A hydrogen gas concentration measurement method using the Raman lidar system

Abstract
The Raman lidar system is a hydrogen gas detecting technique capable of detecting the local hydrogen gas concentration and range in air remotely, because hydrogen gas has a very strong Raman effect. Therefore, hydrogen Raman cells have been widely used for laser wavelength conversion. This paper discusses a method for measuring hydrogen gas concentration using the Raman lidar system. Hydrogen gas combustion is affected by the volume percent of local hydrogen gas concentration in air, and for safety, accurate measurement is important. When hydrogen gas leaks into the air, the local composition of the air is changed. However, the Raman Effect is affected by the number of molecules. Therefore, it is impossible to measure the volume percent concentration of hydrogen gas when using one of the Raman signals of the hydrogen gas or nitrogen gas. To measure the volume percent concentration of hydrogen gas using the Raman lidar system, the equation between the concentrations of hydrogen gas in volumetric concentration units was derived using the ratio of the Raman signal from hydrogen and nitrogen gas. To verify the equation, hydrogen gas concentration measuring experiments were carried out using the Raman lidar system. The results confirmed the Raman lidar system was able to measure the volume percent concentration of hydrogen gas from 0 to 30 Vol.% at a distance of up to 30 m.