Feasibility Study on the Utilization of Water-in-Oil Type Emulsified Fuels to Small DI Diesel Engines

This study deals with the thermal efficiency improvement of diesel engines operated by W/O (water-in-oil) type emulsified fuels. This paper focuses on the feasibility of W/O emulsions as fuels applied to small diesel engines from the view point of compatibility between lower fuel consumption and lower NO_x emission. Effects of water content ratio and mean diameter of water scattered in gas oil on ignition, combustion and emission characteristics in a small DI diesel engine with progress of fuel injection timing were experimentally investigated. Results showed that water content ratio strongly influenced on ignition delay and associated combustion characteristics after auto-ignition, and mean diameter of dispersed water in gas oil was not sensitive parameter on ignition and combustion. Under the 60% load condition in 2000 rpm engine operating speed, for 20 volume percent water content W/O emulsified fuel, slight progress of fuel injection timing yielded approximately 5% improvement of thermal efficiency and 60% reduction of NO_x emission compared with the base engine performance fueled by gas oil.