Efficient Strategy for Low NOx Combustor Design in the Spatial Domain Using Multi-Fidelity Solutions

Gas turbine combustor designers now routinely use high-fidelity reactive computational fluid dynamics (CFD) analyses to gain valuable insight into the complex reactive flow-field and pollutant formation process. But, a large number of such computationally expensive CFD analyses are generally required to arrive at an acceptable combustor configuration. Therefore, given the practical limits on available computational resources and time, traditional combustor design methodologies using only high-fidelity CFD analyses need further improvement. To address this, a combustor design strategy using multifidelity co-Kriging response surface model (RSM) is developed and applied for the design of a two-dimensional test combustor problem in the spatial domain using steady-state Reynolds-averaged Navier Stokes (RANS) formulation. The design and optimization problem is set-up for two geometric variables and a single-objective, NOx concentration, as it is of current interest to the combustor design community. The developed multi-fidelity strategy is also assessed for performance against high-fidelity Kriging RSM strategy. This study demonstrates that the multi-fidelity design strategy can obtain good designs with up to ten times less effort than a full grid sampling search plan. However, the multi-fidelity co-Kriging strategy does not outperform the high-fidelity Kriging strategy for the given spatial domain problem.