Experimental verification of principal losses in a regulatory particulate matter emissions sampling system for aircraft turbine engines

Abstract

A sampling system for measuring emissions of nonvolatile particulate matter (nvPM) from aircraft gas turbine engines has been developed to replace the use of smoke number and is used for international regulatory purposes. This sampling system can be up to 35 m in length. The sampling system length in addition to the volatile particle remover (VPR) and other sampling system components lead to substantial particle losses, which are a function of the particle size distribution, ranging from 50 to 90% for particle number concentrations and 10-50% for particle mass concentrations. The particle size distribution is dependent on engine technology, operating point, and fuel composition. Any nvPM emissions measurement bias caused by the sampling system will lead to unrepresentative emissions measurements which limit the method as a universal metric. Hence, a method to estimate size dependent sampling system losses using the system parameters and the measured mass and number concentrations was also developed (SAE 2017; SAE 2019). An assessment of the particle losses in two principal components used in ARP6481 (SAE 2019) was conducted during the VAriable Response In Aircraft nvPM Testing (VARIAnT) 2 campaign. Measurements were made on the 25-meter sample line portion of the system using multiple, well characterized particle sizing instruments to obtain the penetration efficiencies. An agreement of ± 15% was obtained between the measured and the ARP6481 method penetrations for the 25-meter sample line portion of the system. Measurements of VPR penetration efficiency were also made to verify its performance for aviation nvPM number. The research also demonstrated the difficulty of making system loss measurements and substantiates the E-31 decision to predict rather than measure system losses.

Figure 1.

Diagram of ARP6320 sampling system. Standard conditions are 0 °C and 101.325 Pa.

Figure 2.

Schematics of (a) the AEDC sampling system, near source sampling shed, and the J85 engine test bay at the University of Tennessee Space Institute’s Propulsion Research Facility and (b) more detail with the locations of the size distribution measurements shown.

Figure 3.

Measured SMPS particle size distributions from the J85 engine at different PLAs with Jet-A fuel are shown in (a) to (c) with the penetration efficiencies computed from the measured size distributions compared to theoretical penetrations provided in (d) to (f). The distributions represent the average of 96, 14, and 66 scans for PLA15, PLA60, and PLA90, respectively.

Figure 4.

VPR penetration measurements, comparisons with manufacturer, and UTRC model. The top panel (a) shows the particle size distributions at PLA 15 when a 50/50 blend of Jet-A and Camelina fuels was used. The AEDC SMPS size distribution is plotted as measured and the UTRC SMPS is corrected for the dilution in the VPR. The line represents the average size distribution and the error bars show the standard deviation. The error bars highlight the variability. The bottom panel (b) shows the penetration efficiency obtained from the measured size distributions compared to the modeled penetration for the VPR. The distributions in (a) represent the average of 7 scans.