加熱された物体を煙の中に置くと,その物体の周圍に煙粒子を含まない空氣の薄い層(無煙帶)が出來る.此の實驗では,垂直に張つた白金リボンを電流で熱し,リボンの面に接して生ずる無煙帶を冩眞にとり,ミクロフォトメーターで煙の分布の有樣を調べた.熱に對して安定な數種の煙に就いては,次の實驗式を得た.B=Cθ^a/pこゝに,Bは無煙帶の厚さ,θはリボンと周圍の空氣との温度差,pは空氣の壓力,Cとaとは煙の種類には無關係な定數である.加熱されたリボンの周圍に生ずる對流は,空氣の粘性の爲めに特殊な速度匂配を持つ.その爲に,煙粒子はマグヌス効果に依る力を受け,リボンから遠ざかる.之が無煙帶の生成に與る主要な原因の一つと思はれる.高温で氣化し易い煙の中では,同じ事情の下で,安定な煙の中よりも遙かに大きな無煙帶が出來る.之には煙粒子の蒸發が主なる役目をして居るらしい.無煙帶の厚さは熱輻射,電場,磁場の影響を受けて變化する事はない.

When a hot body is placed in smoky air, a thin smokeless zone is observed around it. In the present experiment, the smokeless zone in front of a platinum ribbon, which is suspended vertically and heated by electric current, was photographed and examined by means of a microphotometer. Different kinds of smokes, stable at high temperature, give the same breadth of the zone. The following empirical formula was obtained. B=Cθ^a/p, where B denotes the breadth of the smokeless zone, θ the temperature difference between the ribbon and the ambient air, p the gas pressure, C and a the constants. The smoke particles in the convection current around the heated ribbon are carried away from it by the force due to Magnus effect. This effect seems to be one of the principal causes on the formation of the smokeless zone. Smokes, volatile at high temperature, give larger breadth of the zone than that of the stable smokes under the same condition. This is probably due to the evaporation of the smoke particles. The smokeless zone is not affected by the radiations from a hot body, and also not by an applied electric or magnetic field.

資料番号: SA4146439000