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General correlations of high pressure turbulent burning velocities with the consideration of Lewis number effect
Proceedings of the Combustion Institute ( IF 3.4 ) Pub Date : 2018-09-19 , DOI: 10.1016/j.proci.2018.08.049
M.T. Nguyen , D.W. Yu , S.S. Shy

This study measures high-pressure turbulent burning velocities (ST) of spherical expanding flames for various liquid and gaseous fuel/air mixtures with different effective Lewis number (Le), i.e. pre-vaporized stoichiometric iso-octane with Le ≈ 1.43 at T = 423 K, hydrogen at the equivalence ratio ϕ= 0.6 with Le ≈ 0.58 at 298 K, and propane at ϕ= 0.7 with Le ≈ 1.62 at 298 K, using the same dual-chamber, fan-stirred cruciform burner capable of generating near-isotropic turbulence. High-speed schlieren imaging is used to obtain the temporal growth of mean flame radii < R(t )> and the observed flame speeds, SF and/or d < R > /dt, where SF is the slope of < R(t )> which equals the average of d < R > /dt within 25 mm ≤ < R(t )> ≤ 45 mm. Using the density correction and Bradley's mean progress variable converting factor for schlieren spherical flames from  = 0.1 to 0.5, ST,c=0.5 ≈ (ρb/ρu)SF(< R > c=0.1/ < R > c=0.5)2, where the subscripts b and u indicate the burned and unburned gas. Results show that Le < 1 flames have much higher ST,c=0.5 than that of Le > 1 flames at any given rms turbulent fluctuating velocities (u′) and pressure (p). We find that these very scattering ST,c=0.5 data with Le < 1 and Le>1 together with previous methane data at 300 K/423 K with Le ≈ 1 can be well represented by three modified general correlations originally proposed by Kobayashi et al. (2005), Chaudhuri et al. (2012), and Shy et al. (2012) when their scaling parameters are rescaling and grouping with Le−1, each representing a single curve with small data scattering. This suggests a possible self-similar propagation for turbulent spherical flames, regardless of different fuels, T, p, u′ used. Discussion and comparison with the Bradley's correlation (1992) are offered and future studies identified.



中文翻译:

考虑路易斯数效应的高压湍流燃烧速度的一般相关性

本研究措施高压湍流燃烧速度(小号Ť球形膨胀火焰),用于与不同的有效路易斯数(各种液体和气体燃料/空气混合物),即,预蒸发的化学计量的异辛烷与乐 ≈1.43在Ť  = 423 K,氢在当量比φ=  0.6与乐 ≈0.58在298 K,和丙烷在φ = 0.7与乐 ≈1.62在298 K,使用能够产生近的相同的双室,风扇搅拌十字形燃烧器各向同性的湍流。高速schlieren成像用于获得平均火焰半径<  Rt )和观察到的火焰速度S F和/或d <  R  > / d t,其中S F是< Rt )>的斜率, 它等于25 mm≤内d < R  > / d t的平均值 <  Rt )>≤45毫米 使用密度校正和Bradley的平均进度变量转换因子对来自 = 0.1〜0.5,小号T,C = 0.5  ≈(ρ b / ρ ù小号˚F(<  - [R  >  C = 0.1 / <  - [R  >  C = 0.52,其中,下标B和U表示燃烧和未燃烧气体。结果表明,在任何给定的rms湍流脉动速度(u')和压力(p)下,Le  <1火焰具有比Le  > 1火焰高的S T,c = 0.5。我们发现这些非常分散的S T,c = 0.5数据与Le <1和>在300 K / 423 K的1个连同先前甲烷数据勒 ≈1可以很好地通过最初由Kobayashi等人提出了三种改性一般的相关性来表示。(2005),Chaudhuri等。(2012)和Shy等人。(2012)当它们的缩放参数被重新缩放并与Le -1分组时,每个参数代表一条具有较小数据分散的曲线。这表明湍流球形火焰可能发生自相似传播,而与所使用的不同燃料(T,p,u')无关。讨论和与布拉德利的相关性(1992年)进行了比较,并确定了未来的研究。

更新日期:2018-09-21
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