The numerical simulation of a new double swirl static mixer for gas reactants mixing

For the nitrogen oxide removal processes, high performance gas mixer is deeply needed for the injection of NH₃ or O₃. In this study, a new type of double swirl static mixer in gas mixing was investigated using computational fluid dynamics (CFD). The results obtained using Particle Image Velocimetry (PIV) correlated well with the results obtained from simulation. The comparisons in pressure loss between the experimental results and the simulation results showed that the model was suitable and accurate for the simulation of the static mixer. Optimal process conditions and design were investigated. When L/D equaled 4, coefficient of variation (COV) was <5%. The inlet velocity did not affect the distributions of turbulent kinetic energy. In terms of both COV and pressure loss, the inner connector is important in the design of the static mixer. The nozzle length should be set at 4 cm. Taking both COV and pressure loss into consideration, the optimal oblique degree is 45°. The averaged kinetic energy changed according to process conditions and design. The new static mixer resulted in improved mixing performance in a more compact design. The new static mixer is more energy efficient compared with other SV static mixers. Therefore, the double swirl static mixer is promising in gas mixing.