Engine Exhaust Particle Research Articles

Impact of fuel, injection type and after-treatment system on particulate emissions of light-duty vehicles using different fuels on FTP-75 and HWFET test cycles

The characteristics of particulate emission, in relation to factors such as fuel, injection type, after-treatment system and test cycle, were investigated. Five light-duty vehicles with different fuel, injection types and after-treatment systems - Compressed Natural Gas (CNG), Gasoline (Port Injection/Direct injection), and Diesel (with/without Diesel Particulate Filter (DPF)) - were tested on Federal Test Procedure (FTP) -75 and Highway Fuel Economy Test (HWFET) cycles. Particulate emissions were measured using a TSI 3090 Engine Exhaust Particle Sizer (EEPS) and Horiba Solid Particulate Counting system (SPCS). For the FTP-75 cycle, the DPF-equipped diesel vehicle showed the lowest particulate emission for the EEPS system, while CNG showed the lowest emission for the SPCS system due to the difference between the two measurement systems. However, the DPF-equipped diesel showed the least PN emission for both EEPS and SPCS method on the HWFET test cycle. Except for the DPF-equipped diesel, fuels with lighter molecular weight generated fewer particulates. Aside from fuel-type, the status of the engine was the most important factor determining particulate emission. When the engine was cold, a large number of particulates is formed regardless of engine-operating conditions. In contrast, warm engines form particulates only if the load on the engine is high enough, and the absolute magnitude is also lower than during the cold-start condition.

Effect of Ethanol–Diesel Fuel Blend on Diesel Engine Emissions Produced by Different Bus Fleets

AbstractThe major regulated pollutants emitted by a diesel urban bus are nitrogen oxides (NOx) and particulate matter (PM). These emissions depend on the engine and its strategies (injection, exhaust-gas recirculation, after-treatment devices, etc.), altitude, weather conditions, route, and driver. This work studies the effect of two fuels, one of them oxygenated, on both NOx emissions and particle-size distributions in comparison with a diesel fuel used as reference. The study was carried out with buses operating in two different cities, one of them located at around 650 m above sea level and the other near sea level. The test fuels were a binary blend of ethanol and diesel fuel (denoted as ED) and a diesel fuel without biodiesel (denoted as D). Emissions were measured using a Horiba OBS-1300 gas analyzer and a TSI engine exhaust particle sizer spectrometer. Results showed a reduction in both NOx emissions and total particle number concentrations with altitude, independently of fuel tested, and an increa...

The formation and physical properties of the particle emissions from a natural gas engine

Natural gas engine particle emissions were studied using an old gasoline engine modified to run with natural gas. The tests were steady-state tests performed on two different low loads in an engine dynamometer. Exhaust particle number concentration, size distribution, volatility and electric charge were measured. Exhaust particles were observed to have peak diameters below 10nm. To get the full picture of particle emissions from natural gas engines, size range 1–5nm is relevant and important to take into consideration. A particle size magnifier (PSM) was used in this engine application for measuring particles smaller than 3nm and it proved to be a useful instrument when measuring natural gas engine exhaust particles. It is concluded that the detected particles probably originated from the engine cylinders or their vicinity and grew to detectable sizes in the sampling process because a small fraction of the particles were observed to carry electric charge and the particles did not evaporate totally at 265°C.

Comparison of Vehicle Exhaust Particle Size Distributions Measured by SMPS and EEPS During Steady-State Conditions

Fast-sizing spectrometers, such as the TSI Engine Exhaust Particle Sizer (EEPS), have been widely used to measure transient particle size distributions of vehicle exhaust. Recently, size distributions measured during different test cycles have begun to be used for calculating suspended particulate mass; however, several recent evaluations have shown some deficiencies in this approach and discrepancies relative to the gravimetric reference method. The EEPS converts electrical charge carried by particles into size distributions based on mobility classification and a specific calibration, and TSI recently released a matrix optimized for vehicle emissions as described by Wang et al. (Submitteda). This study evaluates the performance of the new matrix (soot matrix) relative to the original matrix (default matrix) and reference size distributions measured by a scanning mobility particle sizer (SMPS). Steady-state particle size distributions were generated from the following five sources to evaluate exhaust part...

Effect of multiple-injection strategies on diesel engine exhaust particle size and nanostructure

Multiple-injection has been widely investigated to simultaneously reduce diesel NOx and soot emissions. While the comprehensive understanding of the effects of multiple injection on exhaust PM physical characteristics is still lacking. Three injection modes, single main, pilot-main and main-post injections, were compared in this work. The main objective is to better understand the influence of pilot and post injections on particle size and nanostructure characteristics in diesel exhaust. Experimental tests have shown that, for the pilot-main injection case, less premixed combustion and more diffusion combustion occur compared with the single main injection, which promotes formation of soot nuclei and results in a significant increase of number and mass of particles with the diameter above 100nm. On the contrary, soot oxidation later in the combustion is improved due to the enhancement of gas mean temperature (GMT) and air/fuel mixing for the main-post injection case, which favors soot oxidation and leads to the decrease of particle number and diameter. A comparison of particle nanostructures for the pilot-main injection case and main-post injection case has been conducted, which indicates that both low in-cylinder temperature and relative short carbonization time lead to the particles of less carbonization level (short fringe length and large fringe tortuosity) for the pilot-main injection case. Particles exhibit highly ordered graphitic structure for the main-post injection case due to the increase of combustion duration and the enhancement of in-cylinder temperature during the later stage of combustion derived by post combustion, which presents potential negative effect on diesel particle filters (DPF) regeneration efficiency.

A comprehensive analysis of the impact of biofuels on the performance and emissions from compression and spark-ignition engines

The compression ignition and small displacement spark-ignition engines play an important role in the urban air pollution. In particular, vehicles equipped with compression ignition engines are widely used because of their higher performance and fuel efficiency with respect to the spark-ignition ones. Nevertheless, spark-ignition engines with low displacements are even more wide-spreading because of the lower fuel consumption and emissions. They are also used for two-wheeled vehicles, whose easier navigation makes them widely used in heavily congested areas. Their contribution on urban pollution is worsened by the fact that these vehicles have to comply with the Euro 3 standard; light vehicles have, instead, to fulfill the more restrictive Euro 6, which for the compression ignition and gasoline direct injection engines indicates for particle emissions also a number-based regulation. This article aims to characterize the effects of biofuels on engine emissions and performance of compression ignition and spark-ignition engines. The investigation was carried out on different class of engines. Direct injection and a port fuel injection spark-ignition engines fueled with ethanol and its blends, 10 v/v%, 50 v/v% and 85 v/v% of ethanol in gasoline. The compression ignition engine was equipped with a common rail injection system and was fueled with pure rapeseed methyl ester, representative of fatty acid methyl ester, and its blends in diesel, 20 v/v% and 50 v/v%. The gaseous emissions and the particle concentration were measured at the exhaust by means of conventional instruments. Particle size distribution function was measured in the range from 5.6 to 560 nm by means of an engine exhaust particle sizer. A comprehensive characterization of the particulate carbon was performed by means of optical diagnostics in the combustion chamber. In particular, two-dimensional images of flame evolution were detected and processed by two-color pyrometry technique to assess the in-cylinder soot formation and oxidation processes. For both the investigated spark-ignition and compression ignition engines, the use of biofuels shows a partial increase in the specific fuel consumption and a reduction of the soot particles emission. Nevertheless, a further effort on engine technology should be paid to balance the mass with the size and number of the particles.

Measuring Particulate Emissions of Light Duty Passenger Vehicles Using Integrated Particle Size Distribution (IPSD).

The California Air Resources Board (ARB) adopted the low emission vehicle (LEV) III particulate matter (PM) standards in January 2012, which require, among other limits, vehicles to meet 1 mg/mi over the federal test procedure (FTP). One possible alternative measurement approach evaluated to support the implementation of the LEV III standards is integrated particle size distribution (IPSD), which reports real-time PM mass using size distribution and effective density. The IPSD method was evaluated using TSI's engine exhaust particle sizer (EEPS, 5.6-560 nm) and gravimetric filter data from more than 250 tests and 34 vehicles at ARB's Haagen-Smit Laboratory (HSL). IPSD mass was persistently lower than gravimetric mass by 56-75% over the FTP tests and by 81-84% over the supplemental FTP (US06) tests. Strong covariance between the methods suggests test-to-test variability originates from actual vehicle emission differences rather than measurement accuracy, where IPSD offered no statistical improvement over gravimetric measurement variability.

THE INFLUENCE OF LOAD VEHICLES IN ROAD TESTS ON THE PARTICLE MATTERS PARAMETERS

The emission of PM from combustion engines (given not only as mass but also number) has become the main determining factor influencing the design of drivetrains of modern vehicles. The PM measurement to date, based on the gravimetric method does not guarantee results on an expected accuracy and repeatability level. The introduction of emission standards, containing requirements related to the PM counting in the exhaust gases shows the need of identifying other PM parameters as well. The paper discusses the possibility of a synthetic approach to the parameters of PM generated by diesel engines. The authors felt compelled to realize the task following the obtainment of positive results of the PM parameters research under different operating conditions of diesel engines. The purpose of the tests described in the paper was to verify how the payload of vehicle effects on the PM emissions. It presents the results of road tests of commercial vehicles (LDV type) powered by diesel engines. The paper contains the results of measurements of concentration, mass and size distribution of PM emitted by the engines of these vehicles. The tests were conducted in actual traffic conditions. The AVL Micro Soot Sensor (measurement of the concentration and mass) and Engine Exhaust Particle Sizer 3090 by TSI Inc. (measurement of the size distribution) were used to measure the PM emissions.

Particulate Characterization and Size Distribution in the Exhaust of a Gasoline Homogeneous Charge Compression Ignition Engine

Agglomeration, coagulation, surface condensation, adsorption and oxidation processes are a part of particulate evolution process and lead to significant changes in characteristics of particulate matter (PM), when they enter the atmosphere. PM formation can be significantly reduced by advanced combustion concepts such as homogeneous charge compression ignition (HCCI). In the present study, experiments were performed in a modified gasoline fuelled HCCI engine at varying intake air temperatures (T_i), exhaust gas recirculation (EGR) rates and relative air-fuel ratios (λ). For particulate characterization, a partial flow dilution tunnel was used to collect particulate samples on a filter paper. These particulate samples were analysed for benzene soluble organic fraction (BSOF), trace metals, and particulate morphology using scanning electron microscopy (SEM). Physical characterisation of particulates was done using engine exhaust particle sizer (EEPS), which measured the particle size-number distribution. In the experiments, higher PM was found for richer fuel-air mixtures and it further increased with application of EGR. Trace metals were found to be significantly lower for HCCI generated PM, which increased with increasing EGR. BSOF was negligible as compared to total PM which showed relatively lower toxicity of gasoline HCCI particulates. Total number of particles reduced with increasing λ, however particulate size-number distribution curve shifted away from accumulation mode, indicating that the particulate size decreased with increasing λ. Higher particle size-number distribution and particle size-mass distribution were observed for increasing T_i. Particulate surface area and volume also increased with increasing T_i and mixture strength.

Particle effective density and mass during steady-state operation of GDI, PFI, and diesel passenger cars

Particle effective density is an important physical property of vehicle exhaust, and is required for estimating particulate matter (PM) mass emissions using the Integrated Particle Size Distribution (IPSD) method. In this study, we measure particle effective density of five light-duty vehicles with PM emissions below the Low Emission Vehicle (LEV) III PM standards of 1 or 3mg/mi (0.62 and 1.86mg/km) using the Differential Mobility Analyzer (DMA) – Centrifugal Particle Mass Analyzer (CPMA) approach. Test vehicles included two gasoline direct injection (GDI) vehicles without particulate filters, and for the first time reported in the literature, two port-fuel injected (PFI) vehicles and a turbocharged direct injection (TDI) light-duty diesel vehicle with a diesel particulate filter (DPF). The particle effective density functions generally resemble previous work on GDI and diesel engines without particulate filters but, for many size ranges, the PFI and TDI vehicles produced emissions with higher particle effective densities than GDI vehicles. Good linear correlation was found between the gravimetric and IPSD methods when applying the new particle effective density functions to size distribution measured by the TSI Engine Exhaust Particle Sizer (EEPS, 5.6–560nm, R2=0.84); however, the IPSD method underestimated gravimetric mass by 64%. When using a TSI Aerodynamic Particle Sizer (APS, 0.54–2.5µm) to measure the contribution of larger particles, underestimation bias was virtually eliminated and the correlation improved dramatically (R2=0.96). Even stronger correlation between IPSD and gravimetric methods was achieved when using a Scanning Mobility Particle Sizer (SMPS, 8.7–365nm) and the APS (R2=0.97). A procedure for correcting EEPS measurements using the SMPS is presented and evaluated.

THE INFLUENCE OF HYDROGEN GAS ON THE MEASURES OF EFFICIENCY OF DIESEL INTERNAL COMBUSTION ENGINE / VANDENILIO DUJŲ ĮTAKA DYZELINIO VIDAUS DEGIMO VARIKLIO EFEKTYVUMO RODIKLIAMS

In this research paper energy and ecological parameters of diesel engine which works under addition of hydrogen (10, 20, 30 l/ min) are presented. A survey of research literature has shown that addition of hydrogen gases improve diesel combustion; increase indicated pressure; decrease concentration of carbon dioxide (CO2), hydrocarbons (HC), particles; decrease fuel consumptions. Results of the experiment revealed that hydrogen gas additive decreased pressure in cylinder in kinetic combustion phase. Concentration of CO2 and nitrous oxides (NOx) decreased not significantly, HC – increased. Concentration of particles in engine exhaust gases significantly decreased. In case when hydrogen gas as additive was supplied, the fuel consumptions decreased a little. Using AVL BOOST software combustion process analysis was made. It was determined that in order to optimize engine work process under hydrogen additive usage, it is necessary to adjust diesel injection angle. Straipsnyje pateikiamas dyzelinio variklio, veikiančio su vandenilio priedu (10, 20, 30 l/min), energetinių ir ekologinių rodiklių tyrimas. Atlikus literatūros apžvalgą pastebėta, kad vandenilio dujų priedas pagerina dyzelino degimą, padidina indikatorinį slėgį, sumažina anglies dvideginio (CO2), angliavandenilių (HC), kietųjų dalelių koncentraciją, sumažina degalų sąnaudas. Bandymo rezultatai parodė, kad vandenilio dujų priedas sumažino variklio indikatorinį slėgį kinetinės degimo fazės metu. CO2 ir azoto oksidų (NOx) koncentracija nedaug sumažėjo, HC – padidėjo. Kietųjų dalelių koncentracija variklio išmetamosiose dujose itin sumažėjo. Tiekiant vandenilio dujas kaip priedą nedaug sumažėja dyzelino sąnaudos. AVL BOOST programa atlikta degimo proceso analizė. Nustatyta, kad siekiant optimizuoti variklio darbą, naudojant vandenilio priedą, būtina reguliuoti dyzelino įpurškimo paskubos kampą.

Effect of Particle Size Distribution on the Deep-Bed Capture Efficiency of an Exhaust Particulate Filter

The exhaust filtration analysis system (EFA) developed at the University of Wisconsin–Madison was used to perform microscale filtration experiments on cordierite filter samples using particulate matter (PM) generated by a spark ignition direct injection (SIDI) engine fueled with gasoline. A scanning mobility particle sizer (SMPS) was used to characterize running conditions with four distinct particle size distributions (PSDs). The distributions selected differed in the relative number of accumulation versus nucleation mode particles. The SMPS and an engine exhaust particle sizer (EEPS) were used to simultaneously measure the PSD downstream of the EFA and the real-time particulate emissions from the SIDI engine to determine the evolution of filtration efficiency (FE) during filter loading. Cordierite filter samples with properties representative of diesel particulate filters (DPFs) were loaded with PM from the different engine operating conditions. The results were compared to understand the impact of PSD on filtration performance as well as the role of accumulation mode particles on the diffusion capture of PM. The most penetrating particle size (MPPS) was observed to decrease as a result of particle deposition within the filter substrate. In the absence of a soot cake, the penetration of particles smaller than 70 nm was seen to gradually increase with time, potentially due to increased velocities in the filter as flow area reduces during filter loading, or due to decreasing wall area for capture of particles by diffusion. Particle re-entrainment was not observed for any of the operating conditions.

Temperature effects on particulate emissions from DPF-equipped diesel trucks operating on conventional and biodiesel fuels

Emissions tests were conducted on two medium heavy-duty diesel trucks equipped with a particulate filter (DPF), with one vehicle using a NOx absorber and the other a selective catalytic reduction (SCR) system for control of nitrogen oxides (NOx). Both vehicles were tested with two different fuels (ultra-low-sulfur diesel [ULSD] and biodiesel [B20]) and ambient temperatures (70ºF and 20ºF), while the truck with the NOx absorber was also operated at two loads (a heavy weight and a light weight). The test procedure included three driving cycles, a cold start with low transients (CSLT), the federal heavy-duty urban dynamometer driving schedule (UDDS), and a warm start with low transients (WSLT). Particulate matter (PM) emissions were measured second-by-second using an Aethalometer for black carbon (BC) concentrations and an engine exhaust particle sizer (EEPS) for particle count measurements between 5.6 and 560 nm. The DPF/NOx absorber vehicle experienced increased BC and particle number concentrations during cold starts under cold ambient conditions, with concentrations two to three times higher than under warm starts at higher ambient temperatures. The average particle count for the UDDS showed an opposite trend, with an approximately 27% decrease when ambient temperatures decreased from 70ºF to 20ºF. This vehicle experienced decreased emissions when going from ULSD to B20. The DPF/SCR vehicle tested had much lower emissions, with many of the BC and particle number measurements below detectable limits. However, both vehicles did experience elevated emissions caused by DPF regeneration. All regeneration events occurred during the UDDS cycle. Slight increases in emissions were measured during the WSLT cycles after the regeneration. However, the day after a regeneration occurred, both vehicles showed significant increases in particle number and BC for the CSLT drive cycle, with increases from 93 to 1380% for PM number emissions compared with tests following a day with no regeneration.Implications: The use of diesel particulate filters (DPFs) on trucks is becoming more common throughout the world. Understanding how DPFs affect air pollution emissions under varying operating conditions will be critical in implementing effective air quality standards. This study evaluated particulate matter (PM) and black carbon (BC) emissions with two DPF-equipped heavy-duty diesel trucks operating on conventional fuel and a biodiesel fuel blend at varying ambient temperatures, loads, and drive cycles.

Characterization of particles from a marine engine operating at low loads

Particle emissions from a marine diesel engine operating at low loads with four different fuels were characterized with respect to particle number (PN) and particle mass (PM), size distribution, volatility and chemical composition. The four different fuels used were Swedish Environmental class 1 (MK1) and class 3 diesel (MK3), heavy fuel oil (HFO, 0.12 wt% S) and marine diesel oil (MDO, 0.52 wt% S). The measurements were performed for a marine diesel engine in a test-bed engine lab and the particle emissions were measured with an Engine Exhaust Particle Sizer and a Dust Monitor, giving the number concentrations in the size range of 5.6–560 nm and 300 nm to 20 μm, respectively. To quantify the amount of solid particles a thermodenuder was used. Additionally, filter samples were taken for gravimetric, black carbon (BC) and elemental analysis. The particle emissions showed a bimodal size distribution by number and the number concentrations were dominated by nanoparticles (diameter (Dp) < 50 nm). The nanoparticles measured were both primary and secondary particles, depending on fuel and engine load, while the particles with Dp > 50 nm generally were solid primary particles. Combustion of HFO resulted in the highest PN and PM concentrations. Emission factors (EFs) for PM and PN for both the total particle emissions and the fraction of primary, solid particles are presented for different fuels and loads. EFs for nitrogen oxides (NOx), BC and some elements (Ca, Fe, V, Ni, Zn) are presented as well. This study contributes to understanding particle emissions from potential future fuels as well as emissions in ports and coastal areas where lower engine loads are common.

A source-independent empirical correction procedure for the fast mobility and engine exhaust particle sizers

The TSI Fast Mobility Particle Sizer (FMPS) and Engine Exhaust Particle Sizer (EEPS) provide size distributions for 6–560 nm particles with a time resolution suitable for characterizing transient particle sources; however, the accuracy of these instruments can be source dependent, due to influences of particle morphology. The aim of this study was to develop a source-independent correction protocol for the FMPS and EEPS. The correction protocol consists of: (1) broadening the >80 nm size range of the distribution to account for under-sizing by the FMPS and EEPS; (2) applying an existing correction protocol in the 8–93 nm size range; and (3) dividing each size bin by the ratio of total concentration measured by the FMPS or EEPS and a water-based Condensation Particle Counter (CPC) as a surrogate scaling factor to account for particle morphology. Efficacy of the correction protocol was assessed for three sources: urban ambient air, diluted gasoline direct injection engine exhaust, and diluted diesel engine exhaust. Linear regression against a reference instrument, the Scanning Mobility Particle Sizer (SMPS), before and after applying the correction protocol demonstrated that the correction ensured agreement within 20%.

Experimental Investigations of Particulate Size and Number Distribution in an Ethanol and Methanol Fueled HCCI Engine

Alcohols (ethanol and methanol) are being widely considered as alternative fuels for automotive applications. At the same time, homogeneous charge compression ignition (HCCI) engine has attracted global attention due to its potential of providing high engine efficiency and ultralow exhaust emissions. Environmental legislation is becoming increasingly stringent, sharply focusing on particulate matter (PM) emissions. Recent emission norms consider limiting PM number concentrations in addition to PM mass. Therefore, present study is conducted to experimentally investigate the effects of engine operating parameters on the PM size–number distribution in a HCCI engine fueled with gasoline, ethanol, and methanol. The experiments were conducted on a modified four-cylinder diesel engine, with one cylinder modified to operate in HCCI mode. Port fuel injection was used for preparing homogeneous charge in the HCCI cylinder. Intake air preheating was used to enable auto-ignition of fuel–air mixture. Engine exhaust particle sizer (EEPS) was used for measuring size–number distribution of soot particles emitted by the HCCI engine cylinder under varying engine operating conditions. Experiments were conducted at 1200 and 2400 rpm by varying intake air temperature and air–fuel ratio for gasoline, ethanol, and methanol. In this paper, the effect of engine operating parameters on PM size–number distribution, count mean diameter (CMD), and total PM numbers is investigated. The experimental data show that the PM number emissions from gasoline, ethanol, and methanol in HCCI cannot be neglected and particle numbers increase for relatively richer mixtures and higher intake air temperatures.

Particle emissions from biodiesels with different physical properties and chemical composition

Biodiesels produced from different feedstocks usually have wide variations in their fatty acid methyl ester (FAME) so that their physical properties and chemical composition are also different. The aim of this study is to investigate the effect of the physical properties and chemical composition of biodiesels on engine exhaust particle emissions. Alongside with neat diesel, four biodiesels with variations in carbon chain length and degree of unsaturation have been used at three blending ratios (B100, B50, B20) in a common rail engine. It is found that particle emission increased with the increase of carbon chain length. However, for similar carbon chain length, particle emissions from biodiesel having relatively high average unsaturation are found to be slightly less than that of low average unsaturation. Particle size is also found to be dependent on fuel type. The fuel or fuel mix responsible for higher particle mass (PM) and particle number (PN) emissions is also found responsible for larger particle median size. Particle emissions reduced consistently with fuel oxygen content regardless of the proportion of biodiesel in the blends, whereas it increased with fuel viscosity and surface tension only for higher diesel–biodiesel blend percentages (B100, B50). However, since fuel oxygen content increases with the decreasing carbon chain length, it is not clear which of these factors drives the lower particle emission. Overall, it is evident from the results presented here that chemical composition of biodiesel is more important than its physical properties in controlling exhaust particle emissions.

Measuring particulate matter emissions during parked active diesel particulate filter regeneration of heavy-duty diesel trucks

Heavy-duty diesel trucks (HDDTs, >33,000 pounds gross vehicle weight rating) are commonly equipped with diesel particulate filters (DPFs) to meet the California model year (MY) 2007 PM emissions standard. Particulate matter (PM) emissions were measured from nine parked active DPF regenerations of two HDDTs, a 2007 and 2010 MY, using a novel ambient-dilution wind tunnel. This work specifically evaluated PM mass emissions during regeneration by measurements from the following instruments: TSI DustTrak DRX 8533, TSI Engine Exhaust Particle Sizer 3090 (EEPS) and TSI Scanning Mobility Particle Sizer 3936L88 (SMPS), filters by gravimetric analysis, and for one test a Dekati Mass Monitor 230-A (DMM). Active regeneration by fuel injection upstream of the DPF began with the Soot Combustion Regime, where PM emissions had a count median diameter (CMD) of >30nm and some faint gray smoke was observed flowing from the tunnel. During brief moments of the Soot Combustion Regime, the DustTrak DRX reported more than half of the mass was >1µm. As active regeneration continued, aftertreatment inlet temperature increased to >500°C, beginning the Fuel Combustion Regime, defined conversely where the CMD of the emissions was <30nm. Under both regimes, discrepancies were observed between EEPS and SMPS size distributions and improved agreement was attained after performing a post-hoc EEPS correction procedure. The accuracy of the DMM was equivocal; the average DMM emissions rate was within five percent of the gravimetric filter, but the mass distribution was substantially shifted relative to SMPS and EEPS distributions. Uninterrupted parked active regeneration resulted in 13gPM emissions from the 2007 MY and 1.8gPM from the 2010 MY based on filter measurements. The PM mass emissions rates, based on measurements from real-time instruments, show that the contribution of Soot Combustion Regime to total regeneration emissions decreased from 75% to 5% between the 2007 and 2010 MY.

Effect of intake air temperature and air–fuel ratio on particulates in gasoline and n-butanolfueled homogeneous charge compression ignition engine

An experimental study was conducted to investigate the effect of engine operating parameters on exhaust particulate size–number distribution in a homogeneous charge compression ignition engine fueled with gasoline and n-butanol. In this investigation, portfuel injection was done for preparing homogeneous charge, and intake air preheating was used for auto-ignition of the charge. Engine exhaust particle sizer was used for measuring size–number distribution of particulate matter emitted from the homogeneous charge compression ignition engine. Experiments were conducted at different engine speeds by varying intake air temperature and air–fuel ratio of the charge. Effect of engine operating parameters on particulate size–number distribution, size–surface area distribution, and total particulate number concentration was investigated. Most significant particle numbers were in the range of 6–150 nm mobility diameter for all test conditions. n-Butanol showed relatively higher peak number concentration and lower mobility diameter corresponding to the peak concentrations as compared to baseline gasoline. On increasing intake air temperature, mobility diameters corresponding to peak number concentration of particles moved towards lower mobility diameters. Count mean diameter of particles was in the range of 35–80 nm and 20–65 nm for gasoline and n-butanol, respectively, for all test conditions in homogeneous charge compression ignition operating range.

Comparison of three nanoparticle sizing instruments: The influence of particle morphology

The TSI Fast Mobility Particle Sizer (FMPS), Engine Exhaust Particle Sizer (EEPS), and Scanning Mobility Particle Sizer (SMPS) provide size distributions for 6–560 nm particles. The aim of this study was to perform comprehensive equivalence testing of these three particle sizing instruments with particles of contrasting chemical and physical characteristics (urban ambient, diesel exhaust, and laboratory-generated particulate). It was observed that the EEPS and FMPS measurements agreed to within 15% thus concluding that data from these instruments may be considered equivalent. Parallel measurements with the SMPS showed that when measuring diesel exhaust particulate during ISO8178 Mode 9 operation there is significant overestimation of particle concentrations by both the EEPS and the FMPS in the 20–120 nm size range (25–38% overestimation). This overestimation also occurred for near-road measurement of heavy emitter vehicle plumes in ambient samples (up to 75% overestimation). Laboratory-generated soot agglomerate particles, whose shape was verified by transmission electron microscopy, were also tested. The agglomerate nature of diesel soot particulate was the dominant cause of the overestimation; parallel measurements with an FMPS and an Ultrafine Condensation Particle Counter of the laboratory-generated soot particulate showed overestimation by up to a factor of three.