A computational study of supersonic combustion in strut injector and hypermixer flow fields
A computational study of supersonic combustion in strut injector and hypermixer flow fields
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DOI：
10.1016/j.proci.2014.06.113
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发表时间：
2015-01-01
影响因子：
3.4
通讯作者：
Sabelnikov, V.
中科院分区：
文献类型：
--
作者：
Fureby, C.;Nordin-Bates, K.;Sabelnikov, V.
在超声速燃烧中实现足够高的燃烧效率和稳定性是极具挑战性的，并且高度依赖于所采用的燃油喷射和混合策略。一种可行的方法是支杆喷射器，它通过诱导流动再循环，促进支杆尾迹中的火焰稳定。在这项研究中，我们详细研究了流动，混合，自燃和火焰稳定机制的常规和交替楔形喷射支柱。为了分析这些问题，我们考虑了NAL的超音速燃烧室，该燃烧室配备了两个传统的两级喷射支柱和一个交替楔形喷射支柱，并与ONERA的腐蚀空气加热器结合使用。实验结果包括羟基（OH）的自发火焰图像、壁面压力图像和平面激光诱导荧光（PLIF）图像，并结合基于有限速率化学大涡模拟（LES）的骨架氢-空气反应机理的计算结果。两种喷油器-支杆类型的自燃火焰图像与预测火焰结构在定性上吻合良好，表明燃烧LES捕捉到了实验的总体特征。壁面压力以及OH-PLIF截面均值和均方根的实验数据与计算结果进行了详细比较，结果一致，表明LES结果可用于进一步研究火焰结构的内在特征和稳定机理。这些结果表明，两级喷射支撑和交替楔形喷射支撑在流动和火焰结构上存在显著差异。更具体地说，由交替楔形喷射支撑引入的纵向涡量提高了燃烧效率，但导致间歇性自燃现象。对于两级喷射支板，燃烧由嵌入在非预混火焰或搅拌反应器背景中的自燃孔包围的自燃前缘组成。相比之下，交替楔形喷射支柱的剧烈燃烧可以通过多模式（自燃、非预混、预混）燃烧过程进行观察。(C) 2014燃烧研究所。Elsevier Inc.出版。版权所有。
Achieving sufficiently high combustion efficiency and stability in supersonic combustion is extremely challenging and highly dependent on the fuel-injection and mixing strategies adopted. A viable approach to this is the strut injector, which by inducing flow recirculation, facilitates flame stabilization in the strut-wake. In this investigation we examine in detail the flow, mixing, self-ignition and flame stabilization mechanisms of conventional and alternating-wedge injection struts. In order to analyze these, we consider NAL's supersonic combustor, equipped with two conventional two-stage injection struts, and an alternating-wedge injection strut, in conjunction with ONERA's vitiation air heater. Experimental results, including spontaneous flame images, wall-pressure and Planar Laser Induced Fluorescence (PLIF) images of hydroxyl (OH) are here combined with computational results based on finite-rate chemistry Large Eddy Simulation (LES) with skeletal hydrogen-air reaction mechanisms. The spontaneous flame images and the predicted flame structures for both injector-strut types agree well qualitatively, demonstrating that combustion LES captures the overall features of the experiments. Detailed comparisons between experimental data and computational results for the wall pressure and for mean and rms OH-PLIF cross-sections show acceptable agreement, indicating that the LES results can be used to further study the intrinsic features of the flame structure and the stabilization mechanism. These results indicate significant differences in flow and flame structures between both two-stage injection struts and the alternating-wedge injection strut tested. More specifically, the longitudinal vorticity introduced by the alternating-wedge injection strut increases the combustion efficiency but results in an intermittent auto-ignition phenomenon. For the two-stage injection struts combustion consists of auto-ignition pockets surrounded by self-igniting fronts embedded in a background of non-premixed flames or stirred reactors. In contrast, the alternating-wedge injection strut vigorous combustion is observed proceeding through a multi-mode (auto-ignition, non-premixed, premixed) combustion event. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.