Stratified Charge Ignition for Low Load Gaseous Engines
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Solution Overview
Problem
Gaseous-fueled internal combustion engines face difficulties in igniting a premixed charge at low load or low temperature conditions due to reduced kinetic energy and lower likelihood of particle collisions, leading to unstable ignition and poor combustion.
Innovation Solution
An ignition apparatus with a dilutant injector and an enrichment injector, controlled by an electronic controller, introduces a diluting agent and gaseous fuel to form stratified charges around the ignition device, adjusting the local air-fuel equivalence ratio to improve ignitability, particularly at low engine loads and speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spark plug or conventional ignition device is used in a stoichiometric gaseous fueled engine, then the engine can operate with a stoichiometric air-fuel ratio, but unstable ignition and poor combustion occur at low load and low temperature conditions
Solution Approach 1:
The patent applies local quality by creating a stratified charge with different air-fuel equivalence ratios in different regions of the combustion chamber. Specifically, a rich stratified charge (higher fuel concentration) is formed around the ignition device to ensure reliable ignition, while the bulk mixture maintains stoichiometric composition for efficient combustion. This spatial variation in mixture composition resolves the contradiction between maintaining stoichiometric operation and ensuring ignitability at low load/temperature conditions.
Solution Approach 2:
The patent changes the local air-fuel equivalence ratio parameter around the ignition device to improve ignitability. By enriching the mixture locally (increasing the fuel-to-air ratio) in the region surrounding the ignition device, the activation energy requirement is reduced and ignition becomes more reliable at low load and temperature conditions, while the overall stoichiometric ratio is maintained for combustion efficiency.
2Use of energy by moving object
If pilot fuel is directly injected and compression ignited in a stoichiometric engine, then ignition energy is provided, but the local air-fuel equivalence ratio becomes too rich reducing the likelihood of particle reaction
Solution Approach 1:
The patent uses local quality to create a controlled rich stratified charge around the ignition device rather than uniform rich mixing. This localized enrichment provides sufficient ignition energy while limiting the extent of rich mixing to areas where it is most beneficial for ignition, thereby maintaining adequate oxidant availability for subsequent combustion propagation.
Solution Approach 2:
The patent segments the charge into different regions with different air-fuel ratios: a rich stratified charge region around the ignition device for reliable ignition, and a stoichiometric bulk region for efficient combustion. This spatial segmentation allows the system to benefit from both rich and stoichiometric mixture characteristics without the drawbacks of either extreme throughout the entire combustion chamber.
3Power
If throttling is applied to reduce engine load, then power output is reduced, but the number of moles of oxidant decreases further reducing ignitability
Solution Approach 1:
The patent compensates for the reduced oxidant availability caused by throttling by creating a locally enriched charge around the ignition device. This local enrichment ensures that sufficient fuel is present to maintain ignitability even when the overall number of moles of oxidant is reduced by throttling, thereby maintaining reliable ignition across different load conditions.
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 solution enhances the ignitability of gaseous fuel in stoichiometric gaseous-fueled engines by optimizing the air-fuel mixture around the ignition device, ensuring reliable ignition and improved combustion efficiency even at low load and temperature conditions.
Implementation Method 1
a dilutant injector for introducing a diluting agent that forms a stratified charge around the ignition device
Implementation Method 2
an enrichment injector for introducing gaseous fuel that forms a stratified charge around the ignition device
Implementation Method 3
ignition device associated with a combustion chamber of the internal combustion engine
Data Source
AI summary
Premixed engines have ignition issues when engine speed and load are below a predetermined range. An ignition apparatus for igniting a premixed charge in a gaseous-fueled internal combustion engine comprises an ignition device associated with a combustion chamber of the internal combustion engine. There is at least one of a dilutant injector for introducing a diluting agent that forms a stratified charge around the ignition device and an enrichment injector for introducing gaseous fuel that forms a stratified charge around the ignition device. An electronic controller is operatively connected with the ignition device and the at least one of the dilutant injector and the enrichment injector and programed to at least one of actuate the dilutant injector to introduce the diluting agent when the ignition device decreases a local air-fuel equivalence ratio around the ignition device below a predetermined threshold; and actuate the enrichment injector to introduce the gaseous fuel to decrease the local air-fuel equivalence ratio when engine load and engine speed are below a predetermined threshold engine load and speed range and when the ignition device does not affect the local air-fuel equivalence around the ignition device.