Application of an Inline Mixer to Produce Surfactant-Free Biodiesel-diesel/Water Emulsion Fuel: An Analysis of Water Droplets Characteristics and Drive Cycle Emissions

Water-in-diesel (W/D) emulsion is a promising alternative fuel candidate, as it can simultaneously reduce nitrogen oxides (NOx) and particulate matter (PM) while improving engine performance. Wide scale adoption of this fuel is difficult due to high production and storage costs. Hence, Real-Time Non-Surfactant Emulsion Fuel Supply System (RTES) is a proposed technology to solve these issues by mixing diesel and water in-line directly to the engine. This study presents an updated RTES prototype which incorporated a modular design, with a feedback system to control water injection rate. In this paper, RTES was installed to a common rail injection diesel-powered vehicle and the biodiesel-diesel W/D produced by RTES was analyzed to determine the effect of common rail pressure toward water droplet size and distribution. The vehicle was then tested under the New European Driving Cycle (NEDC) to evaluate vehicle emissions, which will serve as the basis for evaluating the emissions profile of W/D produced by RTES under urban and extra-urban driving conditions. It was found that when subjected to high common rail pressures, W/D droplets produced by RTES reduced by 21.1% compared to freshly produced W/D. NEDC emissions data revealed that NOx emission was reduced to a maximum of 25.3% in urban driving conditions. Hydrocarbons and carbon monoxide increased marginally throughout urban driving phase; while, carbon dioxide emissions were comparable between biodiesel-diesel and W/D. However, extra-urban driving conditions were unfavorable for RTES activation, as substantial emission increases were observed during high-speed accelerations. Nonetheless, W/D reduced PM emissions by 51% throughout NEDC.