The matching relationship between the injector spray field and the in-cylinder flow field is a critical factor influencing fuel–air mixing efficiency, combustion stability, and pollutant formation in modern internal combustion engines. An improper match may lead to spray deviation, wall impingement, or locally rich mixtures. To clarify the coupling mechanism between spray dynamics and chamber airflow, this study conducts a Particle Image Velocimetry (PIV) experimental investigation under controlled conditions.
An optically accessible combustion chamber is employed to reproduce representative in-cylinder flow structures, including swirl-dominated and tumble-dominated flow patterns. A high-pressure injector equipped with a multi-hole nozzle is installed at a fixed position relative to the chamber center. Injection timing and airflow conditions are precisely synchronized to capture transient interaction between the spray and the background flow.
The PIV system consists of a double-pulse laser source, a high-speed camera, and neutrally buoyant tracer particles seeded into the air phase. Planar velocity fields are measured at multiple cross-sections perpendicular to the injector axis. By comparing velocity distributions before and during injection, the influence of spray momentum on the surrounding airflow is quantitatively evaluated.
Experimental results indicate that effective matching between spray penetration direction and dominant airflow structure significantly enhances air entrainment into the spray plume. When the spray axis aligns with the main swirl direction, the spray exhibits wider dispersion and increased turbulence intensity at the spray boundary, promoting rapid fuel–air mixing. In contrast, misalignment between spray direction and airflow causes asymmetric spray deformation and reduces effective interaction time.
Further analysis of velocity gradients and vorticity fields reveals that properly matched conditions generate stable shear layers between the spray and airflow, which facilitate droplet breakup without inducing excessive flow disturbance. A spray–flow matching index based on momentum ratio and turbulence amplification is introduced to quantitatively assess coupling effectiveness. Results show a clear correlation between this index and spray dispersion uniformity.
In conclusion, the PIV-based experimental study provides detailed insight into the matching characteristics between injector spray fields and combustion chamber flow fields. The findings highlight the importance of coordinated optimization of injector nozzle design and in-cylinder flow organization, offering valuable guidance for improving combustion efficiency and reducing emissions in advanced engine systems.
