Air cycle machine system with a fan inlet diffuser housing
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Solution Overview
Problem
Air cycle machine systems in aircraft face performance reduction due to heat exchanger clogging, which limits fan rotor efficiency and surge tolerance, and pose challenges in reducing weight while maintaining structural integrity.
Innovation Solution
A fan inlet diffuser housing made from composite materials with specific reinforcement patches and transition regions, along with an ejector gap design, to enhance structural integrity and flow recirculation, and a method for installing the housing to optimize airflow and structural support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the heat exchanger becomes clogged with dust or contaminants, then the available flow volume to the fan rotor is reduced, but the fan rotor is pushed closer to its surge limit and performance is reduced
Solution Approach 1:
The diffuser vane is made movable rather than fixed, allowing it to change position dynamically. When the heat exchanger is clean, the diffuser vane is in a first position optimized for normal flow. When the heat exchanger becomes clogged, the diffuser vane can move to a second position that redirects airflow to maintain fan rotor performance and prevent surge, thus adapting to changing conditions.
Solution Approach 2:
The system changes the flow path parameters by moving the diffuser vane between different positions. This alters the airflow direction and distribution characteristics, enabling the system to optimize performance under different heat exchanger clogging conditions and maintain tolerance to blockage.
2Reliability
If designs attempt to enhance flow as the fan rotor approaches its surge limit, then surge tolerance may be improved, but performance under off-design conditions is reduced
Solution Approach 1:
The movable diffuser vane allows the system to dynamically adjust between two optimized configurations. In the first position, the system is optimized for normal design conditions with maximum performance. In the second position, the system is optimized for off-design conditions with reduced surge tolerance but improved flow enhancement. This dynamic adjustment resolves the contradiction by allowing the system to operate at peak efficiency under normal conditions while still providing surge protection when needed.
3Weight of moving object
If weight is reduced for aerospace applications, then fuel efficiency is improved, but structural integrity may be compromised
Solution Approach 1:
Instead of uniformly thickening the housing structure throughout, reinforcement patches are applied only at specific locations where structural integrity is most needed. This localized reinforcement approach adds minimal weight while providing targeted strength enhancement at critical stress points, resolving the contradiction between weight reduction and structural integrity.
Solution Approach 2:
The housing utilizes composite material construction with reinforcement patches, combining materials with different properties to achieve optimal strength-to-weight ratio. The composite structure provides the necessary structural integrity while maintaining reduced weight for aerospace applications.
Data Source
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AI summary
A fan inlet diffuser housing (115) includes a housing body (120) of composite material and includes a heat exchanger interface portion (220) positioned between an ejector housing portion (222) and a bypass housing portion (224). A first transition region (226) is formed between the heat exchanger interface portion (220) and the ejector housing portion (222) including an air cycle machine end reinforcement patch proximate to a heat exchanger interface. The air cycle machine end reinforcement patch includes a first patch thickness and a second patch thickness, and a ratio of the first patch thickness to the second patch thickness is between 2.02 and 3.11. An ejector (128) is formed having an ejector gap width between a nozzle portion and a diffuser portion within the ejector housing portion of the housing body. The diffuser portion (126) has a downstream ejector gap width, and a ratio of the downstream ejector gap width to the ejector gap width is between 4.62 and 5.01.