The Flame in Space vs Earth's Flame
On the shore of Lake Erie there is an amazing place called "a gateway to space." It is a tower height of 30 meters, where it is possible to recreate the conditions of microgravity, in other words- weightlessness. Many experiments, which then were conducted in space, were pre-tested in this tower. One of those experiments is flame burning.
The ignition of match in microgravity. image source
The flame accompanies mankind throughout its history. It provides us with energy that allows civilizations to move forward. And like any physics-chemical process it behave absolutely differently in conditions of weightlessness.
The influence of convection.
The process of burning on the Earth is subject to the forces of gravity of the planet. Due to the attraction of the Earth there is an effect of convection: the heated air becomes lighter and goes up, the cold air occupies the released place and repeats the cycle. That's why the flame of a candle or match has an elongated shape.
image source
In microgravity the effects of convection disappears and the flame acquires a spherical shape. In the absence of movement of the ascending air the flame propagates uniformly around the source of combustion. Because of this burning of fuel is more complete than on the Earth.
Burning a drop of heptane in microgravity. image source
By the way, it is convection bends the match, if you hold it vertically. The air moves from the bottom upwards bending the wood+ since the flame on top is hotter than the bottom, the upper part of the match loses more mass and volume (burn stronger). Therefore, the tip becomes lighter and bends more noticeable than the base.
image source
Temperature and visibility.
More importantly, changing not only flame shape, but its physical parameters. On the Earth, the flow of air creates a high temperature gradient along the flame. A constant flow of fresh oxygen affects the highest temperature possible and at the same time the color of fire.
image source
For example, our usual yellow-orange color of the flame is the glowing particles of soot, which is formed only at temperatures above + 1000 °С.
The high temperature allows the atoms to "jump" on some time into higher energy states. When returning to the initial state, the atoms begin to emit light of a certain frequency, this frequency depends on the electronic structure of an element.
That's why different substances have a different color when burning, their atoms have different electronic structure. image source
The flame in weightlessness is “colder”, its temperature ranges from +227-527°C. We can see the orange color of the fire (higher temperature) only at the initial stage of ignition, when oxygen is still enough.
In the cold phase, the flame literally becomes invisible to the human eye (the emitted light is in the ultraviolet and infrared). But the burning process continues. If you add new oxygen, the fire will return to the active phase.
Such experiments are very important. A detailed understanding of the combustion process and its dependence on other physical phenomena (such as convection), will allow us to more efficiently utilize and consume hydrocarbon fuel. At the same time, it is much easier to protect yourself from what you know good. And, in any case, it is very beautiful…
sources: Convection, Flame Extinguishment Experiment (FLEX), The NASA Glenn Research Center, Metal Ion Flame Test Colours Chart, What is the fire?, images from Google Search.
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wow great post, i never heard of the term microgravity , so i am looking it up
Thank you! Well, it's most like zero-gravity, too close to it, but not quite :)
ya there is a lot of information about this, trying to simulate it is interesting, and there a bunch of posts about scientist creating their own gravitational field.....hmmmm
Maybe you will be interesting to read this: Microgravity Facilities and how they create this effect with tower :here
wow thanks for the link i will check it out
Brilliant post natord, and the video was awesome!
Following you now for more excellent content :D
Upvoted and resteemed.
Thank you, my new friend!
I'm your follower now too :)