Compound Engine APU for Aircraft Bleed Air
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Solution Overview
Problem
Existing aircraft auxiliary power units (APUs) are often heavy and complex, making them unsuitable for aircraft applications due to their weight and complexity, which are not compatible with the requirements of airborne systems.
Innovation Solution
A compound engine assembly is designed for use as an auxiliary power unit in aircraft, comprising an engine core with an internal combustion engine, a compressor, a bleed conduit for pneumatic systems, and a turbine section that compounds power with the engine core, along with a generator for electrical power, allowing for efficient provision of both compressed air and electrical power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If known ground-based APUs are used to provide pressurized air and shaft power, then the required functions are achieved, but the weight and complexity increase making them incompatible with aircraft applications
Solution Approach 1:
The patent combines the compressor and turbine into a single integrated compound engine assembly where the compressor compresses air that is then used by the internal combustion engine, and the turbine recovers energy from exhaust gases to drive the compressor. This merging of functions reduces overall system weight compared to separate ground-based APU components while maintaining the required pressurized air and power generation functions for aircraft applications
2Reliability
If known ground-based APUs are used to provide pressurized air and shaft power, then the required functions are achieved, but the complexity increases making them incompatible with aircraft applications
Solution Approach 1:
The compound engine assembly performs multiple functions within a single integrated system: the compressor provides pressurized air to the internal combustion engine, the engine generates shaft power, the turbine recovers exhaust energy to drive the compressor, and the system can provide both mechanical power and pressurized air output. This multi-functionality reduces the number of separate components needed compared to traditional ground-based APUs, thereby reducing overall system complexity for aircraft installation
3Power
If a turbine section is added to compound power with the engine core, then power generation efficiency is improved, but device complexity increases
Solution Approach 1:
The turbine section captures and converts the harmful waste heat and kinetic energy from the exhaust gases into useful mechanical work to drive the compressor. By converting what would otherwise be wasted energy (harmful exhaust flow) into beneficial compressor power, the system achieves improved overall power generation efficiency while the turbine-compressor integration keeps the added complexity manageable through shared mounting structures and common drive shafts
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 compound engine assembly provides a lightweight and efficient solution for aircraft APUs, enabling effective power generation and air supply while minimizing weight and complexity, thus addressing the compatibility issues of traditional APUs.
Implementation Method 1
an engine core including at least one internal combustion engine
Implementation Method 2
a generator in driving engagement with the common shaft to provide electrical power for the aircraft
Implementation Method 3
a compressor having an outlet in fluid communication with an inlet of the engine core
Implementation Method 4
a turbine section having an inlet in fluid communication with an outlet of the engine core, the turbine section configured to compound power with the engine core
Data Source
AI summary
A compound engine assembly for use as an auxiliary power unit for an aircraft and including an engine core with internal combustion engine(s), a compressor having an outlet in fluid communication with an engine core inlet, a bleed conduit in fluid communication with the compressor outlet through a bleed air valve, and a turbine section having an inlet in fluid communication with the engine core outlet and configured to compound power with the engine core. The turbine section may include a first stage turbine having an inlet in fluid communication with the engine core outlet and a second stage turbine having an inlet in fluid communication the first stage turbine outlet. A method of providing compressed air and electrical power to an aircraft is also discussed.