Understanding the transient interaction between fuel spray and in-cylinder airflow is essential for optimizing mixture formation in advanced internal combustion engines. Unlike studies focusing solely on spray morphology or airflow structures, this work emphasizes the dynamic evolution of spray–flow coupling and its quantitative characterization using Particle Image Velocimetry (PIV).
An optically accessible combustion chamber is utilized to simulate realistic in-cylinder flow conditions under non-reacting environments. Controlled swirl and tumble flows are generated through adjustable intake ports, while a high-pressure injector is installed at a fixed location relative to the chamber center. The experimental setup allows independent control of injection pressure, injection duration, and airflow velocity, enabling systematic investigation of spray–flow interaction mechanisms.
PIV measurements are conducted using seeded tracer particles illuminated by a pulsed laser sheet. Time-resolved velocity fields are captured before, during, and after fuel injection. Special attention is given to the temporal evolution of the flow field induced by spray momentum. By comparing pre-injection and post-injection velocity distributions, the disturbance and reorganization of the airflow caused by the spray can be quantitatively evaluated.
Results demonstrate that the fuel spray significantly alters the local flow field by introducing high-momentum jet structures and enhanced turbulence levels. The interaction region expands rapidly during the early injection phase, forming complex shear layers between the spray plume and surrounding airflow. These shear layers promote droplet breakup and air entrainment but also lead to strong velocity gradients and localized vortical structures.
To quantify the degree of spray–flow interaction, dimensionless parameters such as momentum ratio and turbulence amplification factor are introduced. PIV data show that higher spray momentum relative to airflow strength leads to dominant spray-driven flow, while lower momentum ratios allow the airflow to redirect and reshape the spray structure. Additionally, the decay rate of spray-induced turbulence is found to depend strongly on background flow intensity.
This study highlights the importance of considering spray-induced flow modification rather than treating the airflow as a fixed boundary condition. The PIV-based analysis provides a comprehensive framework for evaluating spray–flow interaction dynamics, offering valuable insights for injector design optimization and combustion chamber flow control strategies.
