Experimental study on n-heptane droplet combustion in a micro-T ube

Formation and flame stability of heptane droplets in a quartz tube with inner diameter of 4mm were experimentally studied. In the case of no external heating, droplet dropping behavior and flame stability are discussed. The results show that droplet is easily formed at tip of the capillary tube under no external heating condition, and flame is mainly influenced by droplet falling when heptane flow rate (Qf) is lower than 40ul/min, flame is stable with Qf=20ul/min and extinguish with dripping when Qf=30ul/min. when Qf is larger than 40ul/min, the flame is not easily affected due to formation of fuel film on the tube wall. Then, flame stability of heptane droplet was studied under external heating condition. It was found that when Qf is smaller than 60ul/min, no droplet is formed due to the higher wall temperature when Qf is larger than 60ul/min, no liquid film is formed, The flame becomes more stable under fuel-rich condition than the fuel-lean condition. Heat recirculation can effectively preheat the inner tube and can increase heptane evaporation, but flame oscillation may occur due to droplet falling and fast evaporation.