The discovery of a new type of cool-burning flames could lead to cleaner, more efficient car engines.
In experiments, conducted by a team of international researchers on the International Space Station (ISS), droplets of heptane fuel were ignited in a wide range of environments, including air similar to the earth’s atmosphere as well as atmospheres diluted with nitrogen, carbon dioxide and helium.
The team, at first, believed the flames had extinguished themselves but sensors showed that the heptane was, in fact, still burning.
Forman Williams, a professor of mechanical and aerospace engineering at the University of California, San Diego, commented: “We observed something that we didn’t think could exist.”
The discovery could lead to the development of homogenous-charge compression ignition which could, for example, help improve internal combustion engines in cars. It could also lead to engines burning fuel at cooler temperatures, thus emitting fewer pollutants, while still being efficient.
The experiments are run by remote control from NASA’s John Glenn Research Center in Cleveland and the results are then analysed by a team of scientists from NASA, US San Diego, Princeton, Cornell and other universities.
The experiments occurred in the Multiuser Droplet Combustion Apparatus, which is found within the ISS’s Combustion Integrated Rack, an experimental facility about the size of a 5.5 foot bookcase and around 560 lbs in weight. Here, data is recorded and transmitted to the ground.
In the microgravity environment of the Multiuser Droplet Combustion Apparatus, droplets are generated and ignited from different fuels in varying atmospheric conditions.
It is because of this environment that researchers are allowed sufficient test time for cool flames to occur. The research will not work in other environments. “Things can happen out there that can’t happen here [on earth],” Williams said.
The researchers believe that the cool flames are a result of elementary chemical reactions which can only occur in the microgravity environment on the ISS, where there is no buoyancy, allowing gases enough time around the droplets for the chemistry to develop.
This chemical reaction is not possible on earth since burning fuel droplets, limited by buoyancy, only exist for a very short period of time.
For the cool flame combustion to occur on earth, future applications will need the right mix of fuels. Thus, NASA is planning a new series of experiments to look into this challenge, which is said to start next winter and continue for about a year.
Images courtesy of Nasa