Spark Plug Fouling Mitigation via EGR and Ignition Control
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Solution Overview
Problem
Spark plug fouling occurs frequently, especially in green engines at assembly plants, due to cooler spark plug tip temperatures caused by exhaust gas recirculation (EGR), which hinders soot burning and leads to misfires, conflicting with fuel economy and emissions reduction goals.
Innovation Solution
Adjusting the EGR schedule by reducing EGR more significantly in green engines at assembly plants to maintain higher spark plug tip temperatures for cleaning and reducing EGR less when the engine is no longer green to balance cleaning with emissions compliance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If EGR is used to slow combustion and cool combustion temperatures to reduce engine knock and NOx emissions, then fuel economy and emissions performance are improved, but spark plug tip temperatures become too cool to burn off soot, leading to spark plug fouling
Solution Approach 1:
The system performs preliminary detection of spark plug fouling conditions using ionization current measurements, and proactively initiates cleaning operations by adjusting EGR rates before complete fouling occurs. This preventive approach maintains spark plug reliability while minimizing disruption to normal EGR-based emissions control
Solution Approach 2:
The system dynamically changes the EGR rate parameter based on detected spark plug conditions. When fouling is detected, the EGR rate is reduced or eliminated temporarily to allow spark plug tip temperatures to rise and burn off soot deposits, then returns to normal EGR scheduling once cleaning is complete
2Reliability
If aggressive spark advance is used to raise spark plug tip temperatures for soot burning, then spark plug cleaning is promoted, but it conflicts with engine commands for fuel economy
Solution Approach 1:
The system detects fouling conditions early using ionization current measurements and initiates minimal spark advance adjustments proactively. This early intervention requires less energy correction than waiting for severe fouling, thereby maintaining better fuel economy while still achieving spark plug cleaning
Solution Approach 2:
The system applies only the necessary degree of spark advance to achieve spark plug cleaning, rather than aggressive advance. By using minimal spark timing adjustment sufficient to raise tip temperatures temporarily, the system achieves cleaning while minimizing fuel economy penalties
3Productivity
If the engine is operated frequently at lower speeds and light loads during assembly plant testing, then engine components are tested thoroughly, but spark plug fouling occurs more frequently due to cooler spark plug tip temperatures
Solution Approach 1:
The system continuously monitors ionization current during assembly plant testing to detect spark plug fouling conditions in real-time. This feedback enables the controller to identify when spark plug tip temperatures are insufficient and triggers appropriate EGR or spark timing adjustments to prevent fouling, allowing continuous testing without spark plug failures
Solution Approach 2:
The system performs preliminary detection of fouling tendencies during normal low-speed testing operations and takes preventive action by adjusting EGR or spark timing before actual fouling occurs. This allows the engine to complete testing schedules without spark plug failures that would interrupt productivity
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 approach effectively raises and maintains spark plug tip temperatures for longer durations, expediting cleaning without compromising fuel economy or emissions performance, reducing cylinder misfires and improving spark plug health.
Implementation Method 1
a spark plug for delivering an electric current to a combustion chamber of a spark-ignited engine to ignite an air-fuel mixture and initiate combustion
Implementation Method 2
a controller may operate an engine with exhaust gas recirculation to slow combustion, and cool combustion temperatures
Implementation Method 3
the spark plug may be cleaned by burning off the soot accumulated on the fouled spark plug by operating the engine in speed-load conditions that sufficiently raise the spark plug tip temperature
Data Source
AI summary
Methods and systems are provided for addressing spark plug soot fouling. In one example, spark plug tip temperatures are raised and maintained elevated by advancing spark timing and increasing engine speed, while reducing an amount of EGR being delivered to the engine. The spark plug fouling mitigating actions are adjusted based on whether the engine is in a green condition at an assembly plant or not.