A Novel Approach for the Impingement of AdBlue-Droplets based on Smooth Regime Transitions

Impact of Surface Roughness on the Impingement of Urea–Water Solution Droplets

“…In the latter work, the top-end temperature limit of the thermal-induced breakup can be interpreted as LFP, which was reported at 300 °C. Both values for smooth surfaces were closer to the temperature found by Kuhn for a rough one, which might have been caused by the significantly larger droplets than in [8,24]. It also cannot be neglected that the rougher impingement targets were also porous in [11].…”

“…Kuhn (3 mm droplets) found an LFP of 220 °C for R z = 4.5 µm, with the temperature values also increasing significantly for rougher surfaces (330 °C on R z = 98.4 µm) [11]. For a smooth surface, this is much lower than the values found by Steinbach [24] or in earlier experimental investigations by the current authors [8]. In the latter work, the top-end temperature limit of the thermal-induced breakup can be interpreted as LFP, which was reported at 300 °C.…”

“…It was shown in the past that transitions can be observed [8,12], which contradicts the use of step-wise thresholds. An alternative classification approach based on a weighted superposition of four basic regimes can instead be used to capture smooth transitions [8].…”

“…As a kinetic parameter representing the droplet's stability during impact, the dimensionless Weber number (We) or K-number have been used, the latter being a combination of the We and Reynolds-number (Re) [3][4][5][6][7]. The We-number was chosen for the current study based on various examples in the literature and experience from previous investigations [8]. As shown in Equation (1), this calculation is based on the wall-normal component of the velocity v n , droplet diameter d, density ρ, and surface tension σ.…”

“…However, as indicated by the shaded areas between regimes in Figure 1, a transitional behavior was previously assumed, but this was simplified due to limited available data [3]. It was shown in the past that transitions can be observed [8,12], which contradicts the use of step-wise thresholds. An alternative classification approach based on a weighted superposition of four basic regimes can instead be used to capture smooth transitions [8].…”