Atomization Characteristic Analysis on Inside and Outside Flow Fields of Nozzle and Coupling Study between Dust and Droplet

Author:Xu Cui Cui

Supervisor:yao qing guo


Degree Year:2018





The nozzle is the key component in the spray dust-settling system,its atomization ability directly affects actual spray dust effect.In this study,distributor pressure nozzle is taken as an example and nozzle structure-spray field parameter-atomization mechanism-dust collecting effect was studied as a system.Based on the numerical simulation,FLUENT software was used to simulate the production and development of internal flow field under the pressure of 2MPa,and the nozzle structural parameters influencing the internal flow characteristics of spray were summarized.Taking the characteristics of swirling and velocity in the outlet section as the breakthrough point,the influence of nozzle structural parameters on internal flow characteristics and 1 resistance of nozzle,outlet atomization angle were studied.The simulation results show that outlet diameter(D2),swirl angle(α2),swirl positions(l)and flow areas(A)are is the main structural factor affecting the atomization effect of nozzle.In the spray field test of the nozzle,a spray test experiment of particle-velocity was designed based on PDPA spray test system,the joint distribution characteristics of micro particle-velocity in spray field are obtained.Combined with the kinetic characteristics of droplets,the spray field of distributor nozzle was divided into five regions:mixing region,expansion region,stability region,attenuation region and thinner region.The characteristics of each region are given:the small size droplets in mixing region is easier to obtain higher axial velocity;when entering expansion region,the droplet velocity is obviously reduced,and the droplet of large size is constantly splitting;in stability region,the droplet velocity of large size is larger,the size and velocity distribution of the droplets will tend to a relatively stable state under the joint effect of the breakage and collision of the droplets;the droplet velocity in attenuation region is very small,but some large droplets still continue to crush under air turbulence;the thinner region is the most peripheral part of spray,and the droplet velocity is basically 0 compared with air.As the pressure increases,the expansion region is shortened and the stability region is increased.With inlet/outlet diameter ratio increases,the position of expansion region and stability region move forward.The relationship between the spray dust effect and the spray field characteristics of different coal dust size and the coupling influence of coal dust structure on spray field were preliminarily studied and the correlation between dust suppressants and spray dust effect was investigated by indoor dust test.According to the experimental results,the dust fall areas of the spray field was further divided,the expansion region,the stability region and the attenuation region are the effective dust fall areas.Among them,the stability region is the best dust fall area for spray,and the best dust fall area of respirable dust is in the middle and posterior part of the stability region.According to the main sources and characteristics of dust in fully mechanized mining face(93 下06 working face)of Nantun coal mine,shearer nozzle and hydraulic support nozzle were optimized.Based on the test results and match the pressure parameter of nozzle,the spray dust effect of the improved spray dust control system was checked in combination with field application.Field measurement shows that the water spraying dust suppression technology in this study has good spray dust effect.