Air cycle machine with cooling air flow path
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Solution Overview
Problem
Conventional air cycle machines for aircraft environmental control systems face inefficiencies due to leaks in the cooling air supply system, leading to energy loss and potential bearing failure from heat generation during operation.
Innovation Solution
An air cycle machine cooling system that includes an orifice at the outlet of the airflow path to maintain a higher pressure in the cooling air chamber than the compressor inlet, ensuring that any leaks result in the return of cooling air to the system rather than energy loss, and utilizes hydrodynamic fluid film bearings for both lubrication and cooling, reducing the need for maintenance and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If check valves and seals are used to close the cooling air inlet, then leakage is reduced and system efficiency is improved when the air cycle machine is not running, but the components are susceptible to leaks and require maintenance
Solution Approach 1:
The patent removes check valves and seals from the cooling air inlet system, extracting the problematic components that required maintenance. Instead of using mechanical closing components, the system relies on pressure differential created by the orifice to prevent leakage, eliminating the need for maintenance-prone valves and seals.
Solution Approach 2:
The orifice design creates a self-regulating pressure differential that automatically prevents leakage without requiring active control components. The system uses its own operating parameters (pressure differential across the orifice) to maintain sealing, eliminating the need for external check valves or seals that would require maintenance.
2Temperature
If cooling air is supplied from a single high pressure source, then cooling effectiveness is improved, but any leaks cause significant energy loss and efficiency reduction
Solution Approach 1:
The orifice is positioned to create a pressure differential that anticipates and prevents leakage before it occurs. By establishing higher pressure in the cooling air chamber relative to the compressor inlet through the orifice design, the system proactively counteracts the tendency for leakage, preventing energy loss before it can happen.
Solution Approach 2:
The patent converts the potential harm of high-pressure cooling air leakage into a benefit by using the pressure differential across the orifice to create a sealing effect. The same high pressure that could cause leakage is instead used to maintain higher pressure in the cooling chamber, preventing leakage and turning a potential problem into a solution.
3Reliability
If bearing cooling airflow is supplied to reduce heat generation, then bearing reliability is improved, but system complexity increases with check valves and seals
Solution Approach 1:
The patent extracts the complex valve and seal components from the bearing cooling system. By removing check valves and seals, the system achieves bearing cooling functionality without the complexity and reliability issues associated with these closing components, while still maintaining bearing reliability through continuous cooling airflow.
Solution Approach 2:
The orifice serves multiple functions: it meters the cooling air flow to bearings, creates the pressure differential needed to prevent leakage, and simplifies the overall system by eliminating the need for separate valves and seals. This multi-functionality reduces system complexity while maintaining bearing reliability.
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 system enhances energy efficiency by minimizing energy loss through leaks and prolongs bearing lifespan by effectively managing heat dissipation using air as both a lubricant and coolant, reducing the risk of structural failure.
Implementation Method 1
Hydrodynamic fluid film journal bearings, also called journal air bearings or foil bearings, can be used to provide support to rotatable components such as shafts
Implementation Method 2
During operation, rotation of the rotatable component causes a working fluid to form a cushion (often referred to as an 'air bearing') that supports the rotatable component with little or no direct contact
Implementation Method 3
During operation, the bearings may be rotated at speeds that result in heat generation
Implementation Method 4
cooling air is conveyed and passed over bearing surfaces to remove the heat from the bearing
Data Source
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AI summary
An air cycle machine (400) comprises rotating components that include a fan, a compressor, and a first turbine. The air cycle machine (400) also includes a cooling airflow path (406) that receives cooling air from a cooling air source, directs the cooling air to an air-cooled bearing (406,408,412,414) for at least one of the rotating components, and discharges the cooling air. The airflow path (406) is isolated from an inlet (422) of the compressor by a seal member (260), and the airflow path (406) is configured to maintain pressure at the seal member (420) above a pressure at the compressor inlet (422).