| Ash deposition phenomenon on the tail pass of the boiler and heating surface on the horizontal pass is common. Using numerical simulation method in the fly ash deposition research has a long history at home and abroad. As research of fly ash transport, collision and deposition mechanism related to in-depth study, the numerical model and the continuous improvement of the algorithm, numerical simulation study of fly ash deposition is currently into a mature stage.Earlier studies mainly with the help of the programming code as a means of research, provided such as Fluent, CFX software with the commercial value, a large number of researchers have started to use convenient modular operation on the deposition and some results are obtained. Commercial software in physical modeling, control solution, two phase coupling, particles transport and so on to give users a great convenience and a certain degree of choice. However, because of the limitation of function, Commercial software cannot fully meet the requirements of users in some special circumstances, the programming code to solve the problem of fly ash deposition still has an irreplaceable role.First of all, the numerical simulation research on the fly ash deposition has carried on the brief review and summary in this paper. In the final analysis, the paper found that the research content of deposition process and deposition judgement are relatively abundant, deposition process is mainly related to transport, adhesion, inertia collision, etc., and there are three main deposition judgement model: velocity model, viscosity model and the rule of force model. Studies mainly relied on the programming code, there also are some auxiliary choices, such as using the commercial software Fluent with UDF code completing fly ash deposition decision process.Two ways of fly ash deposition process are mainly studied in this paper, respectively is: with the help of Fluent software and UDF code, using dynamic grid module implements fly ash deposition process simulation; Using C++ programming code, the discrete equation of N-S equation, with the help of IBM immersed boundary method to simulate the process of fly ash deposition. Using two ways to get the results of numerical calculation, and compared the experimental results of Inner Mongolia lignite ash deposition in sedimentation furnace.The experimental results showed that with the increase of the secondary wind speed, height of the fly ash deposition on circular probe gradually increase; Changes after the probe diameter, deposition height change is not big, deposition heights of smaller diameter probe are slightly higher than the large diameter of the probe at most monument. Two types of numerical simulation results and experimental results show that: In terms of deposition height, dynamic mesh technology, numerical results and experimental results fit better, IBM immersed boundary method in early deposition trend is not obvious, which grew slowly. The growth of the late stage came to agreement with the experimental results; In terms of deposition morphology, results of dynamic mesh technology is more smooth, but the boundary morphology is narrow, sharp, does not accord with the experimental results, the IBM immersed boundary method of deposition morphology slightly rough, the boundary of the morphology show wide and flat shape, fit with the experimental results.The computational efficiency between dynamic mesh technology and IBM immersed boundary method are different, about 90000 nodes number under the same model, for the same example, calculation efficiency of IBM immersed boundary method are nearly 10 times than dynamic mesh technique. In practice use, we should according to the appropriate selection to choose suitable numerical calculation method. |
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