Numerical Evaluation of the Effect of Global Equivalence Ratio on Confined Turbulent Non-Premixed Flames

Abstract

The control of nitrogen oxides (NOx) is currently a major issue in designing an effective combustion system because NOx has several detrimental effects on the environment and human health. However, it is difficult to understand NOx formation processes in flames because of complicated interactions between the flow and chemistry. In this study, a partially-stirred-reactor combustion model is implemented in the OpenFOAM CFD tool to model confined turbulent non-premixed propane jet flames, and the NOx emission is evaluated in terms of the global equivalence ratio. The code solves Reynolds-Averaged Navier Stokes equations on an unstructured mesh in a cylindrical coordinate system. The computational predictions of scalar and flow fields in the combustion chamber are extensively compared to experimental measurements, and they show a good agreement. The oxidation and heat-release rates of propane are computationally evaluated, and they are used to verify the scalar fields such as temperature and mole fractions of species. The increase in the global equivalence ratio increases the maximum temperature of the furnace because of the enhancement of reaction rate, and thereby, leads to the enrichment of the NOx emission.

Characteristics of H₂/air annular jet flames using multiple shear coaxial injectors

“…Tucker et al (2008) compared the results of computational fluid dynamics (CFD), based on Reynolds-averaged Navier-Stokes and large-eddy simulations techniques, with experimental results for a rocket injector. The present study uses the standard k- model as the turbulent model and the partial stirred reactor model (Golovitchev, 2001, Somarathne et al, 2013 as the turbulence-reaction interaction model for hydrogen/air annular jet flames in a small chamber with multiple shear coaxial nozzles. This analysis is based on three-dimensional simulation of a 90 azimuthal section of the combustion chamber.…”

Modelling and simulation of high-pressure hydrogen jets using notional nozzle theory and open source code OpenFOAM

“…, represents the summation of the viscous and turbulent stresses. From the first terms of the right hand side of Eq.7 and Eq.8 the effective species and the thermal fluxes are calculated by summing the viscous and turbulent fluxes [23]. Finally, turbulent fluxes are calculated using the gradient-diffusion hypothesis in terms of turbulent viscosity, , (Eq.9) and turbulent thermal diffusivity, (Eq.10):…”

“…[25] in a round jet flow the stretching of turbulent vortex tubes by the mean flow has a significant influence on the process of scale reduction. Therefore as the jet spreads, rings of vorticity are stretched, which leads to greater scale reduction, greater dissipation, less kinetic energy and ultimately lower effective viscosity [23]. To counteract this effect the standard − model can be implemented in conjunction with the MUSCL third order approximation scheme following the study by Houf et al [26].…”