小型プール火災の非定常燃焼時の燃焼速度 Unsteady Burning Rates of Small Pool Fires

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燃料に,ヘプタン,メタノール及び灯油を使い,タンク内の燃料液面高さが時間と共に変化するような,小型プール火災の実験を行い,燃焼速度,燃料温度などを測定した。この結果,燃料温度の変化傾向より,小型プール火災の非定常燃焼では,予熱,遷移,沸騰と呼べる過程の存在すること,ヘプタンと灯油の燃焼速度は,燃料とタンクの温度上昇と共に増加することがわかった。準定常となる予熱と沸騰の各過程の燃焼速度を比較すると,ヘプタンで,約1.6倍,灯油で,約1.3倍の増加が観測されたが,メタノールの場合,他の燃料と同様に,燃料とタンクの温度上昇があるにもかかわらず,明確な燃焼温度の増加は観測されなかった。これらの燃焼速度の変化を燃料の蒸発熱で明らかにした。<br>(オンラインのみ掲載)

In this paper, burning rates measured during unsteady combustion of small pool fires using three different fuels are discussed. Unsteady combustion is obtained by a batch test in which the fuel level in the tank decreases after ignition. We measured the burning rates, the fuel temperature, and the tank temperature of three different fuels. Experimental results allow the following conclusions: <br>1. Three major processes, so called preheating, transition and boiling process, were found from the fuel temperature change curves of small pool fires during unsteady combustion. <br>2. Burning rates of heptane and kerosene increase when fuel temperatures and tank temperatures go up. The burning rates in the boiling process are about 1.64 for heptane and about 1.3 for kerosene times as much as those during the preheating process. <br>3. Preheating, transition and boiling processes were easily found from the fuel temperature change curves of the methanol pool fire. Nevertheless methanol does not show a distinct increase of burning rate. <br>4. The reason for various burning rate changes of small pool fires are clearly explained by the calculation of fuel evaporation using measured burning rates and fuel temperatures. Heptane and kerosene fires change their burning rates because both evaporation heats and preheating heat are not large. The evaporation heat of methanol is the largest and it is about three or five times bigger than that of heptane and kerosene. This is one of the reasons for the constant burning rate of methanol. <br>5. From the above discussion, the concept of maximum burning rate ratio (MBRR) is introduced to explain the burning rate change of various fuels. MBRR becomes larger as the number of carbon atoms in fuel increases. <br>Finally, the above mentioned phenomena will happen when heat supply by convection and conduction are not so small compared with by radiation. In medium and large size pool fires, sufficient heat will be supplied from the flame, mainly by radiation, so that the above mentioned preheating and transition processes may not easily be found. In small pool fires, burning rates are strongly affected by circumferential conditions such as fuel and tank temperatures. This may be one reason for various burning rates obtained by experiments using the same tank size and fuel.

収録刊行物

  • 日本火災学会論文集

    日本火災学会論文集 45(1), 19-25, 1996-07-30

    日本火災学会

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各種コード

  • NII論文ID(NAID)
    10002685936
  • NII書誌ID(NCID)
    AN0018688X
  • 本文言語コード
    JPN
  • 資料種別
    ART
  • ISSN
    05460794
  • NDL 記事登録ID
    4056243
  • NDL 雑誌分類
    ZN1(科学技術--建設工学・建設業)
  • NDL 請求記号
    Z16-105
  • データ提供元
    CJP書誌  CJP引用  NDL  J-STAGE 
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