Performance analysis of HCCI engine powered by tamanu methyl ester with various inlet air temperature and exhaust gas recirculation ratios

[Display omitted] •Neat tamanu methyl ester was tested in both conventional CI and HCCI mode of operation.•TME powered HCCI engine exhibited lower NOx and smoke emission than TME powered CI engine.•Effect of various EGR ratios on HCCI combustion was investigated.•CO and HC emission evidently reduced by increasing the inlet air temperature with TME.•Challenges of HCCI engine was investigated.•HCCI knocking and misfiring could be controlled by adopting the elevated IAT and EGR ratio. 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 °C, 90 °C, and 100 °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 °C, so further experiments were carried out using the IAT 90 °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 °C leads to short HCCI combustion, tending to knock, thus leading to unstable operation.