Particulate matter (PM) emissions from stationary combustion sources burning coal, fuel oil, biomass, and waste, and PM from internal combustion (IC) engines burning gasoline and diesel, are a significant source of primary particles smaller than 2.5 μm (PM2.5) in urban areas. Combustion-generated particles are generally smaller than geologically produced dust and have unique chemical composition and morphology. The fundamental processes affecting formation of combustion PM and the emission characteristics of important applications are reviewed. Particles containing transition metals, ultrafine particles, and soot are emphasized because these types of particles have been studied extensively, and their emissions are controlled by the fuel composition and the oxidant-tem-perature-mixing history from the flame to the stack. There is a need for better integration of the combustion, air pollution control, atmospheric chemistry, and inhalation health research communities. Epidemiology has demonstrated t...

https://www.tandfonline.com/doi/pdf/10.1080/10473289.2000.10464197

Combustion aerosols: factors governing their size and composition and implications to human health.

Different on-line submicron particle sizing techniques report different “equivalent diameters.” For example, differential mobility analyzers (DMAs) report electrical mobility diameter (dm ), while a number of recently developed instruments (such as the Aerodyne aerosol mass spectrometer, or AMS) measure vacuum aerodynamic diameter (dva ). Particle density and physical morphology (shape) have important effects on diameter measurements. Here a framework is presented for combining the information content of different equivalent diameter measurements into a single coherent mathematical description of the particles. We first present a review of the mathematical formulations used in the literature and their relationships. We then show that combining dm and dva measurements for the same particle population allows the placing of constraints on particle density, dynamic shape factor (x), and fraction of internal void space. The amount of information that can be deduced from the combination of dm and dm measurement...

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Particle Morphology and Density Characterization by Combined Mobility and Aerodynamic Diameter Measurements. Part 1: Theory

Chemical characterization of particulate emissions from diesel engines: A review

The development of four-stroke, spark-ignition engines that are designed to inject gasoline directly into the combustion chamber is an important worldwide initiative of the automotive industry. The thermodynamic potential of such engines for significantly enhanced fuel economy, transient response and cold-start hydrocarbon emission levels has led to a large number of research and development projects that have the goal of understanding, developing and optimizing gasoline direct-injection (GDI) combustion systems. The processes of fuel injection, spray atomization and vaporization, charge cooling, mixture preparation and the control of in-cylinder air motion are all being actively researched, and this work is reviewed in detail and analyzed. The new technologies such as high-pressure, common-rail, gasoline injection systems and swirl-atomizing gasoline fuel injectors are discussed in detail, as these technologies, along with computer control capabilities, have enabled the current new examination of an old objective; the direct-injection, stratified-charge (DISC), gasoline engine. The prior work on DISC engines that is relevant to current GDI engine development is also reviewed and discussed.

The fuel economy and emission data for actual engine configurations are of significant importance to engine researchers and developers. These data have been obtained and assembled for all of the available GDI literature, and are reviewed and discussed in detail. The types of GDI engines are arranged in four classifications of decreasing complexity, and the advantages and disadvantages of each class are noted and explained. Emphasis is placed upon consensus trends and conclusions that are evident when taken as a whole. Thus the GDI researcher is informed regarding the degree to which engine volumetric efficiency and compression ratio can be increased under optimized conditions, and as to the extent to which unburned hydrocarbon (UBHC), NOx and particulate emissions can be minimized for specific combustion strategies. The critical area of GDI fuel injector deposits and the associated effect on spray geometry and engine performance degradation are reviewed, and important system guidelines for minimizing deposition rates and deposit effects are presented. The capabilities and limitations of emission control techniques and aftertreatment hardware are reviewed in depth, and areas of consensus on attaining European, Japanese and North American emission standards are compiled and discussed.

All known research, prototype and production GDI engines worldwide are reviewed as to performance, emissions and fuel economy advantages, and for areas requiring further development. The engine schematics, control diagrams and specifications are compiled, and the emission control strategies are illustrated and discussed. The influence of lean-NOx catalysts on the development of late-injection, stratified-charge GDI engines is reviewed, and the relative merits of lean-burn, homogeneous, direct-injection engines as an option requiring less control complexity are analyzed. All current information in the literature is used as the basis for discussing the future development of automotive GDI engines.

Automotive Spark-Ignited Direct-Injection Gasoline Engines

Under the 1997 Kyoto Protocol, no control of black carbon (BC) was considered. Here, it is found, through simulations in which 12 identifiable effects of aerosol particles on climate are treated, that any emission reduction of fossil-fuel (f.f.) particulate BC plus associated organic matter (OM) may slow global warming more than may any emission reduction of CO 2 or CH 4 for a specific period. When all f.f. BC + OM and anthropogenic CO 2 and CH 4 emissions are eliminated together, the period is 25-100 years. It is also estimated that historical net global warming can be attributed roughly to greenhouse gas plus f.f. BC + OM warming minus substantial cooling by other particles. Eliminating all f.f. BC + OM could eliminate 20-45% of net warming (8-18% of total warming before cooling is subtracted out) within 3-5 years if no other change occurred. Reducing CO 2 emissions by a third would have the same effect, but after 50-200 years. Finally, diesel cars emitting continuously under the most recent U.S. and E.U. particulate standards (0.08 g/mi; 0.05 g/km) may warm climate per distance driven over the next 100+ years more than equivalent gasoline cars. Thus, fuel and carbon tax laws that favor diesel appear to promote global warming. Toughening vehicle particulate emission standards by a factor of 8 (0.01 g/ mi; 0.006 g/km) does not change this conclusion, although it shortens the period over which diesel cars warm to 13-54 years. Although control of BC + OM can slow warming, control of greenhouse gases is necessary to stop warming. Reducing BC + OM will not only slow global warming but also improve human health.

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Control of fossil‐fuel particulate black carbon and organic matter, possibly the most effective method of slowing global warming

Particle size measurements using the electrical low pressure impactor (ELPI) and scanning mobility particle sizer (SMPS) are compared from the perspective of characterizing the particulate matter in motor vehicle exhaust. Both steady state vehicle operation and transient drive cycles are considered, and both gasoline and diesel fueled vehicle emissions are compared. Although the ELPI and SMPS measure different physical properties, respectively, the aerodynamic diameter and mobility diameter, the steady state particle size distributions are in close agreement, except for the 37 nm impactor stage of the ELPI which may overestimate particle number by up to a factor of two relative to the SMPS. This has little effect on the volume, or mass, weighted distribution. These, too, are generally in good agreement, though discrepancies appear at large particle size due to multiple charging effects in the SMPS and to electrometer offsets and the small particle loss correction in the ELPI. Selecting particles based on ...

Size Distributions of Motor Vehicle Exhaust PM: A Comparison Between ELPI and SMPS Measurements

This paper explores the extent to which standard dilution tunnel measurements of motor vehicle exhaust particulate matter modify particle number and size. Steady state size distributions made directly at the tailpipe, using an ejector pump, are compared to dilution tunnel measurements for three configurations of transfer hose used to transport exhaust from the vehicle tailpipe to the dilution tunnel. For gasoline vehicles run at a steady 50 70 mph, ejector pump and dilution tunnel measurements give consistent results of particle size and number when using an uninsulated stainless steel transfer hose. Both methods show particles in the 10 100 nm range at tailpipe concentrations of the order of 104 particles/cm3. When an insulated hose, or one containing a silicone rubber coupler, is used to test small 4 cylinder gasoline vehicles, a very intense nanoparticle / ultrafine mode at < ~30 nm develops in the dilution tunnel particle size distribution as the vehicle speed is increased to 60 and 70 mph. This nanoparticle mode coincides with a rise of the transfer line temperature to about 180 250 °C. It is much less evident for the full size gasoline sedan, which has cooler exhaust. Both tailpipe and dilution tunnel measurements of diesel vehicle exhaust reveal an accumulation mode peak of ~108 particles/cm3, centered at 80 -100 nm. In this case, even with the uninsulated transfer hose an intense ultrafine peak appears in the dilution tunnel size distributions. This mode is attributed to desorption and/or pyrolysis of organic material, either hydrocarbon deposits on the walls of the steel transfer hose or the silicone rubber, by hot exhaust gases, and their subsequent nucleation in the dilution tunnel. This substantially limits the ability to make accurate particle number and size measurements using dilution tunnel systems. INTRODUCTION Prompted by potential health concerns, the past few years have witnessed a growing interest in particulate matter (PM) measurements, both ambient and from a wide variety of emissions sources. These measurements are conventionally performed by recording PM mass. The ambient standards are written in terms of mass concentrations, and emission regulations are based on mass rates. However, in order to understand better the nature of the mobile source contribution to ambient PM, many research groups are currently extending their investigations to include measurements of the numbers and sizes of particles in motor vehicle exhaust. Because the standard procedure for tailpipe PM measurements utilizes a dilution tunnel to cool the exhaust and to prevent water condensation, concerns have emerged that the test cell measurements of motor vehicle PM do not reflect the “real world” emissions. The root of the concern is that vehicle exhaust, a hot, complex, mixture of gaseous emissions and particles, is transformed differently when diluted in a tunnel as compared to the “real world”. Particles are not immutable; they readily undergo transformations, such as coagulation, condensation, and adsorption, and new particles can be created by nucleation of gaseous particle precursors in the diluted and cooled exhaust. Under “real world” conditions, motor vehicle exhaust is diluted rapidly, in less than one second, and by a large amount, a dilution ratio of greater than 100, into air of variable temperature and humidity. In the test cell, the exhaust is conducted to the dilution tunnel, typically by a 10 cm diameter by 5 m long tube, where it is then diluted by a factor of between 5 and 50, depending on test conditions, using dry air at room temperature. This discrepancy between dilution times, extents, temperature, and humidity can potentially lead to significant differences in the nature of the particulate emissions.

Vehicle Exhaust Particle Size Distributions: A Comparison of Tailpipe and Dilution Tunnel Measurements

This paper reports mass measurements, size distributions, and the transient response of tailpipe particulate emissions from 21 recent model gasoline vehicles Transient measurement are made for the FTP drive cycle (and limited ECE test) using a scanning mobility particle sizer and an electrical low-pressure impactor The particles emitted in vehicle exhaust have diameters in the 10-300 nm diameter range, with a mean diameter of about 60 nm Particle emissions during the drive cycles occur as narrow peaks that correlate with vehicle acceleration Cold start emissions generally outweight those from a hot start by more than a factor of 3 Particulate mass deduced from the transient distributions agrees semiquantitatively with gravimetric measurements Tailpipe particulate emissions from the recent model gasoline vehicles tested are very low, with mass emission rated ranging downward from 7 mg/mi for a light-duty truck druing the cold start phase of the FTP drive cycle to less than or equal to 01 mg/mi during phase 2 for nearly half of the test vehicles Three high-mileage (greater than 100 K mi) test vehicles exhibited similarly low particulate emission rates The FTP-weighted 3-bag average is under 2 mg/mi for all the conventional gasoline vehicles tested (A)

Examination of the Size-Resolved and Transient Nature of Motor Vehicle Particle Emissions

Particulate Emissions from a Direct-Injection Spark-Ignition (DISI) Engine

Factors influencing the number and size of tailpipe particles from port injection, spark ignition vehicles are examined by comparing emissions recorded during steady-state operation and those obtained from FTP and US06 drive cycles. Size distributions are measured using the scanning mobility particle sizer (SMPS) and the electrical low-pressure impactor (ELPI). Steady-state particulate emissions are examined as a function of vehicle speed and air to fuel ratio. The emission rates increase moderately with increasing speed but climb steeply with decreasing A/F. This is consistent with the observations from transient drive cycle measurements where particulate emissions occur predominantly during periods of heavy acceleration. As expected from the more aggressive speed and acceleration of the US06 cycle, the per mile particulate emission rates are higher than for phases 2 and 3 of the FTP. For the eight vehicles tested, the US06 mass emissions range from 1.2 to 9.6 mg/mi. Use of a US06-compliant calibration l...

Diane H. Podsiadlik

Papers

Size Distributions of Motor Vehicle Exhaust PM: A Comparison Between ELPI and SMPS Measurements

Vehicle Exhaust Particle Size Distributions: A Comparison of Tailpipe and Dilution Tunnel Measurements

Examination of the Size-Resolved and Transient Nature of Motor Vehicle Particle Emissions

Particulate Emissions from a Direct-Injection Spark-Ignition (DISI) Engine

Gasoline vehicle particle size distributions: comparison of steady state, ftp, and us06 measurements