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Experimental Investigation on combustion characteristics of DME lean side mixtures under micro-gravity

微重力下二甲醚贫侧混合气燃烧特性实验研究

基本信息

批准号：
16560196
负责人：
OKAJIMA Satoshi
金额：
$ 2.02万
依托单位：
Hosei University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2007
项目状态：
已结题

项目摘要

Experiments have been carried out to elucidate the fundamental combustion characteristics of DME fuel-air mixtures. The main results obtained for the study are as follows that, for the measurement of burning velocity on DME fuel-air mixtures using microgravity technique, □The micro-gravity technique is the most suitable method to extract the essential combustion characteristics of DME fuel-air mixtures, especially, near the very lean side of mixtures, The burning velocity of DME fuel-air mixtures monotonically decreases with decre4asing equivalence ratio and these values are nearly the same with those4 of methane-air mixtures at all the equivalence ratios studied, for instance the burning velocity is 44.2cm/s and 16.5cm/s, respectively, at equivalence of 1.1 and 0.65 under room temperature and atmospheric pressure and □The decrease of burning velocity of lean side of DME fuel-air mixtures is larger than that of rich side of mixtures, for the fundamental analysis an combustion behavior … More of DME laminar premixed burner flames, The burning velocity of DME premixed flames is approximately 34cm/s at 1.0 of equivalence ratio. As comparison of the burning velocity of DME with those of methane and propane-air mixture, the burning velocity of propane-air mixtures are larger than those of DME-air mixture and DME-air mixture are larger than methane-air mixtures. The blow off velocity and flashback velocity of DME are always larger than those of methane. □The stable region of the flame is easily to examine by the boundary velocity gradients(g). In case of circular tube laminar flow, the boundary velocity gradients can be expressed as g=4V/πR^3. Where V is the volume flow rate and R is the burner radius. Combustion of DME fuel-air mixtures is more stable than that of methane-air mixtures. In this study, we have tried to obtain the lower flammability limit using the burner method with the flame histories. The lower flammability limits of DME-air premixed flame obtained by this method are approximately Φ=0.34 and that of methane-air premixed flame are approximately Φ=0.55. From these data it may be predicted that the application to the engine combustion of DME is an effective alternative fuel for the future and, for measurement of quenching distance on combustion of DME fuel-air mixtures by flat flame propagation method, (1) Both of the quenching distance of DME fuel-air mixtures measuring by parallel plate and circular tube increase with decreasing equivalence ratio and these values are almost identical with the corresponding value for methane-air and propane-air mixtures. □The relationship between the quenching distance of parallel plate L_q, and circular tube d_q may be expressed by L_q=0.65・d_q. (3) The effect of buoyancy makes flame propagation speed increase and quenching distance decrease in upward flame propagation. (4) The quenching distance also depends on the ratio of surface area S to internal volume V of cylindrical long tube and the quenching distance becomes smaller as the S/V decreases.From these experimental data it may be predicted that the application to the engine combustion of DME fuel is not impossible. Less

已经进行了实验来阐明 DME 燃油-空气混合物的基本燃烧特性。研究取得的主要结果如下：对于利用微重力技术测量DME油气混合物的燃烧速度，□微重力技术是提取DME油气混合物基本燃烧特征的最合适的方法，特别是在混合物的极稀侧附近，DME油气混合物的燃烧速度随着当量比减小时，这些值与所研究的所有当量比下的甲烷-空气混合物的值几乎相同，例如，在室温和大气压下，当量为1.1和0.65时，燃烧速度分别为44.2cm/s和16.5cm/s，且□DME燃料-空气混合物稀侧燃烧速度的降低大于浓侧混合物侧面，对 DME 层流预混燃烧器火焰的燃烧行为进行基本分析，当量比为 1.0 时，DME 预混火焰的燃烧速度约为 34cm/s。将DME与甲烷、丙烷-空气混合物的燃烧速度进行比较，丙烷-空气混合物的燃烧速度大于DME-空气混合物的燃烧速度，DME-空气混合物的燃烧速度大于甲烷-空气混合物的燃烧速度。二甲醚的吹扫速度和闪回速度始终大于甲烷。 □火焰的稳定区域很容易通过边界速度梯度（g）来检查。对于圆管层流，边界速度梯度可表示为g=4V/πR^3。其中 V 是体积流量，R 是燃烧器半径。 DME 燃料-空气混合物的燃烧比甲烷-空气混合物的燃烧更稳定。在本研究中，我们尝试使用燃烧器方法和火焰历史来获得可燃下限。该方法得到的二甲醚-空气预混火焰的可燃下限约为Φ=0.34，甲烷-空气预混火焰的可燃下限约为Φ=0.55。从这些数据可以预测，二甲醚在发动机燃烧中的应用是未来有效的替代燃料，对于用平面火焰传播法测量二甲醚油气混合物燃烧的熄火距离，(1)平行板和圆管测量的二甲醚油气混合物的熄火距离均随着当量比的减小而增加，这些值与甲烷-空气和丙烷-空气混合物。 □平行板的淬火距离L_q和圆管d_q之间的关系可以表示为L_q=0.65·d_q。 (3)浮力的作用使得火焰向上传播时火焰传播速度增大，熄灭距离减小。 (4) 熄火距离还取决于圆柱形长管的表面积S与内容积V之比，并且随着S/V减小，熄火距离变小。从这些实验数据可以预见，DME燃料应用于发动机燃烧并非不可能。较少的