results.