| Coal is a fossil energy source,accounting for about 30%of the world's total primary energy consumption.At present,underground mining is still the main mining method for coal.With the increase of coal mining depth and the improvement of mechanization,the dust and gas disasters in the operating area have become more and more serious,which significantly threatens the safe production of coal mines and the health of workers.The fully-mechanized excavation face is one of the main working places in the coal mine.According to the field measurement,the dust concentration of the fully-mechanized excavation face can reach 1200-1500 mg/m~3 without any dust-proof measures.Even when the dust-proof measures are applied,the operation environment of most fully-mechanized excavation faces is still not optimistic,and the dust concentration at the working location of the roadheader driver can reach up to 900mg/m~3.In addition,gas is generated during the coal production in the fully-mechanized excavation face,which is explosive after reaching a certain concentration.Especially,for the mines with high concentration of gas and the prominent mines,the gas concentration in the working area often exceeds the safety limit.Therefore,proposing a new ventilation method to reduce the dust concentration and dilute the gas concentration has important practical significance for improving the working environment and ensuring the safe production of the fully-mechanized excavation face.In order to address the shortcomings of traditional long-pressure short-exhaust ventilation,in this paper,the wall-mounted swirling ventilation of the fully mechanized excavation face was investigated using both numerical simulation and experimental methods.In addition,based on the actual situation in the field,the parameters of the wall-mounted swirling ventilation were optimized.Based on the field investigation,in this paper,the physical model and mathematical model of the wall-mounted swirling ventilation were established according to the size of the actual roadway.The internal flow field of the physical model was measured by the PIV particle image velocimetry system.The dust diffusion and gas dilution were experimentally investigated.According to the similarity criterion,the experimental model and the numerical simulation model were compared,the validity of the model was verified,and the numerical simulation was used for further investigation.The results showed that the wall-mounted swirling ventilation had little disturbance to the dust generation at the tunneling end and can form the axial and radial air curtains,which can block the dust within the area around the tunneling end and prevent the dust from diffusing to the rear of the roadway.Meanwhile,the wall-mounted swirling ventilation can dilute the gas to some extent.Through the analysis on the influencing factors of the wall-mounted swirling ventilation,the reasonable working conditions of the wall-mounted swirling ventilation,as well as the structural parameters and the installation position of the of the air-mounted duct were obtained.The results showed that the dust control effect was optimal when the forced-exhaust air volume ratio was 1.4.When the dust and gas coexisted in the working face,the reasonable axial and radial air volume ratio was 2:8,at which not only the gas concentration of the fully-mechanized excavation face was controlled within the limit,but also the ideal dust-control effect can be obtained.When the width W and length L of the wall-mounted air duct were 0.05 m and 1.4 m,respectively,and the distance D between the wall-mounted air duct and the tunneling end was 5.6 m,the wall-mounted swirling ventilation had the best dust-control effect.In this condition,the dust concentration at the working location of the roadheader driver was the lowest,and the dust-collection efficiencies for the total dust and the respirable dust were 92.14% and 94.08%,respectively. |
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