Study of combustion and emission characteristics of diesel fuel/water emulsion (2st report, Effects of hydrogen addition on spray combustion)

This study experimentally investigated combustion and emission characteristics with hydrogen added to both diesel fuel spray and emulsion fuel spray. The water percentage of 5 vol% in W/O emulsion fuel was used. For experimental setup, a burner equipped with a twin fluid atomizer was used. Hydrogen was supplied near the flame base. Results show that the height and luminosity of flame increased with hydrogen fraction for both spray combustion of diesel fuel and emulsion fuel. The amounts of CO and THC emissions decreased by increasing hydrogen fractions with both fuels. However, flame luminosity with emulsion fuel was lower than that with diesel fuel alone even if hydrogen was added. The lower flame luminosity is caused by smaller amount of soot with emulsion fuel due to water gas shift reaction and by lower combustion temperature. The combustion temperature was decreased by increased sensible heat and latent heat by the presence of water in emulsion fuel. Also, the lower temperature decreased the amount of NO emissions in comparison with the case with diesel fuel alone.