Micromixing in the submerged circulative impinging stream reactor (SCISR) developed by the authors is investigated with the Bourne's reaction scheme. The values measured for the impinging velocity, u0, under the conditions of SCISR normal operation, only is of the order of 0.1m·s^-1, are much slower than that inferred,suggesting low power requirement for operation. The values of the characteristic time constant for micromixing,tM, determined in the impinging velocity range of 0.184m·s^-1 < u0 < 0.326m·s^-1 are ranged from 192ms to 87 ms, showing that impinging streams promotes micromixing very efficiently. The data follow approximately the relationship of tM∝ u0^-1.5. A comparative study shows that the micromixing performance of SCISR is much better than that of the traditional stirred tank reactor. The tM values predicted with the existing theoretical model are systematically longer than those measured by about 2--3 times, implying that the regularity of impinging streams promoting micromixing is unclear yet.
The characteristics of pressure fluctuation in a sub me rged circulative impinging stream reactor (SCISR) were experimentally studied.Th e instantaneous signals of pressure fluctuation resulting from the turbulence in the SCISR were measured by sensors and recorded by a computer.The pressure sign als at some special positions were sampled at different rotary speeds of propell er.After analyzing the signals with the Power Spectrum method,it was found that there was an inherent frequency in the dynamic pressure signals.The inherent fr equencies of the point on the impinging plane were greater than 1000 Hz,so the pressure fluctuation was called high-frequency fluctuation.The fluctuation velo cities with high inherent frequency resulted in a strong shear force field,whic h enabled the fluid to mix quickly on the micro-scale and the agglomerates of s olid particles to disperse effectively.
