Variable Displacement Radial Piston Pump for Aircraft Fuel Systems
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Solution Overview
Problem
Conventional fixed displacement fuel pumps for aircraft turbine engines require high output flow rates, leading to excess fuel circulation and heating issues, necessitating the use of complex and weighty heat exchangers to cool the fuel, which increases system complexity, weight, and cost.
Innovation Solution
A radial piston pump design with a pivotally supported cylinder ring and actuator-controlled cam surface allows for variable displacement by altering the spatial relationship between the cylinder ring and block, adjusting piston stroke and fluid flow, thereby optimizing fuel delivery and reducing excess flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed displacement pump is used to provide sufficient fuel pressure and flow over a wide range of operating speeds, then the pump can meet the minimum fuel flow requirements, but the pump produces excess flow that circulates through the bypass circuit and heats the fuel
Solution Approach 1:
The patent applies a variable displacement mechanism where the cylinder ring can be positioned at different radial distances from the cam surface by adjusting the tilt angle of the actuator arm. This dynamic adjustment allows the piston stroke length to vary, thereby controlling the fuel flow rate to match actual engine requirements and prevent excessive fuel circulation and heating
Solution Approach 2:
The patent changes the geometric parameter of the pump by varying the radial position of the cylinder ring relative to the cam surface. By adjusting the actuator arm tilt angle, the effective stroke length of the pistons is modified, which directly controls the fuel delivery quantity to eliminate excess flow and associated heating problems
2Temperature
If a heat exchanger is added to the bypass circuit to cool the fuel, then the fuel temperature can be controlled, but the system complexity, weight, and expense increase
Solution Approach 1:
The patent extracts and eliminates the need for the heat exchanger by addressing the root cause of fuel heating - excess fuel circulation. By implementing variable displacement control, the pump delivers only the required fuel amount, preventing overflow and subsequent heating, thereby removing the heat exchanger component entirely and simplifying the system
Solution Approach 2:
The patent converts the potential harm of excess fuel circulation and heating into a benefit by using the actuator mechanism to precisely control fuel delivery. The system transforms what would be a harmful thermal effect into an opportunity for efficient fuel management and system simplification
3Loss of energy
If a variable displacement mechanism is implemented to control fuel flow, then excess flow and heating are eliminated, but the pump structure becomes more complex
Solution Approach 1:
The actuator arm serves multiple functions: it controls the radial position of the cylinder ring to vary piston stroke length, provides mechanical leverage for precise control, and integrates with the existing pump structure. This multi-functionality achieves variable displacement capability while minimizing additional structural 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 design enhances pump reliability, reduces size and weight, and extends operating limits by precisely controlling fluid flow, eliminating the need for heat exchangers and improving fuel system efficiency.
Implementation Method 1
a cam surface is formed... An annular bearing ring is located within the circular aperture and has an inner circumferential surface that forms an interior cylindrical cam surface
Implementation Method 2
A plurality of cylinders pistons, which are free to slide, are received within the plurality of cylinders and engage the cam surface of the cylinder ring
Implementation Method 3
An actuator is operably coupled to produce movement of the cylinder ring, which alters the spatial relationship between the cylinder ring and the cylinder block to vary the distance that the pistons move within the cylinders
Data Source
AI summary
A radial pump has a housing with a cylinder ring is pivotally mounted therein. The cylinder ring has a circular aperture within which a cam surface is formed. A cylinder block rotates within the cylinder ring aperture and has a plurality of radially extending cylinders each having port which selectively communicates with a fluid inlet and a fluid outlet as the cylinder block rotates. A plurality of pistons is slideably received within the cylinders and engages the cam surface. An actuator operably coupled to produce movement of the cylinder ring, which alters the spatial relationship between the cylinder ring and the cylinder block to vary the amount that the pistons move within the cylinders. The amount of movement of the pistons within the cylinders is directly related to the magnitude of fluid flow delivered by the pump and moving the cylinder ring thereby controls the fluid flow.