日本火災学会論文集
Online ISSN : 1883-5600
Print ISSN : 0546-0794
ISSN-L : 0546-0794
33 巻, 1 号
選択された号の論文の3件中1~3を表示しています
論文
  • 長田 正義
    1983 年 33 巻 1 号 p. 1-7
    発行日: 1983年
    公開日: 2012/08/31
    ジャーナル フリー
    Polyvinyl chloride covered cords which have many excellent advantages in electrical and mechanical natures, are widely used for lead wires connecting the electrical apparatus. However, when a part of element wires of polyvinyl chloride covered cords are cut by any repeated force, such as bend and twist ones, even if rated current applied to the polyvinyl chloride covered cords having disconnected element wires (PCC), it results in an over current for the residual element wires. As a result, firing phenomena of PCC are possible by an abnormal generated heat caused by the over current in the element wires under the normal operating condition.
    In order to investigate the firing phenomena of PCC under the normal operation, experimental and theoretical studies on the firing current and energy input of PCC have been carried out using a model PCC which is especially devised in consideration of the hardest working condition, and is composed of only an element wire of certain lengths between both ends.
    The results obtained for the firing phenomena of PCC according to the over current are shown as follows:
    (1) Firing current and time ranges of the model PCC are from about 60 to 1,000 sec. for applied current from about 10 to 30 A.
    (2) Firing process of PCC have next two ones; first, the temperature rise up to about 100°C takes place owing to the abnormal generated heat caused by the over current in the element wire, thereafter, instantaneously generated one produced by the element wire explosion forced the polyvinyl chloride covering to about 550°C, then it comes to fire.
    (3) Firing heats of PCC are ranged from about 50 to 800% of the contained one in the polyvinyl chloride covering at firing temperature.
  • 長谷見 雄二, 徳永 太造
    1983 年 33 巻 1 号 p. 9-17
    発行日: 1983年
    公開日: 2012/08/31
    ジャーナル フリー
    A mathematical model to predict deterministic properties of turbulent diffusion flames is derived based on similarity analysis. In order to determine a few parameters appearing in the model, measurements of temperature, velocity, irradiance and flame geometry were made on the turbulent diffusion flames from a porous refractory burner of the diameter of 0.30m with propane as fuel. Excess temperature and velocity along the centerline of flame and flame height are formulated as functions of the properties of air and fuel, physical constants and the parameters governing the flame structure; θa = 1.77kqfcr/mCp, wa = 1.76√gβkqfcrz/mCp and Lf = 0.00154 (mQ/Dπρqfcr)2, where Q is the heat input, Cp is specific heat of air, qf is combustion heat of fuel and cr is the mass fuel to air ratio. Ratio of heat dissipation due to convection to heat input, k air excess ratio, m and the parameter characterizing the turbulence D are estimated experimentally as k≈0.65, m≈3.96 and D≈0.000069Q4/5 respectively. Characteristics of turbulent diffusion flames as radiation heat source is also studied on the basis of the above model, and it was derived that the heat dissipation due to radiation is proportional to Qn, where n takes 0.8-1.2 depending on the composition of carbon in the fuel.
  • 武田 久弘
    1983 年 33 巻 1 号 p. 19-23
    発行日: 1983年
    公開日: 2012/08/31
    ジャーナル フリー
    The behavior of the pre-flashover period in compartment fire was investigated experimentally using the small scale compartment. In the PMMA compartment fires, the flame spread depended only on the ventilation opening height and did not depend on its width. The flame spread rate was fairly high in compared with the free burning condition (without compartment). After the whole PMMA surface was covered by a flame, an oscillatory phenomenon appeared. This oscillatory phenomenon was modelled qualitatively in terms of the competitive relationship between fuel gas release rate and fresh air supply rate by ventilation. Also the scale effect of fire behavior in the early stages of the methanol compartment fires was explained using this model.
feedback
Top