偵測質子交換膜燃料電池流道板生成水的聲導波檢測

Abstract

質子交換膜燃料電池的運轉效能取決於電池組內部生成水分的管理，本研究於鋁合金流道板兩側設置陣列壓電陶瓷換能器，作為聲導波的致動器與感測器，監測流道板中水的分布。以有限元素法計算鋁合金流道板在某一固定波長下所獲得的頻率與模態變形，並繪製聲導波相速度頻散曲線，發現在相同頻率下會對應許多不同的聲導波模態，且當分析模型的寬度越大、流道數量越多時，低頻範圍與S0模態相交的其他撓曲模態會越多。 實驗以陣列聲導波感測器及雷射都卜勒干涉儀偵測流道含有不同水量之導波訊號，流道板前後邊緣多重反射訊號會干擾直接波傳的聲導波響應，造成導波相速度量測值與數值解間的差異。壓電陣列發射及接收端之間的插入損失變化量為反應生成水量的函數，實驗結果顯示聲導波的衰減與負載的水量多寡有關，聲導波的插入損失可作為質子交換膜燃料電池反應生成水的監測指標。

The operating performance of proton exchange membrane fuel cells (PEMFC) depends on the water production inside the cells. In this study, array piezoelectric ceramic transducers were surface adhered to flow field plate mockups made of aluminum alloy and used to generate and detect guided acoustic waves propagating along the flow channels. In-situ inspection of water distribution in PEM fuel cells is feasible by the presented method. The phase velocities for guided acoustic waves and their corresponding mode shapes were determined using finite element analysis (FEA). Besides the A0 and S0 modes, several additional bending modes caused by transverse vibrations of the stiffeners in flow field plate were found in the lower frequency range. In experiment, the acoustic wave signals were detected by two piezoelectric array sensors and laser Doppler interferometer for various amounts of water production. The fact of directly propagating guided waves interfered with multiply reflected echoes results in deviation of both measured and numerically predicted phase velocities of guided acoustic waves. The insertion loss between transmitted and received piezoelectric arrays was measured as a function of the quantity of water production. The results indicate that the attenuation of guided acoustic wave increases as the water content increases. The insertion loss is a significant index for monitoring water production in the flow field plate of PEM fuel cells.