Performance enhancement and emission reduction of CRDI diesel engine fueled using Manilkara Zapota biodiesel blend with TiO2 nanoadditive

The serious issues faced in recent years, globally, are the environmental pollution concern and fuel resource depletion. In this work, the effect of TiO2 nanoadditive in the optimized biodiesel blend of 15% fueled in a stationary single cylinder, 4-stroke naturally aspired CRDI diesel engine to assess the engine performance as well as the combustion and emission characteristics. The results of the prepared fuel samples are compared against using neat diesel fuel. Initially, a Soxhlet apparatus is used to extract the oil from the grounded Manilkara Zapota seed. Moreover, the oil derived from the Soxhlet method would be more viscous and a standard transesterification process is employed to reduce the viscosity. The M. Zapota biodiesel are characterized, and the analysis such as GC–MS (Gas chromatography – Mass spectrometry), FT-IR (Fourier transform Infra-red spectrum), NMR (Nuclear magnetic resonance) are performed. Similarly, the TiO2 nanoparticles are characterized based on surface morphology (FESEM, EDX, and XRD analysis). Three different concentrations of nanoparticles, namely 25, 50, and 75 ppm, are added to a 15% biodiesel blend in diesel fuel. The properties of the prepared fuel samples such as kinematic viscosity, calorific value, cloud point, flash point, cetane index are measured and compared with diesel fuel. The in-cylinder pressure developed during the combustion are lowered with increased TiO2 concentration and moreover, the neat heat release rate by the biodiesel blend using 50 ppm TiO2 nanoadditive is lowered to 29.9 J/oCA whereas, further addition increased the net heat release rate to 31 J/oCA which might be due to higher flame temperature during combustion. The HC emissions are lowered for S15 biodiesel blend with TiO2 NP's in the concentration of 50 ppm and moreover, the NOx formation from the engine for biodiesel blend with 50 and 75 ppm TiO2 nanoadditives are almost similar and significantly lowered. The formation of NOx using neat diesel, biodiesel, and biodiesel with 25, 50 and 75 ppm TiO2 nanoadditives in the engine are found as 600, 609, 556, 509 and 505 ppm, respectively. From the experimental analysis, it is found that the formation of NOx and CO emission reduces during the part load application of diesel engine with slight increase in CO and CO2 emissions and a reduction in cylinder peak pressure and net heat release. Manilkara Zapota seed oil biodiesel blend with diesel at 15% volume proportion along with 50 ppm TiO2 nanoadditive was proven to be a potential replacement for CRDI diesel engines with reduced HC and NOx emission with a slight compromise over the performance of engine.