Study On Distribution And Motion Feature Of Salt-Out Crystal Particles In Impeller Of Centrifugal Pump

The two-phase flow associated with the process of salting, the evolutionary processes can be a combination of different phenomena like nucleation, growth, dispersion, dissolution, aggregation, and breakage producing the dispersion. Therefore, the number of crystal particles in solution, particle size and chemical composition are changing constantly, and greatly increasing the difficulty of numerical studying salt-out two-phase flow field. The partilce size distribution and motion feature of salt-out crystal particles determines the area and the internal rate of salt deposition directly in the salt-out two-phase flow. It is one of the main salt-out theoretical system, but still at the exploratory stage.Under the support of National Natural Science Fund(No.50476068) and the Doctoral Foundation of Ministry of Education of China "Mechanism study of separation of fluid phases in the salt solution transferring process" (No.20060299008), centrifugal pump as the study object, and Supersaturated solution of Na2SO4 as the conveying medium, The partilce size distribution and motion of salt-out crystal particles under different conditions was more comprehensive studyed. The main work and achievements are as follows:1. Present research states of the salt-out two-phase flow and the population balance model at home and abroad were introduced simply. The microscopic behavior of salt-out crystal particles and the basic theory of population balance model were described to provide theoretical support for the selection of numerical simulation model;2. Based on previous research, a centrifugal pump was designed and processed in order to supply model for the numerical simulation as well as experimental study;3. According to the structural parameters of the centrifugal pump, three-dimensional modeling software Pro/E was applied to sculpt the model pump. The unstructured grids were generated in the area of flow passage in the pump. In order to improve the grid quality and quicken the solution velocity, local encryption techniques were adopted;4. Consider the complex micro-behavior of crystal particles existing in the salt-out two-phase flow, population balance model (PBM) is introduced based on two-fluid model in the Mixture when numerical simulated the two-phase flow field in centrifugal pump, to describe the phase-phase force in multiphase and all kinds of microscopic phenomena. The partilce size and class fraction distribution of salt-out crystal particles at different flow rate, solid volume fraction, temperature were obtained in impeller flow field of the centrifugal pump, and conclusions were obtained such as that "large particles within the flow are partial the blade pressure side when come into the channel";5. The particle image velocimetry (PIV) of the working principle was introduced. It is used to measure the salt-out two-phase flow field of centrifugal pump, so as to the partilce size distribution and motion of salt-out crystal particles obtained in the impeller flow field was precise. This tested that the the numerical results is accuracy and the population balance model was feasible to study the fluid mechanical theory of salt-out two-phase flow, and showed the motion feature of crystal particles. Conclusions were proposed such as "the greater change of crystal particles relative velocity in a flow passage near the exit of the flow channel".