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首页> 外文期刊>Combustion and Flame >Effects of electrode spark gap, differential diffusion, and turbulent dissipation on two distinct phenomena: Turbulent facilitated ignition versus minimum ignition energy transition
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Effects of electrode spark gap, differential diffusion, and turbulent dissipation on two distinct phenomena: Turbulent facilitated ignition versus minimum ignition energy transition

机译：电极火花隙，差分扩散和湍流耗散对两个不同现象的影响：湍流促进点火与最小点火能量转变

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This paper reports laminar and turbulent minimum ignition energies (MIEL and MIET) of hydrogen/air mixtures at two equivalence ratios (phi= 0.18 and 5.1) where Lewis numbers Le approximate to 0.3 and 2.3, respectively, over wide ranges of the electrode spark gap (d(gap) = 0.3-6.5 mm) and the r.m.s. turbulent fluctuating velocity (u' = 0-8.3 m/s). Depending on the coupling effects of Le, d(gap), and u', we explain what causes two distinct phenomena: Turbulent Facilitated Ignition (TFI) meaning MIEL MIET and MIE Transition meaning a change from MIET = MIEL to MIET MIEL when u' is greater than some critical value. High-speed Schlieren imaging shows that the embryonic spark kernel in quiescence is ball (rod) like when d(gap) 1 mm (d(gap) 1 mm), demonstrating large (very small or negligible) positive curvature. This explains why TFI, an unusual phenomenon, only occurs at sufficiently small d(gap) 1 mm and at sufficiently large Le approximate to 1 because large positive curvature stretch weakens reaction rate due to differential diffusion, making successful ignition in quiescence very difficult to achieve. At d(gap) = 0.58 mm and Le approximate to 2.3, a non-monotonic decrease and increase of MIE T with increasing u' is observed, because the dissipation of ignition kernel by sufficiently intense turbulence re-declares its dominance leading to the increase of MIET. There is no TFI when d(gap) 1 mm regardless of Le. The scenario changes to MIE transition when d(gap) = 2 mm at Le approximate to 2.3, where MIEL MIET. Moreover, when Le approximate to 0.3, MIE transition is shown to appear at d(gap) = 0.3 mm, but is clearly suppressed at d(gap) = 0.58 mm beyond which successful ignition is very easy to achieve. These findings are important for spark ignition in premixed turbulent combustion. (C) 2019 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
机译：本文以两个等效的比率（PHI = 0.18和5.1）报道了层状和湍流最小点火能（Miel和Miet），其中Lewis Numbume Le近似于0.3和2.3，在电极火花间隙的宽范围内（D（间隙）= 0.3-6.5 mm）和RMS湍流波动速度（U'= 0-8.3 M / s）。取决于Le，D（间隙）和U'的耦合效果，我们解释了两个不同现象的原因：湍流促进点火（TFI）意味着Miel Mie和Mie转换意味着Miet> = Miel到Miet> >当U'大于一些临界值时Miel。高速Schlieren成像表明，静态的胚胎火花内核是球（杆），如D（间隙）<1mm（D（间隙）> 1 mm），展示大（非常小或可忽略的）正曲率。这解释了为什么TFI，一种不寻常的现象，仅在足够小的D（间隙）<1mm处并且足够大的Le大致发生到1，因为大曲率拉伸由于差分扩散而削弱反应速率，使得静态中的成功点火非常难以达到。在D（间隙）= 0.58mm且Le近似为2.3时，观察到不动的下调和MIE T的增加随着U'的增加，因为点火核通过足够强烈的湍流来重新宣布其优势导致增加米特。无论LE如何，当D（间隙）> 1 mm时没有TFI。当D（间隙）= 2 mm在Le近似为2.3时，方案更改为mie转换，其中Miel Miet。此外，当Le近似为0.3时，MIE转换显示在D（间隙）= 0.3mm处出现，但在D（间隙）= 0.58mm之后，在成功的点火上非常易于实现，显然是抑制的。这些发现对于先发化的湍流燃烧中的火花点火很重要。 （c）2019燃烧研究所。由elsevier Inc.出版的所有权利保留。

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