EGR Composition Control for Engine Ignition Stability
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Solution Overview
Problem
Conventional spark ignition systems in internal combustion engines with exhaust gas recirculation (EGR) face combustion instability due to limited ignition energy, which affects ignitability, knock tolerance, ignition timing, and particle emissions.
Innovation Solution
Active control of EGR composition, particularly the amount of hydrogen (H2) and carbon monoxide (CO), by adjusting the air-fuel ratio, using dedicated EGR cylinders, and injecting fuel or H2 into the EGR stream to enhance ignitability and knock tolerance, and reduce particle emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the energy or power of the ignition system is increased to address combustion instability, then combustion stability is improved, but the device complexity and cost increase
Solution Approach 1:
The patent changes the chemical composition parameters of the EGR stream by controlling the air-fuel ratio in the EGR cylinder to produce higher concentrations of hydrogen and carbon monoxide. This chemical parameter change improves ignitability and combustion stability without requiring increased ignition system energy or complexity
Solution Approach 2:
The patent introduces an intermediary substance (hydrogen-rich EGR gas) that mediates between the ignition system and the main combustion process. The hydrogen in the EGR stream acts as a catalyst or promoter that enhances ignition and combustion stability without requiring the ignition system itself to be more powerful
2Device complexity
If conventional spark ignition systems are used with limited energy, then device complexity is reduced, but combustion stability deteriorates
Solution Approach 1:
The patent modifies the EGR composition parameters (increasing hydrogen and CO content through controlled air-fuel ratios) to compensate for the limited ignition energy, thereby maintaining combustion stability without increasing ignition system complexity
Solution Approach 2:
The patent converts what would normally be waste exhaust gases into a beneficial resource by controlling their composition to富含 hydrogen and carbon monoxide, which then serve to enhance ignitability and support stable combustion in the main cylinders
3Reliability
If EGR composition is actively controlled to improve ignitability, then combustion stability is improved, but device complexity increases
Solution Approach 1:
The patent segments the engine into dedicated EGR cylinders and main power cylinders, allowing independent control of EGR composition. This segmentation enables simplified control by dedicating specific cylinders to producing hydrogen-rich exhaust without complicating the overall control system
Solution Approach 2:
The EGR system serves itself by using the exhaust from dedicated EGR cylinders (which are naturally hydrogen-rich due to controlled air-fuel ratios) to directly enhance combustion in the main cylinders, creating a self-sustaining system that reduces the need for external control complexity
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 improves combustion stability, reduces the required ignition energy, increases knock tolerance, and decreases particle emissions by optimizing the EGR composition to match the engine's ignition system capabilities and operating conditions.
Implementation Method 1
the combustion cylinders are provided with a 'charge' consisting of fuel, air and recirculated exhaust. This charge is ignited within the cylinders by the igniter of the engine's ignition system
Implementation Method 2
The recirculated exhaust, added to the fuel and oxygen, increases the specific heat capacity of the cylinder contents, which lowers the adiabatic flame temperature
Implementation Method 3
the amount of H2 that can be produced in the EGR stream as a result of rich combustion
Data Source
AI summary
A method for improving ignition of a spark ignited internal combustion engine by controlling the composition of recirculated exhaust gas. It is assumed that the engine has a spark ignition system and an exhaust gas recirculation (EGR) loop such that at least one of the combustion cylinders is an EGR cylinder that generates an EGR stream carried by the EGR loop. Thus, the combustion charge is a mixture of air, fuel and recirculated exhaust. A first step is receiving combustibility data representing the current ignitability of the charge. It is then determined whether the energy of the ignition system is sufficient to ignite the charge. If not, the amount of hydrogen in the EGR stream is increased, which increases the ignitability of the charge.