Variable Speed Drive System for Aircraft Pump Efficiency
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Solution Overview
Problem
Existing aircraft pumps face inefficiencies due to constant gear ratio-driven input rotary speed, leading to weight and cost penalties in achieving variable displacement, and alternators or generators operate suboptimally with varying engine speeds.
Innovation Solution
An electronically controlled variable speed drive system using a compound planetary gear set, motor, and electronic controller allows independent control of pump rotary speed and alternator/generator operation, transforming fixed displacement pumps into variable displacement pumps and maintaining optimal efficiency across varying conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If variable displacement pumps are used to improve pump thermal efficiency, then pump efficiency is improved, but weight and cost increase
Solution Approach 1:
The patent applies a variable speed drive system with a compound planetary gear set that dynamically adjusts the gear ratio between 1:1 and maximum gear ratio determined by the number of teeth on the gears. This allows a fixed displacement pump to operate at variable speeds, achieving variable displacement effect without the weight penalty of a true variable displacement pump. The motor applies electronically controlled retarding torque to continuously vary the gear ratio, enabling the pump to match flow demand while maintaining reasonable weight.
Solution Approach 2:
The patent replaces the mechanical variable displacement mechanism (such as variable stroke pistons or vanes) with an electrical control system consisting of a motor and electronic controller. The motor applies retarding torque to the compound planetary gear set, and the electronic controller adjusts the torque to achieve desired pump speeds. This substitution of mechanical variable displacement with electrical speed control reduces weight while maintaining pump efficiency benefits.
2Loss of energy
If variable displacement pumps are used to improve pump thermal efficiency, then pump efficiency is improved, but cost increases
Solution Approach 1:
The patent uses a variable speed drive system that dynamically adjusts the gear ratio between 1:1 and maximum gear ratio determined by the number of teeth on the gears. This allows a fixed displacement pump to operate at variable speeds, achieving variable displacement effect without the high cost of a true variable displacement pump. The motor applies electronically controlled retarding torque to continuously vary the gear ratio, enabling the pump to match flow demand while maintaining cost-effectiveness.
Solution Approach 2:
The patent replaces the expensive mechanical variable displacement mechanism with a more cost-effective electrical control system. The motor and electronic controller provide variable speed control at lower cost than redesigning the pump itself as a variable displacement type. This substitution maintains pump efficiency benefits while reducing manufacturing cost.
3Device complexity
If a constant gear ratio is used in the accessory drive gearbox, then the system is simple, but the pump input rotary speed is directly related to engine spool speed and cannot be optimized
Solution Approach 1:
The patent introduces a variable speed drive system with a compound planetary gear set that dynamically adjusts the gear ratio between 1:1 and maximum gear ratio determined by the number of teeth on the gears. This allows the pump speed to be independently controlled from engine speed. The motor applies electronically controlled retarding torque to continuously vary the gear ratio, enabling the pump to operate at optimal speeds for different flight conditions while the engine operates independently.
Solution Approach 2:
The patent creates a multi-functional system where the variable speed drive can simultaneously optimize pump operation and alternator/generator operation. The system can decouple pump speed from engine speed while also maintaining alternator/generator at its best efficiency speed. This universal solution addresses multiple problems with a single integrated system.
4Device complexity
If the pump speed is coupled to engine spool speed, then the system is simple, but the alternator or generator cannot operate at its best efficiency speed
Solution Approach 1:
The patent creates a multi-functional variable speed drive system that can simultaneously optimize both pump operation and alternator/generator operation. The system decouples the output speed from the input drive speed, allowing the alternator/generator to operate at its best efficiency speed regardless of engine speed. The electronic controller manages both functions, making the system universally applicable to both pump and electrical power generation needs.
Solution Approach 2:
The patent introduces a variable speed drive system with a compound planetary gear set that dynamically adjusts the gear ratio. This allows independent speed control for different outputs, enabling the alternator/generator to operate at optimal speed while the engine operates at whatever speed is required for propulsion. The motor applies electronically controlled retarding torque to achieve the desired speed decoupling.
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 efficient flow delivery and reduced weight and cost by allowing independent pump speed control, matching fluid displacement to demand and maintaining optimal alternator/generator efficiency regardless of engine speed.
Implementation Method 1
An electronically controlled variable speed drive consists of a compound planetary gear set, a motor, and an electronic controller. The drive is driven by an external power source, such as an aircraft engine, and depending on the application, it may contain either one or two output drive shafts.
Implementation Method 2
The variable speed drive is capable of continuously varying the gear ratio within a compound planetary gear set by applying an electronically controlled retarding torque to a motor.
Data Source
AI summary
An electronically controlled variable speed mechanical drive to be used in high power applications where using a direct drive motor is not feasible due to weight and size constraints. The variable speed drive components convert an externally driven fixed displacement pump into a variable displacement pump by electronically setting the pump speed to meet flow demands. A single stage pump and a multi-stage pump are so converted, according to the present disclosure.