Gas-solid Two-phase Flow Simulation Of Dust Distribution Law In Fully Mexhanized Excavation Face

Fully mechanized excavation face is one of main dust production places in coal mine.It has characteristics of high dust production,many mechanical equipments,large ventilation air volume,narrow space and long single-head ventilation distance,which leads to complex flow of airborne dust in the face and has dust prevention and control becoming more difficult.High concentration of dust will reduce the visibility of the working face,accelerate the wear of equipment,damage breathing system of the miner,and form a hidden danger of explosion,which seriously threatens safe production of the mine and safety of the miner.There is an urgent need to investigate the distribution rules of gas-solid flow in fully mechanized excavation face,so as to provide a theoretical basis for treatment of flour dust in fully mechanized excavation face.The method of combining on-site measurement and numerical calculation was used to study characteristics of dust and airflow movement in fully mechanized excavation face.Main concludes are as follows:(1)The Rosin-Rammler distribution function was used to fit dispersion of sampled dust in 2601 working face of a mine.A proportional physical was established model based on actual working conditions of working face The three-dimensional mathematical model of dust diffusion in excavation work has calculated to simulate airborne dust migration process in fully mechanized mining face.The independence of the grid had been detected by comparing air velocity at measuring points.(2)By analyzing the distribution characteristics of air flow field,dust movement trajectory and space-time distribution characteristics of fully mechanized excavation face,it was found that airborne dust mainly spreads along return air side deep in working face,and there is a phenomenon of dust backflow behind the roadheader.The space division was used to study dust concentration distribution in space around driver of the roadheader,it was found that dust diffused from front,left and rear to driver's surroundings.Among them,amount of dust from the back of the driver is higher than that from the front.(3)The flour dust return mechanism of fully mechanized excavation face was revealed by changing ventilation air velocity and dust production rate.There is a "negative pressure zone" between outlet of the press-in air cylinder and cutting face,and its influence range varies with air cylinder.Center pressure of "negative pressure zone" decreases as air velocity increases.Vortex flow formed by suction in negative pressure area carries dust behind roadheader to form a backflow.The dust backflow is from the wind return side,then it passes driver of roadheader and gather at "negative pressure zone".With increase of ventilation air velocity,backflow coverage area increases firstly and then decreases.Dust concentration near the front face is almost affected by dust production rate,and dust concentration in ackflow dust belt is compared The outside is more likely to increase with increase of dust production rate.