A Detailed Kinetic Model for Calculation of the Soot Particle Size Distribution Function

University dissertation from Division of Combustion Physics Department of Physics Lund Institute of Technology

Abstract: The soot particle size distribution was studied via numerical simulation under diesel like engine conditions using a detailed kinetic soot model. Two different mathematical methods of the soot model description have been used in this work. In the first part of the work, the method of moments is presented. In addition, a so called sectional method for the soot particle size distribution function in diffusion flames has been developed. Both of the methods have been employed for simulations in diesel like engine operating conditions. The commercial computational fluid dynamics (CFD) codes have been used in order to obtain more information of temporal and spatial soot particles size distribution inside the enclosed chamber. The predictive capabilities of the model have been validated versus experimental data for different fuels and different initial and boundary conditions. The subject of the calculations was the influence of these different values on the soot particle formation. The sectional model was validated with laboratory diesel fuel jet flame data for an optically accessible constant-volume combustion vessel, where test data at high pressure and high temperature are available. For the validation of the soot method of moments, different optical measurements of the in-cylinder soot have been presented. The combustion process itself is simulated using a progress variable model for the auto ignition of a diffusion flamelet, with the sectional model calculations. Source terms for soot particle inception, surface growth, and oxidation describing the interaction of the particles with the gas phase are taken from a flamelet library for both models. The coagulation of particles is calculated as part of the CFD calculations, based on the mean of the weighted soot mass fractions. The computations demonstrate the complex interaction between gaseous species, soot production, temperature, etc. Exclusion of any of the above effects can lead to significant errors.

  This dissertation MIGHT be available in PDF-format. Check this page to see if it is available for download.