單一純油料及混合純油料之燃燒行為

Abstract

本實驗是利用噴墨壓電式液滴產生器產生自由液滴，將各大類純物質打入高溫石英玻璃管內燃燒。第一部分為單一純油料的燃燒行為，包含甲醇、乙醇、丙醇、異丙醇、丁醇、二丁醇、正辛醇及十二醇等醇，烷類有正庚烷、異辛烷、十二烷、十四烷及十六烷，並且將MTBE與烷類做比較，芳香烴則包括苯、甲苯、二甲苯及1-甲基萘，歸納出探討點火延遲、燃燒時間及燃燒速率之趨勢，以及由物理及化學性質影響之關係。第二部分為混合純油料的燃燒行為，觀察高低沸點差造成的燃燒特性。 實驗結果發現，物質的燃燒行為受到沸點、蒸發潛熱與化學結構影響。一般來說，單一純油料之液滴燃燒特性由碳數及沸點控制，但在蒸發潛熱的影響下，低碳數醇類之點火延遲受到沸點溫度的影響較小；而沸點相近的正庚烷與異辛烷，由於化學結構的差別，造成點火延遲與火焰外觀有明顯的差異。混合純油料中，火焰縮口隨高沸點組份增加而提早發生，若低沸點組份比例過低，將造成點火延遲的大幅增加，無論是同質或異質的混合純油料，都會有微爆發生，但都只是雜質所形成的微爆，對燃燒速率沒有太大的影響。

This experiment applies Ink-Jet Printing method by using piezoelectric drop generator to produce free falling droplets into a high temperature quartz glass tube. The following materials were studied: alcohols such as methanol, ethanol, propanol, iso-propanol, butanol, 2-butanol, octanol and dodecanol as well as alkanes such as heptane, iso-octane, dodecane, tetradecane and hexadecane, compared with MTBE. The usages of aromatics hydrocarbons include benzene, toluene, m-xylene and 1-methylnaphthalene. It summarizes the trend of ignition delay, burning time and burning rate influenced by different chemical and physical properties. The second part observes the burning behavior in terms of high and low boiling point in varied fuel mixtures According to present experiment results, the combustion behavior is influenced by boiling point, latent heat of vaporization and chemical structure. Generally, the burning characteristic of pure fuels is controlled by carbon number and boiling point. However, by the effect of Latent Heat of Evaporation, the low-c alcohols’ ignition delay have slighter influence from boiling point. Others like Heptane and iso-octane, having similar boiling point while there flame pattern and ignition delay make significant difference due to the discrepancy of chemical structure. The higher proportion of high-boiling point constituent in the droplet, the earlier the flame shrinkage takes place. Ignition delay will be increased sharply due to low proportion of low-boiling point ingredients. The microexplosion in droplets isn’t related to whether it’s pure or mixed but impurities, which don’t promote burning rate as well.