NUMERICAL MODEL AND EXPERIMENTAL VALIDATION OF ULTRA-LEAN AIR-HYDROGEN COMBUSTION IN CATALYTIC MONOLITHS

Hydrogen plays an important role in the energy transition. The exploitation of hydrogen in gas turbines, as well as in other combustion processes, is promising but it may favor the formation of nitrogen oxides due to its high adiabatic flame temperature. The catalytic combustion of ultra-lean air-hydrogen mixtures solves the issue and improves the stability of the reaction at partial loads. The present work develops a numerical model for the design of catalytic combustors able to process ultra-lean air-hydrogen mixtures. The model simulates the catalytic combustion in a honeycomb monolith. Such tool is useful for the sizing of innovative combustors for micro-gas turbines for power generation. The numerical model solves mass and energy balances in a two-dimensional domain describing a single channel of the monolith. The channel is modelled as a cylinder, while the outer radius describes the catalyst surface. A validation of the numerical model is performed with experimental data obtained on a dedicated test bench at low inlet temperature and pressure. Comparing the simulated results with the experimental measurements, a 0.6% difference in outlet bulk temperature is obtained. Ultimately, useful recommendations are provided for combustor designers, based on the estimations of the numerical model in different operating conditions.