Effect of Long Storage Stability of Karanja (Pongamia) Derived Biodiesel Fuel on the Performance, Combustion and Emission Characteristics of a Multi-Cylinder Turbo-Charged Direct Injection Diesel Engine

Due to its renewable nature, emission advantage and easy adaptation, biodiesel is emerging as an alternative to fossil diesel. There are however concerns on biodiesel storage stability aspect due to the presence of unsaturated content in its composition. This paper discusses on studying the effect of long term storage stability of Karanja derived biodiesel (KME) on the performance, combustion and emission characteristics of a turbo-charged, multicylinder, direct injection diesel engine. For aged karanja derived biodiesel (A-KME) stored in a mild steel container for 500 days, both the fuel properties and the engine performance are found to change. It is observed that the aged fuel as compared to the fresh karanja derived biodiesel (F-KME) showed i) an increase in the acid value and kinematic viscosity from 0.374 mg KOH/g to 0.89 mg KOH/g and 5.6 to 5.7 cSt respectively, ii) a slight decrease in ignition delay and maximum rate of pressure rise, iii) a maximum increase in peak cylinder pressure of about 10% and duration of combustion of 8 deg. CA, iv) a decrease in brake thermal efficiency to an extent of over 4%, v) an increase in un burnt hydrocarbon emissions particularly at low loads, and, vi) a significant increase in exhaust nitric oxide (∼30%) and the smoke emissions (∼78%) at higher loads.