APU Compressor Health Diagnosis from Bleed Air Pressure
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Solution Overview
Problem
Current auxiliary power units (APUs) lack an effective means to distinguish between power turbine and engine compressor deterioration, limiting maintenance facilities' ability to tailor repair processes due to the limited number of sensors, which is essential for maintaining high functional reliability and simplicity.
Innovation Solution
A diagnostic system that includes a bleed air duct, a bleed air pressure sensor, and a processor to diagnose the health state of the power compressor based solely on sensed bleed air pressure, without adding additional sensors to the APU, by tracking pressure over time and generating alerts for predetermined pressure magnitudes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional sensors are added to the APU to monitor component health, then measurement precision and diagnostic capability are improved, but device complexity and cost increase
Solution Approach 1:
The patent uses bleed air pressure as an intermediary parameter to indirectly diagnose power compressor health. Instead of adding sensors directly to the power compressor, the system monitors pressure in the bleed air duct, which reflects compressor performance through the relationship between compressor output and pneumatic load requirements. This intermediary measurement approach provides diagnostic capability without direct contact with the critical component.
Solution Approach 2:
The system leverages existing APU operational parameters (bleed air pressure, rotational speed, pneumatic load conditions) to self-diagnose compressor health. The processor analyzes relationships between these existing parameters to detect degradation, allowing the system to monitor its own health state without requiring external diagnostic equipment or additional sensors.
2Ease of manufacture
If the APU is designed to be simple and lightweight with limited sensors, then ease of manufacture and reliability are improved, but the ability to accurately diagnose APU component health deteriorates
Solution Approach 1:
The patent segments the diagnostic function from the physical sensor placement. Instead of requiring sensors on every critical component, the system divides the diagnostic task into analyzing relationships between measurements taken at accessible locations (bleed air duct pressure) and known operational parameters (rotational speed, load conditions). This segmentation allows comprehensive monitoring without sensor proliferation.
Solution Approach 2:
The bleed air pressure measurement serves multiple functions: it monitors pneumatic load supply, indicates compressor performance, and provides data for health trend analysis. By making this single measurement serve multiple diagnostic purposes, the system achieves comprehensive monitoring capability without adding specialized sensors for each function.
3Device complexity
If no additional sensors are added to the APU, then device complexity remains low, but the ability to distinguish between power turbine and engine compressor deterioration is lost
Solution Approach 1:
The system dynamically analyzes the relationship between bleed air pressure and APU operational conditions (rotational speed, pneumatic load). By examining how pressure responds to changing operating conditions, the system can distinguish between turbine deterioration (which affects overall power output) and compressor deterioration (which directly impacts compression ratio and bleed air pressure characteristics). This dynamic response analysis provides component-specific diagnostic information without additional sensors.
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 accurate diagnosis of power compressor health state, allowing for targeted maintenance without increasing sensor count, thereby improving maintenance efficiency and reliability of the APU.
Implementation Method 1
The bleed air pressure sensor is disposed in the bleed air duct and is configured to sense bleed air pressure and supply a bleed air pressure signal representative thereof
Data Source
AI summary
A system and method for diagnosing load compressor health state for an auxiliary power unit that includes a power compressor, a combustor, a power turbine, and a load compressor is provided. The auxiliary power unit is operated and bleed air is discharged from the load compressor at a bleed air pressure. Using a pressure sensor, the bleed air pressure discharged from the load compressor is sensed and supplied to a processor. In the processor, power compressor health state is diagnosed based solely on the sensed bleed air pressure.