Max B. Trueblood

A FIELD SAMPLING OF JET EXHAUST AEROSOLS

ABSTRACT A mobile aerosol sampling facility was installed and operated on the NCAR (National Center for Atmospheric Research) Sabreliner high altitude research aircraft, for the purpose of sampling aerosols related to cirrus cloud phenomena. During this project the opportunity arose to do field sampling on jet exhaust aerosols, and these results are reported here. Aerosol properties sampled include concentration, size distribution, and hydration properties. The aerosol sampling facility features two electrostatic aerosol classifiers (EACs), in tandem, with a saturator in between. The saturator allows the aerosol to be equilibrated at 100% relative humidity between sizings with the EACs. The facility occupies about the space of two short equipment racks on the aircraft, and collects samples through a tube projecting through the aircraft skin. Exhaust samples were taken from Pratt and Whitney PT 6-42, JT 12A-8, and JT 15-D-4 engines, all burning Jet-A fuel. The results indicate that aerosol sampling offer...

Condensation Coefficient Measurement for Water in the UMR Cloud Simulation Chamber

Abstract A systematic series of condensation coefficient measurements of water have been made using the University of Missouri—Rolla cooled-wall expansion chamber which simulates the thermodynamics of cloud. This coefficient is seen to decrease from a value near unity, at the outset of simulation, to a value in the neighborhood of 0.01 toward the end of a simulation. Final values of this coefficient are sufficiently low as to contribute significantly to the broadening of the drop-size distribution in cloud.

Hydration properties of combustion aerosols

There has been considerable recent interest in the hydration properties of combustion aerosols. Both their warm cloud condensation behavior and ice-nucleating ability have important atmospheric implications. At the University of Missouri-Rolla we have a substantial cloud simulation facility designed for the laboratory study of atmospheric processes under realistic conditions (i.e., temperature, pressure, and supersaturation) and time scales. A combustion aerosol capability has been added to this facility. We can generate a variety of combustion aerosols, under controlled and observed conditions, characterize and shape (modify their size distribution) these aerosols, and then examine their hydration behavior under either warm or cold conditions. Here we describe this combustion system and present results (size distributions and critical supersaturation distributions) for aerosols resulting from the combustion of various liquid fuels. The hydration of these aerosols is found to obey Kohler theory, and solub...

Particulate sizing and emission indices for a jet engine exhaust sampled at cruise

Particle size and emission indices measurements for jet engines, primarily the Rolls Royce RB211 engines on a NASA 757 aircraft are reported. These data were used to estimate the fraction of fuel sulfur that was converted to particulates. These measurements were made in-situ with the sampling aircraft several kilometers behind the source. Some complimentary ground measurements on the same source aircraft and engines are also reported. Significant differences are seen between the ground observations and the in-situ observations, indicating that plume processes are changing the aerosols characteristics.

N-acetylcysteineamide (NACA) prevents inflammation and oxidative stress in animals exposed to diesel engine exhaust

Diesel exhaust particles (DEPs), a by-product of diesel engine exhaust (DEE), are one of the major components of air borne particulate matter (PM) in the urban environment. DEPs are composed of soot, polycyclic aromatic hydrocarbons (PAHs), redox active semi-quinones, and transition metals, which are known to produce pro-oxidative and pro-inflammatory effects, thereby leading to oxidative stress-induced damage in the lungs. The objective of this study was to determine if N-acetylcysteineamide (NACA), a novel thiol antioxidant, confers protection to animals exposed to DEPs from oxidative stress-induced damage to the lung. To study this, male C57BL/6 mice, pretreated with either NACA (250mg/kg body weight) or saline, were exposed to DEPs (15mg/m(3)) or filtered air (1.5-3h/day) for nine consecutive days. The animals were sacrificed 24h after the last exposure. NACA-treated animals exposed to DEP had significant decreases in the number of macrophages and the amount of mucus plug formation in the lungs, as compared to the DEP-only exposed animals. In addition, DEP-exposed animals, pretreated with NACA, also experienced significantly lower oxidative stress than the untreated group, as indicated by the glutathione (GSH), and malondialdehyde (MDA) levels and catalase (CAT) activity. Further, DEP-induced toxicity in the lungs was reversed in NACA-treated animals, as indicated by the lactate dehydrogenase levels. Taken together, these data suggest that the thiol-antioxidant, NACA, can protect the lungs from DEP-induced inflammation and oxidative stress related damage.

Nucleation Experiments with Monodisperse NaCl Aerosols

Abstract Nucleation experiments with monodisperse NaCl aerosols showed good agreement with the Kohler theory relating the critical super-saturation Sc to the dry size. Aerosols produced by condensing NaCl showed the same Sc as those produced by evaporating aqueous NaCl solution droplets. This indicates that if there is an energy barrier in going from a dry NaCl particle to a solution droplet, this energy barrier is small. The fact that the evaporation aerosol particles are cubical crystals and the condensation aerosols are amorphous spheres is shown to make no difference in the nucleation threshold. The investigation also gives insights into the performance of the equipment used, especially the commercial electrostatic aerosol classifier and the vertical flow thermal diffusion chamber developed in this laboratory. When operating this chamber in the isothermal mode, a 36% upper limit was found on the uncertainty in Sc due to index of refraction sensitivity in sizing the water drops. Within this range of un...

Particle concentration characterization for jet engine emissions under cruise conditions

Airborne particle measurements during NASA project SUCCESS have shown that particle concentration profiles serve as good indicators of aircraft exhaust plume encounters. During exhaust plume penetrations there is a strong anticorrelation between the ratio of nonvolatile/total particulates and Nitrogen Oxide (NO) concentrations. An increase in fuel sulfur content was found to increase the total particle emission index, while the nonvolatile emission index remained unchanged. The EIs increased by a factor of 2.6 as the fuel sulfur increased from 70–700 ppm. The large particle size distribution (200–400 nm) was seen as a good long term indicator of an aircraft exhaust plume.

Methodology for Particle Characterization in the Exhaust Flows of Gas Turbine Engines

The University of Missouri-Rolla (UMR) has developed, constructed, and employed a trailer-housed mobile aerosol sampling system (MASS) for the physical characterization of particles extracted from the exhaust flows of gasturbine engines. The MASS has been designed for a range of sampling conditions typically encountered at exit planes of combustors, angular sector rigs, flame tubes, and actual engines. To date measurements have been conducted in test cells, altitude chambers, on the wing (on the ground), and in flight. Reaching beyond the historically used but limited concept of smoke number, the MASS relies on differential mobility analysis, laser particle sizing, transmission electron microscopy, and molecular absorption spectroscopy to measure directly particle number concentration and size distribution (0.01 to <25 μm), water mixing ratio, particle morphology, and carbon dioxide (CO2), Combined with key combustor/engine operating conditions and fuel properties the MASS provides a series of derived parameters including mean particle diameter and number-, surface-, and mass-based emission indices, which are important parameters for the performance characterization and environmental assessment of gas turbine engines. In this article we describe the technical details of the UMR MASS, discuss data reduction and experimental uncertainties, and show some example data sets.

Potential role of nuclei in cloud element formation at high altitudes

Abstract The role of aerosols in providing a heterogeneous nucleation contribution to cirrus cloud ice crystal formation has long been an unresolved question. A mobile aerosol sampling facility was employed on the NCAR Sabreliner research aircraft to take aerosol samples from the vicinity of cirrus clouds over Colorado and Wyoming. Tandem electrostatic classifier and impactor technique were used to measure aerosol size distribution, hydration capability and composition information. The results suggest that aerosol related heterogeneous nucleation processes are active in cirrus cloud processes.

Measured Spectra of the Hygroscopic Fraction of Atmospheric Aerosol Particles

Abstract The relation between dry diameter (X0) and critical supersaturation (Sc) for atmospheric submicron aerosol particles is investigated using a long term air sampling program at Rolla, Missouri. The particles are passed through an electrostatic aerosol size classifier, and then through an isothermal haze chamber. Results are reported in terms of an apparent volume fraction of soluble material, ϵv defined such that for particles composed only of ammonium sulfate and water insoluble compounds, ϵv is the actual volume fraction of soluble material. The probability distribution of ϵv is found to be approximately Gaussian in the ϵv range 0.2 to 1.3. The mean ϵv is 0.5, for electrostatic aerosol classifier settings of 0.2, 0.3, and 0.4 μm diameter.