Scientists create flames that don’t flicker

By Mark Waghorn via SWNS

Manned missions to Mars could be made safer after scientists made flames that don't flicker.

Fire in zero gravity is less predictable - and potentially more lethal.

Now a US team has made the mixture of hot gases more stable using a revolutionary technique.

It opens the door to better machines - ranging from household cookers to passenger jets and even spacecraft.

Lead author Dr. Xiaoyu Ju, of California University in Berkeley, said: "It provides a feasible way to suppress flame flickering without changing the fuel mass burning rate - thus promoting steady-state combustion."

Creating them usually requires artificially low gravity or pressure.

Instead, Ju and colleagues managed to do it in real-world conditions - by pairing flames together.

Devices ranging from stoves and furnaces to airplanes and rockets use tightly arranged flames.

When they are close together they flicker even more - making them less efficient and more damaging to the environment.

Lab experiments showed the phenomenon can be prevented by continuously changing the distance between them under standard conditions.

Here on Earth, when a flame burns, it heats the surrounding atmosphere, causing the air to expand and become less dense.

The pull of gravity draws colder, denser air down to the base of the flame, displacing the hot air, which rises.

This convection process feeds fresh oxygen to the fire, which burns until it runs out of fuel.

The upward flow of air is what gives a flame its teardrop shape and causes it to flicker.

But odd things happen in space, where gravity loses its grip on solids, liquids and gases.

Without gravity, hot air expands but doesn't move upward. The flame persists because of the diffusion of oxygen, with random molecules drifting into the fire.

Fires in microgravity are dome-shaped or spherical and sluggish - thanks to meagre oxygen flow.

They look alien. If you ignite a piece of paper, the fire will just slowly creep along from one end to the other.

By using two identical methane gas burners, the researchers showed once one flame was put into motion, flickering could be stopped.

The left-most couldn’t move, while the other was fixed to an oscillating platform, reports New Scientist.

From previous studies they knew there was a critical distance between the flames where both would momentarily
stop flickering.

But when the flame on the right was programmed to keep moving so it was always "just slightly off" high speed camera recordings showed it happened for much longer.

Ju said: "Instead of influencing each other, the flames would get stuck in a coupled but not yet coupled state."

The findings in Physical Review Applied could be used as a starting point for investigating how gas-turbine engines in aircraft could be made even more reliable.

Dr. Peng Zhang, of the City University of Hong Kong who was not involved in the study, said: "Unstable combustion not only makes an engine inefficient, but also may put it at risk of failure."

NASA is in a race with China for the first crewed trip to the Red Planet. It could happen within a decade.