Aircraft Pneumatic System Auxiliary Engine Bleed Segmentation
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Solution Overview
Problem
Current aircraft pneumatic systems are inefficient, particularly at low engine power conditions, as they require high-pressure cabin bleed air, leading to increased specific fuel consumption (SFC) and limited minimum thrust capabilities due to complex arrangements and excessive pressure requirements for environmental control systems (ECS).
Innovation Solution
The integration of a recuperated auxiliary gas turbine engine with a core compressor connected to the main gas turbine engine's bleed, allowing for efficient pressurized air supply across a wide range of engine conditions using waste cabin air, reducing reliance on high-pressure bleeds and optimizing ECS operation through variable turbine and bypass modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If high-pressure cabin bleed air is used to power the environmental control system, then sufficient pressure and flow are provided to the ECS, but specific fuel consumption increases and minimum thrust capability is limited
Solution Approach 1:
The system divides the bleed air supply into two separate sources: a high-pressure bleed offtake from the high-pressure compressor and a low-pressure bleed offtake from the low-pressure compressor. This segmentation allows the ECS to use low-pressure air when sufficient, avoiding the fuel penalty of high-pressure extraction, while still having high-pressure capability when needed for adequate ECS operation
Solution Approach 2:
The system dynamically switches between high-pressure and low-pressure bleed sources based on operating conditions. A control system monitors engine parameters and automatically selects the optimal bleed source, enabling the ECS to adapt to varying thrust levels and maintain efficiency across different flight regimes
2Stress or pressure
If the cabin bleed offtake is located at a relatively high pressure stage of the engine compressor, then sufficient pressure is provided to the ECS at low engine power, but system complexity increases and thrust specific fuel consumption increases
Solution Approach 1:
The bleed air system is segmented into multiple offtakes at different pressure stages along the compressor. This provides discrete pressure sources that can be selectively activated, simplifying the control logic compared to a single high-pressure offtake while avoiding the need for complex pressure regulation systems
Solution Approach 2:
The low-pressure bleed offtake serves dual purposes: it powers the ECS during normal operation and provides a simplified alternative to high-pressure extraction during low-thrust conditions, eliminating the need for separate low-pressure extraction systems
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 provides highly efficient pressurized air supply, reducing SFC and increasing operational flexibility, allowing for reliable ECS performance at varying altitudes and engine conditions while simplifying system complexity and reducing weight.
Implementation Method 1
a core compressor (42) of a recuperated auxiliary gas turbine engine having an inlet in fluid communication with a main compressor bleed of the main gas turbine engine
Implementation Method 2
The BAS system comprises a fan air heat exchanger which exchanges heat between relatively cool fan air provided by a fan air duct, and the relatively hot cabin bleed air provided from the engine compressor
Data Source
AI summary
An aircraft pneumatic system includes a main gas turbine engine including a main compressor, a recuperated auxiliary gas turbine engine including a core compressor having an inlet in fluid communication with a main compressor bleed of the main gas turbine engine and an environmental control system inlet in fluid communication with the main compressor bleed of the main gas turbine engine. The environmental control system includes a compressor driveable by power provided by the auxiliary gas turbine engine.