摘要
本文在现场对比实验和相似模型实验的基础上，采用理论分析与实践相结合的方法，研究了下行通风时沼气涌出和分布的规律、降尘和降温的效果与机理、发生外因火灾时风流的逆转规律以及能够抑制采空区自然发火的原因，并全面分析了下行通风的优缺点和存在问题。提出了下行通风的合理使用条件，得出了下行通风时断面最高沼气浓度比上行通风低、沼气层长度比上行通风短、吹散沼气层所需风速也比上行通风小，而且倾角愈大它们之间的差异也愈大的重要结论。研究结果表明，采面使用下行道风后，煤尘浓度可降低２０～６０％，倾角愈大，降尘效果愈好；在相同火势的情况下下行通风本侧风路比上行通风旁侧风路风流发生逆转时所需的温度低、时间短；下行通风能有效地降低采面温度１～５℃，工作面愈长、走向长度愈长、倾角愈大、原岩温度梯度愈大、机械化程度愈高，其降温的效果也愈好。建议修改《煤矿安全规程》时，取消对下行通风的限制。
Based on site experiments and laboratory model tests for both descensional and ascensionai ventilation,through theoretical analysis together with field investigation, some aspects of descensional ventilation such as, the pattern of methane emission and distribution, the effects and mechanism of dust suppression and cooling,the reversal behaviour of airflow dunng a mine open fire, the restraining effects on spontaneous combus-tion in the gob,etc. ,have been studied in this paper.The merits and demerits, and some re-maining problems of descensional ventilation have also been analysed comprehensively.The proper conditions for the application of it have been proposed.The important conclusions ob-tained include that the maximum methane concentration on a cross section is smaller with descensional ventilation than that with ascenional ventilation,the length of the methane roof layers is slower,the airflow velocity required to dilute the roof layer is lower, and these differ-ences are greater with bigger face slope. It has also been shown that the dust content decreases by 20～60% with descensional ventilation,and this effect is more significant with bigger face slope;under the same intensity of fire the revcrsal of airflow in the fire branch when descensionally ventilated may occur at a lower airflow temperature and in a shorter time than in the adjacent parallel branch when ascensionally ventilated; the face temperature can be de-creased effectively by 1～5℃ with descensional ventilation,and this cooling effect is more sig- nificant with longer face length, longer strike length, greater slope, greater geothermal gra-dient and higher mechaization. When″safty Regulation of Underground Coal Mines″is re- vised, it is suggested that the restriction on dencensional ventilion be canceled.
