An ultra-rapid optical gas standard for dynamic processes: Absolute NH3 quantification and uncertainty evaluation

Abstract

An ultra-rapid Optical Gas Standard (OGS) for absolute NH3 quantification in the shock tube has been developed. For the first time, the absolute NH3 mole fractions before the incident shock wave, after the incident shock wave and immediately after the reflected shock wave (within 25 μs) were quantified using OGS. On that basis, spectrally resolved NH3 absorption cross-section datasets were measured over pressure ranges of 1.15–3.15 bar and elevated temperatures (up to 2680 K), facilitating NH3 mole fraction quantification after the reflected shock wave using a correlative linear fit method. Besides, comprehensive uncertainty evaluations were conducted for thermodynamic parameters and species mole fraction following the 'Guide to the Expression of Uncertainty in Measurement (GUM)'. This metrological uncertainty analysis not only contributes to providing high-quality data but also serves as a valuable reference for other traceable measurements in shock tubes, such as dynamic temperature and pressure calibrations.