双层皮带机防雨罩流场和粉尘浓度场分析

上层运煤下层运粉煤灰的双层皮带机比常规单层皮带机高度增加，为了确定双层皮带机防雨罩的最适高度，防止在17 m/s强侧风环境下粉尘泄露污染环境，以气固两相流理论为基础，运用Fluent软件分别在有无强侧风的条件下，对双层皮带机的防雨罩内流场和粉尘浓度场的分布进行数值模拟。计算结果表明，强侧风会强化双层皮带之间形成的流动漩涡，从而可能导致粉煤灰被吹动，当侧风速度为17 m/s时不会导致形成的漩涡强度过大，粉煤灰不会被吹到罩外。有侧风时防雨罩顶部会出现非常高流速（高达55 m/s）的风，在对其进行强度设计时必须考虑由于强风冲击造成的受力。有侧风时防雨罩内粉尘浓度最大位置出现在运煤皮带和煤堆交界处，其次是运粉煤灰皮带和粉煤灰堆交界处，当侧风速度为17 m/s时，防雨罩外部空间的粉尘浓度均小于4×10^-6 kg/m³，满足《煤矿安全规程》的要求。

Flow fields and dust concentration fields of rain shields in double-layer belt conveyors

A double-layer belt conveyor, which conveys coal on the upper belt and ash powder on the lower belt, is placed higher than the conventional singe-layer belt conveyor. To determine the most appropriate height of the rain shield to prevent ash powder from blowing out under strong crosswinds (velocity is 17 m/s), the Fluent software is used to numerically simulate the distribution of the flow fields and the dust concentration fields within the rain shield with or without crosswind based on the theory of gas-solid two-phase flow. The calculation results show that crosswinds strengthen the vortex formed between the double-layer belts and the ash powder may thus be blown out. When the crosswind velocity is 17 m/s, the vortex formed is not too strong and the ash powder will not be blown out of the rain shield. Under crosswind conditions, there is wind blowing with very high velocity(up to 55 m/s) on the top of the rain shield; as such, the stress exerted by the strong winds should be considered in the process of designing the strength of the rain shield. In the presence of crosswinds, the dust concentration in the rain shield is the highest at the junction of the coal conveying belt and coal pile, and is the second highest at the junction of the ash powder conveying belt and ash powder pile. When the crosswind velocity is 17 m/s, the dust concentration outside the rain shield is less than 4×10^-6 kg/m³, which meets the requirements of the Coalmine Safety Regulations.