Developmental Research of Multi-Fiber Optic Liquid Film Sensor

研制了两种新型的光纤液膜传感器，与传统的电导和电容探头相比，这两种传感器具有更强的通用性和可靠性。第一个传感器的拾取器(传感头)，我们称之为七光纤传感器，由七根光纤平行紧密连接组成，即一根中心光纤作为发射光纤，六根接收光纤环绕其周围。第二个传感器的拾取器，我们称之为单光纤传感器，只由一根光纤组成，它既起到传输光的作用，又起到从薄膜表面接收反射光的作用。这两种光纤传感器都可以应用于除不透明流体外的几乎所有流体薄膜流动。基于作者的测量理论，通过计算机模拟和模拟实验，研究了这两种传感器对液膜波的静态标定和动态响应特性。之后，将这些传感器应用于实际的垂直管内空气-水和空气-氟里昂R113两相环状流，并测量了局部和瞬时的油膜厚度。因此，以下事实得到了澄清。单光纤传感器可以测量0~2 mm的液膜厚度，由于单光纤传感器的输出信号只在液膜的波峰和波谷处获得，因此它可以区分液膜波形中的波峰和波谷，并可以测量这些部位的液膜厚度。因此，单光纤传感器可以确定液膜的整体波形。另一方面，七光纤传感器可以测量约1 mm到10 mm的薄膜厚度。它还可以区分液膜波形中的波峰和波谷，并能测量这些部位的局部和瞬时曲率以及液膜厚度。

Two kinds of fiber optic liquid film sensors have been newly developed, both of which are more versatile and more reliable than the conventional electric conductance and electric capacitance probes. A pickup (sensor head) of the first sensor, which we call a seven-fiber sensor, consists of seven fibers tightly joined each other in parallel, i.e. a centered fiber serving as a transmitting fiber and six receiving fibers surrounding it. A pickup of the second sensor, which we call a mono-fiber sensor, consists of only one fiber playing both roles of transmitting light and of receiving the reflected light from a film surface. Both these fiber optic sensors can be applied to almost all the fluid film flow except an opaque one.The characteristics of a static calibration and a dynamic response of these sensors to liquid film wave have been investigated by computer simulations based on the authors' measurement theory and by simulation experiments. After that, these sensors have been applied to actual air-water and air-Freon R113 two-phase annular flows in a vertical tube, and the local and instantaneous value of the film thickness has been measured using these sensors. The following facts have been as a result clarified. The mono-fiber sensor can measure the film thickness ranging from 0mm to about 2 mm and it can distinguish the crest and the trough from other parts in the wave-form of the liquid film and can measure the film thickness at these parts because the output signal is obtained from the mono-fiber sensor only at the crest and the trough. The mono-fiber sensor can therefore determine the overall wave-form of the liquid film. On the other hand, the seven-fiber sensor can measure the film thickness ranging about from 1 mm to 10 mm. It can also distinguish the crest and the trough in the wave-form of the liquid film and can measure the local and instantaneous value of the curvature as well as the film thickness at these parts.