Non-volatile Particulate Matter Emissions Research Articles

Predicting aviation non-volatile particulate matter emissions at cruise via convolutional neural network

Aviation emissions are the only direct source of anthropogenic particulate pollution at high altitudes, which can form contrails and contrail-induced clouds, with consequent effects upon global radiative forcing. In this study, we develop a predictive model, called APMEP-CNN, for aviation non-volatile particulate matter (nvPM) emissions using a convolutional neural network (CNN) technique. The model is established with data sets from the newly published aviation emission databank and measurement results from several field studies on the ground and during cruise operation. The model also takes the influence of sustainable aviation fuels (SAFs) on nvPM emissions into account by considering fuel properties. This study demonstrates that the APMEP-CNN can predict nvPM emission index in mass (EIm) and number (EIn) for a number of high-bypass turbofan engines. The accuracy of predicting EIm and EIn at ground level is significantly improved (R2 = 0.96 and 0.96) compared to the published models. We verify the suitability and the applicability of the APMEP-CNN model for estimating nvPM emissions at cruise and burning SAFs and blend fuels, and find that our predictions for EIm are within ±36.4 % of the measurements at cruise and within ±33.0 % of the measurements burning SAFs in average. In the worst case, the APMEP-CNN prediction is different by −69.2 % from the measurements at cruise for the JT3D-3B engine. Thus, the APMEP-CNN model can provide new data for establishing accurate emission inventories of global aviation and help assess the impact of aviation emissions on human health, environment and climate. SynopsisThe results of this paper provide accurate predictions of nvPM emissions from in-use aircraft engines, which impact airport local air quality and global radiative forcing.

Responses of reconstituted human bronchial epithelia from normal and health-compromised donors to non-volatile particulate matter emissions from an aircraft turbofan engine

Health effects of particulate matter (PM) from aircraft engines have not been adequately studied since controlled laboratory studies reflecting realistic conditions regarding aerosols, target tissue, particle exposure and deposited particle dose are logistically challenging. Due to the important contributions of aircraft engine emissions to air pollution, we employed a unique experimental setup to deposit exhaust particles directly from an aircraft engine onto reconstituted human bronchial epithelia (HBE) at air-liquid interface under conditions similar to in vivo airways to mimic realistic human exposure. The toxicity of non-volatile PM (nvPM) from a CFM56-7B26 aircraft engine was evaluated under realistic engine conditions by sampling and exposing HBE derived from donors of normal and compromised health status to exhaust for 1 h followed by biomarker analysis 24 h post exposure. Particle deposition varied depending on the engine thrust levels with 85% thrust producing the highest nvPM mass and number emissions with estimated surface deposition of 3.17 × 109 particles cm−2 or 337.1 ng cm−2. Transient increase in cytotoxicity was observed after exposure to nvPM in epithelia derived from a normal donor as well as a decrease in the secretion of interleukin 6 and monocyte chemotactic protein 1. Non-replicated multiple exposures of epithelia derived from a normal donor to nvPM primarily led to a pro-inflammatory response, while both cytotoxicity and oxidative stress induction remained unaffected. This raises concerns for the long-term implications of aircraft nvPM for human pulmonary health, especially in occupational settings.

Assessment of predicted aircraft engine non-volatile particulate matter emissions at Hangzhou Xiaoshan International Airport using an integrated method

ABSTRACT Assessing the aircraft engine nonvolatile particulate matter (nvPM) emissions during landing and take-off (LTO) cycles is significant for airport air quality management. However, presently few prior studies have examined aircraft engine nvPM emissions on a daily basis for optimizing flight operations at airports. Therefore, based on the latest first-order approximation method of engine nvPM emissions, we introduce the engine emission data and aircraft flight data to establish an integrated method for estimating daily aircraft engine nvPM emissions at airports. This method can be applied to obtain different engine nvPM mass and number emissions in each phase of the LTO cycle, and therefore the total nvPM mass and number emissions in different time periods can be estimated for the analysis of the sources and trends of daily aircraft engine nvPM emissions during LTO cycles at Hangzhou Xiaoshan International Airport. Results show that the highest aircraft engine nvPM mass and number emissions are generally predicted to occur in the climb and taxi/ground idle phase, respectively. The proportion of total engine nvPM mass and number emissions in each phase of the LTO cycle could also be estimated, specifically the take-off phase (21% & 6%), climb phase (52% &15%), approach phase (8% & 27%), and taxi/ground idle phase (19% & 52%). In addition, the trends of hourly engine nvPM mass and number emissions during LTO cycles within a day are similar, but the predicted highest total hourly engine nvPM mass and number emissions occur in different time periods (7:00–8:00 a.m. & 11:00–12:00 a.m.) at the airport, and the total hourly engine nvPM mass and number emissions at 6:00 a.m. to 17:00 p.m. are generally higher than those of the rest periods. These results are valuable for optimizing flight operations for mitigating the environmental impact of aircraft engine nvPM emissions. Implications: The integrated method for estimating engine nvPM mass and number emissions in the LTO cycle based on FOA4.0 method reported in this study is effective to assess the sources and trends of daily aircraft engine nvPM emissions during LTO cycles at airports, which is valuable for optimizing flight operations considering the environmental impact of aircraft engine nvPM emissions. When the relevant aircraft flights, engine parameters, and engine nvPM emission databases embedded in the integrated method for any airport are established, the method is feasible to assess the sources and trends of aircraft engine nvPM emissions during LTO cycles at any time period in the airport.

Reduction of Nonvolatile Particulate Matter Emissions of a Commercial Turbofan Engine at the Ground Level from the Use of a Sustainable Aviation Fuel Blend.

Nonvolatile particulate matter (nvPM) emissions from aircraft turbine engines deteriorate air quality and contribute to climate change. These emissions can be reduced using sustainable aviation fuels (SAFs). Here, we investigate the effects of a 32% SAF blend with fossil fuel on particle size distributions and nvPM emission indices of a widely used turbofan engine. The experiments were conducted in a test cell using a standardized sampling and measurement system. The geometric mean diameter (GMD) increased with thrust from ∼8 nm at idle to ∼40 nm at take-off, and the geometric standard deviation (GSD) was in the range of 1.74-2.01. The SAF blend reduced the GMD and GSD at each test point. The nvPM emission indices were reduced most markedly at idle by 70% in terms of nvPM mass and 60% in terms of nvPM number. The relative reduction of nvPM emissions decreased with the increasing thrust. The SAF blend reduced the nvPM emissions from the standardized landing and take-off cycle by 20% in terms of nvPM mass and 25% in terms of nvPM number. This work will help develop standardized models of fuel composition effects on nvPM emissions and evaluate the impacts of SAF on air quality and climate.

Assessment of a regulatory measurement system for the determination of the non-volatile particulate matter emissions from commercial aircraft engines

The SAE International has published Aerospace Information Report (AIR) 6241 which outlined the design and operation of a standardized measurement system for measuring non-volatile particulate matter (nvPM) mass and number emissions from commercial aircraft engines. Prior to this research, evaluation of this system by various investigators revealed differences in nvPM mass emissions measurement on the order of 15–30% both within a single sampling system and between two systems operating in parallel and measuring nvPM mass emissions from the same source. To investigate this issue, the U. S. Environmental Protection Agency in collaboration with the U. S. Air Force's Arnold Engineering Development Complex initiated the VAriable Response In Aircraft nvPM Testing (VARIAnT) research program to compare nvPM measurements within and between AIR-compliant sampling systems used for measuring combustion aerosols generated both by a 5201 Mini-CAST soot generator and a J85-GE-5 turbojet engine burning multiple fuels. The VARIAnT research program has conducted four test campaigns to date. The first campaign (VARIAnT 1) compared two essentially identical commercial versions of the sampling system while the second campaign (VARIAnT 2) compared a commercial system to the custom-designed Missouri University of Science and Technology's North American Reference System (NARS) built to the same specifications. Comparisons of nvPM particle mass (i.e., black carbon), number, and size were conducted in both campaigns. Additionally, the sensitivity to variation in system operational parameters was evaluated in VARIAnT 1. Results from both campaigns revealed agreement of about 12% between the two sampling systems, irrespective of manufacturer, in all aspects except for black carbon determination. The major source of measurement differences (20–70%) was due to low BC mass measurements made by the Artium Technologies LII-300 as compared to the AVL 483 Micro-Soot Sensor, the Aerodyne Cavity Attenuated Phase Shift (CAPS PMSSA) monitor, and the thermal-optical reference method for elemental carbon (EC) determination, which was used as the BC reference.

Comparison of standardized sampling and measurement reference systems for aircraft engine non-volatile particulate matter emissions

The International Civil Aviation Organization has established new regulatory standards for emissions certification of non-volatile particulate matter (nvPM) from aircraft turbine engines. The adoption of the nvPM emissions regulatory standards required development of a standardized sampling and measurement methodology, and rigorous testing. Three reference systems for aircraft engine nvPM emissions measurement, compliant with the specifications for the standardized methodology, were independently developed. This paper reports the results of the first inter-comparison of these three reference systems using a CFM56-7B26/3 aircraft engine to establish repeatability and intermediate precision of the sampling and measurement systems as part of the multi-agency international collaborative projects: Aviation-Particle Regulatory Instrumentation Demonstration Experiment (A-PRIDE) 5/Studying, sAmpling and Measuring of aircraft ParticuLate Emissions (SAMPLE) III - SC03. The instruments used in the three reference systems recorded nvPM mass and number concentration, which were converted to their respective emission indices for comparison. The reference systems generally agreed to within 15% of the average nvPM number emission index and 30% of the average nvPM mass emission index. The only exception was for the nvPM mass instruments, which exhibited a higher variation as the concentration levels approached the limit of detection. The additional measured particle size distributions could be approximated to lognormal distributions with the geometric mean diameter ranging from 15 nm to 38 nm, and the geometric standard deviation varying between 1.53 and 1.92. The results from this study are a benchmark for the variability in standardized sampling and measurement systems for measuring aircraft engine nvPM emissions.

Nonvolatile Particulate Matter Emissions of a Business Jet Measured at Ground Level and Estimated for Cruising Altitudes.

Business aviation is a relatively small but steadily growing and little investigated emission source. Regarding emissions, aircraft turbine engines rated at and below 26.7 kN thrust are certified only for visible smoke and are excluded from the nonvolatile particulate matter (nvPM) standard. Here, we report nvPM emission characteristics of a widely used small turbofan engine determined in a ground test of a Dassault Falcon 900EX business jet. These are the first reported nvPM emissions of a small in-production turbofan engine determined with a standardized measurement system used for emissions certification of large turbofan engines. The ground-level measurements together with a detailed engine performance model were used to predict emissions at cruising altitudes. The measured nvPM emission characteristics strongly depended on engine thrust. The geometric mean diameter increased from 17 nm at idle to 45 nm at take-off. The nvPM emission indices peaked at low thrust levels (7 and 40% take-off thrust in terms of nvPM number and mass, respectively). A comparison with a commercial airliner shows that a business jet may produce higher nvPM emissions from flight missions as well as from landing and take-off operations. This study will aid the development of emission inventories for small aircraft turbine engines and future emission standards.

The effects of biodiesels on semivolatile and nonvolatile particulate matter emissions from a light-duty diesel engine

Semivolatile organic compounds (SVOCs) represent a dominant category of secondary organic aerosol precursors that are increasingly included in air quality models. In the present study, an experimental system was developed and applied to a light-duty diesel engine to determine the emission factors of particulate SVOCs (pSVOCs) and nonvolatile particulate matter (PM) components at dilution ratios representative of ambient conditions. The engine was tested under three steady-state operation modes, using ultra-low-sulfur diesel (ULSD), three types of pure biodiesels and their blends with ULSD. For ULSD, the contribution of pSVOCs to total particulate organic matter (POM) mass in the engine exhaust ranged between 21 and 85%. Evaporation of pSVOCs from the diesel particles during dilution led to decreases in the hydrogen to carbon ratio of POM and the PM number emission factor of the particles. Substituting biodiesels for ULSD could increase pSVOCs emissions but brought on large reductions in black carbon (BC) emissions. Among the biodiesels tested, tallow/used cooking oil (UCO) biodiesel showed advantages over soybean and canola biodiesels in terms of both pSVOCs and nonvolatile PM emissions. It is noteworthy that PM properties, such as particle size and BC mass fraction, differed substantially between emissions from conventional diesel and biodiesels.

Evaluation of Non-volatile Particulate Matter Emission Characteristics of an Aircraft Auxiliary Power Unit with Varying Alternative Jet Fuel Blend Ratios

The aviation industry is increasingly focused on the development of sustainable alternative fuels to augment and diversify fuel supplies while simultaneously reducing its environmental impact. The impact of airport operations on local air quality and aviation-related greenhouse gas emissions on a life cycle basis have been shown to be reduced with the use of alternative fuels. However, the evaluation of incremental variations in fuel composition of a single alternative fuel on the production of non-volatile particulate matter (nvPM) emissions has not been explored. This is critical to understanding the emission profile for aircraft engines burning alternative fuels and the impact of emissions on local air quality and climate change. A systematic evaluation of nvPM emissions from a GTCP85 aircraft auxiliary power unit (APU) burning 16 different blends of used cooking oil (UCO)-derived hydroprocessed esters and fatty acids (HEFA)-type alternative fuel with a conventional Jet A-1 baseline fuel was performed....

Characterization of Gaseous and Particulate Emissions From a Turboshaft Engine Burning Conventional, Alternative, and Surrogate Fuels

The effect of fuel composition on the operability and gaseous and particulate matter (PM) emissions of an Allison T63-A-700 turboshaft engine operated at four power settings was investigated in this effort. Testing was performed with a specification JP-8, a synthetic paraffinic kerosene, and four two-component surrogate mixtures that comprise compound classes within current and future alternative fuels. Comparable engine operability was observed for all fuels during this study. Major gaseous emissions were only slightly effected, with trends consistent with those expected based on the overall hydrogen content of the fuels. However, minor hydrocarbon and aldehyde emissions were significantly more sensitive to the fuel chemical composition. Linear correlations between speciated hydrocarbon and aldehyde emissions were observed over the full engine operating range for the fuels tested. The corresponding slopes were dependent on the fuel composition, indicating that fuel chemistry affects the selectivity to specific decomposition pathways. Unburned fuel components were observed in the engine exhaust during operation with all fuels, demonstrating that completely unreacted fuel compounds can pass through the high temperature/pressure combustion zone. Nonvolatile PM emissions (soot) were strongly affected by the fuel chemical composition. Paraffinic fuels produced significantly lower PM number and mass emissions relative to aromatic-containing fuels, with the paraffin structure affecting sooting propensity. The observations are consistent with those expected based on simplified soot formation mechanisms, where fuels with direct precursors for polycyclic aromatic hydrocarbon formation have higher PM formation rates. The effect of a specific chemical structure on the relative PM production is important as this would not be evident when comparing sooting tendencies of fuels based on bulk fuel properties. All fuels produced similar single log-normal size distributions of soot, with higher sooting fuels producing larger mean diameter particles. It is hypothesized that the controlling growth and formation mechanisms for PM production are similar for different fuel chemistries in this regime, with composition primarily affecting soot formation rate. This hypothesis was supported by preliminary TEM analyses that showed similar soot microstructures during operation with either conventional JP-8 or alternative fuels. Overall, this study provides additional and improved insight into the effect of fuel chemical composition on complex combustion chemistry and emissions propensity in a gas turbine engine, and can assist with the successful development of predictive modeling tools.

Methodology to Estimate Particulate Matter Emissions from Certified Commercial Aircraft Engines

Today, about one-fourth of U.S. commercial service airports, including 41 of the busiest 50, are either in nonattainment or maintenance areas per the National Ambient Air Quality Standards. U.S. aviation activity is forecasted to triple by 2025, while at the same time, the U.S. Environmental Protection Agency (EPA) is evaluating stricter particulate matter (PM) standards on the basis of documented human health and welfare impacts. Stricter federal standards are expected to impede capacity and limit aviation growth if regulatory mandated emission reductions occur as for other non-aviation sources (i.e., automobiles, power plants, etc.). In addition, strong interest exists as to the role aviation emissions play in air quality and climate change issues. These reasons underpin the need to quantify and understand PM emissions from certified commercial aircraft engines, which has led to the need for a methodology to predict these emissions. Standardized sampling techniques to measure volatile and nonvolatile PM emissions from aircraft engines do not exist. As such, a first-order approximation (FOA) was derived to fill this need based on available information. FOA1.0 only allowed prediction of nonvolatile PM. FOA2.0 was a change to include volatile PM emissions on the basis of the ratio of nonvolatile to volatile emissions. Recent collaborative efforts by industry (manufacturers and airlines), research establishments, and regulators have begun to provide further insight into the estimation of the PM emissions. The resultant PM measurement data-sets are being analyzed to refine sampling techniques and progress towards standardized PM measurements. These preliminary measurement datasets also support the continued refinement of the FOA methodology. FOA3.0 disaggregated the prediction techniques to allow for independent prediction of nonvolatile and volatile emissions on a more theoretical basis. The Committee for Aviation Environmental Protection of the International Civil Aviation Organization endorsed the use of FOA3.0 in February 2007. Further commitment was made to improve the FOA as new data become available, until such time the methodology is rendered obsolete by a fully validated database of PM emission indices for today’s certified commercial fleet. This paper discusses related assumptions and derived equations for the FOA3.0 methodology used worldwide to estimate PM emissions from certified commercial aircraft engines within the vicinity of airports

Postcombustion Evolution of Soot Properties in an Aircraft Engine

Recent measurements have suggested that soot properties can evolve downstream of the combustor, changing the characteristics of aviation particulate matter emissions and possibly altering the subsequent atmospheric impacts. This paper addresses the potential for the postcombustion thermodynamic environment to influence aircraft nonvolatile particulate matter emissions. Microphysical processes and interactions with gas phase species have been modeled for temperatures and pressures representative of in-service engines. Time-scale arguments are used to evaluate the relative contributions that various phenomena may make to the evolution of soot, including coagulation growth, ion-soot attachment, and vapor condensation. Then a higher-fidelity microphysics kinetic is employed to estimate the extent to which soot properties evolve as a result of these processes. Results suggest that limited opportunities exist for the modification of the size distribution of the soot, its charge distribution, or its volatile content, leading to the conclusion that the characteristics of the turbine and nozzle of an aircraft engine have little or no influence on aircraft nonvolatile emissions. Combustor processing determines the properties of soot particulate matter emissions from aircraft engines, setting the stage for interactions with gaseous emissions and development as cloud condensation nuclei in the exhaust plume.