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Computational and experimental investigation of ignition in a Mach 2 cavity-based flameholder

机译：马赫2腔剥落器中点火的计算与实验研究

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摘要

The ignition and flame propagation in an ethylene fueled Mach 2 supersonic cavity are investigated experimentally and computationally. A laser spark is placed in the base of the cavity and the combustion process is tracked using broadband chemiluminescence. Computationally, hybrid Reynolds-averaged Navier-Stokes/large eddy simulation combined with a 22 species chemistry mechanism is used to simulate the ignition process. The simulation is used to explain the underlying physics and flow features leading to the chemiluminescence intensity profile observed experimentally. Initially, the flame kernel spreads in the spanwise direction to fill the region near the cavity & rsquo;s aft-facing step before moving axially downstream to ignite the entire cavity. The flame causes an increase in pressure, restricting fuel flow from the injectors, subsequently leading to leaner conditions that reduce overall heat release. Heat release reduction lowers the pressure and allows the fuel to flow back into the cavity as the flame adjusts to its steady state configuration. At steady state, the elemental fuel concentration within the cavity is significantly higher compared to the non-reacting condition. Examining the ignition time-scales, it is found that the increase in elemental fuel concentration lags approximately 2 milliseconds behind the increase in pressure as the recirculation and diffusion in the cavity transports the additional fuel into the domain. In addition to the full-width simulation, a partial-width simulation that is 1/6 the size of the experimental domain with periodic boundaries is evaluated as a potential cost-saving option. Due to the decreased domain size, the time scales related to ignition were shortened versus the full width simulation which showed consistent time scales with the experimental findings. The partial-width simulation, however, was able to capture the major stages of combustion during the ignition process.Published by Elsevier Masson SAS.
机译：在实验和计算上研究了乙烯燃料马赫2超声腔中的点火和火焰繁殖。将激光火花放置在腔的基部中，使用宽带化学发光跟踪燃烧过程。计算地，混合雷诺平均水平的Navier-Stokes /大型涡旋模拟与22种化学机构相结合，用于模拟点火过程。该模拟用于解释导致实验观察到化学发光强度曲线的底层物理和流动特征。最初，火焰内核在翼展方向上扩散以填充腔室附近的区域，然后轴向轴向沿轴向下游移动以点燃整个腔。火焰导致压力的增加，限制来自喷射器的燃料流动，随后导致减少整体热释放的稀释条件。随着火焰调节到其稳态配置，热释放减少降低压力并允许燃料将燃料流回腔体。在稳态，与非反应条件相比，腔内的元素燃料浓度明显高得多。检查点火时间尺度，发现元素燃料浓度的增加在压力的增加后滞后约为2毫秒，因为腔内的再循环和扩散将额外的燃料输送到域中。除了全宽度模拟之外，偏宽模拟为1/6，具有周期性边界的实验域的大小被评估为潜在的成本节省选项。由于域尺寸下降，与点火有关的时间尺度与全宽度模拟缩短了与实验结果一致的时间尺度。然而，部分宽度模拟能够在点火过程中捕获燃烧的主要阶段。由elestvier Masson SAS发布。

著录项

  • 来源
    《Aerospace science and technology》 |2021年第8期|106756.1-106756.8|共8页
  • 作者

    Hassan Ez; Ombrello Timothy M.; Peterson David M.;

  • 作者单位

    US Air Force Res Lab Wright Patterson AFB OH 45433 USA|1950 Fifth St Wright Patterson AFB OH 45433 USA;

    US Air Force Res Lab Wright Patterson AFB OH 45433 USA;

    US Air Force Res Lab Wright Patterson AFB OH 45433 USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Laser ignition; Scramjet; LES;

    机译：激光点火;Scramjet;

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