The effective density and fractal dimension of soot particles from premixed flames and motor vehicle exhaust

Maricq, M. Matti; Xu, Nannan

doi:10.1016/j.jaerosci.2004.05.002

Cited by 320 publications

(276 citation statements)

References 45 publications

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“…The IPSD method was initially defined by Liu et al (2009), and more recently evaluated using emissions from LDVs by Li et al (2014) and Quiros et al (2015b), although the concept of using size distribution to estimate PM mass was discussed much earlier by Maricq and Xu (2004). Briefly, the IPSD method estimates total particle mass by integrating the fractional mass obtained by multiplying the particle effective density and volume concentration for each size bin from the measured PSD as follows:…”

Section: Discussionmentioning

confidence: 99%

“…For all particles larger than 55 nm, Equation (2) was used to calculate the particle effective density using data from Maricq and Xu (2004) (units g/cm 3 )). For particles with D p between 30 and 55 nm, the effective density calculated for particles with D p D 55 nm (1.031 g/cm 3 ) was applied, which fits with experimental data well shown in previous studies within this range (Maricq and Xu 2004;Quiros et al 2015b).…”

Section: Discussionmentioning

confidence: 99%

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

Xue

Wang

et al. 2015

Aerosol Science and Technology

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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 particulates with various morphologies estimated by mass-mobility scaling exponent: (1) A diesel generator operating on ultralow sulfur diesel, (2) a diesel generator operating on biodiesel, (3) a gasoline direct-injection vehicle operating at two speeds, (4) a conventional port-fuel injection gasoline vehicle, and (4) a light-duty diesel (LDD) vehicle equipped with a diesel particulate filter. Generally, the new soot matrix achieved much better agreement with the SMPS reference for particles smaller than 30 nm and larger than 100 nm, and also broadened the accumulation mode distribution that was previously too narrow using the default matrix. However, EEPS distributions still did not agree with SMPS reference measurements when challenged by a strong nucleation mode during high-load operation of the LDD vehicle. This work quantifies the range of accuracy that can be expected when measuring particle size distribution, number concentration, and integrated particle mass of vehicle emissions when using the new static calibration derived based on the properties of classical diesel soot.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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

Xue

Wang

et al. 2015

Aerosol Science and Technology

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“…The density values found in this and previous studies are high compared to the reported values for soot particle densities. According to the laboratory studies of Park et al (2003); Virtanen et al (2004b) and Maricq et al (2004) the density of the porous diesel soot agglomerates is close to 1 g/cm 3 at ∼60 nm and below ∼0.6 g/cm 3 at ∼100 nm. If the voids in the agglomerated particles get filled with condensable materials, particle density increases.…”

Section: Particle Densitymentioning

confidence: 98%

“…Diesel soot particles are agglomerates with a size dependent density which is below 1 g/cm 3 for particles larger than ∼60 nm (Park et al, 2003;Virtanen et al, 2004b;Maricq et al, 2004). According to authors' knowledge, there are no density values available from roadside measurements, and only very limited amount from urban measurement sites.…”

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confidence: 99%

Winter and summer time size distributions and densities of traffic-related aerosol particles at a busy highway in Helsinki

et al. 2006

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Abstract. Number concentrations and size distributions of traffic related aerosol particles were measured at a roadside in Helsinki during two winter campaigns (10-26 February 2003, 28 January-12 February 2004 and two summer campaigns (12-27 August 2003, 6-20 August 2004. The measurements were performed simultaneously at distances of 9 m and 65 m from the highway. Total number concentrations were measured by a condensation particle counter (CPC) and particle size distributions by a scanning mobility particle sizer (SMPS) and an electrical low pressure impactor (ELPI). This study concentrates on data that were measured when the wind direction was from the road to the measurement site. The total concentrations in the wintertime were 2-3 times higher than in the summertime and the concentrations were dominated by nucleation mode particles. The particles smaller than 63 nm (aerodynamic diameter) constituted ∼90% of all particles in the wintertime and ∼80% of particles in the summer time. The particle total concentration increased with increasing traffic rate. The effect of traffic rate on particles smaller than 63 nm was stronger than on the larger particles. The particle distributions at the roadside consisted of two distinguishable modes. The geometric mean diameter (GMD) of nucleation mode (Mode 1) was 20.3 nm in summer and 18.9 nm in winter. The GMD of the larger mode consisting mostly of traffic related soot particles (Mode 2) was 72.0 nm in summer and 75.1 nm in winter. The GMD values of the modes did not depend on the traffic rate. The average particle density for each mode was determined by a parallel density fitting method based on the size distribution measurement made by ELPI and SMPS. The average density value for Mode 1 particles Correspondence to: A. Virtanen (annele.virtanen@tut.fi) was 1.0±0.13 g/cm 3 and 1.0±0.07 g/cm 3 both in summer and winter respectively, while the average density value for Mode 2 was 1.5±0.1 g/cm 3 and 1.8±0.3 g/cm 3 for summer and winter, respectively.

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“…The integrated particle size distribution (IPSD) method is seen as an option for particle mass emission factor measurement for the modern vehicles (Liu et al 2009(Liu et al , 2012, which produce very few particles and where gravimetric measurement is difficult due to the low mass collected and the significance of errors due to sampling artifacts (Chase et al 2004). The effective density function for GDI particles has been measured by Maricq and Xu (2004), Symonds et al (2008), and Quiros et al (2015). However, the effect of volatility on particle effective density, and by extension the mass concentration measured by the IPSD method, has not been studied.…”

Section: Introductionmentioning

confidence: 99%

Effective Density and Volatility of Particles Emitted from Gasoline Direct Injection Vehicles and Implications for Particle Mass Measurement

Momenimovahed

Olfert

2015

Aerosol Science and Technology

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The effective density and volatility of particulate emissions from five gasoline direct injection (GDI) passenger vehicles were measured using a tandem differential mobility analyzer (DMA) and centrifugal particle mass analyzer (CPMA) system. The measurements were conducted on a chassis dynamometer at three steady-state operating conditions. A thermodenuder was employed to find the volatility and mixing state of the particles as well as the effective density of nascent and non-volatile particles (defined as particle phase remaining after denuding at 200 C). The mass-mobility exponent ranged between 2.4 and 2.7 for nascent (or undenuded) particles and between 2.5 and 2.7 for non-volatile particles; higher than typical diesel soot. The effective density function was 4278d m ¡0.438 § 76.3 kg/m 3 (for mobility diameter, d m , in nm) for nascent particles and 3215d m ¡0.395 § 37.9 kg/m 3 for non-volatile particles. The effective density functions of the non-volatile particles were fairly similar for the conditions studied. The uncertainty in using the effective density and mixing state data to determine the mass concentration of the aerosol by integrating mobility size distributions was examined. The uncertainty in mass concentration is minimized when only the non-volatile component is measured. However, the uncertainty in the mass concentration increases substantially if nascent particles are measured due to uncertainties in the particle mixing state and their associated effective densities. Furthermore, transient vehicle operation (cold-starts, accelerations, and decelerations) would likely change the mixing state of the exhaust particles suggesting it is difficult to accurately measure the mass concentration of undenuded GDI exhaust particulate using integrated size distribution methods.

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The effective density and fractal dimension of soot particles from premixed flames and motor vehicle exhaust

Cited by 320 publications

References 45 publications

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

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

Winter and summer time size distributions and densities of traffic-related aerosol particles at a busy highway in Helsinki

Effective Density and Volatility of Particles Emitted from Gasoline Direct Injection Vehicles and Implications for Particle Mass Measurement

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