Experimental Study on Impingement Processes of Fuel Sprays on Biomimetic Structured Surfaces

To improve the controllability of the wall-wetting process after the fuel spray-wall impingement in internal combustion engines, the methods of laser etching, chemical etching and surface free energy modification are used to prepare biomimetic structured surfaces with different wettability. The impingement processes of diesel and n-butanol sprays on the walls under different conditions are experimentally investigated. As the surface oleophilicity increases, the spreading radius of wall-impinging sprays decreases. At about 5 s after the fuel injections, the fuel spray droplets hit the walls for the first time, and the secondary breakup and rebound occur. The mixture concentrations of different fuels hitting the various walls reach the peak value. Under a higher surface temperature, the peak value of the mixture concentration is mainly related to the heat flux to the fuel droplets in different boiling regimes from the metal surfaces. The concentration of the air–fuel mixture in the near wall region increases with increasing surface oleophilicity, increasing wall temperature and decreasing ambient pressure. Compared with diesel, n-butanol presents a higher air–fuel mixture concentration in the near wall region.