Soot Model Calibration Based on Laser Extinction Measurements

In this work a detailed soot model based on stationary flamelets is used to simulate soot emissions of a reactive Diesel spray. In order to represent soot formation and oxidation processes properly, a calibration of the soot reaction rates has to be performed. This model calibration is usually performed on basis of engine out soot measurements. Contrary to this, in this work the soot model is calibrated on local soot concentrations along the spray axis obtained from laser extinction chamber measurements. The measurements are performed with B7 certification Diesel and a series production multihole injector to obtain engine similar boundary conditions. In order to ensure that the flow and mixture field is captured well by the CFD-simulation, the simulated liquid penetration lengths and flame lift-off lengths are compared to chamber measurements. On this basis the soot model is calibrated to capture the measured soot distribution along the spray axis for a variation of ambient temperature, ambient density and injection pressure. However, the maximum measureable soot concentration is limited with the laser extinction method. Due to the high sooting Diesel fuel saturation effects are observed for certain measurement points.