11.3.5 Discussion
The BTE and BSFC were improved by up to 75% of the maximum load for all tested fuels because the brake power rate increased quickly compared to the fuel consumption rate and reduction in friction losses. At maximum load, BTE and BSFC showed a different pattern for all tested fuels due to the higher fuel consumption rate corresponding to the increased rate of brake power. Up to 75% engine load, the formation of CO emission did not vary much due to sufficient oxygen availability in the cylinder. However, CO emissions were initially slightly reduced with engine load due to better oxidation of hydrocarbons at higher cylinder temperatures. The maximum CO emission was obtained at full engine load conditions. An extra amount of fuel was injected at higher loads, making the mixture rich and supporting incom- plete combustion. Due to this, the abrupt increment of CO emission was observed at maximum load. The HC emissions for engine loadings up to 25% were found to be minimum due to ample oxygen and elevated cylinder temperature, leading to better oxidation of hydrocarbons. HC emissions have risen significantly with an increase in load above 25% due to a larger quantity of fuel injected, resulting in a lower air–fuel ratio (rich mixture) at higher loads. Oxygen insufficiency at higher loads contributed to incomplete combustion and thus hiked the concentration of HC emission. The NOx emissions concentration was found to be hiked with the rise in engine load, which was due to the larger amount of fuel pumped into the combustion chamber, with the rise in the load of the engine leading to an increased proportion of heat energy released and the temperature of the cylinder wall. The temperature rises of the combustion chamber at higher loads led to more NOx emissions.
The preheating of biodiesel and biodiesel blends reduced the viscosity and density, which might be improved the spray characteristics and atomization of fuel particles at a higher fuel inlet temperature. Due to this, better evaporation occurred, and a homogenous mixture was produced, which helped enhance the combustion reaction, resulting in better performance, better fuel combustion, and reduced emission except for NOx compared to non-unheated biodiesel blends. The addition of cerium oxide nanoparticles in the HB20 blend improved the efficiency and environmental perfor- mance, including the NOx, compared to HB20 due to the high catalytic behavior and the higher surface-to-volume ratio of CeO2 nanoparticles that promoted the better combustion of fuel, resulting in better engine performance. Moreover, the CeO2 nanoparticles’ specific capability of continuously absorbing and liberation oxygen acted as a three-way catalyst to simultaneously reduce CO, HC, and NOx emissions.
the present investigation provided a comparative analysis of six tested fuels and compared all biodiesel blends to the reference fuel (diesel). Compared to diesel, the BTE of B20, HB20, NHB20, B100, and HB100 decreased by 2.72–7.93%, 1.58–
4.15%, 0.69–3.07%, 5.99–11.56%, and 5.20–9.26%, respectively, while the BSFC increased by 1.81–14.73%, 0.67–9.26%, 0.22–6.74%, 14.44–21.82%, and 12.00–
19.39%. CO emissions for B20, HB20, NHB20, B100, and HB100 were found to be reduced by 1.76–12.17%, 5.02–14.78%, 10.57–19.13%, 8.24–22.60%, and 9.27–
30.43%, respectively, compared to diesel, whereas HC emissions of these fuels were reduced by 6.97%, 14.53%, 19.18%, 20.93%, and 26.74%, respectively at full load condition. NOx emissions were found to be raised by 1.62–2.69%, 3.55–24.34%, 2.95–19.47%, 4.44–25.73%, and 7.79–41.04% for B20, HB20, NHB20, B100, and HB100 over diesel at varying loads.
It may be possible that using the various types of biodiesel and nanoparticles could perform better than diesel fuel. Future research on life cycle analysis and techno- economic analysis would be beneficial in commercializing NHB20. A study based on durability analysis and non-regulated emissions is also advised to see the multi- faceted effects of NHB20 on diesel engines. The study to improve the storage ability of the nanoparticles added biodiesel blend should also be carried out to increase their feasibility in a diesel engine. Furthermore, SEM and TEM analysis research should be performed to learn more about nanoparticles’ structural and chemical characterization.
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