Numerical Simulation And Design Studies Of Cyclone Separators With Straight Tubes

With the increase of air pollution, urban fog and haze, and air quality reduction, environmental protection has become an important issue of concern for all countries. The strict emission standards are set down by country, and a higher demand on dust removal technology is put forward. So, high efficient new cyclone separators have also been further developed. The cyclone separator with prolonged vertical tubes has been paid attention to, because of avoiding the re-entrainment of already separated dust. But the research on the cyclone separator with prolonged vertical tubes is relatively few. In this paper, the numerical simulation and design of two aspects of the cyclone separator with prolonged vertical tubes are studied and analyzed.By studying theory and numerical simulation method of conventional cyclone separation, the Reynolds stress turbulence model (RSM) and discrete phase model (DPM) model are applied in the numerical simulation of flow field in the cyclone. Firstly, cyclone separator with prolonged vertical tube is taken apart and combined into four different structure of cyclones (containing the cyclone with tube).By adopting the same boundary condition, four cyclones are simulated to obtain the similarities and differences of flow pattern and separation characteristics. The results are as follows:(1) four cyclones with different dust outlet geometries have the same flow patterns, the distribution of tangential velocity is similar, and the pressure drop is without big difference. The vortex of cyclone separator with prolonged vertical tube is not changed with the additional tube, which is the outer quasi free vortex and inner quasi forced vortex. (2) The distribution and separation characteristics of the flow field are different. The inner axial velocity of the cyclone separator with straight pipe is 3m/s, larger than that the other separators because of sudden decrease of diameter. Due to an additional separation, the cyclone has the highest separation efficiency on particles under 5 ?m.Five cyclones (called A, B, C, D, E) with different length of tube are simulated, which of length are 1.5,1.75,2.0,2.25,2.5 times of the diameter of the cylinder. By the analysis of flow field and separation efficiency comparison, a conclusion is drawn that swirl velocity, turbulence and pressure drop will decrease gradually, with the increase of the tube. The increase of the length of tube will increase the separation space, but it will bring about the attenuation of tangential velocity, the decrease of centrifugal force. Therefore, the separation efficiency is not just monotone increasing or monotone decreasing with the increase of the tube. The separation efficiency of the cyclone separator C is the highest, the pressure drop is moderate, and the optimum length of the tube is 2 times of the diameter of the tube. When pressure drop formula of Stairmand is used to predict the pressure drop of cyclone separator with the tube, the model of the pressure drop of the friction loss coefficient q has been corrected. It shows that the corrected pressure drop value and the simulation value are similar, which can prove the correctness of the modified method.Combined with the method on design of the inlet velocity and the optimal determined tube, the simple design method of cyclone separator with vertical tube is put forward, and is verified the feasibility of the method through an example calculation, which provides some useful reference for structure design of a single cyclone with vertical tube. In addition, when a cyclone separator can't meet the production requirements, a series of cyclones are usually arranged in parallel to achieve the production requirements. According to the economic cost model, the design method of the parallel arrangement of cyclone separators with vertical tube is put forward, which provides a reference for the optimal arrangement of the cyclone in the production.