Luna is developing a distributed anemometer that can directly measure flow field velocity profiles using high-definition fiber optic sensing (HD-FOS). The concept is inspired by hot-film anemometry, but extends the capability from a point measurement to a distributed measurement. With a spatial resolution of 1.25 mm, thousands of data points can be collected along an optical fiber to enable 1D, 2D or 3D field measurements, depending on the routing of the sensor. The benefits of this approach compared to particle image velocimetry (PIV) include: no seeding of the flow is necessary; the sensor can be used in non-line-of-sight locations; velocity and temperature profiles can simultaneously be acquired; and the technology can potentially be implemented in a flying vehicle. Measurements of boundary layer velocity and temperature profiles, transition location, and skin friction can be attained with this technique. Phase I will prove the feasibility of flow velocity measurement from a distributed fiber optic sensor over a range of temperatures and Mach numbers to quantify its accuracy. During Phase II, the technology will be matured for implementation in NASA wind tunnels and commercial jet engines. During Phase III, Luna will work with NASA and industry partners to commercialize the technology.
POTENTIAL NASA COMMERCIAL APPLICATIONS
Distributed hot-film anemometry can revolutionize ground-based aerodynamic testing for wind tunnels and air-breathing engines. Instead of sensor rakes or traverses to probe the flow, thousands of velocity measurements will be acquired simultaneously from a single optical fiber. This capability can be used in wind tunnel calibration to document boundary layer profiles, uniformity of the tunnel flow, measurements of flow fore and aft of a model, and identify areas of unsteady or separated flow. For engine testing applications, radial and circumferential distributed anemometer sensors will fully document the engine inlet flow and distortion entering the fan and compressor. Further adaptation of the technique can allow for flow measurements in the hot section of engines. The high-resolution velocity and temperature profile data can be used to validate CFD models and optimize future vehicle designs for maximum efficiency.
POTENTIAL NON-NASA COMMERCIAL APPLICATIONS
Luna?s high-resolution flow velocity measurements will provide unprecedented data to better understand flow fields being ingested by turbofan jet engines. This will allow for optimization of inlet geometry, fan blade design, and serpentine ductwork flow profiles. The end result will be more efficient engines with reduced specific fuel consumption (SFC) that weigh less than current state-of-the-art engines. There is significant interest in understanding the flow and temperature profiles in the cold and hot sections of turbine engines, and this technology will provide visualization of this critical data.