Breakup of a kerosene droplet at high Weber numbers
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摘要: 为了探究高韦伯数下气流速度及液滴初始直径对液滴破碎以及Rayleigh-Taylor不稳定波的影响，进行了煤油单液滴在气流中破碎的实验，采用高速摄影技术记录了液滴的破碎过程，应用包含粘性和表面张力的Rayleigh-Taylor不稳定性理论分析了液滴的破碎过程，对Rayleigh-Taylor不稳定波波长与液滴破碎时间进行了理论计算，并与实验结果做了对比研究。结果表明：当We为321左右时，煤油液滴开始呈现灾型破碎模式；气流速度、液滴初始直径对液滴表面的最大增长率Rayleigh-Taylor不稳定波的波长、增长率和临界波长均有影响；Rayleigh-Taylor不稳定性理论在预测最不稳定波长时，结论与实验结果的误差不超过6%；取经验参数M为8.9时，液滴破碎时间理论与实验误差最小。
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关键词:
- 煤油液滴 /
- 二次雾化 /
- 高韦伯数 /
- Rayleigh-Taylor不稳定性 /
- 破碎时间
Abstract: In order to study the influence of the airstream velocity and droplet initial diameter on the secondary atomization process and the Rayleigh-Taylor wave, the experiment of recording the breakup process of a kerosene droplet at high Weber numbers was conducted, where the photographs were taken by a high speed camera.The analysis based on the Rayleigh-Taylor instability theory which includes viscosity and surface tension was done. The calculation was conducted in order to predict the wavelength of the most unstable Rayleigh-Taylor wave and breakup time, and the results were compared with the experimental data. The results indicate that the catastrophic breakup takes place when the Weber number is greater than 321. The airstream velocity and droplet initial diameter have great influence on the wavelength of the Rayleigh-Taylor wave with the maximum growth rate, the growth rate and the critical wavelength. The Rayleigh-Taylor instability theory which contains the viscosity and surface tension fits the experimental data well when being used to predict the wavelength of the most unstable Rayleigh-Taylor wave, the error less than 6%. Setting the value of M to be 8.9 can minimize the breakup time error. -
图 5 不同液滴初始直径下的k-n图(ug =68m/s)
Figure 5. n vs. k with different initial diameters (ug =68m/s)
图 7 理论波长与实验结果的对比
Figure 7. Comparison of wavelength between theory results and experimental data
图 9 理论破碎时间与实验结果的对比
Figure 9. Comparison of breakup time between theory results and experimental data
表 1 煤油和空气的物性参数
Table 1. Properties of kerosene and air
Material ρ/(kg·m-3) μ/(Pa·s) σ/(N·m-1) Kerosene 780 0.0024 0.00263 Air 1.29 0.00018 
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表 2 实验工况
Table 2. Experimental conditions
Case ug/(m·s-1) T/K d0/mm We 1 53 275 2.23 307 2 53 275 2.33 321 3 53 274 2.55 351 4 60 276 2.23 394 5 60 275 2.33 411 6 60 274 2.55 450 7 68 275 2.23 506 8 68 275 2.33 529 9 68 276 2.55 578
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