Abstract In this work, we achieve a sub-breakdown electric field measurement in a premixed stagnation flame by electric-field-induced second-harmonic generation (ESHG) using a nanosecond laser. Under the application of a DC voltage, the premixed flame can transit from a flat substrate-stabilized mode to a conical nozzle-stabilized mode due to the two-way interaction between the electric and hydrodynamic responses of the flame. The average electric fields along the laser pathway for these two flame modes are measured at different heights above the burner. Combining the measurement and the numerical simulation of a charge transport model, we further elucidate that the flame affects the electric field distribution in two different ways. For the flat flame mode, the electric field strength is shielded at the flame front and then quickly increases both upstream and downstream, reaching the maximum at the electrodes. The charge transport model reveals that the electrostatic shielding effect of the flame front can be attributed to the charge redistribution in the chemi-ionized conductive layer. For the conical flame mode, the electric field strength has a large gradient near the conical tip and remains almost zero downstream. The conical flame front then serves as a conductive layer to guide the charge transport under the application of the electric field. The positive and negative charges are separated at different radial positions because of the inclined asymmetric flame front. Thus, the largest electric field gradient is generated upstream of the flame conical tip, where the net charge and the electric body force maximize and create a virtual flame stabilization mode.

中文翻译：

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直流电源下预混滞止火焰电场分布的实验与数值研究

摘要 在这项工作中，我们通过使用纳秒激光器的电场诱导二次谐波 (ESHG) 实现了预混停滞火焰中的亚击穿电场测量。在施加直流电压下，由于火焰的电和流体动力学响应之间的双向相互作用，预混火焰可以从平坦的基底稳定模式转变为锥形喷嘴稳定模式。这两种火焰模式沿激光路径的平均电场是在燃烧器上方的不同高度测量的。结合电荷传输模型的测量和数值模拟，我们进一步阐明了火焰以两种不同的方式影响电场分布。对于平焰模式，电场强度在火焰前沿被屏蔽，然后在上游和下游迅速增加，在电极处达到最大值。电荷传输模型表明，火焰前沿的静电屏蔽效应可归因于化学电离导电层中的电荷重新分布。对于锥形火焰模式，电场强度在锥形尖端附近具有很大的梯度，并且在下游几乎保持为零。然后，锥形火焰前沿用作导电层，以在施加电场的情况下引导电荷传输。由于倾斜的不对称火焰前沿，正负电荷在不同的径向位置分开。因此，在火焰锥形尖端的上游产生最大的电场梯度，