Simple Combustor Increases Efficiency, Reduces Emissions

Georgia Tech researchers have created a simple combustor (combustion chamber where fuel is burned to power an engine or gas turbine) designed to burn fuel in a wide range of devices ― with next to no emission of nitrogen oxide (NOx) and carbon monoxide (CO), two of the primary causes of air pollution. The device has a simpler design than existing state-of-the-art combustors and could be manufactured and maintained at a much lower cost, making it more affordable in everything from jet engines and power plants to home water heaters.

Called the Stagnation Point Reverse Flow Combustor, the Georgia Tech device, originally developed for NASA, significantly reduces NOx and CO emissions in a variety of aircraft engines and gas turbines that burn gaseous or liquid fuels. It burns fuel with NOx emissions below 1 parts per million (ppm) and CO emissions lower than 10 ppm, significantly lower than emissions produced by other combustors.

A comparison of Georgia Tech’s combustor with a traditional combustor: (L) A traditional combustor mixes fuel and air before they are injected into the combustion chamber. (R) Tech’s combustor injects the fuel and air separately into the combustor.

The design can be adapted for use in a variety of applications, including something as large as a power generating gas turbine or as small as a water heater in a home.

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 NOx and CO and avoids acoustic instabilities that are problematic in current low emissions combustors.

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

But 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.

The project was funded by the NASA University Research Engineering Technology Institute (URETI) Center on Aeropropulsion and Power and Georgia Tech.

Resource: Simple design makes ultra-low emission combustion more efficient, affordable and stable, Georgia Institute of Technology News Room, June 21, 2006

Comments

[Gary Ginter]

Looks to me like a clever application of combustion gas recirculation within a GT. Congratulations on a significant technical achievement! Here are my questions:

1. Are you using only CH4 or propane, not liquid HCs, when you achieve the 1 ppm NOx and sub-10 ppm CO?
2. I would think that a Stagnation Point reversal system is not easily applied to high mass-flow rate GTs such as jet engines. How do you avoid the hit to efficiency that such a reversal of flow would entail? How do you gain the acceleration to near mach one at the turbine throat entrance?

[Engine Additive]

really enjoy to read this awesome blog post. Inspiring!