Fuel Rail Pressure Control for Cold Start Emission Reduction
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Solution Overview
Problem
Spark ignition direct injection (SIDI) engines generate increased particulate emissions during cold starts due to incomplete combustion of fuel on piston and cylinder walls, as the fuel injected at low temperatures is not fully ignited, leading to inefficient fuel stratification and higher emissions.
Innovation Solution
A fuel control system that includes a target rail pressure module, an offset module, and a modifier module to adjust fuel rail pressure based on engine speed, load, air per cylinder, and temperature, using a rail pressure control module to optimize fuel rail pressure and injector operation, thereby improving fuel stratification and reducing particulate emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fuel is injected into combustion chambers during cold engine start, then fuel supply to cylinders is maintained, but fuel impinges on piston and cylinder walls causing incomplete combustion and increased particulate emissions
Solution Approach 1:
The patent adjusts fuel rail pressure as a key parameter based on engine temperature conditions. During cold starts, the system modifies fuel pressure to prevent fuel impingement on cold surfaces while maintaining adequate fuel supply. This dynamic parameter adjustment resolves the contradiction between ensuring fuel delivery and preventing incomplete combustion that generates particulates.
2Manufacturing precision
If fuel rail pressure is increased to improve fuel atomization, then combustion efficiency improves, but fuel impingement on cold surfaces increases during cold starts
Solution Approach 1:
The patent implements dynamic fuel rail pressure control that adapts to real-time engine conditions, particularly temperature. The system transitions from static pressure control to dynamic adjustment, modifying pressure levels based on whether the engine is cold or warmed up. This dynamic approach allows optimal pressure during normal operation for good atomization while reducing pressure during cold starts to prevent impingement.
Solution Approach 2:
The system changes the fuel rail pressure parameter according to engine temperature state. During cold starts, pressure is reduced to prevent impingement; during normal operation, pressure is optimized for atomization. This parameter transformation resolves the contradiction between atomization quality and impingement prevention.
3Device complexity
If conventional multi-point fuel injection is used, then system complexity is reduced, but fuel efficiency and power output are compromised
Solution Approach 1:
The patent applies preliminary action by adjusting fuel rail pressure before fuel injection occurs during cold starts. By pre-conditioning the fuel pressure based on detected engine temperature, the system prepares optimal injection conditions in advance, preventing impingement before it happens. This allows direct injection benefits to be realized without excessive complexity.
Data Source
AI summary
A fuel control system includes a target rail pressure module. The target rail pressure module determines a target fuel rail pressure of a fuel rail of a direct injection engine. An offset module determines an offset value based on an engine speed of the direct injection engine and at least one of an engine load and an air per cylinder. A modifier module determines a modifier value based on a temperature of the direct injection engine. A rail pressure control module adjusts a current fuel rail pressure of the fuel rail based on the target fuel rail pressure, the offset value and the modifier value.