Recirculation Flow Collector for Fan Stability
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Solution Overview
Problem
At lower flight speeds or on the ground, the ram air pressure is insufficient to provide adequate airflow across heat exchangers in aircraft environmental control systems, leading to inefficient heat removal and potential fan instability due to blockages.
Innovation Solution
Incorporation of a recirculation flow collector within the ram air fan assembly that collects and recirculates air back to the fan inlet during blocked conditions, maintaining stability and airflow through a compact, one-sided recirculation path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a fan is used to provide airflow across heat exchangers at lower flight speeds, then sufficient heat removal is achieved, but fan instability and structural failures occur due to blockages
Solution Approach 1:
A recirculation flow collector is introduced as an intermediary component between the heat exchanger outlet and fan inlet. This collector captures air that would otherwise be blocked or recirculated improperly, and redirects it through a controlled path back to the fan inlet, preventing fan instability while maintaining heat removal efficiency.
Solution Approach 2:
The airflow path is segmented into distinct zones: a primary airflow path through the heat exchanger, and a separate recirculation path for blocked air. The recirculation flow collector creates a dedicated channel that separates problematic blocked airflow from the main cooling function, allowing each to be managed independently.
2Weight of moving object
If the recirculation flow collector is designed with a compact one-sided structure, then the overall size and weight of the assembly are reduced, but the complexity of ensuring adequate airflow distribution increases
Solution Approach 1:
The recirculation flow collector utilizes the vertical dimension by extending upward from the heat exchanger outlet to engage with the fan inlet from below. This three-dimensional arrangement allows compact one-sided installation while maintaining adequate airflow distribution through strategic positioning and shaping of the collector in multiple spatial dimensions.
Solution Approach 2:
The recirculation flow collector serves multiple functions simultaneously: it acts as a flow straightener, a recirculation chamber, and a structural support element. By combining these functions into a single integrated component, the design reduces overall assembly complexity despite the sophisticated airflow management required.
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
Prevents fan instability and structural failures by ensuring a steady airflow, allowing for efficient heat removal and reducing the overall size and weight of the ram air fan assembly.
Implementation Method 1
an ejector having a first opening at a first end of the ejector, a second opening at a second end of the ejector, and a third opening at a side wall of the ejector between the first end and the second end
Implementation Method 2
a diffuser positioned within the outer housing and having a diffuser inlet and a diffuser outlet
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A recirculation flow collector (56) for a fan includes an arcuate housing, a first face (66) with a first circular opening (67) to receive flow; a second face (68) with a second circular opening (69) to allow flow in a normal fan operating condition and an outlet (72) in a bottom (70) of the arcuate housing to allow recirculation flow.