A joint schlieren imaging, pressure recording and tunable diode laser absorption spectroscopy (TDLAS) thermometry technique was developed to simultaneously determine the flame radius, pressure and line-of-sight averaged temperature of spherically expanding flames of n-butane/air mixtures at initial temperature of 298 K, initial pressure of 1 atm and equivalence ratios of 0.9–1.5. To probe the flame temperature, a mid-infrared interband cascade laser at 4.2 µm was used to measure the time-resolved direct absorption spectra of CO₂ which are strongly related to flame temperature, CO₂ mole fraction, flame radius and pressure. Quantitative line-of-sight averaged temperatures of burnt gas were obtained by fitting the normalized absorbance spectra. Three typical stages, including the spark affected initial stage, quasi-steady stage and the pressure induced growing stage are determined from the evolution of measured temperature as a function of time and flame radius. The relation between flame temperature, stretch rate and burning velocity of burnt gas are analyzed. Stretch rate is found to have minor effect on the measured temperature in the quasi-steady stage. The relative variation of temperature is much smaller than that of velocity. The flame with lower normalized temperature tends to propagate slower.

开发了一种联合席勒成像，压力记录和可调二极管激光吸收光谱（TDLAS）测温技术，可同时确定初始温度下正丁烷/空气混合物的球形膨胀火焰的火焰半径，压力和视线平均温度298 K，初始压力为1个大气压，当量比为0.9-1.5。为了探测火焰温度，使用了4.2 µm的中红外带间级联激光器来测量时间分辨的CO ₂直接吸收光谱，该光谱与火焰温度CO ₂密切相关摩尔分数，火焰半径和压力。通过拟合归一化​​吸收光谱获得定量的视线平均燃烧气体温度。根据被测温度随时间和火焰半径的变化确定三个典型阶段，包括受火花影响的初始阶段，准稳态阶段和压力诱导的生长阶段。分析了火焰温度，拉伸速率和燃烧气体燃烧速度之间的关系。发现在准稳态阶段，拉伸速率对测得的温度影响很小。温度的相对变化远小于速度的变化。归一化温度较低的火焰倾向于传播较慢。