Experimental Study of Effect on Mach Reflection in Gaseous Detonation
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摘要: 在矩形截面的爆轰管道中, 对C2H2+2.5O2+8.17Ar和C2H2+5N2O在CJ爆轰状态下经过不同楔面所发生的马赫反射的影响因素进行了实验研究。实验中, 由烟膜记录爆轰波马赫反射的胞格结构转变过程; 采用纹影技术捕捉爆轰波马赫反射波阵面的不稳定性及波后流场分布。实验结果表明:两种实验气体在爆轰波马赫反射过程中均存在由CJ区域向过驱区域转变的胞格结构; 初始压力对楔面与马赫反射三波点轨迹线之间的夹角(χ)影响明显, 楔角θw对χ的影响随θw的增大而增大; 根据实验测得的θw+χ与θw之间的关系, 可知爆轰波马赫反射三波点轨迹线的斜率随着θw的增大而增大, 与CJ区域内胞格轨迹线的相交距离也更短, 使马赫杆后的过驱度升高。另外, 不稳定气体C2H2+5N2O的不稳定性高于稳定气体C2H2+2.5O2+8.17Ar, 导致二者的爆轰波马赫反射行为存在较大的差异。Abstract: Mach reflection in C2H2+2.5O2+8.17Ar and C2H2+5N2O over different wedge angles was experimentally investigated in a rectangular channel.In the experiments, the cellular transition structure surrounding wedges was recorded using smoked foils and unstable characteristics of the detonation front were captured using Schlieren setup.The results illustrate that for either a stable or an unstable mixture, there is a transition process of the cellular structure from the CJ zone to the overdriven zone.According to the experimental relationship between θw+χ and θw, the slope of the trajectory of the triple point (χ) formed by the Mach reflection increases with the wedge angle θw, which shortens the intersecting distance with trajectories of the triple points from the CJ zone and elevates the overdriven degree.In addition, the value of χ is significantly affected by the initial pressure and the wedge angle.The instability of C2H2+5N2O is higher than that of C2H2+2.5O2+8.17Ar, which accounts for markedly different behaviours of the Mach reflection that occurred in both mixtures.
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Key words:
- gaseous detonation /
- Mach reflection /
- cellular structure /
- induction zone /
- overdriven degree
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图 2 C2H2+2.5O2+8.17Ar的烟膜实验结果(p0=5kPa)
Figure 2. Soot tracks of C2H2+2.5O2+8.17Ar at p0=5kPa
图 3 C2H2+2.5O2+8.17Ar的纹影图像(p0=5kPa)
Figure 3. Schlieren photographs of C2H2+2.5O2+8.17Ar at p0=5kPa
图 4 C2H2+2.5O2+8.17Ar的烟膜实验结果(p0=10kPa)
Figure 4. Soot tracks of C2H2+2.5O2+8.17Ar at p0=10kPa
图 7 C2H2+2.5O2+8.17Ar的θw+χ与楔角θw的关系
Figure 7. θw+χ vs.wedge angle θw in C2H2+2.5O2+8.17Ar
图 8 不同初始压力下C2H2+2.5O2+8.17Ar的过驱度与楔角的关系
Figure 8. Overdriven degree vs.wedge angle in C2H2+2.5O2+8.17Ar under different initial pressures
图 10 λM/λCJ与MM/MCJ的实验和理论结果对比
Figure 10. Experimental and theoretical results of λM/λCJ and MM/MCJ
表 1 实验设计
Table 1. Experimental design
Mixture Characteristic θw/(°) p0/(kPa) C2H2+2.5O2+8.17Ar
(Highly diluted by argon)Stable 10, 20, 30, 35, 40 3, 5, 10, 20 C2H2+5N2O Unstable 20, 30, 35, 40 3, 5, 10, 20 
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表 2 混合气体爆轰参数的计算结果
Table 2. Detonation parameters computed for mixture
Mixture p0/(kPa) DCJ/(km/s) ΔI/(mm) TvN/(K) pvN/(MPa) C2H2+2.5O2+8.17Ar 5 1.714 9 0.322 2 163.7 0.18 C2H2+5N2O 3 2.103 4 0.823 1 890.6 0.21
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