含双侧分支受限空间油气爆炸火焰行为与超压特性大涡模拟

Large eddy simulation of gasoline/air mixture explosion in a semi-confined space with bilateral branches

为研究含分支结构狭长受限空间油气爆炸特性规律,基于大涡模拟WALE模型和Zimont预混火焰模型,对横截面为100 mm×100 mm的含双侧分支管道受限空间油气泄压爆炸特性进行了数值模拟。通过对火焰形态、火焰传播速度和动态超压3个物理量的对比,验证了所建立模型对于含分支结构受限空间油气爆炸计算的适用性。基于数值模拟结果,对爆炸过程中的流场结构、火焰形态和超压变化规律进行了分析,指出了"浪花状"火焰的形成原因。结果表明:(1)火焰传播进入分支管道前,在主管道和分支管道交界处会产生旋转方向相反的对称涡旋结构,并随着火焰传播不断向分支管道内部发展;(2)当火焰传播进入分支管道后,分支管道内部前期已建立流场决定了火焰的形态,火焰锋面在涡旋结构作用下呈"浪花状",此后火焰和流场相互影响,流场向湍流转捩,火焰锋面褶皱变形;(3)爆炸超压升压过程可划分为4个阶段,受到火焰锋面面积和分支管道泄压共同作用,表明爆炸流场、火焰行为和动态超压呈现出显著耦合性。

In order to study the gasoline/air mixture explosion characteristics in semi-confined spaces with branched structures,a large eddy simulation model based on WALE turbulence model and the Zimont premixed flame model was established.The explosion characteristics of semi-confined space with bilateral branches ware studied through the simulation.The applicability of the established model for the calculation of gasoline/air mixture explosion in semi-confined spaces with bilateral branches is verified by comparing of flame shape,flame propagation velocity and dynamic overpressure.The flow field,flame behavior and overpressure variation during the explosion process were analyzed through the numerical simulation results and the reasons for the formation of“splash-like”flame were pointed out,and the following results were obtained.(1)Before the flame propagates into the branch pipes,two symmetric vortex structure with opposite rotation directions are generated at the junctions of the main pipe and two branch pipes,and develop toward the inside of the branch pipes as the flame propagates continuously.(2)When the flame propagates into branch pipes,the flow field established in the early stage determines the shape of the flame.The flame front forms a“splash-like”flame under the action of the vortex structure.After that,the flame and the flow field interact with each other turning to the turbulent flow and distorted flame front.(3)The growing process of the overpressure can be divided into four stages,which are influenced by the flame front area and the branch pipe pressure unload,indicating that the explosion flow field,flame behavior and dynamic overpressure have significant coupling effects.