Experimental investigations of comparative performance, emission and combustion characteristics of a cottonseed biodiesel-fueled four-stroke locomotive diesel engine

A large-bore, four-stroke, medium-speed, compression-ignition railway traction locomotive engine was fueled with cottonseed methyl ester (Biodiesel). The cottonseed methyl ester was stored for 6 months under ordinary storage conditions, and various fuel properties of this seasoned cottonseed methyl ester were evaluated. Various blends of cottonseed methyl ester (B10, B20, B50 and cottonseed methyl ester) were evaluated for engine performance, emissions and combustion characteristics of the locomotive engine compared to baseline diesel. Correlation of the fuel-injection performance parameters with the physical properties of biodiesel has been carried out. The engine was able to operate on cottonseed methyl ester without noticeable power loss. With cottonseed methyl ester, the thermal efficiency decreased marginally by 0.7% and the brake-specific energy consumption increased by 0.1 MJ/kWh at the rated power. Due to the lower calorific value of biodiesel, brake specific fuel consumption (BSFC) increased by 13.4% at eighth engine notch, nitrogen oxide emissions increased by 8% and particulate matter emissions decreased by 32% vis-a-vis mineral diesel. Nitrogen oxide emissions were found to be a function of injection timings, global oxygen/carbon ratios, time of the maximum mean in-cylinder temperatures and apparent heat release. Particulate matter emissions were found to depend on the air-fuel mixture's oxygen/carbon ratio, fuel bound oxygen and fuel-injection pressure. The experiments were carried out to evaluate the in-cylinder pressure, heat-release rate, cumulative heat release, fuel-injection pressure, needle lift and fuel-injection velocities. Increased fuel-injection pressures (1000 bar compared to 900 bar for mineral diesel), advanced fuel-injection timings, shorter combustion duration, advanced in-cylinder pressures and higher heat-release rates were observed for biodiesel and blends. The findings of the present study have provided further insights into the combustion of biodiesel in locomotive engines.