Findings on droplet breakup behavior of the preheated microalgae oil jet for efficiency improvement in diesel engines

The ability to manage the liquid jet atomization and the breakup of droplets in diesel engines is becoming now one of the most important challenges of the unmodified CI engines’ operations. A mature comparative analysis is performed to achieve enhancement of the injection and liquid jet breakup characteristics of microalgae oil (MAO100) at an elevated temperature of up to 80 °C. To obtain reliable data, the following experimental tasks were performed and qualitatively described to identify the (i) distribution of Sauter mean diameter (SMD) d₃₂ of fuel droplets within the temporal evolution of a fuel jet, (ii) dynamics and topology dependencies of the liquid jet atomization and droplet breakup, (iii) dynamic formation of the liquid jet structure, and (iv) character and peculiarities of liquid jet breakup. The results of the research have shown the presence of zones distinguished by very intense droplet breakup, which carried out a robust individual character that does not depend on the type and temperature of the fuel. Furthermore, the preheated MAO100 was dominant (~ 70%) with droplets of the following size, d ≤ 40–50 μm (~ 20%) and d ≤ 120 μm (~ 50%), who were 1.2 to 1.5 smaller compared to those obtained at 20 °C. At t = 2 ms after injection of MAO100 (80 °C), the presence of droplets which radiuses exceed 500 μm was prevented. This tendency is ideally comparable to the one for a diesel fuel that, in turn, supports the hypothesis that the physical contribution to the ignition delay and hence to the entire process of combustion could be effectively controlled by the preheating route.