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

Abstract

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%.

Inertial Impaction Technique for the Classification of Particulate Matters and Nanoparticles: A Review

“…This includes the slit virtual impactor assembled with an orifice installed upstream of the acceleration nozzle to concentrate the minor flow at the center of the collection probe (Lim K.S. and Lee K.W., 2006;Lee H. et al, 2014) or the impactor with three-partitioned horizontal inlet (Zahir M.Z. et al, 2018).…”

Investigation of collection efficiency of round-nozzle impactors at different atmospheric pressures and temperatures

“…The impactor collection efficiency was estimated by using the statistical Lagrangian particle tracking (SLPT) approach [15][16][17][18]. As shown in Fig.…”

Enhancement of Collection Efficiency of an Inertial Impactor Using an Additional Punched Impaction Plate

“…Based on simulation results with or without particle collection, the statistical Lagrangian particle-tracking (SLPT) model was used to calculate collection efficiency, as presented in Eq. (1) (Kim and Yook, 2011;Kim et al, 2014b;Lee et al, 2014;Park et al, 2015). Here, Δr = R in /(N in -1) is the distance between particles, R in is the inlet radius, N in is the number of particles arranged in the radial direction, r i = (i -1)Δr is the particle position in the radial direction from the center, i is the particle index and f i is the particle collection index.…”