ウォーターミストによる噴流拡散火炎の消炎  [in Japanese] Extinction of Jet Diffusion Flames by Water Mist  [in Japanese]

Access this Article

Search this Article

Author(s)

Abstract

本研究では,同軸流場に形成される噴流拡散火炎を対象に,ウォーターミストが火炎の安定や構造および消炎に及ぼす影響について調べた。ミスト発生器には,市販の超音波加湿器(トヨトミ-TUH-A9)を使用した。ミストの粒径特性をPDPAで測定した結果,ミストの粒径分布 D<sub>m</sub>≒1~44μm で,算術およびザウター平均粒径は,それぞれ D<sub>10</sub>≒15μm,D<sub>32</sub>≒21μm でほぼ一定である。実験に用いたリム厚0.5mmおよび5mm噴射管に形成される噴流拡散火炎の安定や構造に与えるウォーターミストの影響は異なることが観測された。0.5mm噴射管の付着火炎の消炎は,火炎基部に流入したミストの影響により,噴射管リムにおける火炎とミストとの相互作用に起因して火炎基部から不安定になる。これは対向流拡散火炎の熱的消炎に対応しており,プール火災の消炎機構も同様に説明できると考えられる。一方,5mm噴射管の乱流火炎の消炎は,遷移領域における乱れの増加と乱流火炎内に流入したミストとの相互作用で生じた火炎温度の低下に起因している。さらにウォーターミストの燃焼抑制効果についても明らかにした。<br>(オンラインのみ掲載)

In the present study, effect of water mist on the stabilizing and extinction mechanisms of a jet diffusion flames developing in a coaxial-flow burner was investigated experimentally, using propane as fuel. Water mists were generated by a commercial ultrasonic humidifier (Toyotomi-TUH-A9). The characteristics of water mist were measured by a PDPA. The mist sizes were found to have nearly normal distribution and ranged from 1 to 44 μm. The arithmetic and the Sauter mean diameters are D<sub>10</sub> ≒ 15 μm, D<sub>32</sub> ≒ 21 μm, respectively. When water mist was added into air flow, the flame stability limits and the distributions of flame temperatures, soot concentrations, flame brightness were measured. As a result, it was shown that the flame stability limits and flame temperatures are reduced as the water mist flow rates are increased because of the extinguishment due to evaporation which causes the cooling and depletion of oxygen in the flame zone. Likewise, soot concentrations and the flame brightness decrease with the increase of the mist flow rates. Furthermore, it was shown that extinction of the attached flame was caused by increase of the heat transfer from flame to mist. On the other hand, it was found that the local extinction of turbulent flame was spread with the increase of the water mist flow rates. Also it was confirmed that the structure of the turbulent diffusion flame varied with the mist flow rates which flowed into in a turbulent flame.

Journal

  • Bulletin of Japan Association for Fire Science and Engineering

    Bulletin of Japan Association for Fire Science and Engineering 61(1), 11-19, 2011-04-30

    Japan Association for Fire Science and Engineering

References:  30

Cited by:  1

Codes

  • NII Article ID (NAID)
    10028047799
  • NII NACSIS-CAT ID (NCID)
    AN0018688X
  • Text Lang
    JPN
  • Article Type
    Journal Article
  • ISSN
    05460794
  • NDL Article ID
    11106569
  • NDL Source Classification
    ZN1(科学技術--建設工学・建設業)
  • NDL Call No.
    Z16-105
  • Data Source
    CJP  CJPref  NDL  J-STAGE 
Page Top