Combustion chamber modifications to improve diesel engine performance and reduce emissions: A review

The concept of combustion chamber modifications of diesel engines has been attracting much attention in the field of engine research. Many researchers are investigating modified combustion chambers in modern engines because several studies revealed encouraging results: improved brake thermal efficiency (BTE), and reduced brake specific fuel consumption (BSFC), hydrocarbon (HC), carbon monoxides (CO), soot and smoke emissions. However, further investigation is needed into chamber modification vis-a-vis the creation of ordered turbulence, which can help to control nitrogen oxides (NOx) emissions; besides, the rapid turbulence formations on piston crowns lead to impotent tendencies like knocking, system failure and unregulated emissions. A survey of recent studies in the literature has revealed that these chamber modifications can impact positively on air-fuel mixture rates, fluid distribution, heat transfer rates and emission formations. The primary focus of this study is to evaluate engine combustion characteristics,performance and emissions due to chamber modifications by investigating their effect on different chamber profiles and fuels. This critical analysis of these potential combustion factors can be useful to several research groups for understanding the key factors, challenges, and state of art of chamber modifications. It emerges from the literature that these modifications are easily adaptable and can accommodate a variety of research strategies and options. Thus, this review underscores that the continuation of this study should focus on compatible models with multiple advanced combustion strategies and computational tools in order to attain further refinements to the engine outcomes.