Filtered Rayleigh Scattering Approach for Multi-Property Flow Measurement in Tactical Aircraft Inlets Navy SBIR FY2016.1 Sol No.: Navy SBIR FY2016.1 Topic No.: N161-011 Topic Title: Filtered Rayleigh Scattering Approach for Multi-Property Flow Measurement in Tactical Aircraft Inlets Proposal No.: N161-011-0717 Firm: Prime Photonics, LC 1116 South Main Street Blacksburg, Virginia 24060 Contact: Todd Pickering Phone: (540) 251-2957 Web Site: http://www.primephotonics.com Abstract: The development of new military aircraft with improved stealth, lower ground noise and higher efficiency engine designs is driving increasingly complex inlet geometries. The momentum created by a gas turbine engine is highly dependent on the characteristics of the incoming airflow, necessitating accurate understanding of inlet flow distortion characteristics to ensure proper operation over the entire operational envelope. As such, design engineers must account for possible distortions to that inlet flow when designing and testing prototype aircraft. To assist with current and future engine/aircraft design and development, new distortion characterization technologies are required. Although characterization of the inlet flow properties can be done during development, these techniques are often invasive. Common techniques for characterization use pitot tubes that can perturb the flow. Furthermore, damage to sensors that protrude into the flow can result in expensive domestic object damage events. More critically, the operability of the engine can be influenced by thermal, pressure, or swirl distortion. Certain combinations of angle of attack and flight speed can lead to surge conditions, potentially causing expensive damage to engines. Prime Photonics proposes to work with the TurboLab of Virginia Tech to develop a robust, minimally invasive, flight-ready inlet distortion characterization system. Benefits: The proposed Rayleigh scattering-based flow characterization technology has significant advantages over other characterization techniques, including:  Complete flow characterization: not only characterizes pressure, density, and temperature, but also provides flow angle, enabling complete characterization of inlet flow properties.  Minimally Intrusive: small engine penetrations, multifunction send/receive sensors at each port  Does not penetrate flow path: Will not perturb flow, is not sensitive to FOD, is not a potential source of DOD  Rejection of Specular Signals: Right angle periscope probes will not sample specular reflections arising from interaction of the source laser with engine sidewalls, significantly increasing signal to noise and decreasing laser power requirements. Furthermore, frequency scanning and cross correlation will further boost signal to noise ratio.  Accurate: Using conservative values, the Phase I system will characterize velocity to �10m/s, temperature to �20K, and pressure to �5%. During subsequent developmental efforts, accuracy figures can be significantly reduced.  Compact: The final system will feature small diameter sensors, fiber optic bundles, and instrumentation optimized for size and weight to reduce the load to aircraft.  Particle independent: Rayleigh scattering techniques are not dependent on particle-seeded flows, but operate through characterization of the air flowing through the inlet. Return