Variable Displacement Pump Dry-Out for Low-Power Aircraft Fuel Systems
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Solution Overview
Problem
Modern aircraft designs face challenges in reducing horsepower extraction from fuel systems, particularly with single engine aircraft, due to the inefficiency of centrifugal main pumps at low power conditions, which struggle to meet thermal management requirements.
Innovation Solution
A fuel system incorporating a variable displacement pump sub-system (VDPP) and a main fuel pump sub-system (MFP) with a centrifugal pump, featuring a dry-out system using an ejector to minimize horsepower extraction by shutting down the centrifugal pump during low power conditions, supplemented by a boost pump and positive displacement pump for efficient fuel delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a centrifugal main pump is used for fuel delivery, then reliability is improved, but horsepower extraction increases and thermal management performance deteriorates at low power conditions
Solution Approach 1:
The patent applies a variable displacement pump instead of a fixed displacement centrifugal pump, allowing the pump to dynamically adjust its displacement based on actual fuel demand. This enables the pump to operate efficiently across a wide range of power conditions, reducing horsepower extraction at low power conditions while maintaining reliability through continuous operation capability.
Solution Approach 2:
The patent changes the operational parameters of the fuel pump system by implementing a variable displacement mechanism that adjusts pump output based on system requirements. This allows optimization of horsepower extraction across different flight conditions while maintaining adequate fuel delivery and thermal management performance.
2Productivity
If a centrifugal main pump operates continuously, then fuel delivery is maintained, but horsepower extraction increases and efficiency decreases at low power conditions
Solution Approach 1:
The variable displacement pump dynamically adjusts its displacement to match actual fuel demand, allowing the system to maintain continuous fuel delivery capability while optimizing energy efficiency. The pump can reduce its displacement at low power conditions, minimizing energy loss while ensuring adequate fuel supply.
Solution Approach 2:
The patent implements parameter changes by allowing the pump displacement to vary based on system needs, optimizing the balance between fuel delivery capability and energy efficiency across different operating conditions.
3Use of energy by moving object
If a variable displacement pump is used, then horsepower extraction is reduced, but device complexity increases
Solution Approach 1:
The variable displacement pump incorporates dynamic adjustment mechanisms that allow the system to optimize horsepower extraction. While this increases device complexity, the patent integrates these mechanisms into the existing fuel system architecture, balancing the trade-off between energy efficiency and system complexity.
4Use of energy by moving object
If the centrifugal pump is shut down during low power conditions, then horsepower extraction is reduced, but fuel delivery continuity may be affected
Solution Approach 1:
The variable displacement pump allows the system to dynamically adjust pump operation rather than completely shutting down. This maintains fuel delivery continuity through controlled operation at reduced displacement, while still achieving significant horsepower extraction reduction at low power conditions.
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 system reduces fuel pump horsepower extraction and improves efficiency by allowing the centrifugal pump to be turned off during low power operations, while maintaining fuel delivery through the VDPP, thus enhancing thermal management and reducing oscillatory behavior.
Implementation Method 1
An ejector can have a drain inlet connected to in fluid communication with a branch of the main outlet line that is upstream of the SCV, an ejection inlet connected in fluid communication with a return line from the MFTV, and an outlet connected in fluid communication with a return line configured to be connected to an inlet of a boost pump. The ejector can be configured to drain the centrifugal pump using flow from the VDPP through the MFTV.
Data Source
AI summary
A fuel system a main fuel pump sub-system (MFP) with an inlet for receiving a supply of fuel from an inlet line. The MFP has a main outlet line configured to supply fuel to a main fuel throttle valve assembly (MFTV), and a cross-over outlet line. A variable displacement pump sub-system (VDPP) has a first inlet connected in fluid communication with the cross-over outlet line, a second inlet connected to a branch of the main outlet line, a first outlet line configured to connect to supply fuel to the MFTV, and a second outlet line configured to connect to supply fuel to an actuation system.