Aircraft Fuel System Variable Displacement Pump Dynamics
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Solution Overview
Problem
Conventional aircraft engine fuel systems experience heat rejection and increased fuel consumption due to excess fuel being pumped against system pressure, leading to inefficient cooling and energy wastage.
Innovation Solution
The proposed aircraft fuel system incorporates a pressure regulating valve with grooved piston heads and an ejector pump to manage fuel flow and pressure differentials, ensuring constant pressurization and minimizing fuel recirculation during varying flight conditions, thereby reducing heat input and improving fuel efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a positive displacement pump is used to provide fuel through the fuel metering system, then the fuel flow can be maintained at maximum capacity, but excess fuel is spilled back to the low pressure side resulting in heat rejection and energy waste
Solution Approach 1:
The patent applies dynamics by making the pump displacement variable rather than fixed. The variable displacement mechanism allows the pump to adjust its fuel delivery volume to match actual engine demand, eliminating the need to spill excess fuel back to the low pressure side. This dynamic adjustment resolves the contradiction by maintaining full fuel flow capacity when needed while preventing energy-wasting recirculation during lower demand conditions.
Solution Approach 2:
The patent changes the parameter of pump displacement from fixed to variable. By incorporating a variable displacement mechanism that can adjust the pump's volumetric output based on system pressure and engine demand, the system optimizes fuel delivery efficiency. This parameter change eliminates heat rejection caused by excess fuel spilling while maintaining the ability to deliver maximum fuel flow when required.
2Stability of the object's composition
If fuel is spilled back to the low pressure side to maintain constant pressure drop across the metering valve, then pressure stability is achieved, but fuel heating occurs reducing cooling capacity
Solution Approach 1:
The patent uses dynamics to adjust pump displacement in response to pressure conditions. When pressure stability is achieved through the metering valve, the variable displacement pump reduces or stops fuel delivery, preventing excess fuel from being spilled back to the low pressure side. This eliminates the heat generation associated with forced fuel recirculation while maintaining pressure stability through coordinated control of pump displacement and metering valve positioning.
Solution Approach 2:
The patent implements feedback control where the system monitors pressure conditions and adjusts pump displacement accordingly. When the metering valve maintains the required pressure drop, the feedback mechanism signals the variable displacement pump to reduce output, preventing unnecessary fuel spilling and heat generation. This closed-loop control resolves the contradiction by dynamically balancing pressure stability with temperature control.
3Reliability
If the pump capacity is sized for maximum fuel flow with a safety margin, then sufficient fuel supply is ensured, but during idle conditions the pump output exceeds engine demand causing excess fuel recirculation
Solution Approach 1:
The patent applies dynamics by enabling the pump to vary its displacement according to engine operating conditions. During maximum power conditions, the pump operates at full displacement to ensure reliable fuel supply with safety margin. During idle conditions, the variable displacement mechanism reduces pump output to match actual engine demand, eliminating excess fuel recirculation and improving fuel efficiency while maintaining supply reliability when needed.
Solution Approach 2:
The patent changes the pump's operational parameter from fixed capacity to variable displacement. This allows the system to maintain the safety margin capacity for reliable fuel supply during high-demand conditions while dynamically reducing displacement during low-demand idle conditions. The parameter change enables the system to optimize fuel efficiency across the entire operating range without compromising supply reliability.
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 maintains accurate metered fuel flow and reduces energy wastage by minimizing fuel heating and optimizing fuel usage across different engine conditions, enhancing overall engine performance and reducing fuel consumption.
Implementation Method 1
an ejector pump, which is operably disposed between the check valve and the metering valve, and which, with the check valve closed, is configured to pump fuel toward the inlet side of the metering valve during idle conditions
Implementation Method 2
a pressure regulating valve to restrict fuel flow from main and auxiliary pumps, which are disposed to pump fuel to the inlet side in accordance with a pressure differential between the outlet side and fuel pumped by the auxiliary pump
Implementation Method 3
first and second connected piston heads elastically anchored to a first valve end and biased toward a second valve end, the second piston head having a groove that fluidly communicates with a conduit by which excess fuel pumped by the auxiliary pump is bypassed
Implementation Method 4
a check valve arranged, when open, to allow fuel to flow toward the inlet side during start and climb conditions and, when closed, to prevent such fuel flow
Implementation Method 5
a metering valve having inlet and outlet sides and being configured to monitor fuel flow from the inlet to the outlet side
Implementation Method 6
the second piston head having a groove that fluidly communicates with a conduit by which excess fuel pumped by the auxiliary pump is bypassed from the inlet side with the first and second piston heads moved toward the first valve end by a first distance from the second valve end
Data Source
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AI summary
An aircraft fuel system (10) is provided and includes a metering valve (20) having inlet and outlet sides (21,22) to monitor fuel flow from the inlet side (21) to the outlet side (22), a check valve (60) that, when opened, allows fuel to flow toward the inlet side (21) during start and climb conditions and, when closed, prevents such fuel flow and an ejector pump (70), which is operably disposed between the check valve (60) and the metering valve (20), and which, with the check valve (20) closed, pumps fuel toward the inlet side (21) during idle conditions.