Numerical investigation of in-cylinder swirl motion under cold start conditions in a diesel engine

The performance and efficiency of internal combustion engines, particularly diesel engines, are closely tied to the quality of air-fuel mixing and combustion processes. One of the critical factors influencing these processes is the in-cylinder airflow, specifically the swirl motion, which is the rotational movement of air around the cylinder axis. This swirl plays a pivotal role in enhancing the turbulence required for efficient fuel-air mixing, accelerating flame development, and improving overall combustion. This study shows a numerical analysis of the swirl movement within the cylinder of a diesel engine under cold starting conditions. Using computational fluid dynamics (CFD) analysis, the research evaluates the effects of various valve opening configurations on swirl intensity. The results indicate that increasing valve openings generally enhances swirl motion, improving combustion efficiency by promoting better air-fuel mixing. However, excessive swirl can negatively impact performance due to increased heat transfer and potential flame propagation issues. The study also assesses the impact of turbulence models and mesh density on the accuracy of the results, with the k-ε model providing predictions closest to experimental data. These findings contribute to optimizing engine design for improved combustion characteristics and reduced emissions.