| This topic is designed to conduct a theoretical research on the verticalcirculative impinging stream reactor, to build the impinging stream flowmodel, and to analyze particle velocity image in impinging stream.Impinging stream is a new type of highly intensive mixed reactor. It hassome characteristics that general reactors don’t have, such as strengtheninginterface transfer, deepening micromixing. It has been the concern of manyexperts and scholars and also been researched by them.Measurement of the flow field is one of the conditions in industrialmagnification. Therefore, measuring the impact stream flow field of verticalcirculative impinging stream accurately can provide convincing data toenlarge and industrialize it. Advanced dual light sources PIV flow fieldmeasurement system was established in this paper. The flow field of thedetail was recorded in the high-speed CCD cameras and its results wereanalylized by high-performance computer. Then the process of impingingstream was simulated by Ansys company’s flow field software CFX. Itssimulation steps can be divided into geometry modeling, meshing,pre-processing, solver, post-processing. Conclusion from experiment can bedrawn below:Simulation and measurements of this paper can lead to the followingconclusions: With rotation speed of400,800,1200r/min respectively,mathematical model of the impinging stream was established correctly andits elementary PIV measurements was conducted. Analysis is fast andconvenient and calculations are rather reliable which fits the actual workingconditions.From the analysis of the simulation and measurement results wecan notice that existence of stagnation surface in the speed flow field can beproved. There is stagnation area,that is, stagnation surface aroundimpinging surface edge and two pairs of whirlpool are formed. Under the influence of gravity, the fluid flow state on the impinging surface is stillroughly axisymmetric and it has an mirror image distribution. This showsthat the gravity effect on the vertical impinging stream high-speed collisioncan be negligible. From the simulation results it can be seen that themaximum speed is at the entrance to the draft tube. So the draft tube has afunction of tracting and restricting flow direction in the draft tube thus canmaximize the potential advantage of the impinging stream in mixing. It canalso be found from the draft tube at the outlet of the flow rate distributionhas a ladder-shape, so the assumption that the fluid outflow can be seen asplug flow approximately is not in line with the actual working conditions.With fluid moving towards the impinging surface, the axial flow rate declinerapidly as to the impinging surface has a low flow rate. The reason is thatthe axial velocity of the fluid to flow turns into radial velocity along the wall.PIV testing results show that the CFD software is a more realistic simulationof the impinging stream. The calculated and experimental results agree wellwith the experimental method. Therefore, the experimental method isfeasible. Considering the characteristics and advantages of impinging streamreactor, its popularization and application is of great practical significance.In addition, for scholars who have no condition to do PIV testing, thecondition is more realistic, results more realistic by using CFD softwaremodeling. Therefore, CFD allows us to organize the experimental resultsbetter, sum up the law, understand the mechanism profoundly and guide theexperiment. It can also help us save the necessary labor power, material andtime savings as well as improve productivity. |
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