Measurement of Volatile Particulate Matter Emissions From Aircraft Engines Using a Simulated Plume Aging System

Abstract

Aircraft exhaust contains nonvolatile (soot) particulate matter (PM), trace gas pollutants, and volatile PM precursor material. Nonvolatile soot particles are predominantly present at the engine exit plane, but volatile PM precursors form new particles or add mass to the existing ones as the exhaust is diluted and cooled. Accurately characterizing the volatile PM mass, number, and size distribution is challenging due to this evolving nature and the impact of local ambient conditions on the gas-to-particle conversion processes. To accurately and consistently measure the aircraft PM emissions, a dilution and aging sampling system that can condense volatile precursors to particle phase to simulate the atmospheric evolution of aircraft engine exhaust has been developed. In this paper, a field demonstration of its operation is described. The dilution/aging probe system was tested using both a combustor rig and on-wing CFM56-7 engines. During the combustor rig testing at NASA Glenn Research Center, the dilution/aging probe supported formation of both nucleationigrowth mode particles and soot coatings. The results showed that by increasing residence time, the nucleation particles become larger in size, increase in total mass, and decrease in number. During the on-wing CFM56-7 engine testing at Chicago Midway Airport, the dilution!aging probe was able to form soot coatings along with nucleation mode particles, unlike conventional 1-m probe engine measurements. The number concentration of nucleation particles depended on the sample fraction and relative humidity of the dilution air. The performance of the instrument is analyzed and explained using computational microphysics simulations.

Effective Density and Mass-Mobility Exponent of Aircraft Turbine Particulate Matter

“…As expected, the shift with and without a CS was smaller in the diluted line than the undiluted line, as the dilution lowered the semivolatile material partial vapor pressure in the line, making it less likely for semivolatile material to condense. The presence of semivolatile material in the aircraft exhaust has been observed in other studies, such as by Anderson et al [59] and Peck et al [28]. As the gas turbine exhaust dilutes and cools in the sampling system, semivolatile material may partition from the gas to a particle phase by two paths: nucleation to form new particles, and adsorption or condensation on existing particles.…”

“…Mass-mobility relationships can be used to determine characteristics of particle morphology [20] or to calculate mass distributions from mobility size distributions [21,22]. Previous studies of gas turbine engine exhaust aerosol, based on the measurement of particle mobility size distributions, have assumed that the particles were solid spheres that have unit density [23][24][25][26][27][28] or the bulk density of carbon (1500-1900 kg∕m 3 ) [29][30][31] to determine mass distributions. These assumptions are questionable, as the particles are expected to be nonspherical and follow a fractal-like relationship, causing the effective density to be a function of the particle size.…”

A Review of Terminology Used to Describe Soot Formation and Evolution under Combustion and Pyrolytic Conditions

“…418,419 Volatile components, that is, volatile particulate matter (vPM), include H 2 SO 4 , water, unburned fuel, and PAHs. 419 The nvPM contributions to particulate matter are solid and consist primarily of mature soot particles. 306,419…”

“…419 The nvPM contributions to particulate matter are solid and consist primarily of mature soot particles. 306,419…”

“…Nonvolatile particulate matter (nvPM) is a term used by the aircraft industry and others to represent the component of particles that are not volatile below 350 °C. , Volatile components, that is, volatile particulate matter (vPM), include H 2 SO 4 , water, unburned fuel, and PAHs . The nvPM contributions to particulate matter are solid and consist primarily of mature soot particles. , …”