Quiet Please

Air Force Office of Scientific Research-sponsored scientists are exploring ways to prevent spinning acoustic waves from building up on the inside of jet engines and rocket motors and having destructive effect on these propulsion systems. A team, led by Dr. Ben Zinn, an aerospace engineering professor at the Georgia Institute of Technology, is studying the conditions under which these unstable sound waves occur and how to eliminate them. “If we find a means to prevent [the] phenomena from occurring, we can save the Air Force many millions of dollars,” said Zinn. With the help of Ukrainian scientist, Dr. Oleksandr Bibik, inroads have been made in reproducing the acoustic waves in a laboratory combustor and capturing them with very high speed cameras and fiberoptic probes so that the scientists can understand better the complex interactions between fluid mechanical, combustion, and acoustical processes within engines. Zinn thinks the waves can be prevented in rocket engines by symmetrically distributing the engine’s fuel and oxidizer injectors. A second means of mitigating them is by designing better damping devices, he said. (AFOSR report by Maria Callier)