Study On Vapor Saturation Distribution And Particle Condensation Growth In Turbulent Pipe Flow

With the development of society and the continuous acceleration of industrial processes,the situation of atmospheric pollution is severe,and the pollution caused by fine particles produced by industrial emissions has become increasingly prominent.However,it's difficult for the traditional dust removal technology to effectively collected fine particles in the micron range.Different from the idea of direct removal,fine particle condensing and growing pretreatment technology can make fine particles condense and grow first through electric field,sound field or saturated water vapor field and other conditions,reducing the difficulty of removing them,and then using subsequent dust removal methods for efficient treatment.Among them,the heterogeneous condensation growth technology creates a supersaturated environment by adding water vapor,which can cause heterogeneous condensation of fine particles to grow continuously.The heterogeneous condensation growth technology is highly economical,secondary pollution free,and has broad application prospects.At present,the research on particle condensation growth is mainly concentrated in low-speed nonturbulent scenarios such as growth tubes,and the influence parameters such as water vapor saturation are usually stable.However,in practical applications,the flow state is mostly turbulent,and its water vapor distribution and particle growth are still unclear and need further study.This topic selects two common industrial turbulent pipeline structures,venturi tube and equal-diameter circular tube,to explore the distribution characteristics of water vapor and the condensation and growth of fine particles in the turbulent pipe flow through experiments and simulation methods,so that the fine particles are fully condensed and grown.This research also provides theoretical support for the application of heterogeneous condensation growth technology in industrial turbulence scenarios.In the simulation study,firstly,the RNG ?-? model was selected to simulate the characteristics of single-phase flow field and calculate the turbulence.Secondly,the Mixture model and the EWF model were combined to establish the water vapor distribution model,calculate the water vapor migration and condensation,and study the water vapor distribution in the turbulent pipe flow.Finally,the LPT model was used to add fine particles to the water vapor field,and the UDF is written to simulate the particle condensation growth.In order to verify the reliability of the model,an experimental platform was set up to experimentally measure the flow field parameters(velocity,pressure drop),water vapor field parameters(relative humidity),and particle size.The model was checked and verified based on the experimental results.The validated model simulated and comparatively studied the distribution of water vapor and particle growth to obtain the distribution characteristics of water vapor and the law of condensation and growth of fine particles in the turbulent pipe flow.Finally,in order to allow the fine particles released in different positions to grow fully in the pipeline,three different structures of spoilers were added at the inlet and center of the pipes to analyze the influence of the spoiler on the flow field,water vapor field and particle growth in the turbulent pipe flow.The study of this subject has reached the following main conclusions: 1.When the inlet velocity of the pipeline increases from 6 m/s to 14 m/s,the overall water vapor distribution of the two turbulent pipelines does not change significantly,but excessively high velocity will shorten the residence growth time of the particles,and the particle size of the outlet particles will be smaller.2.There is obvious wall condensation in the water vapor in the venturi tube and the circular tube,and due to the presence of the laminar bottom layer near the wall,the migration of water vapor from the center to the wall surface will be inhibited,resulting in a water vapor unsaturated zone near the wall,which is unable to meet the demand for water vapor volume due to particle condensation growth.3.Adding a turbulence device in the pipelines can destroy the laminar bottom layer and cause the water vapor to migrate to the side wall,thereby eliminating the near-wall unsaturated area where the particles are unable to grow,and significantly improving the uniformity of the water vapor distribution.Therefore,fine particles can be fully grown,and the size of the outlet particles is more concentrated,which is more conducive to subsequent processing.