Numerical Investigation of Pilot-Stabilized Turbulent Flames Using Steady Flamelet Model

In the present paper, 2D RANS simulations have been carried out to simulate the Sydney pilot-stabilized turbulent flames using the steady and unsteady flamelet (SF and USF) approach. The flamelet model provides an alternative to computationally exhaustive probability density function (PDF) based approach. The primary focus of this study is to assess the accuracy and applicability of the flamelet methodology to model pilot-stabilized flames, having different fuel composition, by studying the effects of velocity and fuel composition on the flame structure. From the results, it is observed that the steady flamelet model captures the radial profiles of mean axial velocity and turbulent kinetic energy with reasonable accuracy but over-predicts the mean temperature profiles significantly. Although SF captures the profiles of CO, H₂, CO₂, and H₂O adequately, it does not show much deviation between predictions as the jet velocity approaches the blow-off limit for studying the effect of jet velocity variation on the flame structure. For flames closer to blow-off, the peak values for the product species are found to be over-predicted. The unsteady effects using the unsteady flamelets have also been studied to assess the effects of jet velocity on flame characteristics and it has been observed that the unsteady flamelet results are similar to those obtained using the steady flamelet model. The effects of fuel variation on the flame structure are captured reasonably well by flamelet model.