Electrical Bond number effects on the instability of charged ethanol micro-jet in electrosprays
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摘要: 基于高速摄像及小尺度PIV技术对无水乙醇荷电微射流雾化模式的演变及射流不稳定性进行了实验研究。精确捕捉了无水乙醇荷电微射流的显微演变过程，探讨了电邦德数影响下不同雾化模式的射流不稳定性演变特征及其对微射流雾化特性的影响规律。实验结果表明：射流的非轴对称性径向扰动贯穿于整个射流雾化模式区间；随着电邦德数不断增大，射流偏离度呈先增大后减小的趋势，而其不确定性的脉动范围在锥射流模式下不断增大，过渡到多股射流模式后，脉动范围逐渐减小至零，而后再逐渐增大；锥射流模式下，射流核心区及速度方向均偏离轴心，射流速度较纺锤模式明显回落；多股射流模式下，射流核心区速度明显回升，但不同电邦德数下多股射流之间的速度分布差异较大；多数情况下，射流边界处的流线较为紊乱，缺乏对称性，但在电邦德数为13.30~13.60的极小区间内保持稳定的多股射流稳定雾化形态，射流核心区速度达到峰值。Abstract: This paper presents an experimental study on the evolution of charged ethanol atomization modes and the instability of the micro-jet. Based on the high-speed microscopy and small scale PIV technology, the microstructure evolution process of the charged ethanol micro-jet was accurately captured, the jet instability evolution characteristics of different atomization models and its influence on atomization characteristics under the effect of the electrical Bond number were discussed. The results show that the jet's non-axisymmetric radial disturbance occurs throughout the jet atomization models. As the electrical Bond number increases, the jet flow deviation increases first and decreases subsequently. The uncertainty fluctuation range gradually increases in the cone jet mode, while it gradually narrows down to zero and increases again in the multi-jet mode. The jet core and its velocity direction of the cone-jet mode all deviate from the axis, and the jet speed significantly declines compared with the spindle mode. The velocity of the jet core obviously rises when the jet transits to the multi-jet mode, while the velocity distribution has many differences at different electrical Bond numbers. The jet boundary streamline shows disorder and lack of symmetry most of the time. However, a stable multi-jet mode with a peak velocity occurs for a very short interval of the electrical Bond number.
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Key words:
- electrosprays /
- jet deflection /
- instability /
- high-speed microscopy
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图 2 不同BoE下无水乙醇荷电微射流雾化形态
Figure 2. Morphology of the micro-jet at different Bond numbers
图 3 不同BoE下无水乙醇微射流偏离轴心的角度变化
Figure 3. Deviation of the micro-jet at different Bond numbers
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