Measurement of Water Vapor Concentration in Narrow Channel of PEFC Using Fiber-Optic Sensor Based on Laser Absorption Spectroscopy

摘要

Water transport in polymer electrolyte fuel cells (PEFCs) is an important factor that determines their performance. The authors have developed a fiber-optic gas sensing technique for measuring water vapor concentration in flow channels of PEFCs based on tunable diode laser absorption spectroscopy (TDLAS). In this study, a transmission/reception integrated fiber-optic probe was first fabricated to detect absorption spectra of water in millimeter-scale channels of PEFCs. Furthermore, the TDLAS system with the fiber-optic probe was constructed and tentatively applied to the water measurement in a simulated flow cell. It was noted that the water vapor concentration can be estimated from the peak-valley ratio of the second-harmonic and the fourth-harmonic absorption spectra. The measurement accuracy of water mole fraction at 70°C is less than 0.5% in the range of 3.1 to 25.7%. These results suggest the TDLAS-based fiber-optic sensor enables to accurately monitor in-situ water distribution within actual fuel cells.