高风速下沙粒跃移跃距的实验研究

跃距是颗粒运动的重要参数之一,沙粒跃距的实验研究对沙粒跃移理论研究有重要的参考意义.由于高风速下沙粒跃移轨迹平缓,飞行距离较长,因而,高风速下沙粒跃距的实验研究很少.通过对沙粒跃移特点进行分析,提出同时采用水平集沙仪和垂直集沙仪观测沙粒跃距的方法,并采用该方法对高风速下沙粒跃距进行野外观测研究.结果表明,沙粒跃距随粒径减小呈指数规律增大,沙粒粒径与运动方式转换趋势与前人研究结果基本一致,说明该方法测量沙粒跃距是可行的.     

A new phenomenological model of gas explosion based on characteristics of flame surface

This paper presents a new model of explosion propagation in a closed vessel. The foundation of the formulation is a sub-model of turbulent burning velocity based on the assumption that the burning velocity of a turbulent wrinkled flame can be determined from the flame surface. In addition, model development includes simple sub-models of heat transfer and free convection. In order to verify the physics, the model was utilized to simulate the explosion of a methane–air mixture in two different test vessels. The results obtained by use of this new model were compared with results obtained by use of the classical model. While the simulations showed that both are accurate, the new model presented in this paper (called “flame surface model” for simplicity) is more flexible and can easily accommodate sub-models of different phenomena that can play an important role in fuel–air explosions.     

The effect of orifice plates with different shapes on explosion propagation of premixed methane–air in a semi-confined pipeline

The effect of internal shape of obstacles on the deflagration of premixed methane–air (concentration of 10%) was experimentally investigated in a semi-confined steel pipeline (with a square cross section size of 80 mm × 80 mm and 4 m long). The obstacles used in this study were circular, square, triangular and gear-shaped (4-teeth, 6-teeth and 8-teeth) orifice plates with a blockage ratio of 75%, and the perimeter of the orifice was regarded as a criterion for determining the sharpness of the orifice plate. The overpressure history, flame intensity histories, flame front propagation speed, maximum flame intensity and peak explosion overpressure were analyzed. The explosion in the pipeline can be divided into two stages: initial explosion and secondary explosion. The secondary explosion is caused by recoiled flame. The perimeter is positively related to the intensity of the recoiled flame and the ability of orifice plate to suppress the explosion propagation. In addition, the increase in the perimeter will cause the acceleration of the flame passing through the orifice plate, while after the perimeter of the orifice reaches a certain value, the effect of the increase in perimeter on explosion excitation becomes no obvious. The overpressure (static pressure) downstream of the orifice plate is the result of the combined effect of explosion intensity and turbulence. The increase in perimeter leads to the increase in turbulence downstream of the orifice plate which in turn causes more explosion pressure to be converted into dynamic pressure.     

塔里木盆地气溶胶粒度分布研究

使用Series 210收集了塔里木盆地内6个不同地点的气溶胶,获取了该地区气溶胶的粒度分布,并计算了对应的气溶胶数量中位直径。研究发现:在自然情况下,气溶胶分布遵循双峰分布的规律,其中第一峰值通常出现在0.5μm附近,第二峰值出现在3μm附近;由于采样点的气象条件、地表情况等差异所致,不同采样地点的峰位和峰面积有一定的差异;各采样点气溶胶分布规律显示,绝大多数气溶胶粒子粒径小于1μm。自然条件下,大多数采样点气溶胶粒子数量中位直径小于1μm。     

气溶胶在不同倾角裂隙中穿透率研究

为研究气溶胶在自然界不同倾角岩体裂隙中的穿透率,对理想模型进行了理论分析计算,并在实验室用钢板制做模拟裂隙置于不同角度进行实验。结果表明:实测值与修正后的理论计算值吻合较好,对于有一定倾角的规则尺寸岩体裂隙可以通过修正后的理论计算公式得到气溶胶在其中的穿透率;随着水平倾角的交替改变(-90°~90°),气溶胶穿透率呈现周期性变化,随着相对角度(0°~90°,0°~-90°)的增加,气溶胶穿透率明显上升,且大粒径粒子尤为明显,小粒径粒子受角度影响较小;随着侧面倾角增大(0°~90°),气溶胶粒子穿透率逐渐上升(尤其是大粒径气溶胶粒子);裂隙呈水平状态时,气溶胶在其中的穿透率最低。裂隙倾角变化,对小粒径气溶胶粒子穿透率影响不大,对大粒径气溶胶粒子穿透率影响较为明显。     

Experimental study on the quenching process of methane/air deflagration flame with porous media

This article reports experimental investigation of deflagration flame quenching behavior by porous media. In this study, a semi-vented deflagration chamber with a porous media plate was constructed, taking account of effects of obstacles and porous media materials on the flame quenching process. A high speed video camera was used to image the process and behavior of flame propagation, meanwhile, the gas-phase temperatures and ion currents, upstream, within, and downstream of the porous media, were measured using micro-thermocouples and ion probes, respectively. Results show that methane/air deflagration flame can be quenched by the Al₂O₃ porous media with thickness of 20 mm and pore density of 10 ppi. However, the presence of obstacles along the flame path may lead to significant increase of flame speed, thereby both the decreases of gas-phase temperature and ion current when the flame passes through the porous medium in the case with continuous obstacles are less, eventually the unburnt gases downstream the porous media may be reignited. Compared to Al₂O₃, Al porous media shows superior flame quenching performance because this metallic material has higher thermal conductivity, which makes combusting flame release more heat to the pore walls and adjoining structures of the porous media.     

Pu在粉质粘土介质中的分配系数及其影响因素研究

本文以粉质粘土介质为研究对象,用批式法实验研究了Pu在砂土介质中的分配系数及其影响因素。研究结果表明：核素Pu在粉质粘土中的分配系数较大,反映该种地质介质对Pu具有较强的吸附阻滞性;另外,分配系数是一个随环境pH值、介质含水率及水中核素源项浓度而变化的量。     

戈壁地表风沙运动特征的野外观测研究

通过野外观测实验探讨了戈壁地表风沙运动的若干特征。结果表明:戈壁地表风沙活动层主要集中在距地表60 cm高度内;不同粒径沙粒输沙强度的垂向分布不同,以0.25~0.5mm为过渡区,0.25mm颗粒输沙强度随高度增大先增加而后按指数规律递减,0.5mm颗粒则随高度增加呈线性递减,且粒径越大,递减的梯度越小;风沙流中颗粒的粒度组成不仅受风速和颗粒起动风速影响,而且还与地表粒度组成直接相关;输沙率与风速之间关系服从指数规律,公式形式为q=α.eβ.u,其中α、β为相关系数,u为地面2m高处风速。     

Influences of coal dust components on the explosibility of hybrid mixtures of methane and coal dust

In order to study the influences of coal dust components on the explosibility of hybrid mixture of methane and coal dust, four kinds of coal dust with different components were selected in this study. Using the standard 20 L sphere, the maximum explosion pressure, explosion index and lower explosion limits of methane/coal dust mixtures were measured. The results show that the addition of methane to different kinds of coal dust can all clearly increase their maximum explosion pressure and explosion index and decrease their minimum explosion concentration. However, the increase in the maximum explosion pressure and explosion index is more significant for coal dust with lower volatile content, while the decrease in the minimum explosion concentration is more significant for coal dust with higher volatile content. It is concluded that the influence of methane on the explosion severity is more pronounced for coal dust with lower volatile content, but on ignition sensitivity it is more pronounced for coal dust with higher volatile content. Bartknecht model for predicting the lower explosion limits of methane/coal dust mixture has better applicability than Le Chatelier model and Jiang model. Especially, it is more suitable for hybrid mixtures of methane and high volatile coal dust.     

压实膨润土的土水特性试验研究

回填材料是高放废物地质处置库多重屏障系统的重要组成部分,以蒙脱石为主要成分的膨润土是较理想的回填材料,研究膨润土的非饱和渗透特性,对于回填材料选材和处置库安全性评价具有重要意义。文章通过室内试验开展柯尔碱膨润土的土水特性研究,用压力膜仪实测不同干密度柯尔碱膨润土的土水特征曲线,根据柔性壁渗透仪测得的饱和导水率数据,采用Van Genuchten(1980)预测模型分别计算得到每种干密度膨润土在不同含水量及基质吸力条件下的非饱和导水率,建立了非饱和导水率与含水量、基质吸力的相关关系,对比分析干密度对曲线的影响。结果表明,干密度对柯尔碱膨润土的土水特征曲线有着明显的影响,在初始含水量相同的情况下,干密度较大的膨润土脱水速率比干密度较小的膨润土脱水速率慢,表现出较高的持水性能。柯尔碱膨润土的非饱和导水率随含水量减小和基质吸力增大皆呈非线性降低,干密度越小,非饱和导水率越大。