The objectives of this project were to demonstrate the performance and viability of three devices to condition aircraft turbine engine exhaust for the measurement of non-volatile and total (volatile and non-volatile) particulate matter (PM) emissions. These measurements were needed to assess the environmental burden of military and commercial aircraft to verify compliance with future regulations. Non-volatile PM are those found at the engine exit conditions, whereas volatile PM are those formed in the atmosphere from organic and sulfur exhaust compounds. Accurate measurement of turbine engine non-volatile PM was challenging due to a number of factors, including: (1) difficulty of sampling in the harsh environment found at the engine exit, (2) particle losses in the sample lines, (3) PM physical and chemical transformations as it was transported to the instrumentation. Measurements of volatile PM were even more difficult as these were formed in the exhaust plume and were influenced by fuel, ambient conditions and the volatile species composition.
Two devices, a dilution chamber (DC) and a condensation dilution probe (CDP), were evaluated to assess their effectiveness to condition turbine engine exhaust for total PM emissions measurements. Both were designed to promote the condensation of volatile species, which could then be characterized along with non-volatile PM using conventional aerosol instruments. The third device, a vapor particle separator (VPS) used to separate volatile and non-volatile species, was evaluated to support the measurement of only non-volatile PM. The performance of the VPS was assessed in the laboratory by using tetracontane (C40) particles and during field demonstrations using exhaust from two turbine engines (T63 and PW-F117).
PM physical and chemical properties were measured at the exit of the condensation devices at several engine settings, and compared to measurements made in the exhaust plume. Data show that the devices promoted the formation of volatile PM, therefore simulating ambient gas-to-particle processes. However, the concentration of particles formed was significantly lower than those found at plume locations, especially when the engine was operated with high sulfur content fuel. Since neither condensation device met all the performance objectives set for the project, it was concluded that these technologies were not currently ready to use for compliance relevant measurements. Based on the set performance criteria, the VPS met the objectives of the project. Evaluations against the criteria set by the Society of Automotive Engineers (SAE) E31 committee Aerospace Recommended Practice (ARP) 6320 for volatile particle removers (VPR) shall follow to further validate its use for non-volatile PM measurement.
Pending further improvements and successful performance demonstrations, the implementation issues for these devices were relatively minor since the sampling system from engine to device was the same as those existing for gaseous emissions and smoke number certification of engines. Additions include the dilution device, sampling lines for the sample after conditioning, and the PM characterization instruments. Regarding the VPS, implementation issues were minimal and believed to be simpler than the use of the Volatile Particle Remover (VPR) systems considered presently by the SAE E31 committee.