Feasibility of measuring moisture content of green sand by a low frequency multiprobe detector based on dielectric characteristics
Feasibility of measuring moisture content of green sand by a low frequency multiprobe detector based on dielectric characteristics
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DOI：
10.1007/s41230-023-2087-5
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发表时间：
2023-02
期刊：
影响因子：
1.6
通讯作者：
D. Shi;G. Gao;Minghai Sun;Yada Huang
中科院分区：
文献类型：
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作者：
D. Shi;G. Gao;Minghai Sun;Yada Huang
绿色砂是由硅砂、膨润土、水和煤粉以及其他添加剂混合而成。含水率是表征绿色砂性能的重要指标。基于绿色砂的介电特性和传输线理论，提出了一种利用低频多探头检测仪快速测量绿色砂含水率的方法。构建了一个系统，其中设计了具有不同布置和探针的六个探测器。实验结果表明，在29 MHz之前，传输线的电压差随频率的增加而增大，在35 MHz之后，传输线的电压差随频率的增加而减小。电压差平台出现在29-35 MHz的范围内，由于其对频率不敏感，因此适用于测量水分含量。随着探针深度的增加，电场强度逐渐减小，中心探针的电场强度始终大于边缘探针的电场强度。当探头距离砂样表面80 mm时，测得的边缘探头电场强度很弱。测定绿色砂含水率的最佳激励频率为29-33 MHz。最佳的探测器是一个中心探头和三个边缘探头，它们的长度分别为80 mm和60 mm。探头中心与边缘间距为25 mm，探头直径为5 mm，以输电线路电压差、膨润土含量、煤粉含量和可磁化率为输入层参数，以含水率为输出层参数，根据33 MHz下的实验结果，建立了绿色砂含水率预测的三层BP人工神经网络模型。当绿色砂含水率在3 wt.%范围内时，模型预测误差不大于3.3 -7wt. %。
Green sand is a mixture of silica sand, bentonite, water and coal powder, and other additives. Moisture content is an important index to characterize the properties of green sand. Based on the dielectric characteristics of green sand and transmission line theory, a method for rapidly measuring the moisture content of green sand by means of a low frequency multiprobe detector was proposed. A system was constructed, where six detectors with different arrangements and probes were designed. The experimental results showed that the voltage difference of transmission line increases with the increasing frequency before 29 MHz while decreases after 35 MHz. A voltage difference platform occurs in the range of 29–35 MHz, which is suitable for measuring the moisture content due to its insensitivity to frequency. The electric field intensity gradually decreases with the increase of the probe depth, and the intensity of central probe is always greater than that of the edge probe. When the distance of the probe away from the sand sample surface is 80 mm, the electric field intensity of the edge probe is found to be very weak. The optimal excitation frequency for measuring the moisture content of green sand is 29–33 MHz. The optimal detector is the one with one center probe and three edge probes, and their lengths are 80 mm and 60 mm, respectively. The distance between the center and edge probes is 25 mm, and the diameter of probes is 5 mm. Taking the voltage difference of transmission line, bentonite content, coal powder content and compactability as parameters of the input layer, and the moisture content as a parameter of the output layer, a three-layer BP artificial neural network model for predicting the moisture content of green sand was constructed according to the experimental results at 33 MHz. The prediction error of the model is not higher than 3.3% when the moisture content of green sand is within the range of 3wt.%–7wt.%.