| In recent years,with the expansion of the scale of petrochemical and metallurgical enterprises,the frequency and scale of fire accidents in the production,storage and transportation of hazardous chemicals have increased.Chemically active metals and oils cannot be extinguished with water when they catch fire.In view of this situation,the development of a machine that can meet the long-range and continuous dispersal of solid materials will greatly help alleviate the severe situation of water-repellent hazardous chemical fires.Based on mechanical devices such as silage harvester and snow thrower,a blade type sand throwing device was designed in this paper.Theoretical analysis,simulation and experimental research were used to analyze and study the particle motion and scattering effect.(1)The working principle of the sand-throwing device was introduced,and the force of the particles on the impeller,on the throwing cylinder and after leaving the device was analyzed.According to the theoretical analysis,suggestions are made for the design of the sand-throwing device: the feeding position of the sand-throwing device should be located below the rotation area of the impeller,and the speed of the impeller should also be appropriately increased;when designing the throwing cylinder,it is necessary to consider the flight path of the sand particles leaving the impeller,and reduce the collision angle of the sand particles with the wall surface and the length of the throwing cylinder to reduce energy loss.(2)The method of coupling fluid mechanics calculation software FLUENT and discrete element software EDEM was used to simulate the sand throwing device with different parameter blades,and then the basic characteristics of the air flow field and particle motion parameters of the device were obtained.The analysis finds that the air velocity on the outside of the impeller is significantly higher than that on the inside;the average velocity of the particles at the exit position is greatly affected by the blade mounting angle,as the mounting angle shifts from backward to forward,the particle velocity gradually increases,and the velocity distribution of particles at the exit shows a Gauss distribution.(3)The high-speed imaging test of the particles in the rotating area of the impeller was carried out and the law of particle movement was obtained.The blade with a forward tilt of 10 ° has the highest throw angle,with a throw angle of approximately 107 °,and the blade with a 10 ° backward tilt has the smallest throw angle,with a throw angle of 76 °,the velocity of particle motion is 12.5 m/s in blades inclined 10 ° forward,10.7 m/s in the radial blades,7.7 m/s in blades inclined backward 10 °;comparing the test picture with the simulation picture,it is found that the simulation and test are very similar.(4)A sand-throwing platform was designed for the spreading test,and the average spreading distances of 9 different impeller types were obtained,it is found that blade inclination has a greater effect on average spread distance by analysis of variance;the distribution of the thrown sand was studied,it was found that in the longitudinal distribution,the distribution of the thrown sand is a quadratic function by the forward-leaving blade,and is linear by the radial distribution and the backward-leaving blade.According to the research results in this paper,the simulation of the CFD-DEM coupling method can well study the particle motion,and the simulation results are more in line with reality.The article obtains the angle of particle ejection and the distribution law of sand by means of high-speed camera research and spraying test,which provide reference and direction for the next optimization of sand ejection device. |
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