We deal with it every day, or almost: ithas been used by humans for over 400,000 years. But in space, everything is different, and so is its behavior. This is what researchers from who created the project , Where Acme, spread over four and a half years. Thus, since 2017 on board experiment around this theme.
“An environment ofallows scientists to explore the behavior of the flames without affecting so they can study underlying structure and behavior of flamessaid Dennis Stocker, Acme project researcher at Nasa. This knowledge can help designers and engineers here on Earth develop furnaces, power plants, boilers and more more efficient, less polluting and safer. »
In the micro-gravity force, the flames are spherical!
On the program are six experiments that cover different themes, but with one thing in common: they generateor not premixed, i.e. when and necessary in addition to a source of in order for the fire to form, separate before ignition. This is the case, for example, for candles, where the fuel is wax, the oxidizing agent surrounding, and the activation energy the flame from a lighter or a . “More than 1,500 flames were lit, more than three times as many as originally plannedsaid Dennis Stocker. More “first” have also been manufactured, perhaps especially in areas with cold and spherical flames. »
Already created in 2012 with combustible material, this time the flames were made only with gaseous fuels. But the main result is the same: the flame assumes a spherical shape, very different from the one we usually know. In the question, the absence of gravity: on the ground, by because it is less dense and the cold air falls down by gravity and nourishes the bottom of the flame. But these phenomena do not come into play on board the ISS. The combustion products no longer fall by gravity and then remain around the flame: oxygen is supplied from all sides, provided enough air for CO2 let him pass. In this case, the flame is maintained.
Six experiments to understand the dynamics of fire in microgravity
All in all, these six experiments, which are impossible to perform in a terrestrial laboratory, have improved the computer models that simulate growth andflames in a microgravity environment. A fire created in the room will be more stable and therefore harder to put out. It is for this purpose that NASA performed these tests: , and better understand the dynamics of fire in microgravity. Especially in spacecraft, where everything is trapped, and where an uncontrolled fire quickly becomes catastrophic.
Among these tests, cold flames were performed, an experiment that had already been performed in 2012 aboard the ISS. But also it burningSimulator (BRE) consisted of igniting different materials in one at rest, then to observe the ignition and to perform various extinguishing tests. Several fuels have been used, in different atmospheres, in conditions similar to those envisaged for future space exploration ”.
During the s-Flame experiment, the fuel and the surrounding atmosphere were diluted with helium, which replaced the nitrogen. As it is a better heat conductor than nitrogen, the size of the flame has increased markedly, but also its structure and its dynamics. Analyzes are underway to model it, thus predicting effective extinguishing methods. © Nasa
The case of the sooty flames
Other experiences such as Coflow Laminar Diffusion Flame (CLD Flame), made it possible to studyi.e. which generates this polluting blackish-looking substance resulting from incomplete combustion of carbonated. They found that ” Microgravity soot flames are wider and higher than their normal gravitational counterparts, and the concentration of soot can be as much as a factor of ten greater.
But that’s not all! NASA explains that if the fuel is diluted by oneinert, like then the soot and flame disappear “may detach from the surface of and appears as a small blue”. In case of extreme dilution, the flame even assumes the shape of a disc and then goes out. Finally, researchers have shown that one makes it possible to reduce the emissions of diffusion flames: this thanks to created as a result of combustion reactions that are sensitive to it. Depending on the field used, the shape of the flame can be changed until the formation of soot is eliminated.