Development of Hydrogen Gas Non-contact Concentration Measurement Technology for Micro-area Observation

Abstract

When change over time of hydrogen gas concentration in a certain point is measured, a gas sensor is fixed at the measurement point, or a syringe is utilized to sample the gas, which is analyzed by gas chromatography. However, the gas sensor and the syringe have an influence on gas flow and its measurement. Non-contact measurement technology with high temporal resolution and high spatial resolution is necessary. Therefore, in this study, for the purpose of non-contact measurement of the hydrogen gas concentration in the small area under the gas flow, a specialized experimental device was developed. A laser beam (wavelength 355nm, pulse energy 120µJ, PRF 1kHz) with the beam diameter 1mmϕ at the measurement spot was irradiated to the hydrogen gas. Raman scattering light at the measurement point of 750mm ahead was focused by Fresnel lens, which is arranged at the orthogonal direction against the transmitting laser beam. As a result, it was proved that Raman signal intensity had good linear correlation with hydrogen density of more than 100ppm. The gas concentration in a small area could be quantitatively estimated without interference of the gas flow.