Fractal injectors can be used to intensify liquid-phase processes. The flow field, vortex structure and turbulent mixing performance induced by fractal injectors with three different fractal dimensions (D = 2, 2.58 and 3) are investigated. CFD simulations, using a renormalization group (RNG) k-ε turbulence model, are validated with particle image velocimetry (PIV) measurements. The structure and formation mechanism of the vortices are studied. Both spiral and double toroidal vortices are produced, the latter by jet impingement. These vortices interact with each other within a fractal generating unit. For the same total volumetric flow rate, a fractal injector with D = 2.58 can achieve better mixing uniformity than fractal injectors with D = 2 or D = 3, while maintaining a similarly high mixing rate to when D = 2. This is due to enhanced entrainment by mutually interacting double toroidal vortex pairs and turbulent mixing
