Strain Sensor Airflow Sensing Without Icing or Moving Parts
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Solution Overview
Problem
Conventional sensors for determining relative velocity and angle of attack between fluids and bodies are prone to icing, lack sensitivity, increase drag, and are unreliable due to environmental exposure and wear, leading to safety risks in aviation and other applications.
Innovation Solution
An apparatus using a deflecting element joined to a fluid-contacting surface and a strain sensor coupled to a non-fluid-contacting surface to measure strain, eliminating moving parts and environmental exposure, with optional temperature, altitude, and pressure sensors for correction and validation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Pitot-static tubes are used for velocity measurement, then relative velocity can be measured, but the tubes are subject to icing and increase drag on the vehicle
Solution Approach 1:
The strain sensor is extracted from the fluid-contacting environment and mounted on the non-fluid-contacting surface of the body. This separates the sensing function from the harmful environmental factors (icing, drag), allowing accurate measurement while eliminating direct exposure to detrimental conditions.
Solution Approach 2:
The deflecting element acts as an intermediary between the fluid flow and the strain sensor. The fluid interacts with the deflecting element, which then transmits mechanical strain to the sensor through the body structure, enabling indirect measurement without direct sensor exposure to harmful conditions.
2Measurement precision
If rotating foil AOA sensors are used, then angle of attack can be sensed, but the sensors are subject to failure due to exposure to elements and wear of moving parts
Solution Approach 1:
The strain sensor is extracted from the fluid-contacting environment and mounted on the non-fluid-contacting surface. This eliminates exposure to elemental conditions and removes moving parts entirely, as the sensor measures strain through the body structure rather than through direct fluid interaction or mechanical rotation.
Solution Approach 2:
The patent replaces the mechanical rotating foil system with a strain-based measurement system. Instead of using mechanical rotation to sense angle of attack, the system uses strain sensors to detect mechanical deformation caused by fluid flow, eliminating mechanical wear and improving reliability.
3Measurement precision
If conventional mass flow sensors are used, then mass flow can be determined, but the sensors are complicated and ill-suited for certain environments such as sewage monitoring
Solution Approach 1:
The strain sensor system can be applied universally across different fluid types and environments (sewage, storm drains, industrial fluids) by simply changing the deflecting element geometry and material properties. The same basic measurement principle works for all fluids, eliminating the need for environment-specific sensor designs.
Solution Approach 2:
The sensing mechanism is extracted from complex conventional mass flow sensors and simplified to a strain-based system. The strain sensor directly measures mechanical deformation caused by fluid flow, providing a simple and universally applicable solution that works in environments where conventional sensors fail.
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 reliable and accurate measurements of relative velocity, fluid flow, and angle of attack, resistant to environmental effects, enhancing safety and reducing maintenance needs.
Implementation Method 1
at least one strain sensor coupled to the non-fluid-contacting surface, wherein the at least one strain sensor is configured to detect strain imparted on the body by deflection of the at least one deflecting element
Implementation Method 2
at least one deflecting element joined to the body and extending from the fluid-contacting surface into the fluid
Data Source
AI summary
An apparatus including at least one deflecting element and at least one strain sensor is configured for determining relative velocity, fluid flow, or angle of attack between a fluid and a body having a fluid-contacting surface and an opposing non-fluid-contacting surface. The deflecting element is joined to the body and extends from the fluid-contacting surface into the fluid, while the strain sensor is coupled to the non-fluid-contacting surface and is configured to detect strain imparted on the body by deflection of the at least one deflecting element. An output signal of the at least one strain sensor permits calculation of at least one of relative velocity, fluid flow, or angle of attack between the fluid and the body. By measuring deflection of a surface of the body, the at least one strain sensor may be mounted on or along the non-fluid-contacting surface where the environment is controllable, such that the sensor is not subject to deleterious environmental effects.