Aircraft Auxiliary Power Unit Starting via Compressor
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Solution Overview
Problem
Aircraft auxiliary power units face difficulties in starting at high altitudes due to low air density and temperature, requiring long and costly development phases, and a narrow starting window, making it challenging to maintain efficient and reliable operation.
Innovation Solution
A system that includes a positive-displacement compressor to supply compressed air for starting the auxiliary power unit, transitioning to a mixed supply with ambient air, and eventually relying solely on ambient air, utilizing a volumetric compressor and starter generator to ensure effective and controlled starting, even at high altitudes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the auxiliary power unit is started at very high altitude (43,000-45,000 ft), then the aircraft can operate at higher altitudes, but the starting becomes difficult and requires long development phases due to low air density and temperature
Solution Approach 1:
A volumetric compressor is introduced as an intermediary device between the ambient air and the auxiliary power unit. The compressor supplies pre-compressed air to the APU starter, mediating the interaction between the low-density ambient air and the APU's starting requirements. This allows the APU to start reliably at high altitudes by providing the necessary air density and pressure without requiring changes to the APU itself.
Solution Approach 2:
The system changes the physical parameters of the air supplied to the APU by compressing it. The volumetric compressor increases the air pressure and density before it enters the APU starter, transforming the low-density ambient air into a suitable starting medium. This parameter change enables reliable starting at altitudes where ambient air is too thin and cold.
2Ease of operation
If a volumetric compressor is used to supply compressed air for starting, then the starting process becomes effective and controlled, but the device complexity increases
Solution Approach 1:
The volumetric compressor is designed to serve multiple functions: it compresses air for APU starting, can supply air during transitional phases, and integrates with the existing aircraft pneumatic system. By making the compressor multi-functional, the system reduces overall complexity compared to having separate dedicated systems for each function.
Solution Approach 2:
The system dynamically adjusts the air supply configuration based on operating conditions. During starting, the volumetric compressor supplies compressed air; during transitional phases, it works with ambient air; and during normal operation, it relies solely on ambient air. This dynamic adaptation allows the system to maintain simplicity by using the same component in different modes rather than requiring multiple fixed systems.
3Productivity
If the starting window is narrowed at higher altitudes, then the starting conditions become more restrictive, but the difficulty to detect and maintain the starting window increases
Solution Approach 1:
The system incorporates feedback mechanisms to monitor starting conditions and adjust the volumetric compressor operation accordingly. Sensors detect parameters such as air density, temperature, and pressure, and this information feeds back to the control system. The feedback loop enables real-time adjustment of the compressor's air supply to maintain optimal starting conditions within the narrow window, making detection and maintenance of the starting window automated and reliable.
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
Enables faster and less costly starting of the auxiliary power unit at high altitudes, improving reliability and reducing development costs by simulating lower altitudes and maintaining a stable starting window.
Implementation Method 1
supplying compressed air to the auxiliary power unit from a positive-displacement compressor
Implementation Method 2
an auxiliary power unit (APU) including a gas turbine
Implementation Method 3
designed to supply non-propulsive energy on the ground and in flight
Data Source
AI summary
The invention concerns a method for generating auxiliary power in an aircraft, comprising the step consisting of: starting up an auxiliary power unit (6) of the aircraft by supplying compressed air to the auxiliary power unit (6) from a supercharger (7), and transferring non-propulsive energy from the auxiliary power unit (6) to the aircraft. The invention also concerns a system (5) for generating auxiliary power in an aircraft and an aircraft implementing such a method.