Use of Biodiesel and Bio-oil Emulsions as an Alternative Fuel for Direct Injection Diesel Engine

Biofuels are considered as the most attractive and alternative energy sources for the heat and power applications in the near future. Biodiesel, derived from various vegetable oils, has poor oxidation stability and cold flow properties, despite its merits over petroleum diesel. On the other hand, bio-oil obtained from woody biomass through pyrolysis has many hindered phenols, which is a merit and may solve this problem, even though the bio-oil has low calorific value and high viscosity. In this investigation, an attempt has been made to study the effect of combustion, performance and emission characteristics of a direct injection diesel engine fueled with biodiesel and bio-oil emulsions. Emulsions made from wood pyrolysis oil (WPO) and methyl ester of jatropha (JME) were used as the alternative fuels in a single cylinder, four stroke, air cooled diesel engine developing a power of 4.4 kW at 1,500 rpm. Three emulsions by taking 5, 10 and 15 % of WPO on a volume basis were emulsified with 95, 90 and 85 % of JME, denoted as JOE5, JOE10 and JOE15 respectively. The experimental results showed an increased thermal efficiency, and reduced HC and CO emissions, with the JME-WPO emulsions. The NO emissions for the JME-WPO emulsions were found to be higher than those of diesel operation, but reduced with the addition of WPO in JME. The smoke emissions showed a declining trend compared to that of diesel operation in the same engine. JME-WPO emulsions exhibited shorter ignition delay than that of diesel operation at full load. The values of peak pressure are higher by 9.8, 7.9 and 8.8 % than those of diesel operation at full load for JOE5, JOE10 and JOE15 respectively.