Variable Speed Multi-Stage Pump for Aircraft Fuel Systems
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Solution Overview
Problem
Existing gear driven fuel pumps for aircraft often pump excess fuel under lower demand conditions, leading to fuel heating and potential varnish or coking within the fuel system.
Innovation Solution
A multi-stage gear pump system incorporating a variable speed gearbox that adjusts the rotational speed of the pump stages based on fuel demand, preventing excess fuel pumping and reducing fuel heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fuel pumps are designed to provide desired fuel under peak demand conditions, then fuel delivery capability is improved, but excess fuel flow is pumped under lower demand conditions causing fuel heating
Solution Approach 1:
The patent applies a variable speed drive system that dynamically adjusts the rotational speed of the pump according to actual fuel demand. The controller receives signals from flow demand sensors and modulates the motor speed accordingly, allowing the pump to deliver full capacity during peak demand while reducing speed during lower demand to prevent excess fuel pumping and associated heating.
Solution Approach 2:
The system changes the operating parameters of the pump by varying rotational speed based on demand conditions. The variable speed drive enables continuous adjustment of pump speed across a wide range, optimizing fuel delivery at each operating point and preventing the pump from operating at constant high speed that causes overheating during partial load conditions.
2Device complexity
If a single pump stage is used, then device complexity is reduced, but excess fuel pumping cannot be controlled under varying demand conditions
Solution Approach 1:
The patent employs a multi-stage pump configuration where the fuel pumping function is divided into multiple stages with different capacities. Each stage can be independently controlled or selectively engaged, allowing the system to match pump output to actual demand more precisely. This segmentation enables better adaptability without requiring a completely complex system redesign.
Solution Approach 2:
The variable speed drive system provides multi-functionality by enabling a single pump configuration to serve multiple operating conditions. The same pump hardware can operate across a wide range of speeds to meet varying fuel demands, eliminating the need for multiple dedicated pump systems while maintaining adaptability to different flight conditions.
3Productivity
If pump speed is increased to meet peak demand, then fuel delivery is improved, but fuel heating increases under all operating conditions
Solution Approach 1:
The system incorporates feedback control through flow demand sensors and a controller that continuously monitors actual fuel requirements. The controller adjusts pump speed in real-time based on this feedback, ensuring the pump operates at the minimum necessary speed to meet demand. This prevents energy waste from pumping excess fuel at high speeds during partial load conditions while maintaining adequate delivery during peak demand.
Data Source
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AI summary
A multi-stage gear pump includes a first pump stage (102), a second pump stage (104), and a variable speed gearbox (110) including an input and an output, wherein the input is rotationally coupled to the first pump stage and the input rotates at a first rotational speed, and the output is rotationally coupled to the second pump stage and rotates at a second rotational speed, wherein a variable gear ratio determines the second rotational speed relative to the first rotational speed.