Alternative metrics for spatially and temporally resolved ambient particle monitoring

Pham, Liem; Jung, Heejung

doi:10.1016/j.jaerosci.2016.09.004

Cited by 7 publications

(4 citation statements)

References 23 publications

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“…Previous work by Pham and Jung (2016) has shown that the ratio of particle surface area to particle number concentration is indicative of the average particle diameter (equation (1), methods). Over the course of Test 3, air recirculation reduced particulate concentrations in the cabin as expected.…”

Section: Discussionmentioning

confidence: 99%

“…This instrument measures the so-called active surface area of particles using diffusion charging. Evolution of the geometric mean diameter (GMD) of particles in the cabin could be determined using the ratio of particle surface area (PS) over particle number concentration (PN) measured by EAD and CPC using equation (1) (Pham and Jung, 2016):

italicGMD = \frac{{(\frac{1}{c})}^{1.13}}{exp true[\frac{1.13}{2} {ln}^{2} σ_{g} true]} \cdot {true(\frac{EAD response}{CPC response} true)}^{\frac{1}{1.13}}

Where c is 5.146·10 −4 for mm/cm 3 unit of EAD response and σ g is assumed as 1.7, mimicking geometric standard deviation of accumulation mode particles. This analysis, enabled by the simultaneous measurement of GMD and particle concentration, was meant to show the effectiveness of cabin air recirculation for reducing concentrations of small particles in particular, such as nanoparticles and ultrafine particles.…”

Section: Methodsmentioning

confidence: 99%

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Simultaneously reducing CO2 and particulate exposures via fractional recirculation of vehicle cabin air

Jung

Grady

Victoroff

et al. 2017

Atmospheric Environment

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Prior studies demonstrate that air recirculation can reduce exposure to nanoparticles in vehicle cabins. However when people occupy confined spaces, air recirculation can lead to carbon dioxide (CO2) accumulation which can potentially lead to deleterious effects on cognitive function. This study proposes a fractional air recirculation system for reducing nanoparticle concentration while simultaneously suppressing CO2 levels in the cabin. Several recirculation scenarios were tested using a custom-programmed HVAC (heat, ventilation, air conditioning) unit that varied the recirculation door angle in the test vehicle. Operating the recirculation system with a standard cabin filter reduced particle concentrations to 1000 particles/cm3, although CO2 levels rose to 3000 ppm. When as little as 25% fresh air was introduced (75% recirculation), CO2 levels dropped to 1000 ppm, while particle concentrations remained below 5000 particles/cm3. We found that nanoparticles were removed selectively during recirculation and demonstrated the trade-off between cabin CO2 concentration and cabin particle concentration using fractional air recirculation. Data showed significant increases in CO2 levels during 100% recirculation. For various fan speeds, recirculation fractions of 50–75% maintained lower CO2 levels in the cabin, while still reducing particulate levels. We recommend fractional recirculation as a simple method to reduce occupants’ exposures to particulate matter and CO2 in vehicles. A design with several fractional recirculation settings could allow air exchange adequate for reducing both particulate and CO2 exposures. Developing this technology could lead to reductions in airborne nanoparticle exposure, while also mitigating safety risks from CO2 accumulation.

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Section: Discussionmentioning

confidence: 99%

italicGMD = \frac{{(\frac{1}{c})}^{1.13}}{exp true[\frac{1.13}{2} {ln}^{2} σ_{g} true]} \cdot {true(\frac{EAD response}{CPC response} true)}^{\frac{1}{1.13}}

Section: Methodsmentioning

confidence: 99%

Simultaneously reducing CO2 and particulate exposures via fractional recirculation of vehicle cabin air

Jung

Grady

Victoroff

et al. 2017

Atmospheric Environment

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“…SPN (> 30 nm) accounted 8% of total PN over both FTP and US06 cycles. Geometric mean diameters were obtained using PS/PN ratio following the method by Pham and Jung (2016). For GDI vehicles, geometric mean diameter tends to be larger over FTP cycle compared to US06, while it was not distinguishable for PFI vehicles between two types of cycles ( Fig.…”

Section: Emission Ratesmentioning

confidence: 99%

Investigation of alternative metrics to quantify PM mass emissions from light duty vehicles

Xue

Quiros

et al. 2017

Journal of Aerosol Science

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We evaluated the performance of six alternative particulate matter (PM) metrics relative to the regulatory gravimetric method during chassis dynamometer testing of five light-duty vehicles over the Federal Test Procedure (FTP) and Supplemental FTP (US06) cycles. Alternative metrics included three mass-based metrics including black carbon (BC), two suspended PM mass using integrated particle size distribution (IPSD) method, and three number/surface-based metrics including total particle number (PN), solid particle number (SPN), and particle active surface area (PS). The results showed PM emissions over the FTP cycle were dominated by solid particles on a mass basis (BC to PM ratio = 0.6 ± 0.5), whereas over the US06 cycle were dominated by semi-volatile particles (BC to PM ratio = 0.2 ± 0.2). Moderate to strong correlations were reported between the gravimetric method and the six alternative metrics for FTP and US06 cycles separately (R 2 = 0.69-0.91), i.e. the best-fit lines were strongly dependent upon the cycle. On the other hand, the six alternative PM mass and number metrics exhibited moderate to strong correlations regardless of the test cycle (R 2 = 0.66-0.98). We attribute the observed cycle dependency between alternative metrics and the gravimetric mass method to the greater gravimetric sensitivity to organic and semi-volatile PM than for most alternative metrics. 1066 (CFR, 2011, 2012). With the recent adoption of the Low Emission Vehicle (LEV) III emission standards in California, which

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“…However, that is an incorrect statement in a rigorous term. The unit should have been mm 1.13 /cm 3 , as the response of EAD correlates with electrical mobility diameter to the power of 1.13 instead of 1 for the size range of 0.01-1 µm [28,29].…”

Section: Instrumentsmentioning

confidence: 99%

Reducing Mobile Air Conditioner (MAC) Power Consumption Using Active Cabin-Air-Recirculation in A Plug-In Hybrid Electric Vehicle (PHEV)

Brewer

Pham

et al. 2018

WEVJ

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Air conditioner power consumption accounts for a large fraction of the total power used by hybrid and electric vehicles. This study examined the effects of three different cabin air ventilation settings on mobile air conditioner (MAC) power consumption, such as fresh mode with air conditioner on (ACF), fresh mode with air conditioner off (ACO), and air recirculation mode with air conditioner on (ACR). Tests were carried out for both indoor chassis dynamometer and on-road tests using a 2012 Toyota Prius plug-in hybrid electric vehicle. Real-time power consumption and fuel economy were calculated from On-Board Diagnostic-II (OBD-II) data and compared with results from the carbon balance method. MAC consumed 28.4% of the total vehicle power in ACR mode when tested with the Supplemental Federal Test Procedure (SFTP) SC03 driving cycle on the dynamometer, which was 6.1% less than in ACF mode. On the other hand, ACR and ACF mode did not show significant differences for the less aggressive on-road tests. This is likely due to the significantly lower driving loads experienced in the local driving route compared to the SC03 driving cycle. On-road and SC03 test results suggested that more aggressive driving tends to magnify the effects of the vehicle HVAC (heating, ventilation, and air conditioning) system settings. ACR conditions improved relative fuel economy (or vehicle energy efficiency) to that of ACO conditions by ~20% and ~8% compared to ACF conditions for SC03 and on-road tests, respectively. Furthermore, vehicle cabin air quality was measured and analyzed for the on-road tests. ACR conditions significantly reduced in-cabin particle concentrations, in terms of aerosol diffusion charger signal, by 92% compared to outside ambient conditions. These results indicate that cabin air recirculation is a promising method to improve vehicle fuel economy and improve cabin air quality.

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Alternative metrics for spatially and temporally resolved ambient particle monitoring

Cited by 7 publications

References 23 publications

Simultaneously reducing CO2 and particulate exposures via fractional recirculation of vehicle cabin air

Simultaneously reducing CO2 and particulate exposures via fractional recirculation of vehicle cabin air

Investigation of alternative metrics to quantify PM mass emissions from light duty vehicles

Reducing Mobile Air Conditioner (MAC) Power Consumption Using Active Cabin-Air-Recirculation in A Plug-In Hybrid Electric Vehicle (PHEV)

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