## 3 Results and Discussion
### Characteristics of Satellite Droplet Formation and Bubble Dynamics  
Upon impacting the heated wall, the atomization effect significantly affects the evaporation characteristic of the droplet, which in turn impacts the heat-transfer process. This section addresses the characteristics and formation processes of satellite droplets. Davis V8.0 software is utilized for the identification and analysis of satellite droplets. The satellite droplets included in the statistics must occupy at least 15 pixels and should have a contour gradient exceeding 25% in order to minimize severe identification errors. Figure 6 illustrates the satellite droplet size distribution of the two types of binary droplets at \(T_{\rm s}\) = 120 \({}^{\circ}\)C. The diameters of satellite droplets originating from ethanol/propanol binary droplets are relatively small and do not change much with the increase in ethanol content. In contrast, the diameters of satellite droplets originating from ethanol/water binary droplets show a wider distribution, which tends to decrease with the increase in ethanol content. The two types of binary droplets primarily generate satellite droplets through mechanisms of puffing and ejection. Figure 7a,b and Figure 8a,b show the puffing and ejection behaviors of the two types of binary droplets at an ethanol content of 25 vol.% and a surface temperature of 120 \({}^{\circ}\)C. [PERSON] et al. (2018) have compared and analyzed these two secondary atomization modes and the corresponding satellite droplet diameters. Puffing is characterized by the rapid formation of small bubbles, which leads to the generation of secondary droplets with smaller diameters through the rupture of the liquid film. When the heat continues to transfer to the droplet and the bubble grows, a cavity is formed when the bubble breaks up. Under the action of surface tension, the cavity retracts, ejecting a liquid jet outward. Then, the tip of the liquid jet is pinched off to produce multiple secondary droplets due to the Plateau-Rayleigh instability. Supplementary Videos S1 and S2 show the complete binary droplet impact process under conditions corresponding to Figures 7 and 8. It can be observed that puffing occurs more frequently during the impact of ethanol/propanol binary droplets, whereas ejection is more prevalent in ethanol/water binary droplet impacts. The higher surface tension of water enables ethanol/water binary droplets to generate larger bubbles than ethanol/propanol droplets, resulting in larger satellite droplet diameters. Figure 5: Droplet residence time at different liquid components and surface temperatures. In the later stage of evaporation, the generation of large bubbles is often observed. This phenomenon is attributed to the decreasing ethanol content, which consequently leads to an increase in the surface tension of the binary mixtures. When multiple bubbles are formed, the bubbles undergo coalescence to form a bubble with a larger diameter. Comparing Figures 7c and 8c, for ethanol/propanol binary droplets, the bubbles cannot grow significantly due to lower surface tension, and the liquid film of the bubbles is thick. In contrast, for ethanol/water binary droplets, the bubbles can grow considerably due to the higher surface tension, and the liquid film of the bubbles is thin. As the amount of vapor continues to increase, the bubble ruptures, as shown in Figure 7c at \(t=830.3\) ms and Figure 8c at \(t=1926.2\) ms. The internal pressure within the bubble (\(P\)) can be obtained using the Young-Laplace equation, \(P=P_{0}+\frac{2\sigma}{R}\), where \(P_{0}\) is the atmospheric pressure and \(R\) is the radius of curvature of the bubble. It is shown that the larger a bubble grows, the lower its internal pressure, and the weaker the bubble rupture. In droplet combustion research, the rupture of large bubbles can lead to micro-explosions [40, 41]. Following bubble rupture, a liquid ligament is formed and then breaks into several secondary droplets.