Abstract: Based on a self-developed dense phase pneumatic conveying system, conveying tests of three lignite pulverized coal with different mean particle sizes using N₂ as carrier gas were carried out. The Hurst exponents of pressure drop fluctuation signals in horizontal pipe and mass pulsations of material storage tank were calculated using rescaled range analysis. The standard deviations of mass pulsations were analyzed. The Hurst exponent and standard deviation were used as an indicator of conveying stability. The flow stability of conveying pipe was well characterized by Hurst exponents of pressure drop fluctuation signals (H_dp), while the discharge stability of material tank was not well characterized by Hurst exponents of mass pulsations (H_ma) and standard deviation analysis was required. Conveying stability was investigated according to the ratio of superficial gas velocity to saltation velocity (K). At the left side of K=1.5, H_dp decreased with the decrease of K, the flow regime in gas-solids horizontal conveying pipe was changed and even caused a pipe blockage, the flow stability of conveying pipe became worse. Meanwhile, the standard deviation of mass pulsations increased as K decreased, the discharge stability of material tank deteriorated, and conveying stability became worse. At the right side of K=1.5, as K increased, decreasing trend of H_dp was not obvious, through combined analysis with standard deviation analysis, discharge stability became worse and might cause interruption of discharging.

Key words: dense phase pneumatic conveying, two-phase flow, stability, rescaled range analysis, fractals

摘要： 在自主研发的密相气力输送实验装置上，以N₂作输送载气，以3种不同粒径的褐煤作输送物料进行输送实验，运用域重标分析方法对水平管差压信号和料罐质量脉动序列进行了Hurst指数分析，并采用统计学方法对料罐质量脉动序列进行了标准差分析，从管内流动和料罐出料出发，对整体输送稳定性进行了探讨。结果表明：水平管差压信号Hurst指数H_dp能较好地表征管内流动稳定性，而料罐质量脉动Hurst指数H_ma则需结合标准差分析才能更好地表征料罐出料稳定性。以表观气速与跃移速度比值K为特征参数进行探讨，在K=1.5左侧，随着K值减小，H_dp减小，管内流型发生转变，甚至可能发生堵管，管内流动稳定性变差，料罐质量脉动标准差增大，出料稳定性变差，整体输送稳定性变差；在K=1.5右侧，随着K值增大，H_dp减小趋势不明显，管内流动稳定性虽有变差的趋势，但不会发生堵管，而结合对料罐质量脉动序列的标准差分析，发现出料稳定性变差，甚至可能出现出料中断的情况，整体输送稳定性变差。

关键词: 密相气力输送, 两相流, 稳定性, 域重标分析, 分形