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• Cross-flow/ wall-impingement effects on fuel adhesion studied with split injection. • Fuel adhesion area decline rate rises with cross-flow velocity, stabilizing after 20 m/s. • Increased cross-flow velocity leads to a reduction in fuel adhesion thickness. • Fuel adhesion thickness also decreases with increasing wall-impingement distance. • Higher cross-flow velocity increases fuel adhesion mass reduction rate in later stages. In direct-injection spark ignition (DISI) engines, high-pressure fuel injectors introduce fuel into the cylinder, causing the spray to come into contact with and adhere to the cylinder wall; this is known as fuel adhesion. Over time, fuel adhesion contributes to carbon deposition on the cylinder wall, which affects its thermal conductivity and consequently diminishes engine combustion efficiency. This study investigates the influence of different impingement distances and cross-flow velocities on fuel adhesion under the triple injection strategy. The fuel adhesion propagation and side-view spray are measured using refractive index matching (RIM) and Mie scattering, respectively. The findings demonstrate that high cross-flow velocity promotes the fuel adhesion shape to be elongated strips. In the early stage, the growth rate of the fuel adhesion area increases with an increase in cross-flow velocity. In the later stage, the decrease rate in the fuel adhesion area initially increases with an increase in the cross-flow velocity; however, when the critical velocity threshold (20 m/s) is exceeded, the decrease rate in the fuel adhesion area tends to stabilize. The average fuel adhesion thickness then accordingly decreases with the increase in the cross-flow velocity and impingement distance in the later stage. In addition, the cross-flow promotes the volatilization of spray and fuel adhesion, thereby decreasing the fuel adhesion mass over time. In the context of carbon neutrality, this study underscores the importance of optimizing fuel injection conditions to reduce emissions and fuel consumption. [ABSTRACT FROM AUTHOR]

• Effect of injection strategies on fuel adhesion are investigated with cross-flow. • The cross-flow can promote the diffusion and evaporation of fuel adhesion. • Triple injection decreases the fuel adhesion characteristics in cross-flow field. • Deformation coefficient I d is proposed to evaluate the distortion of fuel adhesion. The flat-wall wetting phenomenon is inevitable because of the smaller cylinder volume and higher injection pressure inside direct-injection spark ignition (DISI) engines. The fuel adhesion phenomenon after wall impingement negatively affects the fuel spray mixture formation, the fuel consumption, and the pollutant emissions. In this study, the effects of different fuel injection strategies on the wall-impingement behavior were compared under static flow and cross-flow field conditions. The refractive index matching (RIM) method and high-speed video (HSV) camera were adopted to measure the propagation of fuel adhesion and the spray structure of the vertical plane, respectively. Meanwhile, a dimensionless parameter named "deformation coefficient I d ," which is defined as the fuel adhesion length divided by the width, is proposed to evaluate the degree of distortion of the fuel adhesion. Therefore, when I d approaches 1, the fuel adhesion shape approaches a circle. The results show that the cross-flow promotes the diffusion of the fuel spray, which leads to an increase in the fuel adhesion area. The fuel adhesion shape is similar to that of a slender strip under cross-flow field conditions, but almost maintains a circle under static flow field conditions. The cross-flow decreased the average fuel adhesion thickness. Meanwhile, the cross-flow also promotes the evaporation of the adhered fuel on a flat-wall, which leads to a reduction in the fuel adhesion area and mass with time. Additionally, it was found that triple injection can decrease the fuel adhesion thickness, area, and mass ratio under cross-flow field conditions. To achieve carbon neutrality, optimizing fuel injection strategies to reduce emissions is one of the primary purposes of this study. [ABSTRACT FROM AUTHOR]