The objective of this research work is to evaluate the performance, combustion, and exhaust emissions of a variable compression ratio diesel engine utilizing diesel 25% rubber seed biodiesel mixture (B25) blended with 25 ppm and 50 ppm of alumina nanoparticle running with different operating conditions. An ultrasonicator was used to make uniform dispersion of alumina (Al) nanoparticles in the diesel–biodiesel mixture. Biodiesel mixture blended with nanoparticles has physicochemical characteristics that are comparable to ASTM (American Society for Testing and Materials) D6751 limitations. The results revealed that the B25 exhibited a lower cylinder peak pressure and lower HRR (heat release rate) than diesel at maximum power. BTE (brake thermal efficiency) of B25 is 2.2% lower than diesel, whereas BSFC of B25 is increased by 6% in contrast to diesel. Emissions of HC (hydrocarbon), CO (carbon monoxide), and smoke for B25 were diminished, while emissions of NOx (nitrogen oxide) were higher at maximum power. Further, the combustion and performance of diesel engine were improved with the inclusion of alumina nanoparticles to biodiesel blends. In comparison to B25, BTE of B25 with 50% alumina nanoparticles (B25Al50) mixture was enhanced by 4.8%, and the BSFC was diminished by 8.5%, while HC, CO, and smoke were also diminished by 36%, 20%, and 44%, respectively. At peak load, the maximum cylinder pressure and HRR of B25 were improved by 4.2% and 6.7%, respectively, with the presence of 50% alumina nanoparticles in a biodiesel blend (B25Al50).

Biodiesel is one of the best alternative fuel to diesel engine among other sources due to having potential to reduce emissions. Biodiesel is a renewable, biodegradable and environment friendly fuel in nature. The advantages of biodiesel are lower exhaust gas emissions and its biodegradability and renewability compared with petroleumbased diesel fuel. The energy of the biodiesel can be released more efficiently with the concept of semi adiabatic (thermal barrier coated piston) engine. The objective of this study is to investigate the performance and emission characteristics of a single cylinder direct injection (DI) diesel engine using 25% biodiesel blend (Rubber seed oil methyl ester: RSME) as fuel with thermal barrier coated piston. Initially the piston crown was coated with Alumina (Al2O3) of thickness of 300 micron (0.3mm) by plasma coating method. The results revealed that the brake thermal efficiency (BTE) was increased by 4% and BSFC was decreased by 9% for B25 with coated piston compared to uncoated piston with diesel. The smoke, CO and HC emissions were also decreased for B25 blend with coated piston compared with the uncoated piton engine. The combustion characteristics such as peak pressure, maximum rate of pressure rise and heat release rate were increased and the ignition delay was decreased for B25 blend for the coated piston compared with diesel fuel.