Aircraft APU Excess Air Recovery Duct
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Solution Overview
Problem
Existing aircraft auxiliary power units (APUs) are often heavy and complex, making them unsuitable for use in aircraft applications due to their weight and complexity, which complicates their integration as alternative power sources when main engines are shut down.
Innovation Solution
A compound engine assembly for aircraft APUs, comprising an engine core, a compressor, a turbine section, and an excess air duct that defines a flow path between the compressor and turbine section separate from the engine core, allowing for efficient provision of compressed air and electrical power, with a Wankel engine configuration for high cycle efficiency and reduced weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If known ground-based APU configurations are used, then power provision capability is achieved, but weight and device complexity increase making them incompatible with aircraft applications
Solution Approach 1:
The patent combines the compressor outlet flow into a single integrated system that serves dual purposes: feeding the engine core and providing excess air to the turbine. This merging of functions into a unified flow path eliminates the need for separate heavy ground-based APU configurations, achieving power provision while reducing weight for aircraft compatibility
2Power
If known ground-based APU configurations are used, then power provision capability is achieved, but device complexity increases making them incompatible with aircraft applications
Solution Approach 1:
The excess air duct is designed to perform multiple functions simultaneously: it transports compressed air from the compressor outlet to the turbine, provides excess air for power generation, and integrates with the engine core flow path. This multi-functionality reduces the number of separate components needed, thereby reducing device complexity while maintaining power provision capability
Solution Approach 2:
The patent segments the air flow into two distinct paths within a unified system: one path through the engine core and another through the excess air duct to the turbine. This segmentation allows independent optimization of each flow path while maintaining overall system simplicity, reducing complexity compared to integrated ground-based configurations
3Device complexity
If excess air is not recovered and used, then system simplicity is maintained, but energy efficiency and power density are reduced
Solution Approach 1:
The patent converts what would normally be wasted excess compressed air into a useful resource by directing it through the excess air duct to the turbine. This transforms a potential inefficiency into a beneficial power source, improving energy efficiency and power density while maintaining system simplicity through the straightforward duct integration
4Use of energy by moving object
If a separate flow path for excess air is implemented, then energy recovery and power density are improved, but device complexity may increase
Solution Approach 1:
The separate flow path for excess air is merged with the existing engine core flow path at the compressor outlet and turbine inlet. This integration allows energy recovery through the excess air duct while utilizing the existing structural framework of the engine, thereby improving energy recovery without proportionally increasing device complexity
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 enables a lightweight and efficient auxiliary power unit that can provide both compressed air and electrical power to aircraft systems, reducing weight and complexity while maintaining high efficiency and power density, suitable for aircraft use.
Implementation Method 1
a compressor (18) having an outlet (18o) in fluid communication with an inlet (12i) of an engine core (12)
Implementation Method 2
an engine core (12) having an inlet (12i) in fluid communication with an outlet (18o) of the compressor (18), and having an outlet (12o)
Implementation Method 3
a turbine section (20) compounding power with the engine core (12) and in driving engagement with the compressor (18)
Data Source
AI summary
An auxiliary power unit for an aircraft, having an engine core, a compressor having an outlet in fluid communication with the engine core inlet, a turbine section in fluid communication with the engine core outlet, and an excess air duct having a first end in fluid communication with the compressor outlet and a second end in fluid communication with a turbine inlet of the turbine section. The excess air duct defines a flow path between the compressor outlet and the turbine section separate from the engine core. The auxiliary power unit may include a generator in driving engagement with the engine core to provide electrical power for the aircraft. A method of providing compressed air and electrical power to an aircraft is also discussed.