Visualization of Defect Particle Transmission to the Major Flow of a Slit Virtual Impactor

Kim, T. K.; Seshadri, S.K.; Kihm, Kenneth D.; Phares, Denis J.; Mclntyre, P.

doi:10.1080/027868290505161

Cited by 12 publications

(9 citation statements)

References 9 publications

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“…McFarland (2002) presented results that demonstrated the adverse effect of CTP on LSVI performance, and Kim et al (2004) observed a particle with a Stokes number of about 50 crossed the central plane of a slot virtual impactor. Herein, previous observations are quantified by consolidating recent experimental data on slot virtual impactors (Ding et al 2000(Ding et al , 2001Demokritou et al 2002;Haglund and McFarland 2004).…”

Section: Introductionmentioning

confidence: 99%

CFD Study on the Effects of the Large Particle Crossing Trajectory Phenomenon on Virtual Impactor Performance

Hari

McFarland

Hassan

2007

Aerosol Science and Technology

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Two-dimensional CFD simulations were performed on a fullsection numerical model of an as-built slot virtual impactor prototype and its completely symmetric ideal counterpart. The simulations reproduce the trends of the experimentally observed performance including verification of a third region in the transmission efficiency curve, which is a drop-in transmission efficiency for large particle sizes. Visualization of simulated particle tracks show this decrease is attributed to a crossing trajectory phenomenon, whereby larger particles that acquire enough inertia in a chamfered acceleration nozzle, crossover the vertical mid-plane and impact on the opposite-side wall, particularly on the wall of the receiver section. Some experimental data presented in the literature for rectangular slot and round-nozzle virtual impactors with chamfered 45• half-angle acceleration nozzles (similar to the geometry tested herein), show a similar drop-in transmission efficiency that commences at a particle Stokes numbers of about 6. However, many studies do not demonstrate the drop in transmission efficiency because wall losses are not taken into account. The Reynolds number, based on the acceleration nozzle size and velocity, does not noticeably affect the onset of the phenomenon. The crossing trajectory phenomenon can severely restrict the size range over which a virtual impactor can be used as an efficient particle concentrator. Geometrical asymmetry from dimensional tolerance considerations in the construction of a virtual impactor exacerbates the impact of the crossing trajectory phenomenon.

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Section: Introductionmentioning

confidence: 99%

CFD Study on the Effects of the Large Particle Crossing Trajectory Phenomenon on Virtual Impactor Performance

Hari

McFarland

Hassan

2007

Aerosol Science and Technology

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“…1, the experimental setup consists of a slit virtual impactor, a turntable dust feeder, a modified vibrating orifice aerosol generator (VOAG), a laser illumination system, and a CCD camera coupled to a VHS recorder and a PC. The details of the design and fabrication of the virtual impactor were described in the previous study (Kim et al, 2004), so only the important dimensions are discussed here. The aerosol is accelerated into the separation region through a convergent section having an angle of convergence of 60 • and a final slot width of 0.3 mm.…”

Section: Methodsmentioning

confidence: 99%

“…There exist numerous studies devoted to experimental and numerical characterization of circular and slit virtual impactors operated under dilute conditions. We refer the reader to Marple and Chein (1980), Loo and Cork (1988), Sioutas, Koutrakis, and Burton (1994), Chen and Yeh (1987), Gotoh and Masuda (2000), Kim, Seshadri, Kihm, Phares, and McIntyre (2004) and references therein for discussions of these. In a departure from conventional use of virtual impactors, Fu, Gupta, McIntyre, and Phares (2003) demonstrated that a slit virtual impactor may be employed as a large particle filter for processing superconductor precursor powders.…”

Section: Introductionmentioning

confidence: 99%

“…The first criterion was studied by Kim et al (2004), who used visualization techniques to examine the transmission to the major flow of particles larger than twice the cutoff diameter of the device. These defect particles were observed for Stokes numbers as large as Stk = 50, even though the cutoff Stokes number of the device was measured to be 0.82.…”

Section: Introductionmentioning

confidence: 99%

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Performance of a slit virtual impactor operated at high particle mass loading

Seshadri

Phares

Kim

et al. 2005

Journal of Aerosol Science

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“…The distance between the two nozzles was denoted as S, the length of the acceleration nozzle as T, the width of the orifice as d, the width of the inlet as D, the distance between the orifice and the acceleration nozzle as L, and the span of the slit nozzle as l. Table 1 lists the values of the width of the acceleration nozzle, flow rate through the acceleration nozzle (Q), and corresponding Reynolds number (Re), which were tested in this study. In general, the performance of a slit virtual impactor is affected by its dimensions (Ding and Koutrakis 2000;Kim et al 2004). In the present study, the geometric dimensions were determined as multiples of the width of the acceleration nozzle, that is, W c /W a = 1.4, S/W a = 1.5, T/W a = 1.1, d/W a = 1, and D/W a = 6, based on the studies of Loo and Cork (1988) and Ding and Koutrakis (2000).…”

Section: H Lee Et Almentioning

confidence: 99%

Effect of an Orifice on Collection Efficiency and Wall Loss of a Slit Virtual Impactor

Lee

Kim

et al. 2013

Aerosol Science and Technology

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The effect of an orifice on the collection efficiency and wall loss of a slit virtual impactor was investigated both numerically and experimentally. The ratios of the collection nozzle width (W c ), distance between acceleration nozzle and collection nozzle (S), length of acceleration nozzle (T), inlet width (D), and nozzle span (l) to the acceleration nozzle width (W a ) were fixed at W c /W a = 1.4, S/W a = 1.5, T/W a = 1.1, D/W a = 6, and l/W a = 10, respectively. The minor-to-total flow ratio was set to 0.1 in laminar flow regime. The collection efficiency and wall loss of the slit virtual impactor were found to be characterized by the square root of the Stokes number. For the slit virtual impactor without an orifice, the square root of the Stokes number corresponding to the cut-off diameter was determined to be (Stk 50 ) 1/2 = 0.77 and the maximum wall loss at the collection nozzle reached 30% or 40%. When an orifice having the same width as the acceleration nozzle was placed upstream of the acceleration nozzle at a distance of 20W a , the value of (Stk 50 ) 1/2 decreased to 0.68 and the wall loss at the collection nozzle decreased below 5%.

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Visualization of Defect Particle Transmission to the Major Flow of a Slit Virtual Impactor

Cited by 12 publications

References 9 publications

CFD Study on the Effects of the Large Particle Crossing Trajectory Phenomenon on Virtual Impactor Performance

CFD Study on the Effects of the Large Particle Crossing Trajectory Phenomenon on Virtual Impactor Performance

Performance of a slit virtual impactor operated at high particle mass loading

Effect of an Orifice on Collection Efficiency and Wall Loss of a Slit Virtual Impactor

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