Recent progress on mixing technology for water-emulsion fuel: A review

Global problems such as energy crisis and air pollution issues have motivated researchers to conduct research on water-diesel fuel emulsion as a strategic research works. Researchers agree that water emulsion could reduce emissions of NOx and particulate matters (PM) simultaneously. This paper discusses the parameters that affect the properties and stability of the emulsion, as well as the latest technology in the mixing process of water diesel fuel emulsion. Numerous research activities on different parameters that affect the properties and stability of emulsion have been carried out by many researchers, including the effect of mixing time, temperature, mixing speed, surfactant percentage, and water ratio. In addition to these parameter factors, the mixing technology also play crucial position on the characteristics of the emulsion produced. The size of a water droplet was the character of an emulsion that was strongly influenced by the mixing technology. There were various methods in the mixing process of water emulsion fuels such as ultrasonic vibration, a mechanical homogeniser, mechanical agitators, real-time non-surfactant emulsion fuel system (RTES), rotary high-speed blending machines, stirred high speed, high shear mixers or a combination of several of these methods. In the mixing process, many researchers still use a surfactant as an emulsifier. However, in recent years, surfactants are being minimized and the mixing process has been optimised. In the future, research on emulsion fuel still has excellent prospects, including structured design of experiments, economic studies, engine components, supporting policies for emulsion fuel, and advanced mixing technologies.