The design of a combustion chamber operated in MILD regime — Numerical modeling of hydrogen combustion in oxygen–steam mixtures

Abstract

The goal of the current work is to develop a combustion chamber that can operate on recirculated steam produced by burning hydrogen in oxygen under conditions of Moderate or Intense oxygen Dilution (MILD) in atmospheric and stoichiometric conditions. The study investigates several configurations of combustor with nozzles, taking into account the overall temperature, OH radicals, and heat release rate distribution throughout the combustor’s domain. Thermal power variations of the steam generator (5 to 20 kW) were examined in conjunction with different oxygen dilutions with steam, down to 3% of O₂ (by mol.). The outcomes reveal that a rise in dilution degree promotes a drop in the mean temperature across every case and reagents’ recirculation with homogeneous temperature field, suggesting the presence of MILD combustion. The highest temperature values were observed at the stoichiometric mixture fraction. Higher dilution degree revealed more efficient heat release across the domain with low fluctuations from the reference MILD combustion data. Of the two combustion models studied, the Partially Stirred Reactor model did not show flame extinction at the highest dilution degrees, unlike the Eddy Dissipation model. The selected final design of the combustion chamber was used for constructing the actual combustor dedicated for lab-scale operation.