Computational Fluid Dynamics Analysis of Combustion Characteristics in a Direct-Injection Engine with Varying Swirl Ratios and Hydrogen Addition

This study investigated the influence of swirl ratio and injection timing on combustion characteristics and emissions in a direct-injection diesel engine using hydrogen, a renewable and low-emission fuel that has gained attention as a potential alternative to conventional fuels. The superior combustion properties of hydrogen make it an ideal candidate for meeting stringent emission norms. A numerical simulation of non-premixed combustion in a direct-injection engine was carried out, incorporating a dynamic moving mesh for accuracy. The engine geometry was modeled and meshed using GAMBIT, while Computational Fluid Dynamics (CFD) simulations were carried out using ANSYS FLUENT. The simulation focused on compression and ignition stroke conditions, analyzing the effects of varying swirl ratios and hydrogen enrichment on temperature and pressure. The results showed that increasing the swirl ratio from 1.4 to 4.1 led to a 12.06% rise in peak cylinder temperature and an 8.7% increase in nitrogen oxide emissions while reducing soot emissions by 30%. The results highlight how optimized swirl ratios and hydrogen addition improve combustion efficiency and reduce emissions. These findings contribute to the development of high-performance, low-emission engines and demonstrate the potential of hydrogen as a sustainable fuel solution.