Fuel Metering System with External Pump and Extraction Valve
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Solution Overview
Problem
Existing fuel metering devices for self-igniting, air-compressing internal combustion engines face issues with bubble formation during restart, increased wear on fuel pumps, and the inability to repair pumps when the tank is full, leading to poor engine restart properties and potential engine failure.
Innovation Solution
The fuel metering device extracts the pressurized fuel mixture via an extraction valve located at the tank's lower area, using a pressure booster pump outside the pressure mixing tank, and includes an overpressure and bypass valve to return excess fuel safely, allowing for bubble-free operation and external maintenance of pumps. Additionally, a second tank with a vapor pressure buffer space for diesel fuel or other oils enables bubble expulsion during engine restart.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the fuel pump is arranged inside the pressure mixing tank, then the tank can be filled to maximum capacity, but the pump cannot be repaired when the tank is full and maintenance becomes difficult
Solution Approach 1:
The system separates the fuel storage function (pressure mixing tank) from the fuel delivery function (external fuel pump). The tank maintains maximum capacity while the pump is positioned externally on the tank wall, allowing independent access to the pump for maintenance without draining the tank.
Solution Approach 2:
An extraction valve arranged in the tank wall acts as an intermediary between the internal fuel mixture and the external pump. This allows the pump to be positioned outside the tank while still accessing fuel through the valve, resolving the contradiction between storage capacity and maintenance accessibility.
2Reliability
If excess fuel is returned to the pressure mixing tank, then the injection system is protected from overpressure, but the fuel pump experiences increased wear due to continuous operation
Solution Approach 1:
The overpressure valve creates a feedback mechanism that monitors system pressure and redirects excess fuel back to the tank when pressure exceeds thresholds. This protects the injection system while allowing the pump to operate within safe pressure ranges, reducing unnecessary wear from continuous high-pressure operation.
Solution Approach 2:
The system uses pressure as a controlling parameter to switch between normal operation and bypass modes. When pressure exceeds the overpressure valve setting, the flow path changes to return fuel to the tank, protecting both the injection system and the pump from sustained high-pressure stress.
3Productivity
If the engine is restarted while at operating temperature, then continuous operation is maintained, but bubble formation in lines occurs due to outgassed components, leading to poor restart properties
Solution Approach 1:
The extraction valve positioned at the lower area of the tank and the external pump arrangement create a bubble-free extraction path. By drawing fuel from the bottom where settled fuel resides and positioning the pump externally with proper filtration, the system prepares bubble-free fuel delivery before restart, preventing combustion issues.
Solution Approach 2:
The system creates different quality zones within the fuel system: the lower tank area provides settled, bubble-free fuel extraction, while the external pump area allows for filtration and bubble separation. This local quality differentiation ensures reliable fuel delivery during restart conditions.
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 configuration ensures bubble-free fuel delivery, reduces wear on pumps, allows for external maintenance, and improves engine restart properties, enabling cleaner combustion and reduced emissions with the use of renewable biofuels like rapeseed oil and biogenic propane/butane, while maintaining engine performance and safety.
Implementation Method 1
a pressure booster pump-trained fuel pump is arranged downstream of the extraction valve in the direction of flow of the fuel mixture outside the pressure mixing tank
Implementation Method 2
another fuel pump and the high-pressure pump for further delivery into the injection system
Implementation Method 3
an overpressure and bypass valve for returning the fuel mixture via the return line into the pressure mixing tank is provided
Implementation Method 4
the pressurized fuel mixture is extracted via the extraction valve via a wall located in the lower area of the tank, so that a static pressure acts on the extraction valve
Data Source
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AI summary
The invention relates to a fuel metering device in particular for a self-igniting air-compressing internal combustion engine, comprising a fuel pump for delivering a fuel, wherein the fuel can be withdrawn from a tank and supplied via a high-pressure pump to an injection system of the internal combustion engine, and wherein excess fuel can be recirculated from the injection system via a recirculating line in the injection system, and wherein the tank is designed as a pressure mixing receptacle having a vapour pressure buffer chamber to receive a first fuel such as diesel fuel, rapeseed oil, soyseed oil, sunflower oil, palm oil or fats and a further fuel such as a liquefied petroleum gas (LPG fuel), and a pressurised fuel mixture formed of the first fuel and the second fuel can be withdrawn from the pressure mixing receptacle serving as a tank via an extraction valve and supplied to the high-pressure pump of the injection system via the fuel pump designed as a booster pump. It is characterised in that the withdrawal of the pressurised fuel mixture via the extraction valve takes place via a wall located in the lower region of the tank, such that a static pressure acts on the extraction valve and the fuel pump designed as a booster pump is disposed downstream of the extraction valve in the flow direction of the fuel mixture outside of the pressure mixing receptacle, wherein a pressure relief and bypass valve for recirculating the fuel mixture via the recirculating line to the pressure mixing vessel is provided downstream of the fuel pump and upstream of the injection system in the fuel flow direction.