Dr. William Calhoon from our CRAFT Tech office in Huntsville, AL has recently developed an advanced, computationally efficient turbulent combustion model for large-eddy simulation (LES) of aircraft and power system gas turbine combustors. This new formulation is designed to capture local flame extinction and global flame blow-out effects, thereby enabling improved predictions of lean blow-out limits. Computational efficiency of the model is achieved by storing the required LES closure statistics in a database that may be quickly retrieved during a simulation. The model statistics for this database are generated through an innovative application of the linear-eddy model to the counter flow configuration (LEM-CF). One key feature of this formulation is that it includes the LEM-CF prediction of turbulent flame extinction limits to develop a localized extinction criterion for LES.
This new formulation has recently been applied to predict local extinction effects and global blow-off in a laboratory flame relevant to gas turbine combustion, which was presented at the 2015 AIAA SciTech Conference in Kissimmiee, FL. This study demonstrated the accuracy of the formulation in capturing flame temperature suppression due to local flame extinction, and in predicting of the global blow-out limit. This study also identified an oscillating flame mode just prior to global extinction. The dynamics of this oscillating flame mode are illustrated in the first movie included below. A slight increase in the jet velocity beyond this condition resulted in global blow-out as illustrated in the second movie included below.
This new modeling formulation has been developed for application to a wide range of commercial CFD flow solvers through the development of a portable user-defined-function (UDF) implementation. This UDF implementation has been demonstrated for application within the ANASYS FLUENT® flow solver. The UDF and model generation software for this formulation are available for licensing from CRAFT Tech. Contact us for more information.