Analysis of Cycle-to-Cycle Variation in a Port Injection Gasoline Engine by Simultaneous Measurement of Time Resolved PIV and PLIF 2019-32-0552

Cycle-to-cycle variation (CCV) of combustion in low load operation is a factor that may cause various problems in engine operation. Variable valve timing and variable ignition timing are commonly used as a means to reduce this variation. However, due to mountability and cost constraints, these methods are not feasible for use in motorcycle engines. Therefore, development of an engine with minimal CCV without utilizing complicated mechanisms or electronic control is required. CCV of combustion may be caused by fluctuations in in-cylinder flow, air-fuel mixture, temperature, residual gas and ignition energy. In this study, the relationship between CCV of combustion, in-cylinder flow fluctuation and air-fuel mixture fluctuation was the primary focus. In order to evaluate in-cylinder flow fluctuation, Time Resolved Particle Image Velocimetry (TR-PIV) technique was utilized. In addition, Planar Laser Induced Fluorescence (PLIF) technique was used to measure spatial distribution of the mixture. These two visualization techniques were used together to measure continuous combustion cycles. The fluctuation of net IMEP can be explained by the fluctuation of Turbulence Kinetic Energy (TKE) and fuel concentration. In most cycles, net IMEP was correlated with TKE. In the remaining cycles, net IMEP was correlated with fuel concentration. The contribution of each factor towards net IMEP is to be discussed. It has been also confirmed that TKE fluctuation is caused by fluctuation in the tumble vortex structure, as shown in the authors' previous study [2] [13].