The combined effect of hydrogen enrichment and exhaust gas recirculation on the combustion stability, performance and emissions of CI engine energized by algae biodiesel

Abstract

The scarcity of fossil fuels, the rising cost of liquid fuels, and the wide pollution footprint of conventional fuels all motivate scientists to seek out new approaches. This experimental study aims to explore the performance and emissions of compression ignition (CI) engines by introducing hydrogen into a biodiesel blend derived from algae. According to this study, the superior thermal properties of hydrogen associated with algal biodiesel have a significant impact on the performance and emissions of dual-fuel engines. The effect of hydrogen substitution rates of 10.4, 21.6, 32.4, 43.2, and 54 g per hour (g/h) on pure algae biodiesel was investigated. In comparison to diesel, the algae biodiesel reduces unburned hydrocarbons (UHC) and carbon monoxide (CO) emissions by 4.1% and 8.82%, respectively, while nitrogen oxide (NOx) emissions increase by 18%. Diesel was found to have increased brake thermal efficiency (BTE) and decreased brake specific energy consumption (BSEC) compared to biodiesel. With the addition of pure biodiesel, the 43.2 g/h H2 substitution rate produces a maximum thermal efficiency of 1.92% and a 9.5% decrease in brake-specific energy consumption compared to diesel at maximum load. Compared to diesel, the emission attributes of UHC, CO, and smoke opacity decreased by about 45%, 48%, and 41%, respectively. However, NOx emissions increase by about 36% compared to diesel due to the higher flame temperature and carbon-free fuel of hydrogen and oxygenated biodiesel. The induction of 15% exhaust gas with B100 + 43.2 g/h H2 reduces NOx by about 31% in comparison to B100 + 43.2 g/h H2 without exhaust gas recirculation (EGR). This is primarily attributable to the high oxygen dilution and specific heat capacity of burned gases, which result in a decrease in peak cycle temperature. Compared to diesel, B100 + 43.2 g/h H2 increased the cylinder pressure and heat release rate by about 1.86 and 4.29%, respectively. As a result of its high energy density, hydrogen improves overall energy utilization and engine performance. Hydrogen's rapid flame speed and wide flammability range contribute to the efficient and complete combustion of the algae fueling the CI engine. As well as showing outstanding performance, dual fuel CI engines have the potential to significantly contribute to lowering emissions. Finally, it was determined that using algae biodiesel and exhaust gas recirculation with hydrogen substitution in diesel engines can significantly reduce emissions while increasing efficiency.