Alternatives to the gravimetric method for quantification of diesel particulate matter near the lower level of detection

This paper is part of the Journal of the Air & Waste Management Association's 2010 special issue on combustion aerosol measurements. The issue is a combination of papers that synthesize and evaluate ideas and perspectives that were presented by experts at a series of workshops sponsored by the Coordinating Research Council that aimed to evaluate the current and future status of diesel particulate matter (DPM) measurement. Measurement of DPM is a complex issue with many stakeholders, including air quality management and enforcement agencies, engine manufacturers, health experts, and climatologists. Adoption of the U.S. Environmental Protection Agency 2007 heavy-duty engine DPM standards posed a unique challenge to engine manufacturers. The new standards reduced DPM emissions to the point that improvements to the gravimetric method were required to increase the accuracy and the sensitivity of the measurement. Despite these improvements, the method still has shortcomings. The objectives of this paper are to review the physical and chemical properties of DPM that make gravimetric measurement difficult at very low concentrations and to review alternative metrics and methods that are potentially more accurate, sensitive, and specific. Particle volatility, size, surface area, and number metrics are considered, as well as methods to quantify them. Although the authors believe that an alternative method is required to meet the needs of engine manufacturers, the methods reviewed in the paper are applicable to other areas where the gravimetric method detection limit is approached and greater accuracy and sensitivity are required. The paper concludes by suggesting a method to measure active surface area, combined with a method to separate semi-volatile and solid fractions to further increase the specificity of the measurement, has potential for reducing the lower detection limit of DPM and enabling engine manufacturers to reduce DPM emissions in the future.     

Evaluation of solid particle number and black carbon for very low particulate matter emissions standards in light-duty vehicles

To reliably measure at the low particulate matter (PM) levels needed to meet California’s Low Emission Vehicle (LEV III) 3- and 1-mg/mile particulate matter (PM) standards, various approaches other than gravimetric measurement have been suggested for testing purposes. In this work, a feasibility study of solid particle number (SPN, d50 = 23 nm) and black carbon (BC) as alternatives to gravimetric PM mass was conducted, based on the relationship of these two metrics to gravimetric PM mass, as well as the variability of each of these metrics. More than 150 Federal Test Procedure (FTP-75) or Supplemental Federal Test Procedure (US06) tests were conducted on 46 light-duty vehicles, including port-fuel-injected and direct-injected gasoline vehicles, as well as several light-duty diesel vehicles equipped with diesel particle filters (LDD/DPF). For FTP tests, emission variability of gravimetric PM mass was found to be slightly less than that of either SPN or BC, whereas the opposite was observed for US06 tests. Emission variability of PM mass for LDD/DPF was higher than that of both SPN and BC, primarily because of higher PM mass measurement uncertainties (background and precision) near or below 0.1 mg/mile. While strong correlations were observed from both SPN and BC to PM mass, the slopes are dependent on engine technologies and driving cycles, and the proportionality between the metrics can vary over the course of the test. Replacement of the LEV III PM mass emission standard with one other measurement metric may imperil the effectiveness of emission reduction, as a correlation-based relationship may evolve over future technologies for meeting stringent greenhouse standards.

Implications: Solid particle number and black carbon were suggested in place of PM mass for the California LEV III 1-mg/mile FTP standard. Their equivalence, proportionality, and emission variability in comparison to PM mass, based on a large light-duty vehicle fleet examined, are dependent on engine technologies and driving cycles. Such empirical derived correlations exhibit the limitation of using these metrics for enforcement and certification standards as vehicle combustion and after-treatment technologies advance.     

Directions for Combustion Engine Aerosol Measurement in the 21st Century

Abstract

The Coordinating Research Council convened two Real-Time PM Measurement Workshops in December 2008 and March 2009 to take an intensive look at the current status and future directions of combustion aerosol measurement. The purpose was to examine the implications of parallel rapid developments over the past decade in ambient aerosol science, engine aftertreatment technology, and aerosol measurement methodology, which provide bene?ts and challenges to the stakeholders in air quality management. The workshops were organized into sessions targeting key issues in ambient and source combustion particulate matter (PM). These include (1) metrics to characterize and quantify PM, (2) the need to reconcile ambient and source measurements, (3) the role of atmospheric transformations on modeling emissions and exposures, (4) the impact of sampling conditions on PM measurement, and (5) the potential bene?ts of novel PM instrumentation. This paper distills the material presented by subject experts and the insights derived from the in-depth discussions that formed the core of each session. The paper’s objectives are to identify areas of consensus that allow wider practical application of the past decade’s advances in combustion aerosol measurement to improve emissions and air quality modeling, develop emissions reduction strategies, and to recommend directions for progress on issues in which uncertainties remain.     

Directions for combustion engine aerosol measurement in the 21st century

The Coordinating Research Council convened two Real-Time PM Measurement Workshops in December 2008 and March 2009 to take an intensive look at the current status and future directions of combustion aerosol measurement. The purpose was to examine the implications of parallel rapid developments over the past decade in ambient aerosol science, engine aftertreatment technology, and aerosol measurement methodology, which provide benefits and challenges to the stakeholders in air quality management. The workshops were organized into sessions targeting key issues in ambient and source combustion particulate matter (PM). These include (1) metrics to characterize and quantify PM, (2) the need to reconcile ambient and source measurements, (3) the role of atmospheric transformations on modeling emissions and exposures, (4) the impact of sampling conditions on PM measurement, and (5) the potential benefits of novel PM instrumentation. This paper distills the material presented by subject experts and the insights derived from the in-depth discussions that formed the core of each session. The paper's objectives are to identify areas of consensus that allow wider practical application of the past decade's advances in combustion aerosol measurement to improve emissions and air quality modeling, develop emissions reduction strategies, and to recommend directions for progress on issues in which uncertainties remain.     

Exhaust Temperature Profiles for Application of Passive Diesel Particulate Filters to Solid Waste Collection Vehicles in California

Abstract

To reduce public exposure to diesel particulate matter (DPM), the California Air Resources Board has begun adoption of a series of rules to reduce these emissions from in-use heavy-duty vehicles. Passive diesel particulate filter (DPF) after-treatment technologies are a cost-effective method to reduce DPM emissions and have been used on a variety of vehicles worldwide. Two passive DPFs were interim-verified in California and approved federally for use in most 1994–2002 engine families for vehicles meeting min engine exhaust temperature requirements for successful filter regeneration. Some vehicles, however, may not be suited to passive DPFs because of lower engine exhaust temperatures. The purpose of this study was to determine the applicability of two types of passive DPFs to solid waste collection vehicles, the group of vehicles for which California recently mandated in-use DPM reductions. We selected 60 collection vehicles to represent the four main types of collection vehicle duty cycles—roll-offs, and front-end, rear, and side loaders—and collected second-by-second engine exhaust temperature readings for one week from each vehicle. As a group, the collection vehicles exhibited low engine exhaust temperatures, making the application of passive DPFs to these vehicles difficult. Only 35% of tested vehicles met the temperature requirements for one passive DPF, whereas 60% met the temperature requirements for the other. Engine exhaust temperatures varied by vehicle type. Side and front-end loaders met the engine exhaust temperature requirements in the greatest number of cases with ～50–90% achieving the required regeneration temperatures. Only 8–25% of the rear loader and roll-off collection vehicles met the engine exhaust temperature requirements. Solid waste collection vehicles represent a diverse fleet with a variety of duty cycles. Low engine exhaust temperatures will need to be addressed for successful use of passive DPFs in this application.     

Exhaust temperature profiles for application of passive diesel particulate filters to solid waste collection vehicles in California

To reduce public exposure to diesel particulate matter (DPM), the California Air Resources Board has begun adoption of a series of rules to reduce these emissions from in-use heavy-duty vehicles. Passive diesel particulate filter (DPF) after-treatment technologies are a cost-effective method to reduce DPM emissions and have been used on a variety of vehicles worldwide. Two passive DPFs were interim-verified in California and approved federally for use in most 1994--2002 engine families for vehicles meeting min engine exhaust temperature requirements for successful filter regeneration. Some vehicles, however, may not be suited to passive DPFs because of lower engine exhaust temperatures. The purpose of this study was to determine the applicability of two types of passive DPFs to solid waste collection vehicles, the group of vehicles for which California recently mandated in-use DPM reductions. We selected 60 collection vehicles to represent the four main types of collection vehicle duty cycles--rolloffs, and front-end, rear, and side loaders--and collected second-by-second engine exhaust temperature readings for one week from each vehicle. As a group, the collection vehicles exhibited low engine exhaust temperatures, making the application of passive DPFs to these vehicles difficult. Only 35% of tested vehicles met the temperature requirements for one passive DPF, whereas 60% met the temperature requirements for the other. Engine exhaust temperatures varied by vehicle type. Side and front-end loaders met the engine exhaust temperature requirements in the greatest number of cases with approximately 50-90% achieving the required regeneration temperatures. Only 8-25% of the rear loader and roll-off collection vehicles met the engine exhaust temperature requirements. Solid waste collection vehicles represent a diverse fleet with a variety of duty cycles. Low engine exhaust temperatures will need to be addressed for successful use of passive DPFs in this application.     

The effect of diesel fuel sulfur content on particulate matter emissions for a nonroad diesel generator

The effect of sulfur content on diesel particulate matter (DPM) emissions was studied using a diesel generator (Generac Model SD080, rated at 80 kW) as the emission source to simulate nonroad diesel emissions. A load simulator was used to apply loads to the generator at 0, 25, 50, and 75 kW, respectively. Three diesel fuels containing 500, 2100, and 3700 ppm sulfur by weight were selected as generator fuels. The U.S. Environmental Protection Agency sampling Method 5 "Determination of Particulate Matter Emissions from Stationary Sources" together with Method 1A "Sample and Velocity Traverses for Stationary Sources with Small Stacks or Ducts" was adopted as a reference method for measurement of the exhaust gas flow rate and DPM mass concentration. The effects of various parameters on DPM concentration have been studied, such as fuel sulfur contents, engine loads, and fuel usage rates. The increase of average DPM concentrations from 3.9 mg/Nm3 (n cubic meter) at 0 kW to 36.8 mg/Nm3 at 75 kW is strongly correlated with the increase of applied loads and sulfur content in the diesel fuel, whereas the fuel consumption rates are only a function of applied loads. An empirical correlation for estimating DPM concentration is obtained when fuel sulfur content and engine loads are known for these types of generators: Y = Zm(alphaX + beta), where Y is the DPM concentration, mg/m3, Z is the fuel sulfur content, ppm(w) (limited to 500-3700 ppm(w)), X is the applied load, kW, m is the constant, 0.407, alpha and beta are the numerical coefficients, 0.0118 +/- 0.0028 (95% confidence interval) and 0.4535 +/- 0.1288 (95% confidence interval), respectively.     

Determination of PAHs in diesel particulate matter using thermal extraction and solid phase micro-extraction

Determination of polycyclic aromatic hydrocarbons (PAHs) from chemical analysis of the diesel particulate matter (DPM) requires considerable sampling expertise and is often time-consuming because sample preparation demands strict extraction procedures due to the complex nature of the DPM matrix. In this study, a method to measure the emissions of the 16-U.S. Environmental Protection Agency (EPA) priority PAHs adsorbed in diesel particles has been developed. This method involves the capture of the DPM in glass microfibre filters, thermal extraction of the compounds from the particulate matrix in a thermogravimetric analyzer (TGA), determination of the concentration by means of a solid phase micro-extraction (SPME) fibre and subsequent analysis using a gas chromatograph coupled to a mass spectrometer (GC/MS). Analyses of a fully characterised DPM prepared by the National Institute of Standards and Technology, NIST (SRM 1650b), were performed and calculated errors showed that the method is capable of giving reliable quantitative data. Additionally, DPM collected from a diesel engine was analyzed and the results showed the high method sensitivity to the engine operating conditions.     

Control of Diesel Gaseous and Particulate Emissions with a Tube-Type Wet Electrostatic Precipitator

Abstract

In this study, experiments were performed with a bench-scale tube-type wet electrostatic precipitator (wESPs) to investigate its effectiveness for the removal of mass- and number-based diesel particulate matter (DPM), hydrocarbons (HCs), carbon monoxide (CO), and oxides of nitrogen (NO_x) from diesel exhaust emissions. The concentration of ozone (O₃) present in the exhaust that underwent a nonthermal plasma treatment process inside the wESP was also measured. A nonroad diesel generator operating at varying load conditions was used as a stationary diesel emission source. The DPM mass analysis was conducted by means of isokinetic sampling and the DPM mass concentration was determined by a gravimetric method. An electrical low-pressure impactor (ELPI) was used to quantify the DPM number concentration. The HC compounds, n-alkanes, and polycyclic aromatic hydrocarbons (PAHs) were collected on a moisture-free quartz filter together with a PUF/XAD/PUF cartridge and extracted in dichloromethane with sonication. Gas chromatography (GC)/mass spectroscopy (MS) was used to determine HC concentrations in the extracted solution. A calibrated gas combustion analyzer (Testo 350) and an O₃ analyzer were used for quantifying the inlet and outlet concentrations of CO and NO_x (nitric oxide [NO] + nitrogen dioxide [NO₂]), and O₃ in the diesel exhaust stream. The wESP was capable of removing approximately 67–86% of mass- and number-based DPM at a 100% exhaust volumetric flow rate generated from 0- to 75-kW engine loads. At 75-kW engine load, increasing gas residence time from approximately 0.1 to 0.4 sec led to a significant increase of DPM removal efficiency from approximately 67 to more than 90%. The removal of n-alkanes, 16 PAHs, and CO in the wESP ranged from 31 to 57% and 5 to 38%, respectively. The use of the wESP did not significantly affect NO_x concentration in diesel exhaust. The O₃ concentration in diesel exhaust was measured to be less than 1 ppm. The main mechanisms responsible for the removal of these pollutants from diesel exhaust are discussed.     

Factors affecting heavy-duty diesel vehicle emissions

Societal and governmental pressures to reduce diesel exhaust emissions are reflected in the existing and projected future heavy-duty certification standards of these emissions. Various factors affect the amount of emissions produced by a heterogeneous charge diesel engine in any given situation, but these are poorly quantified in the existing literature. The parameters that most heavily affect the emissions from compression ignition engine-powered vehicles include vehicle class and weight, driving cycle, vehicle vocation, fuel type, engine exhaust aftertreatment, vehicle age, and the terrain traveled. In addition, engine control effects (such as injection timing strategies) on measured emissions can be significant. Knowing the effect of each aspect of engine and vehicle operation on the emissions from diesel engines is useful in determining methods for reducing these emissions and in assessing the need for improvement in inventory models. The effects of each of these aspects have been quantified in this paper to provide an estimate of the impact each one has on the emissions of diesel engines.     

Control of diesel gaseous and particulate emissions with a tube-type wet electrostatic precipitator

In this study, experiments were performed with a bench-scale tube-type wet electrostatic precipitator (wESPs) to investigate its effectiveness for the removal of mass- and number-based diesel particulate matter (DPM), hydrocarbons (HCs), carbon monoxide (CO), and oxides of nitrogen (NOx) from diesel exhaust emissions. The concentration of ozone (O3) present in the exhaust that underwent a nonthermal plasma treatment process inside the wESP was also measured. A nonroad diesel generator operating at varying load conditions was used as a stationary diesel emission source. The DPM mass analysis was conducted by means of isokinetic sampling and the DPM mass concentration was determined by a gravimetric method. An electrical low-pressure impactor (ELPI) was used to quantify the DPM number concentration. The HC compounds, n-alkanes, and polycyclic aromatic hydrocarbons (PAHs) were collected on a moisture-free quartz filter together with a PUF/XAD/PUF cartridge and extracted in dichloromethane with sonication. Gas chromatography (GC)/mass spectroscopy (MS) was used to determine HC concentrations in the extracted solution. A calibrated gas combustion analyzer (Testo 350) and an O3 analyzer were used for quantifying the inlet and outlet concentrations of CO and NOx (nitric oxide [NO] + nitrogen dioxide [NO2]), and O3 in the diesel exhaust stream. The wESP was capable of removing approximately 67-86% of mass- and number-based DPM at a 100% exhaust volumetric flow rate generated from 0- to 75-kW engine loads. At 75-kW engine load, increasing gas residence time from approximately 0.1 to 0.4 sec led to a significant increase of DPM removal efficiency from approximately 67 to more than 90%. The removal of n-alkanes, 16 PAHs, and CO in the wESP ranged from 31 to 57% and 5 to 38%, respectively. The use of the wESP did not significantly affect NOx concentration in diesel exhaust. The O3 concentration in diesel exhaust was measured to be less than 1 ppm. The main mechanisms responsible for the removal of these pollutants from diesel exhaust are discussed.     

Tomato Root: Site of Initial Alteration in Minor Elements in Cadmium Treated Plants

Abstract

Societal and governmental pressures to reduce diesel exhaust emissions are reflected in the existing and projected future heavy-duty certification standards of these emissions. Various factors affect the amount of emissions produced by a heterogeneous charge diesel engine in any given situation, but these are poorly quantified in the existing literature. The parameters that most heavily affect the emissions from compression ignition engine-powered vehicles include vehicle class and weight, driving cycle, vehicle vocation, fuel type, engine exhaust aftertreatment, vehicle age, and the terrain traveled. In addition, engine control effects (such as injection timing strategies) on measured emissions can be significant. Knowing the effect of each aspect of engine and vehicle operation on the emissions from diesel engines is useful in determining methods for reducing these emissions and in assessing the need for improvement in inventory models. The effects of each of these aspects have been quantified in this paper to provide an estimate of the impact each one has on the emissions of diesel engines.     

Investigations on the effect of chlorine in lubricating oil and the presence of a diesel oxidation catalyst on PCDD/F releases from an internal combustion engine

This paper reports on an intensive study into releases of polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated furans (PCDF) and polychlorinated biphenyls (PCB) from a diesel engine and the analysis of PCDD/F and PCB in crankcase lubricating oil. Experimental conditions were set and carefully controlled in order to maximize the possible impact of, and our ability to measure the effect of, changes in the levels of chlorine in the lubricant. Emissions to air were measured using modified EPA methods following the principles of the European EN 1948 standards. A series of 40 experimental runs were completed using three reference lubricants formulated to have three levels of chlorine present as a residual component (at levels of 12, 131 and 259 mg kg(-1) or ppm). The engine was run with and without the diesel oxidation catalyst. All lubricants were realistic oils and the use of unrealistic additives or doping of components - particularly chlorine - in the fuel and lubricant was carefully avoided. Analysis of fuel and lubricant (before and after testing) samples required strenuous attention to achieve acceptable recoveries and showed non-detectable levels of PCB and PCDD/F at a detection limit of around 1.5 ng I-TEQ kg(-1) (ppt), indistinguishable from the laboratory blank. The testing demonstrated the need for extreme care to be taken in developing measurement methods that are sufficiently sensitive for measuring chlorine content of fluids and PCDD/F in oils, the latter being particularly challenging. Mean emissions of PCDD/F with the diesel oxidation catalyst in place were 23 pg I-TEQ l(-1) of fuel and with the diesel oxidation catalyst removed 97 pg I-TEQ l(-1) of fuel. The results of this testing showed that the emissions of PCDD/F were greatly reduced by the presence of a diesel oxidation catalyst in the exhaust, a finding that has not been explicitly tested in previous work. They also show that emissions from the engine were not controlled by the level of chlorine in the lubricant and that emissions did not change in response to a much greater step change in the total chlorine entering the combustion chamber due to a change in the level of chlorine in the fuel. Emissions when the engine was configured with a diesel oxidation catalyst showed a consistent pattern that appears to be unique in the experience of the authors.     

Competitive diesel engine emissions of sulphur and nitrogen species

NO_x, nitrate and sulphate emissions from a typical European passenger car diesel engine have been measured testing eight different fuels under five steady operating conditions (reproducing modes of the European transient urban/extraurban certification cycle). It is confirmed that nitrogen species compete with sulphur compounds to be adsorbed by diesel particulate matter (DPM) before being emitted into the atmosphere. This competition is found to increase with engine load, and is explained on the basis of the different specific surface and adsorption capacity of soot particles under different operating modes. When a high specific surface is available, as occurs in low load modes, both nitrates and sulphates are adsorbed by soot particles. On the contrary when a small surface is accessible, like in high load modes, sulphates are selectively adsorbed. This is specially important since sulphates are responsible for hydrocarbon retention in DPM due to the scrubbing effect.     

Study of Miller timing on exhaust emissions of a hydrotreated vegetable oil (HVO)-fueled diesel engine

The effect of intake valve closure (IVC) timing by utilizing Miller cycle and start of injection (SOI) on particulate matter (PM), particle number, and nitrogen oxide (NO_x) emissions was studied with a hydrotreated vegetable oil (HVO)-fueled nonroad diesel engine. HVO-fueled engine emissions, including aldehyde and polyaromatic hydrocarbon (PAH) emissions, were also compared with those emitted with fossil EN590 diesel fuel. At the engine standard settings, particle number and NO_x emissions decreased at all the studied load points (50%, 75%, and 100%) when the fuel was changed from EN590 to HVO. Adjusting IVC timing enabled a substantial decrease in NO_x emission and combined with SOI timing adjustment somewhat smaller decrease in both NO_x and particle emissions at IVC??50 and??70 °CA points. The HVO fuel decreased PAH emissions mainly due to the absence of aromatics. Aldehyde emissions were lower with the HVO fuel with medium (50%) load. At higher loads (75% and 100%), aldehyde emissions were slightly higher with the HVO fuel. However, the aldehyde emission levels were quite low, so no clear conclusions on the effect of fuel can be made. Overall, the study indicates that paraffinic HVO fuels are suitable for emission reduction with valve and injection timing adjustment and thus provide possibilities for engine manufacturers to meet the strictening emission limits.

Implications: NO_x and particle emissions are dominant emissions of diesel engines and vehicles. New, biobased paraffinic fuels and modern engine technologies have been reported to lower both of these emissions. In this study, even further reductions were achieved with engine valve adjustment combined with novel hydrotreated vegetable oil (HVO) diesel fuel. This study shows that new paraffinic fuels offer further possibilities to reduce engine exhaust emissions to meet the future emission limits.

Supplementary Materials: Supplementary materials are available for this paper. Go to the publisher's online edition of the Journal of the Air & Waste Management Association for a complete list of analysed PAH compounds.     

Emissions profile from new and in-use handheld, 2-stroke engines

The objective of this study was to characterize exhaust emissions from a series of handheld, 2-stroke small engines. A total of 23 new and used engines from model years 1981–2003 were studied; these engines spanned three phases of emission control (pre-control, phase-1, phase-2). Measured emissions included carbon monoxide (CO), carbon dioxide (CO₂), nitrogen oxides (NO_x), hydrocarbons (HC), fine particulate matter (PM_2.5), and sulfur dioxide (SO₂). Emissions reductions in CO (78%) and HC (52%) were significant between pre-control and phase-2 engines. These reductions can be attributed to improvements in engine design, reduced scavenging losses, and implementation of catalytic exhaust control. Total hydrocarbon emissions were strongly correlated with fuel consumption rates, indicating varying degrees of scavenging losses during the intake/exhaust stroke. The use of a reformulated gasoline containing 10% ethanol resulted in a 15% decrease in HC and a 29% decrease in CO emissions, on average. Increasing oil content of 2-stroke engine fuels results in a substantial increase of PM_2.5 emissions as well as smaller increases in HC and CO emissions. Results from this study enhance existing emission inventories and appear to validate predicted improvements to ambient air quality through implementation of new phase-2 handheld emission standards.     

Cold start extra emissions as a function of engine stop time: Evolution over the last 10 years

Cars with catalysts show a significant increase in exhaust emissions at engine start. These extra emissions are expressed as the difference, over a particular driving cycle, between emissions generated when the vehicle is started and when the engine or the catalyst are stably warm. Experimental data, suitable for the assessment of cold start emissions, are usually available for completely cooled engines. Most results originate from tests at ambient temperature of 20–30 °C and with an engine stop time of at least 12 h. On the other hand, data including shorter stop times are very rare.The present work investigates the influence of exhaust emissions with shorter stop times, i.e. 0.5, 1, 2 and 4 h. The main goal consists in the comparison of emissions exhausted by recent car models (Euro-4) against emissions assessed in the framework of a similar campaign 10 years ago (FAV1/Euro-1 vehicles).A short survey of the current extra emission estimation methods is presented in this paper. It is shown that some methods are not suited for providing correct estimations in all cases. We discuss the fact that different estimation methods can show either similar or completely different results depending on the evolution behaviour of the hot emissions.Due to new technologies, e.g. the catalyst and improved engine control algorithms, emissions have been considerably reduced over the last 10 years. In this study it is determined how the relative extra emissions, i.e. extra emissions relative to the extra emissions for the standard stop time of 12 h, expressed as a function of stop time have changed. We may claim with caution that for medium stop times of 0.5–4 h the average relative extra emissions of Euro-4 vehicles are well below the average of the relative extra emissions of Euro-1 vehicles.     

Techniques and Procedures for the Measurement of Aircraft Gas Turbine Engine Emissions

In 1968 the Society of Automotive Engineers formed the Committee on Aircraft Exhaust Emissions Measurement (E-31) whose charge was the development of acceptable standards of measurement for the characterization of aircraft engine exhaust. This committee’s efforts have resulted in the issuance of two Aerospace Recommended Practices, ARP 1179 “Aircraft Gas Turbine Exhaust Smoke Measurement” and ARP 1256 “Procedure for the Continuous Sampling and Measurement of Gaseous Emissions from Aircraft Turbine Engines.” These Recommended Practices have in large part been adopted by the Environmental Protection Agency and promulgated in Federal Register Volume 38, Number 136, Tuesday, July 17, 1973.

For the past three years Pratt & Whitney Aircraft has been measuring emissions from aircraft gas turbine engines using on-line instrumentation systems designed both in accordance with these Aerospace Recommended Practices and in response to the operational needs of a large experimental engineering test facility. In addition to a discussion of these systems this paper describes the experience derived from continuous testing programs in support of this test facility with consideration being given to the specific problems of sampling, sample handling, system accuracy, and data recording and reduction. Comment is made as to the practical limitations of the recommended methods and procedures as applied to emission control technology programs and suggestions are presented for improving the measurement technology.     

Analysis of Industrial Boiler Solid Waste Impacts

This paper presents an examination of industrial coal-fired boiler waste products. Presently the atmospheric emissions from all new boilers larger than 250 × 10⁶ Btu/hr are controlled by existing New Source Performance Standards, and boilers smaller than 250 × 10⁶ Btu/hr are controlled to levels required by the regulations of the particular state in which the facility is located. The 1977 Clean Air Act Amendments, however, specify categories of sources for which EPA must develop revised New Source Performance Standards. Industrial coal-fired boilers are included as one of these categories, and a relevant issue concerns the potential amount of solid waste generated as a result of tightened emission standards that require flue gas desulfurization. This paper examines the air quality and solid waste impacts of moderate and stringent emission controls for particulate and SO₂ emissions from industrial coal-fired boilers.

Comparisons are presented of physical and chemical characterizations of the emissions and solid wastes produced when boilers are equipped with particulate and SO₂ control equipment. The SO₂ systems examined are lime spray drying, lime/limestone, double alkali, sodium throwaway, physically cleaned coal, and fluidized-bed combustion. The solid waste disposal alternatives and the disposal costs are discussed. The most common disposal methods used are landfill for dry wastes and impoundment for sludges, with special wastewater treatment requirements for the sodium throwaway aqueous wastes.     

A study of extractive and remote-sensing sampling and measurement of emissions from military aircraft engines

Aircraft emissions contribute to the increased atmospheric burden of particulate matter (PM) that plays an important role in air quality, human health, visibility, contrail formation and climate change. Sampling and measurement of modern aircraft emissions at the engine exhaust plane (EEP) for engine and fuel certification remains challenging, as no agency-certified method is available. In this paper we summarize the results of three recent field studies devoted to investigate the consistency and applicability of “extractive” and “optical remote-sensing” (ORS) technologies in the sampling and measurement of gaseous and PM emitted by a number of military aircraft engines. Three classes of military engines were investigated; these include T56, TF33, and T700 & T701C types of engines, which consume 70–80% of the military aviation fuel each year. JP-8 and Fischer–Tropsch (FT)-derived paraffinic fuels were used to study the effect of fuels. It was found that non-volatile particles in the engine emissions were in the 20 nm range for the low power condition of new helicopter engines to 80 nm for the high power condition of legacy engines. Elemental analysis indicated little metals were present on particles, while most of the materials on the exhaust particles were carbon and sulfate based. Alkanes, carbon monoxide, carbon dioxide, nitrogen oxides, sulfur dioxide, formaldehyde, ethylene, acetylene and propylene were detected. The last five species were most noticeable only under low engine power. The emission indices calculated based on the ORS data deviate significantly from those based on the extractive data. Nevertheless, the ORS techniques were useful in the sense that it provided non-intrusive real-time detection of species in the exhaust plume, which warrants further development. The results obtained in this program help validate sampling methodology and measurement techniques used for non-volatile PM aircraft emissions as described in the SAE AIR6037 (2009).