Efficient fuel–air mixing in internal combustion engines depends on the effective interaction between the injector spray and the in-cylinder airflow. While previous studies have focused primarily on spray penetration or flow structure visualization, limited attention has been given to the energy exchange mechanisms governing spray–flow matching. In this work, Particle Image Velocimetry (PIV) was employed to analyze the energy transfer and turbulence interaction between the injector spray field and the combustion chamber flow field.
Experiments were conducted in an optically accessible combustion chamber capable of generating controlled air motion with adjustable intensity. The injector was operated under various injection pressures, while the airflow strength was independently regulated. PIV measurements were performed to obtain instantaneous velocity fields before and after injection, enabling the calculation of turbulent kinetic energy and velocity fluctuation intensity within the interaction zone.
The results demonstrated that effective spray–flow matching is closely associated with balanced energy exchange. When the kinetic energy of the spray jet was comparable to that of the surrounding airflow, a strong coupling region developed near the spray boundary. In this region, large-scale airflow structures were fragmented into smaller vortices, increasing turbulence intensity and promoting rapid fuel dispersion. Conversely, excessive spray energy suppressed airflow motion, resulting in a narrow spray plume with limited lateral mixing.
Turbulence scale analysis revealed that favorable matching conditions enhanced the cascade from large-scale vortices to small-scale turbulent structures. PIV-derived velocity spectra showed an increase in high-frequency velocity fluctuations in well-matched cases, indicating intensified micro-mixing. In contrast, poor matching conditions exhibited dominant low-frequency components, suggesting insufficient turbulent breakdown and reduced mixing efficiency.
To quantitatively assess spray–flow interaction quality, a dimensionless energy coupling coefficient was introduced based on the ratio of spray-induced kinetic energy to ambient airflow energy. This coefficient showed a strong correlation with turbulence enhancement and spray dispersion uniformity, providing a useful metric for evaluating matching effectiveness.
In summary, the PIV-based analysis of energy exchange and turbulence interaction offers a deeper understanding of spray–flow matching mechanisms. The findings suggest that optimal injector design and injection strategies should aim to balance spray and airflow energy levels to maximize turbulent mixing. This study provides a new experimental perspective for optimizing combustion chamber air-motion design and fuel injection parameters in advanced engine systems.
