Effect of aerosol precursors from gas turbine engines on the volatile sulfate aerosols and ion clusters formation in aircraft plumes

Abstract

A comprehensive analysis of the influence of sulfate aerosol precursor gases and chemi-ions generation in the internal flow of a jet engine (gas turbine engine) on sulfate volatile aerosols and ion cluster formation in an aircraft plume is presented. The evolution of the aerosol size distribution and the chemical composition change is simulated using a previously developed quasi one-dimensional flow field model with coupled gas phase kinetics, aerosol nucleation, condensation, and coagulation processes. An increased abundance of the aerosol precursors SO₃, HSO₃, and H₂SO₄ at the nozzle exit leads to an increased number of larger volatile aerosol particles, with diameter > 5 and 9 nm, than previously measured in aircraft exhaust plumes. Most of the gaseous H₂SO₄ gets converted to liquid aerosol particles within about 1 s. The generation of HSO₄⁻, NO₃⁻, NO⁺, and H₃O⁺ ions in the combustor results in the formation of charged clusters, mostly HSO₄⁻(H₂SO₄)_m, NO₃⁻(HNO₃)(H₂O), HSO₄⁻(HNO₃)_n, H₃O⁺(H₂O)_m, H₃O⁺(CH₂O)(H₂O)_n in the near field plume (first few hundred meters). For typical cruise conditions of a B-747 aircraft the calculated values of ion cluster concentration at the distance from nozzle exit L < 40 m are around 3 × 10⁵–3 × 10⁶ cm⁻³ for fuel sulfur content (FSC ≥ 0.04%) and only 7 × 10⁴ cm⁻³ for free sulfur fuel (FSC = 0%).