正庚烷液滴在微细直管中的燃烧特性实验

为了解微细直管对液滴形成和燃烧稳定性的影响,采用正庚烷作为燃料在内径为4mm的石英直管中的进行了实验研究.其结果显示:首先在不加热时,容易形成液滴,正庚烷体积流量小于40μL/min 时,火焰稳定性受液滴滴落的影响较大,液滴的蒸发主要受到空气体积流量影响下的火焰位置的影响;大于40μL/min时,液膜形成,火焰受液滴滴落影响不大.其次,管壁加热温度为180℃时,正庚烷体积流量低于60μL/min时难以形成液滴,大于60μL/min时液滴滴落后不形成液膜,液滴的蒸发受空气流速的影响较大,在液滴滴落以及空气流速的影响下,微燃烧器温度的变化对燃料的蒸发产生更大的影响,富燃较贫燃更易形成连续的火焰.空气流速大小对管壁温度影响明显,空气流速越小,管壁温度越高,液滴蒸发速率越大. 

Experiment on combustion characteristics of n-heptane droplets in micro-tube

To understand the effect of micro-tube on the droplet formation and combustion stability, the following researches were performed by using the n-heptane as fuel in 4mm internal diameter quartz tube. Firstly, without heating, the stability of the flame and quartz tube drips was studied. The results showed that without heating, quartz tube was easy to form droplets, and when the n-heptane volume flow rate was lower than 40μL /min, the flame stability was influenced by dripping easily, the evaporation rate of the droplets was mainly affected by the flame position under the influence of the effect of air volume flow rate; when the fuel volume flow rate was larger than 40μL/min, the flame stability was not affected easily by the dripping of droplet due to the formation of liquid film. Secondly, the influences of heating on the droplet formation and the combustion characteristic were studied. It was found difficult to form droplets when the n-heptane volume flow rate was lower than 60μL/min, and when the n-heptane volume flow rate was greater than 60μL/min, the droplet could drip, and film didn't appear when the wall temperature was 180℃. Droplet evaporation was greatly influenced by air velocity; under the influence of air velocity and the droplet dripping, the temperature of micro burner had a greater impact on evaporation rate of droplet. The flame was more easily formed under fuel-rich condition than fuel-lean condition. Hence, air velocity has strong impact on the tube wall temperature, the lower air velocity means the higher wall temperature, the higher evaporating rate of fuel droplet and lower droplets dripping frequency.