CCD光谱层析技术重建氩等离子束射流三维温度场

3D Temperature Field Reconstruction of Ar Plasma Jet Using CCD Spectrum Tomography Technology

根据谱线相对强度法,提出了利用正交面阵CCD光谱层析技术,实时重建氩等离子束射流三维温度场的方法。通过CCD获得的待测场图像与没有射流射出时在待测场处放置的坐标纸图像进行比对,测量了实际待测场的大小;利用步进电机带动光纤探针对待测场进行扫描,通过光谱仪获得了待测场的光强分布。根据谱线相对强度法中谱线选取的原则,选择了696.5和763.5nm两条谱线作为研究对象。为防止CCD接收光强过饱和及待测场边缘光谱信息的损失,根据待测场的大小和光强分布设计了梯度衰减片,再通过窄带滤波片获得了待测场的光谱信息。结果表明与光纤光谱扫描法获得的结果吻合较好,不确定度为3.3%。系统满足了实时重建三维温度场的要求,为等离子束射流后续的密度场、压力场和速度场的实时诊断提供了坚实基础。

For realizing real-time 3D temperature field reconstruction of Ar plasma jet,an orthogonal area array CCD （charge coupled device） spectrum tomography experimental system was proposed according to spectrum relative intensity diagnosis method. The size of tested field was measured using comparison between the tested field image caught through CCD and the plotting paper image when plotting paper was placed in the tested field position with no plasma jet; the emission intensity distribution of tested field was obtained using stepping motor taking fiber probe to scan tested field,and the spectrum analysis instrument was used to show the spectrum intensity information. Based on spectrum selection principle of the spectrum relative intensity method,spectra at 696.5 and 763.5 nm were studied as characteristic spectrum. Novel grad attenuation was designed based on the size and intensity distribution of tested field for not exceeding limen of CCD and avoiding the spectrum information loss at tested field edge. The narrowband filter was set between grad attenuation and CCD,so the whole tested spectrum information can be stored in computer real-time. According to orthogonal two-view spectrum tomography reconstruction algorithm,when tested field is axially symmetric,the reconstruction result is well. So four area array CCDs is placed orthogonally,and the same spectrum narrowband filters are placed in front of two orthogonal CCDs to reconstruct 3D emissivity factor field. Based on the 3D emissivity factor field and spectrum relative intensity theory,3D temperature field of the tested field was reconstructed satisfactorily. The reconstruction result showed that it agreed with the results from fiber scanning diagnosis system,and the uncertain degreed is 3.3%. The proposed experimental device meets the needs of real-time 3D temperature field reconstruction. It provided a stable base for real-time diagnosis of plasma jet density field,pressure field and velocity field.