为了研究索特平均直径(D3,2)对煤粉及其在瓦斯气氛中爆炸特性的影响，利用20-L球形爆炸装置，测量了煤粉初始样和混合样及其在瓦斯气氛中的爆炸特性参数，研究了粒径分散度σD对煤尘爆炸威力的影响，对比分析了粒径特征参数D50，D4,3，D3,2值与煤粉粉尘爆炸威力的相关性;同时收集了煤粉粉尘爆炸的固体残渣，并通过扫描电镜对其微观结构进行了表征;最后，结合煤粉粉尘爆炸实验数据和产物微观结构分析结果，探讨了煤粉粉尘及其在瓦斯气氛中爆炸的机理。实验结果表明:当D50值相同时，σD值最大(2.31)时煤粉粉尘的压力最大值Pmax和(dP/dt)max值较σD值最小(1.49)时分别增加了14.71%和68.05%，说明煤粉粉尘的粒径分散度σD会显著影响其爆炸性能;相对于D50值和D4,3值，D3,2值可以更好的阐述煤粉粉尘的爆炸特性，D3,2值最大(120 μm)时的粉尘爆炸压力Pex和(dP/dt)ex值较D3,2值最小(2.5 μm)时分别降低了33.33%和83.33%，说明D3,2值对(dP/dt)ex值的影响大于对Pex值的影响;在瓦斯气氛中，随着D3,2值的增加，煤粉粉尘的(dP/dt)ex值逐渐减小，低瓦斯体积分数时，D3,2值对Pex值影响较小，但高瓦斯浓度时，D3,2值越大则Pex值越小，而煤粉颗粒的D3,2值越小，挥发分燃烧速率更快，爆炸更剧烈，其残渣表面的孔洞越多,破碎程度也越大。

In order to study the influence of mean diameter (D3,2) on the explosibility of coal dust with and without methane gas,20 L spherical vessel is used to measure the explosive characteristics parameters,the influence of particle size dispersion σD on the explosion power of coal dust is studied,and the correlations between the values of D50,D4,3 and D3,2 and the explosibility coal dust are analyzed,the solid residues of coal dust explosion is collected and characterized by a scanning electron microscope inally,the mechanism of coal dust explosion with and without methane gas is discussed on basis of dust explosion experimental results and the microstructure analysis results of the explosion solid products.The experimental results show that Pmax and (dP/dt) max values of coal dust with the maximum σD (2.31) increase by 14.71% and 68.05% respectively compared to those with the minimum σD(1.49),which shows that particle size dispersion  σD  of coal dust can significantly affect its explosion performance ompared with D50 and D4,3 values,D3,2 can better illustrate the explosion characteristics of coal dust.Pex and (dP/dt)ex values of coal dust with the maximum D3,2(120 μm) increase by 33.33% and 83.33% respectively compared to those with the minimum D3,2 (2.5 μm),therefore,the influence of D3,2 on (dP/dt)ex are higher than that of Pex n the methane gas atmosphere,with the increase of D3,2,the (dP/dt)ex value of coal dust explosion decreases gradually.When the methane gas concentration low,D3,2 had little influence on Pex values,but when the methane gas concentration high,larger D3,2 result in smaller Pex  values.Smaller D3,2 of coal particles led to faster combustion rate of coal particles and higher explosibility,and the residues of coal dust has greater breakage and more holes in their surfaces.The results illustrate the importance of σD and D3,2 values on evaluating the explosion hazard characterization of coal dust or combustible dust,which is of great significance to the prevention of gas and dust explosion in coal mines.