Owing to the determinant effects of the local distribution of solids concentration on transport phenomena, particularly in gas-solids flows in such processing units as gas-solid fluidized beds and pneumatic conveying lines, its accurate measurement has received considerable attention. Despite the widespread applications of optical fibre probes for the measurement of local solids concentration, these instruments may create measurement uncertainties due to their structural designs and challenges in their accurate calibrations. Several calibration methods have been proposed in the literature, while they need to be further improved. In the present study, we calibrated in-house, fabricated, solids concentration mixed parallel optical fibre probes by two sets of solids-polymer blocks covering solids volume fractions in the range of 0-0.30. The uniform blocks were produced by a twin-screw extruder and an injection moulding machine. FCC particles, 86 μm in diameter, formed the dispersed solids in the blocks, while poly styrene and poly methyl methacrylate were separately acting as the transparent medium. They helped us investigate the effects of the refractive index of the medium and the probe tip design on the calibration curve. The blind distance (zone) in front of the adopted probes was determined, at about 0.70 mm, upon measuring their reflective curves. Two glass windows with 1.00 and 1.60 mm thicknesses were separately installed at the tip of a probe to study their effects on the calibration curve. Experimental results indicated that in the absence of a glass window, the probes' voltage readings varied nonlinearly with solids concentration, the voltage readings were higher for blocks with a higher refractive index of the transparent medium, while the normalized calibration curves were similar for both sets of solids-polymer blocks. In addition, the extent of the uniform distribution of illuminating and reflecting fibre strands at the tip of a mixed parallel optical fibre probe can change the degree of nonlinearity of its calibration curve. The application of glass windows thicker than the blind distance decreased the degree of nonlinearity of the calibration curve, yet did not completely eliminate it.

中文翻译：

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用固体聚合物块校准固体浓度光纤探头

由于固体浓度局部分布对输送现象的决定性影响，特别是在气固流化床和气力输送管线等处理装置中的气固流动中，其精确测量受到了相当大的关注。尽管光纤探头广泛应用于测量局部固体浓度，但由于其结构设计和精确校准方面的挑战，这些仪器可能会产生测量不确定性。文献中已经提出了几种校准方法，但它们需要进一步改进。在本研究中，我们通过两组固体-聚合物块覆盖了 0-0.30 范围内的固体体积分数，校准了内部制造的固体浓度混合平行光纤探头。均质块由双螺杆挤出机和注塑机生产。直径为 86 μm 的 FCC 颗粒在块体中形成分散的固体，而聚苯乙烯和聚甲基丙烯酸甲酯分别作为透明介质。他们帮助我们研究了介质的折射率和探头尖端设计对校准曲线的影响。在测量它们的反射曲线时，确定所采用的探头前面的盲区（区域）约为 0.70 毫米。两个厚度为 1.00 和 1.60 mm 的玻璃窗分别安装在探头的尖端，以研究它们对校准曲线的影响。实验结果表明，在没有玻璃窗的情况下，探针的电压读数随固体浓度呈非线性变化，透明介质折射率较高的块的电压读数较高，而两组固体聚合物块的归一化校准曲线相似。此外，混合平行光纤探头尖端的照明和反射光纤束的均匀分布程度可以改变其校准曲线的非线性程度。应用比盲距厚的玻璃窗降低了校准曲线的非线性程度，但并没有完全消除它。混合平行光纤探头尖端的照明和反射光纤束的均匀分布程度可以改变其校准曲线的非线性程度。应用比盲距厚的玻璃窗降低了校准曲线的非线性程度，但并没有完全消除它。混合平行光纤探头尖端的照明和反射光纤束的均匀分布程度可以改变其校准曲线的非线性程度。应用比盲距厚的玻璃窗降低了校准曲线的非线性程度，但并没有完全消除它。