Online monitoring of oil film using electrical capacitance tomography and level set method.
Online monitoring of oil film using electrical capacitance tomography and level set method.
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DOI：
10.1063/1.4928060
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发表时间：
2015-08
期刊：
影响因子：
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通讯作者：
Q. Xue;B. Sun;Z. Cui;M. Ma;H. Wang
中科院分区：
文献类型：
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作者：
Q. Xue;B. Sun;Z. Cui;M. Ma;H. Wang
在油气润滑系统的应用中，电容层析成像（ECT）技术通过真实的重建油膜截面分布，为油气润滑管道油膜监测提供了一种新的途径。而对于小直径管道和薄油膜的情况，由于油膜与空气的界面在重建图像中不明显，所以油膜厚度很难直观地观察到。重建图像中伪影的存在严重影响了水平集等图像分割方法的有效性。此外，水平集方法由于计算速度慢，也不适用于在线监测。为了解决这些问题，开发了一种改进的水平集方法：将距离正则化水平集进化公式推广到ECT系统两相流在线成像中，定义窄带图像滤波器消除伪影的影响，并考虑油液分布变化的连续性，前一帧图像检测到的油气界面可以作为后续帧检测的初始轮廓;因此，可以大大加速从初始轮廓到边界的传播，使得真实的时间跟踪成为可能。为了验证所提出的方法的可行性，一个油气润滑设备的内径为4 mm的管道在正常运行时，使用8电极ECT系统进行测量。仿真和实验结果表明，改进的水平集方法能够准确地在线显示油气界面。
In the application of oil-air lubrication system, electrical capacitance tomography (ECT) provides a promising way for monitoring oil film in the pipelines by reconstructing cross sectional oil distributions in real time. While in the case of small diameter pipe and thin oil film, the thickness of the oil film is hard to be observed visually since the interface of oil and air is not obvious in the reconstructed images. And the existence of artifacts in the reconstructions has seriously influenced the effectiveness of image segmentation techniques such as level set method. Besides, level set method is also unavailable for online monitoring due to its low computation speed. To address these problems, a modified level set method is developed: a distance regularized level set evolution formulation is extended to image two-phase flow online using an ECT system, a narrowband image filter is defined to eliminate the influence of artifacts, and considering the continuity of the oil distribution variation, the detected oil-air interface of a former image can be used as the initial contour for the detection of the subsequent frame; thus, the propagation from the initial contour to the boundary can be greatly accelerated, making it possible for real time tracking. To testify the feasibility of the proposed method, an oil-air lubrication facility with 4 mm inner diameter pipe is measured in normal operation using an 8-electrode ECT system. Both simulation and experiment results indicate that the modified level set method is capable of visualizing the oil-air interface accurately online.