Diesel Fuel System Rerouting Return Line Upstream of Filter
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Solution Overview
Problem
Existing fuel systems for diesel engines face inefficiencies due to the return of fuel from injectors to the fuel tank, which requires a higher capacity low pressure feed pump, difficulties in starting with piezoelectric injectors lacking residual pressure, and inadequate fuel temperature mixing leading to pump durability issues.
Innovation Solution
Rerouting the fuel return line from the injectors to the low pressure fuel line upstream of the fine filter, combined with a fuel cooler to reduce fuel temperature, eliminates the need for a separate filter in the return line, improves mixing, and reduces pump capacity requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If fuel return lines are coupled to the fuel tank, then fuel is returned to the tank, but the low pressure feed pump must pressurize the fuel again and a higher capacity pump is required
Solution Approach 1:
The patent extracts the fuel return flow from the fuel tank and redirects it to the low pressure fuel line between the feed pump and high pressure pump. This allows the returned fuel to be re-pressurized along with the fresh fuel supply, eliminating the need for a separate high capacity pump to handle return fuel.
Solution Approach 2:
The patent merges the fuel return line with the low pressure fuel supply line, combining the returned fuel with the fresh fuel from the tank. This consolidation allows a single low pressure pump to handle both fresh and returned fuel, improving system efficiency.
2Reliability
If return lines are coupled to the fuel tank, then residual pressure is lost, but piezoelectric injectors require residual pressure to operate properly
Solution Approach 1:
The low pressure fuel line acts as an intermediary between the fuel tank and high pressure pump, providing a pathway to maintain residual pressure in the return lines while allowing fuel circulation. The fine filter in this line also serves as a flow resistance element to maintain pressure.
3Reliability
If two fine filters are provided in the fuel system, then fuel filtration is improved, but maintenance cost and complexity increase
Solution Approach 1:
The patent removes one fine filter from the system by eliminating the separate fuel return line to the tank. The single fine filter in the low pressure fuel line now filters both fresh fuel and returned fuel, reducing filter count while maintaining filtration effectiveness.
4Temperature
If return fuel is teed into the low pressure line between high and low pressure pumps, then fuel mixing occurs, but inadequate mixing results in temperature variations at the high pressure pump
Solution Approach 1:
The low pressure fuel line with fine filter acts as a mixing zone where hot return fuel and cooler fresh fuel are combined. The fine filter creates turbulence and flow resistance that promotes mixing, and the extended line length allows thermal equilibrium to be approached before fuel enters the high pressure pump.
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 simplifies the system, reduces maintenance costs, enhances starting performance, and prevents high temperature fuel from overwhelming the high pressure pump, leading to improved efficiency and durability.
Implementation Method 1
The two streams of fuel are combined but little mixing ensues before the fuel enters the high pressure pump... When the pump is provided a slug of the hotter fuel, it can exceed the maximum design temperature of the high pressure fuel pump
Implementation Method 2
a fine filter disposed therein
Implementation Method 3
a low pressure fuel pump supplying pressurized flow to the high pressure fuel system
Implementation Method 4
The injectors are designed such that a portion of the fuel delivered to the injectors is used to actuate the injector; the portion of fuel that used to actuate the injector is returned to a lower pressure portion of the fuel system
Data Source
AI summary
A fuel system for a diesel engine has both a low pressure pump, which extracts fuel from the fuel tank, and a high pressure pump, which is fed by the low pressure pump and supplies fuel to fuel injectors. The fuel injectors supply fuel to the engine cylinders, with a small portion of fuel routed back into the fuel system. According to an embodiment of the present disclosure, the injector return fuel is routed into a low pressure fuel line between the low and high pressure fuel pumps, with return fuel from the fuel rails returned through a fuel cooler to the fuel tank. The low pressure fuel line has a filter disposed therein and the injector return fuel is returned to the low pressure fuel line upstream of the filter.