Controlling nucleation and growth of nanodroplets in supersonic nozzles

Abstract

We used small-angle neutron scattering (SANS) to measure soot development in one-dimensional, laminar premixed flames. Scattering spectra were collected for two sooting ethylene/oxygen/argon flames at six positions above the burner surface. A detailed analysis of the scattering signals yielded the basic properties of the soot size distributions as a function of position. The experiments demonstrate that SANS can be used to extract spatially resolved, quantitative information about incipient soot formation and growth with better particle size resolution than light scattering and extinction.

Overview: Homogeneous nucleation from the vapor phase—The experimental science

“…176,177 The use of different nozzle shapes enabled isothermal nucleation rate measurements. 178 Although Streletzky et al 179 incorporated a nucleation pulse into a supersonic nozzle by shaping the sidewalls, their results demonstrated the challenges associated with expanding the gas fast enough downstream of the nucleation pulse to balance the heat release by the growing droplets while simultaneously avoiding a second, spontaneous nucleation event.…”

Vapor–gas/liquid nucleation experiments: A review of the challenges

“…The maximum experimental value of the nucleation rate, J max , in diffusion chambers can be measured using an obvious relation J theor /N theor = J max /N exp , where J theor is maximum theoretical nucleation rate; N theor and N exp are the theoretical and experimental FDC particle concentrations, respectively (Hyvarinen et al, 2006;Wagner & Anisimov, 1993). That relationship can also be used for J max measurements using a supersonic nozzle (Streletzky, Zvinevich, Wyslouzil, & Strey, 2002). The current FDC scheme has been used for vapor nucleation rate measurements at total pressures from 0.03 to 0.50 MPa.…”

Modeling of H2O/D2O Condensation in Supersonic Nozzles

“…Alternatively, the depletion of vapor from the gas phase, or the appearance of the condensate has been directly measured using spectroscopy (Tanimura et al 1995;Paci et al 2004;Tanimura et al 2005;Tanimura et al 2007). Finally, visible light scattering has been used to detect the appearance of the aerosol, and follow, at least qualitatively, its continued growth (Stein and Wegener 1967;Streletzky et al 2002;Karlsson et al 2007). Despite this extensive experimental work, none of these measurements provides detailed quantitative information on the aerosol itself, i.e., the size distribution of the particles formed during condensation.…”

“…The heat released to the flow by the phase transition is often large enough to increase the static pressure, density, and temperature, above that expected for the isentropic expansion of the gas mixture. The spatial variation of these state variables has been followed using static pressure probes (Stein and Wegener 1967;Wyslouzil et al 2000;Heath et al 2002;Streletzky et al 2002;Khan et al 2003;Kim et al 2004), interferometry (Wyslouzil et al 1994;Lamanna 2000), or spectroscopy (Tanimura et al 1995;Tanimura et al 1996;Tanimura et al 1997;Paci et al 2004;Tanimura et al 2005, Tanimura et al 2007), respectively. Alternatively, the depletion of vapor from the gas phase, or the appearance of the condensate has been directly measured using spectroscopy (Tanimura et al 1995;Paci et al 2004;Tanimura et al 2005;Tanimura et al 2007).…”