KAUST researchers from Saudi Arabia have devised a new strategy to make gas turbines more safer and efficient.
The process involves understanding gas flames’ response to acoustic perturbations within the turbines at high pressure.
According to the researchers, soldiers marching lockstep across a bridge can cause the structure to collapse if the rhythm of their step matches the bridge’s natural vibration frequency.
The same applies to a gas turbine which can be damaged, or even explode, if heat and pressure fluctuations produced by the flame complement the acoustics of the combustion chamber.
On a day-to-day basis, this thermoacoustic instability hampers efficient combustion, increasing noise and pollution emissions.
Deanna Lacoste from KAUST’s Clean Combustion Research Center and her colleagues have now found a way to measure the stability of gas flames at elevated pressure.
As part of their study, the researchers made use of a parameter called flame transfer function (FTF) to investigate the flame’s response to acoustic forcing
The FTF is derived from experimental measurements of the flame’s response to sound waves. But these experiments are usually run at atmospheric pressure, whereas real gas turbines reach pressures of up to 30 bar.
Lacoste, Ph.D. student Di Sabatino, and their colleagues systematically investigated the effect of pressure on methane and propane gas flames.
“Our experiments show the FTF at atmospheric pressure is different to the FTF at elevated pressure,” says Di Sabatino.
According to Lacoste’s team, pressure had a particularly strong effect when the loudspeaker produced acoustic perturbations of 176 Hz for both methane and propane gas flames.
The new data will assist with the design of new gas turbines, says Di Sabatino:
“It will be useful for engineers to have FTFs at pressures closer to the operating pressure of gas turbines. One of the next steps of our research is to build a new experimental setup to reach up to 20 bar, closer to the pressures in real gas turbines.”
Image and content: Rolls-Royce/King Abdullah University of Science and Technology (KAUST)