MORGANTOWN, WV — Researchers at the U.S. Department of Energy’s National Energy Technology Laboratory (NETL) have been awarded a patent for an invention that detects lean blow-off in gas turbines. The new invention represents a step toward realizing low-emission, fuel-flexible gas turbines—a step that will promote air quality and U.S. energy security by allowing power plants to operate cleanly and efficiently on domestic fuels.
Many gas combustion systems, such as stationary gas turbines, operate on some form of lean premix combustion. In this method of combustion, fuel and air are mixed upstream of the combustion zone at low, or lean, fuel conditions. The temperature is kept low, which limits the formation of nitrous oxides (NOx)—pollutants which contribute to acid rain, ground-level ozone, and global warming.
While operating so near the flame’s extinction limit is desired to reduce NOx emissions, it greatly increases the risks of a incurring “lean blow-off,” in which the fuel-to-air ratio is so lean that the flame needed for combustion actually extinguishes. This can result in serious problems and is a major barrier against using coal-derived fuels in gas turbines.
This newly patented lean blow-off detection sensor from NETL researchers Jimmy Thornton, Douglas Straub, Benjamin Chorpening, and David Huckaby is the first monitoring and control system with a fast response time that requires minimal modifications to the turbine’s burner.
The sensor detects when lean blow-off conditions begin to develop. A sensor positioned near the flame imposes an electric field across the flame and uses the measured current through the flame to indicate lean blow-off conditions. Monitoring conditions in the combustion system allows lean blow-off to be prevented altogether.
The apparatus makes operations closer to the lean blow-off limit possible, and can be used to improve performance in state-of-the art gas turbines. Additionally, this new device may fill an important niche in the commercial market; currently, there are no commercial methods to sense incipient lean blowout.
NETL and the Energy Department’s Office of Fossil Energy work to resolve the environmental, supply, and reliability constraints of producing and using fossil fuels. The patented lean blow-off detection sensor helps meet the goals of developing revolutionary near-zero-emission turbine technologies and making the best use of America’s domestic energy resources.