Pratt & Whitney has teamed with scientists at Virginia Tech University to develop a tool for measuring thrust and emissions from gas turbine engines using lasers. The new technique, known as “filtered Rayleigh scattering for thrust measurement” (FRST), enables high-fidelity measurements of key parameters such as velocity, temperature, and density.
According to Raytheon subsidiary Pratt & Whitney, the FRST technique offers several advantages over traditional sensors and probes, which can cause blockages in airflow and are often difficult to install, especially on smaller engine cores with limited space.
“The ability to use lasers and optical sensors represents a major step forward in engine instrumentation technology,” said Geoff Hunt, Pratt & Whitney senior v-p of engineering and technology. “FRST provides a less intrusive and more cost-effective method for measuring a range of engine metrics.”
FRST relies on a basic physics principle called Rayleigh scattering, which refers to the way light interacts with particles in the atmosphere. This phenomenon explains why the sky appears blue.
“Though the principle of Rayleigh scattering has been known for centuries, Pratt & Whitney and Virginia Tech engineers have harnessed recent advancements in computing power and laser and camera technology to demonstrate the first successful application on a turbofan engine,” said Todd Lowe, an aerospace engineer and professor at Virginia Tech.
To apply that principle to the measurement of thrust, the researchers illuminated the gas flow field of a turbine engine with a laser beam of ultraviolet light to observe how the light interacts with the flow of particles. Researchers measure the results using a high-performance camera.
Pratt & Whitney and Virginia Tech have already tested their patent-pending FRST technology using a research engine on a test stand at the university, and the team is now working toward a flight-test campaign. The researchers say FRST could facilitate the development of more efficient engines that produce fewer emissions. It could also enable precise measurement of non-CO2 particulate emissions, which are responsible for creating contrails that contribute to climate change.