Simultaneous In-Cylinder Flow Measurement and Flame Imaging in a Realistic Operating Engine Environment Using High-Speed PIV

Abstract

Among multiple factors that affect the quality of combustion, the intricate and complex interaction between in-cylinder flow/turbulent field and flame propagation is one of the most important. In this study, true simultaneous, crank-angle resolved imaging of the flame front propagation and the measurement of flow-field was achieved by the application of high-speed Particle Image Velocimetry (PIV). The technique was successfully implemented to avoid problems commonly associated with PIV in a combustion environment, such as interferences and reflections, avoided thanks to a number of adjustments and arrangements. All experiments were carried out inside a single-cylinder optical gasoline engine operated at 1200 rpm, using port fuel injection (PFI) with stoichiometric mixtures. It was found that the global vortex location of the tumble motion heavily influences the flame growth direction as well as the flame shape, mainly due to the tumble-induced flow across the ignition source. The flame propagation also influences the flow-field such that the pre-ignition flow can be maintained and the flow of unburned region surrounding the flame front will be enhanced.