Pre-chamber Spark Ignition Engine Combustion Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Spark ignited engines face challenges in achieving high performance while reducing emissions of nitrogen oxides (NOx), unburnt hydrocarbons (HC), and carbon monoxide (CO), particularly in controlling combustion timing and handling multiple fuels.
Innovation Solution
The method involves controlling the amount and chemical composition of a second fuel introduced to the pre-chamber, spark timing, and in-cylinder charge temperature to achieve a desired combustion duration, utilizing active control of air and fuel introduction into prechambers, and managing exhaust gas recirculation to optimize combustion efficiency and 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 (NOx) emissions are reduced to extremely low values, but combustion timing becomes hard to control
Solution Approach 1:
The combustion chamber is divided into a main chamber and a pre-chamber. The pre-chamber serves as a separate ignition zone where a small amount of fuel is burned first, creating hot gases that then ignite the main fuel-air mixture. This segmentation allows independent control of ignition timing through spark timing in the pre-chamber, solving the combustion control difficulty while maintaining the low NOx benefits of HCCI combustion in the main chamber.
Solution Approach 2:
The pre-chamber acts as an intermediary between the spark ignition system and the main HCCI combustion process. It generates hot combustion products that serve as the ignition source for the diluted fuel-air mixture in the main chamber, enabling controlled ignition timing without directly controlling the main combustion event.
2Ease of operation
If a second fuel with different auto-ignition properties is introduced to improve controllability, then combustion timing control is improved, but the complexity of handling multiple fuels increases
Solution Approach 1:
The ignition control function is extracted from the main combustion chamber and placed in the pre-chamber. A small amount of fuel (second fuel) is introduced separately into the pre-chamber to initiate combustion, while the main fuel-air mixture in the combustion chamber follows HCCI combustion. This separation simplifies fuel handling by isolating the controllable ignition process from the main combustion process.
Solution Approach 2:
Different fuel strategies are applied to different parts of the system: the pre-chamber receives a small amount of controllable fuel for ignition timing control, while the main chamber receives the diluted fuel-air mixture for low NOx HCCI combustion. This local differentiation allows each zone to optimize its function without requiring complex handling of multiple fuels throughout the entire system.
3Ease of operation
If prechambers are provided in large spark ignited engines, then combustion timing can be controlled, but the engine size requirement increases to 150 mm cylinder bore and more
Solution Approach 1:
The pre-chamber geometry and fuel injection timing are made dynamically adjustable to optimize combustion control across different engine operating conditions. The fuel injection system can vary the amount and timing of second fuel introduced to the pre-chamber, allowing effective combustion control without requiring large engine dimensions.
Solution Approach 2:
The system controls combustion timing by changing parameters such as spark timing in the pre-chamber, the amount of second fuel introduced, and the temperature of the in-cylinder charge. These parameter adjustments enable effective combustion control in smaller engines without requiring the large 150 mm cylinder bore traditionally associated with prechamber designs.
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 results in low NOx, HC, and CO emissions by allowing for precise control of combustion duration, enhancing engine efficiency and reducing mechanical stress, while maintaining high performance.
Implementation Method 1
spark timing of the pre-chamber
Implementation Method 2
temperature increase during the compression stroke
Implementation Method 3
pre-heating of the charge through suitable measures (for example pre-heating of the intake air or exhaust gas recirculation, EGR)
Implementation Method 4
ignition of a highly diluted (lean and/or with high rate of exhaust recirculation, EGR) and homogeneous fuel-air-mixture
Data Source
AI summary
A method for operating a spark ignited engine, including forming a combustible mixture by mixing generally homogeneously a first fuel and air and introducing this mixture into the at least one cylinder in an intake stroke, and compressing the combustible mixture with a piston in a compression stroke thereby introducing a part of the combustible mixture into a pre-chamber. During the intake and/or the compression stroke, a second fuel is introduced into the pre-chamber at an introduction-time before start of combustion, and the second fuel is of the same or different chemical composition and/or concentration with respect to the first fuel, and a spark ignites in the prechamber. An amount of second fuel and/or the chemical composition of second fuel introduced to the pre-chamber and/or spark timing of the pre-chamber and/or an in-cylinder charge temperature is chosen such that a desired duration of combustion can be achieved.