The interaction between injector spray behavior and in-cylinder airflow plays a decisive role in fuel–air mixing quality, combustion efficiency, and emission formation in modern engines. A mismatch between the spray field generated by the injector nozzle and the combustion chamber flow structure may result in fuel wall impingement, mixture stratification, and incomplete combustion. To better understand this interaction, this study investigates the matching characteristics between the injector spray field and the combustion chamber flow field using Particle Image Velocimetry (PIV) measurement techniques.
A constant-volume optical combustion chamber equipped with quartz windows is employed to provide optical access for PIV measurements. The chamber is designed to replicate representative in-cylinder flow patterns, including swirl and tumble motion, under controlled pressure and temperature conditions. A high-pressure injector is mounted centrally, and fuel injection is synchronized with the airflow field to capture transient spray–flow interaction processes.
The PIV system consists of a double-pulsed Nd:YAG laser, a high-resolution CCD camera, and tracer particles seeded into the airflow. Planar laser illumination is applied along selected cross-sections of the spray axis, allowing instantaneous velocity fields of both the airflow and spray-induced motion to be captured. Image pairs are processed using cross-correlation algorithms to obtain velocity vectors and turbulence intensity distributions.
Experimental results show that the alignment between spray penetration direction and dominant airflow structures significantly influences spray dispersion and breakup behavior. When the spray axis is aligned with the main swirl direction, enhanced entrainment of surrounding air is observed, leading to improved spray spreading and reduced local fuel concentration. In contrast, opposing spray–flow orientation causes spray deflection and velocity decay, increasing the risk of fuel impingement on chamber walls.
Quantitative analysis of velocity fields indicates that proper matching between spray momentum and airflow velocity promotes more uniform mixing, characterized by smoother velocity gradients and reduced turbulence anisotropy near the spray core. Furthermore, PIV results reveal that optimized nozzle spray angle can better adapt to the combustion chamber flow pattern, maximizing effective interaction time between fuel droplets and air.
In conclusion, the PIV-based experimental investigation provides detailed insight into the coupling mechanism between injector spray fields and combustion chamber flow fields. The findings highlight the importance of coordinated design of injector nozzle geometry and in-cylinder airflow structures. This research offers valuable experimental support for injector–combustion chamber matching optimization and contributes to the development of high-efficiency, low-emission engine combustion systems.
