Light Extinction Tomography for Ice Crystal Detection
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Solution Overview
Problem
Current systems lack a non-intrusive, efficient method to measure ice or water particle density in aircraft engines at high altitudes, particularly in wind tunnels, requiring a system that is remotely operable, minimally invasive, fast, and provides good resolution without moving parts or significant optical access.
Innovation Solution
An optical tomography system using electromagnetic emitters and detectors configured around a wind tunnel, employing a controller to reconstruct particle density maps through tomography algorithms, which measures light extinction and calibrates based on dark current and unextinguished light intensity, allowing for the detection of ice or water particles in a cross-section of air flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electromagnetic emitters and detectors are placed around the wind tunnel cavity, then particle density measurement capability is improved, but the system complexity and device complexity increase
Solution Approach 1:
The system divides the measurement task into multiple discrete electromagnetic emitters and detectors positioned around the cavity. Each emitter-detector pair provides a specific measurement projection, and the complete particle density distribution is reconstructed by combining all projections through tomography algorithms. This segmentation allows precise local measurements while distributing system complexity across multiple simple, identical components.
Solution Approach 2:
The patent introduces electromagnetic radiation as an intermediary medium between the measurement system and the particles. The emitters generate electromagnetic radiation that passes through the particle-laden flow, and detectors measure the attenuated radiation. This intermediary enables non-contact, non-intrusive measurement of particle density without physically interacting with the flow.
2Measurement precision
If the support frame substantially surrounds the cavity, then measurement coverage and resolution are improved, but the intrusion into the airflow increases
Solution Approach 1:
The support frame is designed as a thin-walled structure that substantially surrounds the cavity while minimizing airflow disruption. The frame provides structural support for mounting emitters and detectors while its thin construction allows air to flow through and around it with minimal disturbance, maintaining both measurement coverage and airflow integrity.
Solution Approach 2:
The system transitions from point measurements to distributed spatial measurements by positioning emitters and detectors around the entire cavity perimeter. This dimensional expansion from single-point to circumferential measurement provides comprehensive cross-sectional coverage without requiring deep intrusion into the airflow path at any single location.
3Measurement precision
If multiple electromagnetic emitters are cycled on-and-off in illumination patterns, then particle density reconstruction accuracy is improved, but the measurement time and data acquisition complexity increase
Solution Approach 1:
The system employs periodic cycling of electromagnetic emitters in structured illumination patterns, where each emitter is activated in sequence for brief intervals. This periodic activation allows systematic collection of projection data from multiple angles while maintaining temporal resolution of particle density variations. The cyclic nature enables complete data acquisition for tomographic reconstruction without requiring all emitters to operate simultaneously.
Solution Approach 2:
The controller pre-plans and sequences the illumination patterns before data acquisition begins. The cyclic activation schedule for each emitter is predetermined, allowing the system to efficiently collect all necessary projection data in a systematic manner. This preliminary structuring of the measurement sequence optimizes data acquisition speed and ensures complete coverage for accurate reconstruction.
4Reliability
If the system uses non-intrusive electromagnetic radiation for measurement, then reliability and safety are improved, but the ability to measure small particles like ice crystals is reduced
Solution Approach 1:
The system measures optical extinction parameters (attenuation of electromagnetic radiation) rather than directly imaging particles. By analyzing changes in radiation intensity, wavelength, and polarization as electromagnetic waves pass through the particle-laden flow, the system can infer particle density, size distribution, and composition. This indirect parameter measurement enables detection of small ice crystals through their optical effects without requiring direct visual resolution.
Solution Approach 2:
The system creates an indirect optical copy or representation of the particle distribution through extinction measurements. Rather than directly imaging each particle, the detectors measure the cumulative effect of all particles along each line of sight, creating projection data that is then reconstructed into a tomographic image. This copying approach allows measurement of small particles through their aggregate optical impact on electromagnetic radiation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate, real-time detection of particle density with high resolution, supporting safe engine operation by identifying potential icing conditions and providing archival records of particle distributions, thus preventing power loss events due to ice ingestion.
Implementation Method 1
The electromagnetic emitters are displaced along the support frame and are configured to emit electromagnetic radiation toward the cavity and illuminated at least a cross-section of the flow of air
Implementation Method 2
measuring light extinction and calibrates based on dark current and unextinguished light intensity, allowing for the detection of ice or water particles
Implementation Method 3
From the acquired measurements, the controller reconstructs an extinction map of the cross-section of the flow of air using a tomography algorithm
Data Source
AI summary
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. Imaging is accomplished via star-shaped source and detector arrays.