Effect of Diesel on the Performance of Microemulsion Fuels

The increased consumption and limited reserves of diesel, along with its contribution to emissions of particulate matter and nitrogen oxides, has led to an interest in the diesel alternatives, such as biodiesel, hydrotreated vegetable oils, emulsions, and microemulsions. Microemulsions are thermodynamically stable and optically isotropic dispersions of oil and water, stabilized by layers of surfactant and/or co-surfactant. They do not involve any reactions during preparation, and can be used directly in the engine without any modifications. The current work examines the usability of diesel-based microemulsions as an alternative fuel for the compression-ignition engines. Different compositions of microemulsions were formulated with 35 and 40 %(v/v) alcohol, 57.8 ‒ 64.4 %(v/v) diesel, and 0.6 ‒ 2.2 %(v/v) water, and their properties tested as per ASTM D975. Most of the microemulsion compositions satisfied the ASTM standards, and therefore were further tested in a diesel engine to evaluate the performance and emissions parameters. The engine studies were carried out with microemulsions having constant alcohol percentages, and varying diesel percentages. It was observed that almost all the microemulsions had slightly higher fuel consumption, due to a reduction in calorific value. However, the thermal efficiencies were slightly improved due to the presence of alcohol and water, leading to a more complete combustion of the fuel. The CO emissions were found to be higher at lower loads, and lower at higher loads, when compared to those of the neat diesel. The emissions of CO₂, unburnt HC, and of NO_x were lower throughout all the loads for most of the microemulsions. These microemulsions were also found to be economical as compared to petro-diesel in the present Indian scenario. The microemulsions could successfully replace almost 40% of diesel, with lesser emissions, and without any additional modifications in the engine, and thus are a promising cleaner alternative to diesel.