2021 年 87 巻 901 号 p. 21-00143
The impingement of a single droplet on a liquid film is observed using a high-speed video camera. Specifically, an experiment is conducted to simulate the impingement behaviors of a fuel droplet on an engine oil film in a real engine. The droplets are composed of n-heptane and ethanol. The films pertain to engine oils with two viscosities. The impact of the engine oil type, droplet liquid type, droplet release height, and temperature and thickness of the oil film on the collision phenomenon is evaluated. The design of experiments scheme is used to identify the dominant parameters affecting the crown height and splash generation. The dominant parameters for the crown height are the oil film temperature, which affects the oil viscosity; droplet release height, which is related with the impinging velocity, and oil film thickness. The splash phenomena can be divided into two types, specifically, splash phenomena with split early type and crown break type, which are affected by the droplet release height and oil film temperature, respectively. The results demonstrate that the design of experiments scheme can help evaluate the dominant parameters in impingement phenomena.
