Effects of Waste Vegetable Oil/Water Emulsions on the Emissions of a Listeroid Diesel Engine

This study presents the experimentally determined effects of filtered, heated, waste vegetable oil (WVO) and water emulsions on gaseous emissions, opacity, and fuel efficiency of a Listeroid diesel engine. Emissions studied are NO_x, CO, CO₂, SO₂, O₂, unburned hydrocarbons (UHCs), and opacity. WVO emulsions with water additions of 0%, 10%, 20%, 30%, and 40% by weight, heated to 95°C at injection are studied, and results are compared to diesel. The water addition limit was found to be between 41–49%, inclusive, at 50% load. Emulsions are maintained with a magnetic stirrer prior to entry into the fuel line. The WVO is preheated using heat from the exhaust gases. This reduces its viscosity prior to entering the fuel pump, reducing engine wear, pumping losses, and fuel starvation. The WVO is heated again to 95°C immediately before injection, using an externally powered heater to standardize test conditions. A new metric is introduced, namely, brake specific global warming potential (BSGWP). There is a significant reduction in BSGWP at 50% engine load and 30% water addition. Emissions from 40% water addition most closely resemble diesel engine emissions at all engine loads and are consistently lower than with pure WVO.