Hydrogen and air mixtures, within the flammable range, can explode and may burn with a pale blue, almost invisible flame.

在可燃范围内的氢和空气的混合物可能爆炸，也可能燃烧，火焰是淡蓝色，几乎看不见。

youdao

The Olympic Flame will burn from a curved triangular aluminium tube which has a lace-like mesh complete with 8, 000 holes - one to represent each torchbearer .

2012年伦敦奥运圣火将在火炬内的三面锥体铝管内点燃，外层为花边网状结构，表面有八千个圆圈，代表八千名火炬手。

youdao

With the characteristics of long-flame and high temperature, down-fired boilers are used burn coals with low volatiles such as anthracite.

型火焰锅炉以其自身的炉膛温度高、火焰行程长等特点，适于燃烧无烟煤等低挥发分燃料。

youdao