Dual-Fuel HCCI Engine Combustion Control
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Solution Overview
Problem
Existing internal combustion engine technologies face challenges in controlling emissions and mechanical stresses, particularly with high NOx and HC emissions, and mechanical stress levels, especially in HCCI and dual-fuel combustion processes, which are difficult to manage effectively across varying environmental conditions.
Innovation Solution
The method involves observing emissions and mechanical stress in individual cylinders by measuring cylinder pressure and adjusting the quantity, timing, and temperature of the second fuel injection, as well as using a variable valve train to control the cylinder charge temperature, thereby adjusting the combustion process to maintain emissions and mechanical stress within predetermined thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If HCCI combustion is used to reduce NOx emissions through highly diluted fuel-air mixture, then nitrogen oxide emissions are extremely low, but control of ignition timing becomes very demanding and combustion event occurs extremely quickly making regulation difficult
Solution Approach 1:
A second fuel with different self-ignition properties (higher tendency to self-ignite) is introduced as an intermediary substance to control the combustion process. This second fuel acts as a mediator that enables precise ignition timing control while maintaining the low NOx emissions benefits of HCCI combustion with highly diluted fuel-air mixtures
2Ease of operation
If exhaust gas recirculation rate is varied to control ignition point, then ignition timing can be adjusted, but the reaction is delayed and not quick enough for precise control
Solution Approach 1:
Instead of varying the exhaust gas recirculation rate which has delayed response, the invention changes the parameter of fuel composition by injecting a second fuel with different self-ignition properties. This parameter change enables quick and precise control of ignition timing without the delayed response associated with EGR rate adjustments
3Ease of operation
If dual-fuel combustion is used to improve control of combustion process, then ignition timing control is enhanced, but HC and CO emissions become high
Solution Approach 1:
The second fuel is injected locally at specific positions and timings within the combustion chamber to achieve precise control of ignition timing and combustion rate. This localized injection approach enables better combustion control while minimizing the formation of HC and CO emissions by ensuring complete combustion in targeted zones
4Strength
If mechanical stress is reduced by lowering compression ratio or charge temperature, then engine durability improves, but self-ignition capability and combustion efficiency are compromised
Solution Approach 1:
The invention changes the chemical composition parameter by introducing a second fuel with higher self-ignition tendency. This parameter change enables the engine to maintain reliable self-ignition capability and combustion efficiency even at lower compression ratios and charge temperatures that reduce mechanical stress and improve engine durability
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 allows for precise control of emissions and mechanical stress, improving engine operation by reducing NOx and HC emissions and mechanical stress through targeted adjustments in fuel injection and cylinder charge temperature, enhancing engine performance across different conditions.
Implementation Method 1
a highly diluted (i.e. lean mixture and/or with a high exhaust gas recirculation rate) and homogeneous fuel-air mixture is ignited by the temperature rise during the compression stroke near top dead center
Implementation Method 2
The self-ignition of the fuel-air mixture in the combustion chamber is achieved through a combination of different measures, such as a high geometric compression ratio ε and preheating of the charge through suitable measures
Implementation Method 3
preheating of the charge through suitable measures (e.g. preheating of the charge air or exhaust gas recirculation, EGR)
Data Source
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AI summary
A method for operating a compression-ignition internal combustion engine with at least one cylinder and a piston movable in the at least one cylinder, comprising the steps of: - forming an ignitable mixture by largely homogeneously mixing a first fuel and air and introducing this mixture into the at least one cylinder; - compressing the ignitable mixture with the piston in a compression stroke; - during the compression stroke, but before the start of combustion, injecting a second fuel into the ignitable mixture, thereby creating a cylinder charge, the second fuel having a higher tendency to self-ignite than the first fuel; - continuing the compression stroke until combustion starts at those points in the at least one cylinder where the concentration of the second fuel and/or the temperature of the mixture is highest.wherein the combustion-induced emission of the at least one cylinder and/or the mechanical stress of the at least one cylinder are monitored and if the emissions and/or the mechanical stress exceed respective predetermined thresholds, the quantity and/or the timing of the injected second fuel and/or the temperature of the cylinder charge are individually varied for the at least one cylinder in such a way that the emissions and/or the mechanical stress fall below their respective predetermined thresholds.