超快千瓦级微波脉冲用于大气压等离子体中二氧化碳转化的增强
Ultrafast Kilowatt-Range Microwave Pulsing for Enhanced CO2 Conversion in Atmospheric-Pressure Plasmas
AI总结：
通过超快微波功率脉冲提升大气压等离子体中二氧化碳转化效率，研究千瓦级微波功率的可扩展性，对比两种反应器配置的转换和能量效率，发现 Surfaguide 型反应器在气体温度上表现更优。
摘要：
超快微波功率脉冲被证明是增强大气压等离子体反应器中二氧化碳转化的有效策略。初始实验在紧凑同轴等离子炬中显示性能提升，本研究探讨该方法扩展到千瓦级微波功率的可行性。转换和能量效率在两种反应器配置中被评估：基于 Surfaguide 的系统（KIT）和基于谐振腔的等离子炬（IPP），并对比紧凑同轴炬。两种千瓦级装置具有相似的微波耦合方案、功率水平、反应管和气体注入几何结构，但差异在于后燃处理。IPP 炬采用快速喷嘴淬火，而 Surfaguide 型反应器依赖于沿延长石英管的较慢冷却。在峰值功率约 4 kW 和脉冲持续时间从亚微秒到微秒的条件下，稳定等离子体操作得以实现，稳定性受限于脉冲间隔时间，分别为约 10 us（谐振腔炬）和 12 us（Surfaguide 型反应器）。与同轴炬相比，两种千瓦级反应器均未观察到等离子体再点燃现象，导致等离子体温度调制较弱。值得注意的是，Surfaguide 型反应器的周期平均气体温度高于连续波操作。在这些条件下，与连续波操作相比，二氧化碳转化相对提升小于 40%，能量效率提升小于 20%。这些改进在 IPP 炬中被大幅抑制，可能是由于快速后燃淬火所致。最后，对瞬时反射微波功率的分析提供了关于功率关断和功率开启阶段电子密度动态的定性见解。
英文摘要：
Ultrafast microwave power pulsation is demonstrated as an effective strategy to enhance CO2 conversion in atmospheric-pressure plasma reactors. While initial experiments at several hundred watts in a compact coaxial plasma torch showed improved performance, the present study investigates the scalability of this approach to kilowatt-range microwave power. Conversion and energy efficiency were examined in two reactor configurations: a Surfaguide-based system (KIT) and a cavity-based plasma torch (IPP), and benchmarked against the compact coaxial torch. Both kilowatt-scale setups share similar microwave coupling schemes, power levels, reactor tubes, and gas injection geometries, but differ in afterglow treatment. The torch at IPP employs rapid nozzle-based quenching, whereas the Surfaguide-based reactor relies on slower cooling along an extended quartz tube. Stable plasma operation was achieved at pulsation peak powers of ~4 kW and pulse durations from sub-microseconds to microseconds, with stability limited to inter-pulse times of ~10 us (cavity-based torch) and ~12 us (Surfaguide-based reactor). In contrast to the coaxial torch, no plasma reignition regime was observed in either kilowatt-scale reactor, resulting in weaker plasma temperature modulation. Notably, the period-averaged gas temperature in the Surfaguide-based reactor exceeded that under continuous-wave operation. Under these conditions, relative enhancements of <40% in CO2 conversion and <20% in energy efficiency were measured compared with continuous-wave operation. These improvements were largely suppressed in the torch at IPP, presumably due to rapid afterglow quenching. Finally, analysis of the instantaneous reflected microwave power provided qualitative insights into electron density dynamics during the power-OFF and power-ON phases.
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