Antebowl Piston Geometry for Transient Smoke Reduction
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Solution Overview
Problem
Conventional piston designs for compression ignition engines struggle with smoke production during transient load swings, particularly in large bore engines used for electric power generation, where existing designs are inadequate for managing emissions and efficiency in various applications.
Innovation Solution
The piston features a combustion bowl with a rounded inner rim surface defining an antebowl, which provides additional volume for combustion, and an operating strategy that injects fuel plumes into both the combustion bowl and antebowl to ensure complete fuel burn, especially during transient load changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional piston designs are used in large bore compression ignition engines, then the engine can operate across various load conditions, but smoke production increases during transient load swings
Solution Approach 1:
The combustion chamber is segmented into two distinct regions: a combustion bowl for primary combustion and an antebowl for capturing and combusting unburned fuel. This segmentation allows different zones to serve different functions, with the antebowl specifically addressing smoke reduction during transient conditions while the combustion bowl maintains overall combustion efficiency across all operating conditions.
Solution Approach 2:
The antebowl acts as an intermediary chamber between the combustion bowl and the cylinder head. It captures unburned fuel that would otherwise escape into the exhaust, providing a transition zone where this fuel can be completely combusted. This intermediary structure mediates between the high-power combustion process and the emission control requirements.
2Productivity
If the combustion bowl diameter is increased to improve combustion efficiency, then fuel burn is enhanced, but smoke production during transient conditions worsens
Solution Approach 1:
By segmenting the combustion chamber into a combustion bowl and an antebowl, the system can maintain a large combustion bowl diameter for efficient fuel burn while using the antebowl to capture and completely combust any unburned fuel, thus addressing smoke production without sacrificing combustion efficiency.
Solution Approach 2:
The invention changes the geometric parameters of the combustion chamber by adding the antebowl volume (at least 1% of total combustion chamber volume) with specific curvature requirements (radius of curvature between 0.04-0.06 times the combustion bowl diameter). These parameter changes create optimal flow patterns that reduce smoke during transient conditions while maintaining efficient combustion.
3Power
If fuel injection quantity is increased to meet higher power demands, then engine output is improved, but incomplete combustion and smoke increase during transient load changes
Solution Approach 1:
The antebowl serves as an intermediary combustion chamber that receives and completely burns unburned fuel from high-quantity injections during transient load changes. This allows the engine to deliver high power output while the antebowl ensures complete combustion, preventing smoke formation even when large amounts of fuel are injected.
Solution Approach 2:
The antebowl is positioned to intercept unburned fuel before it can escape into the exhaust system. By providing this preliminary combustion chamber, the system ensures that fuel is completely burned in advance, preventing smoke formation during transient conditions when fuel injection quantities change rapidly.
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 design effectively reduces smoke production by ensuring complete combustion of fuel, even during transient load conditions, thereby improving emissions and efficiency in large bore engines.
Implementation Method 1
moving a piston within a cylinder of the internal combustion engine toward a top dead center position, such that a pressure within the cylinder is increased to an autoignition threshold
Implementation Method 2
injecting spray plumes of a first charge of a liquid fuel into the cylinder in the first engine cycle, such that the spray plumes of the first charge enter a combustion bowl formed in the piston
Implementation Method 3
combusting the first charge of the liquid fuel at least predominantly within the combustion bowl
Data Source
AI summary
A direct-injected compression ignition internal combustion engine includes an engine housing having a cylinder and a piston movable within the cylinder and including a piston end face forming a combustion bowl. The piston end face has an annular piston rim with a rounded inner rim surface that extends radially inward and axially downward from a planar outer rim surface to a combustion bowl edge. An antebowl is defined by the rounded inner rim surface and has an antebowl volume that is about 0.8% or greater of a total volume of the combustion bowl and the antebowl together. A configuration and dimensional attributes of the antebowl is associated with reduced smoke production during operation, particularly for low to mid-load transients.