摘要
激光诊断技术是燃烧温度场无干扰在线测量的主要手段,开发精确的燃烧场温度测量技术对于研究燃烧基础问题具有重要意义.目前,基于激光的燃烧场测温技术大多以纳秒激光作为光源,基于飞秒激光的测温技术相对较少.本文开发了一种基于飞秒激光成丝的燃烧场温度测量方法.飞秒激光在光学介质中传播时,会形成一条具有一维长度且强度均匀分布的光丝,由于光丝内的功率密度极高,足以通过光解和激光诱导光化学反应等方式将原子/分子激发到高能级,进而向低能级跃迁时释放荧光.通过相机收集荧光信号即可获得光丝的空间长度,光丝的长度与光学介质的温度密切相关,将光丝置于已知温度的燃烧场中,可获得不同温度下的光丝长度,结合理论推导,对实验数据进行拟合,可获得光丝长度与温度的定量关系,进而实现燃烧场温度的测量.
Laser-based diagnostic techniques are critical nonintrusive methods of measuring the in-situ temperature in combustion flow fields.Developing temperature measurement techniques with high accuracy and precision is of great significance for studying the combustion.At present,nanosecond(ns)lasers are commonly used in these methods.However,the researches based on femtosecond(fs)lasers are relatively few.Here,we develop a thermometry technique for combustion fields based on fs laser-induced filament.When the fs laser propagates in an optical medium,a long uniformly distributed plasma channel(also named filament)will be generated.The clamped intensity inside the filament is high enough to generate excited atoms/molecules through fs laserinduced photochemical reactions.Subsequently,the excited atoms/molecules release fluorescence signals.The length of the filament can be measured by imaging the fluorescence signal with an ICCD camera,which is evaluated by the full width at half maximum(FWHM)of the spatial distribution of the filament emission signal.Based on theoretical analysis,the experimental data of the filament length are fitted with a power function,and the result is satisfactory compared with the R-squared measure of goodness(R2)of 0.984.This indicates that the filament length is correlated well with the temperature of the combustion field.A monotonic quantitative relationship between the filament length and the temperature can be established by a calibration process,and then the temperature of the combustion field can be measured.When the temperature changes from 1630 to 2007 K,the length of the filament shortens by 38%.This indicates that the filament length is sensitive to the temperature of the flow field.When the temperature is 2007 K,the absolute uncertainty of the measurement is±25 K,and the relative uncertainly is about 1.2%.The spatial resolution of the measurement system is 50μm,which was determined by a USAF 1951 Target.Based on the spatial resolution,the measurement precision can arrive at 17 K.Alth
作者
李帅瑶
张大源
高强
李博
何勇
王智化
Li Shuai-Yao;Zhang Da-Yuan;Gao Qiang;Li Bo;He Yong;Wang Zhi-Hua(State Key Laboratory of Engines,Tianjin University,Tianjin 300072,China;State Key Laboratory of Clean Energy Utilization,Zhejiang University,Hangzhou 310027,China)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2020年第23期139-145,共7页
Acta Physica Sinica
基金
国家自然科学基金(批准号:51806149,91741205)
浙江大学能源清洁利用国家重点实验室开放基金(批准号:ZJUCEU2019011)资助的课题.
关键词
飞秒激光
成丝
温度
femtosecond laser
filamentation
temperature
