Quantitative Laser-Saturated Fluorescence Measurements Of Nitric Oxide In A Heptane-Fueled Lean Direct-Injection Spray Flame At Varying Global Equivalence Ratios

摘要

We report the influence of equivalence ratio on nitric oxide (NO) concentration profiles in an unconfined heptane spray flame at atmospheric pressure. The associated burner is based on the lean direct-injection design. NO concentration profiles are measured using a modified laser-saturated fluorescence (LSF) method at four axial heights above the burner. The NO profiles are measured in three flames with global equivalence ratios of 1.0, 0.9, and 0.8. Probe measurements of CO_2 and O_2 mole fractions are used to determine effective equivalence ratios that result from entrained air. Through an analysis of area-averaged NO concentrations at various axial heights, the downstream [NO] is found to be mainly redistributed as the flame spreads owing to the intense recirculation of combustion products. Moreover, comparisons of [NO] profiles as a function of equivalence ratio demonstrate that dilution air is the dominant influence in the reduction of NO concentration at equivalence ratios leaner than stoichiometric.