ISSN Online: 2379-1748
ISBN Flash Drive: 978-1-56700-469-4
ISBN Online: 978-1-56700-470-0
Second Thermal and Fluids Engineering Conference
TURBULENT INHOMOGENEOUS AUTOIGNITION OF POLYDISPERSED N-HEPTANE DROPLETS: AN EXPERIMENTAL STUDY
Аннотация
We present experimental data on the autoignition of polydispersed droplets pure liquid n-heptane released
axisymmetrically from a circular nozzle into a confined turbulent co-flow of high temperature air at atmospheric
pressures. Our aim in this work is to examine the effect of flow inlet conditions on the emergence
and behaviour of autoignition in the presence of flow inhomogeneities. Typically, autoignition is observed
in the form of well-defined localised spots occurring randomly along the length of the tubular reactor. We
record the autoignition location and delay times (based on the residence time from the fuel injector to the
autoignition spots) as a function of the bulk temperature and velocity of the co-flowing air stream, and of the
liquid fuel injection velocity. The near injection fuel droplet size distribution is also measured. It is established
that the axial autoignition length shifts upstream (i.e. closer to the fuel injector) with increasing bulk air temperature;
and moves downstream with increasing bulk air co-flow velocity at a constant liquid fuel injection
velocity. The corresponding autoignition delay time decreases with increasing bulk air temperature and bulk
air velocity, contrary to expectations from pre-vaporized n-heptane autoignition in an identical facility. Such
experimental data can be used for developing and validating advanced models of non-premixed two-phase
turbulent combustion and chemically reacting flows.