Direct emissions and oxidative processing of aircraft turbine engine exhaust

Abstract:

Aircraft turbine engines emit both primary organic aerosols (POA) and volatile organic compounds (VOC) during the Landing/Take-off (LTO) cycle. Both can react in the atmosphere by aging POA or forming secondary organic aerosols (SOA). These emissions can potentially cause adverse health effects and affect regional air quality. In order to assess the impact of airport emissions, the detailed characterization of the primary and secondary aircraft emissions are required. Particularly, there are open questions on the characterization of VOCs and SOA and their dependence on atmospheric aging at each flight mode.

VOCs, POA and SOA from 7 turbine engines operated under simulated LTO cycle flight modes are presented. Measurements were conducted at the SR Technics engine test facility at Zurich Airport. Particle composition was investigated by a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), while the VOCs were characterized by a proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS). Atmospheric aging of engine emissions was simulated by oxidation in a potential aerosol mass (PAM) reactor and characterized as a function of OH exposure in the PAM. The PAM utilizes higher-than-ambient concentrations of OH radicals to perform the equivalent of about 40 hours of ambient oxidation in only 90 seconds.

VOC emissions and SOA yields are highest at idling and decrease with increasing thrust by a factor of ~ 10. The chemical composition of the exhaust changed with thrust. At low thrust, 30% of the VOC were hydrocarbons (total VOC emission index of 1.6 g/kg fuel) whereas at maximum thrust about 60% of the VOC emitted (total VOC emission index of 0.1 g/kg fuel) were oxygenated compounds e.g. carbonyls and acids. The relationship between aircraft VOC emissions and SOA formation is investigated and used to assess the effect of aircraft emissions on local air quality.