| The fully mechanized working face was the working space which produced a large amount of mine dust in fully mechanized working face, and the dust concentration exceeded the standard dozens of times when the shearer cut coal, seriously threatening the health and safety of miners. Therefore, the dust control in fully mechanized working face became one of the problems in current coal mine safety work.The paper made a research on dust migration law by the methods of theory analysis, field measurement and numerical simulation, when the shearer cut coal in fully mechanized working face, concluding that the airflow was the main factor affecting dust migration. Swirling eddies were created because of shearer’s obstruction to airflow and the variation of cross section areas of the working face, causing that the cutting dust was carried to the pavement by air flow. Therefore, the paper creatively proposed a scheme of applying the double air curtains to improve airflow distribution in fully mechanized working face, and the curtains limited swirling eddies to the areas between the air curtains and the coal wall to prevent the cutting dust from diffusing to the pavement. Hybrid grids method was applied to complete the meshing of geometric model of the fully mechanized working face, and numerical simulation method was applied to contrast the dust isolation performance of single air curatin with that of double air curtains, and finally the paper determined the optimal performance of double air curtains. Conclusions as follows: switching on single air curtain, the airflow at working face was separated to the sides, but low velocity areas was created in the jet under the effects of airflow in the working face, causing that the cutting dust diffused to the pavement through the low velocity areas; switching on double air curtains, the curtain close to the coal wall could supply part of air entrainment by the curtain away from the coal wall to weaken the ability of entraining cutting dust, and it could also strengthen the swirling eddies which could prevent the inhaled dust from fleeing from the eddies; it indicated that when the outlet velocity of the curtain close to the coal wall was identical with or slightly greater than that of the curtain away from the coal wall on condition that the outlet velocity both was greater than 3m/s, and the length of the curtain away from the coal wall was at least 1.2m longer than that of the curtain close to the coal wall, the dust-isolation performance was better.Double air curtains managed to make the cutting dust limited to the areas between the curtains and the coal wall, in which the paper assembled a spray system which would produce a droplets curtain to increase the abilities of droplets to capture the cutting dust and then to increase the spray dust efficiency. Numerical simulation method was applied to study the atomization quality of the spay system with the double air curtains operating. The paper studied the influence of parameters variation on atomization effect with an operating curtains group in which the length of double air curtains was 3.8m and 2.6m respectively and the outlet velocity both was 5m/s. Conclusions as follows: the double air curtains limited atomized droplets to the areas between the curtains and the coal wall, increasing the droplets number density; larger nozzle diameter made the atomized droplets bigger, and enlarged the droplets distribution areas; the higher spray pressure made the atomized droplets smaller, and made the droplets velocity higher, but weakened barrier effect of the double curtains instead; higher spray angle made atomized droplets distribution more uniform, but made the droplets velocity lower; to the fixed mass flow of water, it made limited influence on the droplets parameters by varying nozzle diameter, spray pressure and spray angle. After analyzing the simulation results, the spray parameters matching the double air curtains was presented. |
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