Fuel Rail Vent System Air Purging
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Solution Overview
Problem
Fuel injected internal combustion engines, particularly those with pull start mechanisms like marine engines, face difficulties in starting due to air presence in the fuel rail, which reduces the likelihood of successful engine ignition.
Innovation Solution
A fuel rail vent system incorporating a high pressure fuel pump, a primer pump, and separate fuel lines with check valves and vapor vent valves ensures liquid fuel is present in the fuel rail by evacuating air through a secondary fuel reservoir, ensuring fuel injectors receive liquid fuel during engine start-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single fuel line is used from the fuel reservoir to the fuel rail, then the system structure is simple, but air can remain trapped in the fuel rail causing starting problems
Solution Approach 1:
The fuel delivery system is segmented into multiple independent fuel lines: a primary fuel line for normal operation and a secondary fuel line for priming and air purging. This segmentation allows the system to address air trapping issues without completely redesigning the fuel delivery architecture, maintaining simplicity while improving reliability.
Solution Approach 2:
A second fuel reservoir is introduced as an intermediary component between the fuel tank and the fuel rail. This intermediate reservoir serves as a collection point for air and excess fuel, allowing air to be purged from the system while fuel is delivered to the injectors. The intermediary reservoir resolves the contradiction by providing a dedicated space for air separation.
2Reliability
If the fuel rail is vented to allow air escape, then air can be purged from the system, but fuel vapor may be lost to the atmosphere
Solution Approach 1:
The system converts the potentially harmful fuel vapor loss into a beneficial recirculation process. Instead of venting fuel vapor directly to the atmosphere, the second fuel reservoir captures the vapor and returns it to the fuel supply system through a return line. This transforms the harmful vapor loss into a benefit by reducing emissions and preventing fuel waste.
Solution Approach 2:
Fuel vapor that would normally be discarded through venting is instead recovered and returned to the fuel system. The second fuel reservoir acts as a collection point where vapor is condensed or captured and then returned to the first fuel reservoir through the return line, ensuring that no fuel is lost and emissions are minimized.
3Reliability
If a primer pump is added to force fuel through the system, then air can be purged from the fuel rail, but the system complexity increases
Solution Approach 1:
The primer pump is designed to perform multiple functions: it can force fuel through the system during priming operations, it can purge air from the fuel rail, and it can maintain fuel pressure in the system. By making the pump multi-functional, the system reduces the need for additional separate components, thereby limiting the increase in complexity while maximizing the reliability benefits.
Solution Approach 2:
The primer pump enables preliminary action by allowing the operator to manually prime the fuel system before engine operation. This preliminary fuel delivery through the second fuel line ensures that air is purged and fuel is present in the fuel rail before the engine needs to start, preventing starting problems without requiring continuous complex active systems.
4Reliability
If check valves are installed in the fuel lines, then fuel flow control is improved, but the manufacturing complexity increases
Solution Approach 1:
Check valves are merged into the fuel line assemblies rather than being separate installed components. The check valve functionality is integrated directly into the fuel line structure, allowing fuel flow control to be built-in during manufacturing. This merging approach improves reliability through better flow control while reducing manufacturing complexity by eliminating separate assembly steps.
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 system reliably ensures liquid fuel is delivered to the fuel injectors, enhancing the engine's starting reliability by purging air from the fuel rail, thus optimizing the chances of successful engine ignition.
Implementation Method 1
a primer pump configured for fluid communication with the first fuel reservoir to pump liquid fuel under pressure from the first fuel reservoir to the fuel rail through the second fuel line
Implementation Method 2
a high pressure fuel pump configured for fluid communication with the first fuel reservoir to pump liquid fuel under pressure from the first fuel reservoir to the fuel rail through the first fuel line
Implementation Method 3
The second fuel reservoir is configured for fluid communication with the fuel rail downstream of the fuel rail to receive any excess liquid fuel and/or fuel vapor upstream therefrom
Data Source
AI summary
A fuel rail vent system for evacuating air from a fuel rail includes a first fuel reservoir and a first fuel line extending between the first fuel reservoir and the fuel rail. A fuel pump is configured in fluid communication with the first fuel reservoir to pump liquid fuel from the first fuel reservoir to the fuel rail through the first fuel line. A second fuel line separate from the first fuel line extends between the first fuel reservoir and the fuel rail. A primer system is configured for fluid communication with the first fuel reservoir to pump liquid fuel from the first fuel reservoir to the fuel rail through the second fuel line. A second fuel reservoir separate from the first fuel reservoir is configured for fluid communication with the fuel rail downstream of the fuel rail to receive any excess liquid fuel and/or fuel vapor upstream therefrom.