Mixing performances of fluids in three types of T-jet reactors were experimentally studied by planar laser induced fluorescence (PLIF) at 25 <= Re <= 200. The effects of Reynolds numbers, geometric parameters (jet separation and headspace of the channel) and excitation of pulsed inflow in the range of 0.5-25.0 Hz on the mixing performances in T-jet reactors have been investigated. Results show that the increasing Reynolds number is the primary factor for the enhancement of mixing rate during the transition from the segregated flow to the oscillation regime in T-jet reactors. The flow in the T-jet reactor with L/h>6 and w/h>8 (where L is the injector separation, w and h are the width and height of the injector) has been verified to display a half deflecting oscillation at small Reynolds numbers, which will enhance the mixing rate of fluids significantly. The mixing in T-jet reactors at low Reynolds numbers can be effectively enhanced by the excitation with low frequencies, as a periodic oscillation is induced by the pulsed inflow, which further causes the continuous folding and stretching of the impingement plane in T-jet reactors. (C) 2016 Elsevier Ltd. All rights reserved.