Both homogeneous and inhomogeneous ignition modes of n-heptane were studied using high-speed imaging in a high-pressure shock tube (HPST). n-Heptane, a fuel with a strong negative temperature coefficient (NTC) behavior, was mixed with 4%-21% oxygen in argon or nitrogen and ignited at both low (< 1000 K) and high (> 1000 K) temperatures, at elevated pressures (>10 atm). Ultraviolet (UV) images were captured through a sapphire shock tube end-wall using a high-speed camera and a UV intensifier. Both homogeneous and inhomogeneous auto-ignition were observed. The current study demonstrates the capability to study auto-ignition inhomogeneity using high-speed imaging in a high-pressure shock tube.
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