High-Pressure Fuel Pump Seal Recirculation for Liquefied Gas Leakage
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Solution Overview
Problem
High-pressure fuel pumps designed for liquefied gases like DME and propane experience significant leakage rates due to their low viscosity, leading to compromised lubrication systems, wear, and inefficient combustion processes at pressures above 500 bar, which existing technologies fail to adequately address.
Innovation Solution
A high-pressure pump design featuring a plunger seal with a recirculation passage that maintains a constant pressure on the fuel side, ensuring separation from lubricating oil and controlling leakage by directing excess fuel back to the pump inlet, thereby stabilizing seal performance and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If high-pressure fuel pumps are designed for Diesel fuel, then they can operate above 2000 bar, but they cannot operate with liquefied gases like DME due to significantly higher leakage rates caused by lower viscosity
Solution Approach 1:
The patent changes the operating parameters by maintaining the pump at lower pressures (below 500 bar) when handling liquefied gases, rather than operating at the high pressures (above 2000 bar) used for Diesel fuel. This parameter adjustment reduces the pressure differential that drives leakage through the plunger seal, making the pump suitable for low-viscosity liquefied gases while accepting the pressure limitation as a necessary trade-off
Solution Approach 2:
The patent introduces a dynamic pressure compensation mechanism where excess fuel leaking past the plunger seal is recirculated back to the inlet side of the pump. This creates a dynamic balance that maintains lower pressure on the inlet side of the seal, reducing the pressure differential and thereby reducing leakage rates during operation with liquefied gases
2Reliability
If pumping pressure is limited to below 500 bar to reduce leakage, then lubrication system wear is reduced, but combustion optimization is hindered due to insufficient fuel mixing with charge air
Solution Approach 1:
The patent introduces a recirculation passage as an intermediary system that captures leaked fuel and returns it to the inlet. This mediator prevents the leaked fuel from contaminating the lubrication oil while also maintaining the pressure differential needed to reduce leakage, thereby protecting the lubrication system without requiring higher operating pressures that would compromise combustion efficiency
3Object-affected harmful factors
If a seal is placed around the pump piston plunger to prevent fuel leakage, then fuel-to-oil dilution is reduced, but pressure pulsations weaken seal function and reduce lifespan
Solution Approach 1:
The patent implements a feedback mechanism where fuel that leaks past the seal is detected and recirculated back to the inlet side of the pump. This feedback loop maintains lower pressure on the inlet side of the seal, reducing the pressure pulsations that degrade the seal while still preventing fuel from entering the crankcase and contaminating the lubrication oil
Solution Approach 2:
The patent converts the harmful effect of fuel leakage past the seal into a beneficial outcome by recirculating the leaked fuel back to the inlet. The leakage that would normally weaken the seal through pressure pulsations is instead used to maintain lower inlet pressure, and the recirculated fuel is reused, turning a harmful leakage path into a pressure management feature that extends seal life
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
The solution effectively reduces leakage and maintains seal integrity at high pressures, ensuring efficient fuel delivery and optimized combustion processes for liquefied gases, while preventing fuel-to-oil contamination and wear.
Implementation Method 1
The recirculation passage can be exposed to the seal or to an annulus groove in the pump housing bore placed along the plunger isolating the seal from the inlet pressure pulsations taking place during the pumping process
Implementation Method 2
a seal around the pump piston plunger. The seal prevents fuel from passing into the pump crankcase
Implementation Method 3
These liquefied gases are supplied through a fuel delivery pump to the high-pressure pump at pressures above the saturation vapor point, ensuring the fuel remains in liquid form
Data Source
AI summary
A high-pressure fuel pump for low-viscosity liquefied gases includes a plunger within a pump body and a seal surrounding the plunger to block fuel leakage into the crankcase. A communication passage connects the fuel side of the seal to the pump inlet, maintaining the seal at a substantially constant pressure near inlet supply pressure. In certain embodiments, the passage communicates with an annular groove positioned between the high-pressure chamber and the seal to isolate the seal from pressure pulsations and over-pressurization. This configuration improves seal durability, reduces leakage, and maintains separation between fuel and lubricating oil during high-pressure operation.