Injection and Combustion of RME with Water Emulsions in a Diesel Engine
Keywords:diesel engine, RME – water emulsions, injection, combustion, visualization
AbstractThis paper presents ways of using the fully-digitised triggerable AVL VideoScope 513D video system for analysing the injection and combustion inside a diesel engine cylinder fuelled by RME with water emulsions.The research objects were: standard diesel fuel, rapeseed methyl ester (RME) and RME – water emulsions. With the aid of a helical flow reactor, stable emulsions with the water fraction up to 30 % weight were obtained, using an additive to prevent the water from separating out of the emulsion.An investigation was made of the effect of the emulsions on exhaust gas emissions (NOX, CO and HC), particulate matter emissions, smoke and the fuel consumption of a one-cylinder HD diesel engine with direct injection. Additionally, the maximum cylinder pressure rise was calculated from the indicator diagram. The test engine was operated at a constant speed of 1 600 rpm and 4 bar BMEP load conditions. The fuel injection and combustion processes were observed and analysed using endoscopes and a digital camera. The temperature distribution in the combustion chamber was analysed quantitatively using the two-colour method. The injection and combustion phenomena were described and compared.A way to reduce NOX formation in the combustion chamber of diesel engines by adding water in the combustion zone was presented. Evaporating water efficiently lowers the peak flame temperature and the temperature in the post-flame zone. For diesel engines, there is an exponential relationship between NOX emissions and peak combustion temperatures. The energy needed to vaporize the water results in lower peak temperatures of the combusted gases, with a consequent reduction in nitrogen oxide formation. The experimental results show up to 50 % NOX emission reduction with the use of 30% water in an RME emulsion, with unchanged engine performance.