To address the challenges of unclear coal dust migration laws and ineffective pollution control in fully mechanized caving mining of thick coal seams in gas mines, a typical high air volume fully mechanized top-coal caving (FMTC) face in a gas mine in Shanxi, China, was selected as the research object. Based on field measurements of wind speed and dust characteristics and laboratory analysis data, a precise dust release method based on a source-specific parameter matrix and particle size-mass conversion was proposed.The airflow field of the working face was calculated using finite element discretization combined with the Euler-Lagrange gas-solid two-phase flow method, and the migration trajectories of coal dust and spray droplets were simulated. The airflow distribution characteristics, combined pollution laws of multi-source coal dust, and source-specific contribution mechanisms of the FMTC face under downwind and upwind cutting conditions were revealed. A comprehensive wet dust suppression system was arranged according to the spray wind resistance test results, and its dust reduction effect was verified with the dust suppression mechanism elucidated.The results demonstrate that dust generated by shearer cutting forms a high-concentration dust pollution zone within 100 m between the downwind supports and the coal wall, with a maximum total dust concentration of 925.37 mg/m(3), which is the main dust source on the downwind side of the working face. The pollution severity of drum cutting dust to the pedestrian walkway area follows the order: upwind drum > downwind drum during downwind cutting, and the opposite during upwind cutting. The process of hydraulic support advancing and face guard retracting causes a large amount of coal to collapse, forming an extensively polluted "coal flow waterfall" between supports. Dust generated from this operation is characterized by high concentration, high wind speed, and high respirable dust proportion, making it the main source of respirable dust in the downwind pedestrian walkway. The pollution degree of support advancing dust to the pedestrian walkway is higher during upwind cutting than during downwind cutting. During top coal caving, dust leakage occurs through the gaps between supports due to top coal collapse, with respirable dust accounting for up to 63.8 % of the total dust. The pollution degree of top coal caving dust to the pedestrian walkway is higher during downwind cutting than during upwind cutting.The deflection degree of spray morphology is positively correlated with airflow velocity. High-pressure nozzles exhibit better wind resistance performance than pneumatic nozzles, with the high-pressure flat-head conical nozzle showing the optimal wind resistance. By arranging the dust suppression system targeting the core principles of "tracking and covering main dust sources with wind-resistant sprays, cutting off the core channels of dust diffusion, and adapting to source-specific contributions under multiple working conditions", precise prevention and control of dust pollution in the working face was achieved. The maximum total dust reduction efficiency in key dust pollution areas reached 91.29 %, and the maximum respirable dust reduction efficiency for all particle sizes reached 98.44 %. The research results can provide a theoretical basis and technical support for the precise prevention and control of multi-source dust pollution in FMTC faces of gas mines, and are of great significance for ensuring the safe and efficient mining of gas coal mines.

To solve the problem that the traditional spray dust suppression method cannot efficiently capture the respirable fine dust in coal mine, the high humidity and high temperature two-phase jet dust suppression technology was developed. In this work, a gas-liquid thermodynamic coupling experimental device was designed and built to evaluate the effects of different parameters on the atomization characteristics of this technology and to verify the dust suppression performance. The results indicate the uniformity of the spray distribution and the gas-liquid phase transition can be greatly improved by improving the thermodynamic performance of the system; The flash evaporation effect was intensified and the surface tension of the liquid was reduced under the optimal operation conditions of water supply temperature of 90 degrees C, gas supply temperature of 100 degrees C, gas supply pressure of 0.4 MPa and water flow rate of 150 mL/min. The average relative humidity of the whole field was 84.6% with a maximum of 94% locally; the median droplet size (SMD) was 10.71 mu m with a dust suppression efficiency of 93.7%. This technology solves the shortcomings of the traditional methods and provides an efficient, innovative technical solution to control respirable dust in the mining industry.

To further improve the dust control performance of charged spray, a micro-scale high-voltage electrostatic field was established based on supersonic pneumatic atomization spray technology, thereby enhancing droplet charging and dust removal efficiency. The charging and dust suppression characteristics of the proposed system were investigated through a combination of experimental measurements and numerical simulations. The results show that the droplet charge increases with increasing electrical conductivity of the electrode material, exhibits an initial increase followed by a decrease with increasing electrode diameter, and increases with increasing electrode spacing. Under optimal conditions, the maximum charge-to-mass ratio reached 820.8 mu C/kg. The dust removal efficiency of the charged spray exhibits a similar dependence on electrode parameters: it first increases and then decreases with increasing electrode diameter and increases with both electrode spacing and electrode material conductivity, reaching a maximum value of 94.93%. Under different electrode configurations, the supersonic charged spray exhibits distinct capture efficiencies for dust particles across different size fractions. These differences can be characterized by the instantaneous dispersion index and are governed by the droplet charging characteristics. An increase in droplet charge enhances the electrostatic attraction between droplets and dust particles, thereby facilitating the efficient capture of fine particles smaller than 5 mu m. This study advances the understanding of electrostatically enhanced spray dust capture and provides a theoretical and technical basis for the development of advanced charged spray dust suppression technologies.

To address the problem of poor collection efficiency of respirable coal dust in underground coal mines, a multistage stepwise dust removal fan utilizing supersonic dynamic mist was proposed. Based on the step function, five geometric structures of stepwise dust removal units were designed.The Discrete Phase Model (DPM) combined with the k-epsilon turbulence model was employed to investigate the internal flow field, droplet trajectories, and dust particle trajectories of each structure. In conjunction with experiments, tests were conducted using a thermal anemometer, laser particle size analyzer, dust sampler, and dust dispersion tester.The wind speed, Sauter Mean Diameter (SMD) distribution characteristics of droplets, and their evolution laws of each dust removal unit under different operating conditions were obtained.Finally, the optimal structure, operating conditions for dust removal performance, and the dust reduction mechanism were clarified.Results show that the multi-stage stepwise structure effectively enhances the dust-fog coupling effect. Affected by the heterogeneous turbulent field, dust and fog particles move in a vortex-like manner, which significantly prolongs the migration time of respirable dust inside the structure.This facilitates the collision and agglomeration of dust particles with droplets to form dust-fog coupling aggregates that settle.The abrupt change in the axial cross-sectional area of the dust removal unit is conducive to the capture of respirable dust by droplets.Under the same operating conditions, compared with the stepwise structure with a constant cross-section, the maximum relative improvement rates of collection efficiency for dust particles with particle sizes of 0 similar to 2.5 mu m, 2.5 similar to 5 mu m, and 5 similar to 10 mu m are 70.83%, 124.04%, and 65.3%, respectively.The symmetric two-stage incremental stepwise dust removal unit achieves optimal dust removal performance when the supply air pressure is 0.3 MPa and the fan speed is 300 RPM.The total dust removal efficiency measured based on dust mass concentration reaches 99.34%, and the mass-based dust removal efficiency for each particle size fraction exceeds 94%.The research results can provide theoretical and technical support for the efficient, simple, and economical control of respirable dust in underground coal mines.

High-intensity induced airflow caused by coal dropping at belt conveyor transfer points is the main driving force for long-distance diffusion of respirable dust, which seriously pollutes the underground working environment and endangers miners' occupational health. Traditional spray dust suppression is unsuitable for water-scarce mining areas, and unpowered dust removal devices fail under high induced wind speeds. Based on boundary layer separation and vortex dissipation theories, this study proposes an active stepped induced vortex dust suppression technology. A three-dimensional air-dust coupled numerical model is established using the CFD-DEM method and standard k-e turbulence model. Four stepped structures are designed and evaluated via numerical simulation and physical experiments. Simulations show that the square-loop and arc stepped devices achieve optimal dust suppression performance, reducing the average outlet wind speed by 54.7% and 54.9%, and shortening the 8-second maximum dust diffusion distance by 57.2% and 68.1%, respectively. Experiments verify that the square-loop device reaches respirable dust suppression efficiencies of 77.68% at the impact point and 75.72% at the outlet. This water-free and energy-saving device provides reliable theoretical and technical support for dust control in water-scarce coal mines. (c) 2026 Published by Elsevier B.V. on behalf of The Society of Powder Technology Japan. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

Pneumatic spray dust reduction technology is widely used in dust pollution control in the coal industry due to its advantages of high spray concentration, small droplet size, and fast movement speed. However, supersonic power spray dust reduction will be accompanied by severe high-frequency noise, which restricts the promotion of technology. To address this problem, this research develops a multi-material composite sound-absorbing device adapted to the high-frequency noise of supersonic power spray. It uses multi-field coupling simulations and experiments such as high Mach number and pressure acoustics to explore the noise characteristics of single- and multi-layer sound-absorbing chambers, verify the feasibility of the device, screen the optimal structure, and reveal the noise reduction mechanism. Research shows that the flow field velocity of the Laval nozzle in singleand multi-layer sound-absorbing chambers decreases outward along the central axis, and the flow field velocity inside the multi-layer chamber is even lower; the core area where sound energy is converted into heat energy is the sound-absorbing material in the inner layer near the nozzle. The three-dimensional network micropores of the porous fiber material can convert sound energy into heat energy and dissipate it, greatly reducing the sound pressure level of radial propagation. In a single-layer chamber, the noise reduction effect is optimal when the cavity diameter is 56 mm. The sound pressure level at the sound source is reduced by 10.9 % similar to 13.4 %, and the sound radiation direction is reduced by 7.3 % similar to 10.8 %. Under different materials, airgel has the best noise reduction effect, with corresponding reductions of 13.4 % and 10.8 %. Among the multi-layer chambers, com-posite method 5 has the best noise reduction effect, with a 21.2 % reduction at the sound source and a 12.4 % reduction in the sound radiation direction, which is better than the single-layer airgel chamber. When the aerodynamic pressure increases, the sound pressure level in each frequency band increases, and when the water flow increases, the sound pressure level in the middle and high frequency bands decreases. Under the same working conditions, the particle size of 50 % of the droplets is about 11 mu m, and the dust reduction efficiency exceeds 88 % in 3 min. This study not only ensures the efficiency of atomization and dust reduction, but also reduces the high-frequency noise at the sound source to below the national standard (GB12348-2008) 85 dB, laying a theoretical and technical foundation for the collaborative control of dust and spray noise.

To address the problems that the dust pollution law dominated by air distribution volume in coal mining faces is unclear, the key influencing factors of the wind resistance performance of spray are unknown, and the mechanism of environmental airflow on dust-fog coupling is not explicit, this study takes the 3217 working face of Shanxi Tiandi Wangpo Coal Mine as the research object. By combining numerical simulation with field and laboratory tests, numerical simulations were carried out on the airflow distribution and dust migration trajectory of the working face under different air distribution volumes, as well as the droplet migration trajectory and dust-fog collision behavior under the disturbance of environmental airflow. The wind resistance performance of different types of nozzles was tested, a dust control system was constructed, and the dust reduction effect of the system was verified via field tests. The influence of air distribution volume on airflow and dust migration was revealed, the key factors affecting the wind resistance of high-pressure and pneumatic sprays were clarified, the mesoscopic dynamic behavior of dust-fog coupling under environmental airflow disturbance was uncovered, and the optimal nozzle type was selected to build the dust control system. The results show that air distribution volume significantly regulates the airflow distribution and dust migration characteristics of the working face. Under low air distribution volume, the wind speed is high on both the inlet and return air sides of the shearer; under medium air distribution volume, the wind speed on the inlet air side of the shearer is higher than that on the return air side; under high air distribution volume, the wind speed on the return air side of the shearer is higher than that on the inlet air side. With the increase of air distribution volume, the dust migration distance, dust concentration and particle size range in the return airway increase. The dominant factor for the wind resistance of high-pressure spray is droplet size, while that of pneumatic spray is initial injection velocity; the high-pressure flat-head conical nozzle exhibits the optimal wind resistance performance. Dust wettability is positively correlated with dust-fog collision velocity, and the wettability reaches the maximum at a collision velocity of 11 m/s.After field application of the dust control system constructed based on this research, the dust reduction efficiency in key areas all exceeds 80%, and the highest dust reduction efficiency at the center of the return airway section reaches 90.77%. The research results provide key theoretical basis and technical support for efficient dust control in underground coal mining faces, and have important practical significance for ensuring the occupational health of operating personnel.

High concentrations of respirable dust are frequently produced during coal mining operations, and excessive inhalation can lead to severe respiratory diseases, such as pneumoconiosis, among underground workers. This poses a serious occupational health hazard. To address these risks, this study investigates a supersonic coaxial pneumatic atomization nozzle designed to enhance dust suppression efficiency. Employing numerical simulations and experimental methods, this study examines the internal airflow characteristics of the nozzle and experimentally investigates its atomization behavior under different operating conditions. Critical structural parameters of the nozzle, including the coaxial probe length and aperture as well as the diffuser length, were optimized to improve dust capture efficiency. The results indicate notable improvements in droplet size control and dust suppression efficiency, offering important insights for the design and application of advanced wet dust suppression systems in coal mines. These findings provide valuable data and theoretical support for strengthening dust control strategies and safeguarding worker health.Compared with existing studies, this work provides a systematic structural optimization of a supersonic coaxial pneumatic atomization nozzle and clarifies, through combined internal flow-field analysis and experimental characterization, the coupled mechanisms of flow-field evolution, droplet breakup, and fine-dust capture, demonstrating superior removal efficiency for respirable dust (0-5 mu m).

Dust is inevitably produced during coal mining, which seriously harms workers' health. To effectively reduce airborne dust concentration in the working environment, a novel supersonic dynamic micro-electrostatic spray dust collection device was developed. A combined strategy of numerical simulation and experimental investigation was employed to systematically assess the effects of aerodynamic pressure, charging voltage, and water flow rate on droplet atomization, droplet charging, dust deposition behavior, and dust dispersion before and after capture. The capture mechanisms of charged mist droplets against dust with different particle sizes were elucidated. The results demonstrate that the proposed device can generate a broad spectrum of high-speed, fine, charged mist droplets with a droplet diameter below 10 μm, a velocity exceeding 30 m/s, and a charge-to-mass ratio of 766.8 μC/kg, thereby substantially enhancing dust removal performance. The dust removal efficiency reaches 94.93%, which is approximately 4% higher than that of the uncharged case. Moreover, supersonic dynamic micro-electrostatic spray exhibits particularly strong removal effectiveness for ultrafine dust in the 0–5 μm size range, after dust reduction, its proportion decreases by more than 8%. The underlying action mechanisms vary with dust particle size, revealing a competitive relationship between electrostatic adsorption and inertial impaction. After droplet evaporation, electrically charged micro water-molecule clusters form under volume-fraction saturation conditions and subsequently deposit on the surfaces of dust particles, promoting particle wetting and thereby improving capture capability. Overall, these results provide a theoretical basis and technical support for efficient dust prevention and control in underground coal mining.

To address the challenge of insufficient control over respirable dust in coal mining operations using conventional spray technologies, a supersonic plasma-activated water mist dust capture system is proposed and developed. The atomization, charging, and dust removal characteristics of this system are investigated through a combination of numerical simulations and experimental studies. Results indicate that droplet size decreases with increasing atomization-gas pressure, reaching a minimum of 6 mu m, while it increases with higher liquid flow rates. Droplet velocity increases with atomization-gas pressure, initially decreases, and then stabilizes as liquid flow rates increase. Plasma activation significantly enhances the charge-to-mass ratio of the droplets, with the optimal charging effect achieved at an applied voltage of 6 kV. The combined effects of supersonic atomization and plasma activation improve the overall dust removal efficiency by nearly 7 % compared to non-activated spraying, reaching a maximum efficiency of 97.92 %. Fractional efficiency analysis shows that the activated spray captures particles in the 2.5-10 mu m range with efficiencies exceeding 80 % and effectively suppresses ultrafine particles (0-5 mu m), with capture efficiencies up to 85 %. This study provides valuable technical support for the prevention and control of fine respirable dust in mining operations.

When transporting coal in underground tunnels, airflow is induced by coal flow, which results in a large amount of diffuse coal dust. A high percentage of diffuse coal dust can seriously pollute the operating environment and jeopardize the health of coal miners. To address this problem, powered micromist vortex dust control technology and a management scheme based on supersonic water siphon atomization technology and the principles of limited-space vortex airflow and dust control are proposed for coal transportation. A three-dimensional numerical simulation model that tracks wind flow-coal dust-droplet transport during the coal transfer process in underground mines was established via the discrete particle model, finite element method, computational fluid dynamics (CFD) and the k-epsilon turbulence model while considering the induced influence mechanism of coal flow in the coal transfer process. The phenomenon of coal dust diffusion and pollution caused by induced airflow and ambient wind flow under the action of coal flow during the coal transportation process was studied at a transfer point. The three-dimensional spatial distributions of wind flow, coal dust, and droplets were analysed. To manage this type of coal dust pollution, the No. 85214 transfer point of the Sandaogou coal mine was taken as the research object. A powered micromist vortex dust control system was created at a transfer point, and numerical simulations and onsite experiments were established to study the coal transportation process both inside and outside the coal chute, the airflow induced by falling coal, the ambient ventilation airflow, the supersonic- powered micromist jet stream coupling state and its impact on fog droplets and dust, and the transportation characteristics of the mist droplets and dust. This explains the special distribution phenomenon of dust concentration and dispersion characteristics at different locations in the downwind side roadway of the transfer point in the field and reveals the dust control and reduction mechanism of this technology. The research results revealed that the high-velocity airflow region, large-scale vortex phenomena, and small-scale vortex phenomena in the reprocessing space are the key factors that cause dust to be stripped from coal. The airflow velocity is faster at the lower part of the coal flow hitting the wall, so the external ventilation flow line of the roadway is more affected near the gap than farther away. A large amount of dust is confined to the coal chute, and most of it is concentrated at the bottom of the chute, forming highly concentrated dust clusters that move at variable speeds with the internal vortex airflow. Most of the dust is affected by impact airflow, which accelerates and spreads from the gap between the lower conveyor and the chute to both sides of the roadway and is transported downwind. The transportation distance of dust at the top of the roadway is greater than that at the bottom plate, and the dust concentration and transportation distance near the impact side of the coal flow in the lower roadway are greater than those at other locations in the roadway. Owing to the faster airflow speed at the impact below the coal stream, the surrounding vortex flow of the highly concentrated dust mass is quickly pulled into the lower roadway through the gap between the sidewall and the conveyor. A dust control system is used at the transfer point of the coal chute and the surrounding roadway dust diffusion area to achieve full coverage, and the supersonic-powered mist spray formed by the internal multiscale vortex fog area can effectively prevent the flow of coal to the outside of the airflow induced by the coal chute from internal effective damage to the original aggregation of dust. The diffusion of the trajectory, the formation of a vortex so that the coal dust is wetting, and the aerodynamic characteristics are significantly changed, thus inhibiting dust from travelling outside the chute and escaping. For the fog droplets to capture dust to separate airborne wind flow and reduce the concentration, time and space are needed so that the dust captured by the fog droplets in the drop tank after leaving is transported a certain distance before settling rapidly. The dust control system has an obvious effect on the prevention and control of dust pollution at the transfer point, with an efficiency level reaching 86.78 %, but the inhibition of dust below 5 mu m still needs to be improved. This study provides theoretical support and effective management methods for simulating coal transfer point dust pollution mechanisms and managing coal transfer point dust pollution in underground coal mines.

Supersonic coaxial air spray dust removal technology is good in the treatment of respirable dust.It has the ad-vantages of high spray concentration,small droplet size and fast movement speed,but it will bring serious noise pollution,especially high-frequency noise.In order to solve this problem,the research group optimized the structure of the technical device.The velocity distribution and sound distribution of the flow field in Laval nozzle before and after optimization were studied by COMSOL Multiphysics software,and the feasibility was verified.Combined with the experiment,YSD130 noise analyzer,laser particle size analyzer and dust sampler were used to measure the spray noise characteristics and change rules under different pneumatic pressure and water flow,as well as the droplet size and dust removal effi-ciency of the two nozzles.The results show that in Laval nozzle,the sound pressure level of both nozzles decreases gradu-ally along the central axis.The thickness of supersonic layer of optimized nozzle is smaller than that of optimized nozzle,and the corresponding sound pressure level is smaller.When the water flow rate is 10 L/h,with the increase of aerodynam-ic pressure,the sound pressure level of high frequency band at the sound source of two nozzles shows an increasing trend,and the trend of increasing first and then decreasing at the propagation direction changes to an increasing trend before op-timization.Compared with the optimized nozzle,the optimized nozzle sound pressure level at the sound source is reduced by about 16.7%,the peak sound pressure level is reduced by 8.5%-9.3%,and the sound pressure level at the propagation direction is reduced by about 18%.When the pressure is 0.4 MPa,with the increase of water flow,the sound pressure level of the nozzle before optimization increases at the sound source,and increases first and then decreases at the propagation direction.After optimization,the sound pressure level of the nozzle at the sound source increases first and then decreases,the sound pressure level at the middle and high frequency band increases,and the sound pressure level at the propagation direction decreases.Compared with the optimized nozzle,the optimized nozzle sound pressure level at the sound source is reduced by about 9.8%,the peak sound pressure level is reduced by 19.2%-20.9%,and the sound pressure level at the propagation direction is reduced by about 12.7%.When the pressure is 0.4 MPa and the water flow rate is 12 L/h,the particle size of the droplets with 50%of the number of droplets in the two nozzles is about 11 μm,which can effectively capture micron dust.With the increase of test time,the dust removal effect increased linearly,and the dust removal effi-ciency of the two nozzles reached more than 84%.The research not only ensures the dust removal effect,but also reduces the noise pressure level in the atomization process through structural optimization,which provides theoretical and technic-al support for the safe application of supersonic aerodynamic dust removal spray and the collaborative control of dust and noise.

Supersonic aerodynamic spray dust removal technology has the advantages of high spray concentration, small droplet size and fast movement speed. It has good control over respirable dust, but it can cause severe highfrequency noise pollution. To solve this problem, the research team has carried out structural optimization and material optimization on the technical device (porous aluminum foam, porous stainless steel foam - 30-50 mu m). The velocity flow field and sound field of each nozzle were simulated via COMSOL Multiphysics software.In combination with these experiments, verify the feasibility of porous absorption and attenuation nozzles; select nozzles with better noise reduction effects; study the spray noise characteristics and change rules of each nozzle under different aerodynamic pressures and water flow rates; and compare and analyze their dropper particle size, velocity and dust removal efficiency. The mechanism of noise induced by the supersonic flow of compressible fluid, the optimization of the supersonic flow field structure and the noise reduction of porous metal foam nozzles were revealed. The results showed that after the optimization of the supersonic flow field structure, the velocity in the nozzle and the thickness of each velocity layer were reduced so that the corresponding sound pressure level was reduced, the spray noise at the sound source was reduced by approximately 11.6 %, and the propagation direction was reduced by approximately 9.6 %. The rigid pore blocking effect of the microporous metal foam Laval nozzle greatly reduced the radial sound pressure level of the sound source propagating through the nozzle sidewall. Among them, the porous aluminum foam nozzle has the best noise reduction effect, In the direction of propagation, the sound pressure level in the middle and high frequency band is reduced by 16.3 %. With increasing aerodynamic pressure, the sound pressure level at each nozzle sound source and propagation direction increased. With increasing water flow, the sound pressure level of the nozzle at the sound source changed from the original value and then decreased to an upward trend. Under the same working conditions, the size of droplets in the droplet field of each nozzle was approximately 11 mu m. When the dust removal time was 3 min, the dust removal efficiency of each nozzle was above 84 %. While ensuring the dust removal effect of the spray, the noise pressure level of the atomization process is reduced through structural optimization and the principle of porous absorption attenuation, which provides theoretical and technical support for the safe application of the supersonic aerodynamic dust removal spray and the collaborative control of dust and noise.

In coal mine dust control, the efficiency of pneumatic spray technology is limited due to the unclear removal efficiency of different types of droplets on different types of dust, and the unclear dust fog coupling mechanism. This research systematically explores the characteristics of the droplets of the internally mixed pneumatic atomization nozzle and its interaction with the dust through theoretical analysis and experiment. Laser particle size analyzer and particle image velocimeter were used to measure the particle size and velocity field distribution of fog droplets. A gas dust liquid three-phase coupling experimental platform was constructed to capture fog films with specific properties of fog droplet groups for dust fog coupling experiments. The response surface methodology was used to analyze the dust fog coupling effect under different operating conditions. The experimental results show that there is a significant temporal and spatial difference between the droplet velocity and the airflow velocity. The velocity of the aerosol flow field is negatively correlated with the spray distance, and positively correlated with the aerodynamic pressure. The attenuation of the airflow velocity is far greater than that of the droplet. Droplet size is negatively correlated with aerodynamic pressure, and positively correlated with water flow and spray distance. In the coupling effect of dust and mist, dust particles with particle sizes of 0-2.5 mu m and 5-10 mu m are dominated by droplet velocity, while dust particles with particle sizes of 2.5-5 mu m are significantly affected by their own velocity. When the droplet velocity reaches 18-23 m/s, the fog film has a good effect on capturing respiratory dust at different velocities, and the dust reduction efficiency reaches a peak of 86.13 %. The momentum ratio and kinetic energy ratio of fog droplets to dust have a significant nonlinear effect on the removal of 5-50 mu m dust from airborne airflow, with the removal efficiency of 10-50 mu m dust showing a unimodal distribution as the momentum ratio and kinetic energy ratio increase. The results of this study provide data and theoretical support for determining the optimal dust mist coupling matching relationship between different types of droplets and dust under different lateral airflow velocities, and for efficient prevention and control of respiratory dust in coal mines.

To investigate the spray and dust reduction characteristics of internal mixing pneumatic atomizers, experiments were conducted using a self-developed atomization angle and droplet size testing platform, along with a dust-fog coupling experimental platform. The results showed that under pneumatic pressures of 0.2-0.4 MPa and water flow rates of 10-16 L/h, the volume median diameter (V50) and Sauter mean diameter (SMD) of the internal mixing pneumatic atomization droplets decreased with increasing pneumatic pressure and increased with rising water flow rates, with pneumatic pressure having a greater effect. At dust movement speeds of 1-3 m/s and aerosol velocities of 2-5 m/s and 5-11 m/s, the highest dust reduction efficiency occurred at droplet sizes of 4050 mu m and 30-40 mu m, respectively. Setting the aerosol velocity to 8-11 m/s and the dust velocity to 1 m/s, with the droplet size (SMD) evenly distributed between 20- and 40 mu m, resulted in effective coupling and settling with dust particles ranging from 0 to 50 mu m, achieving the highest dust reduction efficiency. This study offers theoretical and experimental support for the use of internal mixing pneumatic atomization in dust control.

In the process of coal mining,a large amount of respirable dust is generated,which seriously endangers the miners'health.As the most widely used dust reduction technology,the spray technology has the advantages of high effi-ciency and cleanliness,but the existing spray technology does not have a strong ability to capture respirable dust,and the atomization efficiency is low.In order to solve those problems,the supersonic coaxial aerodynamic atomization techno-logy was developed.The atomization characteristics of the technology were studied by experimental and numerical simu-lations,and the dust reduction characteristics of supersonic water drawing siphon aerodynamic atomization and superson-ic coaxial atomization were compared based on the self-designed dust reduction experimental platform.At the same time,the dust separation experiment of the two technologies revealed the sedimentation mechanism of dust under the action of supersonic dynamic micro-fog curtain.The results show that under different aerodynamic pressures,the coaxial probe wa-ter injection method adopted by the supersonic coaxial atomization dust reduction device greatly reduces the energy loss of the probe structure on the supersonic flow field,significantly improves the atomization efficiency,and produces a large number of high-speed droplets below 11 μm with an uniform spatial distribution,and the particle size is reduced by 12%-50%compared with the siphon atomization device,forming a large-scale high-speed fine fog area in the spray flow field.The coupling effect of the droplet field and the dust field can be characterized by the instantaneous dispersion of the dust and determined by the distribution characteristics of the droplet field.At different times,the variation trend of the graded dust reduction efficiency in each particle size interval is different,and the contribution to the total dust reduction efficiency under different pressures is also different.The large-scale high-speed fine mist generated by the supersonic coaxial atomization technology is easy to capture respirable dust,and the classification efficiency of PM0-PM2.5 is more than 75%,and the maximum is 90%.The increase of pressure enlarges the range of high-speed fine mist,which is condu-cive to the capture of fine particles.During the confined space migration of dust-containing airflow,the sedimentation pro-cess of dust under the action of supersonic dynamic micro-fog curtain can be divided into droplet dust capture area,con-densation and sedimentation area,and evaporation escape area.The different behaviors and concentration distributions of fog droplets and dust in different regions are the results of the drag migration of spray airflow and airborne wind flow,the capture of high-speed micro-fog collision,the condensation and settlement of fog droplets,and the weight loss of fog droplet evaporation.

The high concentration of respirable dust pollution created during coal mining has long been known to be harmful to employee health. A water absorbing atomization device has certain advantages when spray trapping particle sizes of PM2.5-10. To further improve the PM0-2.5 trapping efficiency, supersonic coaxial pneumatic atomization dust removal technology has been developed. The effects of fog droplet characteristics on the instantaneous diffusion of dust were studied by numerical simulation and macro- and microexperiments for the first time, and the coupling characteristics of fog droplets and dust fields were obtained. The results show that with increasing aerodynamic pressure, the supersonic range extends along the axis toward the nozzle outlet, and the average velocity in the tube increases. Under different pressures, the droplet particle size in the supersonic coaxial atomizing nozzle is <6 mu m and decreases with increasing aerodynamic pressure. When a droplet effuses from the nozzle, the transonic distribution of the flow field causes the droplet velocity to increase first and then decrease under the drag force. The droplet field characteristic distribution of supersonic coaxial atomization is determined by droplet evaporation, condensation, and migration. Under the same pressure, with increasing spray distance, the distribution of the droplet particle size increases in a stepwise manner, and the droplet velocity decreases according to an exponential function so that the droplet field produces a high-speed fine fog area. The range of droplets with higher velocities and smaller particle sizes is mainly influenced by migration and increases with increasing pressure. The coupling effect droplet field and dust field can be characterized by the instantaneous dispersion of dust and are determined by the distribution characteristics of the fog droplet field. The large range of high-speed fine fog produced by supersonic coaxial atomization technology easily traps respirable dust, and the classification efficiency of PM0 -2.5 reaches 90%. In this study, a new dynamic microfog dust trapping technique was proposed, and a new method of instantaneous sampling combined with a microscopic dispersion test was adopted to characterize the temporal and spatial distributions of dust fields affected by fog droplet fields, reveal the generation of dynamic microfog and the mechanism of dust trapping, enrich the theory of fine dust trapping, and provide technical support for the safe production and utilization of coal.

In order to solve the problem of respirable dust pollution in the heading face, a multi-layer spiral spray dust removal method was proposed, in which supersonic pneumatic nozzles were arranged in a spiral shape. Taking the heading face of Qipan Coal Mine as the research object, the three-dimensional numerical model of multi-layer spiral spray dust removal technology device was established by using discrete element and finite element method and k-ω turbulence model and fluid flow particle tracking model in COMSOL software. The velocity field of multi-layer spiral spray air flow, velocity section and trajectory of water mist particles were obtained. The simulation results show that the airflow velocity at the cutting head of the TBM is faster, the farther away from the cutting head, the smaller the airflow velocity, and the airflow near the cutting head is very disorganized; after the nozzle is opened, the water mist particles will form a multi-layer spiral fog curtain, and the spiral fog curtain will cover the entire simulated driving surface after 20 s, and the particle size of the water mist particles is smaller than that of the traditional spray method.

为了解决掘进工作面粉尘污染严重的问题,运用COMSOL软件对某矿 1019 掘进工作面进行了几何模型构建,并基于k-ε湍流模型和流体流动颗粒跟踪模型,计算了在压入式和长压短抽通风方式下的速度切面、风流流线分布以及粉尘粒子的运移轨迹,分析了两种通风方式对粉尘粒子运移的影响,并研究了掘进工作面在两种通风方式下的粉尘运移规律.结果表明:压入式通风方式下,由压风筒将新鲜空气压入巷道内,迫使掘进工作面的粉尘随风流排出巷道,导致掘进机前方区域风流曲线非常密集形成多处涡流导致粉尘粒子在涡流处聚集,同时部分粉尘粒子沉淀在巷道底部,还有部分粉尘粒子沿右侧巷道壁面向后方移动,其控尘效果较差;长压短抽通风方式下,两风筒前方区域速度较大,且压风筒和抽风筒之间风流流线密集;压风筒吹出气流裹挟粉尘粒子移动,同时利用抽风筒的抽吸作用将粉尘粒子吸入排出巷道,与压入式通风方式相比长压短抽的降尘效果更好.