3. Challenges and Opportunities of Particle Imaging Velocimetry as a Tool for Internal Combustion Engine Diagnostics

To make further progress on in situ reduction of pollutant formation in engines, the understanding of combustible mixture preparation is vital. Time-dependent development of flow structures and distribution of turbulent kinetic energy (TKE) are instrumental in charge preparation for both premixed as well as mixing controlled combustion phases. Non-linear and unsteady nature of in-cylinder air motion has remained a grey area ever since the days of initial development of internal combustion (IC) engines. The optimization of in-cylinder flow structures and development of numerical models for an in-depth understanding of the in-cylinder processes has become critical in view of the need for complying with stringent emission regulations. This can be realized by in-cylinder flow visualization and continuous tuning and validation of Computational Fluid Dynamics (CFD) models. Particle Image Velocimetry (PIV) has evolved as a pioneering tool for the investigation of intake air-flow structure, flow interaction and fluid motion. However, there are several challenges for the utilization of PIV for in-cylinder flow investigations in IC engines. While the intricate geometry of engine creates hindrance for optical access, the dynamic nature of ambient conditions complicates the selection of seeds. The work presented in this chapter summarizes these critical issues along with the possible solutions. Comprehensive literature on the evolution of PIV as a diagnostics tool for engine application has been covered. A brief review on the impact of flow structures on the combustion and pollutant formation has been also discussed. This chapter is useful for thorough understanding of PIV and its applications in IC engine and provides direction for further innovations in the field.