管径及气体性质对爆轰极限的影响实验研究

Experimental Study on the Effect of Tube Diameter and Gas Properties on Detonation Limits

本文在大尺度(D=50.3mm,63.5mm)光滑管道内对四种预混气(2H_(2)+O_(2)+50%Ar,C_(2)H_(2)+2.5O_(2)+70%Ar,C_(2)H_(2)+2.5O_(2)+85%Ar,CH_(4)+2O_(2))进行了爆轰实验研究;获得了爆轰极限Pc和胞格尺寸λ,分析了四种气体的不稳定性,计算了边界层位移厚度δ^(*)和诱导长度Δ_(i),深入研究了管径和气体性质对爆轰极限的影响。实验结果表明:随着初始压力和管径的减小,边界层位移厚度增大,边界效应加强,热损失增多,爆轰临界压力变大;大尺度管道内,不稳定性对极限的影响占据主导,因此极限情况下不稳定气(CH_(4)+2O_(2))符合判据λ=πD,稳定气(2H_(2)+O_(2)+50%Ar,C_(2)H_(2)+2.5O_(2)+70%Ar,C_(2)H_(2)+2.5O_(2)+85%Ar)则不符合;四种预混气的诱导长度均随初始压力增大而减小,2H_(2)+O_(2)+50%Ar和其余三种碳氢燃料混合气的胞格尺寸可分别用λ=52.07Δ_(i)、λ=19.6Δ_(i)预测;边界效应对诱导长度有影响,边界层位移厚度与诱导长度呈正比关系。

In this paper,an experimental study on the detonation of four premixed mixtures(2H_(2)+O_(2)+50%Ar,C_(2)H_(2)+2.5O_(2)+70%Ar,C_(2)H_(2)+2.5O_(2)+85%Ar,CH_(4)+2O_(2))is carried out respectively in large-scale(D=50.3 mm,63.5 mm)smooth tubes.The detonation limits and cell sizes A are obtained,and the instability of four mixtures is analyzed.Moreover,the boundary layer displacement thickness*and induction length;are calculated.Based on these,the effects of tube diameter and gas properties on detonation limit is studied deeply.The experimental results unfold that with the decrease of initial pressure and tube diameter,the boundary layer displacement thickness increases,so the boundary effect and the heat loss increase,ultimately leading the detonation critical pressure increases.In large-scale tubes,the influence of instability on the limit dominates,so in the limit case,the unstable mixture(CH_(4)+2O_(2))meets the criterion λ=πD,the stable mixtures(2H_(2)+O_(2)+50%Ar,C_(2)H_(2)+2.5O_(2)+70%Ar,C_(2)H_(2)+2.5O_(2)+85%Ar)do not.The induction lengths of four mixtures all decrease with the increase of the initial pressure.The cell sizes of 2H_(2)+O_(2)+50%Ar and the other three hydrocarbon fuel mixtures can be predicted throughλ=52.07Δ_(i);andλ=19.62Δ_(i),respectively.Finally,the boundary effect has an influence on the induction length,and the displacement thickness of the boundary layer is proportional to the induction length.