Title : Green Fuel, Green Earth
Abstract:
This presentation investigates the production, characterization, engine performance, emission behaviour, and energy–exergy analysis of biodiesel derived from non-edible feedstocks such as tomato seed oil, apricot, and papaya oils. With the growing global emphasis on sustainable fuels, these sources offer renewable, low-emission alternatives to conventional diesel. The biodiesel was synthesized via a base-catalysed transesterification process using NaOH and methanol. Precautions were taken to avoid soap formation, including the use of dry methanol and control of free fatty acids. The resulting products—fatty acid methyl esters (FAMEs) and crude glycerol—were separated, washed, and refined. Chromatographic analysis revealed the biodiesel contained over 90% methyl esters, including C16:0, C18:0, C18:1, C18:2, and C22:2 fatty acids.
Engine performance tests were conducted on a four-cylinder Kubota V3300 diesel engine using various biodiesel blends (B5, B10, B20) and pure diesel (B0). The B10 blend demonstrated superior results with the lowest CO and CO? emissions, attributed to better combustion due to higher oxygen content. B5 showed the lowest HC emissions, while B0 exhibited the least NOx emissions. The spherical combustion chamber design facilitated enhanced air-fuel mixing, improving thermal efficiency and reducing emissions. Computational simulations were also conducted using AVL FIRE, a 3D CFD engine simulation software. These simulations modelled the intake, combustion, and emissions characteristics of the engine, and the results aligned well with empirical findings, validating the accuracy of the model. In addition, a neural network was developed using real experimental data to predict performance and emissions. It featured ten hidden layers and used early stopping to avoid overfitting, achieving high prediction accuracy based on MSE and R² values.
A detailed energy and exergy analysis was conducted to evaluate the thermodynamic performance of the biodiesel blends. At the engine speeds corresponding to maximum torque and power, the average energy efficiency was approximately 29.27%, while the exergy efficiency was slightly lower at 26.90%. This indicates that about one-third of the total input energy was converted to useful power, but only about one-fourth of the available exergy contributed to work, highlighting the irreversibilities present in the combustion process. Furthermore, the exergy destruction was found to be higher for conventional diesel due to less complete combustion and higher entropy generation. Thermodynamic complexity analysis showed that blends with lower entropy, such as TD and TAD, produced higher torque and lower exhaust temperatures, confirming the efficiency benefits of biodiesel combustion. This contrasts with higher-complexity fuels like pure diesel, which exhibited incomplete combustion and higher emission temperatures.
In conclusion, biodiesel derived from tomato, apricot, and papaya oils not only complies with ASTM standards but also improves engine performance, reduces emissions, and demonstrates better thermodynamic efficiency through both energy and exergy perspectives. These findings support the integration of such biodiesels into current diesel engines as part of a sustainable energy transition.
