Engine Valve Overlap Control for Afterburn Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing engine control systems fail to effectively manage the overlapping period of intake and exhaust valves during fuel injection, leading to excessive temperature increases in the exhaust system components due to afterburn, which can damage catalysts and other components.
Innovation Solution
A control apparatus with a processor and variable valve timing mechanism that adjusts the overlapping period based on estimated exhaust gas temperature increases, determining when protection is required and shortening the overlap to prevent afterburn, thereby reducing the blow-through flow rate and minimizing component temperature increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the overlapping period is extended to improve exhaust gas cooling, then the catalyst temperature control is improved, but afterburn occurs in the exhaust system causing component temperature to excessively increase
Solution Approach 1:
The control apparatus determines whether protection for exhaust system components is required based on estimated exhaust gas temperature increase before fuel amount increase control is fully executed. By shortening the overlapping period in advance when protection is required, the system prevents afterburn before it occurs, rather than reacting after temperature problems arise.
Solution Approach 2:
The overlapping period is dynamically adjusted based on real-time estimation of exhaust gas temperature increase. The valve controlling module varies the overlapping period length according to whether protection is required, transitioning from a fixed timing approach to a dynamic, condition-based approach that optimizes both catalyst temperature control and afterburn prevention.
2Temperature
If fuel injection amount is increased to cool exhaust gas, then exhaust gas temperature decreases, but unburned fuel reacts with fresh air in exhaust system causing afterburn
Solution Approach 1:
The overlapping period acts as an intermediary control parameter between fuel injection amount and afterburn prevention. By adjusting the overlapping period, the system mediates the relationship between increased fuel injection (which cools exhaust gas) and the risk of afterburn (from unburned fuel reacting with fresh air), finding an optimal balance that achieves cooling while preventing harmful reactions.
Solution Approach 2:
The system uses feedback from exhaust gas temperature estimation to control the overlapping period. The valve controlling module continuously monitors estimated exhaust gas temperature increase and adjusts the overlapping period accordingly, creating a closed-loop control system that responds to actual thermal conditions to prevent afterburn.
3Object-affected harmful factors
If fresh air flow rate through exhaust system is increased to suppress afterburn, then afterburn is reduced, but exhaust gas cooling effect is diminished
Solution Approach 1:
The system changes the timing parameters (overlapping period duration) rather than directly controlling fresh air flow rate. By adjusting when the intake and exhaust valves overlap during the intake stroke, the system indirectly controls the amount of fresh air entering the exhaust system, achieving afterburn suppression while maintaining exhaust gas cooling through parameter optimization rather than direct flow control.
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 solution effectively suppresses afterburn and protects exhaust system components by accurately determining the need for temperature protection and adjusting the overlapping period before fuel injection, ensuring the system operates within safe temperature limits.
Implementation Method 1
since unburned fuel vaporizes inside the cylinder, latent heat of the vaporization cools the inside of the cylinder, and a temperature of the exhaust gas discharged from the cylinder to an exhaust system decreases
Data Source
AI summary
A control apparatus of an engine including intake and exhaust valves and a variable valve timing mechanism for varying open and close timings is provided. The apparatus includes a processor configured to execute an increasing amount controlling module for performing a fuel amount increase control in which a fuel injection amount is increased to decrease an exhaust gas temperature, and a valve controlling module for controlling, via the variable valve timing mechanism, an overlapping period in which the intake and exhaust valves are both opened on intake stroke. When the increasing amount controlling module performs the increase control, based on an increase of a temperature of the exhaust gas in the increase control, the valve controlling module determines whether a protection for an exhaust system component is required, and if the protection is determined to be required, the valve controlling module shortens the overlapping period.