In-situ laser-induced incandescence of soot in an aero-engine exhaust: Comparison with certification style measurements

In-situ (non-intrusive) laser-induced incandescence measurements of soot in the exhaust of a current technology, mid-size turbofan aero-engine running on a sea-level test bed have been performed at the same time as the extractive measurements required for engine emissions certification. Although laser-induced incandescence and the filter paper reflectance measurement specified for engine certification provide different measures of soot concentration which are not directly comparable, trends with engine power are the same. At high engine power, agreement between mass concentration derived from an LII measurement along a diameter through the exhaust plume and that derived from the SAE Smoke Number measured by the filter paper technique was well within the uncertainty of the standard technique. At low power, only the non-intrusive method could measure the levels of soot produced. The interpretation of line-of-sight integrated laser-induced incandescence data from a real engine exhaust is discussed.