Smoke Point Is Adequate for Engineering Soot Prediction: A Demonstration

A semi-empirical Laminar Smoke-Point (LSP) model is used to compare soot predictions against the experimental Laser-Induced Incandescence (LII) based measurements in a lab-scale CFM-56 aircraft combustor with liquid jetA1 as fuel and dilution jets. The soot model, which has so far been used in the fire dynamics domain for laminar flames, has now been extended to an industrial burner using LES. Comparison of the averaged Discrete Phase Model (DPM) droplet distribution against the backlight spray imaging shows a good comparison. The simulation displays some degree of spray asymmetry similar to the data due to the wall confinement effect. A comparison of the thermal field with the instantaneous flame image shows a good match in terms of the radial and axial extent of the flame front. Finally, a comparison of the soot volume fraction predicted by the model with the LII data shows an acceptable qualitative and good quantitative match. The soot field immediately downstream of the swirler shows a near-uniform soot field at an angle of about 98° which is close to the measured spray angle. The radial extent of the soot at the widest section matches closely with the data. However, the model predicts an axial extension of the soot further downstream and up to the dilution jets which is not observed in LII. This could be due to the presence of Poly-Aromatic Hydrocarbons (PAH) in these regions which are not picked up in LII due to the spectral filter or could be due to the laser sheet attenuation by the liquid fuel on the quartz window.