Model simulations of fuel sulfur conversion efficiencies in an aircraft engine: Dependence on reaction rate constants and initial species mixing ratios

The fuel sulfur conversion efficiency ε behind the combustor of a JT9D-7A aircraft engine in flight has been simulated using an extended exhaust plume chemistry model. The model simulations start in the high-temperature intra-engine regime behind the combustor. The simulations show that the sulfur conversion efficiency is sensitively dependent on model assumptions like reaction rate constants and initial mixing ratios. Sensitivity studies to demonstrate the effect of the uncertainties and variabilities of these parameters on ε are presented. Among the rate constants k, the uncertainty of the reaction rate constant for SO₂ + OH + M → HSO₃ + M has the greatest effect on ε: The uncertainty of k(SO₂ + OH) results in an uncertainty range of 1.1% <ε<6.2% for our simulation scenario, with a most probable value around 3.8%. The effect of the reaction SO₂ + O + M → SO₃ + M on ε is very small if the initial mixing ratio of O is smaller than that of OH. Among the initial mixing ratios, the variation of the initial OH mixing ratio OH₀ has the greatest effect on ε. For our simulation scenario, the uncertainty range of 5.7 ppmv < OH₀ < 14.7 ppmv (inferred from measurements) leads to an uncertainty range of 2.7% <ε<5.0%.