Engine Control System for Stochastic Pre-ignition Mitigation
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Solution Overview
Problem
Conventional engine control systems are ineffective in preventing stochastic pre-ignition, a random and severe abnormal combustion process that occurs in boosted engines, leading to excessive peak pressures and potential engine damage.
Innovation Solution
A control system that advances spark timing past a spark limit for consecutive cylinder firing events and supplies a rich fuel-air charge to prevent and mitigate stochastic pre-ignition by dislodging and suppressing fuel-oil deposits, using a spark module and fuel module to manage spark timing and fuel-air equivalence ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If spark timing is advanced past the spark limit to improve combustion efficiency, then power output increases, but stochastic pre-ignition occurs causing excessive peak pressures and potential engine damage
Solution Approach 1:
The system performs preliminary action by advancing spark timing past the spark limit for N consecutive cylinder firing events before stochastic pre-ignition occurs, inducing spark-knock to dislodge fuel-oil deposits that serve as pre-ignition sources. This preventive measure is taken in advance to eliminate the root cause of stochastic pre-ignition, allowing the system to subsequently operate with more aggressive spark timing without suffering from pre-ignition damage.
Solution Approach 2:
The system converts the harmful effect of spark-knock (which was traditionally avoided) into a beneficial cleaning mechanism. By deliberately inducing spark-knock through advanced spark timing, the system dislodges and removes fuel-oil deposits from the combustion chamber that would otherwise cause stochastic pre-ignition. This transforms spark-knock from a harmful phenomenon to a useful deposit-removal mechanism that improves long-term engine reliability.
2Reliability
If spark timing is retarded to prevent stochastic pre-ignition, then engine damage is avoided, but combustion efficiency and power output decrease
Solution Approach 1:
The system implements periodic action through cyclic alternation between two operational modes: a cleaning mode where spark timing is advanced past the spark limit for N consecutive firing events to induce spark-knock and dislodge deposits, followed by a protection mode where spark timing is retarded for M consecutive firing events to prevent stochastic pre-ignition. This periodic switching allows the system to achieve both deposit removal and pre-ignition prevention over time, balancing reliability and power output.
3Reliability
If a rich fuel-air charge is supplied to suppress pre-ignition events, then stochastic pre-ignition is reduced, but fuel consumption increases
Solution Approach 1:
The system applies partial action by supplying rich fuel-air charge (fuel-air equivalence ratio greater than 1.0) only for M consecutive cylinder firing events after spark timing is retarded, rather than continuously enriching the mixture. This temporary enrichment is sufficient to suppress remaining pre-ignition events and cool combustion chamber surfaces, while limiting fuel consumption by returning to stoichiometric or leaner mixtures during normal operation.
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 effectively reduces the occurrence of stochastic pre-ignition by inducing spark-knock to dislodge deposits and enriching the fuel-air charge to suppress remaining pre-ignition events, thereby reducing the probability of engine damage and peak pressure issues.
Implementation Method 1
combustion is initiated by an electrical discharge or spark that supplies energy to the fuel-air charge. Once initiated, combustion continues along a flame front
Implementation Method 2
The fuel module supplies a rich fuel-air charge to the cylinder for the M consecutive cylinder firing events
Implementation Method 3
a fuel-air equivalence ratio of the fuel-air charge is greater than 1.0 and less than 1.5
Data Source
AI summary
A control system for an engine includes a spark module and a fuel module. The spark module advances spark timing of a cylinder R degrees past a spark limit for N consecutive cylinder firing events, and retards spark timing of the cylinder past the spark limit for M consecutive cylinder firing events after the N consecutive cylinder firing events. The fuel module supplies a rich fuel-air charge to the cylinder for the M consecutive cylinder firing events. According to the system, R is a real number greater than zero, N and M are integers greater than zero, and the spark limit is a control value used to limit an amount of spark advance to prevent spark-knock. A method for controlling an engine is also provided.