The aim of this project was to continue previous work on the understanding of the flameless combustion regime. Research on isothermal and reactive flows were conducted at FCT and at IST, respectively. Non-intrusive optical techniques allowed gather important information not yet available in the literature, such as the extension of the reaction and heat release zones. Detailed maps of velocities, temperatures and concentrations were also obtained for the reactive flow. In the isothermal experiments at FCT, key points of the flow generated by an axissymmetric confined jet were located. Estimatives of the recirculation ratio, an important parameter in flameless combustion, were also obtained. In what regards the numerical work, advanced turbulence models for the Reynolds averaged Navier-Stokes equations have been used (namely, k-e RNG, k-e realizable, k-w and Reynolds stress models). Advanced combustion models, such as the eddy dissipation concept and the joint scalar probability density function transport models were employed.
Partners: FCT/UNL and IDMEC Lisboa/IST/UTL
Funding organization: Science and Technology Foundation (PT)
Main achievements at FCT/UNL: Two experimental models of a burner and pressure probes were designed and constructed to carry out cold-flow experiments. The models were coupled, in turn, to a combustion chamber model and key experimental data was gathered for validation of the numerical models, namely the loci of the centres of recirculation, reattachment line, and point of maximum return velocity (see scheme). Estimatives of the global recirculation ratio were also obtained. It was found that decreasing the diameter of the air nozzle increased the global recirculation ratio, confirm previous theorectical reasoning. Numerical simulations of non-reactive have been performed with several turbulence models, with the k-ε RNG model producing results in better agreement with the experimental data. Exploratory simulations of IST’s reactive case were also performed with the EDC model and the reaction mechanism kee58