Active Prechamber Combustion Control in Spark Ignited Engines
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Solution Overview
Problem
Internal combustion engines face challenges in controlling emissions like nitrogen oxides (NOx), unburnt hydrocarbons (HC), and carbon monoxide (CO) while maintaining efficient combustion, particularly in transitioning between HCCI and spark ignited engine modes.
Innovation Solution
The method involves using an active prechamber in spark ignited engines to control combustion by adjusting the energy content and chemical composition of the prechamber charge, allowing for individual control of air and second fuel introduction, and monitoring combustion characteristics to adjust spark timing and temperature, thereby optimizing combustion efficiency and reducing emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If HCCI combustion concept is used with highly diluted fuel-air mixture, then nitrogen oxides emissions are extremely low, but combustion control becomes very difficult
Solution Approach 1:
The combustion chamber is divided into a prechamber and a main chamber. The prechamber serves as a separate ignition source that can be independently controlled, allowing the main chamber to operate with highly diluted mixtures for low NOx emissions while the prechamber provides reliable ignition control.
Solution Approach 2:
The prechamber acts as an intermediary between the control system and the main combustion chamber. By controlling fuel injection and spark timing in the prechamber, the system can indirectly control the ignition and combustion process in the main chamber, solving the controllability issue while maintaining low emissions.
2Ease of operation
If prechamber is provided in large spark ignited engines, then combustion timing can be controlled, but device complexity increases
Solution Approach 1:
The prechamber serves multiple functions: it acts as an ignition source, a fuel injection location, and a combustion control mechanism. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while achieving good combustion timing control.
Solution Approach 2:
The prechamber combines several functions into a single structural element: ignition initiation, fuel preparation, and combustion control. By merging these functions into one component rather than using separate systems, the overall device complexity is minimized.
3Object-generated harmful factors
If active prechamber is used to control combustion, then emissions and mechanical stress can be reduced, but device complexity and control system complexity increase
Solution Approach 1:
The control system uses feedback from combustion sensors to monitor combustion characteristics and adjust prechamber fuel injection and spark timing in real-time. This feedback mechanism allows the system to reduce emissions and mechanical stress by adapting to actual combustion conditions, while the complexity is managed through electronic control algorithms.
Solution Approach 2:
The prechamber operation is dynamically adjusted based on engine operating conditions. Fuel injection quantity, injection timing, and spark timing in the prechamber are continuously varied to optimize combustion, reduce emissions, and minimize mechanical stress across different operating regimes, making the control system adaptable rather than static.
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 enables precise control of combustion, reducing NOx and HC emissions, lowering mechanical stress, and improving engine operation across varying conditions by adjusting the prechamber charge, resulting in efficient and low-emission combustion.
Implementation Method 1
the ignition of a highly diluted (lean and/or with high rate of exhaust recirculation, EGR) and homogeneous fuel-air-mixture is effected through the temperature increase during the compression stroke
Implementation Method 2
the ignition of a highly diluted (lean and/or with high rate of exhaust recirculation, EGR) and homogeneous fuel-air-mixture is effected through the temperature increase during the compression stroke
Implementation Method 3
in spark ignited engines the combustion timing can be easily controlled by the spark timing
Data Source
AI summary
A method includes forming a combustible mixture by mixing generally homogeneously a first fuel and air and introducing this mixture into a cylinder, compressing the combustible mixture with a piston in a compression stroke, introducing a second fuel into a prechamber at an introduction-time before start of combustion thus creating a prechamber charge, in which the second fuel being of the same or different chemical composition and/or concentration with respect to the first fuel, and spark igniting the prechamber charge. Emission of the cylinder and/or mechanical stress of the cylinder caused by the combustion are monitored. If emissions and/or mechanical stress are above respective predetermined thresholds, individually for the at least one cylinder, the chemical composition and/or the amount of second fuel introduced into the prechamber, and/or temperature of the cylinder charge and/or spark timing, are changed.