Light extinction tomography for measurement of ice crystals and other small particles
Inventors
Bencic, Timothy J. • Rohler, David P. • Fagan, Amy F. • Izen, Steven H. • Maniyedath, Arjun K.
Assignees
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Publication Number
US-10908061-B2
Publication Date
2021-02-02
Expiration Date
Abstract
A tomography duct for wind tunnels includes a plurality of light sources and sensors displaced around a support structure. The light sources are cycled and sensor measurements are made from sensors opposite the light sources. Tomographic algorithms are used to determine an extinction map from the sensor measurements. The extinction map provides details about particles in a cross-section of the air flow through the tomography duct.
Core Innovation
The invention relates to light extinction tomography for measuring ice/water particles and other small particles in air flow. A tomography duct passes an air flow through a support frame or cavity while light is emitted across the tomography duct and received by sensor elements positioned across the duct. The system measures unextinguished light intensity of the emitted light and extinguished light intensity caused by one or more particles in the air flow to form data for reconstructing an extinction map.
The invention calibrates a tomography algorithm based at least in part on a measured dark current of a sensor element and the measured unextinguished light intensity. Using the calibrated tomography algorithm and the measured extinguished light intensity, the invention reconstructs an extinction map of a cross-section of the air flow. The tomography algorithm is described as being usable with reconstruction approaches including a single scattering model and options such as diffraction tomography and truncated SVD, including for rectangular geometry.
The invention also supports temporal updating using partial acquisitions and uses an illumination pattern with cycling illumination. In at least one described implementation, a plurality of light sources is cycled on-and-off in the illumination pattern disposed in the tomography duct, and sensor measurements are taken during each on-cycle. Partial acquisition data are used to update reconstructions in near real time, with measurement and illumination sequencing described in relation to practical system components.
Claims Coverage
The independent claim (clm-00001) covers a particle tomography method that reconstructs an extinction map from calibrated sensor measurements, with an explicit dark-current and unextinguished-intensity calibration and extinction-based reconstruction of a cross-section of an airflow. The dependent claims shown (clm-00002 through clm-00010) refine particle types, system contexts, illumination cycling, intensity control, and temporal updating using partial acquisitions.
Dark current measurement and unextinguished intensity calibration
measuring a dark current of a sensor element and measuring an unextinguished light intensity of the emitted light; calibrating a tomography algorithm based at least in part on the dark current and the unextinguished light intensity
Emitting across a tomography duct and receiving sensor measurements through airflow
emitting light from a light source across a tomography duct through which an air flow can be passed and receiving, by a sensor element positioned across the tomography duct, the emitted light
Measuring particle-caused extinguished intensity
measuring on the sensor element an extinguished light intensity of the emitted light caused by the one or more of the plurality of particles in the air flow
Extinction map reconstruction of airflow cross-section
reconstructing, using the calibrated tomography algorithm, an extinction map of a cross-section of the air flow based at least in part on the extinguished light intensity
Particle type selection for the plurality of particles
receiving a plurality of particles into the air flow, wherein the plurality of particles is selected from water droplets, supercooled water droplets, and ice particles
Tomography duct configured for selected particle-density detection systems
receiving a plurality of particles into the air flow, wherein the tomography duct is configured to detect particle density in one of several systems selected from smokestack emission detection, atmospheric particulate density detection, airborne volcanic ash detection, icing condition detection, jet engine intake/jet engine, wind tunnel, and spray system/spray nozzle
Light intensity adjustment based on unextinguished intensity
adjusting the intensity of the light emitted from the light source based on the measured unextinguished light intensity
Cycling multiple light sources in an illumination pattern and measuring on-cycles
cycling on-and-off a plurality of light sources in an illumination pattern disposed in the tomography duct, and measuring extinguished light intensity during each light-source on-cycle
Real-time temporal updating with partial acquisition reconstruction updates
reconstructing the extinction map using a tomography algorithm each time a light source is cycled on-and-off, with partial-acquisition data replacing prior partial-acquisition data for real-time temporal updating
Across the independent claim and shown dependent refinements, the core inventive scope is directed to reconstructing an extinction map of an airflow cross-section using a tomography algorithm calibrated with sensor dark current and unextinguished light intensity, together with extinguished-light measurements caused by particles, and further refined by particle type/system context selection, light intensity adjustment, illumination-pattern cycling across multiple light sources, and reconstruction updates for real-time temporal updating using partial acquisition data.
Stated Advantages
Provides real-time temporal updating of reconstructions using partial acquisitions.
Measures particle-caused extinction to reconstruct an extinction map of a cross-section of an air flow.
Supports detection for multiple particle categories including water droplets, supercooled water droplets, and ice particles.
Documented Applications
Real-time and archival particle density for ice clouds.
Nozzle/spray diagnostics.
Jet engine intake icing monitoring.
Atmospheric particulates including volcanic ash.
Smoke stack emission analysis.
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