Performance of a rotary-blade real-time emulsification system on diesel vehicle exhaust emissions

The use of water-in-diesel emulsion fuel has been widely investigated as a strategy to mitigate harmful diesel exhaust emissions, particularly nitrogen oxides (NOx) and particulate-related smoke. However, practical implementation is often limited by emulsion instability, surfactant dependency, and storage-related challenges. This study aims to investigate the effects of surfactant-free, water-in-diesel emulsion fuel on harmful emissions from a common-rail diesel vehicle, using a rotary blade real-time emulsification system. Two fuels were employed: standard Euro 2 diesel and a 10% water-in-diesel emulsion prepared in real time by the rotary-blade system. Emission measurements were carried out at four idle engine speeds, namely 800, 1000, 1500, and 2000 revolutions per minute. Data was collected under steady-state conditions and compared against baseline diesel performance. The emissions measured during the tests included nitrogen oxides (NOx), carbon monoxide (CO), and smoke opacity. The results showed that the rotary-blade emulsification system consistently reduced nitrogen oxide emissions, with decreases ranging from 9.4% at low idle to nearly 40% at higher idle speeds. Smoke opacity was also significantly reduced at lower speeds, achieving reductions of more than 50%. However, at higher speeds, smoke benefits diminished and even reversed, showing an 8.9% increase at 2000 revolutions per minute. Carbon monoxide emissions, by contrast, increased across all operating conditions, with penalties as high as 50.6% at high idle. These results confirm that the rotary-blade system delivers the expected benefits of water-in-diesel combustion, such as improved atomization and lower flame temperatures, but also highlight the consistent drawback of incomplete carbon monoxide oxidation under cooler combustion conditions.