Effects of secondary impinging on flow features and mixing performance in T-T jet reactors

•Flow regimes in T-T jet reactor are investigated with PLIF experiments and numerical simulation.•Effect of secondary impinging on different flow regimes is studied in detail.•The mixing performance of T-T jet reactors with various T-T gap ratios is compared.•The vanish of vortex structure is an important reason for the decrease of mixing. The improvement of mixing performance for the micro/mini impinging jet reactor is a pivotal and attractive topic in the chemical industry. In the present study, the Planar Laser-Induced Fluorescence (PLIF) experiment and numerical simulation on a novel T-T jet reactor that generated secondary impinging were carried out. In the T-T jet reactor, the influence of secondary impinging on various flow regimes at diverse Reynolds numbers was investigated in detail. The results show that, compared with the classical T jet reactor, the mixing of different flow regimes is intensified by the secondary impinging. The number and shape of the impingement planes of the segregated flow and vortex flow are changed. The steady engulfment flow generates more fluid filaments under the secondary impinging. The agglomerate created by the vortex-merging of unsteady engulfment flow is strengthened and the flow topology of the unsteady symmetric flow is modified. All the above indicates that the mixing performance is improved. In addition, the impact of the T-T gap ratio (κ = l/w, where l and w are the width of the T-T gap and the inlet channel, respectively) on flow characteristics and mixing performance in the T-T jet reactor was also considered. The configuration with the lower T-T gap ratio, i.e., κ = 0.2, presented a better global mixing performance than those with the larger T-T gap ratios, i.e., κ = 0.6 and 1.0.