Air Cycle Machine Strut Plate Assembly for Surge Margin Under Blockage
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Solution Overview
Problem
Conventional air cycle machines in aircraft environmental control systems face reduced performance due to heat exchanger blockage from dust or contaminants, which can push the fan rotor closer to its surge limit, leading to reduced tolerance to blockage and inefficient air conditioning.
Innovation Solution
An air cycle machine with a strut plate assembly featuring a first strut plate without inner struts between the fan rotor and the ejector, and a second strut plate with inner and outer struts between the ejector and the diffuser cone, forming an ejector that reduces blockage and swirl angle effects, and aligns inner struts with the fan rotor's design point condition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional strut plate designs are used with heat exchanger cooling flow, then the fan rotor can establish flow, but the heat exchanger becomes partially clogged due to dust or contaminants that reduce available flow volume to the fan rotor, pushing the fan rotor closer to its surge limit
Solution Approach 1:
The ejector is extracted as a separate functional component between the first and second strut plates, creating a dedicated flow enhancement zone that operates independently from the conventional strut plate structure. This extraction allows the ejector to specifically address flow volume reduction caused by heat exchanger blockage without modifying the entire strut plate assembly.
Solution Approach 2:
The ejector modifies flow parameters by creating a low-pressure zone that draws additional air through the heat exchanger, changing the pressure distribution and flow velocity characteristics. This parameter change enables the system to maintain adequate flow volume even when the heat exchanger is partially clogged, preventing the fan rotor from approaching its surge limit.
2Productivity
If designs attempt to enhance flow as the fan rotor approaches its surge limit, then flow volume is increased, but performance is reduced when operating under off-design conditions
Solution Approach 1:
The ejector creates a dynamic flow enhancement mechanism where the low-pressure zone is generated by the interaction between the first and second strut plates. This dynamic pressure differential automatically adjusts to maintain optimal flow characteristics across varying operating conditions, including off-design scenarios, without requiring mechanical adjustment or complex control systems.
Solution Approach 2:
The ejector acts as an intermediary component between the strut plates and the heat exchanger cooling flow. It mediates the flow characteristics by creating a low-pressure zone that draws additional air through the heat exchanger, thereby improving off-design performance without directly modifying the fan rotor or heat exchanger structures.
3Strength
If the first strut plate includes inner struts between the fan rotor and the ejector, then structural support is provided, but ejector blockage and swirl angle effects increase
Solution Approach 1:
Inner struts are extracted from the first strut plate in the region between the fan rotor and the ejector, eliminating the source of blockage and swirl angle effects. This selective removal maintains structural support through outer struts while clearing the flow path for the ejector to operate effectively without interference from internal structural elements.
Solution Approach 2:
The strut plate assembly is segmented into functional zones: the first strut plate provides external support with outer struts but lacks inner struts to avoid blocking the ejector, while the second strut plate includes both inner and outer struts positioned downstream of the ejector. This segmentation allows each component to fulfill its specific function without interfering with others.
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
The solution enhances air flow by reducing ejector blockage and improving strut alignment, maintaining performance even under off-design conditions and heat exchanger blockage, ensuring efficient air conditioning.
Implementation Method 1
An air cycle machine with a strut plate assembly featuring a first strut plate without inner struts between the fan rotor and the ejector, and a second strut plate with inner and outer struts between the ejector and the diffuser cone, forming an ejector that reduces blockage and swirl angle effects
Data Source
AI summary
According to one aspect, an air cycle machine includes a fan rotor, a diffuser cone axially aligned with the fan rotor, and a strut plate assembly. The strut plate assembly includes a first strut plate and a second strut plate with an ejector formed between the first strut plate and the second strut plate. The first strut plate is axially positioned between the fan rotor and the ejector, and the second strut plate is axially positioned between the fan rotor and the diffuser cone. The first strut plate includes a plurality of outer struts and is absent inner struts between the fan rotor and the ejector. The second strut plate includes a plurality of inner struts and outer struts, where the inner struts are axially positioned between the ejector and the diffuser cone.