Surrogate-Based Multiobjective Design Optimization of a Hydrogen Burner to Balance NO_xEmissions and Temperature

In hydrogen combustion, efforts to reduce NO_xemissions often lead to a decrease in combustion temperature, highlighting a fundamental trade-off between thermal efficiency and pollutant formation. This study addresses this challenge through a multiobjective optimization of a pure hydrogen-fueled burner, aiming to simultaneously minimize NO_xemissions and maximize combustion temperature. Computational Fluid Dynamics (CFD), Response Surface Methodology (RSM), and a Genetic Algorithm (GA) were integrated to explore and optimize burner geometry. CFD simulations using the realizable k-ε turbulence model and eddy dissipation concept were validated against experimental data in previous work, showing good agreement with a temperature mean absolute percentage error of approximately 5% and NO_xerror below 2%, confirming the reliability of the numerical approach. To enable surrogate model training, CFD simulations and sensitivity analysis were first performed. Four out of six geometric parameters were identified as influential and subsequently perturbed to generate the training data set. A third-order RSM was used to capture the highly nonlinear relationships between geometric variables and performance outcomes. Three representative optimal designs were selected from the final Pareto front generated by the GA: one prioritizing NO_xminimization, one maximizing temperature, and one offering a balanced trade-off. The optimized designs achieved significant performance improvements. Among the Pareto-optimal solutions, one design achieves a 29.6% reduction in NO_xemissions and a 7.8% increase in combustion temperature, demonstrating overall performance enhancement through improved air–fuel mixing and reduced residence time in the primary combustion zone. These results demonstrate the effectiveness of the proposed CFD-RSM-GA framework as a robust approach for multiobjective optimization. It enables the systematic design of hydrogen burners that meet both stringent environmental regulations and high thermal performance demands.