Improving the Performance of a Biogas Powered Dual Fuel Diesel Engine Using Emulsified Rice Bran Biodiesel as Pilot Fuel Through Adjustment of Compression Ratio and Injection Timing

Emulsification is one of the proven techniques to control the pollutants of the diesel engines. The present work attempts to explore the effect of injection timing (IT) of pilot fuel and compression ratio (CR) for an emulsified rice bran biodiesel (RBB)–biogas powered dual fuel diesel engine. A two-phase stable water emulsion of rice bran methyl ester has been prepared by optimizing the factors such as water content (5% and 10%), surfactants (3%), and hydrophilic lipophilic balance (HLB) values (4.3, 5, and 6). The stability of the emulsions is determined on the basis of measurement of mean droplet diameter and stability test. For experimentation, a 3.5 kW single cylinder, direct injection (DI), water cooled, variable CR diesel engine is converted into a biogas run dual fuel diesel engine by connecting a venturi gas mixer at the inlet manifold. A set of combinations comprising CRs of 18, 17.5, and 17, and ITs of 23 deg, 26 deg, 29 deg, and 32 deg before top dead centers (BTDC) at different loading conditions are considered. The investigation demonstrates a maximum brake thermal efficiency (BTE) of 23.62% along with a liquid fuel replacement of 82.22% at pilot fuel IT of 29 deg BTDC and CR of 18. For the same combination, CO and HC emissions are found to be least in all the test cases.