Spark Ignition Engine Transitional Mode EGR Control
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Solution Overview
Problem
The switching from spark ignition combustion to compression ignition combustion in engines leads to increased combustion noise due to preignition caused by high temperatures, which results in a rapid pressure increase and loud noise.
Innovation Solution
The engine employs a transitional mode with a reduced EGR ratio immediately after switching from spark ignition to compression ignition, avoiding the introduction of high temperature exhaust gas and thus reducing cylinder temperature, preventing preignition and noise by controlling the EGR ratio and valve operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine switches from spark ignition combustion to compression ignition combustion, then thermal efficiency is improved, but combustion noise increases due to preignition caused by high cylinder temperature
Solution Approach 1:
The control device performs preliminary action by temporarily reducing the EGR ratio immediately after switching from spark ignition to compression ignition combustion. This prevents high-temperature exhaust gas from being introduced into the cylinder at the critical moment, thereby avoiding preignition and combustion noise before the engine stabilizes in compression ignition mode
Solution Approach 2:
The EGR ratio serves as an intermediary parameter that mediates between spark ignition and compression ignition modes. By temporarily adjusting the EGR ratio during the transition period, the control device regulates the temperature of introduced exhaust gas, thereby controlling cylinder temperature and preventing harmful preignition while maintaining the benefits of compression ignition
2Reliability
If high temperature burnt gas is introduced into the cylinder to ensure ignitability in compression ignition combustion, then combustion stability is improved, but preignition occurs due to excessively high cylinder temperature
Solution Approach 1:
The control device applies dynamics by temporarily varying the EGR ratio during the transition from spark ignition to compression ignition combustion. Instead of maintaining a constant high EGR ratio that would cause preignition, the system dynamically adjusts the EGR ratio to be temporarily reduced during the critical transition period, then returns to the normal high EGR ratio for stable compression ignition combustion
Solution Approach 2:
The control device changes the EGR ratio parameter temporarily during mode switching. By reducing the EGR ratio immediately after switching to compression ignition combustion, the system changes the temperature characteristic of the introduced exhaust gas, thereby controlling cylinder temperature to prevent preignition while ensuring combustion stability
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 reduces combustion noise and ensures stable compression ignition combustion with improved thermal efficiency by maintaining a lower cylinder temperature during mode switching.
Implementation Method 1
an EGR ratio, which is a ratio of an amount of an exhaust gas introduced into the cylinder
Implementation Method 2
a spark plug disposed to face an inside of the cylinder, and configured to ignite an air-fuel mixture in the cylinder
Implementation Method 3
a combustion pattern by compression ignition of an air-fuel mixture in a cylinder
Data Source
AI summary
A controller performs switching between a compression ignition mode in which compression ignition combustion is performed to operate an engine body, and a spark ignition mode in which spark ignition combustion is performed to drive a spark plug to ignite and combust an air-fuel mixture in a cylinder. The controller reduces an EGR ratio to be lower than an EGR ratio set in the compression ignition mode to operate the engine body in a transitional mode in which the compression ignition combustion is performed in switching from the spark ignition mode to the compression ignition mode.