Numerical evaluation of lean premixed turbulent flame characteristics on co-axial cylinder configuration at gas turbine conditions
The present RANS-combustion study focuses on the flame behaviour and turbulent flame speeds at different equivalence ratios of methane/air mixtures typical of gas turbine conditions. It also highlights degree of accuracy of the Weller combustion model available in the XiFoam solver, for a set of conditions, for three equivalence ratios, for leaner mixtures (φ) 0.43, 0.50 and 0.56, at high pressure 5 bar and preheating temperature 673K, at bulk velocity of 40m/s. We present and discuss the flame position, turbulent flame speeds are in comparison with experimental data. This study uses two sub-models available in the Weller combustion model, to show the strong influence of equivalence ratio on above flame quantities. For lean mixture (φ = 0.43), the flame shape is elliptic with increased flame brush thickness whereas for rich mixture (φ= 0.56) produces a flame of conical shape of reduced flame brush thickness. We will show a good quantitative agreement between experiment and simulations. We will show that for the current geometry the turbulent strain has no much influence on laminar flame speed. Using b-Xi two-equation Weller model seems to capture the flame characteristics with more accuracy at the cost of computational time. However, with one equation model transport equation for `b’ and algebraic model for `Xi’, the results obtained are reasonably good at relatively less computational time.