基于图像处理技术的等离子体射流稳定性分析

Analyses on the Stability of Plasma Jet Based on Image Processing Techniques

在等离子体技术领域,目前主要基于分析等离子体电弧弧压波动情况间接的研究等离子体射流稳定性。提出一种利用CCD相机以一定频率拍摄等离子体射流图像,并基于MATLAB程序分析等离子体射流稳定性的方法。首先利用高速CCD相机按照设定的拍摄频率拍摄等离子体射流图像信息并保存;然后利用MATLAB程序将拍摄的等离子体射流图像转化为灰度图,并求取灰度图中像素大于阈值的像素长度;接着根据预先测量的单位像素长度与等离子体射流实际长度的比值获取等离子体射流实时长度值;最后求取等离子体射流长度与平均长度值的差值和平均长度的比值,定量的分析射流的稳定性。此外,基于此分析方法,通过实验对层流等离子体射流稳定性进行了分析,结果表明此法可有效在线或离线分析等离子体射流稳定性,且等离子体射流的实际波动情况并不与等离子体电弧的波动情况完全保持一致。

In the field of plasma technology, the stability of plasma jet is always studied indirectly by studyingthe fluctuations of plasma arc at present. A metliod to analyze the stability of plasma jet directly is proposed. Based on a special MATLAB program,this method can analyze the stability of plasma jet on line or off line by using a CCD camera to shoot the images of the plasma jet. Firstly, the images of the plasma jet are recorded automatically by a CCD camera with a specified frequency; Then, based on the special MATLAB program, the images of the plasma jet are converted to gray images to obtain th e ir lengths larger than a specified value determined by the ima-ges information ; Subsequently, the actual lengths of the plasma jet are obtained with a specified value determined by the actual length corresponding with an unit length in the gray image; Lastly, the stability of the plasma jet arequant-ational analyzed by obtaining the ratio between the difference value of actual length and mean length and mean length. In addition, based on this method,the stability of laminar plasma jets are analyzed experimental ly and comparatively. The results show that this metiiod could analyze the stability of plasma jet effectively and the stability of plasma jet could not be in accordance with the fluctuations of plasma arc well.