| In this paper,Computational fluid dynamics(CFD)numerical simulation analysis method was used to study the influence of sludge characteristics and pipeline characteristics on the Friction loss of sludge pipeline transportation in sewage plants.The main research work of the paper is as follows:(1)The effectiveness of the simulation model was verified by comparing the concentration cross-section distribution and pressure loss with experimental data in literature using a multiphase flow Euler model.When the flow rate is 1 m/s,the maximum particle concentration at the bottom is 38.9%.As time progresses,the slurry inside the pipeline continues to accumulate,ultimately causing blockage of the pipeline;When the flow rate increases to 5 m/s,the sediment concentration at the bottom decreases to 11.7%,and the concentration of upper particles further increases.The minimum particle concentration at the upper part increases from 0.001 to 0.087.The difference between the simulated pressure drop data and the experimental values is between-12%and 10%,with an average error of+1.58%.The difference is small,and the predicted pressure drop is in good agreement with the experimental measurement results.(2)Based on CFD software,numerical simulations were conducted to investigate the changes in frictional loss under different flow rates,pipe diameters,sludge concentrations,and 90 °bend conditions.Under the condition of the same pipe diameter and concentration,the simulation results of inlet velocity of 1 m/s,2 m/s and 3 m/s respectively show that the increase of inlet velocity will lead to a Exponential type increase in pressure drop,and different inlet velocity will also affect the location of the maximum sludge velocity in the pipeline;Simulations were conducted on pipelines with diameters of 100mm,200mm,and 300mm,respectively.The results showed that as the pipe diameter increased,the pressure drop decreased rapidly;When the sludge concentration is 2.58%,3.84%,and 5.79%,respectively,in a 100mm diameter pipeline,the sludge pressure drop increases with the increase of sludge concentration,indicating a significant impact of sludge concentration on the pressure drop;When the sludge passes through a 90° bend,the outer side of the bent pipe is more impacted,making it more prone to wear and corrosion risks.The flow rate has varying degrees of deviation compared to straight pipes.(3)Based on the above numerical simulation results,the influence of different parameters on the Friction loss and friction coefficient of Pipeline transport is analyzed.When the sludge concentration is 3.84%and the conveying flow rate increases from 1 m/s to 2 m/s,the friction coefficient decreases from 0.0679 to 0.0313,indicating that the friction coefficient decreases with the increase of flow rate and tends to stabilize after 1.5 m/s;When the inlet flow rate is 1 m/s and the sludge concentration increases from 2.58%to 3.84%,the friction coefficient increases from 0.055 to 0.064.However,when the sludge concentration increases from 5.79%to 7.63%,the friction coefficient increases from 0.088 to 0.131,indicating that the friction coefficient increases with the increase of sludge concentration,and the relationship between the two is closely related;In addition,the friction coefficient decreases with the increase of pipeline diameter.The calculation formula of Drag coefficient is obtained from the simulation results of friction loss characteristics of sludge pipeline transportation λ=0.00702C ^ 1.112635[Dg/v ^ 2]^ 0.004858 provides a theoretical basis for the subsequent calculation of conveying resistance and the selection of conveying equipment. |
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