New technology: High fidelity measurement of key parameters of turbine engines using lasers

On June 19, Pratt&Whitney and Virginia Tech announced that they had successfully demonstrated a groundbreaking new technology, which can use laser to calculate thrust, so as to achieve high-precision and high fidelity measurement of key parameters (including speed, temperature and density) of Gas turbine.

It is reported that this new Optical instrument technology is called "filtered Rayleigh scattering thrust measurement" (FRST), which can project a "slice" of laser through the entire plane area of the inlet and exhaust. Compared with traditional sensors and probes, it has significant advantages - it can support the development of more efficient engine core technologies, and due to its high fidelity measurement ability, it can also detect non carbon dioxide particulate emissions in flight.

Recently, the research team has successfully demonstrated this filtered Rayleigh scattering thrust measurement (FRST) technology on the test engine of the Pratt Whitney Center of Excellence at Virginia Tech, which is expected to help researchers obtain richer and higher quality data.

Geoff Hunt, senior vice president of engineering and technology of Pratt&Whitney, said: The ability to use lasers and optical sensors represents an important step forward in engine instrumentation technology, and is also proof of the long-term collaboration of the Virginia Tech Center for Inclusive Excellence. FRST provides a less invasive and cost-effective method for measuring a range of engine indicators. We see the exciting potential of FRST in advancing gas turbine propulsion technology, particularly involving smaller and more efficient engines The core of motivation is the key to our next generation of military and sustainable commercial engines

This FRST technology is currently applying for a patent, using the Rayleigh scattering principle. It utilizes ultraviolet spectroscopy and relies on the light scattered by air molecules passing through the laser irradiated area to provide information about the gas flow field, ultimately accurately deriving thrust.

The signals they get from Rayleigh scattering transform all the information about speed, temperature and density into the form of spectrum. Light from high-power lasers will be transmitted through a fiber optic cable system to limited imports or exports. The notch filter sensor installed around the intake or exhaust duct can also transmit reflected light back to the camera installed remotely in the cabin. These scattering will be recorded by high-performance cameras and "filtered" out the damage in the signal. Then, the optical data from the camera is transmitted to the processor for spectral analysis.

In the past, traditional sensors and probes were difficult to install and could lead to airflow blockage (only measuring the flow in discrete parts of the gas path), especially on small engine cores with limited space. With FRST Optical instrument, the engineering team is expected to save traditional sensors and probes.

In addition, FRST also provides the advantage of measuring non carbon dioxide particle emissions, which may help the entire industry understand and mitigate the environmental impact of these gas emissions, especially in terms of "wake" formation.

Todd Lowe, a professor of aerospace engineering at Virginia Tech, said: "Although the principle of Rayleigh scattering has been known to the world for centuries, engineers from Pratt&Whitney and Virginia Tech have successfully applied it to turbofan engines for the first time by taking advantage of the latest advances in computing power, laser and camera technology. As we are committed to advancing the flight demonstration of FRST, we expect that this technology will bring other applications to the development and certification of aircraft engines."

Pratt&Whitney and Virginia Tech have long-term cooperation in promoting technology development, focusing on advanced instruments. The joint research team of both parties successfully used FRST optical technology to measure engine thrust on a small business jet engine at Virginia Tech, including Honeywell TFE731 and Pratt&Whitney Canada PW300, and achieved accuracy similar to traditional sensors and probes. The team is currently committed to conducting flight development testing of this technology.

Source: OFweek