Re-entrant Piston Bowl Toroidal Recirculation
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Solution Overview
Problem
Diesel engines face challenges in controlling NOx and soot emissions, as advancing injection timing to improve fuel economy often increases soot production, and retarding timing to reduce NOx increases fuel consumption.
Innovation Solution
A combustion system with a piston bowl having a peripheral exit angle greater than 90°, specifically 105°-115°, where fuel impinges on a midland portion of the bowl floor, promoting tangential impingement and toroidal recirculation to reduce NOx formation and consume soot, while allowing advanced injection timing for better fuel economy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If injection timing is advanced to improve fuel economy, then fuel consumption decreases, but soot production increases
Solution Approach 1:
The combustion chamber is segmented into distinct zones: a peripheral region for initial fuel impingement and combustion, and a central region for recirculation and soot consumption. The piston bowl geometry creates separate flow paths that allow different combustion stages to occur in different spatial locations, enabling fuel economy improvement without excessive soot formation.
Solution Approach 2:
The invention introduces a vertical dimension to the combustion process by creating a toroidal recirculation flow that moves fuel and combustion products from the peripheral region upward and inward toward the central region. This three-dimensional flow structure allows soot to be transported from high-temperature combustion zones to lower-temperature recirculation zones for consumption, decoupling the relationship between injection timing advancement and soot production.
2Object-generated harmful factors
If injection timing is retarded to reduce NOx emissions, then NOx formation decreases, but fuel consumption increases
Solution Approach 1:
Different regions of the combustion chamber are given different functional qualities: the peripheral region is optimized for high-temperature combustion with controlled NOx formation, while the central recirculation region is optimized for soot consumption and mixing. This local differentiation allows the system to achieve low NOx emissions without sacrificing fuel economy, as each zone performs its specialized function efficiently.
3Productivity
If fuel sprays impact the peripheral region of the piston bowl, then combustion occurs, but momentum is lost and recirculation is limited
Solution Approach 1:
The piston bowl is designed with a curved, toroidal geometry that guides the fuel spray and combustion products along a circular recirculation path. The curved surfaces redirect flow momentum rather than allowing it to dissipate, maintaining high velocities throughout the recirculation loop. This curvature-based design converts what would be momentum loss into sustained recirculation flow that enhances mixing and combustion efficiency.
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 reduces fuel consumption and maintains constant or reduced particulate emissions without increasing NOx, achieving superior fuel economy and controlled emissions.
Implementation Method 1
fuel and primary products of combustion become entrained in a toroidal flow recirculating from the midland portion of the floor to an outward region of the piston bowl and then inward toward a middle region of the combustion chamber
Implementation Method 2
compression ignition engine includes a cylinder and a cylinder head having a fuel injector with a nozzle mounted so as to spray at a predetermined angle
Data Source
AI summary
A diesel combustion system with a re-entrant piston bowl utilizes momentum interaction with the bowl at multiple locations to cause recirculation of the partially burned fuel and combustion products in a toroidal flow so as to consume soot formed during an earlier portion of the combustion process, while reducing the formation of NOx and improving fuel efficiency of the engine.