• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Plasma-assisted combustion in a supersonic flow.
【24h】

Plasma-assisted combustion in a supersonic flow.

机译：超音速流中的等离子体辅助燃烧。

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

In this study, a nanosecond pulsed plasma discharge is used to ignite jet flames (hydrogen and ethylene) in supersonic crossflows. The nonequilibrium plasma is produced by repetitive pulses of 15 kV peak voltage, 20 ns pulse width and 50 kHz repetition rate. Sonic or subsonic fuel jets are injected into an air or a pure oxygen supersonic free stream flow of Mach numbers Ma 1.7 to Ma 3.0. The flow pattern and shockwaves, induced by the fuel jets and flow disturbances originating from the surface geometric alterations of the test model are characterized by Schlieren imaging. Planar laser induced fluorescence and emission spectroscopy are employed for imaging the distribution of OH radicals depicting fuel/oxidizer reaction regions.;Two geometric configurations of the test model are utilized with the application of the pulsed plasma, which are a cavity model and a flat wall model. The cavity provides a recirculation region where cavity flames are ignited and sustained. The cavity flame is found to be enhanced by the application of the pulsed plasma in the cavity. An investigation of the time evolution of the cavity flame reveals that the flame enhancement is primarily caused by the reduction of ignition delay time by the plasma. In the flat wall model experiment, the fuel injection nozzles and electrodes are mounted flush with the surface of a flat wall, oriented to be parallel to the flow to minimize stagnation pressure losses associated with generated shockwaves. A configuration combining an upstream subsonic oblique jet and a downstream sonic transverse jet is shown to provide an adequate flow condition for jet flame ignition. The OH fluorescence images of the region in the vicinity of the discharge confirms jet flame ignition by the plasma. Similar trends are observed in both of hydrogen and ethylene fuel injection experiments with the two test models.;The experimental results with the hydrogen fuel jets are validated using a numerical approach. The pulsed plasma is modeled as a radical source providing radicals to a flammable gas mixture periodically. The reactions following the radical production are simulated by a MATLAB based code, Cantera. The reduction of the ignition delay and the jet flame ignition by the plasma on the flat wall are successfully validated by the method. In addition, the effects of the plasma operation conditions (e.g., plasma power and frequency) are investigated. The results suggest that higher plasma power further reduces the ignition delay time and the radical production by the pulsed plasma of a fixed power varies inversely or proportionally with the plasma frequency depending on the initial temperature of gas mixture.
机译：在这项研究中，纳秒脉冲等离子体放电用于点燃超声速横流中的喷射火焰（氢和乙烯）。非平衡等离子体是由15 kV峰值电压，20 ns脉冲宽度和50 kHz重复频率的重复脉冲产生的。音速或亚音速喷气燃料被注入空气或马赫数Ma 1.7至Ma 3.0的纯氧超音速自由流中。通过Schlieren成像来表征燃料喷射流引起的流动模式和冲击波以及源自测试模型表面几何变化的流动扰动。平面激光诱导的荧光和发射光谱用于成像描绘燃料/氧化剂反应区域的OH自由基的分布。;在脉冲等离子体的作用下，使用了测试模型的两种几何结构，即空腔模型和平坦壁模型。空腔提供了再循环区域，在该区域中点燃并维持了空腔火焰。发现通过在空腔中施加脉冲等离子体可以增强空腔火焰。对腔内火焰时间演变的研究表明，火焰增强主要是由于等离子体减少了点火延迟时间。在平壁模型实验中，燃料喷嘴和电极与平壁的表面齐平安装，并定向为与流动平行，以最大程度减少与产生的冲击波相关的停滞压力损失。示出了组合上游亚音速倾斜射流和下游音速横向射流的构造，以提供用于射流火焰点火的适当流动条件。放电附近区域的OH荧光图像证实了等离子体的喷射火焰点火。使用这两种测试模型在氢气和乙烯燃料喷射实验中都观察到了类似的趋势。氢燃料射流的实验结果通过数值方法得到了验证。脉冲等离子体被建模为自由基源，可周期性地向可燃气体混合物提供自由基。自由基产生后的反应由基于MATLAB的代码Cantera模拟。通过该方法成功地验证了等离子体在平坦壁上的点火延迟的减小和喷射火焰的点火。另外，研究了等离子体操作条件（例如，等离子体功率和频率）的影响。结果表明，较高的等离子功率可进一步减少点火延迟时间，并且固定气体的脉冲等离子体产生的自由基产生量取决于气体混合物的初始温度，与等离子体频率成反比或成比例地变化。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号