Optical In-Flight Thrust Measurement via Rayleigh Scattering

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Solution Overview

Problem

Existing methods for determining propulsion mass flow and thrust in gas turbine engines are inaccurate and rely on ground-based extrapolations, lacking direct in-flight measurements, which hinders precise engine control and integration with airframes.

Innovation Solution

An optically-based measurement system using lasers and spectrally-sensitive cameras to perform non-intrusive in-flight measurements of mass flow and thrust by analyzing Rayleigh/Mie scattering of light, calculating mass and momentum flux through rigorous integral conservation equations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If ground-based extrapolation methods are used to determine propulsion mass flow and thrust, then device complexity is reduced, but measurement precision deteriorates due to inaccuracies in estimating in-flight conditions

Engineering Contradiction:

Improvethrust measurement precisionVSAvoidmeasurement system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces traditional mechanical measurement systems (balance beams, load cells) with an optical measurement system using lasers and spectrally-sensitive cameras to detect Rayleigh/Mie scattering. This substitution enables non-intrusive in-flight measurements while maintaining measurement precision, resolving the contradiction between accuracy and system complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces light scattering (Rayleigh/Mie scattering) as an intermediary phenomenon to indirectly measure mass flow and thrust parameters. By measuring the scattering of light by gas molecules in the engine flow, the system derives thrust information without direct mechanical contact, achieving both precision and reduced complexity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If non-intrusive optical measurement systems are implemented, then measurement precision improves through direct in-flight measurements, but device complexity increases due to additional sensors and processing requirements

Engineering Contradiction:

Improvemeasurement reliabilityVSAvoidoptical system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The measurement system utilizes the engine's own exhaust flow as the measurement medium. The gas molecules in the exhaust naturally scatter light, providing the measurement signal without requiring additional tracers or modifications to the engine operation. This self-service approach enhances reliability while managing system complexity.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The system measures changes in optical parameters (light scattering intensity and spectrum) that correspond to changes in mass flow and thrust. By monitoring these optical parameter variations, the system achieves reliable measurements without complex mechanical instrumentation.

Inventive Principle:

Principle #35Parameter changes

3Loss of information

If traditional estimation methods are used, then ease of operation is maintained, but loss of information occurs due to uncertainties in ground-based extrapolations

Engineering Contradiction:

Improvethrust data accuracyVSAvoidmeasurement system operation

Core Design Contradiction:

Loss of informationVSEase of operation

Solution Approach 1:

The system provides real-time feedback by continuously measuring mass flow and thrust parameters during flight operations. This feedback loop eliminates the information loss associated with post-flight analysis or ground-based estimations, allowing operators to make informed decisions based on actual in-flight data while maintaining ease of operation through automated measurements.

Inventive Principle:

Principle #23Feedback

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

Provides accurate and reliable in-flight measurements of thrust and mass flow, supporting engine and airframe manufacturers in optimizing engine operation and control, reducing uncertainties associated with ground-based estimations.

Implementation Method 1

Methodology Applied

Scientific EffectRayleigh scattering: Rayleigh Scattering

Implementation Method 2

Methodology Applied

Scientific EffectMie scattering: Scattering

Data Source

PatentEP4112886B1In-flight measured propulsion mass flow and thrust on aircraft

Publication Date: 2025.06.25 RTX CORP

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AI summary

An aircraft (10) includes a gas turbine engine (20) and an optically-based measurement system (100). The gas turbine engine (20) is configured to ingest a first mass flow and to exhaust a second mass flow. The optically-based measurement system (100) is configured to determine the first and second mass flows in response to performing an imaging process on the gas turbine engine (20).