Experimental Studies on Methanol Sprays for IC Engine Applications

Abstract

In this work, studies have been conducted on sprays of methanol and its emulsions with diesel towards assessing the potential of methanol as an alternative fuel for IC engines. Methanol can be used in compression ignition engines as a methanol-in-diesel emulsion, and in spark ignition engines as a direct gasoline-substitute. Evaporating spray characteristics of methanol-in-diesel emulsions and pure methanol are studied in a high-pressure chamber with optical access. In the first part of the study, a comparison between two measurement methods (DBI and scattering) along with two post-processing methods (line-fit and threshold) to measure liquid length of a diesel spray is presented. The second part of the study involved assessing the stability of methanol-in-diesel emulsions with conventional surfactants such as sorbitan monooleate (Span-80®) and polyoxyethylene sorbitan monooleate (Tween-80®). The hydrophilic-lipophilic balance (HLB) values of the surfactant were varied from 7 to 15 to investigate the role of the surfactant on stability of the macroemulsion. It was observed that macroemulsions with up to 10 wt.% of methanol were stable. The macroemulsion with an HLB value of 10 gave the best stability results. In the third part of the study, the emulsion sprays were characterized in a constant volume chamber at injection pressures of 500 bar, 1000 bar, and 1500 bar in an inert atmosphere of nitrogen at 50-bar and 900-K. Interestingly, the liquid-length of the methanol-in-diesel emulsion spray with 10 wt.% of methanol using a mixture of Span-80® and Tween-80® as a surfactant is higher by around 25% as compared to that of the diesel spray, even though methanol is far more volatile than the components of diesel. This is attributed to the higher boiling point of the surfactant used, as confirmed by experiments with a low boiling point surfactant, i.e., 1-dodecanol, and recent observations from the literature. Next, microemulsions of diesel-methanol were produced by using various surfactants such as 1-dodecanol...