Teresa Parra

Flame Kernel Growth in a Rotating Gas

The communication deals with an ignition kernel development in uniformly rotating mixture. A simple model is presented in order to predict the time evolution of the kernel length and its diameter under the assumption of ignition on the axis of rotation, which is preferred mode for rapid flame development. The analytic expressions for flame radius and length are compared with experimental results. The predicted radius growth rate is in good agreement with experimental data, whereas the length evolution rate predictions deviate substantially from measurements due to flame propagation effects involving quenching and perturbation of the surrounding flow by the growing kernel. An interesting general result supported by the theory and experiment is that the diameter growth rate of the cylindrical part of the kernel is about half the growth rate of the spherical kernel in a quiescent mixture and is independent of the rotation rate. Wall effects start to reduce the kernel development rate when the distance from the wall is less than double the kernel diameter. The effects are quite strong.

Numerical simulation of the performance of a human nasal cavity

Purpose – The paper aims to focus on airflow and heat transfer inside the human nasal cavity. The contribution of this work is the inertial analysis of the momentum and thermal stress of the cavity throughout the respiratory cycle.Design/methodology/approach – By means of computer tomography scans, an accurate three‐dimensional anatomical representation of the human nasal cavity was obtained. A three‐dimensional numerical model is presented in order to predict the time evolution of flow patterns during a quiet breathing cycle, covering inhalation and exhalation. An inertial analysis of the momentum and a detailed study of the thermal behaviour during the breathing cycle is carried out.Findings – Head loss, velocity and temperature values are in agreement with experimental results from previous studies. Based on these results, the influence of the inhalation and the exhalation on the flow pattern and air conditioning has been reviewed. Results suggest that the anterior and posterior turbinate regions are w...

Numerical Modelling of Swirl-Stabilized Turbulent Lean Non-Premixed Flames

Numerical simulations have been performed to analyze the interaction of confined coaxial high-swirl jets in both cases: isothermal and reactive flows. Besides different setups of swirl injectors have been tested to study the influence of swirl in the flames for both stoichiometric and lean mixtures. The aim was to quantify the nitrogen oxide emissions as well as the flow pattern for different swirling annular air jet and non-swirling inner fuel jet. This simple setup is widely used in burners to promote stabilized flames of lean mixtures producing ultra low NOx emissions.

Mixing and combustion of turbulent coaxial jets an application of Computational Fluid Dynamics to swirling flows

The aim of this research is gaining an insight into flow patterns in swirling burners. These are suitable for lean mixtures, because of procuring the fix position of the flame. The interaction of the two reactive confined swirling jets leads to the formation of complex patterns which are not well understood. In the present study, these flow patterns are numerically investigated using Reynolds Averaging Navier-Stokes (RANS) equations for the flow and a Probability Density Function is used for modelling the combustion. Two swirl numbers were characterised: 0.14 and 0.74. Strong swirling annular jets are responsible of an inner recirculation zone. Low swirling flows produce poorer mixture and wide flame fronts whereas strong swirling flows are precursors of mixing enhancement and thing flame fronts.