滑动弧等离子体拓宽双模态冲压燃烧室点火边界的探索研究

Extending the low Mach number start-up boundary of the dual-mode ramjet combustor to less than 3Ma is of great significance for the development of 0-6Ma turbine-ramjet combined engine. At 3Ma, the total temperature and pressure of incoming flow are 600K and 0.23MPa, respectively. The evaporation rate and chemical reaction rate of kerosene atomization decrease significantly, which leads to ignition difficulty. It is urgent to develop innovative ways to broaden ignition boundary. On the basis of the research results of the previous cultivation project, a new idea of self-entraining multi-channel plasma ignition is proposed. A self-entraining channel is set up from the upstream of the combustion chamber to the bottom of the cavity, kerosene is injected into the channel, and a sliding arc plasma is applied to excite the outlet of the channel. The high power sliding arc plasma ignition is connected with low power sliding arc plasma ignition. It is expected that the ignition boundary of the dual-mode ramjet combustor with low Mach number will be extended. The basic data and parameters of high/low power sliding arc plasma ignition/combustion-supporting were obtained through comprehensive measurement and theoretical analysis of discharge energy, pyrolysis components and evolution process of ignition nucleus. The mechanism of self-ignition sliding arc plasma ignition and combustion-supporting under high speed, low total temperature and low total pressure was revealed. The results of the project will provide support for breakthroughs in the scientific issues of "Controllable Combustion Mechanism under Extreme Conditions" in major research projects and innovations in combined engine combustors.

拓宽双模态冲压燃烧室的低马赫数启动边界到3Ma以下，对于0-6Ma涡轮-冲压组合动力的发展具有重要意义。3Ma时来流总温总压分别为600K和0.23MPa，煤油雾化蒸发速率和化学反应速率显著降低导致点火困难，亟待发展创新的点火边界拓宽途径。本项目在前一个培育项目研究成果的基础上，提出自引气多通道滑动弧等离子体点火助燃的新思路，从燃烧室凹腔上游到凹腔底部设置自引气通道，在通道内喷入煤油，在通道出口施加滑动弧等离子体激励，通过高功率滑动弧等离子体点火与低功率滑动弧等离子体助燃的接续作用，有望拓展双模态冲压燃烧室低马赫数点火边界。通过放电能量、裂解组分、火核演化过程等综合测试与理论分析，获得高/低功率滑动弧等离子体点火/助燃的基础数据与变化规律，揭示高速低总温低总压条件下滑动弧等离子体点火助燃机理。项目成果将为重大研究计划“极端条件下可控燃烧机制”科学问题的突破和组合动力燃烧室的创新提供支撑。

本项目面向拓展双模态冲压燃烧室低马赫数点火边界的重大需求，开展了高速低总温低总压条件下滑动弧等离子体点火助燃的实验研究和理论分析，研制了自引气多通道滑动弧等离子体激励器，验证了高功率滑动弧等离子体点火的技术可行性，获得了拓宽点火边界的新方法。研制的滑动弧等离子体激励器实现了燃油的雾化、蒸发、裂解、点火功能集成，通过放电与预燃裂解的耦合，释放煤油的化学能，将点火释放的能量从传统电点火的十焦耳量级提升至百或千焦耳量级。分析了多通道滑动弧等离子体点火与助燃特性，获得了不同通道及布局条件下滑动弧等离子体点火助燃效果的变化规律与主要影响因素。煤油裂解产物主要为氢气、甲烷、乙烯、乙炔，以及其他微量C3以下烃类物质，能够显著提高超燃冲压燃烧室的燃烧强度和火焰稳定性，验证了滑动弧激励器的助燃效果。利用燃气组分分析法计算了不同工况下燃烧室燃烧效率。煤油流量为7.5g/s时，燃烧效率提高了7.83%。煤油流量大于9g/s时，单激励器点火后火焰无法稳定燃烧，双激励器可以维持火焰稳定燃烧。并对高速低总温低总压条件下自引气多通道滑动弧等离子体点火助燃机理进行了初步探索。.项目研究成果显著提高了超燃冲压燃烧室低总温进口条件下的点火与燃烧性能，研制的新型滑动弧等离子体激励器体积较热射流点火器显著缩小，既具有热射流的热效应又可产生煤油裂解的活性产物，与传统电点火器尺寸基本相当且无需使用先锋氢引导，相比烟火点火器具有可重复使用及提升稳定燃烧性及燃烧效率的显著优势，为未来拓展超燃发动机点火下边界研究提供了创新思路。

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