Pneumatic Cleaning Of Wet Concrete Particles Based On CFD-DEM Study On Dynamic Characteristics

With the increasing investment in road construction and the gradual improvement of road network in China,pavement maintenance has been paid more and more attention.Pavement crushing is an indispensable part of road maintenance.There are still many problems in the current mechanical methods.High-pressure water jet crushing technology can solve these problems better.The recycling of concrete crushed by water jet has become an important factor restricting the development of this technology.Therefore,in this paper,the pneumatic cleaning and pneumatic recovery are proposed to deal with the concrete particles broken by water jet,and the wet concrete particles are taken as the research object to carry out the research on the pneumatic cleaning of water-concrete particles based on multiphase flow coupling through theoretical analysis,numerical simulation and experimental verification.The main contents of this paper are as follows:The flow field was modeled and meshed,the gas-liquid-solid three-phase coupling was realized by EDEM and Fluent,and the complex non-spherical particles were established for pneumatic cleaning,which made the numerical simulation closer to the actual engineering problems,and the basic theory and model of computational fluid dynamics-discrete element method were explained.For the problem of particle incipience,the empirical formula of particle incipient velocity in previous studies is summarized and substituted into the particle parameters in this paper for trial calculation.The incipient motion of particles under different conditions was studied by numerical simulation,including the effects of target distance,nozzle incident angle,nozzle height and liquid height on the incipient motion of particles,and the correctness of the conclusions was demonstrated by gas velocity nephogram and particle position-time image.Aiming at the problem of multi-particle cleaning,the numerical simulation method was used to study the same kind of particles,which kind of airflow would make the moving particles reach the expected position for the subsequent particle recovery work,and the particle coordinate change and liquid volume fraction nephogram were analyzed.For different numbers of particles,the airflow velocity is defined as a function of time to sweep,which is analyzed in conjunction with the particle initiation time and the time to reach the desired location.About the pneumatic cleaning test,the equipment selection and the construction of the cleaning test bed are carried out,and the numerical simulation is verified and compared.For the single particle starting test,the specific starting time of the particle is observed by combining with the video recorded by a high-speed camera;for the multi-particle cleaning test,the comparison between the detailed cleaning process of the particle in the test and the numerical simulation,as well as the size of the central angle formed by the blank area formed by the cleaning particle are observed.