Aircraft Fuel Pump Actuation With Speed-Switched Motor-Generator Drive
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Solution Overview
Problem
Existing pump actuating devices in aircraft fuel systems require oversized pumps to ensure adequate fuel flow across varying engine speeds, leading to excessive fuel recirculation and heat dissipation issues.
Innovation Solution
A fuel actuating device comprising a motor and generator rotating electric machines, an electrical energy inverter, a switching member, and a control member that selectively connects the motor to the generator or inverter based on engine speed, optimizing pump sizing and operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pump is dimensioned to meet the highest fuel flow rate requirement at low engine speeds, then the fuel flow rate supplied is sufficient across all operating points, but the fuel flow rate supplied exceeds the required flow rate at high engine speeds, necessitating fuel recirculation
Solution Approach 1:
The pump actuating device uses a rotating electric machine (motor or generator) to dynamically adjust the pump's rotational speed according to engine speed requirements. This enables the pump to deliver variable fuel flow rates that precisely match the engine's needs across different operating conditions, eliminating the need for oversized pumps and fuel recirculation systems
Solution Approach 2:
The system changes the operational parameters by using electrical control to vary the pump's rotational speed based on engine speed feedback. This allows continuous adjustment of fuel flow rate to match varying engine demands, resolving the contradiction between ensuring sufficient fuel supply at all speeds and avoiding excessive fuel delivery that requires recirculation
2Reliability
If a fuel recirculation device is installed to handle excess fuel flow, then the fuel supply adequacy is maintained, but mechanical power is drawn from the engine and dissipated as heat, impacting the cooling system
Solution Approach 1:
The invention extracts and eliminates the harmful fuel recirculation loop from the system. By using a dynamically controlled pump actuating device, the system directly supplies the precise amount of fuel needed without generating excess fuel flow, thereby removing the source of harmful heat dissipation and its negative impact on the aircraft's cooling system
3Device complexity
If a mechanically coupled pump system is used without electrical control, then the system complexity is reduced, but the discrepancy between required and supplied fuel flow rates increases across varying engine speeds
Solution Approach 1:
The invention replaces the direct mechanical coupling between the engine and pump with an electrically controlled actuating system. A rotating electric machine (motor or generator) coupled to the pump allows precise electrical control of pump speed, enabling accurate matching of fuel flow rate to engine requirements while reducing the mechanical complexity of direct drive systems with fixed displacement pumps
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
This solution reduces the discrepancy between required and supplied fuel flow rates, minimizing the need for fuel recirculation and associated heat dissipation, thereby improving system efficiency and reducing heat impact on other aircraft systems.
Implementation Method 1
a rotating electric machine, in particular an asynchronous machine, designated by the generic term 'motor' (24)
Implementation Method 2
a generator (26) whose shaft is coupled to a shaft (37) of the engine (18) forming a drive shaft
Data Source
AI summary
An actuating device of a pump of a fuel pumping system of an engine, including a motor, a generator, an inverter, a switching member and a control member, the motor including a first rotor coupled to the pump and a first stator including at least one input stator winding, the generator including a second rotor coupled to a drive shaft of the engine, and a second stator including at least one output stator winding, the control member being configured to control the switching member in order to selectively connect each input stator winding: to a corresponding output stator winding if a speed of the engine is higher than or equal to a predetermined speed; to a corresponding output of the inverter, otherwise.