Study on evaporation and combustion of n-heptane droplet in a heated tube

When a suspended droplet of n-heptane burns in a heated tube, oscillatory flame is formed at the tube exit due to periodic droplet dripping and colliding with hot wall, along with heat and mass transfer processes among solid, gaseous and liquid. In order to understand the mechanism of oscillatory flames, an evaporation model of suspended droplet and deposited liquid film were established, with careful consideration of both evaporation and combustion processes. Experiments and calculations were conducted to examine the effects of vaporization on heat and mass transfer processes for droplet and liquid films. Results indicate that oscillatory flames result from both suspension and dripping processes. Increasing fuel flow rate can increase flame temperature and benefit flame stability. While increasing air velocity shortens oscillating period and impedes flame stability.