Modelling Heat Loss Effects in the Large Eddy Simulation of a Lean Swirl-Stabilised Flame

Abstract

The flame in a gas turbine model combustor close to blow-off is studied using large eddy simulation with the objective of investigating the sensitivity of including different heat loss effects within the modelling. A presumed joint probability density function approach based on the mixture fraction and progress variable with unstrained flamelets is used. The normalised enthalpy is included in the probability density function to account for heat loss within the flame. Two simulations are presented that use fixed temperature boundary conditions, and use adiabatic and non-adiabatic formulations of the combustion model. The results are compared against the previous fully adiabatic case and experimental data. The statistics for the simulations are similar to the results obtained from the fully adiabatic case. Improved statistics are obtained for the temperature in the near-wall regions. The non-adiabatic flamelet case shows the average reaction rate values at the flame root are approximately 50% smaller in comparison to the adiabatic flamelet cases. This causes the lift-off height to be overestimated. The time series of the lift-off height and the volume integrated heat release rate show that including non-adiabatic flamelets causes the flame to be highly unstable. A higher enthalpy deficit is seen in the near-field regions when the flame root is not present and experiencing some lift-off, suggesting that the flame is more dynamic when including heat loss.

On the blow‐off correlation for swirl‐stabilised flames with a precessing vortex core

“…These simulations demonstrated that the flame stabilisation and lift-off processes are highly influenced by the PVC. Furthermore, it has been demonstrated that including heat loss effects can influence the flame shape [25] and stability [24,26,27]. It is expected that the PVC attributes will be affected by heat loss as previously hinted [24].…”

“…Hence, the fluid mechanical processes in the GTMC are complex and challenging for numerical modelling. However, recent studies [21][22][23][24] have demonstrated that these flow features and flame characteristics can be captured well using a carefully designed flamelet based SGS combustion closure. These simulations demonstrated that the flame stabilisation and lift-off processes are highly influenced by the PVC.…”

Large eddy simulation and low-order modelling of azimuthal thermoacoustic instability in a gas turbine model annular combustor

“…Heat loss effects are implemented in a similar fashion to that used in Ref. 19 by scaling down the heat release rate in the energy equation. As can be seen in the figure, the computed adiabatic flame speeds agree well with the measurements and as the heat loss increases, the flame speed drops smoothly.…”

“…They showed that the heat loss effects are important for the swirl burners considered and need to be taken into account in the LES in order to correctly capture the thermoacoustic instability. Thus, a non-adiabatic flamelet approach is adopted from Massey et al 19 for this work and the heat loss effects on the instability simulation are investigated.…”

Impact of wall heat transfer in Large Eddy Simulation of flame dynamics in a swirled combustion chamber

“…The heat loss effects on the stabilization of a lean swirl-stabilized flame close to blow-off conditions was analyzed by Massey et. al [24], showing that the lift-off height is influenced by the wall heat transfer modelling. DNS was used to perform a sensitivity analysis of transfer functions of laminar flames [12], proving that the inlet air temperature affects both gas velocity and flame speed whereas the combustor wall-temperature determines the lift-off distance of the flame and controls the FTF delay.…”