Fuel Pump Epicyclic Drive for Variable Turbomachine Flow
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Solution Overview
Problem
The existing fuel supply circuit in turbomachines, particularly in aircraft, faces inefficiencies due to excess fuel flow regulation issues, leading to increased power draw and thermal dissipation, which complicates the design and mass of the fuel circuit, especially in heat exchangers, and necessitates a recirculation loop to manage surplus fuel.
Innovation Solution
A transmission device with an epicyclic gear train and reversible electrical power transfer between motors is used to adapt the pump speed to match fuel flow requirements, ensuring minimum power consumption and eliminating the need for external power, allowing the pump to operate efficiently across varying turbomachine speeds without excess fuel injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the pump displacement is increased to ensure sufficient fuel flow at low speed ignition, then the fuel flow requirement at ignition is met, but the pump delivers excess fuel flow during cruise flight, requiring a recirculation loop and increasing power consumption
Solution Approach 1:
The patent applies a variable displacement pump mechanism that allows the pump displacement to be dynamically adjusted according to operating conditions. The pump displacement is varied as a function of turbomachine speed to match fuel flow demand, eliminating the need for a fixed high displacement setting that would cause excess flow during cruise. This dynamic adjustment resolves the contradiction by enabling the pump to deliver appropriate fuel quantities across the entire operating range without continuous recirculation.
Solution Approach 2:
The invention changes the displacement parameter of the pump based on operating conditions. By varying the displacement parameter as a function of turbomachine speed, the system optimizes fuel flow delivery at each operating point. This parameter change approach allows the pump to operate efficiently at both low speed ignition (high displacement) and cruise flight (low displacement), eliminating the energy loss associated with delivering excess fuel during cruise.
2Quantity of substance
If the pump is dimensioned for sufficient flow at all speeds, then fuel flow is adequate during all flight conditions, but the recirculation loop increases in size and mass to handle excess fuel
Solution Approach 1:
The variable displacement pump eliminates the need for a large recirculation loop by dynamically matching fuel delivery to actual demand. Since the pump displacement is adjusted according to operating conditions, excess fuel generation is minimized, allowing the recirculation loop to be significantly reduced in size and mass while still handling transient fuel flow requirements.
3Weight of moving object
If the pump displacement is optimized for minimum mass, then the pump size is reduced, but the fuel flow becomes insufficient at certain operating speeds
Solution Approach 1:
The variable displacement mechanism allows the pump to achieve adequate fuel flow across all operating speeds without requiring a large fixed displacement design. By adjusting displacement dynamically, the pump can operate with a smaller base size while meeting fuel flow requirements at all speeds, thus reducing pump mass while maintaining fuel flow adequacy.
4Quantity of substance
If a recirculation loop is implemented to manage excess fuel, then fuel flow regulation is achieved, but the complexity of the fuel circuit increases
Solution Approach 1:
The variable displacement pump simplifies the fuel circuit architecture by regulating fuel flow through pump displacement control rather than requiring a complex recirculation system with multiple valves and control mechanisms. This dynamic pump control approach achieves fuel flow regulation with fewer components and less circuit complexity.
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 power consumption, simplifies the fuel circuit, minimizes the size of the recirculation loop, and optimizes the pump's displacement, ensuring fuel flow matches operational needs, thereby enhancing turbomachine efficiency and reducing the size and mass of the fuel circuit components.
Implementation Method 1
a reduction gear with an epicyclic gear train comprising three elements, a central sun gear, an external ring gear and a planet carrier whose satellites mesh with the sun gear and the crown
Implementation Method 2
first electrical means arranged to rotate the third of said elements of the reducer, so as to modify a rotation speed ratio between the first and the second of said elements
Implementation Method 3
second electrical means are coupled to the first or the second of said elements of the reducer, the first and second electrical means being arranged to transfer electrical power reversibly from one to the other
Data Source
Figure 1~2
Figure 3~4c
Figure 5~6
AI summary
The invention relates to a transmission device (6) for driving a fuel pump (1) for a turbomachine using a drive shaft of said turbomachine, said transmission comprising a planet reduction gearing (11) comprising three elements, a central planet gear (11A), an outer ring gear (11B) and a planet carrier (11U), the planets (11S) of which engage with the planet gear and the ring gear, a first of the three elements to be connected to the drive shaft and a second of the three elements to be coupled to a shaft of the pump, characterised in that said three elements can be rotated about a shaft of the reduction gearing, and in that the device also comprises first electrical means (12) arranged so as to rotatably drive the third of said elements of the reduction gearing (11) in such a way as to modify a rotational speed ratio between the first and the second of said elements, and second electrical means (13) coupled to the first or the second of said elements of the reduction gearing (11), the first and second electrical means being arranged so as to transfer electrical power reversibly from one to the other. The invention also relates to a method for adjusting the speed of the pump.