强自发光高速侵蚀模拟环境粒子速度场测量

Measurement of particle velocity fields in a strong self-luminous high-speed erosion simulation environment

  • 摘要: 以电弧加热器为代表的粒子侵蚀模拟环境具有速度高、温度高、自发光强度大的特点,粒子速度场测量难度增加。针对高速飞行器头部/发动机喉道侵蚀环境模拟中粒子速度场的测量需求,本文通过引入窄带滤光片实现粒子散射光的滤波光谱分离,大幅抑制由电弧加热器高温气流产生的自发光干扰,由此获得高速运动条件下的高信噪比粒子图像,进而发展建立了高温强自发光流动粒子速度测量技术。基于该技术,在总温范围为21503570 K条件下,对平均名义粒径分别为20、50 μm的Al2O3粒子和石墨粒子开展了粒子速度场测量。结果表明:对于同种粒子材料,总焓提升可以有效提升侵蚀粒子的出口速度分布,其中Al2O3粒子在215027703570 K条件下的出口平均速度峰值分别为130214211527 m/s;对比分析发现,石墨粒子虽然具有较大直径,但因其密度较低,出口平均速度峰值可达1539 m/s;侵蚀粒子射流出口速度流向平均值沿径向(x方向)的分布近似正态分布;由于电弧加热器出口流场为自由大气环境,侵蚀模拟射流存在明显的低速剪切边界,剪切边界跨度最小为35.5 mm、最大为45 mm。通过系统对比不同来流条件下出口粒子速度分布和涡量分布,本文揭示了射流边界特性,为粒子侵蚀试验的精细化评估提供了数据支撑。

     

    Abstract: Due to ultra-high flow speed, extreme total temperature and intense self-luminescence of typical particle erosion environments such as in the arc heater, it is difficult to measure the particle velocity field accurately. To address the measurement requirements of particle velocity fields in ‌hypersonic vehicle nose‌ and ‌engine throat erosion, ‌this paper developed a particle image velocimetry (PIV) technique based on high-temperature and strong self-luminescence particles. A narrowband filter was used to achieve spectral separation of particle scattered light, greatly suppressing the self-luminescence generated by the high-temperature airflow of the arc heater, thus images with high signal-to-noise ratio were obtained under high-speed flow. ‌Implementing this technique‌, PIV measurements were conducted on Al2O3 particles (the average particle size of 20 μm) and graphite particles (the average particle size of 50 μm) ‌across‌ total temperature ranges of 2150–3570 K. ‌The results revealed that‌: 1) ‌For identical particle materials‌, increased total enthalpy significantly enhanced particle exit velocities, ‌with‌ Al2O3 particles reaching peak average velocities of 1302 m/s (2150 K), 1421 m/s (2770 K), and 1527 m/s (3570 K); 2) ‌Despite their larger size‌, graphite particles achieved higher peak velocity (1539 m/s) ‌attributed to‌ their lower density; 3) ‌Spatial analysis demonstrated near-normal distribution of axial velocity components along the radial (x) direction; 4) ‌Notably‌, distinct low-speed shear boundaries (35.5–45 mm span) were observed ‌at the jet periphery‌, ‌resulting from‌ free atmospheric interaction with arc-heater exhaust flows. ‌Comprehensive comparison‌ of particle velocity and vorticity distributions ‌under varied inflow conditions‌ elucidates jet boundary characteristics, ‌providing quantitative experimental support‌ for ‌precision evaluation‌ of particle erosion mechanisms.

     

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