Hybrid Oxygen Enrichment and Preheating Strategy for Performance Recovery in Ultra‐Lean Micro–Trapped Vortex Combustors

ABSTRACT Ultra‐lean operation in micro‐combustion‐based thermophotovoltaic systems offers significant benefits including low pollutant emissions and increased longevity due to reduced thermal stresses, but it is hindered by low thermal performance. This paper numerically addresses the potential of oxygen enrichment and preheating to counteract performance losses in a hydrogen‐powered micro‐trapped vortex combustor operating under ultra‐lean conditions. A Taguchi design of 16 cases was conducted at a fixed equivalence ratio of ϕ = 0.3, varying inlet temperature from 300 to 450 K and O 2 levels from 21% to 30%, to evaluate their impact on radiative power, energy conversion efficiency, combustion efficiency, and NO x emissions. Results indicate that excessive enrichment (30% O 2 ) at high inlet temperature (≥ 400 K) leads to flame flashback, establishing an upper safety limit. Within the stable operating region, O 2 enrichment substantially improved radiative power by up to 56%, while preheating enhanced radiative efficiency by up to 73%, with both factors exhibiting equal influence on combustion efficiency. However, the use of oxygen‐enriched air remarkably increased NOx emissions compared to the baseline case at 21% O 2 . Moreover, the optimal configuration with T in = 450 K and X O2 = 0.27 has achieved 41% higher energy efficiency and 99% lower pollutant emissions compared to the lean case at ϕ = 0.8.