Probing PAH Formation from Heptane Pyrolysis in a Single-Pulse Shock Tube

To improve our capabilities to model surrogate fuels, particularly in respect to polycyclic aromatic hydrocarbons (PAHs) and soot formation, the pyrolysis of n-heptane is studied in a single-pulse shock across a wide temperature range (900-1700 K) at 20 bar nominal pressure and 4 ms residence time. Three different initial fuel mole fractions are considered, 103, 502, and 2000 ppm of n-heptane in argon. Fuel and intermediate species, including aromatics up to three-ring structures, are measured using gas chromatography and mass spectrometry diagnostics. An ongoing detailed chemical kinetic model for PAH chemistry has been updated to successfully capture the fuel decomposition, the formation of small hydrocarbons, and the concentration of the main PAH products. Major reaction pathways to PAHs are highlighted as well as the role of important intermediate species.