Two-Pass Heat Exchanger Recirculation for Aircraft Cabin Pressurization
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Solution Overview
Problem
Current aircraft air conditioning systems rely on high engine bleed pressures for cabin pressurization and cooling, which are inefficient in terms of engine fuel burn, especially as the aerospace industry moves towards more efficient aircraft designs.
Innovation Solution
An environmental control system utilizing a two-pass heat exchanger with a quench loop and recirculation of air between the passes, leveraging lower pressure engine bleed air to achieve cabin pressurization and cooling while minimizing fuel burn, incorporating a compressing device and heat exchanger configuration that recirculates air to manage pressure and temperature effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high engine bleed pressures are used for cabin pressurization and cooling, then effective temperature and pressure conditions are maintained, but engine fuel burn efficiency deteriorates
Solution Approach 1:
The heat exchanger is divided into two separate passes: a first pass for heating air using engine bleed air, and a second pass for cooling air using ambient air. This segmentation allows independent optimization of each thermal process, enabling the system to use lower pressure bleed air while still achieving effective cabin temperature control.
Solution Approach 2:
The first pass pre-heats the air using lower pressure engine bleed air before it enters the compressor. This preliminary heating action reduces the work required by the compressor to achieve the desired cabin pressure and temperature, thereby improving overall system efficiency and reducing fuel consumption.
2Use of energy by moving object
If lower pressure engine bleed air is used, then engine fuel burn efficiency improves, but cabin pressurization and cooling effectiveness deteriorates
Solution Approach 1:
The two-pass heat exchanger acts as an intermediary device that facilitates heat transfer between engine bleed air and cabin air in a controlled manner. The first pass uses lower pressure bleed air to pre-heat air, while the second pass uses ambient air for cooling, thereby maintaining cabin effectiveness while enabling the use of lower pressure (more efficient) engine bleed air.
Solution Approach 2:
The system changes the thermal parameters of the air stream by implementing sequential heating and cooling in two distinct passes. This parameter transformation allows the system to effectively utilize lower pressure bleed air by adjusting the temperature profile of the air before compression, thereby maintaining cabin pressurization and cooling effectiveness while improving fuel efficiency.
3Use of energy by moving object
If a two-pass heat exchanger with recirculation is implemented, then fuel burn efficiency improves, but device complexity increases
Solution Approach 1:
The system merges the heating and cooling functions into a single integrated two-pass heat exchanger unit with recirculation capability. By combining these functions in one device rather than separate systems, the patent achieves improved fuel efficiency while limiting the increase in overall system complexity through functional integration.
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
This configuration enhances engine fuel burn efficiency by utilizing lower pressure engine bleed air for cabin pressurization and cooling, reducing fuel consumption while maintaining effective temperature and pressure conditions within the aircraft cabin.
Implementation Method 1
a second heat exchanger downstream of the compressor and downstream of a turbine, the second heat exchanger having a first side and a second side, the first side of the second heat exchanger in fluid communication with the compressor and the second side of the second heat exchanger in fluid communication with the turbine
Implementation Method 2
a compressing device comprising a compressor
Implementation Method 3
an air cycle machine comprising an inlet, a compressing device in communication with the inlet, a first heat exchanger downstream of the compressor, a turbine downstream of the first heat exchanger
Data Source
AI summary
A system of an aircraft includes an inlet arranged in fluid communication with a bleed air source such that the inlet is configured to receive a flow of bleed air. A compressing device includes a compressor having a compressor inlet fluidly connected to the inlet. A heat exchanger is fluidly coupled to an outlet of the compressor. The heat exchanger includes a first pass and a second pass, both of which are located downstream from the compressor. An outlet of the first pass is directly connected to an inlet of the second pass via a first conduit. The outlet of the first pass is also fluidly connected to an inlet of the compressor via a second conduit such that a portion of the bleed air output from the first pass is returned to the compressor inlet via the second conduit.