Investigating Soot Parameters in an Ethane/Air Counterflow Diffusion Flame at Elevated Pressures

Abstract

Soot emissions from diesel engines and gas turbines are influenced by the combustion environment. Pressure is one of the parameters which affects particulate emissions and these effects are poorly understood on soot parameters. In this work, pressurized counterflow diffusion flame of ethane and air has been investigated using two angle light scattering and extinction technique. A counterflow diffusion flame has been stabilized from 2 to 5 atm in a pressure vessel which can provide optical access from 10 to 165° in angular direction. Global strain rate (a) of 30 s-1 is maintained at all pressures by adjusting the inlet flows. Scattering measurements are performed at two angles (45° and 135°) and Rayleigh-Debye-Gans theory for Fractal Aggregates (RDG-FA) has been used to determine soot parameters from light scattering and extinction data. By combining the scattering at 135° with laser extinction measurements, path averaged soot volume fraction (fv), mean primary particle diameter (̅̅̅) and particle number densities (np), along the axis of the counterflow flame are calculated. Local soot volume fraction (fv,local) profiles are also measured using diffuse light 2D line of sight attenuation technique. Peak value of fv increases from 0.3 ppm to 8 ppm as the pressure is raised from 2 to 5 atm. Primary particle size (̅̅̅) also increases with pressure where peak primary particle size of 11 nm at 2 atm rises to 38 nm at 5 atm. Population average radius of gyration (Rg) increases with pressure while the number densities (np) of primary particles decrease due to coalescence.

Effects of Ambient Oxygen and Density on Primary Soot Size under Diesel-Like Conditions Using a Lagrangian Soot Tracking Model

“…However, experimental studies on SVF have shown that decreasing ambient oxygen [58] and increasing ambient density [62] can increase SVF in diesel spray flame. In addition, measurement of primary soot size in canonical flame setups also showed similar findings regarding the effect of oxygen [63] and ambient density [64][65][66] on primary soot sizes.…”

Extinction Imaging Diagnostics for In Situ Quantification of Soot within Explosively Generated Fireballs

“…LII can provide data on a thin, 2D slice and can be performed at high repetition rates [25]. Multi-angle scattering is another common laser technique, which quantifies soot morphology based on intensity variations as a function of scattering angle and can also be applied for 2D imaging [26][27][28]. LII requires one or more high-power pulsed lasers, while multi-angle scattering relies on a series of detectors located at various angles from the incoming laser radiation.…”

Planar Light Extinction Measurement of Soot Volume Fraction in Laminar Counterflow Diffusion Flames

“…In addition, the diffuse layout is observed to have better performance in the presence of beam steering compared with the collimated layout (Thomson et al, 2008). Amin and Roberts performed the diffuse layout for planar extinction measurement of SVF in CDFs (Amin and Roberts, 2020). However, the collimated layout has not been attempted in counterflow flame.…”