Sparse tomographic reconstruction of temperature and concentration in ammonia flames

Two-dimensional temperature and nitric oxide concentration fields are reconstructed in a steady-state NH₃-O₂-enriched air flame in a Hencken burner using spatially sparse laser absorption spectroscopy and algebraic reconstruction tomography (ART). The flame is probed with two quantum cascade lasers centered at 5.263 and 5.397µm, respectively, to obtain sparse line-of-sight absorbance measurements. Data are taken across the ammonia flame at equivalence ratios ranging from 0.7 to 1.3 in 0.1 increments, at discrete offset positions (0-12.25mm), and at three axial heights (1, 2, and 3cm) above the burner surface. The resulting limited-angle, underdetermined dataset is processed using ART to recover two-dimensional fields. The temperature field is obtained by two-line thermometry. This work demonstrates the feasibility and effectiveness of sparse tomographic methods for spatially resolved diagnostics in reactive flows, particularly in environments where full data coverage may be impractical.