Abstract A dielectric barrier discharge plasma controlled diffusion flame experimental system was built based on the designed coaxial swirling plasma injector. The air plasma was generated within the annulus gap of the injector by alternating current dielectric barrier discharge. The discharge characteristics and power of plasma injector under different actuation intensities and air flowrates were measured. Through the measurement techniques, such as schlieren imaging, broadband chemiluminescence image and CH* chemiluminescence, the effect and mechanism of plasma on ethylene-air normal diffusive jet and flame was explored. The results showed that a large number of filamentary discharge channels are formed in air plasma. The increase of air flowrates weakened the intensity of discharge to a certain extent. The induced jet generated by the plasma can short the laminar length of the ethylene-air jet, accelerate the transition of the flow jet, enhance the turbulence and the mixing of the fuel and the oxidizer. The higher the actuation intensity, the shorter distance of the cold jet transition zone, the higher the jet turbulence. Depending on the aerodynamic and kinetic effects, plasma can improve the stability of ethylene-air diffusive flame and reduce the lift height between the flame root and injector. The plasma can also expand the flammability limit of ethylene-air flame and make the flame ignited under some conditions that could not be. In addition, the CH* chemiluminescence shows that, in a certain range of discharge voltage, the heat release distribution can be changed on both sides of the flame, and its representative length are generally reduced as the voltage rises. On the contrary, the overtop voltage could lead to a decrease of flame heat release.

中文翻译：

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交流介质阻挡放电驱动等离子体喷射器对乙烯-空气扩散火焰结构影响的表征

摘要 基于所设计的同轴旋流等离子体喷射器，搭建了介质阻挡放电等离子体控制扩散火焰实验系统。通过交流电介质阻挡放电在喷射器的环形间隙内产生空气等离子体。测量了不同驱动强度和空气流量下等离子体喷射器的放电特性和功率。通过纹影成像、宽带化学发光图像和CH*化学发光等测量技术，探讨了等离子体对乙烯-空气法向扩散射流和火焰的影响及其机理。结果表明，空气等离子体中形成了大量的丝状放电通道。空气流量的增加在一定程度上减弱了放电强度。等离子体产生的诱导射流可以缩短乙烯-空气射流的层流长度，加速流动射流的过渡，增强燃料和氧化剂的湍流和混合。驱动强度越高，冷射流过渡区距离越短，射流湍流越大。取决于空气动力学和动力学效应，等离子体可以提高乙烯-空气扩散火焰的稳定性，降低火焰根部与喷射器之间的提升高度。等离子体还可以扩大乙烯-空气火焰的可燃极限，使火焰在某些不能点燃的条件下被点燃。此外，CH*化学发光表明，在一定的放电电压范围内，火焰两侧的放热分布可以发生变化，其代表长度一般随着电压的升高而减小。相反，过高的电压会导致火焰放热减少。