Numerical Simulation And Experimental Studies Of Turbulent Impinging Streams

Large scale coal gasification technology is not only the main approach to solve the shortness problem of liquid fuel but also the key part of the clean coal technology. Therefore, it is significant to study the approach of large scale, high efficiency coal gasification for the national energy safety and the environment protection. And impinging streams is the major flow modality in the practice of coal gasification.In this thesis, we study the turbulent impinging stream produced by two opposed jets without any wall confine. Both numerical simulation by CFD code (Fluent 6.2) and experiments by PIV have been taken. During numerical simulation, a group of turbulence models are presented including classical models based on Reynolds stress decomposition such as standard k-εmodel,renormalization group k-εmodel (RNG k-εmodel) and Reynolds stress model, and large eddy simulation (LES) based on space filtered equations. The results of standard k-εmodel,RNG k-εmodel and Reynolds stress model were compared with the experimental data obtained for the case of two interacting opposed jets. According to the comparison, we found that all the results could reflect the fundamental character of the flow field between two opposed jets and that RNG k-εmodel, which takes into account the swirling of the averaged flows, yields to a better result than standard k-εmodel and Reynolds stress model. We also found there were still some difference between the numerical results and the experimental data. It is difficult for them to capture the unsteady character of turbulent impinging streams. As far as large eddy simulation is concerned, the simulation results display the flow swing and show the visual flows of the impinging region. During experimental study, the flow visualization experiments and the flow measurement experiments were studied by PIV.It is a primary research of the impinging stream, and many other scopes need to be studied in detail, such as the relationship between the geometry and the flow mixing, the modification of the existing turbulent models, experiment device improvements and etc.