An Experimental and Computational Study of a Single Diesel Droplet Impinging on an Inclined Dry Surface

Fuel spray interactions with piston surfaces and cylinder walls in internal combustion engines have been extensively studied in the past decades. However, there still exists an imperative knowledge gap on the fundamental understanding of dynamic droplet-wall interactions. Particularly, the impinging angle of droplet has been barely investigated as it renders asymmetrical droplet behaviors. This paper aims to provide detailed data of droplet-inclined surface impingement physics which could further support spray-wall model development. The experimental work of single diesel droplet impinging on an inclined dry surface was conducted under isothermal (25°C) conditions. Various droplet impact angle (φ) was achieved by adjusting surface tilting angle which was set from 0° to 45° in current study. A single diesel droplet impinged onto the inclined surface with different Weber number (around 20 ~ 800). Shadow graphic technique was adopted to capture droplet dynamic morphology changes after impingement which are characterized and quantified by spreading factor, contact angle of both downhill and uphill side. Besides, critical droplet impact Weber number of splashing under various impact angles were investigated and compared. The uphill and downhill side of the droplet showed different splashing behaviors. Finally, simulations of diesel droplet impinging on an inclined surface was performed in OpenFOAM by means of the volume of fluid (VOF) technique. An accuracy study on the minimum mesh size was carried out to guarantee the grid convergence of numerical results. The numerical results matched well with experimental results in terms of the spreading factor and the height ratio, which indicated that the presented simulation scheme will provide alternative insights of the dynamic impingement process of single droplet onto an inclined dry surface.