Aspirated Total Air Temperature Probe Boundary Layer Control
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Solution Overview
Problem
Conventional total air temperature (TAT) probes face challenges in icing conditions, where ice accumulation can clog the sensor, and at low mass flows, boundary layer separation leads to inaccurate measurements and deicing heater errors due to uncontrolled heating of internal air layers.
Innovation Solution
The TAT probe design includes a primary airflow passage with bleed ports and a cross-port to control the boundary layer, an aspiration tube for cooling, and an aspiration aperture to maintain pressure balance, ensuring symmetrical deicing heater error behavior and improved performance across varying angles of attack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If bleed ports and cross-port are used to control boundary layer, then deicing heater error is reduced, but device complexity increases
Solution Approach 1:
The probe structure is segmented into multiple functional zones: a primary airflow passage for main flow, a cross-port for lateral pressure equalization, and multiple bleed ports distributed along the inner surface of the elbow. This segmentation allows independent control of boundary layer at different locations, improving measurement accuracy while maintaining manageable complexity through modular design
Solution Approach 2:
The cross-port acts as an intermediary element that couples the bleed ports to the aspiration tube system. It distributes the pressure equalization function across multiple components, mediating between the boundary layer control requirement and the aspiration flow management, thereby reducing deicing heater error without requiring direct complex interaction between all components
2Reliability
If aspiration tube is added for cooling, then anti-icing performance improves, but device complexity increases
Solution Approach 1:
The aspiration tube is merged with the existing structural cavity of the probe, utilizing the internal space already available in the probe body. The tube integrates with the cross-port system and elbow structure, combining the cooling function with the existing boundary layer control architecture rather than adding completely separate components
Solution Approach 2:
The aspiration tube serves multiple functions: it provides active cooling to prevent ice formation on the sensing element, and it works in conjunction with the cross-port and bleed ports to manage boundary layer pressure distribution. This multi-functionality reduces the need for separate dedicated components for each function
3Device complexity
If conventional TAT probe design is used, then device simplicity is maintained, but measurement precision deteriorates in icing conditions
Solution Approach 1:
The harmful boundary layer and ice-forming conditions are extracted from the sensing element environment through the bleed ports that actively remove boundary layer air, and the aspiration tube that extracts heat and moisture. This extraction prevents ice accumulation on the sensing element while maintaining overall probe structural simplicity
Solution Approach 2:
The bleed ports and aspiration system provide preliminary anti-icing action by actively managing the boundary layer and cooling the sensing element before ice can form. The deicing heater works in conjunction with these features to prevent ice accumulation proactively rather than reacting after ice forms, maintaining measurement precision without requiring complex ice removal mechanisms
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
This design enhances the accuracy of TAT measurements by preventing ice accumulation, reducing deicing heater errors, and maintaining consistent performance during changes in flight conditions, thereby improving the anti-icing performance and reducing measurement inaccuracies.
Implementation Method 1
an aspiration aperture in the cross-port can be centered in the cross-port and couples the cross-port to the internal cavity of the strut of the probe. Area ratios are also controlled to enhance performance of both swept sensor flow passage and non-swept sensor flow passage probes
Implementation Method 2
An aspiration tube in an internal cavity of the probe aids in cooling the probe during standstill or low airflow conditions
Implementation Method 3
Conventional TAT probes have incorporated an elbow, or bend, to inertially separate these particles from the airflow before they reach the sensing element
Implementation Method 4
Anti-icing performance is facilitated by heater elements embedded in the housing walls
Implementation Method 5
a favorable pressure difference is created which removes a portion of the boundary layer through the bleed holes, and pins the remaining boundary layer against the elbow's inner wall
Data Source
AI summary
A total air temperature probe includes an inlet through which airflow enters a primary airflow passage through the probe. A sensor flow passage is connected to the primary flow passage. Bleed ports extend between the primary airflow passage and a cross-port which extends laterally across the probe. An aspiration aperture in the cross-port couples the cross-port to an internal cavity of a strut of the probe. The aspiration aperture can be centered within the cross-port to provide symmetrical deicing heater error behavior of the probe during changes in angle of attack. An aspiration tube couples the internal cavity of the probe to a pressure source.