Aircraft Fuel Pump Actuation With Dahlander Speed Switching
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Solution Overview
Problem
Existing fuel pump actuating devices for aircraft engines result in excessive fuel flow rates at low engine speeds, necessitating fuel recirculation and heat dissipation, which is detrimental to the oil circuit and increases the size of exchangers.
Innovation Solution
An actuating device with an asynchronous motor rotating electric machine and a generator, utilizing Dahlander coupling and an electrical connection member to connect windings in series or parallel based on engine speed, allowing proportional rotational speeds to match fuel demand, reducing the discrepancy between required and supplied fuel flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the pump displacement is sized to meet the highest fuel flow requirement at low engine speed, then the fuel flow rate requirement is satisfied at all operating points, but the pump supplies excessive fuel flow at high engine speed requiring recirculation
Solution Approach 1:
The motor rotating electric machine uses Dahlander coupling with two stators that can be connected in series or parallel configurations. This dynamic reconfiguration allows the motor to operate at two different speeds: a first speed when stators are in series (for low engine speed operation) and a second speed when stators are in parallel (for high engine speed operation). This dynamic speed adjustment enables the pump to match fuel delivery to actual engine demand across different operating conditions, eliminating the need for recirculation at high speeds
Solution Approach 2:
The invention changes the operational parameters of the motor by altering the electrical connection configuration of the two stators. By switching between series and parallel connections, the motor's rotational speed parameter is adjusted to match different engine operating conditions. This parameter change allows the system to adapt the pump output to the actual fuel flow requirement at each operating point, preventing excessive fuel delivery and the associated energy losses
2Quantity of substance
If a fuel recirculation device is installed to handle excess fuel flow, then the fuel flow rate match is improved, but mechanical power is drawn from the engine and heat dissipation increases the size of exchangers
Solution Approach 1:
The Dahlander coupling motor provides dynamic speed adjustment capability, allowing the pump to be directly driven at the appropriate speed to match fuel demand. This eliminates the static recirculation device and its associated complexity by using dynamic motor control instead of mechanical recirculation hardware
Solution Approach 2:
The invention extracts and eliminates the recirculation device from the system by using the dual-speed motor to directly address the root cause of excess fuel flow. Instead of adding a recirculation path to handle surplus fuel, the system reconfigures the motor to prevent surplus fuel generation in the first place
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
Significantly reduces the need for fuel recirculation and heat dissipation, optimizing fuel supply to the engine by minimizing excess fuel flow, thereby reducing the size of exchangers and improving energy efficiency.
Implementation Method 1
an asynchronous motor rotating electric machine (24), and a generator rotating electric machine (26)
Implementation Method 2
the generator rotating electric machine (26) delivering electrical energy to the motor rotating electric machine (24)
Data Source
AI summary
An actuating device of a fuel pump for an aircraft engine includes: a motor, a generator and an electrical connection member, the motor being an asynchronous machine with Dahlander coupling including a first rotor coupled to the pump for actuation thereof, and a first stator including at least one input phase, each input phase comprising two windings, the generator including a second rotor mechanically coupled to a shaft of the engine, and a second stator including at least one output phase, the electrical connection member being configured so as to connect each output phase to an input phase, and to connect the windings of each input phase in series or in parallel according to a speed of the engine.