| Spiral nozzle as one of the effective liquid atomization and dust reduction methods.Compared with direct injection nozzles,it has gradually attracted people's attention due to its advantages of high atomization degree,low energy consumption and simple structure,and is gradually used in under the control of coal dust in coal mines.However,due to the complicated flow state of the spiral nozzle,the researchers cannot form a complete clear understanding of its atomization characteristics,and the relevant atomization characteristics parameters in the coal dust control in the coal mines have not been reasonably matched.The liquid mist the effect of transformation has been greatly improved.For the above problems,the theoretical analysis,numerical simulation analysis and experimental research are used in this paper to combine and compare methods to systematically analyze and analyze the atomization characteristics of the spiral nozzle,and the spray pressure,spiral inclination angle and nozzle diameter make reasonable matches.First,theoretically analyze the liquid atomization mechanism and droplet formation process,the important parameter Weber number of the stability of a single droplet is determined by the formula,use the example chart to analyze the atomization process of direct nozzle and spiral nozzle,finally,analyze the atomization quality evaluation indexes such as droplet size,droplet size distribution function,nozzle flow rate,etc,in this paper,the atomization characteristics such as the range,flow rate,atomization angle,atomization droplet velocity and atomization droplet size SMD of the 30°,40°and 50°spiral nozzles are analyzed,the relationship between the system's spray pressure,nozzle spiral angle and nozzle orifice and other factors that affect these atomization characteristics.Make a theoretical basis for analyzing the relationship between them.Secondly,Fluent fluid simulation software was used to mesh and three-dimensional model the spiral nozzle,and the flow field was numerically simulated and analyzed using RNG k-? model and VOF method.The simulation results show that at the same spiral angle,for the liquid tangential velocity,inside the spiral nozzle,from the center of the spiral nozzle in the radial direction 1/4,the liquid tangential velocity increases linearly from 0,about It increases to the maximum at the middle position,and decreases linearly to 0when it is 1/4 away from the inner wall of the nozzle.For the liquid pressure,the pressure is the smallest at the center of the spiral nozzle,and the closer to the nozzle center,the more obvious the decrease is,and the pressure is the largest at the inner wall of the nozzle.On the axis of the spiral nozzle,the pressure loss of the structural change from the spiral chamber to the tapered section is not very obvious,but due to the rapid change of the structure during the injection of the tapered section to the nozzle section,the tangential velocity of the atomized liquid and The pressure is obviously reduced,and during the change of 5 MPa-6MPa,the tangential velocity of the liquid does not change significantly;at the same pressure,the tangential velocity of the liquid in the atomizing flow field changes with the decrease of the spiral inclination angle A nozzle with a large and small helix angle is about 20% faster than a nozzle with a large helix angle.As the helical inclination angle of the nozzle decreases,the atomization angle at the nozzle outlet becomes larger.By comparing the simulation results and Weber's atomization liquid breaking theory,we can determine that the helical nozzle atomization effect of the spiral inclination angle 30° spray pressure 5MPa and the aperture 1.2 mm good.Finally,according to the structural design of the spiral nozzle,a spray experiment platform was built,and the atomization characteristics of the spiral nozzle were tested.Use HX-6 high-speed camera to collect images,analyze the atomization angle,and use DP-02 laser particle size for particle size collection.Through the analysis of atomization test data,it is found that under the same pressure and at the same axial distance from the nozzle,the Soter diameter(SMD)and flow rate of the spiral nozzle increase with the increase of the spiral angle.The angle,velocity and range decrease with the increase of the helix angle;under the same helix angle,the law of the system's spray pressure on the atomization characteristics of the spiral nozzle is;the range,flow rate and droplet velocity increase with the increase of the system's spray pressure On the contrary,as the injection pressure of the system increases,the atomizing angle of the nozzle outlet and the Soter diameter(SMD)decrease accordingly;the law of the effect of the structure size of the spiral nozzle body on the atomizing characteristics is: at the same pressure,the distance from the nozzle axis At the same distance,for a nozzle with a helix angle of 30°,the atomizing droplet Soter diameter(SMD)and atomizing cone angle increase as the nozzle diameter increases.With respect to the nozzle cavity diameter,the nozzle diameter of the nozzle cavity of 10 mm is smaller than that of the nozzle cavity of 6 mm,and the atomization droplet Soter diameter(SMD)is smaller,and the atomization cone angle is larger.Through the comparison of experimental data,the spray effect of the nozzle with a spiral inclination angle of 30° and a spray pressure of5 MPa and a nozzle diameter of 1.2 mm is the best,which is consistent with the numerical simulation results.The liquid atomization process of the spiral nozzle is relatively complicated.The analysis and research in this paper further clarified its atomization characteristics,and the atomization parameters affected by it have been properly matched,which will have important practical value and theoretical significance for the prevention and control of coal dust in coal mine working face in the future. |
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