Abstract
The extensive usage of petroleum as a fuel in a conventional engine produces harmful pollutants and also leads to global warming. CI engines have certain advantages over SI engines such that they have higher efficiency and emit lesser CO and HC, but they also have disadvantages such as high smoke and NOx. A homogeneous charge compression ignition engine (HCCI) is a better solution to minimize smoke and NOx simultaneously. The present study was performed comparing the conventional CI engine and HCCI mode of operation fueled with tamanu methyl ester (TME). The HCCI engine was run at various inlet air temperatures (IAT) (80 degrees C, 90 degrees C, and 100 degrees C) because tamanu methyl ester cannot be vaporized at room temperature. The results exhibited that TME operated CI engine noticed higher brake thermal efficiency (BTE) and fuel economy and also lesser carbon monoxide (CO) and unburned hydrocarbon (UBHC) emission than the HCCI engine. HCCI engine with enhanced IAT showed lower NOx and smoke emission than conventional engine. From the results, the optimum IAT was found to be 90 degrees C, so further experiments were carried out using the IAT 90 degrees C at various exhaust gas recirculation (EGR) ratios. The EGR associated HCCI engine produces ultra-lean NOx emission, but on the other hand, it shows slightly lower BTE, cylinder pressure and heat release rate than the engine operating without EGR. The results also exhibited that elevation of IAT beyond 100 degrees C leads to short HCCI combustion, tending to knock, thus leading to unstable operation.