甲烷在空气燃烧的等离子体射流助燃效应的光谱研究  

Spectral Study on Combustion Supporting Effect of Plasma Jet for Methane Combustion in Air

作　　者：张小林[1] 李寿哲 冀春俊[1] 牛裕龙 白阳 廖宏达 ZHANG Xiao-lin;LI Shou-zhe;JI Chun-jun;NIU Yu-long;BAI Yang;LIAO Hong-da(School of Energy and Power Engineering,Dalian University of Technology,Dalian 116024,China;Key Laboratory of Materials Modification by Laser,Ion and Electron Beams Ministry of Education,School of Physics,Dalian University of Technology,Dalian 116024,China)

机构地区：[1]大连理工大学能源与动力学院,辽宁大连116024 [2]大连理工大学物理学院三束材料改性教育部重点实验室,辽宁大连116024

出　　处：《光谱学与光谱分析》2021年第10期3251-3255,共5页Spectroscopy and Spectral Analysis

基　　金：国家自然科学基金项目(11975003)资助。

摘　　要：大气压氩等离子体射流是一种非平衡等离子体,能够产生大量的电子、离子、激发态粒子和活性基团,在燃烧过程中这些粒子的参与能够大大降低化学反应的活化能,而等离子体射流的动力学效应影响粒子输运过程,使得等离子体射流具有一定程度的辅助燃烧效果。本实验通过发射光谱测量,分别识别出了在非预混和预混的甲烷燃烧过程参与燃烧的中间物种(OH,CH和C_(2)),测量了这些自由基的发射光谱强度随着外部控制变量(放电电压、混合当量比)变化的规律。对于非预混情况,实验发现随着产生等离子体射流放电电压的增大,火焰总体长度变短,火焰面出现褶皱,火焰根部蓝色区域面积不断扩大,在22 kV时,大约占总火焰面积的1/2。对火焰根部的发射光谱测量结果表明,当电压达到16 kV时,发射光谱明显增强,而当电压进一步增大到22 kV时,这些自由基粒子的光谱强度却出现下降,这归因于在等离子体产生的电离风作用下管内气体流速增大,导致燃烧区发生移动远离喷口,使采集到的火焰根部区域变小造成的。另外,研究了在不同的燃料当量比下等离子体射流对预混气体助燃的过程,实验发现燃料当量比为2时,OH(A-X)的光谱发射强度随电压的增大而增强而CH(A-X)和C_(2)(d)的发射强度在等离子体射流直接作用的情况下减小,反映了在氩等离子体射流参与助燃下燃烧变得更加充分了。实验发现等离子体射流产生大量的自由基以及等离子体电离风对混合过程的影响能够对燃烧过程产生明显影响。Atmospheric pressure argon plasma jet(APAPJ)is a non-equilibrium plasma producing a large number of electrons,positive ions,excited particles and active groups,which can significantly reduce the activation energy in reactions,and the dynamic effect caused by APAPJ also imposes influence on the transportation process,thereby they both play a very important role in the process of plasma-assisted combustion.In this experiment,By OES,the intermediate radicals(OH,CH and C_(2))generated in the non-premixed and premixed combustions are identified.The variation of emission intensity of those radicals is measured with respect to the fuel equivalent ratio and discharge voltage,respectively.It is found that the application of the APPJ causes the overall length of flame to become short and the flame surface appears wrinkled,with the blue area of the flame root continuously enlarged,which accounts for about 1/2 of the total flame area at discharge voltage of 22 kV,indicating that the combustion becomes complete and intense.When the voltage reaches 16 kV,the spectral intensity of the free radical OH(A-X),CH(A-X)and C_(2)(d)becomes remarkable,but when the voltage is 22 kV,the spectral intensity decreases,which is because the plasma enhances the gas flow rate in the tube,causing the combustion region to move away from the nozzle so that the less intensity is collected by fiber during the spectrum acquisition process.In addition,the combustion process of premixed gas assisted by plasma jet under different fuel equivalence radio is studied.In the case ofΦ=2,it is found that the spectral intensity of OH(A-X)increases with discharge voltage,while those of CH(A-X)and C_(2)(d)decline when the discharge voltage is large enough that the APPJ is merged into flame near the nozzle.It is found that APAPJ plays an importance role in CH 4 combustion in open air due to the active radicals generated in APAPJ and the mixing effect caused by ion wind by APAPJ.

关 键 词：大气压 等离子体射流 助燃 甲烷 发射光谱 

分 类 号：O657.31[理学—分析化学]