APU Oil Quantity Indication Across Startup and Shutdown Gulps
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Solution Overview
Problem
Existing aircraft auxiliary power unit (APU) systems face challenges in accurately determining and indicating oil quantity while the APU is running, particularly due to inadequate accounting for startup and shutdown 'gulps,' which requires shutdown of the APU for measurement, increasing maintenance time and inconvenience.
Innovation Solution
A fluid quantity indication system that determines and displays accurate oil quantity by establishing gulp values during startup, operation, and shutdown phases, using a controller to combine raw fluid quantity values with gulp values to provide a stable and consistent indication, allowing for accurate oil quantity measurement without shutting down the APU.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the APU is shut down to acquire consistent oil quantity measurement, then measurement precision is improved, but loss of time and productivity worsen due to increased maintenance time and inconvenience
Solution Approach 1:
The system performs preliminary actions by establishing gulp values during startup, operation, and shutdown phases in advance. These gulp values are stored and later used to compensate for oil quantity measurements taken during any phase, eliminating the need to wait for shutdown conditions to achieve accurate measurements.
Solution Approach 2:
The system changes the measurement approach by introducing phase-dependent gulp value parameters. Instead of requiring a specific system state (shutdown) for accurate measurement, the system applies different gulp compensation parameters based on the operational phase, enabling accurate measurements across all phases including startup and operation.
2Measurement precision
If the APU is shut down for oil quantity measurement, then measurement precision is improved, but ease of operation worsens due to inconvenience of restart procedures
Solution Approach 1:
The system performs preliminary actions by establishing gulp values during startup, operation, and shutdown phases in advance. These gulp values are stored and later used to compensate for oil quantity measurements taken during any phase, eliminating the need to wait for shutdown conditions to achieve accurate measurements.
Solution Approach 2:
The system provides self-service by automatically compensating for gulp effects using stored gulp values and phase identification. The controller automatically selects the appropriate gulp value based on the current operational phase and applies it to the raw sensor signal, eliminating the need for operator intervention or system shutdown.
3Stability of the object's composition
If gulp values are established for all phases (startup, operation, shutdown), then stability of indication is improved during transients, but device complexity increases
Solution Approach 1:
The system performs preliminary actions by establishing gulp values during startup, operation, and shutdown phases in advance. These gulp values are stored and later used to compensate for oil quantity measurements taken during any phase, eliminating the need to wait for shutdown conditions to achieve accurate measurements.
Solution Approach 2:
The system uses feedback by continuously monitoring the operational phase and automatically selecting the appropriate gulp value for compensation. The controller receives feedback about the current phase (startup, operation, or shutdown) and adjusts the indicated oil quantity accordingly, maintaining stability throughout transitions.
Data Source
AI summary
An auxiliary power unit (APU) oil quantity indication system and method provides a stable and accurate oil quantity indication during startup, mission duration and shutdown. The system determines a gulp value at various stages of operation, which is combined with a raw oil quantity indication to provide an indicated oil quantity.