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Effects of surrounding pressure on cone–jet formation in electrospray process
Microfluidics and Nanofluidics ( IF 2.8 ) Pub Date : 2021-01-20 , DOI: 10.1007/s10404-020-02405-8
H. Dastourani , M. R. Jahannama , A. Eslami-Majd

A numerical approach has been employed to investigate the role of surrounding gas pressure in the electrospray cone–jet status as the most desired and practical mode in various applications. The simulations carried out based on heptane as the working liquid and air as the surrounding gas, over an extent of absolute pressures lying in 10 kPa to 1000 kPa for the liquid flow rate 6.2 mLh−1 and the electric potential 4 kV. The simulating cases fall in the range of dimensionless numbers 82.2 < \({\text{Re}}_{j}\) < 112.3, 17.3 < \({\text{We}}_{j}\) < 44.0, 0.2 < \({\text{Ca}}_{j}\) < 0.4 and \({\chi }_{j}\) < 4 × 10–4, confirming the formation of a stable cone–jet pattern in compliance with the convective instability limits. Despite the preservation of cone–jet geometry, the results clarify that the surrounding pressure could obviously contribute a dual effect through the length and surface undulations of the jet owing to change in the drag force. The jet tip disintegration into droplets remarkably demonstrates a transition from a prolate to an oblate mode at the upper bound pressures. The surrounding medium also influences flow pattern within the cone zone by means of contracting and relocating vortices further downstream as the pressure rises up. The droplet mean size shows 7.9% variation all over the pressure extent, however, the droplet number size appears to earn more weight as the size spectrum broadens while the surrounding pressure increases.



中文翻译:

周围压力对电喷雾过程中锥形射流形成的影响

一种数值方法已被用来研究周围气压在电喷雾锥喷状态下的作用,这是各种应用中最需要和最实用的模式。在液体流速为6.2 mLh -1和电势为4 kV的情况下,以庚烷为工作液体,空气为周围气体,在10 kPa至1000 kPa的绝对压力范围内进行了模拟。模拟情况属于无量纲数82.2 <  \({\ text {Re}} _ {j} \)  <112.3,17.3 <  \({\ text {We}} _ {j} \)  <44.0, 0.2 <  \({\ text {Ca}} _ {j} \)  <0.4和\({\ chi} _ {j} \)  <4×10 –4,证实了根据对流不稳定性极限形成的稳定的锥喷模式。尽管保留了圆锥射流的几何形状,但结果表明,由于阻力的变化,周围压力显然可以通过射流的长度和表面起伏起双重作用。射流尖端崩解成液滴,表明在上限压力下从扁长模转变为扁模。当压力上升时,周围介质还会通过收缩和重新定位涡流而影响锥区内的流型。液滴平均尺寸在整个压力范围内均显示7.9%的变化,但是,随着周围环境压力增加,尺寸谱变宽,液滴数尺寸似乎会获得更多的重量。

更新日期:2021-01-20
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