变截面管道结构对H2/Air预混气体燃爆特性的影响研究

实际工业中,管道截面突变可改变预混燃气火焰的燃烧模式和燃爆特性,影响燃气输送的安全性。为此,利用Fluent软件,数值模拟研究了4种变截面管道结构(突变扩张型管道、突变收缩型管道、渐变扩张型管道和连续突变扩张型管道)对H_2/Air预混气体燃爆过程火焰动态变化的影响,并分析了管内温度场、压力场的分布情况、气体流速和涡量等燃爆特征参数以及焓、熵值等热力学参数的变化规律。研究结果表明:扩张型管截面的突扩诱导作用和收缩型管截面的收缩阻挡作用改变了管内预混气体燃烧火焰传播的动态结构以及火焰前锋的稀松波和预混气流方向,使火焰出现了"杯口"型和"长颈花瓶"型前锋面;突变收缩型管截面的阻挡、反射和抑制作用加强了湍流强度和涡流运动强度,管内最高温度、峰值压力和平均流速等燃爆特征参数也相对较高,而涡团向上、下管壁的运动抑制了火焰尖端的反应强度和传播速度;渐变扩张型管道能降低突扩诱导作用的影响;而连续突变扩张型管内发生在层流向湍流火焰转变阶段的首次截面突扩产生的诱导作用对其燃爆特性的影响更为显著。

Influence of Variable Cross-section Pipe Structure on Deflagration Characteristics of H2/Air Premixed Gas

In industrial applications,the mutation of pipe section can change the combustion model and deflagration characteristic of premixed gas, which would affect its transportation safety.Influence of four kinds variable cross-section pipeline structures(mutational expansive pipe,mutational concretive pipe,gradually expansive pipe and continuous muta-tion expansive pipe)on the flame dynamic change in the combustion process of H2/Air premixed gas was numerically simu-lated by Software Fluent.Distribution of temperature field and stress field,and change law of combustion characteristic pa-rameters of premixed gas such as flow velocity and vorticity were also analyzed.Results show that induction functions of mu-tational expansive and blocking functions of mutational concretive in variable cross-section pipelines change dynamic struc-ture of premixed flame propagation and the heading direction of poor ware in front of premixed flame and premixed airflow, generating"cup"type and"long neck vase"type flame fronts.Blocking, reflection and inhibiting effects of mutational concretive pipe strengthened the turbulence intensity and eddy current intensity,and brought deflagration parameters,such as the highest temperature,peak pressure and average flow velocity,to higher level.However,the motion of vortex to up-per or lower wall inhibits the reaction strength and propagating speed of the flame tip.Gradually expansive pipe can reduce the influence of induction functions of mutational expansive.Influence of induction functions caused by the first mutational cross-section,in the process of lamina to turbulence,is more significant in the continuous mutation expansive pipe.