Simulation of Colorless Distributed Combustion

Sammanfattning: Colorless distributed combustion (CDC) is a promising novel technology to reduce emissions of carbon monoxide and nitrogen oxides in gas turbine combustors. CDC features a different flame regime than conventional gas turbine combustors, associated with a distributed reaction zone and low and uniform temperatures due to dilution of combustion air with exhaust gases. In this thesis, an attempt has been made at proposing a suitable simulation strategy in order to accurately predict reaction zone, temperature and pollutant emissions for methane-air combustion at an affordable computational cost. The simulations were performed in tandem with experiments on a specific combustor at the Combustion Laboratory of University of Maryland. The most popular approach in literature was found to be solution of the Reynolds-averaged Navier Stokes equations (RANS) with finite-rate chemistry as modeled by Eddy Dissipation Concept (EDC). Fluid dynamics and chemistry were simulated using the commercial computational fluid dynamics software Ansys Fluent. The non-reacting flow field was predicted using several two-equation and Reynolds stress (RSM) models. The results were compared to particle image velocitmetry (PIV) measurements of the flow field. The reacting flow was then simulated using different global reaction mechanisms and EDC model parameters. Numerical results were compared to experimentally obtained exhaust gas pollutant levels and flame front visualization by OH chemiluminescence. Results showed best convergence performance using the realizable k