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Fundamental Study of Wood Ignition Medchanism under High Voltage and Large Current Discharge Condition for Development of Control Method of Forest Fire

高电压大电流放电条件下木材点火机理的基础研究为森林火灾防治方法的发展

基本信息

批准号：
13309001
负责人：
HAYASAKA Hiroshi
金额：
$ 18.05万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13309001/
关键词：
Forest Fire Lightning Ignition Mechanism High Voltage Discharge Smoldering Shock Wave Boreal Forest Global Warming 泥炭環境破壊

项目摘要

It is well known that lightning does ignite forests, although we do not know details of how lightning ignites forests, what parts of a forest act as the starter of forest fires. We also do not know the growth processes from small to large flames in a forest fire, or how lightning produces the energy for ignition.Field research in Alaska was carried out to establish the existence lightning scars in forests there, and to elucidate the characteristics of lightning-caused fires Results of the field research in Alaska may be summarized as follows :1.Ignition probabilities are not small in boreal forests near Fairbanks, Alaska. They are around 15 % that suggests that there are flammable materials or fuels available in the boreal forest.2.Fuel in this boreal forests includes twigs wish needles of black spruce, moss which covers the ground at a thickness of about 10cm, and lichen on branches and forest floor. The trunks of trees and thick branches do not burn under usual forest fire conditions.3.Gravimetry of distribution measurements of these fuels shows that the maximum (ideal) heat generated by boreal forest fires in Alaska would be 72.4MJ/m^2. This becomes 11.3MJ/m^3 per meter of tree, when an average height of 6.4m is assumed.The voltage generators (1Gs) were used to carry out impulse voltage tests. The 1.2MV 1G of Kansai Tech was mainly used to carry out basic experiments to evaluate the damage to trees due to discharges, representing lightning, and the conditions causing fire ignition. The 12MV 1G of CRIEPI was used to verify whether standard lightning-impulse currents cause ignition in dry grass. Two explosive phenomena taken by a video camera will be explained by using theoretical results obtained by Uman and Voshall (1968). Finally, a forest ignition mechanism by lightning based on the field research and experimental results, and theoretical consideration was obtained.

众所周知，闪电会点燃森林，尽管我们不知道闪电如何点燃森林的细节，也不知道森林的哪些部分会引发森林火灾。我们也不知道森林大火从小火焰到大火焰的生长过程，也不知道闪电是如何产生点火能量的。为了确定阿拉斯加森林中是否存在雷击伤痕，阐明雷击火灾的特征，在阿拉斯加进行了实地调查。在阿拉斯加费尔班克斯附近的北方森林，着火的可能性也不小。它们在15%左右，这表明在北方森林中有可燃材料或燃料。这片北方森林的燃料包括黑云杉的细枝和针叶，覆盖地面约10厘米厚的苔藓，以及树枝和森林地面上的地衣。树干和粗树枝在通常的森林火灾条件下不会燃烧。对这些燃料的分布测量的重量法表明，阿拉斯加北方森林火灾产生的最大（理想）热量为72.4MJ/m^2。假设树的平均高度为6.4米，这就变成了每米树11.3MJ/m^3。使用电压发生器（1Gs）进行冲击电压试验。关西科技的1.2MV 1G主要用于进行基础实验，以评估放电对树木的损害，代表闪电，以及引起火灾的条件。CRIEPI的12MV 1G用于验证标准雷击脉冲电流是否会在干草中引起点火。用摄像机拍摄到的两种爆炸现象将用human和Voshall（1968）的理论结果来解释。最后，在野外研究和实验结果的基础上，得出了森林雷电引燃机理，并进行了理论思考。