Infrared measurements of soot formation in diesel sprays

This paper describes an experimental program in which soot formation was monitored in the near-injector region for a diesel spray. Measurements were made for initial temperatures ranging from 700 to 950 K, pressures of approximately 3 MPa, and injection pressures of approximately 20 MPa. The fuel was normal dodecane. Measurements were obtained at locations ranging from 5 mm from the spray tip to 35 mm from the tip. Soot was monitored using infrared emission between 6 and 12 mu m with a custom-designed infrared spectrometer, and 9.4 mu m was found to be an appropriate wavelength for quantitative measurements of soot mass in the spray. Soot was observed at all locations in the spray. Results from this experimental effort indicate that soot is formed at the radial periphery of the spray and is poorly coupled to the spray's high-momentum central core. Copyright (C) 1996 by The Combustion Institute