Gaseous SO3 and H2SO4 in the exhaust of an aircraft gas turbine engine: measurements by CIMS and implications for fuel sulfur conversion to sulfur (VI) and conversion of SO3 to H2SO4

An estimation of the conversion efficiency ( ) of fuel sulfur to SO3 and H2SO4, where =([SO3]+[H2SO4])/[ST] and [ST] is the total sulfur atom concentration in the exhaust at the exit of an aircraft gas-turbine combustor, was derived from measurements by comparison with model results. The major results of the presented CIMS experiments and their interpretation with a model simulation are: (i) The efficiency is =2.3±1% at an exhaust age of about 5 ms from the combustor exit; (ii) The SO3 molecules represent a major fraction of sulfur (VI) gases A<50% and an essential SO3-conversion to H2SO4 takes place in the sampling line where the exhaust gases spend a sufficiently long time and where the temperature is lower than in the hot exhaust. The coincidence of from our work (measurements with the sampling point in the exhaust just behind the combustor exit) and the measurements in an exhaust at a plume age of about 1 s suggests that the sulfur (VI) formation is inefficient in the post-combustor flow inside the aircraft engine.