Centrifugal Particle Mass Analyzer Research Articles

Effect of fuel composition on properties of particles emitted from a diesel–natural gas dual fuel engine

The effective density and mixing state of particles emitted from a natural gas–diesel dual fuel engine are investigated. Measurements were conducted at three different fuel compositions including 100% diesel fuel (0% NG), 75% diesel–25% natural gas (25% NG) and 50% diesel–50% NG (50% NG). The particle effective density was measured using a differential mobility analyzer in series with a centrifugal particle mass analyzer. A catalytic stripper at 350 °C was employed upstream of the centrifugal particle mass analyzer in order to remove the semi-volatile material from the solid particles to measure the effective density of non-volatile particles as well as the particle mixing state. A scanning mobility particle sizer was used to measure the particle size distribution. The particle mass concentration was also measured using several techniques including cavity-attenuated phase-shift particulate matter single-scattering albedo, laser-induced incandescence, thermal-optical analysis, photoacoustic spectroscopy, and integrated particle size distribution. The semi-volatile number and mass fractions are found to be lower than 15%. The effective density functions of particles at 0% and 25% NG are within 6% of each other; however, the effective density values of particles at 50% NG are lower than those of the 0% NG by up to 35%. The mass-mobility exponent varies in the range of 2.42–2.51 and 2.38–2.54 for undenuded and denuded particles, respectively. For the mass concentration measurements, photoacoustic spectroscopy agrees with thermal-optical analysis within 5%, while all the other techniques measure up to 50% deviations relative to thermal-optical analysis.

Repeatability and intermediate precision of a mass concentration calibration system

Many aerosol instruments require calibration to make accurate measurements. A centrifugal particle mass analyzer (CPMA) and aerosol electrometer can be used to calibrate aerosol instruments that me...

Size, effective density, morphology, and nano-structure of soot particles generated from buoyant turbulent diffusion flames

With a global gas flaring volume of ∼140 billion cubic meters, flares are an important source of particulate emissions; however, very little is known about the physical and morphological properties of these particle emissions. To study these properties, a laboratory pipe flare producing a buoyant turbulent diffusion flame was used which allowed controlled experiments on flames up to ∼3 m tall. Three flare diameters (38.1, 50.8, and 76.2 mm) were used in this study with fuel exit velocities of 0.5, 0.9, and 1.5 m/s. ‘Light’, ‘medium’, and ‘heavy’ fuel compositions (consisting of C1 to C4 alkanes, carbon dioxide, and nitrogen in concentration representative of flares in the Alberta, Canada upstream oil and gas sector) were used, where heavier compositions refer to a greater concentration of higher order alkanes. Size distributions of soot particles were measured using a scanning mobility particle sizer. Mass-mobility relationship and effective density of particles were determined using a tandem arrangement of a differential mobility analyzer, a centrifugal particle mass analyzer and a condensation particle counter. Morphology and nano-structure of the particles were studied using transmission electron microscopy and Raman spectroscopy, respectively. Results showed that the particle median diameter and concentration increased as the fuel composition was changed from light to medium to heavy. On the other hand, particle morphology, measured by the relationships between particle mass vs. mobility (or effective density) and primary particle size vs. particle aggregate size, was independent of fuel composition, flow rate, or flare size and was in good agreement with previously reported values for that of soot particles from different internal combustion engines. Previously developed relations between effective density and primary particle size work well for the soot particles of this study. Raman spectroscopy indicated slightly lower D1/G ratios (more graphitic content) for the heavier fuels.

Properties of carbon black produced by the thermal decomposition of methane in the products of premixed flames

The thermal decomposition of methane is a technique used to manufacture hydrogen gas and carbon black. The physical properties of carbon black produced by the thermal decomposition of methane (TDM) in the O2-deficient gas products of two premixed flames (propane- or methane-air) were investigated under different flow rates of decomposing methane injection (0.5–5 SLPM). An inverted burner was designed to provide a fuel-rich, laminar premixed flame, to produce hot gas into which methane was injected to thermally decompose inside a reactor. Particles from TDM were extracted by a nitrogen dilution system at the immediate exit of the reaction chamber, where another branch of the exhaust was dried and directed to a gas chromatograph. The carbon black particles were characterized by size resolved number concentration, mass concentration, effective density, volatility, and internal mixing state using different arrangements of a differential mobility analyzer, catalytic denuder, centrifugal particle mass analyzer, and condensation particle counter, as well as by morphology and primary particle size using transmission electron microscopy. A bimodal number-size distribution was observed at all conditions with count median diameters (CMDs) less than 58 nm and 21 nm when using propane- or methane-air premixed flames as the heat source, respectively. Higher number concentrations and mass concentrations with larger CMDs were achieved under lower flow rates of decomposing methane injection. For a given flow rate of decomposition methane, mass concentration and CMD increased significantly when using propane as the fuel, compared to the methane fuel. The size segregated mass fraction of internally mixed volatile content in particles was similar for both heat sources, showing a roughly constant fraction of volatile material in particles produced by the decomposition of 0.5 and 5 SLPM of methane (10%–30%) but a measurably larger fraction (55%–30%) with a decreasing trend as a function of particle size from the decomposition of 1 SLPM of methane. The effective density of denuded particles was similar, but slightly higher, than the effective density of soot from a wide range of internal combustion engines. A higher denuded effective density was observed in the particles with higher volatile contents (particles from decomposition of 1 SLPM of methane), suggesting the restructuring of carbon black into more compact clusters due to excessive volatile condensation. TEM analysis revealed some similarity between the produced carbon black and engine soot in terms of morphology and primary particle diameter (both below 40 nm). Beside the carbon black properties, the efficiency of TDM in this configuration was also investigated by evaluation of methane destruction efficiency, as well as carbon black and hydrogen production efficiencies, based on the product gas composition and the particle mass concentration. It was found that longer residence times corresponding to lower flow rates resulted in higher conversion efficiencies in terms of methane destruction efficiency (maximum of ∼95%), hydrogen production efficiency (maximum of ∼80%), and carbon black production efficiency (maximum of ∼1%). It was concluded that the significantly low efficiency of carbon black production is due to the high amount of CO formation, likely through the gasification process.

Effects of fuel structure on structural characteristics of soot aggregates

Two critical structural characteristics of soot aggregates, i.e., the primary particle size and the spatial arrangement of primary particles in aggregates, were investigated for laminar premixed burner-stabilized stagnation propane flames with and without toluene addition under similar temperature profiles. To link the structural characteristics of soot aggregates with the dynamic processes of soot formation, the particle mass and mobility size were measured by using a centrifugal particle mass analyzer and a scanning mobility particle sizer respectively, which enabled us to obtain the particle size distributions and the spatially fractal feature or mass-mobility exponents. The results show that for pure propane flames, the size growth is relatively rapid as indicated from the particle size distributions, and soot aggregates are highly branched with bigger primary particles. By contrast, for toluene-added propane flames, soot nucleation is faster, while the size growth of primary particles is suppressed, resulting in more compact arrangement of smaller primary particles in the soot aggregates. For both types of flames, with the increase of flame temperature, the process of soot inception is accelerated, but the production of soot is suppressed due to the thermodynamic reversibility of soot precursors at higher temperatures.

On the Effective Density of Soot Particles in Premixed Ethylene Flames

In this work, the effective density of soot particles was studied in burner-stabilized-stagnation premixed ethylene flames, at an equivalent ratio of 2.0 and over the maximum flame temperature of 1747 K < Tmax < 1837 K, using micro-orifice probe sampling in tandem with a centrifugal particle mass analyzer, a differential mobility analyzer (DMA) and a condensation particle counter. For a better understanding of the variation of effective density with mobility diameter, monodisperse soot particles between 10 and 50 nm were classified via the DMA and imaged by transmission electron microscopy (TEM). The particle size distribution functions and the C/H ratio of the particles were measured by a scanning mobility particle sizer and an elemental analyzer, separately. The results show that for all these flames, effective density first increases and then decreases with increasing mobility diameter, and the maximum occurs at the mobility diameter of ∼20 nm, which is consistent with the size for soot morphology changing from spherical-like to non-spherical shapes according to the TEM images. With the increase of flame temperature, the effective density decreases, which is caused by the slower particle growth rate at higher temperatures as shown by a series of evidences.

A novel inversion method to determine the mass distribution of non-refractory coatings on refractory black carbon using a centrifugal particle mass analyzer and single particle soot photometer

A novel inversion method is presented, which derives the two-variable number distribution for black carbon aerosol, using a coupled centrifugal particle mass analyzer (CPMA) and single particle soo...

Determination of the effective density and fractal dimension of PM emissions from an aircraft auxiliary power unit

Gas turbine particulate matter (PM) emissions contribute to air quality degradation and are dangerous to both human health and the environment. Currently, PM mass concentrations determined from gravimetric measurements are the default parameter for gas turbine emissions compliance with PM regulations. The measurement of particle size however, is of significant interest due to its specific effects on health and climate science. The mass concentration can be determined from the number-size distribution measurement but requires the experimental evaluation of effective density of a number of particles to establish the power-law relationship. In this study, the effective density of PM emissions from an aircraft Auxiliary Power Unit (APU) with petroleum diesel, conventional aviation fuel (Jet A-1) and a multicomponent surrogate fuel (Banner NP 1014) as combusting fuels have been compared. An experimental configuration consisting of a Differential Mobility Analyzer, a Centrifugal Particle Mass Analyzer and a Condensation Particle Counter (DMA-CPMA-CPC) was deployed for this purpose. Overall, a decrease in the effective density (220–1900km−3) with an increase in the particle size was observed and found to depend on the engine operating condition and the type of fuel undergoing combustion. There was a change in the trend of the effective densities between the PM emissions generated from the fuels burnt and the engine operating conditions with increasing particle size.

Size-resolved effective density of submicron particles during summertime in the rural atmosphere of Beijing, China

Particle density is an important physical property of atmospheric particles. The information on high time-resolution size-resolved particle density is essential for understanding the atmospheric physical and chemical aging processes of aerosols particles. In the present study, a centrifugal particle mass analyzer (CPMA) combined with a differential mobility analyzer (DMA) was deployed to determine the size-resolved effective density of 50 to 350nm particles at a rural site of Beijing during summer 2016. The measured particle effective densities decreased with increasing particle sizes and ranged from 1.43 to 1.55g/cm3, on average. The effective particle density distributions were dominated by a mode peaked at around 1.5g/cm3 for 50 to 350nm particles. Extra modes with peaks at 1.0, 0.8, and 0.6g/cm3 for 150, 240, and 350nm particles, which might be freshly emitted soot particles, were observed during intensive primary emissions episodes. The particle effective densities showed a diurnal variation pattern, with higher values during daytime. A case study showed that the effective density of Aitken mode particles during the new particle formation (NPF) event decreased considerably, indicating the significant contribution of organics to new particle growth.

Experimental investigation of the effect of inlet particle properties on the capture efficiency in an exhaust particulate filter

The impact of inlet particle properties on the filtration performance of clean and particulate matter (PM) laden cordierite filter samples was evaluated using PM generated by a spark-ignition direct-injection (SIDI) engine fuelled with tier II EEE certification gasoline. Prior to the filtration experiments, an advanced aerosol characterization system that comprised of a scanning mobility particle spectrometer (SMPS), centrifugal particle mass analyzer (CPMA), a differential mobility analyzer (DMA), and a single particle mass spectrometer (SPLAT II) was used to obtain a wide range of information on the SIDI PM emissions including particle size distribution (PSD), composition, mass, and dynamic shape factors (DSFs) in the transition (χt) and free-molecular (χv) flow regimes. During the filtration experiments, real-time measurements of PSDs upstream and downstream of the filter sample were used to estimate the filtration performance and the total trapped mass within the filter using an integrated particle size distribution method. The filter loading process was paused multiple times to evaluate the filtration performance in the partially loaded state. The change in vacuum aerodynamic diameter (dva) distribution of mass-selected particles was examined for flow through the filter to identify whether preferential capture of particles of certain shapes occurred in the filter. The filter was also probed using different inlet PSDs. Pausing the filter loading process and subsequently performing the filter probing experiments did not impact the overall evolution of filtration performance. Within the present distribution of particle sizes, filter efficiency was independent of particle shape potentially due to the diffusion-dominant filtration process. Particle mobility diameter and trapped mass within the filter appeared to be the dominant parameters that impacted filter performance.

Tandem configuration of differential mobility and centrifugal particle mass analysers for investigating aerosol hygroscopic properties

Abstract. A tandem arrangement of Differential Mobility Analyser and Humidified Centrifugal Particle Mass Analyser (DMA-HCPMA) was developed to measure the deliquescence and efflorescence thresholds and the water uptake of submicron particles over the relative humidity (RH) range from 10 to 95 %. The hygroscopic growth curves obtained for ammonium sulfate and sodium chloride test aerosols are consistent with thermodynamic model predictions and literature data. The DMA-HCPMA system was applied to measure the hygroscopic properties of urban aerosol particles, and the kappa mass interaction model (KIM) was used to characterize and parameterize the concentration-dependent water uptake observed in the 50–95 % RH range. For DMA-selected 160 nm dry particles (modal mass of 3.5 fg), we obtained a volume-based hygroscopicity parameter, κv ≈ 0.2, which is consistent with literature data for freshly emitted urban aerosols.Overall, our results show that the DMA-HCPMA system can be used to measure size-resolved mass growth factors of atmospheric aerosol particles upon hydration and dehydration up to 95 % RH. Direct measurements of particle mass avoid the typical complications associated with the commonly used mobility-diameter-based HTDMA technique (mainly due to poorly defined or unknown morphology and density).

Effective density and volatility of particles sampled from a helicopter gas turbine engine

The effective density and size-resolved volatility of particles emitted from a Rolls-Royce Gnome helicopter turboshaft engine are measured at two engine speed settings (13,000 and 22,000 RPM). The effective density of denuded and undenuded particles was measured. The denuded effective densities are similar to the effective densities of particles from a gas turbine with a double annular combustor as well as a wide variety of internal combustion engines. The denuded effective density measurements were also used to estimate the size and number of primary particles in the soot aggregates. The primary particle size estimates show that the primary particle size was smaller at lower engine speed (in agreement with transmission electron microscopy analysis). As a demonstration, the size-resolved volatility of particles emitted from the engine is measured with a system consisting of a differential mobility analyzer, centrifugal particle mass analyzer, condensation particle counter, and catalytic stripper. This system determines the number distributions of particles that contain or do not contain non-volatile material, and the mass distributions of non-volatile material, volatile material condensed onto the surface of non-volatile particles, and volatile material forming independent particles (e.g., nucleated volatile material). It was found that the particulate at 13,000 RPM contained a measurable fraction of purely volatile material with diameters below ∼25 nm and had a higher mass fraction of volatile material condensed on the surface of the soot (6%–12%) compared to the 22,000 RPM condition (1%–5%). This study demonstrates the potential to quantify the distribution of volatile particulate matter and gives additional information to characterize sampling effects with regulatory measurement procedures.

Morphology and volatility of particulate matter emitted from a gasoline direct injection engine fuelled on gasoline and ethanol blends

The particulate matter emitted from a turbocharged, four cylinder, wall-guided, gasoline direct injection (GDI) engine fuelled with gasoline and ethanol blends was investigated, and characterized by size distribution, mass-mobility exponent, effective density, and volatility using tandem measurements from differential mobility analysers (DMA) and a centrifugal particle mass analyser (CPMA). Three engine loads were tested at 2250 RPM (4%, 13%, and 26% of maximum load) in addition to an idle condition while the engine was fuelled using gasoline mixed with ethanol fractions of 0% (E0), 10% (E10), and 50% (E50) by volume. An increase in engine load increased particle number concentration, although idle produced approximately as many particles as at 13% load. In the majority of cases, an increase in ethanol fraction decreased number concentration. The fraction of the number of particles comprised of only volatile material to total number of particles (number volatile fraction) both overall and as a function of particle mobility-equivalent diameter was under 10 percent at all engine conditions and fuels (measured after a three-way catalytic converter). The size-segregated ratio of the mass of internally mixed volatile material to total particle mass was similarly low. Volatility measurements were conducted using a thermodenuder set to 300°C. Mass-mobility exponent was seen to range between 2.28 and 2.60. Effective density increased with load, and in general mass-mobility exponent increased as well. Effective density decreased with an increase in ethanol fraction and a slight decrease in mass-mobility exponent was also observed for all conditions except idle. No significant changes in effective density, particle size, or number concentration were observed in GDI soot after denuding particle samples.

Methodology for quantifying the volatile mixing state of an aerosol

ABSTRACTMixing state refers to the relative proportions of chemical species in an aerosol, and the way these species are combined; either as a population where each particle consists of a single species (‘externally mixed’) or where all particles individually consist of two or more species (‘internally mixed’) or the case where some particles are pure and some particles consist of multiple species. The mixing state affects optical and hygroscopic properties, and quantifying it is therefore important for studying an aerosol's climate impact. In this article, we describe a method to quantify the volatile mixing state of an aerosol using a differential mobility analyzer, centrifugal particle mass analyzer, catalytic denuder, and condensation particle counter by measuring the mass distributions of the volatile and non-volatile components of an aerosol and determining how the material is mixed within and between particles as a function of mobility diameter. The method is demonstrated using two aerosol samples ...

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

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 4278dm−0.438 ± 76.3 kg/m3 (for mobility diameter, dm, in nm) for nascent particles and 3215dm−0.395 ± 37.9 kg/m3 for non-volatile particles. The effective density functions of the non-volatile particles were fairly similar for the conditions stu...

Effective density and mass–mobility exponents of particulate matter in aircraft turbine exhaust: Dependence on engine thrust and particle size

The mass and electrical mobility size of nascent soot generated by aircraft turbine engines were measured using a Differential Mobility Analyzer, a Centrifugal Particle Mass Analyzer and a Condensation Particle Counter in series. The measurements were conducted with a commonly used engine at a maintenance facility at airport Zurich, Switzerland. The aircraft engine under investigation was a CFM56-7B26/3. The used standardized sampling system conforms to the emission certification regulations captured by the “Society of Automotive Engineers, Aerospace Information Report 6241”. Effective densities of the aircraft soot were derived using measured power-law relationships between mass and electrical mobility size. The values ranged from 530kg/m3 to 1865kg/m3 depending on the particle mobility size and applied engine thrust. Trends in these effective densities suggest that the size of primary particles in the soot aggregates increase with increasing thrust. The mass-mobility exponents associated with these engine thrusts ranged from 2.54 to 2.79 and 1.86 to 2.32 for thrust levels above 30% and below 30%, respectively. Comparison with a second engine, a CFM56-5B4/2P, revealed higher effective densities for particles smaller than 40nm.

Transient measurement of the effective particle density of cigarette smoke

The real-time effective particle density of cigarette smoke was determined using a Centrifugal Particle Mass Analyzer (CPMA) and Differential Mobility Spectrometer (DMS). A Puff Inhale Exhale (PIE) simulator was used to produce the smoke from various research and commercial cigarettes following the International Standard Organization (ISO) puffing parameters (35ml puff of 2s duration, every 60s) or the Health Canada Intense (HCI) puffing parameters (55ml puff of 2s duration, every 30s). The impact of modifying parameters, such as smoke mass, cigarette format, filter type, inhalation volume and mouth hold period, on the effective particle density was also investigated. All of the effective density functions were found to be independent of particle size within the bias uncertainty of the measurement system, indicating that the cigarette smoke particles likely had a spherical morphology. Trends in the average effective particle densities were observed for the different cigarettes and puffing parameters. While all of these shifts were within the bias uncertainty of the CPMA–DMS system, two-sample t-tests and the Tukey method were used to identify where the shifts were statistically probable. However due to the complexity of cigarette smoke, the aerosol mechanisms behind most of these shifts were unknown and require further investigation. For all of the tested cases the average effective particle density, considering puffs 3–6, varied from 1090 to 1518kg/m3, with a majority (9 out of 16 cases) falling within 1300 to 1394kg/m3. The Tukey method identified no statistical change in the effective particle density over the duration of an ISO puff, but it did identify significant differences between effective densities produced by different cigarettes.

Characterization of Particulate Matter Morphology and Volatility from a Compression-Ignition Natural-Gas Direct-Injection Engine

The particulate matter (PM) emitted from a single-cylinder compression-ignition, natural-gas engine fitted with a High-Pressure Direct-Injection (HPDI) system distinctly different from a duel fuel engine was investigated, and characterized by size distribution, morphology, mass-mobility exponent, effective density, volatility, mixing state, and primary particle size using transmission electron microscopy (TEM), and tandem measurements from differential mobility analyzers (DMA) and a centrifugal particle mass analyzer (CPMA). Six engine conditions were selected with varying load, speed, exhaust gas recirculation (EGR) fraction, and fuel delivery strategy. An increase in engine load increased both the number concentration and the geometric mean diameter of the particulate. The fraction of the number of purely volatile particles to total number of particles (number volatile fraction, NVF) was found to decrease as load increased, although at the lower speed, partially premixed mode, the lowest NVF. All size d...

Particle Classification by the Tandem Differential Mobility Analyzer–Particle Mass Analyzer System

Particle mass analyzers, such as the aerosol particle mass analyzer (APM) and the Couette centrifugal particle mass analyzer (CPMA), are frequently combined with a differential mobility analyzer (DMA) to measure particle mass mp and effective density ρeff distributions of particles with a specific electrical mobility diameter dm. Combinations of these instruments, which are referred to as the DMA–APM or DMA–CPMA system, are also used to quantify the mass-mobility exponent Dm of non-spherical particles as well as to eliminate multiple charged particles. This study investigates the transfer functions of these setups, focusing especially on the DMA–APM system. The transfer function of the DMA–APM system was derived by multiplying the transfer functions of DMA and APM. The APM transfer function can be calculated using either the uniform or parabolic flow models. The uniform flow model provides an analytical function, while the parabolic flow model is more accurate. The resulting DMA–APM transfer functions wer...

Hygroscopic effects on the mobility and mass of cigarette smoke particles

The hygroscopic growth of particles, produced from a University of Kentucky 3R4F reference cigarette smoked following Health Canada Intense (HCI) puffing parameters (55mL puff of 2s duration, every 30s), was measured in terms of the electrical mobility diameter and particle mass, using a Hygroscopic Tandem Differential Mobility Analyzer (HTDMA) and Centrifugal Particle Mass Analyzer (CPMA) system. Both the particle mobility diameter and mass growth factors were found to agree with previously determined values and hygroscopicity models. The mobility diameter growth factor of the particles produced from either a University of Kentucky 3R4F or 1R5F reference cigarette, following HCI puffing parameters, were found to be very similar. As the relative humidity (RH) approached saturation, the effects of the initial particle size on the mobility growth factor became more dominant, with larger particles growing proportionally larger than smaller particles. From the measured mobility diameter and mass growth factors, the density growth factor was calculated. This parameter showed that the particle density increased as the sample relative humidity increased. This case is only possible, given that the dried smoke particle density (1109±118kg/m3) was determined to be greater than the density of water, if the water condensation on the smoke particle dissolves at least a portion of it, resulting in a significant increase in mass with only a small increase volume.