May/June 2012
Automation Update

Patented "noise sponge" quiets combustion

According to Science Daily, a sponge-like material employed by a University of Alabama engineering professor can significantly quiet combustion, possibly making work environments safer and extending the life of equipment.

Dr. Ajay K. Agrawal, the Robert F. Barfield Endowed Chair and professor of mechanical engineering, was granted a patent for the breakthrough technology for noise reduction in combustion. This technology decreases the noise generated by combustion systems at the source by placing a sponge-like material directly in the flame. This patent is based on Agrawal's work on jet engine combustion with Ultramet Corp., funded by the U.S. Navy.

The challenge of cutting the sound level during the combustion process is that combustion happens at extremely high temperatures and pressure. Agrawal found a porous material-a composite material made of hafnium carbide and silicon carbide-that can tolerate the conditions of jet engine combustion. It can withstand intense levels of heat and pressure. The material is placed directly into the flame and acts like a sponge for the noise. Due to its high permeability, the foam allows gases to easily flow so combustion is not interrupted, yet is much quieter. The foam surrounds the flame, cuts the noise and eliminates the potential for engine instability.

The application of the technology extends beyond jet engines. Some chemical manufacturers place loud, high-capacity torches at ground level instead of safer heights to control noise. Factories that rely on combustion also face government regulations to protect employees from noise.