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受限空间内可燃预混气体燃爆规律数值模拟研究

作者:优质期刊论文发表网  来源:www.yzqkw.com  发布时间:2019/10/31 9:34:40  

摘要:近几年能源产业不断发展,碳氢可燃性气体广泛使用,因燃气泄漏导致火灾和爆炸的事故层出不穷,严重威胁着工业生产、交通运输和物资储运的安全。基于可燃气体燃烧爆炸事故的巨大危害性,探究爆炸火焰在管道内的发展规律也成为了一项亟待解决的课题。

本文通过数值模拟手段,利用流体力学软件Fluent,应用雷诺平均(RANS)方程和基于C方程的Zimont模型计算非稳态燃烧过程,采用PISO算法,对无障碍物管道内丙烷-空气预混气体燃爆过程进行数值模拟,求解火焰传播速度、爆炸压力,通过与实验结果、理论模型的对照,验证了该模型的可靠性。

本文首先对密闭管道内爆燃过程进行数值模拟研究,分析管道长度、管道直径对火焰结构变化、火焰传播速度、爆炸压力的影响规律。研究结果显示,增加管长,火焰传播速度有所提高,但不同管长条件下最终达到的峰值压力基本一致;管径对于火焰传播特性是非常重要的参数,“郁金香”火焰出现的位置随管径的增大而延后,不同管道直径下的火焰速度变化趋势有明显差异,最大火焰传播速度与管径大小呈正比。

对置障密闭管道内预混气体燃烧过程进行数值仿真,分析障碍物阻塞率、障碍物间距、障碍物空间位置对密闭管道内丙烷-空气爆炸火焰加速的效果。本文工况中,火焰传播速度随阻塞率的增大呈先增大后减小的趋势,阻塞率为0.7时的火焰传播速率最高,但阻塞率不影响峰值压力的大小,只对压力上升速率产生影响;阻塞率在0.5~0.7时,障碍物间距才影响火焰的加速效果,其中障碍物间距为一倍管径时火焰加速效应最大;而障碍物的空间位置对火焰传播的影响更为显著,当障碍物位于管道单侧时,湍流涡强度最大,火焰褶皱最明显,火焰传播速度最快。

对末端开口管道内可燃气体燃爆特性进行研究,针对管道长度、管道直径、障碍物阻塞率等影响因素进行分析。研究发现,末端开口、闭口管道内“郁金香”火焰形成机制不同,火焰在管道内自加速机制也不同,末端开口工况下,管长对火焰传播速度的影响程度明显大于末端闭口工况;对于开口管道,管径较大时难以形成“郁金香”火焰,且不同管径条件下,火焰传播速度变化趋势基本一致,火焰传播速度均在管道末端达到峰值。随着障碍物阻塞率的增大,最大火焰传播速度呈先增大后减小的趋势,在阻塞率为0.7时达到峰值,而爆炸压力与阻塞率呈正比关系。

In recent years, the energy industry hasbeen developing continuously, and the hydrocarbon and flammable gases arewidely used. Due to gas leakage, fire and explosion accidents emerge in anendless stream, which seriously threaten the safety of industrial production,transportation and material storage and transportation. Based on the greatharmfulness of flammable gas combustion and explosion accidents, it hasattracted more and more attention to its safety. It has revealed that thedevelopment of flammable gas flame in the pipeline has become an urgentproblem.

In this paper, by means of numericalsimulation, using fluid mechanics software Fluent. Using the Reynoldsaveraged(RANS) equation and Zimont model based on C equation to calculate theunsteady combustion process. The PISO algorithm is applied to simulate thecombustion process of propane-air premixed gas in an empty pipe withoutobstacles, the velocity of flame propagation and the explosion pressure aresolved. The reliability of the model is verified by the comparison with theexperimental results and the theoretical model.

The numerical simulation of deflagration ina closed pipe is carried out in this paper firstly. The influence of pipelength and pipe diameter on flame structure change, flame propagation speed andexplosion pressure is analyzed. The research results show that, increasing thelength of pipe has improved the flame propagation velocity, but slowed down therate of pressure rising. However, the peak pressure under the condition ofdifferent length to reach consistant. The diameter is an important parameter forthe change of flame structure, the tulip flame occurs delayed with the increaseof diameter. When the pipe diameter increases to a certain extent, the typicaltulip flame structure is not observed. The variation trend of flame velocityunder different pipe diameters is obviously different, and the maximum velocityof flame propagation is proportional to the size of the pipe diameter.

The combustion process of premixed gas inthe barrier pipeline is numerically simulated, and the effect of obstaclesblocking ratio, obstacle spacing and spatial position of the obstacles on flameacceleration of propane-air explosion flame in closed pipelines is analyzed.The results under the working condition of this paper show that the flamepropagation velocity increases and then decreases with the increase of blockingratio. The flame propagation rate is the highest when the blocking rate is 0.7.However, the blocking ratio doesn’t affect the peak pressure, and only affectsthe rate of pressure rising. When the blocking ratio is at 0.5~0.7, theobstacle spacing affects the flame acceleration action. In addition,theinfluence of the spatial position of the obstacles on the flame propagation wasmore significant. The most rapid flame propagation was observed when the obstacleswas located on the unilateral side of the pipe,the turbulence vortex intensityin the flow field was the largest, the flame folding was also the most obviouswith the process of chemical reaction.

The combustion and explosioncharacteristics of combustible gas in in a semi-closed pipe are studied, andthe factors such as the length of pipe, the diameter of pipe, and the blockingratio of the obstacles are analyzed. The study found that, the mechanism oftulip flame formation and flame auto acceleration in the closed and semi-closedpipe are different. Under the condition of semi-closed pipe, the influencedegree of pipe length on flame propagation velocity is obviously greater thanthat of closed pipe. For semi-closed pipe, the tulip flame is difficult to formwhen the pipe diameter is large, and the flame propagation velocity isbasically the same under different diameter conditions, the flame propagationvelocity reaches the peak value at the end of pipeline. With the increase ofobstacles blocking ratio, the maximum flame propagation velocity increase firstand then decre

关键词:数值模拟;预混气体;火焰加速;火焰结构;爆炸压力

numerical simulation; premixed gas; flameacceleration; flame structure; explosion pressure

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