Fast Exhaust Nephelometer (FEN)
Measurement of particle emissions from engines with intra-cycle time resolution
· Resolution of 0.5° of crank shaft rotation.
· Enables intra-cycle time measurements.
· Soot concentrations within individual engine cycles can be resolved.
· Overcomes variation between cycles.
· High sensitivity even at low PM conc.
Vehicle exhaust is considered a significant source of anthropogenic particulate matter (PM), as especially diesel engines release large amounts of black carbon or soot into the atmosphere contributing to overall global warming and the melting of the Earth’s ice caps. To counteract climate change, regulatory authorities around the world have released various engine emission standards to reduce PM emission from diesel engines.
Soot emissions from direct injection engines, e.g. diesel engines, hold a delicate balance between formation and oxidation reactions, which are sensitive to details of mixture formation inside the cylinder, and therefore vary from one cycle to the next. Conventional exhaust emissions measurements, such as gravimetric filter sampling and particle counting instruments; cannot resolve inter- or intra-cycle variations in particle emissions; however, such variations are often critical during transient engine operations where only few cycles may disproportionally affect the total exhaust soot.
Researchers at The University of British Columbia have developed a device using light scattering to measure particulate matter concentration and size with a time resolution of < 1 ms or 0.5° crank shaft rotation. Due to the excellent time resolution achieved, the Fast Exhaust Nephelometer (FEN) overcomes earlier measurement limitations, as intra- and inter-cycle measurements can now be detected and resolved. Operating at atmospheric pressure and sampling near the engine exhaust port, the FEN uses a laser diode to illuminate a small measurement volume, and the scattered light is focused on two amplified photodiodes (at 45° and 135° angles) providing high detection sensitivity even at extremely low PM concentrations at the solution line or during raw exhaust measurements.