A landscape review on biodiesel combustion strategies to reduce emission

The study presents state-of-the-art literature on biodiesel combustion strategies for improving engine performance and reducing emissions. The application of those strategies in compression ignition engines is a prominent approach to reducing harmful emissions. The literature reveals that biodiesel can significantly reduce CO, HC, and PM emissions. However, the higher NOx emission characteristics of biodiesel compared to fossil fuel is a concerning factor for its application. In addition, its physicochemical properties have also shown some complications during the combustion process. This article covers fundamental aspects, challenges, prospects, and the pros and cons of advanced biodiesel combustion strategies such as low-temperature combustion (LTC), chamber modifications, and injection modifications that directly influence combustion rate and emission formation. In addition, the exhaust gas after-treatment systems and the effect of operating parameters are briefly discussed and presented in this article. The study found that LTC strategies and retarded injection timing showed significant reductions in NOx emission in the leaner mixtures but with poor combustion control. Besides, chamber modifications and higher injection pressure showed better combustion through high turbulence and swirl rates, but leading to more NOx emission. The review critically analyzed those strategies and concluded that incorporating leaner mixture combustion with chamber modifications will form better combustion under low in-cylinder temperature conditions, favoring reducing the NOx emission. Finally, the study recommends that more studies are needed to obtain a low in-cylinder temperature atmosphere by altering the equivalence ratio and optimizing the chamber (geometry and nozzle) modifications and varying injection parameters with biodiesel to reduce emissions.