Binary Coaxial Jet Flow

Marcio T Mendonca¹

¹ Instituto de Aeronautica e Espaco

doi:10.20906/CPS/COB-2015-0816

Resumo

There is a large number of applications where mixing between different gas species is relevant, in particular applications related to combustion, where mixing between fuel and oxidizer dictates the combustion efficiency. Besides the need to mix reactants properly there is the issue of combustion stability, where the interaction between the acoustic, hydrodynamic and thermal fields may lead to flame blowout or large oscillations that lead to the combustor failure. In this sense the analysis of disturbances propagation in binary flows composed of a fuel and an oxidizer will lead to a better understanding of the processes taking place in a combustion system. In order to study the stability and acoustic characteristics of coaxial binary jets an accurate solution of the base flow is needed. By solving the parabolic boundary layer equations numerically such accurate results may be obtained for laminar and turbulent flows, even close to the nozzle exit, where the jet has not yet become self-similar. The present investigation uses a boundary layer approach to study the characteristics of binary coaxial jets. The boundary layer equations are written in a streamwise, streamline coordinate system and solve implicitly for different configurations in order to investigate the effect of inner and outer nozzle diameter ratio, velocity ratio, temperature ratio, Mach number ratio and density ratio for different chemical species. Variable Prandtl, Lewis and Chapman-Rubesin parameters are considered, since it has been shown in the literature that they vary significantly across the shear layer in binary compressible flow configurations. Results for simple and coaxial jets of homogeneous and binary species are compared with experimental and other numerical results to validate the code. Then, the main topological characteristics of the given results are discussed in terms of vorticity, velocity and density distribution, aiming at the study of stability and acoustics to be performed and presented in a futu

Palavras-chave: coaxial jets; boundary layer; fuel oxidizer mixing; hydrodynamis stability