Engine Re-combustion Cycle for Exhaust Temperature
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Solution Overview
Problem
Existing methods for increasing exhaust gas temperature in internal combustion engines, such as cylinder deactivation and cam phasing, often result in unwanted noise, vibration, and harshness (NVH) issues, particularly at low engine speeds, and require additional hardware like direct air injection systems, increasing engine complexity.
Innovation Solution
The method involves rebreathing or recompressing previously combusted air-fuel mixtures in the cylinders by alternately cycling between standard four-stroke cycles and rebreathing or recompression cycles, where the intake or exhaust valves are manipulated to expel and re-ingest the combusted gases, or maintain them for re-combustion, without the need for additional hardware, thereby reducing air flow and increasing exhaust gas temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cylinder deactivation is used to increase exhaust gas temperature, then catalytic conversion efficiency is improved, but noise, vibration, and harshness (NVH) increase
Solution Approach 1:
The patent applies periodic action by alternating between standard four-stroke cycles and rebreathing cycles. During rebreathing cycles, the intake valve remains closed during the intake stroke to trap and re-combust exhaust gases, while during standard cycles, normal valve operation occurs. This periodic alternation allows the exhaust system to accumulate sufficient thermal energy for catalytic conversion while avoiding continuous cylinder deactivation that would cause persistent NVH issues.
Solution Approach 2:
The patent changes the operational parameters of the intake valve by controlling it to remain closed during intake strokes in rebreathing cycles, rather than following the standard open-closed pattern. This parameter change enables exhaust gas trapping and re-combustion, increasing exhaust temperature without the NVH penalties of continuous deactivation.
2Temperature
If cam phasing is used to maintain exhaust valve open during intake stroke, then exhaust gas temperature is increased, but additional hardware complexity is required
Solution Approach 1:
The patent makes the existing intake valve serve a dual function: during standard cycles, it performs normal intake air admission, and during rebreathing cycles, it remains closed to trap exhaust gases. This multi-functionality eliminates the need for separate exhaust valve phasing mechanisms or dedicated air injection systems, reducing hardware complexity while achieving the same thermal management goal.
Solution Approach 2:
The patent uses the engine's own exhaust gases as the heating medium for catalytic conversion, rather than requiring external air injection systems. The rebreathed exhaust gases are re-combusted to generate the necessary heat, making the system self-sufficient and eliminating additional hardware components.
3Quantity of substance
If exhaust valve is kept open during intake stroke, then exhaust gas recirculation is improved, but low vacuum is introduced at low engine speed
Solution Approach 1:
The patent applies periodic action by alternating between standard four-stroke cycles and rebreathing cycles. During rebreathing cycles, the intake valve remains closed during the intake stroke to trap and re-combust exhaust gases, while during standard cycles, normal valve operation occurs. This periodic alternation allows the exhaust system to accumulate sufficient thermal energy for catalytic conversion while avoiding continuous cylinder deactivation that would cause persistent NVH issues.
Solution Approach 2:
The patent changes the operational parameters of the intake valve by controlling it to remain closed during intake strokes in rebreathing cycles, rather than following the standard open-closed pattern. This parameter change enables exhaust gas trapping and re-combustion, increasing exhaust temperature without the NVH penalties of continuous deactivation.
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 increases exhaust gas temperature for more efficient catalytic conversion, reduces NVH issues, and simplifies engine design by eliminating the need for complex hardware, while maintaining catalyst operation above light-off temperature and improving emissions quality.
Implementation Method 1
compress the charge stored therein through piston motion
Implementation Method 2
combustion in the engine
Data Source
AI summary
Methods and systems are provided for re-combustion of exhaust in a cylinder of a multi-cylinder engine in order to increase the temperature of the exhaust for enhancing catalytic conversion within the multi-cylinder engine. In one example, a method may include expelling combusted gases from the cylinder into an intake manifold via an intake valve during an exhaust stroke, in order to rebreathe in the combusted gases from the intake manifold via the intake valve in a subsequent intake stroke.