Aircraft APU with Electrically Driven Compressor
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Solution Overview
Problem
Auxiliary power units in aircraft face inefficiencies due to components being sized for peak loads, leading to suboptimal operation at average loads, and geometric constraints limiting compressor and turbine configurations, compromising aerodynamic efficiency.
Innovation Solution
An auxiliary power unit design featuring a rotary intermittent internal combustion engine with a turbine and compressor that can operate independently, driven by an electric motor and transfer generator, allowing for optimal speed operation and flexible positioning, and including a method for power transfer between components to manage load variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If components are sized to accommodate peak loads, then the auxiliary power unit can meet maximum demand requirements, but components do not operate efficiently during average load operation
Solution Approach 1:
The patent applies dynamics by making the compressor and turbine independently variable in speed through separate drive systems. The compressor can be driven by an electric motor at speeds optimized for average loads, while the turbine operates independently at speeds optimized for peak loads or power generation. This dynamic independence allows each component to operate at its optimal speed regardless of whether the system is experiencing peak or average demand conditions.
Solution Approach 2:
The patent implements parameter changes by allowing the compressor speed and turbine speed to be independently controlled and adjusted. The compressor speed can be varied to match average load requirements, while the turbine speed can be adjusted for peak power generation needs. This independent parameter control enables the system to optimize efficiency at average loads while maintaining the capability to meet peak demand requirements.
2Device complexity
If the compressor is positioned in proximity to mechanically connected components, then mechanical connections are simplified, but the auxiliary power unit configuration is limited and aerodynamic efficiency is compromised
Solution Approach 1:
The patent applies mechanics substitution by replacing the traditional mechanical connection between the compressor and turbine with an electrical connection system. The compressor is driven by an electric motor that receives power from the turbine through a generator and electrical transmission system. This substitution eliminates the need for direct mechanical coupling, allowing the compressor to be positioned independently from the turbine without requiring complex shafts, gears, or other mechanical transmission components.
Solution Approach 2:
The patent uses an electrical power transmission system as an intermediary between the turbine and compressor. The turbine drives a generator that produces electrical power, which is then transmitted through electrical conductors to drive the compressor motor. This intermediary electrical system allows the compressor and turbine to be spatially separated while maintaining functional connectivity, enabling flexible positioning for optimal aerodynamic efficiency.
3Power
If the compressor and turbine are mechanically connected, then power transfer is direct, but one or both components cannot operate at optimal speeds
Solution Approach 1:
The patent applies dynamics by enabling independent speed control of the compressor and turbine through separate drive systems. The turbine can rotate at speeds optimized for power generation, while the compressor can be driven by an electric motor at speeds optimized for its aerodynamic performance. This dynamic independence allows each component to operate at its optimal speed without being constrained by a fixed mechanical connection that would require both to rotate at the same speed.
Solution Approach 2:
The patent applies segmentation by dividing the power transmission system into separate functional segments: the turbine segment for power generation, the electrical generation and transmission segment, and the compressor drive segment. This segmentation allows each component to operate independently at its optimal speed while maintaining overall system power transfer efficiency through the electrical connection medium.
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 design enables efficient operation at average loads, reduces fuel consumption, emissions, and noise by allowing components to operate at optimal speeds, and provides flexibility in unit configuration and positioning, improving overall efficiency and performance.
Implementation Method 1
an electric motor drivingly engaged to the compressor
Implementation Method 2
a turbine having an inlet in fluid communication with an outlet of the engine
Implementation Method 3
a transfer generator drivingly engaged to the engine, the transfer generator and the electric motor being electrically connected to allow power transfer therebetween
Implementation Method 4
an engine configured as a rotary intermittent internal combustion engine
Data Source
AI summary
An auxiliary power unit for an aircraft includes a rotary intermittent internal combustion engine, a turbine having an inlet in fluid communication with an outlet of the engine, the turbine compounded with the engine, a compressor having an inlet in fluid communication with an environment of the aircraft and an outlet in fluid communication with the aircraft, the compressor rotatable independently of the turbine, an electric motor drivingly engaged to the compressor, and a transfer generator drivingly engaged to the engine, the transfer generator and the electric motor being electrically connected to allow power transfer therebetween. The compressor or an additional compressor may be in fluid communication with the inlet of the engine. A method of operating an auxiliary power unit of an aircraft is also discussed.