Fuel Pump Sealing Liquid Chamber Dynamics
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Solution Overview
Problem
Fuel pumps for large two-stroke internal combustion engines using alternative fuels like LPG or LNG face challenges in preventing fuel leakage, which contaminates the sealing liquid and increases emission levels due to the fluctuating pressure in the fuel chamber, requiring a complex and costly system to maintain sealing liquid pressure in sync with fuel pressure.
Innovation Solution
A fuel pump design featuring two plungers in series within a single bore, with a sealing liquid chamber between them, where the drive plunger pushes the pump plunger without direct contact, ensuring the sealing liquid pressure follows the fuel pressure fluctuations, preventing fuel from reaching the proximal side of the pump plunger and minimizing sealing liquid contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sealing liquid pressure is maintained higher than the maximum fuel pressure to prevent fuel leakage, then fuel sealing reliability is improved, but sealing liquid contamination increases due to steady flow into the pump chamber
Solution Approach 1:
The patent applies dynamics by making the sealing liquid pressure variable rather than constant. The sealing liquid pressure follows the fuel pressure fluctuations dynamically, being higher than fuel pressure during aspiration stroke and lower during pump stroke. This resolves the contradiction by adapting the sealing pressure to actual needs, preventing fuel leakage when required while minimizing unnecessary sealing liquid flow into the pump chamber.
Solution Approach 2:
The patent changes the pressure parameter of the sealing liquid from a fixed high value to a variable value that tracks fuel pressure fluctuations. By adjusting the sealing liquid pressure parameter dynamically based on fuel pressure conditions, the system achieves effective fuel sealing while reducing excessive pressure differential that causes sealing liquid contamination.
2Loss of substance
If the sealing liquid pressure is set between minimum and maximum fuel pressure to reduce contamination, then sealing liquid loss is reduced, but fuel leakage risk increases during pump stroke
Solution Approach 1:
The system dynamically adjusts sealing liquid pressure to match fuel pressure conditions. During pump stroke when fuel pressure is high, sealing liquid pressure is reduced to avoid excessive contamination. During aspiration stroke when fuel pressure is low, sealing liquid pressure is increased to prevent fuel leakage. This dynamic adaptation resolves the contradiction between reducing contamination and maintaining sealing reliability.
Solution Approach 2:
The sealing liquid pressure operates periodically in sync with the pump cycle, alternating between high pressure (during aspiration stroke) to prevent leakage and lower pressure (during pump stroke) to reduce contamination. This periodic variation in sealing pressure resolves the contradiction by providing appropriate pressure levels at appropriate times in the operational cycle.
3Reliability
If a complex pressure control system is used to synchronize sealing liquid pressure with fuel pressure, then fuel sealing reliability is improved, but device complexity increases
Solution Approach 1:
The patent introduces a sealing liquid chamber as an intermediary between the fuel pressure source and the sealing liquid supply system. This chamber acts as a pressure buffer that naturally follows fuel pressure fluctuations, simplifying the control mechanism. The intermediary chamber eliminates the need for complex active pressure control systems while maintaining reliable fuel sealing.
Solution Approach 2:
The sealing liquid chamber is designed to automatically follow fuel pressure variations without external control. The system is self-regulating, where changes in fuel pressure automatically translate to corresponding changes in sealing liquid pressure through the chamber mechanism. This self-service approach eliminates complex control systems while maintaining effective sealing.
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 effectively maintains the sealing liquid pressure in sync with fuel pressure fluctuations, preventing fuel leakage and reducing emission contamination, while maintaining a simpler and less expensive pump system.
Implementation Method 1
A sealing liquid is supplied to a second clearance between the pump plunger and the second bore at a pressure that follows the pressure fluctuations of the fuel in the pump chamber, thereby the sealing liquid follows the pump plunger in the second clearance when the pump plunger moves between its retracted position and its extended position, and prevents fuel from reaching the proximal side of the pump plunger in the second clearance
Implementation Method 2
The drive plunger pushes the pump plunger without direct contact between the drive plunger and the pump plunger
Data Source
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AI summary
A fuel pump for pumping fuel to a fuel valve. The fuel pump has a housing with a first bore (84) and a second bore (81). A hydraulically driven actuation piston (83) is slidably received in the first bore (84) and configured to be movable between a retracted position and an extended position. A drive plunger (80) is operably connected to the actuation piston (83) to move in unison with the actuation piston (83). The drive plunger (80) is slidably received with a first clearance (91) in the second bore (81). A pump plunger (87) is slidably received with a second clearance (92) in the second bore (81) and configured to be movable between a retracted position and an extended position. A sealing liquid chamber (86) is arranged in the second bore (81) between a distal side of the drive plunger (80) and a proximal side of the pump plunger (87). A pump chamber (82) is arranged in the second bore (81) on a distal side of the pump plunger (87).