Large Eddy Simulation of Hydrogen Flame Stabilization in a Reheat Gas Turbine Combustor

Abstract

Abstract Reheat gas turbine combustors utilizing high hydrogen content fuel blends serve as a potentially effective low-emission alternative energy system; however, these combustors operate under unique conditions that lack low-cost models for accurately predicting flame stabilization. A large eddy simulation (LES) with detailed chemistry and adaptive mesh refinement is performed on a simplified geometry of the Ansaldo GT36 sequential combustor with an elevated inlet temperature and vitiated air-hydrogen flow in a rectangular mixing duct and combustion chamber, a configuration previously modeled with direct numerical simulation (DNS) in ref. [15]. Flame characteristics and stabilization are investigated, finding similarity in stabilization mechanism and location, but discrepancies in flame front shape and size as compared to DNS results — likely due to a combination of a reduced flame speed fuel composition from that used in DNS results and too coarse a grid for the highly reactive hydrogen fuel. Various wall treatments are investigated, finding indistinguishable behavior across heat transfer models for Law of Walls models, reduced heat transfer with an isothermal wall indicating unresolved length scales, and expected high near wall temperatures for adiabatic wall. The latter two causing significant differences in flame stabilization location and mechanism as compared to DNS results. Results gathered here validate the feasibility of stabilized sequential combustor LES models which can complement fundamental experimental and DNS results in their application to the design process, though further improvements to the LES model are needed before it can be applied to systematic flame characteristic analysis.