In this work we present and apply a mathematical model to simulate the auto-ignition of isolated fuel droplets burning in microgravity conditions. The aim is to demonstrate the fundamental role of the lowtemperature mechanisms on the auto-ignition process and to show that several experimental observations cannot be explained without considering the formation of cool-flames around the burning droplet. Thus, in order to better clarify the importance of the low-temperature chemistry, a detailed kinetic scheme (with hundreds of species and thousands of reactions) was adopted to model the spontaneous ignition of isolated droplets of n-heptane, n-decane, and n-dodecane in air, in a wide range of operating conditions (with environment temperatures from 600 K to 1100 K and pressures from 1 bar to 20 bar). The model was able to correctly identify the typical auto-ignition regimes of n-alkane oxidation. The comparison with the experimental measurements available in the literature was satisfactory: both firststage and total induction times were reasonably captured by the numerical simulations. The simulations confirmed that the low-temperature chemistry plays a role of paramount importance in the auto-ignition process. In particular, the competition between low- and high-temperature mechanisms was found to explain the different types of auto-ignition which can be experimentally observed.

Numerical modeling of auto-ignition of isolated fuel droplets in microgravity

CUOCI, ALBERTO;FRASSOLDATI, ALESSIO;FARAVELLI, TIZIANO;RANZI, ELISEO MARIA
2015-01-01

Abstract

In this work we present and apply a mathematical model to simulate the auto-ignition of isolated fuel droplets burning in microgravity conditions. The aim is to demonstrate the fundamental role of the lowtemperature mechanisms on the auto-ignition process and to show that several experimental observations cannot be explained without considering the formation of cool-flames around the burning droplet. Thus, in order to better clarify the importance of the low-temperature chemistry, a detailed kinetic scheme (with hundreds of species and thousands of reactions) was adopted to model the spontaneous ignition of isolated droplets of n-heptane, n-decane, and n-dodecane in air, in a wide range of operating conditions (with environment temperatures from 600 K to 1100 K and pressures from 1 bar to 20 bar). The model was able to correctly identify the typical auto-ignition regimes of n-alkane oxidation. The comparison with the experimental measurements available in the literature was satisfactory: both firststage and total induction times were reasonably captured by the numerical simulations. The simulations confirmed that the low-temperature chemistry plays a role of paramount importance in the auto-ignition process. In particular, the competition between low- and high-temperature mechanisms was found to explain the different types of auto-ignition which can be experimentally observed.
2015
Cool flame; Detailed kinetics; Droplet; Low-temperature chemistry; Microgravity; Mechanical Engineering; Chemical Engineering (all); Physical and Theoretical Chemistry
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11311/970697
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