Spatially Resolved Emission Measurements on a Hydrogen-Fueled Full-Ring Combustion Chamber Test Bench

Abstract Hydrogen is widely viewed as a promising sustainable fuel without direct carbon emissions. However, it introduces new challenges related to pollutant formation, which demand precise and dynamic diagnostics. Accurate measurements of exhaust gas composition are essential, as they provide valuable insights into mechanisms of pollutant formation and serve as a key indicator of combustion efficiency, stability, and overall system performance. This work presents a tunable diode laser absorption spectroscopy (TDLAS)-based sensor adapted for extractive exhaust gas analysis in a full annular combustor rig. The system enables high-temporal-resolution detection of the key combustion species NO, NO2, O2, and H2O, which are typical for hydrogen combustion. While these species are traditionally measured using different sensing principles, such as chemiluminescence and paramagnetic detection, TDLAS allows simultaneous measurements of all four molecules. It offers calibration-free operation, independence from mass flow, an unmodified gas matrix, and excellent temporal resolution. For spatially resolved diagnostics, the measurement probe was traversed around the annular exit plane of the combustion chamber in a predefined time. A comparison with conventional measurement equipment under stable combustion conditions demonstrates that the TDLAS system not only reproduces results from established techniques but can even surpass them in terms of temporal resolution and selectivity.