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The effect of jet preheating on turbulence in a premixed jet in hot coflow

机译：射流预热对热混凝土预混射流湍流的影响

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摘要

Moderate or Intense Low oxygen Dilution (MILD) combustion is an important combustion regime, which utilises the combustion of gas in hot and often vitiated environment. MILD combustors are characterised by the use of exhaust gases recirculated into the combustor via dilution or mixing with the incoming fuel or alternately by rapidly mixing an incoming fuel stream into a hot environment of combustion products. However, the influence of preheating the fuel jet is not well understood. Current approaches rely heavily on assumptions about the role of heat on laminarisation of turbulence, due to viscosity. However, the density ratio between jet and environment is known to have a dominant effect on mixing. Velocity measurements are presented for a pair of turbulent premixed flames issuing into a premixed coflow. Two cases are considered, both with and without preheating of the central fuel jet. The resulting near-field velocity is measured using digital Particle Image Velocimetry (PIV). The resulting velocity maps are processed to find the turbulence intensity, u’/U. A two-point correlation technique is used to determine the turbulence integral length scale, lf. The influence of preheating the central jet on the resulting near-field turbulence characteristics are presented and discussed.
机译：中度或强烈的低氧稀释（MILD）燃烧是一种重要的燃烧方式，它利用了在高温且经常通风的环境中燃烧气体的能力。 MILD燃烧器的特点是使用通过稀释或与进料燃料混合而再循环到燃烧器中的废气，或者通过将进料燃料流快速混合到燃烧产物的高温环境中来进行替代。但是，对燃料喷嘴预热的影响尚不十分了解。由于粘性，当前的方法在很大程度上取决于关于热量在湍流层流化中的作用的假设。然而，已知射流与环境之间的密度比对混合起主要作用。给出了针对一对湍流的预混火焰的速度测量结果，该对预混火焰发出了预混同流。考虑了两种情况，包括中央燃料射流的预热和不预热。使用数字粒子图像测速（PIV）测量所得的近场速度。处理所得的速度图，以找到湍流强度u’/ U。两点相关技术用于确定湍流积分长度标度lf。介绍并讨论了对中心射流进行预热对所产生的近场湍流特性的影响。

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    Kalt P.; Dally B.;

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  • 年度 2013
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