Determination of particle penetration factors in a particle transfer line for aero gas turbine engine exhaust particle measurement

There is a need to develop a reliable and standard PM (Particulate Matter) measurement method for aircraft engines. Due to safety and practicability of such measurements, a distance is required for the transportation of the exhaust samples from the aircraft engine exhaust exit to particle measurement instruments. The particle line loss during the transportation is therefore a critical issue for the accurate and reliable determination of particle emissions from aircraft engines. The work in this paper investigated the particle penetration/loss along a 25 meters ARP proposed particle sample transfer line by measuring the particle emissions from an aircraft auxiliary power unit (APU) at idle and full power. Two SMPS instruments were used to simultaneously measure exhaust particle size distributions at the entrance and exit of the 25 m transfer line. A catalytic stripper was used to remove volatile particles so that non-volatile particles can be measured. The particle penetration factors for the 25 m transfer line were found to be 0.6∼0.7 in general, excluding particles smaller than 10 nm. For the particles smaller than 10nm, particle penetrations were very poor and about 70-100% of parcel losses were observed. The volatile factions were roughly 20∼30% of the total concentrations.