This work examines the coalescence of two unequal-size spherical liquid droplets in the inviscid regime, with an emphasis on exploring the scaling of the liquid bridge evolution. Our experiment suggests that the classical 1/2 power-law scaling for equal-size droplets still holds for the unequal-size situation of small size ratios, but it diverges as the size ratio increases. Employing an energy balance analysis, we develop a theoretical model to collapse the experimental data of different droplet size ratios. The model reveals an exponential dependence of the bridge's radial growth on time, implying an intrinsic breaking of scaling law. The scale-free evolution behavior is evident only at late coalescence time and large size ratio, which can be explained using the length and time scales obtained from the theory.
