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Flow Measurement

Non-Seeded Flow Measurement

Prime Photonics is working on optical measurement of non-seeded flow.  The goal is to measure 3 components of flow velocity, temperature, and pressure of the flow.

Most flow measurement techniques require a seeded flow, meaning that specific traceable particles are added to the flow.  This can be in the form of large particles which can be detected individually or fluorescent particles.

The Prime Photonics system does not require any particle to be added to the flow, making the technique usable in places where seeded flow is not an option.  Examples include in-flight testing of aircraft engines, heavily distorted flows where seeding particles cannot reach certain areas (such as inside a vortex), or measurements close to a wall or obstacle (including boundary layer measurements).



Application 1: Inlet Distortion Characterization

Prime Photonics is working on the development of an inlet distortion measurement system based on filtered Rayleigh Scattering (FRS).

The goals of this research program are to:

  • Identify and characterize swirl conditions for gas turbine engine inlets
  • Develop a compact, low-cost FRS system suitable for ground-based test (near-term) and on-wing distortion characterization (mid-term)

In cooperation with Virgina Tech, the team is developing scalable methods to measure planar velocity, temperature, and pressure of flows.

The velocimetry portion is extremely robust, with high spatial resolution and velocity uncertainties in the order of 1 m/s.

Scalar measurements are less mature but developing rapidly:

  • Temperature uncertainty in the order of +/- 3K
  • Pressure uncertainty of +/- 500 Pa

These FRS measurements have benefits in spatial resolution over single-point probes or probe rakes.


Application 2: Boundary Layer

Prime Photonics is also working on applying the technology to near-wall conditions and measure velocity profiles of boundary layers without seeded particles.


Technology: Filtered Rayleigh Scattering

The measurement technique is called Filtered Rayleigh Scattering.

Rayleigh Scattering is a wave optics phenomenon resulting from the interaction of light and matter on the scale or smaller than the wavelength of the light.  All information needed for temperature, pressure, and velocity measurement is contained within the Rayleigh scattered light signal.  Particle scattering and reflections are much stronger than the Rayleigh signal.  Filtered Rayleigh scattering is a means to measure the spectrum of the Rayleigh signal.

Filtered Rayleigh Scattering yields one- to three-component mean flow velocity, mean temperature and mean pressure; total pressure and total temperature.


More Information

To learn more about our research on inlet distortion please contact us by filling out the form below.


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