Abstract The development of high-speed volumetric laser-induced fluorescence measurements of formaldehyde ( $$\hbox {CH}_2\hbox {O}$$ CH 2 O -LIF) using a pulse-burst laser operated at a repetition rate of $${100} \hbox { kHz}$$ 100 kHz is presented. A novel laser scanning system employing an acousto-optic deflector (AOD) enables quasi-4D $$\hbox {CH}_2\hbox {O}$$ CH 2 O -LIF imaging at a scan frequency of $${10}\hbox { kHz}$$ 10 kHz . The diagnostic capability of time-resolved volumetric imaging is demonstrated in a partially premixed DME/air lifted turbulent jet flame near the flame base. Simultaneous imaging of laser beam profiles is performed to account for the laser pulse energy fluctuation and laser sheet inhomogeneity. With the accurate registration of laser sheet positions, the volumetric reconstruction of $$\hbox {CH}_2\hbox {O}$$ CH 2 O -LIF signals is performed within a detection volume of $$17.3 \times 11.9 \times {2.3}\, \hbox { mm}^3$$ 17.3 × 11.9 × 2.3 mm 3 with an average out-of-plane spatial resolution of $${250}\,\upmu \hbox {m}$$ 250 μ m . A surface detection algorithm with adaptive thresholding is used to determine the global maximum intensity gradient by calculating gradient percentiles. The flame topology characteristics are investigated by evaluating the 3D curvatures of $$\hbox {CH}_2\hbox {O}$$ CH 2 O surfaces. Curvatures calculated using 2D data systematically underestimate the full 3D curvature due to the lack of out-of-plane information. The inner surfaces near the turbulent fuel jet exhibit higher probabilities of large mean curvature than the outer surfaces. The saddle and cylindrical structures are dominant on both the inner and outer surfaces and the elliptic structures occur with lower probability. The results suggest that the damping of turbulent fluctuations by the temperature increase through the $$\hbox {CH}_2\hbox {O}$$ CH 2 O region reduces the curvature, but the local structure topology remains self-similar. Graphic abstract

中文翻译：

---

使用声光偏转器对提升的湍流喷射火焰中的甲醛进行高速体积成像

摘要 使用重复频率为 $ 的脉冲脉冲激光对甲醛 ($$\hbox {CH}_2\hbox {O}$$ CH 2 O -LIF) 进行高速体积激光诱导荧光测量的发展${100} \hbox { kHz}$$ 100 kHz。一种采用声光偏转器 (AOD) 的新型激光扫描系统可实现准 4D $$\hbox {CH}_2\hbox {O}$$ CH 2 O -LIF 成像，扫描频率为 $${10}\ hbox { kHz}$$ 10 kHz 。时间分辨体积成像的诊断能力在火焰底部附近部分预混合的 DME/空气提升湍流喷射火焰中得到证明。执行激光光束轮廓的同时成像以解决激光脉冲能量波动和激光片不均匀性。通过激光片位置的准确配准，$$\hbox {CH}_2\hbox {O}$$ CH 2 O -LIF 信号的体积重建在 $$17.3 \times 11.9 \times {2.3}\, \hbox { mm}^ 的检测体积内进行3$$ 17.3 × 11.9 × 2.3 mm 3 具有$${250}\,\upmu \hbox {m}$$ 250 μ m 的平均面外空间分辨率。具有自适应阈值的表面检测算法用于通过计算梯度百分位数来确定全局最大强度梯度。通过评估 $$\hbox {CH}_2\hbox {O}$$ CH 2 O 表面的 3D 曲率来研究火焰拓扑特征。由于缺乏平面外信息，使用 2D 数据计算的曲率系统地低估了完整的 3D 曲率。湍流燃料射流附近的内表面比外表面具有更高的平均曲率概率。内表面和外表面均以鞍形和圆柱形结构为主，椭圆形结构出现的概率较低。结果表明，通过$$\hbox {CH}_2\hbox {O}$$ CH 2 O 区域的温度升高对湍流波动的阻尼降低了曲率，但局部结构拓扑保持自相似。图形摘要