To further improve the combustion and emissions performance of opposed-piston two-stroke (OP2S) engines, the implementation of a flexible injection strategy is crucial. The employed double injectors with different nozzle orifice diameters at different timings could make it easier to adjust the concentration stratification of the fuel–air mixture and better control the combustion characteristics. Despite the benefits, spray–spray impingement (SSI) is an unavoidable consequence of employing a dual direct injection system in OP2S engines. Therefore, this study aims to explore the influence of the flexible injection strategy on the SSI phenomenon. The results indicate that the impingement spray area and air entrainment are significantly reduced compared to those of the free spray. Additionally, the spray area is found to be proportional to t0.25 after impingement under synchronous injection. The observed phenomenon is attributed to the fact that SSI promotes droplet coalescence and suppresses the overall diffusion of the spray in the radial direction. Furthermore, the spray can be divided into dense core region, partial atomization region, and homogeneous mixture region by threshold sensitivity methodology to analyze spray spatial distribution and evaluate mixture formation more effectively. Finally, the injection strategy (Pinj = 180 MPa, ρamb = 50 kg/m3, ΔT = −800 μs) is selected to enhance atomization and mixing performance. This strategy is crucial for minimizing soot emissions and fuel consumption in the OP2S engines among the considered injection strategies.

Direct injection is an attractive technology for improving fuel economy and engine performance in gasoline engines. However, the adhered fuel formed on the piston surface has significant influence on the combustion efficiency and emissions. To obtain a better understanding of fuel adhesion, this work involved investigation of the spray and impingement on a flat wall through a mini-sac injector with a single hole. Different impingement distances and injection pressures were investigated. The evolution of the impinging spray was obtained by the Mie scattering method. The refractive index matching method was applied to measure fuel adhesion. The mass, area, and thickness of adhesion under different conditions were compared. The experimental results show that the fuel adhesion on the wall increases significantly with a large impingement distance. Moreover, the maximum thickness increases and the thickness uniformity of the fuel adhesion declines under a large impingement distance condition.