Soot Measurements in a Simulated Engine Exhaust Using Laser-Induced Incandescence

Abstract

Soot mass concentrations were measured with laser-induced incandescence (LII) in a nonreacting ow. The behavior of the LII signal with respect to soot concentration, particle size, and temperature was isolated with the use of a controllable soot-generating device. This device can simulate a hot, low-soot-concentration environment similar to that of a jet engine exhaust. Reduction of interference signals and high detection sensitivity were achieved with the use of a Nd:YAG laser at its fundamental wavelength and broadband detection from 570 to » 850 nm.The LII signals were nearly proportional to soot concentration over 4 orders of magnitude, with a soot detection limit of better than » 1 part per trillion (» 2 ¹g/m 3 ). The detection setup was designed, according to a model of the LII process, to reduce dependence on local gas temperature and soot particle size. Experimental results agreed with the model predictions in terms of particle size dependence, and negligible temperature dependence (beyond gas density effects) was seen for gas temperatures from 70 to 300 ± C.

Laser induced incandescence for soot concentration measurements in turbine engine exhausts

“…This arrangement allows the beam along the entire width of the plume, about 0.5 m, to be captured in one image frame. For calibrating the LII system, a "soot generator" was developed that produces a steady stream of simulated soot aerosol 7 at a known mass concentration. Fig.…”

(KA-2) Diagnostics for the Measurement of Particulate Matter Emissions from Reciprocating Engines

“…Of these, light scattering is by far the most sensitive technique. (As a point of reference, LII has been estimated to have a sensitivity on the order of a few parts per trillion [21].) The opacimeter is the least sensitive, but there are several ways that this can be improved.…”