Reverse Bootstrap Air Cycle Machine with Motor-Assisted Ground Cooling
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Solution Overview
Problem
Reverse bootstrap air cycle machines on aircraft face challenges in providing sufficient cooling when RAM air pressure is below ambient pressure, particularly on the ground, as the turbine and compressor may not generate adequate vacuum to cool heat loads effectively.
Innovation Solution
Incorporating an electric motor connected to the shaft of the reverse bootstrap air cycle machine to drive the compressor and turbine, with an electronic controller that activates the motor when RAM air pressure is below a threshold to ensure cooling, and bypassing components during high RAM air pressure to prevent overcooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reverse bootstrap air cycle machine uses only turbine and compressor without additional motor assistance, then the device complexity is reduced, but the cooling effectiveness is insufficient when RAM air pressure is below ambient pressure
Solution Approach 1:
The patent combines an electric motor with the turbine-compressor assembly, creating a hybrid system where the motor assists the turbine during ground operations (low RAM pressure) while the turbine drives the compressor during flight (high RAM pressure). This merging of power sources resolves the contradiction by ensuring reliable cooling across all operating conditions without requiring completely separate systems.
Solution Approach 2:
The system dynamically switches between motor-driven and turbine-driven modes based on operating conditions (ground vs. flight). The electronic controller monitors RAM air pressure and activates the motor only when needed, allowing the system to adapt its complexity to the operational requirements, thus maintaining reliability without permanent increase in device complexity.
2Productivity
If the reverse bootstrap air cycle machine operates continuously at maximum capacity, then the cooling output is maximized, but the energy consumption increases
Solution Approach 1:
The system applies partial action by using the electric motor only when and where needed (during ground operations when RAM pressure is insufficient), rather than continuously. The motor provides supplemental power only during the specific condition of low ambient pressure, reducing overall energy consumption while maintaining adequate cooling output.
Solution Approach 2:
During flight operations, the turbine automatically drives the compressor without external motor assistance, as the high RAM air pressure provides sufficient energy. The system serves itself using the available atmospheric pressure, eliminating the need for additional energy input during flight and reducing overall energy consumption.
3Reliability
If the system activates the electric motor to drive the compressor during high RAM air pressure, then the cooling output is enhanced, but the energy consumption increases unnecessarily
Solution Approach 1:
The electronic controller continuously monitors RAM air pressure and uses this feedback to determine when motor assistance is needed. When pressure is high (during flight), the controller keeps the motor inactive, allowing the turbine to handle the load alone. This feedback mechanism prevents unnecessary energy consumption by activating the motor only when pressure conditions warrant it.
Solution Approach 2:
The system extracts and utilizes the available RAM air pressure energy directly to drive the turbine-compressor system during flight, removing the need for supplemental motor power. By taking out and using the energy already present in the high-pressure RAM air, the system avoids unnecessary energy loss from motor operation.
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
Ensures reliable cooling of heat loads both in flight and on the ground by maintaining a pressure differential, enhancing the air cycle machine's effectiveness and reducing complexity compared to vapor cycle systems.
Implementation Method 1
RAM air may be first expanded to a sub-ambient pressure and cooled in the turbine
Implementation Method 2
The heat exchanger in this configuration is used to remove heat from another source
Implementation Method 3
The cooled air may then enter the compressor, where it is pressurized to a higher level
Implementation Method 4
The higher pressure air may then be cooled as it passes through a second heat exchanger which may also utilize ambient air to remove the heat of compression
Data Source
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AI summary
Disclosed is a cooling circuit for cooling a heat load in an aircraft system, having: a compressor (155); a turbine (135) connected to the compressor by a shaft (160), the turbine configured to drive the compressor via the shaft when RAM air pressure into a turbine inlet is above a first threshold; and a motor (170) connected to the shaft configured to drive the compressor when RAM air pressure at the turbine inlet is below the first threshold to cause the compressor to draw air into the turbine inlet, through the turbine, a heat exchanger (104) in fluid communication with the heat load (102), the compressor, and out of a compressor outlet.