Clean fire, pristine heat

A development in combustion and combustion chambers may save process industries and other heat-hungry users fuel, money, and pollution credits.

Georgia Tech researchers say their new combustor will burn fuel in a wide range of devices with next to no emission of the pollutants nitrogen oxide (NO^sub x^) and carbon monoxide (CO).

The combustor, a combustion chamber where fuel burns to power an engine or gas turbine, has a simpler design than existing state-of-the-art combustors. The Georgia Tech team said it could manufacture and maintain the device at a much lower cost, making it more affordable in everything from jet engines and power plants to home water heaters.

Attaining ultra low emissions is a priority for combustion researchers as federal and state restrictions on pollution continuously reduce the allowable levels of NO^sub x^ and CO produced by engines, power plants, and industrial processes.

Called the Stagnation Point Reverse Flow Combustor, the Georgia Tech device, originally developed for NASA, significantly reduces NO^sub x^ and CO emissions in a variety of aircraft engines and gas turbines that burn gaseous or liquid fuels. It burns fuel with NO^sub x^ emissions below 1 part per million (ppm) and CO emissions lower than 10 ppm, significantly lower than emissions produced by other combustors. A traditional combustor mixes fuel and air before they enter the combustion chamber. Georgia Tech's combustor injects the fuel and air separately into the combustor.

The combustor burns fuel in low temperature reactions that occur over a large portion of the combustor. By eliminating all high temperature pockets through better control of the flow of the reactants and combustion products within the combustor, the device produces far lower levels of NO^sub x^ and CO and avoids acoustic instabilities problematic in current low emissions combustors.

To reduce emissions in existing combustors, fuel premixes with a large amount of swirling airflow prior to injection into the combustor. This requires complex and expensive designs, and the combustion process often excites instabilities that damage the system.

However, Georgia Tech's design eliminates the complexity associated with premixing the fuel and air by injecting the fuel and air separately into the combustor while its shape forces them to mix with one another and with combustion products before ignition occurs.