Rectangular Ducted Combustion Chamber for Direct Injection Engines
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Solution Overview
Problem
Direct injection engines face challenges in achieving uniform fuel-air mixing and reducing emissions, particularly NOx and soot, due to the entrainment of combustion products and rich fuel mixtures at the flame lift-off length, which are not adequately addressed by existing designs that require substantial machining operations.
Innovation Solution
The introduction of ducts with a generally rectangular or U-shaped cross-section within the combustion chamber, formed by protruding walls from the piston head and cylinder head, which channel fuel jets and inhibit the entrainment of combustion products, promoting faster and more uniform premixing of fuel and air.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional combustion chamber designs are used, then the engine structure is simple, but fuel-air mixing is non-uniform and emissions are high
Solution Approach 1:
The combustion chamber is segmented into multiple regions using ducts that divide the space into upstream and downstream zones. This segmentation allows different mixture compositions to be maintained in different regions, with the ducts preventing harmful combustion products from the downstream region from contaminating the upstream fuel injection zone, thereby improving mixing uniformity and reducing emissions.
Solution Approach 2:
Different regions of the combustion chamber are given different functional qualities. The upstream region is optimized for fuel injection and initial mixing with relatively fresh charge, while the downstream region handles combustion and recirculation. The ducts create local quality differences by maintaining distinct flow characteristics and composition in each zone, leading to reduced emissions.
2Object-generated harmful factors
If ducts are added to channel fuel jets, then emissions are reduced, but device complexity increases
Solution Approach 1:
The ducts are integrated into the existing combustion chamber structure rather than being added as separate components. The ducts merge with the piston crown and cylinder head surfaces to form a unified combustion chamber design, channeling fuel jets while maintaining structural coherence. This merging approach reduces the perceived complexity by combining emission control functionality with the existing chamber geometry.
3Stability of the object's composition
If combustion products are allowed to recirculate freely, then mixing is enhanced, but equivalence ratio becomes too rich at lift-off length
Solution Approach 1:
The ducts extract or remove harmful combustion products from the upstream fuel injection region by providing a physical barrier that prevents recirculated products from contaminating the fresh charge zone. This extraction maintains a fuel-lean equivalence ratio at the lift-off length where soot formation would otherwise occur, while still allowing controlled mixing in the downstream region.
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 configuration enhances combustion efficiency, reduces emissions by maintaining a more fuel-lean equivalence ratio at the lift-off length, leading to lower soot and NOx emissions, and improves engine efficiency.
Implementation Method 1
local velocity gradients around the fuel jet create a more-uniform mixture of fuel from the fuel jet with the charge gas
Implementation Method 2
Entrainment of recirculated combustion products from a downstream region of a fuel jet to an upstream region of a fuel jet is minimized by containing a portion of the upstream region of each fuel jet within its corresponding duct
Data Source
AI summary
An internal combustion engine includes an engine block having a cylinder bore and a cylinder head having a flame deck surface disposed at one end of the cylinder bore. A piston connected to a rotatable crankshaft and configured to reciprocate within the cylinder bore has a piston crown portion facing the flame deck surface such that a combustion chamber is defined within the cylinder bore and between the piston crown and the flame deck surface. A fuel injector having a nozzle tip disposed in fluid communication with the combustion chamber has at least one nozzle opening configured to inject a fuel jet into the combustion chamber along a fuel jet centerline. At least one duct defined in the combustion chamber between the piston crown and the flame deck surface has a generally rectangular cross section and extends in a radial direction relative to the cylinder bore substantially along the fuel jet centerline.