Particulate Emissions Research Articles

Effects of Lean Burn on Combustion and Emissions of a DISI Engine Fueled with Methanol–Gasoline Blends

Methanol has significant potential as an alternative fuel for internal combustion engines. Using methanol–gasoline blends with lean-burn technology in traditional spark-ignition engines can enhance fuel economy and reduce emissions. This paper investigates the effects of lean burn on the combustion and emissions in a commercial direct-injection gasoline engine fueled with methanol–gasoline blends. The lean-burn mode is adjusted by controlling the injection strategy. The results show that homogeneous lean burn (HLB) has earlier combustion phase and better power performance when the excess air ratio (λ) is less than 1.3, while its combustion phase extends more than stratified lean burn (SLB) when λ exceeds 1.4. Both lean-burn modes achieve optimal fuel economy at λ = 1.2–1.3. Under stable conditions, BSFC decreases with higher methanol blending ratios, with SLB being more economical at low blending ratios and HLB at higher ratios. The lowest HC and particulate matter emissions for both modes are achieved around λ = 1.3. SLB has lower NOX emissions when λ < 1.3, while HLB shows lower NOX emissions when λ > 1.3. The particulate size distribution is bimodal for blending lean-burn conditions, with SLB having the highest nucleation mode peak and HLB the highest accumulation mode peak. M20 (20% volume of methanol) corresponds to the highest particle emissions under lean-burn conditions. This study can provide a deeper understanding of methanol–gasoline blending lean burn, and provide a reference for emission control of spark-ignition engines.

Relationship between Exhaled Aerosol and Carbon Dioxide Emission Across Respiratory Activities.

Respiratory particles produced during vocalized and nonvocalized activities such as breathing, speaking, and singing serve as a major route for respiratory pathogen transmission. This work reports concomitant measurements of exhaled carbon dioxide volume (VCO2) and minute ventilation (VE), along with exhaled respiratory particles during breathing, exercising, speaking, and singing. Exhaled CO2 and VE measured across healthy adult participants follow a similar trend to particle number concentration during the nonvocalized exercise activities (breathing at rest, vigorous exercise, and very vigorous exercise). Exhaled CO2 is strongly correlated with mean particle number (r = 0.81) and mass (r = 0.84) emission rates for the nonvocalized exercise activities. However, exhaled CO2 is poorly correlated with mean particle number (r = 0.34) and mass (r = 0.12) emission rates during activities requiring vocalization. These results demonstrate that in most real-world environments vocalization loudness is the main factor controlling respiratory particle emission and exhaled CO2 is a poor surrogate measure for estimating particle emission during vocalization. Although measurements of indoor CO2 concentrations provide valuable information about room ventilation, such measurements are poor indicators of respiratory particle concentrations and may significantly underestimate respiratory particle concentrations and disease transmission risk.

Assessment of the skin contamination dose coefficients for 252Cf radionuclide: Monte Carlo approach

Handling the 252Cf radionuclide source poses a potential hazard of skin surface contamination in case of an unexpected occurrence. Consequently, there is a growing need to establish precise dose conversion coefficients tailored to each type of emitted primary particle and various radionuclides. Nevertheless, the current body of literature does not provide specific data or methodologies for evaluating skin contamination dose and its associated coefficients, particularly with regard to the 252Cf source. Thus, this study aims to quantify the dose rate received by the skin and its associated coefficients after contamination scenario. Utilizing the established MCNPX environment, the Equivalent dose rate and Absorbed dose, along with Skin contamination dose coefficient (SCDC), have been calculated within the skin tissue. Two methodologies, specifically Watt Fission distribution and the Doppler Effect, are proposed to analyze particle spectra within skin phantom, enabling the calculation of Equivalent dose rate. In accordance with ICRP recommendations regarding the optimal depth for assessing skin doses, the designated scoring volume within the skin is located between depths of 50–100 μm. This volume is tasked with evaluating the dose. The SCDC results were entirely consistent with previously published data from MCNPX, with statistical uncertainties of less than 15%, demonstrating the efficacy of the methodologies employed in this study. This research presents an innovative method for generating data related to skin contamination doses. The novel outcomes in the current research facilitate the assessment of skin dose contamination for the targeted radionuclides and radiotherapy purposes due to staff oversight and radiobiological effects.

Multipartite Correlations in Parikh-Wilczek Non-Thermal Spectrum.

In this study, we systematically investigate the multipartite correlations in the process of black hole radiation via the Parikh-Wilczek tunneling model. We examine not only the correlations among Hawking radiations but also the correlations between the emissions and the remainder of the black hole. Our findings indicate that the total correlation among emitted particles continues to increase as the black hole evaporates. Additionally, we observe that the bipartite correlation between the emissions and the remainder of the black hole initially increases and then decreases, while the total correlation of the entire system monotonically increases. Finally, we extend our analysis to include quantum correction and observe similar phenomena. Through this research, we aim to elucidate the mechanism of information conservation in the black hole information paradox.

Enhancing understanding of particle emissions from lithium-ion traction batteries during thermal runaway: An overview and challenges

Particle emissions released by lithium-ion traction batteries (LIBs) during thermal runaway (TR) are considered to be one of the fire hazard sources for new energy vehicles. Moreover, the particle emissions may persist in the environment and cause damage even after a fire is extinguished. Therefore, the formation mechanisms of the particle emissions from LIBs during TR are summarized firstly in this review. Effects of influencing factors on particle emission characteristics and biotoxicity are also explored. Furthermore, simulation models of LIB particle emissions are summarized. Particle emissions calculated for 2021 to 2023 are presented, and particle emissions from 2024 to 2030 are predicted. Finally, the existing research results and the problems with LIB particle emissions are summarized, and future research challenges and directions are prospected. This review aims to evoke interest in particle emissions from lithium-ion traction batteries during TR and provide a reference for suppressing and managing particle emissions to improve the safety of LIBs and mitigate environmental hazards.

Towards dynamical low-rank approximation for neutrino kinetic equations. Part I: Analysis of an idealized relaxation model

Dynamical low-rank approximation (DLRA) is an emerging tool for reducing computational costs and provides memory savings when solving high-dimensional problems. In this work, we propose and analyze a semi-implicit dynamical low-rank discontinuous Galerkin (DLR-DG) method for the space homogeneous kinetic equation with a relaxation operator, modeling the emission and absorption of particles by a background medium. Both DLRA and the discontinuous Galerkin (DG) scheme can be formulated as Galerkin equations. To ensure their consistency, a weighted DLRA is introduced so that the resulting DLR-DG solution is a solution to the fully discrete DG scheme in a subspace of the standard DG solution space. Similar to the standard DG method, we show that the proposed DLR-DG method is well-posed. We also identify conditions such that the DLR-DG solution converges to the equilibrium. Numerical results are presented to demonstrate the theoretical findings.

A Review of Alternative Aviation Fuels

One of the most promising mid-term solutions for reducing GHG emissions from the aviation sector is alternative aviation fuels, especially sustainable aviation fuels (SAFs). Regulations imposed by the Fit for 55 package to use 38% of SAFs until 2050 require a comprehensive analysis of SAFs and production pathway development with increased blending limits of alternative fuel. Within this review, a summary of key aspects of alternative aviation fuels is presented. The review contains a description of the certification process and certified production pathways with an analysis of feedstocks used for SAF production. SAF emissions also have been analyzed based on available research. SAFs reduce particulate matter emissions significantly, even by 70%, compared to fossil fuels. The emission of gaseous exhaust compounds, such as carbon monoxide, unburned hydrocarbons and nitrogen oxides, also is discussed. Alternative aviation fuels have a lower LCA compared to conventional aviation fuel and the LCAs of specific feedstocks are presented.

Characterization of Particulate Emissions From Thermal Runaway of Lithium-Ion Cells

Abstract Over the past decade, there has been a significant acceleration in the adoption of lithium-ion (Li-ion) batteries for various applications, ranging from portable electronics to automotive, defense, and aerospace applications. Lithium-ion batteries are the most used energy storage technologies due to their high energy densities and capacities. However, this battery technology is a potential safety hazard under off-nominal conditions, which may result in thermal runaway events. Such events can release toxic gaseous and particulate emissions, posing a severe risk to human health and the environment. Particulate emissions from the failure of two different cell chemistries—lithium iron phosphate (LFP) and nickel manganese cobalt oxide (NMC)—were studied. Experiments were conducted at multiple states of charge (SOC), and three repeats were performed at each SOC for each cell chemistry to examine the repeatability/variability of these events. Particulate emissions were characterized in terms of particulate matter mass (PM2.5), black carbon, and particle number (PN)/size. Failure of a single cell led to a significant release of particulate emissions, with peak emission levels being higher at the higher SOCs. A high level of variability was observed for a specific SOC for LFP cells, while NMCs exhibited relatively less variability. In general, much higher particulate emissions were observed for NMCs compared to LFPs at each SOC. For NMCs at 100% SOC, peak PN levels were ∼2.5 × 10+09 particles/cc (part/cc), and black carbon levels were ∼60 mg/m3. For LFPs at 100% SOC, peak PN levels were ∼9.0 × 10+08 part/cc, and black carbon levels were 2.5 mg/m3.

Numerical Investigation of Effusion Cooling Air Influence On the Co Emissions for a Single-Sector Aero-Engine Model Combustor

Abstract Stricter aviation emissions regulations have led to the desire for lean-premixed-vaporized combustors over rich-quench-lean burners. While this operation mode is beneficial for reducing NOx and particulate emissions, the interaction of the flame and hot exhaust gases with the cooling flow results in increased CO emissions. Predicting CO in computational fluid dynamics (CFD) simulations remains challenging. To assess current model performance under practically relevant conditions, Large-Eddy Simulation (LES) of a lab-scale effusion cooling test rig is performed. Flamelet-based manifolds, in combination with the Artificial Thickened Flame (ATF) approach, are utilized to model the Turbulence-Chemistry Interaction (TCI) in the test rig with detailed chemical kinetics at reduced computational costs. Heat losses are considered via exhaust gas recirculation (EGR). Local transport effects in CO emissions are included through an additional transport equation. Additionally, a Conjugate Heat Transfer (CHT) simulation is performed for good estimations of the thermal boundary conditions. Extensive validation of this comprehensive model is conducted using the available experimental dataset for the studied configuration. Subsequently, model sensitivities for predicting CO are assessed, including the progress variable definition and the formulation of the CO source term in the corresponding transport equation. To investigate the flame thickening influence in the calculated CO, an ATF-postprocessing correction is further developed. Integrating multiple sophisticated pollutant submodels and evaluating their sensitivity offers insights for future investigations into modeling CO emissions in aero-engines and stationary gas turbines.

An active-type dust collector that reduces brake wear particle (BWP) emission

An active-type dust collector that reduces brake wear particle (BWP) emission

Pollutant Emissions and Oxidative Potentials of Particles from the Indoor Burning of Biomass Pellets.

Residential solid fuel combustion significantly impacts air quality and human health. Pelletized biomass fuels are promoted as a cleaner alternative, particularly for those who cannot afford the high costs of gas/electricity, but their emission characteristics and potential effects remain poorly understood. The present laboratory-based study evaluated pollution emissions from pelletized biomass burning, including CH4 (methane), NMHC (nonmethane hydrocarbon compounds), CO, SO2, NOx, PM2.5 (particulate matter with an aerodynamic diameter ≤2.5 μm), OC (organic carbon), EC (element carbon), PAHs (polycyclic aromatic hydrocarbons), EPFRs (environmentally persistent free radicals), and OP (oxidative potential) of PM2.5, and compared with those from raw biomass burning. For most targets, except for SO2 and NOx, the mass-based emission factors for pelletized biomass were 62-96% lower than those for raw biomass. SO2 and NOx levels were negatively correlated with other air pollutants (p < 0.05). Based on real-world daily consumption data, this study estimated that households using pelletized biomass could achieve significant reductions (51-95%) in emissions of CH4, NMHC, CO, PM2.5, OC, EC, PAHs, and EPFRs compared to those using raw biomass, while the differences in emissions of NOx and SO2 were statistically insignificant. The reduction rate of benzo(a)pyrene-equivalent emissions was only 16%, much lower than the reduction in the total PAH mass (78%). This is primarily attributed to the more PAHs with high toxic potentials, such as dibenz(a,h)anthracene, in the pelletized biomass emissions. Consequently, impacts on human health associated with PAHs might be overestimated if only the mass of total PAHs was counted. The OP of particles from the pellet burning was also significantly lower than that from raw biomass by 96%. The results suggested that pelletized biomass could be a transitional substitution option that can significantly improve air quality and mitigate human exposure.

Emissions from Ethiopian clinker-producing cement factories and their impact on community well-being

In the realm of cement production, clinker-producing factories emerge as both energy and material-intensive entities, emitting a substantial array of primary pollutants into the environment compared to their non-clinker-producing counterparts. This study investigates the emissions from clinker-producing cement factories in Ethiopia and their impact on community well-being. We specifically focus on particulate matter (PM2.5 and PM10) and gaseous emissions (CO2, N2O, SO2) measured at various units within the cement factories and nearby residential areas. The study area includes major industry players such as Derba Cement plant, National Cement Share Company, Mugher Cement Enterprise, Ethio Cement P.L.C, Dangote Cement plant, Habesha Cement, and Pioneers Cement Share Company. The pollutants were measured using standard instruments, including the portable Aeroqual Series-500 Gas Sensor (S-500) for both particulate matters and gases, with sampling conducted from August 1, 2021, to January 30, 2022. We analyzed the potential health impacts of these emissions, particularly respiratory diseases, among different age groups. The findings underscore the urgent need for regulatory measures to mitigate cement particulate emissions and protect community health. Our study provides valuable insights into the environmental and health risks associated with clinker-producing cement factories in Ethiopia, contributing to the broader field of environmental science.

Using DPF to Control Particulate Matter Emissions from Ships to Ensure the Sustainable Development of the Shipping Industry

PM (particulate matter) emissions from ships are the main sources of marine atmosphere pollution. Controlling the emissions of particulate matter from ships is related to the sustainable development of the shipping industry. To reduce PM emissions from marine four-stroke diesel engines, DPFs are effective. Our results show that DPF had more than 90% capturing efficiency for both the number and mass emissions of PM, and the capturing efficiency for the accumulation mode was higher than that of the nuclear mode. DPF can also significantly reduce the chemical components of PM in marine diesel exhaust gas. The removal efficiencies for OC and EC were 89.7–91.6% and 84.8–92.8%, respectively, with each particle size range showing over 80% efficiency. SO42− was the ion with the highest content, followed by NH4+, NO3−, Na+, NO2−, and Cl−, with their reduced proportions remaining consistent with the removal efficiency of particulate matter. DPF can also effectively reduce PAH content and toxicity. The use of DPF can greatly improve the impact of ship emissions on the marine atmospheric environment. The appropriate DPF with the best performance can be selected according to the exhaust parameters and particle size distributions with different characteristics.

Demonstration of aneutronic p-11B reaction in a magnetic confinement device

Aneutronic fusion using commonly available fuel such as hydrogen and boron 11 (11B) is one of the most attractive potential energy sources. On the other hand, it requires 30 times higher temperature than deuterium–tritium fusion in a thermonuclear fusion reactor condition. Development of techniques to realize its potential for the experimental capability to produce proton-boron 11 (p-11B) fusion in the magnetically confined fusion device using neutral beam injection is desired. Here we report clear experimental exploration and measurements of p-11B fusion reactions supported by intense hydrogen beams and impurity powder dropper installed in the magnetic confinement plasma Large Helical Device. We measured a significant amount of fusion alpha particle emission using a custom designed alpha particle detector based on a passivated implanted planar silicon detector. Intense negative-ion-based hydrogen beam injectors created a large population of up to 160 keV energetic protons to react with the boron-injected plasma. The p-11B alpha particles having MeV energy were measured with the alpha particle detector which gave a fusion rate in a good agreement with the global p-11B alpha emission rate calculated based on classical confinement of energetic proton, using experimentally obtained plasma parameters.

Particulate matter emissions from open pit mines; measurement methodologies, instruments, and research undertaken

Particulate matter is one of the primary pollutants in open pit mining operations. Measurements must be taken to control particulate matter created during open pit mining activities and to compare them to the regulatory limits. Numerous studies have been undertaken to estimate particulate matter emissions produced by open pit mining. It was discovered that the research were largely conducted on coal mines (69.4%), with little study done in other mining types. Research studies on particulate matter estimation took into consideration mostly machine characteristics (loader bucket volume, truck capacity, number of truck wheels etc.) and atmospheric conditions (air temperature, wind speed, relative humidity etc.). This study emphasizes on particulate matter measurement methods along with other measuring parameters and equipment for particulate matter estimation (TSP, PM10, PM4, PM2.5, and PM1).

Rural Roads, Farm Labor Exits, and Crop Fires

Even as policymakers seek to encourage economic development by addressing misallocation due to frictions in labor markets, the associated production externalities—such as air pollution—remain unexplored. Using a regression discontinuity design, we show access to rural roads increases agricultural fires and particulate emissions. Farm labor exits are a likely mechanism: rural roads cause movement of workers out of agriculture and induce farmers to use fire—a labor-saving but polluting technology—to clear agricultural residue or to make harvesting less labor-intensive. Overall, the adoption of fires due to rural roads increases infant mortality rates by 5.5 percent in downwind locations. (JEL D62, J43, O13, O18, Q12, Q51, Q53)

Wildfire combustion emission inventory in Southwest China (2001–2020) based on MODIS fire radiative energy data

Wildfires, a persistent environmental menace, are a significant source of harmful gases and particulate emissions. This study leverages the fire radiative power (FRP) method to delineate a comprehensive wildfire emission inventory for Southwest China from 2001 to 2020. Daily fire radiative power data derived from 1 km MODIS Thermal Anomalies/Fire products (MOD14/MYD14) were used to calculate the FRE and combusted biomass. Available emission factors were assigned to three biomass burn types: forest, grass, and shrub fires. Over the span of two decades, we have compiled data and estimated the annual emissions of carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), sulfur dioxide (SO2), ammonia (NH3), nitrogen oxides (NOx), total particulate matter (TPM), black carbon (BC), organic carbon (OC), and non-methane volatile organic compounds (NMVOCs) to be 9809.13, 566.82, 25.79, 5.37, 12.25, 16.67, 133.53, 4.16, 41.81, and 97.23 Gg per year (Gg yr−1), respectively. In terms of fire type, forest fires accounted for the largest portion of total CO2 emissions (59.23%), with grass fires and shrub fires coming in second and third, accounting for 20.41% and 20.36%, respectively. Geographically, Yunnan Province were identified as the major contributor in Southwest China, accounting for 69.67% of the total emissions. Temporally, the maximum emission occurred in 2010 (24263.33 Gg), and the minimum emission occurred in 2017 (2917.66 Gg). And the emissions were mainly concentrated in February (23.33%), March (25.52%), and April (22.61%), which accounted for nearly three-fourths of the total emissions. The results of this study are much higher than those obtained by the burned area method, almost three times as high. In contrast, the results of this study are close to the fire emission data from the GFED4s and GFASv1.2 and QFEDv2.5r1 databases.

Effect of Vocalization on Human Aerosol Dynamics: Whispering Produces More Aerosols than Speaking

ObjectivesSound pressure and exhaled flow have been identified as important factors associated with higher particle emissions. The aim of this study was to assess how different vocalizations affect the particle generation independently from other factors. DesignExperimental study MethodsThirty-three experienced singers repeated two different sentences in normal loudness and whispering. The first sentence consisted mainly of consonants like /k/ and /t/ as well as open vowels, while the second sentence also included the /s/ sound and contained primarily closed vowels. The particle emission was measured using condensation particle counter (CPC, 3775 TSI Inc.) and aerodynamic particle sizer (APS, 3321 TSI Inc.). The CPC measured particle number concentration for particles larger than 4 nm and mainly reflects the number of particles smaller than 0.5 µm since these particles dominate total number concentration. The APS measured particle size distribution and number concentration in the size range of 0.5 – 10 µm and data were divided into > 1 µm and < 1 µm particle size ranges. Generalized linear mixed effects models were constructed to assess the factors affecting particle generation. ResultsWhispering produced more particles than speaking and sentence 1 produced more particles than sentence 2 while speaking. Sound pressure level had effect on particle production independently from vocalization. The effect of exhaled airflow was not statistically significant. ConclusionsBased on our results the type of vocalization has a significant effect on particle production independently from other factors such as sound pressure level.

Role of primary drivers leading to emission reduction of major air pollutants and CO2 from global power plants

Electricity production is a significant source of air pollution. Various factors, including electricity demand, generation efficiency, energy mix, and end-of-pipe control measures, are responsible for the emission changes during electricity generation. Although electricity production more than doubled from 1990 to 2017, air pollutant emissions showed a moderate increase or decrease, which was attributed to mitigating drivers such as increased clean energy use, improved power generation efficiency, and widespread installation of end-of-pipe control facilities. The absence of these mitigating drivers would have increased CO2, fine particulate matter (PM2.5), black carbon, SO2, and NOx emissions in 2017 by 165 %, 403 %, 1070 %, 614 %, and 274 % than their actual levels, respectively. The improved electricity generation efficiency reduced potential CO2, PM2.5, SO2, and NOx emissions by 30 %, 295 %, 119 %, and 52 % compared to actual emissions, respectively. Meanwhile, the installation of end-of-pipe facilities reduced potential SO2 and PM2.5 emissions by 34.7 and 4.0 Tg, respectively. Considerable differences in emissions among countries were found to be attributable to their differences in electricity demand and the implementation of local mitigating polices.

A comparison of population-level exposure and equity tradeoffs across strategies to reduce fine particulate matter emissions from transportation sources in the northeastern US

BackgroundMany climate mitigation policies to reduce transportation emissions have public health benefits related to ambient air pollution. However, few health analyses consider the equity implications of alternative policies. Equity can be conceptualized in many different ways that may be relevant to communities, decision-makers, and other stakeholders. ObjectivesTo evaluate alternative transportation emissions reduction scenarios across the northeastern United States considering population exposure reductions and multiple equity constructs. MethodsWe developed four quantitative indicators reflecting equity constructs that aligned with stakeholder perspectives, including racial/ethnic exposure inequities, proportion of benefits in environmental justice communities, distribution of benefits among participating states, and rural/urban share of benefits. We analyzed numerous transportation emissions reduction scenarios for directly emitted fine particulate matter (primary PM2.5) covering 12 Northeast states and the District of Columbia. We used the Community Multiscale Air Quality model with the decoupled direct method to estimate the reduction in population-weighted primary PM2.5 exposure and the impact on equity for each scenario. ResultsScenarios that yielded greater reductions in population-weighted primary PM2.5 exposure generally emphasized emissions reductions in urban areas or states with large urban centers, with a more than threefold difference in benefits across scenarios. The higher exposure-benefit scenarios typically also had greater reductions in racial/ethnic exposure inequities but led to higher between-state or rural/urban inequality. Scenarios that targeted uniform percentage emission reductions from light or heavy-duty trucks best addressed rural/urban inequalities but led to the smallest reductions in racial/ethnic inequity. ConclusionThere are intrinsic tradeoffs among equity constructs, where focusing resources on distributing benefits across states or between urban and rural populations could come at the expense of less reduction in racial/ethnic exposure inequities or in environmental justice communities. Future health benefits analyses should incorporate multiple equity indicators that reflect different stakeholder perspectives and articulate the underlying constructs and tradeoffs.