Impacts of additives on performance and emission characteristics of diesel engines during steady state operation

Depletion of fossil fuel resources and stringent emission mandates has spurred the search for improved diesel engines performance and cleaner combustion. One of the best approaches to solve these issues is to use biodiesel/diesel additives. The effects of biodiesel/diesel additives on the performance and emissions of diesel engines were comprehensively reviewed throughout this article. The additives reviewed herein were classified into five categories, i.e., oxygenated additives, metallic and non-metallic based additives, water, antioxidants, and polymeric-based additives. The effects of each category on the engine performance (i.e., brake specific fuel consumption (bsfc) and brake thermal efficiency (bte)) and emissions (i.e., CO, NOx, HC, and PM) were exclusively summarized and discussed. Furthermore, various strategies used for adding water like water-diesel emulsion, direct water injection, and adding water into the inlet manifold were illustrated and their pros and cons were completely scrutinized. Finally, opportunities and limitations of each additive considering both engine performance and combustion benignity were outlined to guide future research and development in the domain.