Isolator Duct Strain Sensing for Ramjet Unstart Prevention
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Solution Overview
Problem
Existing ramjet engines face severe unstart events due to shock train length exceeding the isolator length, leading to loss of vehicle control and mechanical stress, which conventional pressure sensors cannot accurately measure and control.
Innovation Solution
Implementing a system with distributed strain sensors along the isolator duct to measure strain, allowing real-time estimation of the shock train leading edge position, and controlling fuel flow and back pressure to prevent unstart events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional pressure sensors are used to measure shock train position, then the measurement system is simple, but the measurement precision and spatial resolution are insufficient to accurately determine shock train leading edge position
Solution Approach 1:
The sensing system is segmented into multiple discrete strain sensors distributed along the isolator duct axis. Each sensor measures local strain independently, and the combined data provides high-resolution spatial mapping of the shock train position. This segmentation enables precise localization while keeping individual sensor components simple.
Solution Approach 2:
The patent replaces conventional pressure sensing with strain sensing on the isolator duct wall. Strain sensors measure mechanical deformation caused by shock train pressure, providing indirect but more precise measurement of shock train position. This substitution enables higher measurement precision through mechanical field coupling.
2Reliability
If the isolator length is increased to prevent unstart, then the shock train can be contained, but the engine size and weight increase
Solution Approach 1:
The strain sensing system provides real-time early warning of shock train approach to the isolator inlet. By detecting strain changes before unstart occurs, the system enables proactive control adjustments (fuel flow modulation, bleed valve actuation) to prevent unstart without requiring increased isolator length.
Solution Approach 2:
The system continuously monitors strain distribution along the isolator duct and provides feedback on shock train position. This feedback enables real-time control adjustments to maintain shock train within acceptable limits, preventing unstart events without modifying the isolator geometry.
3Reliability
If real-time control is implemented to prevent unstart, then engine stability improves, but the control system complexity increases
Solution Approach 1:
The control system uses real-time strain sensor data as feedback to monitor shock train position and adjust fuel flow and bleed valve operations. This closed-loop control maintains engine stability by preventing unstart conditions through continuous adaptation to changing flow conditions.
Solution Approach 2:
The system performs preliminary detection of shock train approach through strain sensing and executes control actions before unstart occurs. By acting in advance based on predicted shock train position, the system maintains stability with simpler control logic rather than requiring complex real-time response systems.
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
Accurately determines the shock train leading edge position with high spatial and temporal resolution, enabling proactive control to prevent unstart events and reduce mechanical stress, thus enhancing engine stability and safety.
Implementation Method 1
a plurality of strain sensors distributed axially along a radially outward surface of the isolator duct and configured to sense strain on the radially outward surface of the isolator duct
Data Source
AI summary
In some embodiments, apparatuses and methods are provided herein useful for an engine. In some embodiments, the engine includes an isolator duct extending axially from an inlet side and a burner side; a plurality of strain sensors distributed axially along a radially outward surface of the isolator duct and configured to sense strain on the radially outward surface of the isolator duct; and a processor coupled to the plurality of strain sensors. In some embodiments, the processor configured to: obtain sensor values from one or more of the plurality of strain sensors; determine a measured strain distribution based on the sensor values and axial locations of the plurality of strain sensors; and estimate a shock train leading edge position based on identifying a shock train leading edge in the measured strain distribution, where the engine system includes an air-breathing propulsion engine.