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可调空间分辨USEDCARS技术研究

Research on Spatial Resolution Adjustable USEDCARS Technology
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摘要 相干反斯托克斯拉曼散射(CARS)技术是一种非常重要的燃烧诊断技术,该技术具有非常强的抗干扰能力和非常高的测量精度。但空间分辨力不足会使CARS技术产生很强的空间平均效应,引起成CARS光谱畸变,进而造成CARS光谱分析困难,无法通过CARS光谱反演燃烧场参数。针对非稳腔空间增强探测CARS(USEDCARS)技术存在的空间分辨不足以及空间分辨力不易改变的特点,分析了影响USEDCARS技术测量空间分辨力的各种因素,采用一组轴棱锥对USEDCARS系统中的泵浦激光进行环状光束整形,并通过调节轴棱锥之间的距离获得了不同直径的环状光束,在此基础上,建立了空间分辨可调USEDCARS诊断系统。开展了空间分辨力分析实验,获得了CARS信号强度随空间位置的分布数据,以CARS信号总强度95%包含的空间区域代表CARS的纵向空间分辨力,以此计算得到了CARS系统空间分辨力为1.7~6.5 mm连续可调。其中,高分辨力情况,达到了现有BOXCARS技术的空间分辨力。利用所建立的空间分辨可调USEDCARS诊断系统测量了酒精/空气预混火焰温度参数,获得了不同空间分辨条件下的CARS光谱。空间分辨力为1.7 mm时,获得了高质量CARS光谱,通过光谱拟合给出了所测火焰的温度信息。分辨力分别为4.9和6.5 mm时获得了较强的CA RS信号,但存在光谱畸变。结果显示,空间分辨力对CARS信号的强度和空间平均效应有很大地影响,提高测量的空间分辨力可以有效消除空间平均效应,获得准确的CARS光谱,增强光谱拟合精度,同时空间分辨可调的特性使该系统能够更好地适应不同实验条件下的诊断工作。 Coherent anti-Stokes Raman scattering(CARS)is a very important combustion diagnostic technique,for its high accuracy and strong anti-interference ability in combustion field parameter measurement.But when there is a temperature gradient in the detected spatial region,spectra superposition of low and high temperature CARS signal result in spatial average effects which will cause CARS spectral distortion.As a result,it is difficult to analyze the CARS spectrum,and the combustion field parameters cannot be retrieved from the CARS spectrum.In Unstable-resonator Spatially Enhanced Detection CARS(USEDCARS),the lower spatial resolution has limited the application of CARS in flow with a high temperature gradient.Various factors affecting the spatial resolution of the technology were analyzed.The circular beam shaping of the pump laser was carried out by using the axicon group,and ring-shaped pump beam with different diameters was obtained by adjusting the distance between the axicons.Then a USEDCARS diagnostic system with the adjustable spatial resolution was established,and the spatial resolution of the USEDCARS was measur ed,the distribution of CARS signal strength with the spatial position was obtained.Taking spatial region over 95% of the total CARS intensity to represent the longitudinal spatial resolution,the spatial resolution of the system can be adjusted continuously from 1.7 to 6.5 mm.At the highest spatial resolution state,the spatial resolution achieves the level of BOXCARS technology.The temperature of an alcohol/air premixed flame was measured using the established USEDCARS system.Single-pulse CARS spectra with different longitudinal resolutions were obtained.The high-quality CAR spectrum was achieved when the measured spatial resolution was 1.7 mm,and the flame temperature was indicated by the spectral fitting.When the spatial measurement resolution was 4.9 or 6.5 mm,the CARS signal intensity was very strong,but the CARS spectra were distorted.The results show,the spatial resolution has a large impact on the intensity and spatial average effects of CARS signals,the spatial averaging effect can be reduced by improving the spatial resolution,the continuously adjustable spatial resolution enables the USEDCARS system to better adapt to various combustion flow fields.
作者 张振荣 李国华 胡志云 王晟 叶景峰 陶波 邵珺 方波浪 ZHANG Zhen-rong;LI Guo-hua;HU Zhi-yun;WANG Sheng;YE Jing-feng;TAO Bo;SHAO Jun;FANG Bo-lang(Northwest Institute of Nuclear Technology,State Key Laboratory of Laser Interaction With Matter,Xi’an 710024,China)
出处 《光谱学与光谱分析》 SCIE EI CAS CSCD 北大核心 2021年第1期1-4,共4页 Spectroscopy and Spectral Analysis
基金 国家自然科学基金项目(91541203,91641112) 国家重点实验室基金项目(SKLLIM1608)资助。
关键词 相干反斯托克斯拉曼散射 空间分辨力 轴棱锥 环状光束 Coherent anti-Stokes Raman scattering Spatial resolution Axicon Annular beam
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