Mitigating exhaust emissions in CI engines using butanol-diesel-water microemulsions

The current research work examines the usability of surfactant-free microemulsion fuels as a substitute in CI engines, with alcohol being used as an amphi-solvent. Studies were carried out on different compositions of microemulsions with 35% volume and 40% volume butanol, named ME35 and ME40, having 57.8-64.4% volume diesel and 0.6-2.2% volume water. Most of the microemulsions had properties such as viscosity, specific gravity, cloud point, and sulfur content comparable to those of diesel. The heating values and cetane indices of the microemulsions were 0.09-8.7% and 19.4-28.7% lower than diesel due to the addition of water and alcohol. The water and sediments percentages were found to be low, even after the addition of water, indicating the microemulsions were stable. ME40 showed an average of 0.6-3.5% improvement in BTE, but the BSFC was also increased by 5.3-8.9%. The emissions of HC, NO_x, and PM showed an average decrease of 19.0-48.9%, 14.8-41.9%, and 10.06-50.24%, respectively, for all the microemulsions at all the loads. The CO emissions were lower at higher loads and vice versa, but the average CO emissions showed 5.16-31.9% decrease due to significant reductions at higher loads. It could, therefore, be concluded that microemulsions are a promising sustainable and cleaner substitute for diesel. Synopsis Microemulsion fuels successfully replaced up to 42% of diesel, with significant reduction in emissions of CO, HC, NO_x, and PM.