生質柴油預混醇類於微重力下燃燒研究

Burning characteristics of biodiesel mixed with alcohol in microgravity condition

姚嘉俊(Chia-Chun Yao)

指導教授 ： 潘國隆

國立臺灣大學/工學院/機械工程學研究所/碩士(2013年)

https://doi.org/10.6342/NTU.2013.01638

摘要

本文使用落塔(drop tower)方式進行0.68 s的自由落體以達到微重力環境，固定液滴尺寸為535 μm，並利用電熱絲點火觀察單組份液滴及雙組份液滴於微重力環境下燃燒現象(包括:液滴直徑變化、平均燃燒速度、微爆(micro-explosion)及火焰熄滅等)。實驗所使用之單組份燃油分別為甲醇、乙醇、異丙醇、十六烷、十二烷、柴油及生質柴油，而雙組份之燃油為生質柴油預混乙醇之燃燒。為使量測液滴尺寸上有一致性且誤差減至最低，本實驗使用Matrox Inspector 8.0之影像軟體內建的自動量測邊界。

實驗結果發現，將生質柴油預混醇類之液滴打上懸掛線上時，會有類似液泡的不均勻(non-uniform)現象發生，此時不管在重力或是微重力下燃燒，皆會產生微爆。而不均勻之現象與環境之相對濕度有關，隨著相對濕度越高，產生出之液泡就越大。在相同的相對濕度下，液泡會隨著醇類的碳數增加而越小；且隨著醇類重量百分比濃度上升，產生出之液泡就越大；同時也發現，液滴內部的液泡會隨著時間越來越小，當液滴內部之液泡消失時，燃燒過程中微爆現象不會產生。
當相對濕度為50 %時，異丙醇25 %之組份就會產生微爆，將相對濕度降至38 %時，異丙醇之組份可升到45 %才會產生微爆，因此可以觀察到添加異丙醇可以使燃燒速率增加，異丙醇組份在25 %至35 %區間之燃燒速率趨於平緩，而異丙醇40 %之燃燒速率有下降的趨勢。而乙醇25 %之組份，從相對濕度50 %降至40 %時，依然會產生微爆。

關鍵字

微重力 ； 自由落體 ； 生質柴油 ； 醇類 ； 微爆 ； 碳微粒

並列摘要

The research uses the method called “drop tower” to undergo a 0.68s free-falling body and reach the microgravity environment. Confining the droplet diameter to 535 μm and using hot wire to ignite the droplet, we observe the phenomena of single component droplet and binary fuel droplet burning in microgravity environment (including the evolution of droplet diameter, burning rate, micro-explosion, and extinguish). The single component fuels used in the experiment are methanol, ethanol, propanol, hexadecane, dodecane, diesel, and biodiesel. The binary fuel used in the experiment is the premixed liquid of bio-diesel and ethanol. To ensure the consistency of the target droplets and to minimize the experiment error, this experiment use the built-in function of a image process software, Matrox Inspector 8.0, to measure boundaries.
In the experiment results, we found that when we deploy the droplet of biodiesel mixed with alcohol onto fiber, the non-uniform phenomenon similar to liquid bubble occurs. In this situation, whether under the condition of gravity or microgravity, micro-explosion is sure to occur while burning. And this non-uniform phenomenon is related to the relative humidity of the environment. Along with the rise of relative humidity, the liquid bubble gets bigger and bigger. Under the same relative humidity, liquid bubbles would become smaller when the carbon number of alcohol increases. Also, with the increase of alcohol concentration in percent by weight, the size of liquid bubbles become bigger. We also discovered that the liquid bubble substance inside the droplet would diminish with time. When the liquid bubble substance vanishes, so does the micro-explosion during burning.
When the relative humidity is 50 %, the 25 % by weight 2-Propanol solution will have micro-explosion. After lowering the relative humidity to 38 %, micro-explosion would not occur until the percentage of weight of 2-Propanol solution was raised to 45 %. Therefore, we can observe that adding 2-Propanol can lead to the increase of burning rate. The burning rate of between 25~30 % by weight 2-Propanol solution does not change significantly while it tends to decrease when the weight percentage comes to 40%. On the other hand, 25 % by weight ethanol solution would still experience micro-explosion after lowering the relative humidity from 50 % to 40 %.
In the experiment results, we found that when we deploy the droplet of biodiesel mixed with alcohol onto fiber, the non-uniform phenomenon similar to liquid bubble occurs. In this situation, whether under the condition of gravity or microgravity, micro-explosion is sure to occur while burning. And this non-uniform phenomenon is related to the relative humidity of the environment. Along with the rise of relative humidity, the liquid bubble gets bigger and bigger. Under the same relative humidity, liquid bubbles would become smaller when the carbon number of alcohol increases. Also, with the increase of alcohol concentration in percent by weight, the size of liquid bubbles become bigger. We also discovered that the liquid bubble substance inside the droplet would diminish with time. When the liquid bubble substance vanishes, so does the micro-explosion during burning.
When the relative humidity is 50 %, the 25 % by weight 2-Propanol solution will have micro-explosion. After lowering the relative humidity to 38 %, micro-explosion would not occur until the percentage of weight of 2-Propanol solution was raised to 45 %. Therefore, we can observe that adding 2-Propanol can lead to the increase of burning rate. The burning rate of between 25~30 % by weight 2-Propanol solution does not change significantly while it tends to decrease when the weight percentage comes to 40%. On the other hand, 25 % by weight ethanol solution would still experience micro-explosion after lowering the relative humidity from 50 % to 40 %.
In the experiment results, we found that when we deploy the droplet of biodiesel mixed with alcohol onto fiber, the non-uniform phenomenon similar to liquid bubble occurs. In this situation, whether under the condition of gravity or microgravity, micro-explosion is sure to occur while burning. And this non-uniform phenomenon is related to the relative humidity of the environment. Along with the rise of relative humidity, the liquid bubble gets bigger and bigger. Under the same relative humidity, liquid bubbles would become smaller when the carbon number of alcohol increases. Also, with the increase of alcohol concentration in percent by weight, the size of liquid bubbles become bigger. We also discovered that the liquid bubble substance inside the droplet would diminish with time. When the liquid bubble substance vanishes, so does the micro-explosion during burning.
When the relative humidity is 50 %, the 25 % by weight 2-Propanol solution will have micro-explosion. After lowering the relative humidity to 38 %, micro-explosion would not occur until the percentage of weight of 2-Propanol solution was raised to 45 %. Therefore, we can observe that adding 2-Propanol can lead to the increase of burning rate. The burning rate of between 25~30 % by weight 2-Propanol solution does not change significantly while it tends to decrease when the weight percentage comes to 40%. On the other hand, 25 % by weight ethanol solution would still experience micro-explosion after lowering the relative humidity from 50 % to 40 %.
In the experiment results, we found that when we deploy the droplet of biodiesel mixed with alcohol onto fiber, the non-uniform phenomenon similar to liquid bubble occurs. In this situation, whether under the condition of gravity or microgravity, micro-explosion is sure to occur while burning. And this non-uniform phenomenon is related to the relative humidity of the environment. Along with the rise of relative humidity, the liquid bubble gets bigger and bigger. Under the same relative humidity, liquid bubbles would become smaller when the carbon number of alcohol increases. Also, with the increase of alcohol concentration in percent by weight, the size of liquid bubbles become bigger. We also discovered that the liquid bubble substance inside the droplet would diminish with time. When the liquid bubble substance vanishes, so does the micro-explosion during burning.
When the relative humidity is 50 %, the 25 % by weight 2-Propanol solution will have micro-explosion. After lowering the relative humidity to 38 %, micro-explosion would not occur until the percentage of weight of 2-Propanol solution was raised to 45 %. Therefore, we can observe that adding 2-Propanol can lead to the increase of burning rate. The burning rate of between 25~30 % by weight 2-Propanol solution does not change significantly while it tends to decrease when the weight percentage comes to 40%. On the other hand, 25 % by weight ethanol solution would still experience micro-explosion after lowering the relative humidity from 50 % to 40 %.

並列關鍵字

microgravity ； free-falling body ； biodiesel ； alcohol ； micro-explosion soot

參考文獻

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