Diesel Microemulsion Fuel Resistant to Low-temperature Conditions: Study of Thermal Stability and Breakup

Abstract

The study was performed by using the alternative fuel prepared by the authorswater-in-diesel or ammonium acetate brinein-diesel microemulsions (WDME or BDME) stabilized by a non-ionic surfactant and various alcohols with a carbon chain length from C5 to C9 as co-surfactants. The study provides results on thermal stability of the fuel mentioned and a breakup of its drops during the impact onto a horizontal heated wall. The processes under study are crucial for developing advanced fuel technologies intended to reach conditions of the enhanced fuel vaporization, ignition, and combustion inside combustion chambers of various IC-engines and power generation systems. Learning of the thermal stability involves several ways for controlling temperature ranges of the prepared fuel existence. Among of them are a utilization of the ammonium acetate brines as a dispersed phase, as well as alcohols (hexanol-1, 2ethylhexanol, nonanol-1) as a co-surfactant when stabilizing microemulsions, a variation of the co-surfactant fraction in a surfactant/cosurfactant mixture (emulsifier), as well as the content of the dispersed phase relative to the continuous one. By using these ways we succeeded in fabricating the microemulsion fuel samples stable to phase separation in a temperature range from about-20°С to +60°С. For physical modeling of drop impingement of the fabricated fuels onto heated surfaces of a combustion chamber, we investigated hydrodynamic regimes of single drop interaction with a horizontal wall. In addition, regime maps were plotted, and the determining relationships between inertia, viscosity and surface tension forces were established. The study presents critical Weber and Reynolds numbers characterizing the thermal breakup/rebound transition. An application of the alternative fuels is of the great interest because it is possible to enhance considerably an explosive breakup of drops in combustion chambers due to low-boiling component vaporization. Such an effect enables a significant increase in fuel burnout and the reduction of environmentally harmful emissions.